Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/32—Biological treatment of water, waste water, or sewage characterised by the animals or plants used, e.g. algae
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/001—Runoff or storm water

Definitions

• the invention relates to a process for the treatment of effluents from communities equipped with a sewerage network capable of collecting rainwater or infiltration water, so that the effluent flow rates to be treated by a water treatment plant may vary greatly between a period of dry weather and a period of rain.
• Examples of extensive wastewater treatment plants are provided by FR 2 782 508 and FR 2 858 316.
• the jolts of flow, caused by the rains, therefore lead to size the facilities on major water flows to be treated , which are only rarely reached in normal service.
• a storage of the polluted water surplus, caused by a storm or heavy rain, can be considered in a basin but it is advisable to treat the excess in less than 24 hours to limit the fermentation, source of bad smells and degradations of the quality of treatment at the level of purification.
• the purpose of the invention is, above all, to provide a process for treating effluents from communities which makes it possible to "smooth" the flow peaks due to precipitation, particularly storms, and to obtain at the outlet of the purification plant a quality relatively constant treatment. It is desirable that the footprint of the facilities be as low as possible.
• the effluent treatment process of communities is characterized in that: - a purification plant is provided with capacity adapted essentially to the flow of effluents in dry weather;
• a filter bed planted with plants is planned upstream of the purification station and is capable of storing a polluted water surplus without fermentation, and pre - purifying;
• Planted plants are, advantageously, reeds.
• the stored water is evacuated, in particular by pumping, over a week or more, which causes a minimum impact on the sizing of the station downstream treatment plant.
• This treatment plant can be sized for a flow of effluents in dry weather.
• the storage time of the waste water in the filter bed planted is greater than several days, no fermentation is observed resulting in release of odor pollution. Aerated by plants, especially reeds, and their rhizomes, the waste water does not ferment in the filter bed.
• Storage capacity is chosen by the community. The period for removing the wastewater from the reed bed should be followed by a rest period of at least one week, necessary to avoid stratification of heterogeneous layers of sludge.
• the feeding of the storage can be carried out for a period of at least two weeks, the plants having to be able to withstand prolonged immersion.
• a bypass is provided, in particular by closing an automatic valve, to direct the total flow of effluents to the purification plant when the storage capacity of the bed of plants is reached or when the feeding period is over.
• an automatic program manages the effluent admission valve to the bed planted with reeds from the measurement of the level of liquid in the reed filter, in particular by ultrasonic sensor, and from a programmed clock.
• the automatic program can also control the solid level (massive filter plus sludge produced) and follow it over a long period (several years) to indicate when cleaning must be done.
• the invention also relates to an effluent treatment plant of communities equipped with a sewerage network capable of collecting rainwater or infiltration, for the implementation of the method defined above.
• Such an installation is characterized in that it comprises: a purification plant of capacity adapted essentially to the effluent flow rate in dry weather; - upstream of the treatment plant, a filter bed planted clean to store without fermentation a polluted water surplus, and perform a pre-purification;
• Fig. 1 is a block diagram of a treatment method according to the invention.
• FIG.2 is a schematic, partial vertical section of the treatment plant.
• an installation E of treatment according to the invention comprises a purification station 1 for the effluents of a community having a sewerage network which drains large quantities of water from tablecloth. The network also collects rainwater.
• the flow variations between dry weather and rainy weather would lead, according to the prior art, to size the wastewater treatment plant so that it processes at a relatively constant quality the large water flows due to rain or a thunderstorm, but which are rarely reached in normal service.
• the purification station 1 is of a capacity adapted essentially to the flow of effluents in dry weather.
• capacity adapted to the effluent flow rate in dry weather designates a capacity which, while possibly greater than that strictly necessary in dry weather, remains much less than that which would be necessary to treat, at equal quality, a flow of rain or thunderstorms that can be more than three times higher than the flow in dry weather.
• the purification plant 1 may be of the type with a bacterial bed 2 followed by a bed 3 planted with reeds for final filtration, which gives the outlet 4 treated effluent.
• the raw effluent is introduced through the inlet 5 of the installation E.
• the purification plant 1 may be of a type different from that described above, for example of the conventional activated sludge type, of the type bio-filter or membrane bioreactor, or other.
• the treatment plant 1 makes it possible to treat carbon pollution, or even nitrogen and / or phosphorus pollution.
• the inlet 5 delivers a flow Qt on a screening device 6 whose output 7 is connected to a unit 8 called D.O: "storm weir".
• D.O "storm weir"
• the unit 8 directs all this flow to a pipe 10 connected to the inlet 9 of the station. purification 1.
• the excess Qp is directed by the unit 8 to a pipe 11 connected to the inlet of a filter bed 12 planted with plants, advantageously of reeds R, forming a pool for the storage and pre-purification of excess effluents collected during rainy weather.
• a de-waterer 13 is provided upstream of the filter bed 12.
• a valve H is installed on the pipe 11, upstream of the de-waterer 13.
• the outlet 14 of the filter bed 12 is connected to the inlet of a pumping station 15, the outlet 16 of which discharges a flow Qv of pretreated effluents into the bacterial bed 2 of the purification station 1.
• the outlet 17 of the bed Bacterial 2 delivers Qs + Qv effluent flow to beds 3 for final filtration.
• FIG. 2 schematically illustrates an embodiment of the filter bed 12 and the pumping station 15.
• the filter bed 12 is defined by vertical walls 17 and a bottom 18, made for example of concrete.
• Recovery drains 19 having a sufficient inclination on the horizontal to allow the flow of liquid, are provided near the bottom 18 and through the wall 17 in the direction of the pumping station 15.
• the height hl of a layer 20 containing the drains 19 is of the order of 0.1m.
• This layer 20 consists for example pebbles 20 / 40mm particle size surrounding perforated tubes constituting the drains themselves.
• a support layer 21 is provided above the layer of drains over a height h2 advantageously of the order of 30 cm. This support layer 21 is formed for example gravel 3/10 mm.
• a layer of sand 22 is provided above the support layer 21.
• the height h3 of the sand layer 22 is advantageously about 30 cm, with sand having a particle size of 0.8 / 4 mm.
• the filtering mass consists of the various granular layers mentioned above of alluvial, siliceous origin (effective sizes D10 / D90).
• the sand layer 22 is planted with plants, advantageously with reeds R.
• the vertical walls 17 exceed the upper level of the layer 22 by a sufficient distance so that the storage bed 12 can accept the water in rainy weather up to at a maximum level Lm located at a height h5, preferably of the order of 0.8m, above the last measured solid level N.
• This level N corresponds to the upper surface of a sludge layer 23.
• the height h4 of layer 23 can reach about 0.8m.
• a spillway 24 is provided at the top of the walls 17 to spread the excess rainwater Wp in the storage bed 12.
• the particularity of the rainy weather is to cause an influx of suspended matter, particularly fine, at the entrance of the treatment plant because of the runoff on the soil and by self-cleaning of the collectors.
• the sanding device 13 provided downstream of the screening device 6 prevents clogging of the storage bed 12 by these suspended materials. Given the characteristics of the granulate provided for the sand layer 22 of the storage bed, the sand trap 13 must retain 90% of sands of more than 200 .mu.m in particle diameter.
• the pumping station 15 transfers the filtrate from the planted bed 12 to the purification station 1; the pumping station 15 consists of a basin 25 equipped with at least one pump P1, and in the example shown, two pumps P1 and P2.
• the pumps P1 and P2 are advantageously volumetric type.
• the pump P1 pumps the liquid into the pipe 16 which discharges the liquid into the purification station 1.
• the pump P2 is a backup pump which can take over in case of failure of the pump P1.
• the filter bed 12 and the pumping device 15 may be partially buried in the soil S.
• the minimum level of liquid Li corresponds to the minimum level for the immersion of pumps P1 and P2. This level Li passes substantially through the middle of the support layer 21.
• a device 26 for measuring the level of liquid in the filter bed 12 is provided.
• the measuring device 26 is preferably an ultrasonic sensor. From this measurement of the liquid level and a programmed clock (not shown), an automatic PLC A program manages the admission valve H to allow or not the filling of the storage bed 12 in accordance with predefined rules.
• the automaton A also controls the solid level N (filter mass + sludge produced) and follows it over a long period (several years) to indicate to the operator when the cleaning must be done. The sludge is then taken again using a double bucket machine.
• the minimum liquid level Li is controlled by low level detection in the tank or tank 25 of the pumping station. The operation of the installation is as follows.
• the excess Qp due to the rain is directed towards the filter bed 12 which can be filled to the level Lm.
• the storage capacity of the bed 12 is generally chosen so as to store the usual rains until the maximum level Lm is reached.
• valve H would be closed and the flow would be bypassed, at least in part, to the treatment plant 1.
• the emptying rate of the bed 12 provided by the pumping station 15 is progressive so as not to overload the treatment plant too heavily. This emptying rate is chosen so as to ensure in one week (ie 7 days) the emptying of the complete stock of the bed 12. In other words, when the bed 12 is filled to the level Lm, and in the absence of new input In excess, the pumping station 15 moves the liquid from the maximum level Lm to the lower level Li in one week.
• the plants in particular the reeds R, are chosen to be able to withstand prolonged immersion, and the feeding of the bed 12 can be carried out for a maximum of two weeks. Once the storage capacity is reached or the feeding period is over (maximum 2 weeks), any new water surplus is derived by unit 8 with closing of the automatic valve H. The destocking period is followed by a period of at least a week's rest, necessary to avoid stratification of heterogeneous mud layers.
• the purification plant 1 remains of suitable dimensions to the effluent flow rate in dry weather, since the treatment of excess effluent due to rainfall is spread over several days, at least 7 days preferably .
• the bed 12 makes it possible to store the water in contact with the plant plantation, without observation of fermentation resulting in release of olfactory pollution.
• the real case of a small community of Seine et Marne (France), equipped with a sanitation network very little waterproof and eager to treat a part (160 m 3 ) of its effluents collected in rainy weather, while obtaining the same concentration of treated water as in dry weather is given below in Table 1.
• the footprint of the treatment plant is reduced by a factor of 1.8 (ie 600/335).
• the volume of the bacterial bed, dimensioned for dry weather, does not vary, which greatly reduces the total cost of the treatment plant.
• Qe is the derivative flow (by-passed).
• the column "Dry time” shows on the line Qt the flow of raw effluent arriving at the inlet 5 of the installation. In dry weather, this flow Qt is equal
• the flow Qe of effluent derivative is zero, as well as the flow of rain Qp and thus also the flow rate Qv of effluent discharged by the pumping station 15.
• Initial Vp corresponds to the initial volume of water stored in the bed 12 and which is zero. Similarly the volume “Final Vp” remains zero because the time is dry.
• the column "Rain storage Jl" corresponds to a day when a rainfall volume of 160 m 3 is collected in the filter bed 12.
• the excess over Qs can not be sent into the filter bed 12 full, and is derived by a bypass.
• the fourth column corresponds to the case where the storage bed 12 is not completely filled, but without being completely emptied.
• the storage bed 12 is assumed to be filled with 150 m 3 of effluent from a previous episode and is being destocked.
• a new rainwater effluent can be stored at the level of the available capacity, if this new filling is made less than 14 days (2 weeks) after the end of the last rest period.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Hydrology & Water Resources (AREA)
• Botany (AREA)
• Biodiversity & Conservation Biology (AREA)
• Microbiology (AREA)
• Biotechnology (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
• Biological Treatment Of Waste Water (AREA)
• Hydroponics (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=35720896

Family Applications (1)

Country Status (10)

Families Citing this family (3)

Family Cites Families (5)

• 2005
  • 2005-06-03 FR FR0505664A patent/FR2886639B1/fr not_active Expired - Fee Related
• 2006
  • 2006-05-23 EP EP06764667A patent/EP1888472A2/de not_active Withdrawn
  • 2006-05-23 US US11/916,143 patent/US20080197083A1/en not_active Abandoned
  • 2006-05-23 DE DE06764667T patent/DE06764667T1/de active Pending
  • 2006-05-23 WO PCT/FR2006/001174 patent/WO2006128994A2/fr active Application Filing
  • 2006-05-23 AU AU2006254029A patent/AU2006254029A1/en not_active Abandoned
  • 2006-05-23 ES ES06764667T patent/ES2300233T1/es active Pending
  • 2006-05-23 CN CNA2006800190993A patent/CN101189189A/zh active Pending
  • 2006-05-23 BR BRPI0610940A patent/BRPI0610940A2/pt not_active IP Right Cessation
• 2007
  • 2007-12-03 MA MA30446A patent/MA29530B1/fr unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events