MODULAR METHOD AND WASTEWATER TREATMENT ARRANGEMENT FOR EFFICIENT CLEANING OF WASTEWATER

Abstract

A wastewater treatment arrangement for efficiently cleaning variously polluted partial streams of wastewater, in particular of industrial effluents, includes the following components: an electrodialysis unit; an accidental-damage reservoir, a buffer tank, wherein the buffer tank is designed such that it can be reached by partial streams of some of the wastewater indirectly by way of the electrodialysis unit and/or directly, and wherein the buffer tank is designed such that it can be reached by the partial streams of wastewater indirectly by way of the accidental-damage reservoir and/or directly, and wherein downstream of the buffer tank, a first flotation tank, an anaerobic reactor and an SBR unit are arranged in series before the outflow.

Claims

1.-14. (canceled)

15. A wastewater treatment arrangement for cleaning of individual partial wastewater streams polluted by different industrial effluents, comprising the following components: an electrodialysis unit, an accidental-damage reservoir, a buffer tank, said buffer tank is configured to be accessible directly by some of the polluted partial wastewater streams and/or indirectly via the electrodialysis unit, and said buffer tank is also accessible directly by different polluted partial wastewater flows and/or indirectly via the accidental-damage reservoir, and wherein downstream of said buffer tank, a first flotation tank, an anaerobic reactor and an SBR unit are arranged in series before an outflow.

16. The wastewater treatment arrangement according to claim 15, wherein a denitrification tank with a downstream second flotation tank is arranged in parallel with the accidental-damage reservoir, and wherein the second flotation tank is connected with the accidental-damage reservoir and/or the buffer tank.

17. The wastewater treatment arrangement according to claim 16, wherein a MAP precipitation unit with a MAP magnesium ammonium phosphate recovery is arranged between the anaerobic reactor and the SBR unit.

18. The wastewater treatment arrangement according to claim 15, wherein a concentrate buffer tank is arranged downstream of electrodialysis unit, and/or downstream of the first flotation tank, a flotate buffer tank, and/or downstream of the anaerobic reactor, a gas treatment, gas recovery, cogeneration plant are arranged downstream of electrodialysis unit.

19. The wastewater treatment arrangement according to claim 17, wherein the MAP precipitation unit and/or the SBR unit are configured as two-way units for alternating operation of said units for a quasi-continuous operation.

20. The wastewater treatment arrangement according to claim 19, wherein a sludge buffer tank and/or an outflow reservoir are arranged before the outflow for the clear water and after the SBR unit.

21. The wastewater treatment arrangement according to claim 15, wherein the outflow reservoir is dimensioned such that in normal operation, the wastewater treatment arrangement is filled to only to 50%.

22. The wastewater treatment arrangement according to claim 15, wherein a return pump line into the accidental-damage reservoir is arranged between the outflow reservoir for an eventual accident.

23. A modular method for an efficient cleaning of differently polluted wastewater streams in a wastewater treatment arrangement according to claim 15, wherein a separate measurement of the individual wastewater streams is performed and that the wastewater streams are treated as partial streams separately in a modular manner and are subsequently combined, and undergoing further treatment depending on their properties.

24. The modular method for the efficient purification of differently contaminated wastewater according to claim 23, wherein, depending on the properties of the wastewater partial stream a) an electrodialysis takes place to reduce a chloride load by and a potassium load by relative to the initial value for only a single wastewater partial flow, b) a flotation of undissolved substances takes place, c) an anaerobic wastewater treatment for producing biogas as a valuable material from a high-salt substrate takes place, ) a MAP precipitation for the production of magnesium ammonium phosphate as a valuable substance takes place, and that e) an aerobic wastewater treatment in an SBR process takes place with further P elimination in a salt-rich substrate.

25. The method according to claim 23, wherein the treated wastewater stream is filtered before reaching an outflow.

26. The method according to claim 24, wherein an exhaust air treatment and desulfurization of the biogas generated in the anaerobic wastewater treatment takes place.

27. The method according to claim 24, wherein in step b) a dissolved air flotation is performed.

28. The method according to claim 24, wherein depending on measured phosphorus concentrations, additional phosphorus compounds are eliminated by way of simultaneous precipitation.

Description

[0055] Further details, features and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawing.

[0056] According to an exemplary embodiment of the invention, an industrial wastewater treatment plant in operation is described, with which 2300 m.sup.3/d of production wastewater of a drying plant, which is used to produce demineralized dry whey, is treated for direct discharger quality. Based on the required cleaning capacity for the load contained in the wastewater, this plant corresponds to a wastewater treatment plant of size class 5 according to the Wastewater Ordinance AbwV, which corresponds to more than 100,000 population equivalents.

[0057] The production wastewater of the drying plant to be treated, the partial wastewater stream 20, is characterized by high salt loads, high nutrient contents and high organic loads. Depending on the processing step, water of different composition is produced:

approx. 600 m.sup.3/d less polluted wastewater 24 from the rinsing processes during demineralization,
approx. 500 m.sup.3/d of highly polluted wastewater 20 from demineralization processes,
approx. 500 m.sup.3/d predominantly mineral-contaminated wastewater 22, 23 (vapors, CIP waters from the cleaning and rinsing steps),
approx. 700 m.sup.3/d dairy effluents 21 with high organic load.

[0058] Sanitary and street effluents are collected separately and fed in the aforedescribed case to a municipal sewage treatment plant. Thus, for example, all of the sludge produced on the industrial wastewater treatment plant can be assigned to the food industry based on its origin, which considerably facilitates later recovery.

[0059] The production effluents are fed to the industrial wastewater treatment plant in separate lines 20, 21, 22, 23, 24, which can be fed to a total of six tanks 6.1, 7.1, 8.1, 2, 9, 10.

[0060] All wastewater streams 22, which are highly contaminated with mostly inorganic substances and originate from the regeneration of the cation exchanger of the drying plant, are temporarily stored in a tank 6.1 and fed therefrom first to an electrodialysis unit 1.

[0061] The water 23 originating from the anion exchanger of the production plant is temporarily stored in tank 7.1 and fed therefrom to the electrodialysis unit. The water 24 originating from the backwashing operations of the reverse osmosis unit 8 of the drying plant is temporarily stored in tank 8.1 and fed therefrom to electrodialysis. Optionally, the partial wastewater stream 24 can also be fed directly from the buffer tank 8.1 of the reverse osmosis unit to the buffer tank 2, provided the composition is suitable. Alternatively, this partial wastewater stream 24 is fed to the electrodialysis unit 1 to regulate the pH value.

[0062] The wastewater from the cheese dairy, the inlet 21, is also fed to the independent buffer tank 2, from which the wastewater is directly fed load-controlled to a first flotation tank 11.

[0063] Highly contaminated product wastewaters originating from accidents are intercepted in the accidental-damage reservoir 9, from where they are pumped load-controlled into the buffer tank 2. This ensures that load spikes do not unnecessarily burden the biological treatment stages.

[0064] An outflow reservoir 18, which serves to ensure the Q24 before introducing the purified wastewater via the outflow 19 into the receiving water, communicates with the accidental-damage reservoir 9 via an unillustrated pipe. This interconnection allows back-pumping and temporarily storing of insufficiently purified wastewater fractions, for example, when sludge is discharged in the event of a technical malfunction at one of the SBR plants, and thus serves directly to protect water bodies from pollution. The outflow reservoir 18 is dimensioned so as to be filled in normal operation of the system to only 50%, leaving additional reserves in the event of an accident.

[0065] Effluents with very high nitrate concentrations are fed directly to another separate denitrification tank 10 for protection of the subsequent anaerobic stage. The denitrification tank 10 is used as a small separate denitrification stage located upstream of the actual wastewater purification. The thus denitrified wastewater is fed into the buffer tank 2 via a second flotation tank 12. The denitrification tank 10 is connected to the flotation tank 12 for the purpose of separating the activated sludge required for denitrification and retaining the same in the system. This second flotation tank 12 is to be regarded as one unit with the denitrification tank and provided in the overall arrangement in addition to the first flotation tank 11.

[0066] A particular advantage of the arrangement and the method is that the illustrated separate measurement of the individual wastewater streams allows a further targeted and cost-saving treatment.

[0067] According to a preferred embodiment, the method steps are as follows:

a) electrodialysis (reduction of the chloride load by and the potassium load by compared to the initial value)only for a partial wastewater stream,
b) flotation of undissolved substances,
c) anaerobic wastewater treatment (generation of biogas as a valuable material from a salt-rich substrate),
d) MAP precipitation (production of magnesium ammonium phosphate as a valuable material),
e) aerobic wastewater treatment in SBR reactors (further P-elimination in a salt-rich substrate),
f) wastewater filtration (can be operated optionally).

[0068] In addition, exhaust air treatment as well as the required desulphurization of the biogas produced during anaerobic wastewater treatment are carried out.

[0069] The partial streams of the inflows 22, 23, 24, which contain predominantly high concentrations of inorganic salts, are fed to the electrodialysis unit 1, wherein the ions are concentrated by way of monovalent membranes and discharged into the concentrate buffer tank 5.

[0070] Since the inorganic highly polluted material streams 22, 23, 24 are already detected separately in the drying plant, this process step can be optimized for cost and energy savings. Contamination of the wastewater to be treated by the electrodialysis unit with organic substances from other material streams would cause blocking of the membranes and thus to higher operating costs.

[0071] Thereafter, the wastewater in the buffer tank 2, which is now deconcentrated from salts, is then combined with the other wastewaters 20 from the drying plant contaminated with low salt concentrations and wastewater 21 of the cheese dairy contaminated with low salt concentrations and, not shown, fed directly to the SBR unit 17 for further aerobic treatment.

[0072] The drying plant efluents from the feed of the drying plant 20, which are heavily contaminated with organic compounds such as whey protein and undissolved substances, are introduced directly into the buffer tank 2 and fed therefrom load-controlled to the first flotation tank 11.

[0073] The flotation in the first flotation tank 11 is designed as dissolved air flotation. Aided by flocculants, a portion of the COD is removed in this purification stage. The flotate is fed to the flotation buffer 4 and thereafter to sludge recovery.

[0074] The water discharged from the first flotation tank 11 is fed to an anaerobic reactor 14. In this anaerobic reactor, most of the COD is broken down and converted into biogas. In the described industrial wastewater treatment plant, an R2S reactor was used which operates on the basis of granulated biomass. However, any other anaerobic technology that works with bacteria retention in the fermenter can be used.

[0075] Systems with immobilized biomass are known to be less sensitive to concentration fluctuations. In addition, sufficient active biomass is always present in the system, so that short residence times can be realized even with a low dry-matter content. Wastewater has significantly lower dry-matter content than conventional biogas substrates. In addition, only small amounts of increased biomass in the form of excess sludge are produced in anaerobic processes.

[0076] The resulting fermentation residue is supplied for use in agriculture.

[0077] The biogas is desulphurized with alkaline gas scrubbers. Alternatively, however, other types of desulfurization, for example, biological desulfurization, can be used. In this case, the H.sub.2S contained in the biogas is converted to sodium sulfide or sodium hydrogen sulfide and brought into the aqueous phase. After drying and subsequent purification via activated carbon, the purified gas is then converted into electricity in a cogeneration power plant, whereby the produced electrical energy is used internally for the industrial wastewater treatment plant. These process steps are summarized in the FIGURE with the gas treatment, gas utilization cogeneration power plant 13. Thus, as an added benefit, dependence on the electricity provider is reduced.

[0078] After leaving the anaerobic reactor 14, the R2S reactor, the wastewater is fed to a redundantly configured magnesium ammonium phosphate precipitation stage, the MAP precipitation unit 16.

[0079] Since all effluents originate from the food industry, the precipitated magnesium ammonium phosphate is very pure and can be marketed as a valuable material in what is referred to as MAP magnesium ammonium phosphate utilization 15. The resulting revenues reduce the total costs incurred for wastewater treatment.

[0080] The outflow from the MAP precipitation unit 16 is subsequently further aerobically treated in the activation process. Two SBR units 17 are here used, which are fed alternately. In addition, the reactors were equipped with precipitation/flocculant dosing stations so that, depending on the measured phosphorus concentration, further phosphorus compounds can be eliminated by way of simultaneous precipitation.

[0081] Here, the process stages biological P elimination with or without simultaneous P-precipitation, nitrification and denitrification take place in the same reaction space in consecutive temporal order.

[0082] The excess activated sludge is temporarily stored in a sludge buffer tank 3 and thereafter automatically drained and supplied to agricultural use. The clear outflow from the SBR units 17 is discharged into the receiving water via the outflow reservoir 18 and the outflow 19. The aerobic purification stage of the SBR unit 17 was designed so that the required cleaning performance can be attained even if the anaerobic stage fails, for example due to a short-term shut-down for maintenance purposes, or due to a failure of the MAP precipitation unit 16. However, this is associated with a higher expenditures.

[0083] Optionally, the clear discharge of the SBR unit 17 is also fed to an additional unillustrated wastewater filtration, where additional organically bound phosphorus is removed. The backwash water of the filtration is returned to the SBR units 17.

[0084] Since the effluents from the dairy processing industry are easily microbiologically degradable and consequently tend quickly to form unpleasant odors, the exhaust air from the system components, including the storage and buffer tanks, is cleaned by using a photo ionization process.

LIST OF REFERENCE SYMBOLS

[0085] 1 electrodialysis unit; electrodialysis two-way [0086] 2 buffer tank; buffer tank 2, V=3026 m.sup.3 [0087] 3 sludge buffer tank; buffer tank 3 (sludge), V=455 m.sup.3 [0088] 4 flotate buffer tank; buffer tank 4 (flotate), V=369 m.sup.3 [0089] 5 concentrate buffer tank; buffer tank 5 (concentrate), V=434 m.sup.3 [0090] 6 cation exchanger; L4 cation exchanger (151 m.sup.3d) [0091] 6.1 cation exchange buffer tank; buffer tank 1.1, V=300 m.sup.3 [0092] 7 anion exchanger; L5 anion exchanger (119 m.sup.3d) [0093] 7.1 anion exchange buffer tank; Buffer tank 1.2, V=300 m .sup.3 [0094] 8 reverse osmosis unit; L6 reverse osmosis (231 m.sup.3d) [0095] 8.1 reverse osmosis unit buffer tank; buffer tank 1.3, V=300 m.sup.3 [0096] 9 accidental-damage reservoir; accidental-damage reservoir, V=1000 m.sup.3 [0097] 10 denitrification tank; deni tank, V=1000 m.sup.3 [0098] 11 flotation 1, flotation tank [0099] 12 flotation 2, flotation tank [0100] 13 gas treatment, gas recovery, cogeneration plant [0101] 14 anaerobic reactor; anaerobic reactor R2S, one-way, V=471 m.sup.3 [0102] 15 MAP magnesium ammonium phosphate recovery; MAP (recovery) [0103] 16 MAP precipitation unit; MAP precipitation (two-way), V=2290 m.sup.3 [0104] 17 SBR unit; SBR (two-way), V=22,475 m.sup.3 [0105] 18 outflow reservoir; outflow reservoir, V=1,000 m.sup.3 [0106] 19 outflow [0107] 20 partial wastewater stream, inlet drying plant; L 1/3 drying plant (1097 m.sup.3/d) [0108] 21 partial wastewater stream, inlet cheese dairy; L2 cheese dairy (700 m.sup.3/d) [0109] 22 partial wastewater stream, inlet cation exchanger [0110] 23 partial wastewater stream, inlet anion exchanger [0111] 24 partial wastewater stream, inlet reverse osmosis