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
  • C02F3/02—Aerobic processes
  • C02F3/08—Aerobic processes using moving contact bodies
  • C02F3/085—Fluidized beds
• • 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
  • C02F3/02—Aerobic processes
• • 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
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the invention relates to a method in improving .the purification of wastewater in biological aerated ponds .
• the wastewater is passed through some type of reactor, tank or basin wherein micro-organisms are utilized for converting impurities existing in the water to harmless end products such as carbon dioxide and water.
• the purification i.a. can be performed under supply of air (aerobically) or without supply of air (anaerobically) .
• the degraded impurities are converted into microbial biomass, a biosludge, which must be separated from the water and removed from the process, dewatered, and cleared off in some way usually by deposition or combustion. Handling of the sludge in connection with biological purification is connected with large operating costs, and it is therefore desired to have a sludge production as low as possible in the biological process.
• a very simple form of biological purification process is the so called aerated pond, which is common i.a. in the forest industry.
• wastewater is purified in an aerated pond or basin the wastewater is simply passed through the pond or basin wherein air is supplied by means of some type of aerating system.
• the active micro-organisms are not retained in the process and, therefore, the content of active micro-organisms usually is low in an aerated pond.
• a long dwelling time therefore is required for the wastewater in the aerated pond, often between two and ten days. At large wastewater flows this means that the process volume will be very large, often several hundred thousand cubic meters.
• a common problem in an activated sludge processes under low load is moreover that there arises sludge separation problems such as so-called sludge swelling, which may provide reduced purification results and difficulties in dewatering the surplus sludge which is removed from the process.
• the rebuilding also results in a considerable increase of the amount of surplus sludge that must be taken care of.
• Biofilm processes usually are operated as processes under higher load which do not reach a purification degree which is as high as that of an activated sludge process at low load. Often biofilm processes are utilized as pre- treatment before a following activated sludge process but biofilm processes are also operated as the only biological purification sometimes in combination with a following chemical precipitation.
• a biofilm process is considerably simpler to operate than an activated sludge process and the need of attendance is low.
• cooling of hot wastewater is required before treatment and addition of extra nutrient salts in the treatment of many industrial wastewaters which usually is not required for treatment in aerated ponds.
• SE-A-9501744-8 a carrier material is introduced directly in the aerated pond.
• JP-A1-51193 JP-A1-51193
• biofilm process with suspended carrier material EP-A-0 575 314, O-A-95/25072
• carrier material in the form of filler bodies of plastics is used said bodies being kept suspended and in movement in the process by air being supplied at the bottom of the reactor tank.
• the method proposed according to the present invention for improving purification of wastewater in biological aerated ponds has obtained the characterizing features of claim 1 and has been found to provide great advantages as compared with the conventional method of improving the purification. It has been found that by the combination of the two processes - the treatment in the aerated pond and the biofilm process - there is obtained a result which is substantially better than the sum of the effects obtained by the individual processes. Moreover, the invention comprises a further method of supplementing said process combination in order to reduce the discharge of suspended material, nitrogen and phosphorous.
• the invention also provides a considerably lower sludge production than an installation of carrier material in the pond.
• a sludge production of 0.04 kg sludge/kg reduced COD while an installation of carrier material directly in the pond gave a sludge production of 0.10 kg sludge/kg reduced COD, and rebuilding for an activated sludge process gave a sludge production of 0.14 kg sludge/kg reduced COD.
• the very low sludge production obtained in a process combination according to the invention has been found to cause problems in achieving high separation degrees of nutrient salts in the process. This is true particularly for wastewaters containing considerable amounts of nutrient salts in relation to the organic material in the wastewater.
• Nutrient salts can be separated from the wastewater primarily by said salts being absorbed by the micro-organisms and being built into the biomass produced by the growth of the micro-organisms. By separating this biomass from the wastewater .after the biological purification process the nutrient salts contained in the biomass will also be separated.
• the invention also relates to this method of improving the separation of nutrient salts.
• the nutrient salts separation will be good even if untreated wastewater is not conveyed to the biofilm process. In many cases no nutrient salt separation is aimed at, and in these cases it is relatively common that there is no separation step after the aerated pond the treated wastewater with biosludge existing therein being discharged directly to the recipient. For these cases the invention can provide a substantial reduction of the discharge of organic material and suspended substances by breakdown thereof in the biofilm process before discharge to the recipient.
• An alternative to the location of an activated sludge process after the biofilm process in order to further improve the purification is to return sludge from a separation step following the biofilm process, directly to the biofilm process, i.e. to operate the process as a hybrid between a biofilm process and an activated sludge process.
• This gives principally the same result as the biofilm process in combination with a separate activated sludge process but requires slightly lower dwelling time in the biofilm process than if said latter process is operated with a following activated sludge process. In some cases there can also be obtained a slightly impaired separatability of the active sludge.
• FIG. 1 discloses an embodiment of the invention with a subsequent sedimentation step
• FIG. 2 discloses the same process combination as FIG. 1 but without a subsequent sedimentation step
• FIG. 3 discloses the same process combination as FIG. 1 but with a shunted partial flow of untreated wastewater
• FIG. 4 discloses a process combination with activated sludge process
• FIG. 5 discloses the same process combination as FIG.
• FIG. 6 discloses the same process combination as FIG. 4 but with two shunted partial flows of untreated wastewater
• FIG. 7 discloses the same process combination as FIG.
• FIG. 8 discloses the same process combination as FIG.
• the untreated wastewater is passed to a presedimentation means 1 and therefrom to a biological aerated pond 2.
• the wastewater is passed from the pond to a tank 3 with carrier material for growth of biofilm, which is kept completely or partly suspended and in movement by air being blown into the tank in order to undergo a biofilm process therein.
• the treated wastewater is discharged via a subsequent sedimentation means 4.
• FIG. 2 does not have the sedimentation means 4 but in other respects corresponds to the plant in FIG. 1.
• FIG. 3 discloses a plant corresponding to that in FIG. 1 but in this case a partial flow 5 of wastewater is conveyed from the presedimentation means 1 past the aerated pond 2 directly to the tank 3 in order to undergo the biofilm process.
• the plant in FIG. 4 also corresponds to that in FIG. 1 but is supplemented by an aerated reactor 6 for activated sludge process between the tank 3 and the subsequent sedimentation means 4 sludge from said latter means being returned to the reactor 6.
• FIG. 6 is a combination of the plants in FIGS. 3 and 5 the wastewater from the pre-sedimentation means 1 being conveyed directly to the tank 3 as well as the reactor 6 the aerated pond 2 being passed over.
• the plant in FIG. 7 corresponds to that in FIG. 1 but in this case sludge 7 is returned from the subsequent sedimentation means 4 to the biofilm process 3.
• a partial flow 8 of wastewater according to FIG. 8 is conveyed from the presedimentation means directly to the biofilm process.

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• Life Sciences & Earth Sciences (AREA)
• Biodiversity & Conservation Biology (AREA)
• Microbiology (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Biological Treatment Of Waste Water (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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• 1997
  • 1997-03-03 SE SE9700735A patent/SE508478C2/sv not_active IP Right Cessation
• 1998
  • 1998-03-03 EP EP19980908397 patent/EP0963351A1/en not_active Withdrawn
  • 1998-03-03 WO PCT/SE1998/000375 patent/WO1998039254A1/en not_active Application Discontinuation
  • 1998-03-03 AU AU66433/98A patent/AU6643398A/en not_active Abandoned

Non-Patent Citations (1)

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