ITRM20110340A1 - PURIFICATION SYSTEM FOR CIVIL AND INDUSTRIAL WASTEWATER WITH VERTICAL REACTOR. - Google Patents

Description

Vertical reactor civil and industrial wastewater purification plant

The present invention relates to a civil and industrial wastewater purification plant, whose function is to make the water resulting from the treatment compliant with the provisions of the regulations in force.

More particularly, the invention relates to civil and industrial wastewater purification plants of the vertical reactor type.

In the field of equipment that allows the treatment of civil and industrial waste water, excellent results have been obtained through the introduction of the so-called deep well technology.

Examples of such apparatuses or similar methodologies are described in patents DE9304698, EP0552134 and WO / 2004/035488 and EP2089329.

According to this type of technology, the purification of waste water takes place in a vertical reactor completely underground and covered. The more traditional deep-well purification plants, with vertical reactors having a diameter of 5-8m, however, present enormous construction and waterproofing problems, with consequent serious risks for the aquifers, which could be polluted. These problems have severely limited its diffusion, even though these plants have important advantages in terms of size and effectiveness with respect to traditional purification plants.

According to the modifications proposed in WO / 2004/035488, the dimensions of the reactors can be reduced up to 50cm in diameter, allowing excellent waterproofing, with a depth of 40 - 70m, making the biological reaction to activated sludge particularly effective thanks to the high pressure. present at such depths due to the overlying hydraulic head. The measures involved make it possible to excavate the reactor housing with a normal drill and to perfectly waterproof the work with a steel jacket and a HDPE, as well as concrete and gravel.

Such a reduction in the reactor diameter is due in particular to an innovative air distribution system. In fact, after the primary treatments, the water to be purified passes through an equalization tank and, subsequently, enters the reactor, inside which compressed air is distributed which, operating at pressures from 2 to 8 atmospheres, forms fluid beds of activated sludge whose effectiveness is particularly high. After having completed the descent to the bottom of the reactor, and having therefore come into contact with the air and the fluid beds, the water returns to the surface by means of the dragging action exerted by an air pump (air lift) and then passes through a series of phases (energy dissipation, flotation and sedimentation) completing the purification process.

The purification plants that make use of this technology have both environmental and economic advantages. In fact, the footprint of this type of plant is much smaller (30-50% less) than an equivalent traditional activated sludge system and is completely underground and covered. Furthermore, the production of biological sludge (smelly and expensive to eliminate) is reduced by 50-80%. The initial cost of these plants is lower than that of traditional activated sludge plants, above all thanks to the lower electrical power required and the very reduced concrete products. In addition, the running cost is at least 30% lower: less electricity, less maintenance and less sludge, however already stabilized.

The installations carried out following the teachings of WO / 2004/035488 have also highlighted some problems, such as the fact that, in plants with potential for 20000-30000 inhabitants, in which rainwater and industrial wastewater are made to flow, particularly harmful to the development and maintenance of the bacterial flora responsible for purification, it is very problematic to regulate the recirculation of the sludge floated in the heat sink to the homogenization balancing tank, this operation having to be carried out several times a day and requiring a long time, with the consequent use of personnel engaged in simple routine operations.

A second problem highlighted by this type of systems is that for significant flow rates, the float flows irregularly from bottom to top, hindering the transfer of solids from the heat sink to the balancing.

Furthermore, the great variability of the wastewater flowing into the plants entails difficulties in regulating the quantity of air introduced into the vertical reactor, as the activated sludge beds proposed for the abatement of biodegradable substances and suspended solids change consistency and location at the same time. inside the reactor itself.

Furthermore, even if the deep well system has proved particularly efficient in reducing the Biological Oxygen Demand (hereinafter BOD), i.e. when the pollutants are rich in carbon C, the reduction of nitrogen N required a study. in depth in which it emerged that the bacteria (nitosomonas and nitrobacter) in charge of this purpose do not withstand the stress due to the rapid decrease in pressure that occurs in the reactor air lift. For the treatment of wastewater with inlet BOD concentrations even higher than 10000mg / l, it was found that it was difficult to obtain an exchange of oxygen between the introduced air and the sewage, which entails a difficulty in the growth of the activated sludge and a bad quality of the same, with consequent unsatisfactory results.

According to EP2089329 it is proposed to overcome these limits by realizing a purification plant for civil and industrial waste water with a vertical reactor, of the type comprising a sewage lifting station; a fine screening with a rotating drum; tanks for desanding, oil removal, denitrification; a nitrification, biological oxidation, homogenization tank; oxygen air diffusers; a vertical reactor; an air lift designed to recirculate the suspended sludge and sewage by catching it at a predefined depth in said reactor; an air pump inside said reactor; one or more air and gaseous oxygen diffusers inside said reactor positioned at various levels; one or more high-pressure compressors that feed said one or more air diffusers; one or more pipes suitable for taking mixture samples at different depths; a flotation tank; one or more adjustable openings with motorized and manual gates for the recirculation of the flotation formed inside and outside the flotator; a plurality of lamellar packs in the sedimentation tank; a series of hoppers in the sedimentation tank; a submersible pump for sludge recirculation; a well to collect the floating mud; and a recirculation pump of the sludge in oxidation to denitrification or dehydration; and in particular by equipping said purification plant with a rising duct for communicating vessels, connected to a recycle sludge pit, and able to recirculate the suspended sludge and sewage by catching it at a depth lower than the maximum depth of said air lift in said reactor, suspended bodies suitable to allow the increase of the attached flora and means for introducing oxygen (02) into said reactor in the case of sewage particularly rich in carbon (C) and / or with BOD concentrations higher than 500- 1000 ppm.

The plants built following the teachings of EP2089329 have demonstrated a remarkable ability to treat even wastewater with a very high level of BOD, producing a very small quantity of sludge.

Experience, in fact, has shown that the action of the air lifts, involving the rapid passage from a pressure of about 7atm, corresponding to a depth of 60m, to the atmospheric pressure present in the flotation tank, causes a physical lysis of the bacteria, which is instrumental both in providing (by recycling) the feeding of incoming bacteria, and in reducing the vitality of the waste sludge, making it, in effect, more digested and reducing its olfactory impact.

The purpose of the present invention is therefore that of realizing a purification plant for civil and industrial wastewater with a vertical reactor that allows to overcome the limits of the solutions according to the known technology by making the most of the lysis phenomena of bacteria that occur inside of the reactor.

A further object of the invention is that said purification plant can be realized with substantially contained costs, both as regards the production costs and as regards the management costs.

Not least object of the invention is that of realizing a purification plant for civil and industrial waste water with a vertical reactor which is substantially simple, safe and reliable.

Therefore, the specific object of the present invention is a vertical reactor civil and industrial wastewater purification plant, of the type comprising a section for the elimination of coarse solids present in the water to be treated, a denitrification section, an oxidation / homogenization tank, on the bottom of which a vertical reactor is arranged, equipped with a plurality of air and oxygen diffusers and at least one air lift that takes the water from the reactor and conveys it to a flotator and subsequently to a battery of lamellar packs and from this to a disinfection and discharge section, which comprises means for heating the water at the bottom of the vertical reactor and means for detecting the temperature at the bottom of the vertical reactor, which control said means for heating the water.

Further characteristics of the vertical reactor civil and industrial wastewater purification plant according to the present invention are defined in claims 2-10.

The present invention will now be described for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the figures of the attached drawings, in which: - Figure 1 shows a sectional view of a waste water purification plant civil and industrial according to the present invention;

- figure 2 shows a sectional view of the vertical reactor of the purification plant of figure 1, and in particular of the anti-seismic flange with which it is equipped;

Figure 3 shows a sectional view of a further embodiment of the vertical reactor of the purification plant of Figure 1; And

Figure 4 shows a plan view of the vertical reactor of Figure 3.

Referring preliminarily to Figure 1, the sewage coming from a pipe 10 reaches a lifting station 11 in which the electric pumps 12 are installed which send it through the pipes 13 to a fine screening apparatus 14 with a rotating drum, whose function It is to prevent any coarse solid from reaching the subsequent phases and to create possible blockages and consequent stops of the system. The removed material, after any compaction, is sent to a bin (not shown). The sewage coming out of the fine screening apparatus 14 with rotating drum is instead sent, through the pipe 15, to a desanding and oil removal tank 16, and then reaches, through the pipe 17, the biological denitrification tank 18, equipped with an agitator 51 and subsequently, through the pipe 19, to an oxidation / homogenization tank 20.

In the oxidation / homogenization tank 20 there are a series of dependent air and oxygen diffusers 46 and others, which vary according to the type of sewage to be treated, fed by low-head blowers. The introduction of air and oxygen causes the mixing of the mass, its chemical and biological oxidation and the dissolution of any other additive gases. On the surface of the oxidation / homogenization tank 20 there are bodies with adherent mass 50 to increase the contact area between wastewater and sludge.

In the oxidation / homogenization tank 20 there are also a series of electronic detectors 21 connected to indicator instruments which automatically adjust the operating times in the blowers by means of timers and a series of valves. In the bottom of the oxidation / homogenization tank 20, in a variable planimetric position according to the characteristics of the sewage to be treated, there is the vertical reactor 22, in which the sewage arrives by gravity, with motion from top to bottom along the entire length of the reactor itself.

Inside the vertical reactor 22 there is an air pump connected by a vertical pipe (air lift 23) and a series of air or gaseous oxygen diffusers positioned at various levels and fed by high head compressors.

A second air lift 24 is positioned in the reactor in support of the first, at an intermediate depth.

The air lifts send the water-gas-mud mixture into a flotator 25 equipped with adjustable motorized bulkheads for carrying out the recirculation of the flotate formed both inside the flotator and in the area outside it.

In the tank 26 of the flotator, separated by special adjustable motorized bulkheads, the final sedimentation of the system is made, served by lamellar packs 27, suitably sized and studied, and by a series of hoppers (not shown), which facilitate the outflow of the mud in the recovery area for subsequent recirculation with a submersible electric pump. The recirculation of the float takes place by gravity.

The resulting water, after passing through the lamellar packs, is sent to a disinfection tank 28 and subsequently sent, through the pipe 29, to drain.

The system that has the operating characteristics described above has the modifications which have already been mentioned at least in part and which are specified below.

In particular, the solution according to the present invention proposes to improve the ability of this type of plant to treat wastewater with a very high level of BOD and to produce a negligible quantity of sludge by making the most of the lysis phenomena of bacteria that occur at the inside the reactor.

Experience has in fact shown that the rapid transition from a pressure of about 7atm, corresponding to a depth of 60 meters at the bottom of the vertical reactor, to the atmospheric pressure present in the flotator 25 causes a physical lysis of the bacteria, which is instrumental both in the provide (by recycling) feeding to the incoming bacteria, both to reduce the vitality of the waste sludge, making it, to all intents and purposes, more digested and reducing its olfactory impact.

According to the present invention, a thermal lysis is added to this physical lysis: it has in fact been shown that, at temperatures above 50 ° C, most bacteria undergo this phenomenon. The temperature, however, must not rise above 60 ° C, a level at which the reaction kinetics substantially decreases.

According to the invention, it is proposed to achieve this purpose by increasing the temperature at the bottom of the reactor.

This temperature increase can be obtained in one of the following two ways, depending on the availability or not of usable heat sources:

- feeding pure oxygen to the bottom of the reactor; - providing heat at the bottom of the reactor.

To feed pure oxygen to the bottom of the reactor (however necessary in a very small quantity), a feeding tube is provided at the bottom of the reactor. Thanks to the contribution of the oxygen added at the bottom of the reactor, the exothermic chemical reaction of oxygenation, which in itself is already prevalent in this section of the apparatus, is enhanced until the desired temperature level is obtained.

If there is availability of hot water, steam or, in general, thermal energy (for example by virtue of the presence of a biomass transformation system in the same plant where the purification plant of the invention is installed), Ã On the other hand, it is possible and convenient (as shown in Figure 1) to use this heat by installing a heating system 30 which, through insulated pipes 31, transfers these heat sources to a coil 32 at the bottom of the vertical reactor 22.

In both of the aforementioned cases, it is necessary to equip the system with a thermal sensor placed at the bottom of the vertical reactor, which disconnects the heating system in the event that the temperature reaches a threshold level (58 ° C seems to correspond to the best result).

In support of the specific solution of the invention, the vertical reactor civil and industrial wastewater purification system of the present invention provides further expedients with the aim of introducing anti-seismic precautions and obtaining an increase in the maximum dimensions of the vertical reactor.

The recent seismic phenomena, in fact, have created an instinctive concern for systems, in general, with underground activity.

In order to overcome this type of concern, according to the present invention a movement system (as shown in figure 1 and more particularly in figure 2) is proposed, optionally and to complete the solution already described, which allows a certain displacement in the horizontal direction of the reactor 22 with respect to its usual position, without generating shear stresses.

The actual vertical reactor 22, made with polymeric materials, such as for example HDPE (high density polyethylene), and surrounded by an external steel jacket 33, will therefore be equipped with a handling system 34, consisting of rollers 35 or by spheres, arranged on the four sides of the vertical reactor 22, on which rests a flange 36, coupled to the end of the vertical reactor 22. The rollers 35 or the spheres in turn rest on a plate 37, which in turn rests on the bottom 38 of the oxidation / homogenization tank 20, and which acts as a reinforcement of the bottom 38 itself. Between the reactor 22 and the outer jacket 33 there is an interspace 39. According to the known art, this interspace 39 is isolated from the oxidation / homogenization tank 20 due to the fact that the flange 36 is welded to the outer jacket 33 In the case of the solution of the invention, such welding is not feasible because it would prevent the reactor 22 from moving. To ensure the insulation of the interspace 39, according to the present invention, sealing gaskets 40 are provided, arranged between the flange 36 and plate 37, sufficiently elastic not to impede the displacements of the reactor 22.

Furthermore, since the horizontal movements linked to possible seismic movements would still be equal to a few centimeters, the space between the outer jacket 33 and the reactor 22 is conveniently increased from 10cm of the known solutions (5cm per side) up to 20cm, so such as to create a movement space in which the outer jacket 33 can flex and also deform, without causing shear stresses on the reactor 22 which guarantees the hydraulic seal.

As regards the increase in the dimensions of the reactor, the maximum dimensions of the vertical reactors, to which the embodiments according to the known art refer, are equal to about 900mm in diameter. This limit is imposed by the need to prevent bacterial beds from losing stability by increasing their size. However, this limitation leads to an area of criticality (also economic) of this type of plant in the range between 7000 - 11000 inhabitants and beyond, cases for which the need to switch from one to two reactors arises.

The solution according to the present invention allows to increase the useful diameter of the reactor 22 up to 1300mm (corresponding to an external jacket 33 equal to 1500mm), thus giving a range of manufacturing diameters from 400 to 1300mm.

With reference to Figures 3 and 4, according to the present invention, the potential destabilization of bacterial beds is eliminated by introducing vertical bulkheads 41, integral with the two air lifts 23, 24, with very wide mesh support grids 45, in the section of reactor 22 where bacterial beds are formed (typically ranging from 10 to 30 meters deep).

This depth can be predetermined, for each plant, on the basis of the amount of air used, the BOD, the amount of suspended solids, the inlet and reactor operating temperature and other parameters.

The present invention has been described by way of illustration, but not of limitation, according to its preferred embodiments, but it is understood that variations and / or modifications may be made by those skilled in the art without thereby departing from the relative scope of protection. as defined by the appended claims.

Claims (8)

CLAIMS 1) Civil and industrial wastewater purification plant with vertical reactor, of the type comprising, in succession following the path of the water to be purified: a screening section (14) for the elimination of coarse solids present in the water to be treated, a biological denitrification section (18), a tank inside which there are a plurality of air and oxygen diffusers for oxidation / homogenization (20) on the bottom of which there is a vertical reactor (22), equipped with a plurality of air and oxygen diffusers and an air lift (23) which takes the water from the bottom of the vertical reactor (22) and conveys it to a flotator (25) and subsequently to a battery of lamellar packs and from this to a disinfection section (28) and discharge, characterized in that it comprises means for heating (30, 31, 32) of the water at the bottom of the vertical reactor (22) and means for detecting the temperature at the bottom of the reactor v erticale (22), connected to means that control said water heating means (30, 31, 32), as well as a second air lift that takes the water from the vertical reactor (22) at an intermediate level and conveys it to said flotator (25) or to a different flotator and from this to said battery of lamellar packs and subsequently to said disinfection section (28) and discharge. 2) Vertical reactor civil and industrial wastewater purification plant according to claim 1, characterized in that said heating means (30, 31, 32) of the water at the bottom of the vertical reactor (22) comprise feeding means at the bottom to the vertical reactor (22) of pure oxygen, as a reactant in the exothermic reaction of oxygenation of the waters. 3) Vertical reactor civil and industrial wastewater purification plant according to claim 1 or 2, characterized by the fact that said heating means (30, 31, 32) of the water at the bottom of the vertical reactor (22) comprise a system of heating (30) which, through insulated pipes (31), sends a hot fluid to a coil (32) at the bottom of said vertical reactor (22). 4) Vertical reactor civil and industrial wastewater purification plant according to any one of the preceding claims, characterized by the fact that it comprises a movement system (34) of said vertical reactor (22) which allows the free movement of the same in the horizontal direction inside an external containment jacket (33). 5) Vertical reactor civil and industrial wastewater purification plant according to claim 4, characterized in that said movement system of said vertical reactor (22) comprises a plurality of rollers (35) or spheres, arranged on the sides of the reactor vertical (22), on which rests a flange (36), coupled to the end of the vertical reactor (22), and sealing gaskets (40), arranged between the flange (36) and the plate (37). 6) Vertical reactor civil and industrial wastewater purification plant according to any one of the preceding claims, characterized in that said vertical reactor (22) is equipped with at least one vertical bulkhead (41). 7) Vertical reactor civil and industrial wastewater purification plant according to claim 6, characterized in that said at least one vertical bulkhead (41) is supported by support grids (45) with a very large mesh. 8) Vertical reactor civil and industrial wastewater purification plant according to claim 6 or 7, characterized by the fact that said at least one vertical bulkhead (41) is located in the section of the vertical reactor (22) in which the beds are formed bacterial.