Hệ thống xử lý nước thải là hệ thống được tạo thành từ một số công nghệ xử lý nước đơn lẻ hợp thành, giúp giải quyết các yêu cầu xử lý nước thải cụ thể cho từng nhà máy. Mỗi loại nước thải tùy thuộc vào loại hình sản xuất mà sẽ có các công nghệ xử lý đơn lẻ khác nhau hợp thành, để tạo ra một hệ thống xử lý nước hoàn chỉnh. Một hệ thống xử lý nước thải hiệu quả và được thiết kế tốt sẽ giải quyết: 1. Xử lý được những thành phần gây ô nhiễm trong nước thải. Đảm bảo chất lượng nước sau xử lý đạt chuẩn yêu cầu
MIRCEN Journal, 1988, 4, 37-58 New processes for the advanced treatment of wastewaters L Vriens and D Eyben Artois-Piedboeuf Interbrew, Leuven, Belgium Introduction The two-stage, aerobic unitank system (TSU-system) and the tri-stage, anaerobicaerobic unitank system with biological nitrogen removal (3SU-N-system) have been developed at the Research and Development laboratory for Environmental Biotechnology (Artois-Piedboeuf Interbrew), in cooperation with several laboratories of the University of Leuven The 3SU-N-system is a combination of the two-stage anaerobic unitank system (TSU-AN-system) and the single-stage aerobic unitank system with biological nitrogen removal (SSU-N-system) In collaboration with STABO and A V E V E 'Agro en Industrie', two members of the Belgian Boerenbond, turnkey solutions can be offered, including all civil, mechanical and electrical works The two-stage, aerobic unitank system (TSU-system) This is a cost-effective alternative to conventional activated sludge systems The main purpose is to reduce capital and operation costs and to guarantee flexible and reliable operation and high process performance The TSU-system has been patented in Belgium A European patent is pending Description of the process The general principle is schematized in Fig and the flow chart is represented in Fig After the preliminary treatment (screening, grit-removal, no primary settlement, eventual buffering) the wastewater is first treated in a high-loaded combined aerationsedimentation stage The BOD reduction is about 80-85% The partially purified water then flows by gravity to a second low-loaded combined aeration-sedimentation stage where the residual B O D is removed to obtain a high-quality effluent resulting in more than 98% B O D reduction Each combined aeration-sedimentation stage of the TSU-system is composed of one rectangular tank divided by two baffles into three square units which are hydraulically connected All units are provided with an air diffuser system The exterior units are also provided with a weir The middle unit of each stage always serves as an aeration compartment, whereas the exterior units can serve both as aeration or sedimentation compartments The wastewater is introduced in an aerated exterior unit of the first stage The Oxford UniversityPress 1988 38 L Vriens and D Eyben WASTE'WATERI A,R= HighBODconcentration Averagetemperature30~ I I I FIRSTH I G H - L O A D E ~ ~1 EXCESSSLUDGE TREATMENT SLUDGEDISPOSAL AIR=*[ SECONDLOW-LOADEDCOMBINED I OXlDATION-SEDIMENTATIONSTAGE ] BOD-removalefficiency98% ] Fig Principle of the TSU-system sludge suspension flows towards the continuously aerated inner unit and then to the other exterior unit which at that moment functions as a sedimentation tank The sludge suspension settles and the effluent flows by means of the weir to the second combined aeration-sedimentation stage, where the same process takes place After a period of time the flow direction in the combined aeration-sedimentation stages is changed The TSU-system requires no separate settling tanks nor sludge recycle facilities The excess sludge of both stages is continuously wasted out of the inner units and fed to the sludge thickener The type of sludge stabilization (aerobic, anaerobic, chemical) is dependent on the scale of the plant and on the final option for disposal of the sludge The stabilized sludge is then conditioned and further dewatered by mechanical means Operation of the process The TSU-system functions in an alternating mode of operation which can be described as a repetition of a sequence of two main phases divided by two intermediate phases (Fig 3) (a) First main phase The wastewater is pumped into unit A of the first stage As this 39 Advanced treatment of wastewaters Influent I"'"'~ Buffering tank " I ] I I High rate oxidation I I I - -' I _F_I ] Surpressor Effluent Fig Flowchart of the TSU-system (two-stage unitank system) unit is aerated, the sludge microorganisms degrade and accumulate the exogenous substrate (accumulation phase) The mixed liquor flows through the connecting pipe (a-b) into unit B which is always aerated (regeneration phase) The regenerated sludge then flows through the second connecting pipe (b-c) to unit C where the aeration has been cut off (sedimentation phase) The effluent of the first stage flows through the weir of unit C to the aerated unit F of the second stage The mixed liquor flows through the connection pipe (e-f) to the continuously aerated inner unit E, and further to unit D which serves as a sedimentation tank The effluent is discharged through the weir of unit D During this first main phase the sludge concentration is decreasing in the aerated units A, B, E and F while in the sedimentation units C and D Influent lnfluent J / Influent Effluent Effluent L tnfluent Effluent Effluent ::i:::'.'.':::::i~::i::i!ii:~:i:iii~i!i~i~ First main phase First intermediate phase Second main phase Fig Cyclic operation of the TSU-system Second intermediate phase 40 L Vriens and D Eyben the amount of sludge increases Therefore the length of this phase is limited by the hydraulic load and is normally between 90 and 180 (b) First intermediate phase During this intermediate phase the function of the exterior units is reversed Aeration in units A and F is stopped and these units become sedimentation tanks The aeration in unit C starts completing the regeneration of this sludge Meanwhile the wastewater is directed to the inner unit (E) of the second stage (accumulation phase) The aeration in unit D remains off and the sludge suspension flows from the inner unit E to the exterior unit D where the sludge settles and the effluent flows out through the weir The length of this intermediate phase is primarily dependent on the sludge settling characteristics and is normally about 15 (c) Second main phase This phase is similar to the first main phase but the flow through the plant is in the opposite direction The wastewater is pumped into the aerated unit C and aeration of D is started The sludge exhibits a regenerated capacity for oxidative assimilation of the substrate (accumulation phase) and flows to the aerated inner unit B (regeneration phase) and further to unit A which serves as a settling tank The effluent of the first stage flows through the weir of unit A to the aerated unit D of the second stage The flow of the sludge suspension in the second stage is also in the opposite direction as in the first main phase The effluent is discharged through the weir of unit F The duration of this second main phase is just as long as the first main phase (90 to 180 min) (d) Second intermediate phase This phase is similar to the first intermediate phase The function of the exterior units is again reversed Units C and D become sedimentation tanks The sludge in unit A is regenerated The wastewater is again added directly to the inner unit E of the second stage (accumulation phase) Unit F remains a sedimentation compartment and the sludge suspension flows from the inner unit E to the exterior unit F where it settles The effluent flows out through the weir of this unit The length of this phase is also about 15 (e) Wasting of excess sludge For optimum control of solids retention time in both oxidation stages, sludge wasting may be accomplished continuously from the interior units (f) Control of sludge bulking The succession of two distinct phases in both oxidation stages, an 'accumulation phase' during substrate addition and a 'regeneration phase' when the sludge is aerated without addition of substrate, will select floc-forming microorganisms which have good settling characteristics The proliferation of filament-forming microorganisms causes sludge bulking Comparison with other activated sludge systems A goal design engineers like to achieve in an activated sludge process is to increase the rate of substrate removal so that smaller treatment units are required for achieving the same treatment efficiency as in a low-loaded activated sludge system Kinetic models available and engineering experience reveal that those goals can only be achieved in a two-stage process The first stage is operated at high organic loading to increase the Advanced treatment of wastewaters 41 rate of waste removal Because the BOD removal is insufficient to meet the effluent requirements, a second stage which operates at low organic loading is required Although the total aeration volume and total oxygen requirement in a two-stage process will be lower to achieve the same treatment efficiency compared to a lowloaded one-stage process, the latter system has the great advantage that only one clarifier is required Each stage of the conventional two-stage process must have its own integral clarifier and sludge recycle system resulting in much higher building, equipment and operation costs The TSU-system which has no separate settling tanks nor sludge recycle facilities eliminates the disadvantages and extends the advantages of the conventional two-stage system (Fig 4) Possible process modifications (a) Carbon removal: TSU-C-system low-rate oxidation First-stage: high-rate oxidation Second-stage: Low rate system Conventional system Conventional two stage system I i, Two stage unitank system Fig TSU-system: comparison with other activated sludge systems 42 L Vriens and D Eyben The first stage of the TSU-C-system is operated at high organic loading (short solids retention time) The second low-loaded stage removes the residual BOD to guarantee a high-quality effluent (c) Nitrogen removal: TSU-N-system First stage: high-rate oxidation Second stage: low-rate oxidation with nitrification and denitrification In a TSU-N-system the carbonaceous and nitrogenous oxidations are separated in order to assure reliable operation In the first stage, the bulk of the carbonaceous oxygen demanding material is removed In the second stage, the solids retention time is comparatively long because of the controlled growth of the autotrophic nitrifying organisms It is also possible to insert a stirred unit for denitrification (c) Phosphorus removal: TSU-P-system First stage: high-rate oxidation, Second stage: low-rate oxidation and simultaneous precipitation The biological treatment in the first stage in the TSU-P-system is completed with a chemical treatment in the second stage in order to achieve a high-rate reduction of phosphorus This is accomplished by adding a flocculent agent; the soluble phosphorus will thereby be precipitated as sludge Biological phosphorus removal is under study Advantages of the TSU-system (a) Less capital costs primary settling - - L e s s total aeration volume because of the considerable higher BOD load No separate sedimentation tanks No sludge scraping mechanism - - N o sludge recycle facilities - - Rectangular tanks: compact construction possible make full use of available land cheaper and easier to construct than circular tanks economical lengths of connecting pipes and channels - - C o m p a c t system: smaller land area required No (b) Less operational costs - - L e s s energy for aeration - - N o energy for sludge recycle Less maintenance costs (less moving parts) (c) Better process performance (Table 1) High-treatment efficiency of sludge bulking Simple and reliable process: reduced need for supervision Control (d) Easily controlled by microprocessor For reasonable simple treatment objectives, a Advanced treatment of wastewaters 43 Table Performance data of the TSU-system treating combined malting and brewery effluents compared with the low-loaded activated sludge process (plug-flow type) TSU-system Low-loaded activated sludge system (Artois breweries) Pilot-scale (Artois breweries) Full-scale (Canton, China) 1200-1300 1900-2200 15-25 600-900 900-1200 26-32 First stage Secondstage First stage Secondstage Influent BODmg 1-1 COD mg 1-1 Temperature (~ 1200-1300 1900-2200 18-25 Reactor HRT (hours) SRT (days) BOD sludge loading SVI ml g-1 72 20 0.1 40-50 10 0.5 80 25 0.09 70 14 / 0.3 60 13 / 0.05 50 Effluent BOD mg 1-1 5-10 5-15 8-15 time clock control is sufficient If a more sophisticated and more flexible control system is desired, microprocessor control systems may have considerable utility in this regard (e) Flexible operation - - Possibility for temporary operation of half capacity (for seasonal operation plants, or during periods of maintenance work) Full capacity can be restored quickly Possibility for temporary operation as two high-loaded one-stage systems (during periods of peak production or heavy rainfall) conserving a treatment efficiency of 80-85% B O D reduction - - Possible applications: brewing and malting wastewater treatment municipal wastewater treatment food processing wastewater treatment industrial wastewater treatment aerobic post-treatment of anaerobic effluents The two-stage anaerobic unitank system (TSU-AN-system) Anaerobic digestion fundamentals The anaerobic digestion process is a two-phase biological process (Fig 5) In the first phase the complex polymeric substrates are hydrolyzed to simpler soluble molecules with the aid of extracellular enzymes The products of hydrolysis are catabolized next by fermentative microorganisms to produce mainly volatile fatty acids, aldehydes, alcohols, carbon dioxide and hydrogen In this first phase, also called the 'acidogenesis phase', partial removal of suspended solids will be practised by L Vriens and D Eyben 44 ORGANICWASTES(complexpolymericsubstrates) carbohydrates,proteins, lipids F A I C R I Hydrolysis by bacterial exo-enzymes T P H A S E G E N E S I S MONOMERS Hexoses,pentoses,peptides,amino-acids,longchain fatty acids, glycerol l Fermentative microorganisms H2,CO2,Formate,acetatepropionate,butyrate,ethanol lactate,aldehydes 'E ~ E Acetogens N A D N O P G H E A N S E E S S Acetate, CO2,H2 Methanogens 0H4+002 [ Fig Flow-scheme for the anaerobic digestion of waste components to biogas presedimentation In the second phase the majority of the fermentation products, with the exception of H2, CO2, formate and acetate, must undergo further cleavage by the acetogens to yield acetate and H2 and in the case of odd-numbered fatty acids, additionally CO2 The acetogens grow in very close association with the methanogens Indeed, the methanogens have to remove directly the hydrogen produced by the acetogens in order to render the thermodynamic conditions favourable for growth of the acetogens A variety of methanogens use H2, CO2, formate and acetate to form methane Principle of the TSU-AN-system The TSU-AN-system is a two-stage anaerobic digestion process schematized in Fig The acidogenesis and methanogenesis take place in separate reactors so that more Advanced treatment of wastewaters 45 attention can be directed towards determining and providing optimal environmental conditions for each group of microorganisms In the first stage, the biological conditioning tank, the incoming wastewater is buffered, presedimented, hydrolyzed and fermented The excess sludge will be discharged to the sludge thickener and further treated The first reactor permits removal of at least in part H2S in the off-gas This results in a higher-quality biogas of the second stage The second stage is an WASTEWATER HighBODconcentration Averagetemperatureabove30~ I PRELIMINARYTREATMENTI BIOLOGICALCONDITIONINGTANK buffering/presedimentation - hydrolysis acidfication D OFF-GAS - - i pH-control nutrients I t CORRECTION I TANK ~.~ SLUDGE TREATMENTI ! SLUDGEDISPOSAL HYBRIDMETHANEREACTORI UPFLOW-CONTACTPROCESS BIOGAS I ,ue.z I BOD removalefficiency80-90% Fig Principle of the TSU-AN-system 46 L Vriens and D Eyben hydride methane reactor which incorporates a combination of an upflow process and the anaerobic contact At the bottom of the reactor a dense bed of granular sludge is developed with biomass concentration exceeding 60 g 1-1 while flocculent biomass extends above this The produced biogas will be used as energy source The TSU-AN-system operates in a continuous repeating cycle which consists of two main phases divided by two short intermediate phases Description of the process (Fig 7) The TSU-AN-system is composed of two covered rectangular tanks, built next to each other The biological conditioning tank is divided by two baffles into three square units (A, B, C) which are connected hydraulically The bottom in the exterior units is flat while in the interior unit it is conical The three units are equipped with submersible stirrers to keep the solids in suspension and to homogenize the contents When it is necessary the solids can settle at the conical bottom of the inner unit At regular time intervals, the settled solids (after complete stabilization) will be discharged out of the inner unit to the sludge thickener and further treated The exterior units are equipped with floating weirs so that the level in the conditioning tank can vary, which permits a regular feed to the methane reactor Through a central feed line the raw wastewater can be introduced in the three units (A, B, C) of the biological conditioning tank (controlled by the opening or closing of automatical values) The off-gas is fared-off T Fig Two-stageanaerobic unitanksystem(TSU~AS-system) The supernatant coming out of the biological conditioning tank will flow by gravity to the correction tank where the pH, if necessary, will be corrected From the correction tank, the conditioned wastewater will be pumped at a controlled flow to the methane reactor The methane reactor is an hybrid reactor which incorporates a combination of an upflow process and an anaerobic contact Therefore the reactor is divided by a baffle into two units which are connected hydraulically in the upper part Advanced treatment of wastewaters 47 of the reactor Both units are equipped with a three-phase (gas-liquid-solid) separation system and with a weir for effluent discharge From the correction tank, the wastewater will be introduced at the bottom of either of the two units The produced biogas is stored in the gasholder and can be used as energy source The effluent is discharged through the weir of either of the two units Operation of the process (Fig 8) The wastewater is pumped in unit (A) of the biological conditioning tank which is stirred to keep the solids in suspension and to homogenize the content The mixed liquor then flows to the inner unit (B) which will be either stirred or not stirred (if sedimentation of the solids is required to control the solids retention time) From the inner unit, the wastewater flows to the other exterior unit where the mixing is stopped to allow the solids to settle The supernatant, deprived of settleable solids, flows over through the floating weir and flows by gravity to the correction tank and from there the wastewater will be pumped at a controlled flow to the methane reactor i First main phase Second main phase Fig Cyclicoperation of the two-stage anaerobic unitank system (TSU-AN-system) By introducing the wastewater in one part of the reactor the fluidization and expansion of the sludge bed will be very high owing to the higher hydraulic load and higher biogas production per cubic metre and consequently there will be a very intense contact between sludge and substrate which makes mechanical agitation by external devices unnecessary In this unit a considerable fraction of the sludge granules will be dispersed in the liquid above the sludge bed, i.e the sludge bed as a separate phase may even vanish owing to the higher loading rate applied, the heavy turbulence brought about by upflowing gas bubbles and the decreasing actual density of the granules owing to adherent or occluded gas bubbles This reactor becomes an almost completely mixed reactor The pressure drop over the bed in this unit becomes insignificant In classical upflow systems, the gas mixing of the bed is negligible for low strength wastewater which will cause a severe increase in channelling and consequently cause 48 L Vriens and D Eyben poor contact between sludge and wastewater But on the other hand, intense fluidization in conventional upflow systems promotes the expansion of the sludge bed to the top of the reactor where the three-phase separator is located and this will cause substantial losses of the biomass through the effluent even when the sludge settleability is very good and the separating device works sufficiently In the hybrid reactor, the mixed liquor (especially the lighter flocs) flows from a compartment where the bed is very much expanded to the other compartment where the reactor is very quiescent because there is no direct introduction of wastewater and therefore a low gas production In this quiescent unit, the sludge settles: the coarser and/or heavier sludge granules will accumulate in the lower part (the sludge bed); the lighter flocs will settle on top of them (sludge blanket) The clear effluent flows out through the three-phase separation system After a period of time, the flow direction in the biological conditioning tank and in the methane reactor will be reversed The settling units become heavy turbulent units and the heavy turbulent units become settling tanks The length of the main phases is limited by the hydraulic load and is normally between 90 and 180 rain It is also possible to operate both units of the methane reactor in parallel Advantages of the TSU-AN-system - - L o w energy requirements: no energy is required for aeration Reduced sludge production - - T h e biogas produced can be a valuable additional energy source (0.4 m biogas produced for each kg C O D eliminated) - - T h e process is effective at very high loadings Low nutrient requirements - - T h e process is totally enclosed, eliminating odour problems and bacterial aerosols - - T h e sludge activity remains unchanged after long periods of shut down Sludge wash-out is reduced to a minimum Two-phase operation allows a reduction in total reactor volume and also avoids organic and hydraulic overloading and fluctuations which can result in serious lowering of efficiency - - T h e first reactor permits to remove at least part of the H2S in the off-gas This results in a higher quality biogas in the second reactor Presedimentation results in a decreased content of inert solids in the methane reactor This means a more active biomass The amount of suspended solids in the effluent is also much reduced Sludge wash-out is reduced to a minimum - - L e s s capital costs rectangular tanks: make compact construction possible make full use of available land owing to the common walls the system is less costly to insulate easy to construct compact system: smaller land area required Performances of the TSU-AN-system The performanees o f the process in the anaerobic treatment of brewery wastewater are given in Table Advanced treatment of wastewaters 49 Table Performances of the TSU-AN-system in the anaerobic treatment of brewery wastewaters Parameter Influent C O D (mg/1) Suspended solids (mg/1) Biological conditioning tank Hydraulic residence time (hours) Full-scale upflow system: Sebastian Artois Brewery, Armenti&es, France Pilot-plant TSU-AN-system: Artois Breweries, Leuven, Belgium 3000-3800 800-1000 2000-2500 300-400 5-6 (extended for the moment to 10-12) 10 6-8 8-10 Methane reactor COD space loading (kg COD/m day) Hydraulic residence time (hours) Temperature (~ 8-10 5-7 >35 29-30 Effluent Total COD (mg/1) Soluble COD (mg/1) Suspended solids (mg/1) Total nitrogen (mg/l) 300-500 220-400 250-500 30-60 250-400 200-300 150-250 20-40 Single-stage aerobic unitank system with biological nitrogen removal (SSU-N-system) Fundamentals of biological nitrogen removal Despite the many advantages of anaerobic wastewater treatment, it will always remains a primary partial biological treatment step For the removal of the remaining BOD, NH4+ - N, P O ~ - - P , suspended solids and dissolved malodorous compounds there is still an important place left for more advanced post-treatment processes To insure a high BOD- and nitrogen-removal efficiency, this post-treatment process has to be a low-rate oxidation stage with biological nitrogen removal Biological removal of nitrogen proceeds through the nitrification-denitrification processes During nitrification N H + - N is oxidized by a specific group of bacteria (the autotrophic nitrifying organisms Nitrosomonas and Nitrobacter) to form nitrite and then nitrate This nitrification process requires oxygen (4.5 kgO2 per kg N H + - N oxidized) Owing to their low growth rate, the nitrifying bacteria can only maintain themselves if the sludge retention time is long enough Nitrification NH4+ + 2 - + NO3- + H20 + 2H + + energy 50 L Vriens and D Eyben During denitrification the nitrite or nitrate will be reduced to N gas by facultative anaerobic heterotrophic bacteria In this process, nitrate serves as the electron acceptor in the oxidation-reduction reactions of the carbon substrate to provide energy for cell growth Biological denitrification is achieved under conditions of low (4.5) the denitrification will be incomplete If complete N removal is required, additional degradable COD, e.g in the form of unpurified wastewater (or acidified wastewater) will in most cases have to be supplied to the denitrification step It appears that a large part of the COD in the anaerobically-treated wastewater is present as suspended solids This COD is only partially degraded in the biological post-treatment, but is primarily removed by adsorption on the sludge flocs Bad smells will also be removed efficiently in the nitrification-denitrification system The excess sludge is wasted and discharged to the sludge thickener and further treated Description of the SSU-N-system (Fig 10) The SSU-N-system is composed of a rectangular tank divided by four baffles into five units (F, G, H, I, J) which are connected hydraulically All units, except the inner unit, are provided with an air diffusor system The exterior units (F, J) are also provided with a weir for effluent discharge These exterior units can serve both as aeration or as sedimentation compartments This is controlled by the opening or Advanced treatment of wastewaters I WASTEWATER [ 51 Low BODconcentration HighNitrogenconcentration PRELIMINARYTREATMENT LOWLOADEDCOMBINEDOXIDATION SEDIMENTATIONSTAGEWITH BIOLOGICALNITROGENREMOVAL AIR Excess Sludge EXCESSSLUDGE TREATMENT U i SLUDGEDISPOSAL J I V EFFLUENT ] BODremovalefficiency98% Nitrogen-removalefficiency90% Fig Principle of the single-stage aerobic unitank system with biological nitrogen removal (SSU-Nsystem) closing of the automatic valves The units G and I are continuously aerated Unit H is continuously stirred Through a central compressor the units F, G, I, J can be aerated A system for internal sludge recycle from the anoxic unit H to alternatively one of the exterior units (F or J) has to be installed The excess sludge is wasted out of the anoxic unit and discharged to the sludge thickener and further treated Operation of the SSU-N-system (Fig 11) The raw wastewater (anaerobic effluent) is added continuously to the anoxic unit H 52 L Vriens and D Eyben because the COD in the wastewater will be used as a carbon source to perform denitrification In the first main phase, the mixed liquor is pumped to the aerated exterior unit F where the residual COD will be removed by oxidation Nitrification will also be performed in this exterior unit From this exterior unit, the sludge suspension will flow to the permanently-aerated unit G and then the mixed liquor flows again to the anoxic unit (denitrification) part or it is again recycled The sludge (the same volume as the amount of wastewater which is added to the system) flows to the other continuously-aerated unit I (post-aeration) and from there to unit J which at that moment serves as a sedimentation compartment The effluent is discharged through the weir of this unit After 90 to 180 rain, the flow through the system is reversed The function of the exterior units is changed The sludge is now recycled in the other direction Advantages of the SSU-N-system (a) Less capital costs - - N o separate sedimentation tanks - - N o sludge-scraping mechanism - - N o sludge-recycle facilities from the sedimentation tank to the aeration tank - - Rectangular tanks: compact construction possible make full use of available land cheaper and easier to construct than circular tanks economical lengths of connecting pipes and channels - - C o m p a c t system: smaller land area required (b) Less operational costs - - L e s s energy for aeration/recuperation of the oxygen owing to the denitrification process - - N o energy for sludge recycle from sedimentation tank to aeration tank - - L e s s maintenance costs (less moving parts) (c) Better process performance (Table 3) - - High-treatment efficiency >98% B O D removal >90% N removal - - C o n t r o l of sludge bulking - - S i m p l e and reliable process: reduced need for supervision (d) Easily controlled by microprocessor (e) Flexible operation The tri-stage, anaerobic-aerobic unitank system with biological nitrogen removal (3SUN-system) The 3SU-N-system is a combination of the two-stage anaerobic unitank system (TSUAN-system) and the single-stage aerobic unitank system with biological nitrogen removal (SSU-N-system) For the description and working principle (Figs 12, 13 and 14) refer to the discussions above Advanced treatment of wastewaters D L_ z, i e- 12d e 53 54 L Vriens and D Eyben First main phase N ":.'.,,-'.,:-;"~"v L,N t.%.:':~.;~,'~ g'~.'~:~ I Second main phase Fig ll Cyclic operation of SSU-N-system (see text) Summary The principle of the Artois-Piedboeuf lnterbrew wastewater treatment is: (1) the construction of a one-tank compact rectangular tank divided into compartments each having defined functions This allows reduction in capital and operation costs (2) The number of compartments allows a two-stage treatment to obtain better process performances (3)For the same reason, the compartments are designed to allow two hydraulic reversed flow directions The three-stage anaerobic-aerobic unitank system with biological nitrogen removal (3SU-N-system) is an example of such a treatment It combines a biological conditioning tank for buffering, presedimentation, hydrolysis and acidification (three compartments) with a hybrid methane reactor combining the upflow process and the anaerobic contact process (two compartments) and with a low-rate oxidation stage for biological nitrogen removal (five compartments) The efficiency of the system is a BOD removal of 98% and a nitrogen removal of 90% R6sum6 Nouveaux procdd~s pour le traitement avancd des eaux rdsiduaires Le principe du traitement des eaux us6es des Brasseries Artois r6side en (1) la construction d'un r6servoir unique divis6 en compartiments ayant chacun une fonction d6finie Ceci permet une diminution du capital et du coot op6rationnel (2) Un nombre de compartiments permettant un traitement en deux 6tapes pour l'obtention de performances plus 61ev6es et (3) la conception, pour les m6mes raisons, de compartiments permettant des flux hydrauliques en direction Advanced treatment of wastewaters 55 HighBODconcentration Highnitrogenconcentration Averagetemperatureabove30~ i WASTEWATERi PRELIMINARYTREATMENT BIOLOGICALCONDITIONING TANK - buffering/presedimentation - hydrolysis acidification - pH-control Nutrients ~ CORRE~CTi0N' i TANK ], SLUDGE TREATMENT I BIOiAS SLUDGEDISPOSAL I HYBRIDMETHANEREACTOR t UPFLOW-CONTACT PROCESS AIR I~ LOW-RATE OXIDATIONWITH [ BIOLOGICALNITROGENREMOVAL BODremovalefficiency98% Nitrogen-removalefficiency90% Fig 12 Principleof the tri-stage anaerobic-aerobicunitank systemwith biologicalnitrogen removal (3SUN-system) 56 L Vriens and D E y b e n Table Performance data of the SSU-N-system in the aerobic post-treatment of brewery wastewaters with biological nitrogen removal Pilot-plants Parameter Influent Total COD (mg/1) Soluble COD (rag/l) Suspended solids (mg/1) Total nitrogen (rag/l) Sebastian Artois Brewery Armenti~res, France Artois Breweries, Leuven, Belgium Full-scale plant: Sebastian Artois Brewery, Armenti6res, France 300-500 220-400 250-500 30-60 250-400 200-300 150-250 20-40 U N D E R " Reactor Hydraulic residence time (hours) Temperature (~ 10 25 25 Effluent Total COD (mg/1) NH4+ - N (mg/1) NO3 N (mg/1) NO2 N (mg/1) PO - - N Suspended solids (mg/1) 50-90 0-2 0-2 0-0.5 1-2.5