NZ533069A - In-pipe wastewater treatment system - Google Patents

Abstract

An aerobic waste-water treatment apparatus includes an elongate trough or pipe 20 which holds a body of porous and water permeable treatment material 23 such as an open cell foam with capillary action which can support vigorous colonies of microbes fitted on the bottom of the trough and extending between the walls but having an air gap 24 at the top between the roof 25 of the trough and the top of the material. The trough is at least three times as long as it is wide. During treatment of water contaminated with carbonaceous BOD (biochemical oxygen demand), the water moves from the inlet, seeping through the foam and having an average standing level 27 to the outlet, and is exposed to the microbes growing in the foam and using oxygen from the space above the foam to perform aerobic breakdown reactions of the BOD in the water residing in the pores of the treatment material.

Description

*10056902088* 1 53 50 6 9 IN-P1PE WASTEWATER TREATMENT SYSTEM [0011 In a first aspect, this Invention relates to typically aerobic, microbial treatment of mainly domestic sewage and other wastewaters, and to the renovation of polluted water in general.

THE FIRST ASPECT OF THE INVENTION, IN RELATION TO THE PRIOR ART

[002] One common arrangement for treating wastewater has the following element or stations: (a) an anaerobic digester station; (b) an aeration station; and (c) an Infiltration station, In that case, Ihe first aspect of the invention may preferably be utilised in the aeration station.

[003] Water entering an aeration station may be water that has Just emerged from a septic tank. Here, solid materials in ttie wastewater can settle out, and reductive breakdown reactions can take place, which break down much of the organic content of the wastewater, both solid and dissolved, Dissolved ammonium in the water is largely not affected by passage through the septic tank. Water emerging from a well-engineered septic tank has only a small undissolved (i.e solid] organic content. One of the functions of the aeration station Is to remove the remaining dissolved organic content,

[004] In tie aeration station, the oxidation reactions can take place, In passing through a well-engineered aeration station, 1hs carbonaceous-BOD content Is oxidised to Inconsequential liquids and gases. Also, ammonium In the water can be oxidised In an aeration station,

[005] The infitlration station mainly serves the mechanical purpose of infiltrating the water Into the ground, rather 1han serving to promote treatment reactions. An Infiltration station is well engineered if water Infiltrates into the ground without disruption to 1he ground and without clogging, etc, over a long seivlce life.

[006] • In traditional seplic-tank wastewater treatment systems, the aeration station and the Infiltration station have been combined In a single structure, comprising a tile-bed soakaway. Ihe first aspect of the present Invention relates to treatment systems in which the aeration station is a separate structure from the Infiltration station, and follows generally from 1he technologies disclosed in Ihe following U.S.A. patents: 5,707,513 5,762,784 5,980,739 5,997,747 6,063,268 6,156,094.

[007] In its first aspect the present invention Is aimed mainly at providing a new form of treatment station in which the water is presented most efficaciously to a body of treatment materia). One aim Is to improve the efficiency of utilisation of premium space, The invention, in its first aspect, may be utilised generally for removing contaminants from water, but the advantages of the Invention are very marked In the case of the aerobic treatment station, to vigorously promote the carbonaceous-BOD oxidation reactions, and this first aspect of the invention is described mainly as it relates to an aeration station, It Is intended that an aeration station, In this new farm, should require no more input of Ingredients or energy, and no more attention or service, than Is required In traditional conventional septic tank systems, (It should be understood, in this context, that conventional septic iTeatment systems sometimes include electric pumps and other active components, and septic systems commonly need to be serviced every year or Iwo.) 2

[008] In ttie first preferred aspect of the Invention, the aeration station has a long, narrow configuration. So much so, that (t preferably becomes convenient to fit the aeration station Into a pipe. In a preferred arrangement, which will be described, the aeration station Is located In a pipe that transfers water from the effluent port of the septic tank to the ground-tnfiltraHon station. Unlike conventional tile-beds, the aeration stations as described herein are generally not suitable for serving double duty as ground-Infiltration stations. It Is mainly fn the smaller size of aeration station, that the long/narrow configuration can provide large gains in efficiency, for example In single-dwelling domestic installations, or an Installation for handling, say, six dwellings, or a small institutional Installation, such as a restaurant or golf course. The advantages of the Invention are not so marked In the case of e.g municipal-sized treatment facilities.

[009] Hitherto, it has riot been practical to configure a water treatment station to fit In a pipe, It has not previously been proposed how the constraints associated with flow through a pipe might be overcome. Trealment reactions require vigorous colonies of microbes, and It may be considered Impractical to house the colonies of microbes actually in ihe pipe, It has been considered that a pipe Is for moving wcrier, not for treating water.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF FIRST ASPECT

[0010] By way of further explanation of the first aspect of the Invention, exemplary embodiments of the Invention will now be described with reference to the accompanying drawings, in which: Fig 1 is a diagrammatic cross-sectioned side view of a system for treating wastewater that embodies the Invention.

Fig 2 is a pictorial view of a body of foam material, which Is a component of 1he system of Fig 1.

Fig 3 is a close-up of a portion of Fig 1.

Fig A is a plan view of the treatment system of Fig 1.

Fig 5a Is a diagrammatic cross-sectioned view of a pipe containing a body of treatment material.

Fig 5b is the same view as Fig 5a, but shows a different condition, Figs 6a,6b correspond to Figs 5a,5b, but show a different trealment material.

Fig 7 is an end view of another system for treating wastewater that embodies 1he invention, Fig 8 is a cross-sectioned side-view of the system of Fig 7.

Fig 9 Is an end view, like Fig 7 of another system that embodies the invention.

Fig 9a Is a cross-secfloned side-view of the system of Fig 9.

Fig 10 Is a pictorial view of another system 1hat embodies the invenlion.

[0011] The systems shown in the accompanying drawings and described below are examples which embody the Invention. It should be noted that the scope of the invention Is defined by 1he accompanying claims, and not necessarily by specific features of exemplary embodiments.

[0012] In Fig 1, the pipe 20 has a length of about fifteen metres, and a diameter (internally) of about twenty-five centimetres. The pipe 20 is made of a plastic [polyethylene, PVC, etc) material that Is Inert as far as wastewater and 1he pollutants commonly found in wastewater are concerned.

[0013] Inside the pipe 20 is a body 23 of plastic foam material. Again, the foam Is of a plastic material that is inert as far as wastewater and the pollutants found in wastewater are concerned. (Types of treatment material olher than foam may be considered for use in the invention, as will be described later.) 3 [0014} Ihe bod/ 23 of foam is configured as shown in Fig 2, and Is dimensioned so as to il the pipe 20, except that an air passage 24 is created belween the top of the foam and the roof 25 of the pipe 20. The body 23 of foam Is tight against the floor 26 of the pipe. The air-passage 24 is open to the atmosphere. The air-passage 24 Is of large enough cross-section to ensure that air can pass easily along and through the whole length of the pipe 20. in the 25-cm diameter pipe, as shown, the air-passage 24 should have a cross-sectional area of about forty square cm.

[0015] The air-passage 24 also serves another purpose. If there were to be a sudden excess influx of wasiewafer, the overflow of water can be received Into the air-passage, and can be directed further down the pipe, until it can infiltrate down into the foam. Of course, the treatment system must be adequate for the task for which it Is designed, and the system would be Inadequate if an overflow of Incoming water could reach, and be discharged from, the far end of the pipe without soaking down into the foam,

[0016] It will be understood also that If the portion of the foam material near the inlet should become plugged (e.g with slime or other solid treatment products), whereby water is Inhibited from soaking Into that portion of the foam material, again the incoming water can be received In the air-passage, and can thereby be directed , further down the pipe.

[0017] The air-passage 24 must be large enough to perform these functions. If the excess overflow water flowing down the air-passage is to have the opportunity to soak down properly Into 1he foam, the surface area of foam presented to the water must be adequate; that Is to say, if the air-passage were too small, the overflow water might be conducted right through the air-passage, and be discharged, untreated, from the far end of the pipe. Fa this reason, the designer should see that the cross-sectional area of the air-passage 24 Is at least ten square cm. Also, if the cross-sectional area of the air-passage were smaller than ten sq cm, air access to the foam might be Inadequate, the main purpose of the pipe 20 Is to contain treatment material, rather than to contain air passage; so, given that the 25-cm pipe 20 has a total cross-sectional area of Just under 500 sq cm, the air-passage 24 should not be more than about 100 sq cm, as that would Just waste space Inside the pipe. ■

[0018] The foam Is of the Interconnected or open-cell type, whereby water can pass through the cells of the foam with a measurable velocity, The cells are small enough to provide a substantial capillary effect. The capillary effect should be strong enough that, after the pipe 20 has been filled with water, such lhat 1he body 23 of foam material Is saturated, and then after the water has drained freely out of the pipe, some water is retained In the body of foam material. The foam material should be such that after a period of, say, one hour after dosing has ended, water Is retained to a depth 27 (Fig 1) of belween five cm and fifteen cm. If more water were to drain away than this, 1he water would not be retained In 1he pipe for a long enough residence time. If more water than this were retained, that would mean the foam might not be sufficiently permeable, whereby Incoming water might tend to flow straight through the pipe, l.e frirough the air-passage 24, rather than to Infiltrate down Into the body 23 of foam material. l

[0019] To have the right degree of absorbency and capillarity for use in the Invention, the foam preferably should have a porosity of between about ninety percent and ninely-six percent.

[0020] After the system has been In use for long enough to reach steady operating conditions, the freestanding depth 27 of water will be present in the pipe at all limes. Of course, If the system were to remain disused for a long period, say a few months, the treatment material might then dry out, and then the microbe colonies might need to be re-established, upon re-commencement of treatment operations. 4 [0021 ] An alternative to retaining the water in the treatment material by means of the absorbency and capillarity of foam, is that 1he water may be collected upon emerging from Ihe treatment material, and recycled therethrough, this would entail the use of a pump, pipe-work, flow control valves, etc, and Is riot preferred, but may be done in a particularly difficult Installation.

[0022] Another alternative, or supplement, to retaining wafer In the treatment material by the absorbency of the treatment material Is to configure the outlet port of the pipe in the form of a weir, Then, when water has finished draining out of the outlet port, still a volume of water is retained In the pipe, and in the treatment material In the pipe. Where the treatment material Is absorbent, the portion of 1he treatment material below the level of the weir will remain saturated, as will a layer of the treatment material above the level of the weir.

Above that, capillary acflon will be sufficient to support a smaller mass of water, so there are wet layers and moist layers, and above those, the trealment material will be dry. As a new dosing of water to be treated is added at the Inlet end of the pipe, the level of saturated, wet, and moist layers rises, until steady conditions once more obtain.

[0023] in most aomesiic wastewater systems, water enters the pipe not as a steady flow but as periodic doses, Of course, systems vaiy as to volume of water per dose, and as to the frequency of dosing. A lyplcal system might have an average dose size In the ten to twenty litre range, at a dose rate between ten and a hundred times a day,

[0024] As a water dose arrives, so the incoming water fills up the left end of the pipe. Now, there Is (or may be) more, water at the left end of the pipe than can be supported by the capillar/ action of the foam at that location. Water already present at the left end of the pipe is displaced further along 1he pipe, l.e to the right, the effect Is progressive, whereby when twenty litres of water enters at the left end, a corresponding Iwenty litres of water Is discharged (after a period of time) from the right end. But the water 1hat is discharged from Ihe right end Is water that has been resident Inside the pipe for a considerable time, having been displaced progressively, In a bucket-brigade mode of progression, rightwards along ihe pipe each time more water Is dosed In from the left. ■

[0025] It will be understood that, usually, as a nBW dose of water Is added at the left end, a corresponding equal volume of water will not be Immediately discharged at the right end. The discharge might be Immediate If the pipe had not been left to drain at all since the previous dosing, and the foam material In 1he pipe would be already saturated to full capacity, But usually, the foam material In the pipe will have drained enough, between dosings, that It takes a considerable lag time for a dose applied at the left end to produce a corresponding discharge at the right end. Indeed, the designer should seek to so arrange the system that, In spite of the dosings of water at the left end being periodic, there is a more or less steady trickle or discharge flow of water (of the same aggregate flow rate) atthe right end. The standing water level 27 represents the level at which the water Is retained, by capillary action, over substantially long periods; dosing causes the water level to rise quite quickly, at the left end, above the level indicated by numeral 27, but then the water level drops back to the level 27 much more gradually. Consequently, water trickles out gradually from 1he right end. That is to say, although the water entering the Inlet end tends to be in spaced doses, water may emerge from the outlet at a more or less constant flow rate.

[0026] The designer should see to It 1haf the system is sized, in relaiion to the dosing rate, such 1hat the water has a residence time, within the pipe, of preferably about twelve hours, Of course, the residence time depends not only on the sizing and arrangement of the treatment material, but also on the wastewater-produclng habits of the owners/users of the system. But the designer should recognise that a system In which wastewater might pass right through the aeration station In less than about 1wo hours would not be expected to treat the water adequately. Less than that, and the degree of maintenance to keep the foam from becoming plugged up would be excessive.

[0027] The water residing In the pipe is within a few centimetres of a supply of oxygen, l.e the air In Ihe air-passage 24. Under these conditions, colonies of aerobic microbes can form on the malrix of 1he foam material, and be extremely viable, The water level is static most of the time [during operation of the system), and the water Is slowly moving through Ihe pipe, whereby the microbes have ample opportunity to extract the needed nutrients from the water, but the water is continually being replaced, so the microbes receive fresh supplies of nutrienls.

[0028] If 1he designer can arrange for the stabilised capil!ary-supporied depth 27 of the water to be mare than about five cm, the aerobic reactions can be so thorough that a lower portion of the depth of water can be depleted of oxygen. In that case, anaerobic reactions can take place; these can be beneficial In that. If the conditions were only aerobic, slime and solids might tend to build up In the foam. It Is beneficial to promote the anaerobic conditions, if possible, because these are the products that are predominantly addressed by anaerobic treatment.

[0029] The block 28 of foam as illustrated in Fig 2 typically Is 1V2 metres long. Several such blocks 28 make up the whole length of the body 23 at foam. As mentioned, tie pipe 20 is fifteen metres long, and, In this particular case, the pipe contains ten blocks. As will be understood from Fig 3, sometimes the blocks 28 of foam will abut tightly, with no gaps, but it does not matter If gaps do appear between the blocks. Of course, gaps waste premium space, and are disadvantageous for that reason.

[0030] The pipe 20 may be In one long length, rather than short lengths joined together. The designer preferably should arrange the system so that the foam material can be removed and replaced, for future servicing, which Is generally more convenient If Ihe pipe Is straight, and In short lengths. [0031 ] The blocks should be assembled Into Ihe pipe such that no passageway or conduit can open up, being a passageway that would allow the water to by-pass the foam, because that might allow the water to flow along the pipe wilhout encountering the microbe colonies. It Is important that the water does not |ust quickly pass through the habitation of a few microbes, but that the water should encounter metre after metre of vigorous colonies of microbes.

[0032] The blocks 28 must be the right way up; If any biock were orientated such that the air-passage 24 was near the floor 26 of the pipe, water wouid simply flow through the air-passage, wtfhout treatment. While If Is not essential that the air-passages of all the blocks be exactly at the top of the roof 25, it is important that the blocks should be orientated relative to each other such that the air-passages of the respective blocks match up, so that alr can pass along the aggregate length of the pipe.

[0033] In some cases. It may be adequate for the air-passage 24 to be open at just one end of Ihe pipe 20, but preferably 1he air-passage Is open at both ends, in order to encourage air to move freely along the air-passage, Holes may be punched in the roof 25 of the pipe, to improve air circulation, if desired [provided water cannot escape tfirough those holes, under all conditions of dosing rates and flow volumes). The piudent designer alms to provide 1hat the system will cope with [short-lived) abusive overloads of the system. 6

[0034] Upon emerging from the exit-end 29 of the pipe, the-treated water remains to be disposed of, It may be appropriate to empty the water straight into a stream or laice. Or, It may be appropriate to collect the water, , for recycling or other purposes. More usually, however, the requirement Is for the water emerging from the pipe to be Infiltrated Into the ground. In Fig 1, this is done through an infiltration station 30.

[0035] In Fig 1, the pipe containing the body 23 of foam, comprises a highly efficient aeration station 32. The aeration station 32 promotes the oxidation reactions; i.e If the water from the septic tank has a high organic content, the aeration station supplies the oxygen needed to diminish the carbonaceous-BOD and Ihe total suspended solids (TSS). Oxidalion (nitrification] of ammonium can also occur.

[0036] There are many conventional structures that can be used at the infiltration station 30. It may be noted that In a conventional septic treatment system, which has a conventional tile-bed soakaway, the tile-bed soakaway comprises not only the infiltration station, but the tile-bed soakaway also doubles as ihe aerobic treatment station. It Is recognised that the function "of the conventional tile-bed as an infiltration station Is much less demanding (in terms of the size of bed required) than Its function as an oxidation treatment station.

[0037] In Fig 1, the infiltration station 30 comprises a soakaway, but now the soakaway can be much smaller (and cheaper) than the soakaway would have to be If the soakaway itself served also as the aerobic treatment station. To repeat: a conventional tile-bed combines the functions of aeration station and Infiltration station. Since a conventional lile-bed does not always make a very efficient aeration station, the whole Installation is . large, which Is not only expensive but occupies a large area of land. By separating the aeration function and the InfiHration function Into two separate stations, l.e the aerobic treatment station 32 and the separate Infiltration station 30, as In Fig 1, the overall Installation can be more economical, and can use the available premium space more efficiently.

[0038] Fig 4 is a plan view of a wastewater installation. Un-aerated water from the septic tank enters the system at 34, and a distribution box 35 (of conventional design) distributes ihe water between the four pipes 20, as shown. The four pipes as shown are straight and parallel, but lhat is not essential: sometimes It might be more convenient to anange the pipes In curves, to follow the contours of the land, or for the pipes 1o fan out from the distribution box.

[0039] Once the sewage flow rates and dosage requirements that the system will have to cater for have been determined, the designer needs to choose between having one large pipe, or several smaller-diameter pipes. Hie factors to be considered when making this choice have to do not so much with the aeration station itself, but e.g with the depth of workable soil at the site, and the ability of 1he ground material at the site to accept the discharge of treated water over a long period of seivice.

[0040] The treatment material as shown in Fig 2 is of open-cell, or Interconnected-cell, plastic foam, Foam Is preferred as the microbe-habitation material because foam can be produced in the desired shapes easily and cheaply. Foam can be made flexible and resilient, whereby the foam can be a tight fit In the pipe, which ensures water cannot by-pass the foam, and by-pass the colonies of microbes residing In the foam. Piasiic foam material can easily be formed Into a cross-sectional shape that just fills the pipe. [0041 ] Other materials may be used as the microbe-habitation material If 1hey are absorbent and permeable. For example, peat may be used. Anoiher suitable material Is rock-wool, Rock-wool comprises a mat of fine threads or fibres of rock, ceramic material, glass, etc. Rock-wool, tike open-cell foam, provides very 7 effective habitations for microbe colonies, while having only a minimal tendency to become clogged with slime and solids,

[0042] Rock-wool also, lite foam, has the capillarity or absorbency to retain the water within the material for a good time period, it Is beneficial for 1he water to be'retained, since that enables an efficient use of the material. As .water drains out of the treatment material belween dosings, inevitably a certain portion of the volume of the treatment material becomes emply of water belween dosings; and the smaller this portioa the more efficient the use of the material, and the more efficient the use of the volume needed to contain the material.

[0043] To Illustrate this point, attention Is directed to Figs 5a,5b,6a,6b. (In Figs 5a,5b,6a,6b, the vertical distances are exaggerated.)

[0044] In Figs 5a,5b, a porous treatment material comprises highly-absorbent foam or rock-wool. Fig 5a shows the situation just after a dose has been applied to the left end of the pipe, The material Is saturated, right to the top of the material, for a length LS, the rest of the line of the \fcafer-table being as illustrated, Then, dosing ceases, l.e no more water is applied to the left end. Some water drains out of the right end of the pipe, and ttie water-table In the pipe gradually sinks. After a time, which might be several minutes, or perhaps half an hour or more, the water-table has sunk to a stabilisation level, as shown In Fig 5b, at which no more water, or only a small trickle, drains out of the right end (assuming no more doses have been applied In the meantime at the left end).

[0045] In Figs 6a,6b, the porous treatment material Is a coarse sand or gravel, having only a minimal (though not zero) absorbency. (The designer should not specify a fine sand, which, though more absorbent, would not have the required permeability.) Now, Immediately after the dose Is applied (Fig 6a), the equivalent of the saturated length LS is much shorter. Also, (Fig 6b) Ihe belween-doslngs water-table stabilises at a much lower level. Furthermore, the time taken for the water to drain out, from the Fig 6a condition to the Fig 6b condition, is shorter than the time for the water to drain out from the Fig 5a (absorbent foam material] condition to 1he Fig 6b condition.

[0046] The volume of wastewater lhat is effectively presented to the microbe colonies for treatment depends on the volume of wastewater lhat is retained within the treatment material belween dosings. The effectiveness of capillary absorbency may be seen by comparing highly-absorbent foam or rock-wool (Figs 5a,5b) with minimally-absorbent sand/gravel (Figs 6a,6b), In Figs 6a,6b, the length of the pipe, and the length of 1he treatment material, would have to be much greater In order fa the retained volume of wastewater to be comparable.

[0047] Sand can be used in the Invenlion, provided It has some capillary absorbency, and provided the extra length of pipe can be accommodated. It is contemplated that, where the material lacks absorbency, In place of resorting to more material, the water emerging from 1he exit end of the material can be collected and recycled through the trealment material; possibly several times. A sand, or gravel, or other porous material, that basically has no capacity for caplllaiy absorption, is not preferred for use in the invention. [004B] A material Is suitable for use In the Invention If the material is capable not only of supporting vigorous colonies of microbes, but preferably is capable also of caplllaiy acton; that is to say, 1he material should retain and support a substantial body of water, within 1he material, after the material has been saturated with 8 incoming water, Thus, the material Is such that water moves through the pipe, from end to end, progressively, with each dosing of Incoming water,

[0049] To be suitable for use in the invenlion, the material has to be porous and permeable. Fine sand or Slit would soon become clogged and plugged with solid products, and should not be used. In fact, when It comes to clay. silt, sand, gravel, etc (termed particulate materials herein), as the material for ttie invention, ft should be understood that 1he range of properties that will lead to effective treatment Is quite narrow; the smaller the particulates, generally, the more absorbent the sand material, but the more likely ft is that the material will become clogged with slime and solids. Thus, although particulate materials can sometimes be acceptable, generally, particulate materials are not preferred.

[0050] Preferably, the nature and volume of the treatment material, and its arrangement In Ihe pipe, should be such that the volume of wastewater retained In the treatment material belween dosings is several times larger than Ihe volume of the Individual dosings. [0061 ] To use rock-wool as the microbe-habitation material, Ihe material may be pre-formed into a body having a cross-sectional shape similar to that shown in Fig 2, or may comprise loose material, placed In a bag, with an air tube (and with a means for ensuring that the air tube is at the top of Ihe pipe).

[0052] The shape of the pipe and of the treatment material should correspond, to make sure there are no free channels or pathways the water might take through the pipe, and thereby by-pass the treatment material, The treatment material should be tailored to fit tightly against -the (bottom of the) pipe, whether 1hat is round, square, or of another shape.

[0053] After the treatment system has been operating for some time, the trealment material can be expected to have become divided into treatment zones, The treatment material in the first few metres of the treatment pipe will be stained and discoloured, which is the usual indication of an effective decrease of the carbonaceous-BOD [organic) content. Downstream of that zone, the treatment material is less discoloured, and this less-discoloured zone extends for many metres, indicating a large capacity for treating 1he ammonium and pathogen pollutants. In the pipe, dawn to very low concentrations.

[0054] It can be expected that a well-designed treatment pipe system will clean the water down to a level of ten mg c-BOD per litre, ten mg TSS per litre, and Ihree mg ammonium per litre.

[0055] After a long period, it should be expected that some zones of the treatment material In the pipe might have become clogged with a build-up of slime and solids, The system can cope with such clogging, because. If It happens, doses of Incoming water simply flow along the air-passage 24, and by-pass the clogged area; the incoming dose of water passes downstream along the air-passage until it reaches a zone of the treatment material that is not clogged, An Incoming dose of water simply overflows along the air-passage until It can soak down Into 1he foam material.

[0056] The treatment material cannot be expected to last for ever, and the system may have to be cleaned out. This Is a simple enough operation, In that the designer can easily arrange for the blocks of foam to be removable from the pipes, for service, and can usually arrange that the blacks are removable, and replaceable, without 1he pipes having to be dug up or dismantled. 9 10057] As shown, the pipe 20 is ananged In a horizontal configuration and water passes along the pipe In the manner as described; that is to say, as an Incoming dose appears at the entry-end of the pipe, corresponding volumes are water are displaced, in bucket-brigade fashion, along ihe length of the pipe, and a corresponding volume of water drops out of the exit-end of the pipe, over a period of time, To promote this manner of movement of water through the treatment pipe, it Is not essential that the pipe slope downwards towards the exit end. The pipe might even slope (veiy slightly) uphill, and a volume of water would still emerge from the exit-end when a dose is applied to the entry-end (Uphill Is not recommended, though, because water might pool In certain areas and become stagnant, or block the air-passage.)

[0058] The designer should arrange that the slope of the treatment pipe should be kept to a minimum. Preferably, the treatment pipe should be horizontal, or slope slightly downhill. It is recognised that the treatment pipe, containing a body of foam or other treatment material, does not need to be Installed with a constant accurate horizontality, or a constant accurate slope, So long as the pipe is approximately horizontal, that will do. In the treatment pipe, it is an aim that the water should flow horizontally along the pipe - although of course 1he predominantly-horizontal flow Is driven by gravity-Induced pressure heads. Alternatively, sometimes, depending on the nature of the treatment materia!, and the manner of retaining water in the treatment-pipe, the treatment pipe may be inclined at a considerable slope,

[0059] Figs 7 and S show an alternative manner of infiltrating the treated water Into the ground. Here, the ■treatment pipe 41 is located Inside a chamber 40, which Is formed from a plastic hood 42. The hood Is located In an excavated trench, and covered over with soil etc. The design of the hood and the trench is such that air can enter Ihe air-passage 43, it can be arranged that air enters Ihe chamber through 1he hood, and through a light covering of soil, If the hood and the soli are suitably permeable, The treatment pipe 41 Is supported off 1he floor 45 of the chamber, either from the floor or from the hood.

[0060] Water emerges from the exit-end 46 of the pipe, Into the void space of the chamber 40, and travels along the floor 45 of the chamber. The floor may be bare soil, or may have pebbles etc to help spread the Infiltration uniformly over the area,

[0061] Figs 9 and 9a show another alternative arrangement. Here, a similar chamber 47, with a hood 48, Is provided, but now the trealment material 49 is placed on the floor of the. chamber, l.e on the ground. The pipe 50 itself contains no treatment material. Incoming doses of water Iravel along the pipe, and 1he water drips from holes 52 down onto the treatment material underneath. The water 1hen moves laterally through the treatment material before entering the ground. The drip-rate through the holes 52 and the volume of 1he pips 50 should be small enough that one dose of water fills the pipe; if the pipe were larger than that, or the volume of water per dose were too small, the water in 1he dose might not reach the far end of the pipe. To ensure that the pipe Is filled along Its length, It might be preferred for the incoming water to be collected prior to being fed into the pipe, and pumped Into the pipe in doses of, say, twenty litres.

[0062] In some cases, steps must be taken to ensure that the water passes lengthwise (i.e horizontally) for a considerable distance, through the treatment material. To this end, it may be arranged that a plastic trough 54 be Interposed belween the treatment material 49 and the soli of the floor of the chamber 47. The trough 54 ensures that water cannot escape downwards and Into the ground soil except at gaps or holes 56 In the trough. Ihe gaps 56 do not lie underneath the drip holes 52, but are positioned so that water has to travel horizontally through the treatment material 49.

[0063] Basically, in the invention, the volume of trealment material through which the water passes Is large, but the volume is configured as a long channel of nairow cross-sectional area, rather than as a volume having a short-length, wide-area, configuration, The long-narrow configuration of the conduit of treatment material through which the waier Is constrained to pass, ensures that the incoming doses remain within the treatment material for a long residence time, The long-narrow configuration promotes the desired bucket-brigade mode of transport of the water progressively along and through the treatment material. The long-narrow configuration ensures that, as much as possible, the water cannot by-pass any portion of the volume of the treatment material.

[0064] Any portion of the volume of trealment material that Is not effectively being used to treat wastewater, would be wasted. It Is an aim of the Invention to maximise the portion of the volume of the treatment material ' that is available for use, and Is used, to treat wastewater.

[0065] Another major benefit that arises from the treatment material being configured In the long-narrow configuration Is that the water fo be treated Is applied, locally, just to one end of the treatment material. This may be contrasted with conventional systems In which the Incoming water has to be forcefully spread out, and spread out reasonably evenly, over a horizontally-large area of trealment material. Consider, for example, the conventional systems where Ihe treatment material Is configured basically as a horizontal mat, and the incoming water has to be sprinkled over ttie whole of ihe upwards-facing surface of the mat. This requires the provision of a [powered) sprinkler or similar horizontal water-distribution system. In those systems, if ihe water were to be fed Just to a single point above a horizontally-extending mat, ihe water would not spread evenly over the whole mat, but would simply penetrate down through ]ust the immediate sector of the treatment material.

[0066] By contrast, the long-narrow configuration of the treatment material does enable water to be fed Into a large body of treatment material from a single inlet point, without the use of sprinklers or distribution systems. In a well-engineeied system that embodies the invention, all the water entering the system, upon being simply placed at the left end of the pipe, cannot fail to flow along the pipe, and cannot fail to pass through metre after metre of well-aerated microbe-laden treatment material,

[0067] It Is not ruled out In the invention that a pump might be needed for moving water to the inlet point, However, a conventional system 1hat uses a sprinkler to spray water outwards and downwards onto the treatment material is much more likely to need a pump than a system that simply places the water alongside the treatment material.

[0068]. Some of the differences will now be considered between the above-described type of aerobic Ireaiment station, and a conventional aerobic treatment station, of the kind where water falls or trickles downwards'through the treatment material. In the conventional system, a water distribution system has to be provided, to spread the water, horizontally, over the whole area of treatment material. Any portion of the materia] to which water was not conveyed by the horizontal distribution system would Just be wasted. In the present system, water is caused to flaw Ihrough, and to fully utilise, the whole body of treatment material, simply by the geometry of the pipe or trough. No powered sprinkling or distribution system is needed, The water is fed In at the Inlet end of 1he pipe, and simply flows horizontally along the pipe, through the body of treatment material, and out at the olher end of the pipe.

[0069] With this arrangement, the designer can arrange that the water flows through many metres of treatment material, and Oust as Important) that the water cannot escape or by-pass that long length of 11 trealment material. The line of the many metres of treatment material through which the water passes is horizontal, not vertical, and that line can be made many metres long with very little difficulty of structure. By contrast. It would be very inconvenient to provide for water to flow through many metres of trealment material, if the water were arranged to flow vertically downwards through the treatment material, whereby a long vertical flow really cannot be done In the context of a small domestic treatment installation.

[0070] Furthermore, water flowing horizontally through a body of treatment material can veiy easily be retained In the body of material, whereby the treatment reacilons can continue over a long period; by contrast. In a vertical system, the water is only retained within the treatment material for a few moments. [0071 ] It is not essential fiat the treatment material must provide capillary action. The treatment material should be such thatlhe material will support colonies of microbes, and should be such that the material will not easily become clogged with slime. Also, the configuration of the treatment material, and of the constraints that determine the pathways the water takes In passing through the treatment material, should be such that the doses of water pass through In bucket-brigade mode.

[0072] These criteria can be met with an alternative form of material, as shown In Fig 10. In Fig 10. a round pipe 57 contains inner and outer pieces 58,59 of bristle-mat. The mat comprises artificial turf, such as AstroTurf [trade name). The two mats of artificial turf are rolled Into spirals, one left-handed, the other right, The arrangement leaves an outer gap, which serves as an air-passage 60, running along the length of the pipe 57. The arrangement also leaves another gap 62, running the length of the pipe, being the central tubular passageway as shown. The mat should be so selected for size, and be so arranged, that the bristles or blades of 1he artificial turf are compressed sllghliy, whereby ttie mat fits tightly against the wall s of the pi pe.

[0073] Water dosed Into the pipe 57 enters between the turns of Ihe mat, and flows along lengthwise between the turns, The artificial turf material provides an excellent habitat for microbes, and the arrangement means that there Is ample provision for circulation of air, and for oxygen access for microbes residing on the bristles or blades of the turf mat.

[0074] Artificial turf does not promote a caplllaiy action, and therefore If the pipe 57 as shown in Fig 10 were to be inclined downhill, It might happen that too much of the water being treated would drain out of 1he pipe, and out of the treatment material, between dosings. The Fig 10 pipe therefore should be arranged so that water does not drain completely, bertween dosings, which can be done by placing the water oullet (slightly) higher than the bottom of the pipe. This can be done by forming a weir at the outlet end of the pipe. Now, the water remains In the turns of the rolled mats, between dosings, and the long-narrow character of the water-ways between the turns promotes the desired bucket-brigade mode of movement of water along the pipe, as each new volume of water is dosed in. The water should occupy approximately half the cross-sectional area of 1he pipe; the line 63 indicates an optimum residual water level,

[0075] The retained water level should not be so high that the gap 62 provides an open channel, along which water could flow without hindrance straight to the outlet. The bristles and blades of the artificial turf material do provide a hindrance to flow, in that they take substantially all the kinetic energy out of the moving water; it should be regarded that water passes along the pipe 57 by seeping Iherealong, rather than by flowing with a velocity, and the pipe, and the roil of turf, should be sized accordingly.

[0076] If an area of the blades or bristles should become clogged with solids and slime, water could flow up 12 and around the curved paths between the tums, and over the obstacle. There Is generally no need for ttie mat to be perforated (to give direct communication between turns) and too many perforations might lead to too marry possible pathways through the treatment material, and to the water starling to establish channels and pathways, On the other hand, If desired, the mat may be perforated.

[0077] As mentioned, It Is a preferred feature of 1he Invention that the water be constrained to flow through a volume of treatment material that Is configured as a long-narrow volume. The more the material Is disposed, with respect to the passing water, in a long-narrow configuration, the less likely It is that preferred pathways might develop In the material, whereby water might by-pass some of the material ,

[0078] The manner In which the long-narrow character of the treatment material Is defined, In the context of the Invenlion, will now be discussed. The water may be regarded as flowing through or along a pipe or trough, In which the treatment material is contained. The trough has a floor, which is contiguous with left and right side-walls.

[0079] If the water-concfuif had a simple rectangular cross-section, the floor and side-walls of the water conduit would be immediately defined. When the water-conduit Is some other shape — a round pipe, for example—Just what constitutes the floor of the water-conduit Is not so Immediately clear. In the context of the Invention, the floor of the water-conduit is preferably defined as including not only the bottom of the conduit but also those portions of the conduit walls that face upwards, and lie at no more 1han thirty degrees to the horizontal. Insofar as It makes a difference, a portion of the water-condutt walls that lies more steeply to the horizontal than thirty degrees should be regarded as a portion of the side-wall of the water-conduit, rot as a portion of the floor,

[0080] The treatment material rests on, and makes contact with, the floor of the water-conduit, The treatment material also makes contact with at least a lower portion of the side-walls of the water-conduit. The floor of the water-conduit Includes contact-patches, where the treatment material actually touches the floor, and non-contact-areas, between the contact-patches, where the treatment material does not touch the floor. If the treatment material is in touching contact with the whole of the floor surface, the non-contact-areas In that case would be zero, and that Is to be desired, but zero Is not essential. [0081 ] The wafer, in passing from the enlry-poit to the exit-port, takes flow-paths through the treatment material. The flow-paths are traced on the floor of Ihe water-conduit, by water passing from the enlry-port to the exit-port, and the flow-paths Incorporate the non-contact-areas of the floor, if such be present.

[0082] The clearest-fiow-path Is the flow-path that brings the water Into the least contact with 1he treatment material, It Is a preferred feature of the Invenlion that even the clearest-flow-path lies within 1wo millimetres of the treatment material over a distance of at least ten metes,

[0083] h the Invention, It Is preferred that 1he width of the water-conduit be narrow, defined as follows. The width of the floor of the conduit, as measured laterally with respect to the length of the water-conduit, Is Wl metres at a point Tl, Is W2 metres at a point T2, and is WN metres at a point TN. T1,T2,,„TN,.. are points along the length of the water-conduit at which 1he treatment material Is present, it Is preferred, In the Invention, that at least eighty percent of the widths Wl ,W2„ „WN„. are less than forty centimetres. The aggregate of all the flow-paths through ttie trealment material is the stTeam-pafh, PCT/CA02/0 J 005 13

[0084] It should be noted that it would not be satisfactory to provide Ihe horizontal-flow of water through the treatment material. If the body of treatment material were wider, horizontally, than the dimensions Indicated. The narrowness is important because it ensures freedom from channelling and pathways through the body of material, If the body of material were provided in the form of a flat slab of foam, say 200 cm wide, inside a suitably-shaped trough with a horizontal floor, and If the water were fed into the slab via an entiy chamber across the whole width of the slab, the water can only be expected to traverse lenglhwise along the slab, evenly across the slab, for a small distance. With a slab that wide, channelling and pathways would very quickly start to develop, so that, mote than a metre or so away from the entiy chamber, only a fraction of 1he width of the slab would be being utilised. Thus it is recognised that the horizontal flow ot water should be channelled between Impermeable side-walls, which confine the flow to the narrow, flow-way, as described. Providing extra width to a body of treatment material does not seive to improve treatment, because the extra width Is wasted, as the water foims pathways and channels through the extra width. [0085J The designer should take precautions against freezing, if appropriate.' The pipe should be free-draining, and typically buried with about fifteen cm of soil above the pipe, to accommodate minus 20 degC. More soil or insulation should be provided over 1he pipe !n colder climates.

THE SECOND ASPECT OF THE INVENTION, IN RELATION TO THE PRIOR ART

[0086] In a second aspect, this Invention relates to the treatment of wastewater, being wastewater e.g from a domestic dwelling, and relates especially to the treatment of wastewater as has been traditionally carried out in a septic tank.

[0087] Septic tanks have been well known for many years, and many designs have been proposed, ranging from the simple hollow rectangular box-shaped tank, to more intricate and sophisticated designs. In which separate compartments, baffles, and the like, have been used. These sophistications have been aimed at making sure the septic tank performs properly, in the sense that no water can emerge unseated from the tank, and at making sure the sepflc tank performs efficiently, in Ihe sense that the septic tank performs its functions using a minimum of volume and space.

[0088] The traditional septic tanks have been made of concrete, metal, plastic, etc. The material has to be watertight, and must remain so for many years, and has to withstand the stresses arising from settling of the ground, from overloqdlng and other abuses, and the like, Septic tanks have been designed with access hatches, whereby a person can inspect the Interior and monitor the build-up of sludge and scum, and through which the sludge/scum can be extracted from time to time.

[0089] The second aspect of the invention Is concerned with achieving the performance of a traditional septic tank, Including promoting the anaerobic digestion reactions, separating sludge and scum from the water by settling, etc, but with achieving this performance In an apparatus that is of a more convenient and efficient configuration and size. One of the alms of the invention Is to make it easier to find room for the apparatus, and to make less expensive 1he task of installing the apparatus, than has been 1he case with the traditional septic tank designs, and to allow easy installation In areas of high water table or high bedrock,

[0090] In one preferred embodiment, the septic tank is basically configured In the form of a long, narrow, 14 pipe. The pipe may be of extruded plastic, having a diameter typically of fifty or sixty centimetres, and being four or more metres long. Such pipes are readily and inexpensively available. They are intended fa commercially conveying water, including wastewater, and are intended to be buried In the ground. These relatively small diameter extruded plastic pipes are light in weight, whereby 1wo persons can easily lift a length of the pipe down from a truck, manhandle it, and Install it in an easily-prepared shallow trench, In the ground, The second aspect of the invention lies In configuring a structure such as a pipe of this kind, as a septic tank. [0091 ] As mentioned, rectangular concrete septic tanks are traditional and well known, as are metal tanks.

Both are readily available, with or without internal baffles. However, bath these materials deteriorate In sewage, especially where sulphur is present. Also, septic tanks made of plastic are known, In particular, it is known to provide a septic tank In 1he form of a round plastic body, typically about one and a half metres In diameter, and 1wo or three metres long, Theoretically, this body could be extruded, like a pipe, but a more favoured manner of construction Is to fabricate the body over a mould, in, for example, glass-fibre-reinforced plastic. Similarly-fabricated plastic end-caps are cemented onto the ends of the round body, prior to installation in the ground. Hatches, ports, etc, have been included In the as-fabricated structures.

[0092] The known moulded-plastic septic tanks have been lighter in weight than the comparable concrete tank. However, when the tank is pumped out during service, or If the water table should rise, a tank made of plastic might be prone to flotation, Polyethylene and fibreglass tanks have improved chemical resistance. Hbreglass tanks are very expensive, Polyethylene tanks are not so durable, and can collapse If not installed and backfilled with unusual skill and care. Also, the known plastic tanks still take up more or less the same size of hole in tie ground, so there Is little saving of space, or of amount of excavation. Also, although the plastic tank Is lighter, still a crane Is needed to lift the plastic tank off the truck, move the tank to the prepared (excavated) hole, and lower the tank into the hole. As a result, the savings overall, arising from the use of a plastic tank, are marginal.

[0093] As mentioned, it Is known to incorporate baffles info a concrete or metal tank. The baffles create mechanically-defined pathways along which the water passes. Without the baffles, a wide conduit would be available for the water flow. The tendency is, when the conduit is wide, not for the water to flow at an even rate over the whole cross-sectional area of the wide conduit, but for the water to start to establish unwanted pathways. It has been recognised that, In a case where the water can pass rapidly along a pathway that has developed, from inlet to outlet, the volume of the tank Is not being used efficiently, Some of the water, l.e the warier in the pathway, now has a short residence time, the rest much longer.

[0094] Only when the residence time of ail the water is the same is ihe volume of the septic tank being used at maximum efficiency, The baffles serve to define the pathways along which the water must pass, and serve to even out some of the differences in residence time, Traditionally, baffles provide and define a long/narrow passageway for the water, where, without Ihe baffles, the passageway would have been wide and short.

[0095] But baffles are awkward structures to incorporate Into a septic tank. If the baffles really are effective to brtng all points of the septic tank into equal effect, they will restrict access, and make servicing and cleaning out the tank almost Impossible. Plus, the tank is still a tank, even If if contains baffles. And as such. It still requires the heavy lifting equipment, the disruptive excavations, etc, as described, As an example, a 3000-litre traditional (concrete) septic tank may be considered. Such a tank typically requires an excavation that is 2M> by Th metres In area, and 2 metres deep. Using ihe septic-pipe principle (as described herein) instead, the same or better performance can be achieved with a 15 or 20 metre length of 40 cm diameter pipe. A suitable trench PCT/CA02/0100S ' for this pipe can soon be excavated, without heavy machinery; and two people can easily pick up 2 or 3-metre sections of 40cm (plastic) pipe, and instal them In a trench, by hand. Because the volume of the pipe is utilised so effectively, frie overall volume of the treatment facility can be reduced. But what can be more important is that ttie depth of excavation Is reduced; and the fact that no crane is needed to install It, especially In difficult and remote areas,

[0096] The Invention provides another manner by which water can be made to move through a water treatment system, gradually and progressively, Ihe whole body of water moving forwards, with each incoming dose at the Inlet.end, as an integrated unitary whole body, towards the oullet end.

[0097] Again, the aim Is to make sure that every drop of water passing through the tank has the same residence Hme, This aim can be expressed conversely, l.e as the aim to make sure that all of the available space Is being utilised equally for the purpose of promoting the treatment reactions and processes.

[0096] The second aspect of the Invention lies In conducting the wastewater through a septic trealmenf-trough, rattier lhan through a septic tank. The preferred form of the treatment-trough Is a treatment-pipe, and ttie invention is described herein mainly as it relates to the treatment-pipe.

[0099] The treatment-trough, or treatment-pipe, has a long/narrow configuration, The narrowness of the cross-section means that substantially all of the cross-section Is utilised, more or less equally, for treatment, in a ■traditional septic tank, as mentioned, it does not take long for channels and pathways to start to develop tn the tank. Then, the incoming doses of sewage water start to take a short-cut to the outlet, and the rest of the volume of the tank is simply wasted,

[0100] As a desideratum, the treatment-pipe and the apparatus should be so configured that, when a dose of sewage enters the inlet the whale volume of water contained in ihe apparatus moves forwards towards the outlet, as a unitary moving front, over lis whole cross-sectional area. Ideally, every drop of water that emerges from the ouiiet has been Inside the pipe for the same residence time as every other drop, When that is so, the treatment-pipe Is at its maximum volumetric efficiency, l.e Its efficiency In terms of minimising the water volume that Is needed, in the pipe, to achieve full treatment. Of course, the ideal cannot be achieved, wherein all drops of water would have exactly the same residence time; however, the long/narrow treatment-pipe performs much closer to the Ideal 1han a traditionally-shaped septic tank.

[0101] The scope of the second aspect of the Invention Is set out in the accompanying claims,- but may be summarised as follows. Excess water In the container drains out of the outlet port, leaving a minimum-standing-body of water retained In the container. This mlnimum-standlng-body of water has a standlng-water-length, between the inlet and outlet ports of the container, (In fact, for the sake of clarity of definition, reference Is made to an Inlet-point and an outlet-point, which are the nearest points within the standing-body to ttie respective ports.)

[0102] At each point along the standlng-water-lenglh, the mlnimum-standing-body of water has a standing-width. At a polnt-P, the width Is standlng-wldlh-P. Similar, 1he standing-body has standing-depth-P at point-P.

[0103] Some of Ihe polnts-P along the slanding-water-length comprise also polnts-T of Ihe trough, A polnt-P Is also a polnt-T If, at point-P, the standlng-width-P Is less than about 1/4 of the standing-water-length. Preferably, the standing-depth-P is also less than 1/4 of the standing-water-depth, Any point In respect of which the 16 standing-width at that point is greater than 1 /4 of the standing-water-length Is not a point of the trough,

[0104] There is also an overall width limitation In respect of the trough, that the standing-width should not exceed 120 cm. That Is to say, any polnt-p of the container at which the width does exceed 120 cm is not a point-T of the trough. Naturally, ttie wider widths would only be considered In very large installations, but the designer should have it in mind that at widths abwe 120 cm, freedom from channelling becomes very doubtful. Therefore, the designer should over-engineer the container, bearing In mind that much of the volume might be wasted due to channelling. A septic container is fed from an Inlet-pipe which typically is around 15 cm diameter or less, and the designer cannot count on spreading that concentrated in-flow evenly over a larger width lhan 120. And the smaller Ihe width, the better the assurance lhat all tie width will be utilised equally. Thus, designing to a width limitation of 100 cm provides a good commercial margin. A width limitation of 70 cm means that the possibility of problems with channelling can really be Ignored. [0105J The trough Is the aggregate of all the polnts-T, i,e of all the polrrts-P at which the standing-width is less than 1/4 of the standing-water-length.

[0106] For the trough to be long/narrow, In the second aspect of the invention, the trough should be of least 1wo metres long, (tt should be noted that, to clarity of definllion, the narrowness .of the trough is defined in terms of the ratio of the width of the trough to the lenglh of Ihe container, not to the length of the trough.)

[0107] In a traditional septic tank, with baffles, the overall path as dictated by the baffles may bs long/ndrrow, within ttie above definllion. However, a tank with baffles is not Included In the Invention, for the reasons as will be described. A tank with baffles Is distinguished, In this second aspect of the Invention, by the feature that no portion of the wall of the treatment trough Is wetted on both sides by the water undergoing treafment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF SECOND ASPECT

[0108] By way of further explanation of the Invention, exemplary embodiments of the Invention will now be described wilh reference to the accompanying drawings. In which: Fig 11 Is side elevation of a treafment apparatus, installed In the ground, which embodies the Invention; Fig 12 Is a cross-section of a treatment-pipe; Fig 13 is a plan view of another treatment apparatus; Fig 14 is a side elevation of a further trealment apparatus; Fig 15 Is a plan view of another treatment apparatus.

[0109] The apparatuses shown in the accompanying drawings and described below are examples which embody the second aspect of the Invention. It should be noted that the scope of the Invention is defined by the accompanying claims, and not necessarily by specific features of exemplary embodiments.

[0110] The wastewater treatment apparatus 120 shown In Fig 11 Includes an inlet port 123, which receives sewage wastewater from a dwelling, for example a single-family house. The apparatus, to meet the usual codes for e.g a three-bedroom dwelling, should be able to cope with sewage being dosed into the apparatus at the dally rate of 1600 litres per day, being applied at the dose-rate of ten to fifty doses per day, and the following dimensions of the apparatus are set by the need to meet these requirements, 17

[0111] The apparcrtus 120 Includes an Inlet chamber 124, which comprises a 1,5 m length of plastic pipe, of diameter 60 cm, The apparcrtus also Includes an outlet chamber 125, which comprises a 1,0 m length of fhe 60 cm pipe. The chambers are manufactured with holes, having welded or cemented-on flanges and bosses 126, to enable inlet and outlet pipes 127,128 to be sealingly attached .Itiereto, and to enable a treatment-pips 129 to be connected between the chambers.

[0112] The treatment-pipe 129 Is of Inexpensive, readily-available, extruded plastic (polyethylene) pipe, having a diameter of 45 cm. Ihe treatment-pipe 129 is 16 m long, (Alternatively, the treatment pipe may be, for example, 60 cm diameter and nine metres long.) An insulafive and protective covering of soil, 30 cm deep, lies over the burled treatment-pipe.

[0113] The apparatus Is installed In a prepared (l.e excavated) receptacle in the ground. At fhe two ends, the excavation accommodates the inlet and outlet chambers 124,125. Between the ends, a shallow trench, barely-1 m deep, and % m wide, Is all that is needed to accommodate the treatment-pipe. Of course, heavy excavation equipment may be put to use, if available. But septic treatment apparatus is required in respect of all dwellings, Including those where access for heavy equipment is not so easy, and/or ihe ground is difficult to dig, whereby the minimal excavation requirement is especially beneficial. It Is an aim of the invention to treat the water in a pips or trough (which includes a conduit or culvert), the mechanical characteristics of which permit the designer to assure mechanical stability when Installed to only a shallow depth,

[0114] For the purposes of periodic cleaning and other service, the (horizontal) treatment-pipe 129 Itself might be difficult to reach. However, usually^ most of the heavy solids (sludge 146) will collect in the deposltlon-sump 148 of the inlet chamber 124. "ihe lighter solids [scum 147] will float on the surface of Ihe water In the Inlet-chamber. Access to the inlet-chamber may be had very easily, by means of a removable hatch 130. In fact, a basket may be placed In the Inlet-chamber, and the basket simply lifted out, through Ihe hatch 130 - sludge, scum, and all - for servicing. Solids can be expected to collect also In the outlet chamber 125, but In smaller quantities.

[0115] It is unlikely that there will be much build-up of sludge in the treatment-pipe 129 itself, since the movement of the water along the pipe (slow though that movement is) will tend to cariy solids along to the outlet. The pipe 129 may be set at a (slight) angle to the horizontal, tf desired, to help prevent bulld-up actually In the pipe.

[0116] Preferably, ttie treatment-pipe Itself Is completely filled with water, i.e there Is no air. and no access fa air, in the treatment-pipe 129. "Ihe pipe 129 is the place where the main organic digestion reactions take place, which reduce the C-BOD of the water being treated, and these microbial reactions take place under anaerobic conditions,

[0117] Generally, the Inlet and outlet chambers should be vented, to make sure there Is no bulld-up of pressure (or vacuum) inside. The venting may be done via the Inlet pipe 127, to a venting stack on the roof of the dwelling, to control odours etc. If 1he layout of the pipe permits a small airspace on top of the water in the pipe, that Is not too Important (cf. the airspace above tie water in a traditional septic tank), but still the water In the treatment pipe must not be allowed to become aerated, again as in a traditional system. Water undergoing septic breakdown reactions in the treatment pipe should remain substantially still, except for the occasional shifts due to fresh doses of wastewater being added at the inlet, 18

[0118] Major benefits of 1he invention include Ihe fact that Ihe long/narrow pipe-configuration Is excellent at preventing pathways from arising. As a result, all portions of the volume of ihe Ireatment-plpe contribute equally to overall treatment performance. Also, the excavated hole In the ground, as needed to accommodate 1he Ireatment-plpe, can be done with considerably less expense and disruption than the corresponding excavation needed to accommodate a traditional septic tank.

[0119] For the purposes of the second aspect of the Invention, the difference between a long/narrow treatment-pipe, as used in the Invention, and the long/narrow conduit that arises from the placement of baffles In a conventional septic tank, Is that a baffle Is a wall that Is wetted on both sides by the wastewater undergoing septic treatment. In the trealment-plpe, the walls of the treatment-pipe are wetted by the wastewater only on the Inside. The outside surface of the treatment-pipe wail is In contact with air, or with the ground In which the pipe Is burled. (Ihe ground might be saturated with water, but that Is other water, l.e not the wastewater undergoing treatment.) The traditional septic tank Is a large heavy cumbersome structure, and requires a substantial and expensive excavation, and the use of heavy equipment, for Its Installation. Even then, such structures are fragile. In Ihe sense that the tank can crack, or even collapse, for example If 1he ground should settle, etc, In the present case, however, the septic container, as a complete unit, has a long/narrow configuration; that configuration means 1hat the overall unit has very high integrity, as a structure. This may be contrasted with a traditional septic tank. In which the treatment path has been elongated by placing baffles Inside the tank; frie provision of baffles (baffles are welted on both sides by the water undergoing treatment) does not nothing to change the physical requirements and structural Integrity of what Is sfill a short wide tank.

[0120] As may be understood from Fig 11, when water enters the inlet port 123, frie volume of water In the apparatus Increases, and the level of the water tends to rise, thereby causing excess water to flow out from ttie outlet port 132, Water drains out of the outlet port, until only a minimum-standing-body of water remains in Ihe apparatus. The level of the mlnimum-standlng-body, and thus the volume of the minlmum-standlng-body, is defined by the height of the weir 134 at the outlet port 132. The water remains at this level until the next dose of wastewater enters at 1he inlet port.

[0121] Figs 11 and 12 illustrate how the dimensions that are important in the definition of the Invention [and especially in defining fhe long/narrow aspect of the invention) are determined. At the Inlet end, an inlet-point 135 Is established, as the point on the surface of the minimum-standing-body of wafer which Is fhe closest point to the Inlet port. Correspondingly, an outlet-point 136 Is the point on fhe surface of the minimum-standing-body of water which is frie closest point to the outlet port, A line is drawn, through the wastewater undergoing treatment, along the shortest route between these 1wo points 135,136. This line Is termed the standing-body-length 137.

[0122] At each point along 1he length of the standing-body-lengfri 137, the water has a standing-body-width 138. The standing-body-width is the overall width of the wastewater at that point. Usually, this width will be equal to the maximum horizontal distance apart of the inside-surfaces of the walls of the pipe, at that point. The standing-body-width Is the widest width of the water at the point, which may occur at any deptti of the water at ■that point.

[0123] Fig 12 Is a cross section of the treatment-pipe 129 taken at a particular point along tie standing-body-length 137. The standing-body-width Is the maximum internal (horizontal) width of the pipe. The deptti at which the standing-body-width occurs Is the depth at which the standing-body-width Is maximum. 19 .

[0124] The standing-body-width 138 would not be the width of the surface of ihe water unless the width of fhe I surface happens to coincide wlfh the maximum distance apart of fhe pipe walls. Besides, the water need not have a surface at all, over much of the sfanding-body-length.

[0125] Hie deptti 139 of the water is a vertical measurement. Tti6 depth Is affected by whether there is an airspace 140 above fhe water.

[0126] Point PI is a point on the inwards-facing-surface 142 of the pipe wall 143, and is a point on that surface that is wetted by the minlmum-standlng-body of wastewater that is undergoing treatment in the treatment-pipe, Point Q1 is a point on the outwards-facing-surface 145 of the pipe wall, being the closest point on the oulwards-faclng-surface from point P1, and is separated therefrom by ttie thickness Tl of the pipe wail at 1hat point. Point Q1 Is not wetted by fie minimum-standing-body of wastewater undergoing treatment in the 1iea1ment-plpe,

[0127] this condition (of not being wetted on the outwards-facing-surface) Is not true af a baffle, A baffle Is, by definition, wet on both sides. In the second aspect of the invention, no portion of the treatment-pipe wall 43 Is wetted on both sides by the water undergoing treatment. No portion of the wall of the treatment-pipe doubles as another portion of the wall of the treatment-pipe. The treatment-pipe is of long/narrow configuration, to ensure efficiency of usage, and the long/narrow configuration is achieved, not by putting baffles in a short wide tank, but by providing a structure that Is itself physically long and narrow, l.e the treatment-pipe.

[0128] The long/narrow configuration is preferably defined by the following dimensional parameters of the treatment-pipe: (a) the standlng-body-length 137 is at least four metres; (b) the volume of the minlmum-standlng-body Is at least 1,5 cubic metres; (c) referring to at least fifty percent of the points along 1he sianding-body-length, both the standing-body-width 138 at that point, and the depth of 1he water at that point, are less than one quarter of the standlng-body-length 37.

These dimensional limitations will now be explained.

[0129] Traditionally, the smallest size of septic tanks have had a capacity of around 2 cubic melres, which Is the size appropriate to (and fulfilling the codes for) a small single-family dwelling. Because the treatment-pipe utilises Its volume and capacity so veiy efficiently, an equivalent degree of treatment can be realised, with a treatment-pipe, of about l .2 or 1.5 cubic metres.

[0130] The long" aspect of the long/narrow configuration of 1he treatment-pipe Is determined by the limitation that the standing-body-length 137 preferably should be at least four metres. [0131 ] The "narrow" aspect of the long/narrow configuration is determined by the limitation that the treatment-pipe have a width 138 of, preferably, less than sixty centimetres. The narrowness requirement applies to 1he treatment pipe portion of the apparatus, not to the end-chambers, which may be wider. But the end-chambers should not account for more than fifty percent of the standing-body-length. At this, it Is easy to ensure 1hat no pathways develop in the pipe. The wider the pipe, the more possible It Is for. unwanted pathways to develop, and for the structure thereby to become inefficient. If the treatment-pipe were to have a width of more than about one quarter of 1he standlng-body-length, the development of unwanted pathways, over a period of time, would be more or less inevitable.

[0132] The treatment-pipe should not be so narrow that the water shoots along it at a high velocity, of course, given that motion of the water is not conducive to efficient settling-out of solid debris. A practical lower limit to the narrowness of the standlng-body-wldth 138 would be around twenty-five centimetres; below 1hat, the water would probably be moving too quickly.

[0133] It Is not essential that the whole minlmum-standlng-body of water be contained actually In fhe treatment-pipe. As shown In Fig 11, some of the water is contained in the inlet and outlet chambers 124,125.

[0134] The structure of Fig 11, i.e the treatment-pipe 129 and the two chambers 124,125, may be prefabricated and pre-assembled, as an Integrated whole unit, prior to being taken to the site. Alternatively, the final Insertion of the pipe 129 into ihe (factory-formed) flanges 126 In the chambers may be left, to be ■ completed upon Installation at the site, In that case, the ease with which the unassembled components can be handled and transported must be set against the difficulty of ensuring, on site, that the seal between the pipe and the chambers is done properly.

[0135] .Alternatively, the Inlet and outlet pipes 127,128 may be coupled directly Into the ends of the treatment-pipe, i.e the Inlet and outlet chambers 124,125 may be omitted, as separate structures. However, it Is more convenient for the manufacturer to make the Inlet and outlet chambers as standard components, and then the treatment-pipe 129 Is simply a length of standard cylindrical pipe, having no attachment structures fabricated Into it. Then, the length of 1he pipe is the only variable, installation to Installation. The presence of Ihe chambers 124,125, with their openable hatches 130, means that the settled-out sludge and scum can be easily accessed, and removed. Easy access is especially important for the Inlet chamber 124, since ttie sludge tends to settle out mainly near the inlet end,

[0136] However, the end-chambers should be regarded as being adjuncts to the treatment-pipe. A substantial proportion of the volume of the mlnlmum-standing-body of water undergoing treatment must be contained In tie long/narrow structure of the apparatus, l.e in the 1recrlment-pipe. That Is to say, at least one half of the volume of the mlnlmum-standing-body of water should be contained within tie treatment-pipe Itself. If the inlet and outlet chambers were to contain more than one-half of the total volume of the mlnlmum-standing-body, that would mean the chambers were too large, which would be an inefficient utilisation of the available space, and which would lead to the development of unwanted pathways.

[0137] Expressed as a linear dimension of the standing-water-length 13 7, preferably at least fifty percent of the standing-water-length should He wilhln the treatment-pipe 29 itself. Preferably, Ihe treatment-pipe acoounls for three-quarters of the standlng-water-iength.

[0138] it Is repeated that the treatment-pipe is the long/narrow portion of the apparatus, over which the standlng-body-wldth is less 1han one quarter of the standlng-body-length. Up to half of 1he total volume'of the minlmum-standlng-body of water may be contained elsewhere than in the treatment-pipe, where Ihe long/narrow limitation does not apply,

[0139] The Inlet chamber preferably Is deeper than the outlet chamber (and than the middle chamber), because It is Ihe Inlet chamber that collects most of the settted-out solid sludge. However, if the lie of the land Is especially difficult. It may be easier to excavate a deeper hole for the outlet-chamber or for the middle-chamber than for the inlet-chamber. In that case, the outlet or middle chamber may be lengthened p .e deepened) appropriately, and the main collection of sludge would then occur in that chamber. One of fhe 21 benefits of ttie treatment-pipe apparatus Is that. If the Inlet chamber Is shallow, whereby its floor is quickly covered with sludge, it Is unlikely that sludge will then build up actually rn the treatment-pipe, due to the (periodic) movement of water In ihe treatment-pipe. Of course, when the inlet chamber Is shallow, the prudent owner will monitor the apparatus more closely, to make sure fhe treatment-pipe is not starling to become blocked with sludge.

[0140] Ihe designer should prefer the inlet and outlet chambers to be small, to minimise the amount of extra excavation (l.e extra to the trench that will house the Irealment-pipe). The main benefit of the invention comes from the presence of the treatment-pipe, rather than from the presence of the Inlet and outlet chambers. One, or both, chambers, as separately-manufaclured structures, may be omitted, Again, the water contained In the chambers should not comprise more than half the total volume of the whole mlnlmum-standing-body.

[0141] The Irealment-pipe 129 preferably is a length of extruded round plastic pipe. However, other forms are contemplated, and, as mentioned, In ihe broad sense 1he treatment structure should be referred to rather as a treatment-trough, than a treatment-pips. Ihe treatment-trough must be watertight, as to rts bottom and sides, but there is no need for ihe freaiment-trough to be watertight as to lis roof. Ihe trough roof Is Ihere mainly fa physical protection - to prevent objects falling into ihe water. The treatment-trough may be structured as a fabrication, In which ihe roof is separate from the floor and sides of the trough.

[0142] On the other hand, the convenience Is preferred, of containing ihe water In an actual physical pipe, with its constant-ttiickness cylindrical walls, and Inexpensive, easily available, but assured, Integrity,

[0143] When the treatment-pipe is long, it may be in sections. The sections may be joined by such means as bolted-togeiher flanges, or an enlarged end on one of the sections which slides over the plain end of the adjacent section, etc.

[0144] The trealment apparatus may be arranged with more than one ireatment-plpe. When two or more treatment-pipes are used, they may be arranged In series. An example of an apparatus with two pipes In series, where the two pipes lie both at 1he same level, Is shown in Fig 13.

[0145] Putting Iwo pipes In series can be done where, for example, the lie of ihe land dictates a major change of direction. In Fig 13, a middle chamber 149 Is provided, between the first and second pipes. While this middle chamber can be of some use for collecting setiled-out solids, Its main purpose Is simply to provide a physical structure Into which the ends of ihe treatment-pipes can be mounted and sealed.

[0146] An example of an apparatus with two pipes in series, where the two pipes tie at different levels, Is shown In Fig 14. The water level In the second pipe Is lower than that In the first pipe, due to the presence of fhe welr 150 In the middle chamber 152. Thus, the minlmum-standlng-body of water need not be In one coherently-unitary body, having all 1he same surface level. However, a change in level might give jise to some aeration of the water, which might affect the efficiency of 1he anaerobic reactions, so preferably the minlmum-standlng-body should be a coherent, unitary body of water, unless that Is Impossible due to 1he lie of the land.

[0147] An example of an apparatus with iwo treatment-pipes in parallel Is shown In Fig 15. Ihis can be done, again, when the ground is veiy difficult, and deep excavation must be kept to a minimum. Both pipes use a common inlet chamber 153 and a common outlet chamber 154. Where two (or more) pipes are used, the designer preferably should arrange Ihe Inlet and outlet chambers such that neither one of the pipes receives 22 more flow than the others. Thus, it would not be prefened, in Ihe second aspect of the Invention, to provide two a more treatment-pipes, where the pipes were substantially different as to size, flow-rate, etc. The designer preferably should see to it that the residence time of the water is the same, whichever treatment-pipe the water passes through.

[0148] In the parallel iTeatment-plpes version, ttie parallel-pipes should be fed from a common errtiy-chamber. The parallel-pipes need not all drain Into a common outlet chamber; however, it should be noted ttiat If the parallel pipes have separate outlet ports, the water in all the pipes will drain down to the level of the lowest port; thus, a common outlet chamber, with one single outlet pipe, is also preferred. [0149j it should be noted that the treatment apparatus as described herein Is Intended only for promoting the anaerobic digestion reactions. After having passed through the anaerobic treatment stage, In the treatment-pipe, the water has to be aerated, to promote the needed aerobic treatment reactions. The aerobic treatment station is not Included in the invention, and the Irealment-pipe, as described herein cannot, by definition, be a part of the aerobic treatment station.

[0150] In a case where the treatment apparatus has to accommodate a greater dose rate of incoming sewage, the treatment-pipe length may be increased. But there is no need to increase the other dimensions of the apparatus, Thus, capacity may be Increased, up to a dose-rate of around 15,000 litres per day, simply by Increasing the length of the 45 cm diameter pipe, for Instance to twenty metres, in respect of the minlmum-standlng-body of water, the designer should aim for four-to-one, or greater, In respect of the ratio of the standlng-body-length to the standing-body-width, at more than half the points along the standlng-body-length.

[0151] Below four-to-one, the septic treatment-trough does not have 1he required bng/naiTOw configuration; rather, It would now be characterised as a short/wide container, like a traditional septic tank; end as such it would be prone to the channelling of unwanted pathways. Also, the short/wide container does not have ttie mechanical structural Integrity of a long/narrow trough or pipe. Although four-to-one Is the limit, about slx-to-one should be regarded as the working limit, to be used in practice, as giving a reasonable commercial margin of tolerance. Above about elght-to-one, diminishing returns can be expected, l.e the freedom from unwanted channelling Is almost completely assured at about eight-to-one. If more volume is required, tough, if Is preferred to add volume by way of extra length, rather than extra width, though the designer should take care that the water does not travel along the treatment-pipe at too high a velocity.

[0152] As described, the Invention Is particularly applicable for use In domestic Installations, either for one house, of for a small number of houses that share wastewater 1rea1ment, or for small institutional installations, having a dose rate up to about 15,000 Wres per day. In these installations, the septic treatment Is followed by the usual aerobic trealment, and Ihen the water is infiltrated into the ground, at or close to the treatment stations], The water is not piped away (or not piped for any great distance), either before or after passing through the anaerobic and aerobic treatment station(s). In these cases, apart from the plumbing pipes in Ihe house, ihe treatment-pipe itself comprises almost the only length of pipe in Ihe system. However, It is not a limitation of the Invention that the water not be piped away.

[0153] For a one-bedroom house (750 litres per day), a five or six metre run of 45-cm pipe (with suitable end-chambers) would be suitable; so would 1wo five or six metre runs of 30-cm pipe. For a four-bedroom house (2,500 litres per day) nine or ten metres of 60-cm pipe, plus end-chambers, would be suitable. 23

[0154] The Invention Is not so applicable to large installations, e.g Installations that cater fa dozens of domestic homes, or for larger public institutions, or municipal water treatment installations, because there, usually, Ihe savings arising from the minimal excavations, and from the easy assurance of mechanical stability, would be less. This Is not to say that the Invention must be ruled out In respect of large Installations, and Indeed especially ttie parallel-pipe configuration of Fig 15 can lend itself well to large Installations. But rather, the invention especially lends itself to the type of housing development where each house has its own individual water treatment station, or each set of four or five houses.

[0155] Notionally, Ihe dimensions of the apparatus could be reduced, If the dosing were less than 1000 litres per day; but In practice, treatment systems are hardly ever designed for dosing rates of less than 1000 litres per day.

[0156] If the desired average residence time for water passing through the system were one day, the minimum standing volume should be equal to one day's dosage, But the average residence lime should not be set as low as one day, since that would leave too small a margin for variations. Rather, fhe designer should provide that the mlnlmum-standing-body of water has a volume of preferably one-and-a-half times, and a minimum of one-and-a-quarter times, the average daily dose rate. Thus, where the dose rate Is 3,000 litres per day, the volume of the minlmum-standlng-body preferably should be 4,500 litres. As mentioned, keeping the width and depth of fhe minlmum-standlng-body below one quarter of the standlng-body-length, over at least half of the standlng-body-length, ensures freedom from unwanted pathways, where the treatment-pipe is less than one metre diameter, is suitable for installations dealing with up to about 15,000 litres per day, In lhat differences In residence time can be accommodated by using different lengths of treatment pipe.

[0157] However, for Installations that deal with more than about 15,000 litres per day, the diameter of the Ireafment pipe should be increased beyond the cne melre, because at that large flow rate, a one-metre pipe would be too narrow. In that the water would be flowing along the pipe at too high a velocity. Therefore, for large flow rates, the diameter of the pipe should be increased to a dimension that enables the water, again, to move only veiy slowly.

[0158] As mentioned, the apparatus should be engineered such lhat the volume of the minimum-standing body is 1'/« to l Vz times the average dally dosing rate. If the designer specifies a smaller volume than that, there may not be enough margin to cater for the inevitable variations in usage. If the designer specifies a greater volume, the system may be utilising the available space In an Inefficient manner. It may be noted that the cost of returning later to Increase the capaclly of a too-small treatment-pipe system is considerably less 1han the cost of returning later to Increase the capacity of a too-small concrete tank system. So, with a concrete tank, the prudent designer makes sure to over-engineer the system; but with the treatment-pipe, the designer can leave less of a margin.

[0159] It should be understood that the treatment-pipe of the Invention Is a deliberately engineered containment structure. It might be considered lhat, sometimes, a treatment-pipe system, like that described herein, might have arisen accidentally, for example when a sewage pipe became (partially) blocked, causing water to be backed up, and the backed-up pool of water might correspond to the mlnlmum-standing-body of water. Indeed, the water in such a pool might undergo some anaerobic treatment. The treatment-pipe (or treatment-trough) of the invention lies in the engineered structure that sets the minimum-standing-body of water, as described; the invention does not lie In the body of water Itseff. 24

[0160] Where the wastewater Is fairly clear of suspended solids, for Instance where Ihe treatment-pipe station receives water that has passed through a pre-treatment station, the treatment-pipe can contain a filter medium. The purpose of the fitter medium is to encourage attached microbial growth and to enhance Ireafment. The medium should have good permeability and porosity, while maximizing surface area. A mat of thin plastic strips, for example, is very suitable. Preferably, the medium should be removable from one end of the treatment-pipe, for occasional seivlcing. The medium must be made from a non-biodegradable material that will attract microbes, such as polyethylene, polyurethane, rock wool; but not material that will absorb water and weaken, like nylonj nor repel microbes, like styrene-type. (0161] In connection with the septic treatment-pipe, an alternative to placing the treatment pipe in a predominantly horizontal configuration, as depicted herein, is to align the treatment pipe vertically, or nearly vertically. The treatment-pipe can be In Iwo sections, one conveying the water downwards, followed by another which conveys the water-back up. This arrangement can be made to perform efficiently, and be economical, If the lie of the land requires It. (0162} In a preferred option wastewater is Ireated first in a septic treatment pipe, as described herein, and then passes to a second treatment pipe, containing the described treatment material. Thus the wastewater is Seated both anaerobicaily and aerobically In the respective treatment pipes. received @ IPONZ 22 Dec 2008 •• 25 -

Claims (2)

1. CLAIMS; i. Apparatus for treating wastewater, wherein; the apparatus -includes a container, having an inlet port For receiving wastewater to be treated and an outlet port; the container has-left, and right side-walls and a floor; the left and right side-walls of the container have respective inwards-facing surfaces,, which define a hollow interior of the container, between which the wastewater Is contained; the container includes a treatment-trough, which is of a long/narrow configuration; the treatment-trough Is a component of the container, and is so arranged that wastewater, in passing from the Inlet port to the outlet port of the container, passes along and through the treatment-trough; portions of the left and right side-walls of the container iie in the treatment-trough, and comprise left and right trough-side-walls; the trough-side-wails' confine the water toeing treated in the treatment-trough, and the apparatus is so configured that water, having once entered the treatment-trough, is constrained, by the trough-side-wails, to pass lengthwise along the treatment-trough, and to remain between the trough-;sfde-wails> to the outlet port; a portion of the floor of the container lies in the treatment-trough, and comprises the trough-floor; in a cross-section taken longitudinally along the treatment-trough, being a cross-section taken at the full depth of the trough-floor, a iongitudinal-trough-fioor-line is the longitudinal line that most closely follows the trough-floor, fn that cross-section; an inlet-point and an outlet-point are points that lie within the container, and are the points on the lonyitudinahtrough-flooHlne, or on extensions of the iongitudlnai-trougli-fSoor-iine, which are closest, respectively, to the inlet port and the outlet port of the container; the length of the longitudinai-trou^h-floor-line between the Inlet-point and the outlet-point is termed the container-length; received @ IPONZ 22 Dec 2008 - 26 - at each point along the container, the container has a respective container-width, being the width between the container-side-waiis at that point; at least some of the points along the length of the container comprise also points-?' of the treatment-trough, being those points in respect of which the; container-width at the point lis less than 1/4 of the container-length; the treatment-trough comprises the aggregate of all the points-?; the apparatus Includes a body of treatment material, which:- (a) Is porous and permeable to the passage of water therethrough, and is capable of supporting vigorous microbe colonies; (b) resides in the treatment-trough, and makes tight contact with the trough-floor, and -makes tight contact with at least a bottom portion of the trough-side-wails, In such manner as to ensure that water, in passing through the treatment-trough, cannot .by-pass the treatment material; wastewater being treated in the apparatus moves along respective paths,, in passing from. Inlet to outlet, through the body of treatment-material; in respect of each of the respective paths, the water traverses through, and In contact with, the treatment-materia I., for respective treatment-lengths, being the longitudinally-projected total length of the contact of the water with the treatment-material; the shortest one of the treatment-lengths is at least two metres in length, whereby a drop of water, in passing from inlet port to outlet port of the container, traverses a longitudinal distance, in contact with the body of treatment-material, of at least two metres; the wastewater is water contaminated with carbonaceous BOD,, and the arrangement of the apparatus is such: - that the body of treatment material: does not completely fill the treatment-trough, but. an air-passage exists, running above the body of treatment material in the trough, and so arranged that water residing in the pores of the treatment material is exposed to air in the air-passage; received @ IPONZ 22 Dec 2008 • 27 - - that the air-passage is sufficiently open to the atmosphere as to enable substantial aerobic microbiological breakdown reactions of the SOD in the water residing: in the pores of the treatment material.
2. 2, Apparatus of claim 1, wherein the floor of the trough is predominantly horizontal; and in the said cross-section taken longitudinaiiy along the treatment-trough, being a cross-section taken lengthwise at the full depth of the trough-floor, the iongltudsnahtrough-fioor-line, being the. line that most closely follows the trough-floor, is horizontal, 3. Apparatus of claim 1, wherein: a point aiongthe length of the container comprises a point-T of the treatment-trough only if the container-width at the point, being less than 1/4 of the container-lengthy also is less than about 100 cm; the container Is characterised in that any and every point-along the length of the container in respect of which the container-width at that point is greater than 1/4 of the container-length, is not a point-T of the treatment-trough, 4> Apparatus of claim 1, wherein: the said treatment-trough is the only treatment-trough included in the container, in that the container is so arranged that there is no pathway that wastewater, having entered through; the inlet port, could take, which does not pass through the one said treatment-trough; and the shortest one of the treatment-lengths of the one single treatment-trough is at least three metres. 5. Apparatus of claim 1, wherein the container includes two or mors treatment-troughs, arranged in series, so that the wastewater passes from one to another. 6. Apparatus for treating wastewater, wherein: received @ IPONZ 22 Dec 2008 the apparatus includes a treatment trough, having an entry port for receiving water to: be treated* and an. exit port; the trough has left and right trough-side-walls, and a frough-rloor; the trough-side-walls ;ar$d trough-floor confine the water being treated, and constrain the water, having been received in the entry port, to pass iongitudinaliy along the trough to. the exit pert; the apparatus includes a body of treatment material, which: - (a) is porous and permeable to the passage of water therethrough, and is capable of supporting vigorous microbe colonies;. (b) fits in the trough, between the left and right trough-side-waiSs, and rests in contact with the trough-floor; the structure and arrangement of the apparatus is such that:- •• water undergoing treatment occupies the pores of the treatment material; - a trough-length of the trough comprises the shortest length of the trough-floor, as measured on a line from the entry port to the exit post., that is both (a) wetted by the water being treated, and (b) in contact with the treatment material; - at points along the trough-length, the left and right trough-side-walls serves to confine the water undergoing treatment within the treatment-material to respective trough-widths,, each respective trough-width being the distance apart of the 'trough-side-walls at the respective point; - the trough is of a tong/narrow configuration. In that the ratio of the trough-length to the trough-width is 3:1 or more, over at least eighty percent of the trough-length; the wastewater ;$ water contaminated with carbonaceous BOD, and the arrangement of the apparatus is such: - that the body of treatment material does not completely fill the treatment-trough, but an air-passage exists, running above the body of treatment material in the trough, and so arranged that water residing in the pores of the treatment materia! is exposed to air in the air-passage; received @ IPONZ 22 Dec 2008 - that the air-passage is sufficiently open to the atmosphere as to enable substantias aerobic microbiological .breakdown reactions of the. SOD in'the water residing in the pores of the treatment material. 7, Apparatus of claim 6, wherein the: structure and arrangement of the apparatus is such that the fine, on the trough-floor, comprising the trough-length is at least approximately horizontal over at least eighty percent of its length; 8, Apparatus of claim ?, wherein: the trough is 'long, in that a drop of water, in passing from entry to exit, along the trough-length, traverses a horizontal distance, through the treatment material, of at least two metres; and the trough is harrow, in that the trough-width is less than about 100 cm, over at least eighty percent of the trough-length; and the trough is of a long/narrow configuration, in that the ratio of the trough-length to the trough-width is S; 1 or more, over at least eighty percent of the trough-length, 9, Apparatus of claim 6, wherein the apparatus includes an entry -chamber, which is so arranged that water entering the trough passes first into the entry-chamber before passing into the entry-port of the trough, 10, Apparatus of claim 6, wherein ■ the apparatus includes a plurality of water-treatment sub-troughs, of which the said trough comprises one; the sub-troughs have respective sub-sides and sub-floors, and respective entry ports and exits ports, and respective sufo-trough-iengths, bssng the respective distances between the entry ports and exit ports; the apparatus includes a single inlet-pipe, through which ail water to be treated by the apparatus is received into the apparatus; the apparatus includes an entry-chamber, common to all the sub-troughs, which is so arranged that water entering the inlet-pipe passes into and received @ IPONZ 22 Dec 2008 - 30 ■■ through the entry-chamber before passing into the .entry-ports of the sub-troughs; the sub-troughs are arranged to conduct water away From the com mo n en try -ch a m b er; the apparatus includes a plurality of sub-bodfes of treatment, material, disposed respectively one to each sub-trough, .of which the said body of treatment material comprises oris; each sub-body of treatment materia!, in Its- respective sub-trough (a) is porous and permeable to the passage of water therethrough, and is capable of supporting vigorous microbe colonies; (b) fits in the sub-trough, between the left and right sub-sides, and rests in contact with the sub-floor; the: structure and arrangement of each sub-trough is such that;- - a sub-trough-length of the sub-trough is the shortest length of the sub-floor, as measured on a line from the entry port to fhe-exit port, that is both (a) wetted by the water being treated, and fb) In contact with the sub-body of treatment material; - water undergoing treatment, upon being received at the entry port of the sub-trough, 'travels' longitudinally along the sub-trough to the exit port of the sub-trough; - at points along the sub-trough-length,, the structure of the sub-trough serves to confine the water undergoing treatment to respective sub-trough-widths; - the sub-trough is of a long/narrow configuration. In that the ratio, of the sub-trough-length to the sub-trough-width is 3:1 or more, over at feast eighty percent of the sub-trough-length. 11. Apparatus of claim 10, wherein, in respect of each of the sub-troughs: the sub-trough is long,, in that the sub-trough-length is at least two metres; received @ IPONZ 22 Dec 2008 the sub-trough is narrow, In that the structure of the sides and floor of the sub-trough is such as to confine fhe sub-trough-width, to less than about. 50 em, over at least eighty percent of the sub-trough-length,. 1:2i Apparatus of claim 10, wherein the arrangement of the sub-troughs is such that, between fhe respective entry and exit ports thereof, there is no communication whereby water could pass between adjacent sub-troughs. 13. Apparatus of claim 1.0, wherein the sub-troughs are formed as components of a corrugated sheet, of impermeable material, and the corrugations form the sub-troughs, 14, Apparatus: of ;elaim 6, wherein the arrangement of the apparatus Is such: - as to provide an open passage along the length of the treatment material In the trough; - that the open passage is above the body of treatment material, whereby water cannot enter the passage except on an overflow basis; - that the air passage is continuous, and runs all' along the length of the body of treatment material, and is open to the atmosphere. 15. Apparatus of claim 6, wherein the apparatus includes structure for maintaining water in the trough at a volume at or above a minimum-volume, whereby the trough, during water treatment, contains never less than the said minimum-volume of water. 16, Apparatus of claim 15, whereinj the treatment; material is of an absorbent nature, having a capacity for holding water by capillary action; the body of treatment materia: is so disposed in the trough that the minimum-volume resides in three water-layers of the body of the treatment material, being:- - a saturated-layer, in which the pores are full of water; received @ IPONZ 22 Dec 2008 - a wet-layer, in which the pores are more than half full of water; and - 3 moist-layer ;m which the pores contain: water but are less than half full; the trough-floor and trough-sides confine the water-layers to a width overall of less than 100 cm; the minimum-volume is the aggregate of ail water that is present in ail three of fhe water-layers; the apparatus is so arranged that the body of treatment material also includes a dry-layer, in which the pores contain no water, and which surmounts; the moist-layer, 1?. Apparatus of claim 16, wherein the exit-port is at floor level, whereby.- but for the absorbency and capillarity of the body of treatment material, the minimum-volume would be zero, 18, Apparatus of claim 16, wherein: the exit-port is so structured as to provide a weir, which defines a weir-level, whereby a beiow-weir level of water upstream of the exit-port, and below the weir-level, is retained in the trough; the absorbency arid capillarity of the body of treatment material provide that an above-weir portion of the saturated-layer resides in the body of treatment material, above the weir-level: the beiow-weir portion of the body Is included in the saturated-layer; the remainder of the body of treatment materia!" lies above the weir-level, and includes the wet-layer, the moist-layer, and the dry-layer, 19, Apparatus of claim 16, wherein the body of treatment material is so dimensioned and configured, in relation to the floor and sides of the trough, that a drop of water, in passing along the shortest, pathway a drop of water couid take through any of the saturated * wet, and moist layers, permeates through at least two metres of treatment material. received @ IPONZ 22 Dec 2008 20, Apparatus of claim 16, wherein the trough-$k1e--wali;s confine and guide the flow of water along the trough, end are impermeable, and seated, to the extent that water, once having entered the:entry port of the trough, cannot pass outside the trough, except through the exit port thereof, 21, Apparatus of claim 15, wherein* the exit-port is so structured as to provide a weir, which defines a weir-level,- and water Immediately upstream of the exit-port, and below the weir-level, is retained in the trough; and the. weir comprises the structure for maintaining the volume of water in the trough at a volume at or above the mini mum-volume, 22, Apparatus of claim 15.< wherein: the apparatus Includes an operable recirculating-sysfcem, which is effective, when operated, to collect water from the exit port, and to transfer the co-Elected water back into the trough, through the entry-port; and and the recirculating -system comprises the structure for maintaining the volume of water In the trough at ® volume at or above a minlrnum-voiurne, 23, Apparatus of claim 6, wherein the trough floor is all on one level, and is at feast approximately horizontal. 24, Apparatus of claim 6, wherein the trough floor is on two levels, both of which are approximately horizontal,, and which are separated by an Intermediate weir. 25, Apparatus of claim 6, wherein the treatment material is one of: (a) open-ceil foam, having a porosity between ninety and ninety-six percent; (b) spun molten silicate; (c) sand or gravel having a measurable degree of ab-sorb-ency;: received @ IPONZ 22 Dec 2008 •• 34 - (c!) plastic artificial turf, and the body of treatment material comprises the turf wrapped into a spiral that is a light fit inside the pipe, 26; Apparatus of claim 6, in combination with a source of wastewater to be treated, wherein the source produces water to be treated at the rate of D1 litres per day, and the minimum-volume is at least twenty percent of 27. Apparatus of claim 6, wherein the treatment trough comprises a treatment-pipe, having a floor, sides, and a roof, of the treatment-pipe, forming a complete circumferential enclosure, and being of constant cross-section along its iength, 28. Apparatus of claim 27, wherein: the body of treatment material'is a resilient body of open -cell foam; the body of foam is formed with a cross-sectional configuration complementary to that of the pipe, and of such dimensions as to be a tight fit inside the pipe; except that an upper sector of the body of roam is formed "with a cutout, which comprises the said air-passage. 29. Apparatus of claim 27, in combination with a source of wastewater to be treated,, wherein: the pipe is right cylindrical, and is not more than 30 cm diameter; the source produces water to be treated at a rate of T1. litres per day, where Tl is less than 500 litres; and the length of the pipe, as measured in centimetres, is between % and 2 times Tl. SO. Apparatus of claim 27, in combination with a-source of wastewater to be treated, wherein: PI. the source produces water to be treated at a rate of T2 litres per clay , where T2 is between 500 and 1000 litres; the iength of the pipe, as measured in centimetres, is between Vz and .1. times T2, 31. Apparatus of ciairn 27, in combination with a source of wastewater to be treated, wherein: the pipe is right cylindrical, and is not more than 100 cm diameter; the source produces water to be treated at a rate of 13 litres per day, where 13 is between 1000 and 2000 litres; the length of the pipe, as measured in centimetres, is between: Vs and Vz times T3. 32. Ap p a r atu s of claim 27, vv h e rei n: the apparatus Includes two treatment pipes, arranged in series; each of the two treatment pipes forms a complete circumferential enclosure and Is of constant cross-section along its iength.