Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/28—Treatment of water, waste water, or sewage by sorption
  • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/30—Wastewater or sewage treatment systems using renewable energies
  • Y02W10/33—Wastewater or sewage treatment systems using renewable energies using wind energy

Definitions

• the invention relates to removal of impurities, particularly to a slow sand filter which removes impurity(ies) from raw feed water.
• Slow sand filtration is usually carried out in slow sand filters which provide a well established means of removing impurities from raw feed water. They have however a high capital cost and require extensive land. As mentioned previously, current filters are unable consistently to meet required standards of removal of impurities such as pesticides, trihalomethane precursors, organic solvents and volatile organic compounds which affect taste and odour, such as geosmin and 2-Methylisobomeol. Similar considerations apply to removal of colour, total organic carbon (TOO and assimable organic carbon (AOC).
• TOO total organic carbon
• AOC assimable organic carbon
• a filter for removing impurities from a liquid such as water comprising sand or the like filter medium, and an additive adapted to remove at least pesticides from the liquid.
• the term "pesticides" used herein includes fungicides, herbicides, insecticides and the like.
• the filter may be a slow sand filter for water.
• the additive may comprise activated carbon, particularly in the form of at least one layer of granular activated carbon in the filter. This provides for efficient removal of impurities.
• a lower lave*- of sand of thickness in the range of about 200 to 400mm
• a layer of activate ⁇ carbon of thickness in the range of about 200mm, suitably 25 to 200mm.
• an upper layer of sand of thickness in the range of about 300 to 500mm.
• the lower sand layer may be substantially 300mm thick, the granular activated carbon layer substantially 135mm thick and the upper layer of sand substantially 450mm thick.
• modules of activated carbon particularly for an activated carbon layer thickness of between 25mm - 50mm thickness.
• Each module may be a substantially square module, for example of about lm side.
• the modules may then be laid in a slow sand filter as desired, preferably the module may be a mat. bag or strip with a boundary or casing of a suitable material such as geotextile material.
• a suitable material such as geotextile material.
• the activated carbon may be sandwiched between layers of geotextile material.
• the bags may comprise compartments, each of which holds a desired quantity of activated carbon in a positive, i.e. non-shifting, way.
• the compartments can be formed in any suiiable way, by stitching, moulding or the like.
• bag and contents may be such as to be regeneratable by being placed straight into a regeneration furnace, so that the complete bags can be regenerated, and then reused.
• a slow sand filter may comprise activated carbon as a layer of say 25mm to 50mm thickness, laid or sandwiched between geotextile layers or mats one of which is laid on a (lower) sand layer, the activated carbon is then laid thereon, and an upper (in use) geotextile layer or mat is then laid over the activated carbon, a sand layer then being laid on the upper leotej tile layer.
• the layers of geotextile may overlap, to provide a comprenensive containment for the activated carbon.
• the granular activated carbon may itself be mixed with sand, in suitable predetermined proportions.
• sand panicles being of smaller dimension than the activated carbon granules, tend to "plug” gaps between the activated carbon granules.
• This "plugging” action forces water, in use, in a filter bed, to flow through the adsorbent granular activated carbon.
• the “plugging” also provides fewer voids for the growth of organisms in the filter.
• Each layer of the bed may be levelled relative to a laser datum. This ensures uniform filtering and purification.
• the laser datum may comprise a laser transmitter set to a desired height of an upper surface of a layer and a receiver on a mobile device for levelling the respective layer to that desired surface height.
• a method of providing a filter, comp ⁇ sing providing sand or the like filter medium providing an additive adapted to remove at least pesticides passing in use through the filter and laying the sand/additive to provide the filter.
• the method may preferably comprise providing a slow sand filter.
• the step of providing an additive may comprise providing an additive comprising granular activated carbon.
• the step of providing granular activated carbon may comprise laying that granular activated carbon in at least a layer in the filter.
• the method may include the step of levelling the upper surface of at least the lower sand layer and granuiar activated carbon layer using a laser datum.
• the method may also comprise providing an indicator of a desired level which indicator is monitored by an operator of the mobile device for adjusting levelling means of the device.
• the method may also comprise providing a bridge or gantry extending across the slow sand filter, for levelling and/or laying a layer.
• the method may provide for provision of a boom having an appropriate reach, the boom preferably being mounted on and extendingfrom the side of the filter.
• the method may further comprise providing a motor device adapted to run on a layer of the bed.
• This method step may suitably provide a mobile device having scraper bars of substantially 90° angular configuration.
• the method may comprise iaying the layers in sequential pan surface areas of the total area of the slow sand filter until the whole surface area is provided with a sandwich of sand and granular activated carbon.
• the invention e.xtends to a slow sand filter bed in corporation a filter and method as hereinbefore defined.
• Fig. l is a cross-section through a siow sand filter according to the invention:
• Fig.2 is a schematic perspective view of a method of laying and levelling the slow sand filter of Fig. l;
• Fig.3 is a schematic transverse sectional view of an alternative method of levelling and/or laying the slow sand filter of Fig. l ;
• Fig. 5 is a schematic perspective view of a pa ⁇ icular embodiment of levelling device of Figs. 2, 3 and 4:
• Fig. 6 is a plan view of the levelling device of Fig. 5;
• Fig. 7 is a sectional view on line "B"-"B" of Fig. 6;
• Fig. 8 shows the step of dressing a surface of a layer of sand and a method of laving a slow sand filter according to the invention
• Fig. 9 shows the step of levelling a layer of granular activated carbon
• Fig. 10 is a graphical representation of pesticide removal using a slow sand filter according to the invention, against a control bed which did not have any additional layer.
• a slow sand filter 1 comprising, in the sand 2, an additive 3 in the form of a layer of granular activated carbon operative to remove impurities, at least pesticidal ones, from water (not shown in the filter in the Figs.) passing in use through the slow sand filter to be purified thereby.
• the granular activated carbon is in the form of a single layer 3 in the embodiment of about 135mm (uncompacted) thickness sandwiched between a lower (as viewed and in use) layer 4 of clean sand of substantially 300mm thickness and an upper (as viewed and as in use) layer 5 of clean sand of substantially 450mm thickness.
• the lower layer 4 of clean sand is firstly laid and levelled. It is delivered to the bed of the filter by suitable means such as a series of motor devices such as dumper trucks, or an overhead bridge or gantry 6 to the bed.
• the layer 4 is spread out to the required thickness and with a relatively smooth and level upper surface by a laser datum in the form of a laser transmitter 7 which is set to a required height and a laser receiver 8 which is mounted on a levelling device in the form of a levelling device 9 which has a frame 10 with transverse substantially parallel bars 11 of substantially 90° angular configuration as shown in Figs. 4, 5 and 7. As can be seen (Figs.
• the bars 11 are mounted on the frame 10 such that their lower limbs are inclined at about 20° to the horizontal.
• the laser datum 7, 8 is such that as the device 9 is dragged over the sand 4, to spread and smooth it out, the receiver 3 passes up and down through the laser beam 12 from the transmitter 7, monitors whether it is too high or low and provides a signal to the operator of the gantry 6 or device 9 so that he or she can make appropriate adjustment of the levelling device as it is moved back and fo ⁇ h and up and down (arrow 'X') until the height of the upper surface of the layer 4 is smooth, level, and of the required height, in other words the layer is of the required thickness, any tyre marks being smoothed out where dumpers are used.
• the laser receiver 8 is mounted in one or other of two sockets 9 ' mounted on the frame 10 (Fig.5).
• the layer of granular activated carbon 3 is then iaid on the lower layer of sand, using a similar method.
• the granular activated carbon is delivered to the bed by a series of dumper trucks (not shown) which delivers a pile 13.
• a mobile grader 14 or tractor with the levelling device 9 of Fig.4 (which has a pivotal connection 15 for connection with a tractor raising and lowering mechanism 15') is then brought up and spreads out the granular activated carbon to form the layer 3 of the required thickness using the laser datum 7,8 as before.
• the laser receiver 8 has a direct visual indicator showing the operator 16 in the cab whether the thickness is too great or too little so that he can manoeuvre the levelling device 9 as desired until the required thickness and smoothness is achieved.
• the upper layer 5 of sand is then applied using a similar laser datum method to achieve a desired thickness and smoothness of the upper layer of sand.
• the slow sand sandwich filter of the invention is suitablv laid in sections. suitably half at a time as shown in Figs. 8 and 9.
• the lower layer of clean sand is laid in its entirety.
• half the sandwich is built up as described above.
• the tyre marks of dumpers or the like of the other half are then eradicated from the layer 2 using a bar scraper and smoothing mat arrangement, and then the other half of the sandwich is built up.
• the first application of clean sand of the upper layer 5 is applied relatively gently to the laid layer of granular activated carbon 3 so as not to disrupt the smooth surface or alter the thickness.
• the granular activated carbon is also covered with the upper layer of sand 5 as quickly as possible after laying so that it is protected from dispersion by wind, degradation or attrition by frost, or disturbance or depradation by animals or birds.
• the granuiar activated carbon is also delivered dry to a holding store, usually in tankers, from which it is pumped out to a washing plant to remove fines, the washing medium being water.
• the water drains away, but the carbon remains damp and is laid like this, so helping to avoid dispersion by wind, and also assisting in improving the process of compression of the granules.
• the water to be treated may also be pre-treated with ozone (O j ) which can enhance the life of the granular activated carbon prior to exhaustion.
• O j ozone
• a slow sand filter embodying the invention and as described herein with reference to the drawings will remove individual pesticide levels from surface waters to below 0.1 ug/1 and total pesticide levels to below 0.1 ug/1 for between 12 to 60 months before regeneration of the granular activated carbon falls due.
• a pesticide resistant to ozone such as atrazine can be virtually totally removed using a slow sand filter embodying the invention which is double the removal rate by ozone.
• the top layer of sand 5 is progressively skimmed down by about 2.50cm, and replaced, therefore with a 450mm thickness top layer, 14 skims or cleans will take place before a thickness of about 100mm sand above the granular activated carbon is reached using a mobile "dry” cleaning machine. This thickness is about the minimum thickness before disruption of the carbon layer ensues.
• 14 "cleans" can be effected prior to topping up with new sand or removing the granulated activated carbon layer if exhausted, thereby greatly reducing operating costs.
• Typical slow sand filters as operated by the Applicants are typically rectangular, 80-120m long and 20-35m wide. Within the filter a 0.7-1.0m deep layer of 0.3mm effective size (ES) sand overlies a layer of drainage gravel and an underdrain system constructed from porous concrete.
• ES effective size
• the granular activated carbon sandwich filter followed pre-ozonation, primary rapid gravity filtration with (dual media filter with ferric sulphate dosing) and main ozonation.
• a second pilot siow sand filter constructed without the granular activated carbon but otherwise identical, was operated in parallel as a control.
• the target filtration rate for both filters was 0.3 m/hr.
• Fig. 10 Results of four individual pesticides are shown in Fig. 10, which compares concentrations in the filtrate from the full scale granular a ⁇ ivated carbon sandwich and control beds. To date no pesticides have been detected in the filtrate from the granular a ⁇ ivated carbon sandwich (15,000 bed volumes treated).
• TOC total organic carbon
• the granular activated carbon sandwich has also maintained a high degree of colour removal throughout, dropping only 20% over the period of the trial.
• Conventional granular activated carbon media of effe ⁇ ive size (ES) 0.7mm can be placed as a 25-200mm sandwich layer within conventional slow sand filter media, ES 0.3mm, with no detriment to normal filter operation or water quality.

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• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Water Treatment By Sorption (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Filtration Of Liquid (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Control And Other Processes For Unpacking Of Materials (AREA)
• Processing Of Solid Wastes (AREA)
• Physical Water Treatments (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Filtering Materials (AREA)

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Citations (4)

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• 1993
  • 1993-12-08 CA CA002151367A patent/CA2151367A1/en not_active Abandoned
  • 1993-12-08 GB GB9325163A patent/GB2273251B/en not_active Expired - Fee Related
  • 1993-12-08 EP EP94902043A patent/EP0673276B2/en not_active Expired - Lifetime
  • 1993-12-08 DE DE69308886T patent/DE69308886T3/de not_active Expired - Fee Related
  • 1993-12-08 CZ CZ19951498A patent/CZ286279B6/cs not_active IP Right Cessation
  • 1993-12-08 RO RO95-01117A patent/RO113615B1/ro unknown
  • 1993-12-08 HU HU9501677A patent/HU214803B/hu not_active IP Right Cessation
  • 1993-12-08 RU RU95114445A patent/RU2131287C1/ru active
  • 1993-12-08 JP JP51393394A patent/JP3519404B2/ja not_active Expired - Fee Related
  • 1993-12-08 WO PCT/GB1993/002511 patent/WO1994013381A1/en active IP Right Grant
  • 1993-12-08 PL PL93309297A patent/PL172949B1/pl unknown
  • 1993-12-08 AU AU56556/94A patent/AU5655694A/en not_active Abandoned
  • 1993-12-08 AT AT94902043T patent/ATE149862T1/de not_active IP Right Cessation
  • 1993-12-10 IN IN781CA1993 patent/IN181283B/en unknown
• 1995
  • 1995-06-08 NO NO952267A patent/NO309929B1/no not_active IP Right Cessation
  • 1995-06-09 FI FI952841A patent/FI952841A/fi unknown

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