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Veolia’s Case Studies for Small Wastewater Treatment Plants

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prepared by Xin, ZHAO*, Mark, ELLIOTT *, Edwin, TAN *, Edmond, CHEUNG *, Xiaohua CHEN * * Veolia Water Solutions and Technologies (Beijing) Co., Ltd., Beijing 100004, China (E-mail: …

prepared by Xin, ZHAO*, Mark, ELLIOTT *, Edwin, TAN *, Edmond, CHEUNG *, Xiaohua CHEN * * Veolia Water Solutions and Technologies (Beijing) Co., Ltd., Beijing 100004, China (E-mail: xin.zhao@veoliawater.com) for Urban Environments in Asia, 25-28 May 2011, Manila, Philippines. organized by International Water Association (IWA).


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  • 1. Veolia’s Case Studies for Small Wastewater Treatment Plants Xin, ZHAO*, Mark, ELLIOTT *, Edwin, TAN *, Edmond, CHEUNG *, Xiaohua CHEN * * Veolia Water Solutions and Technologies (Beijing) Co., Ltd., Beijing 100004, China (E-mail: xin.zhao@veoliawater.com) Abstract Asia is facing immense challenges arising from rapid population growth and intense urbanization, where about 45% of the population now live in towns and cities, and the population densities are much higher than other parts of the world. Against the backdrop, the lack of wastewater management continues to be a huge challenge. Conventional centralised approaches to wastewater management have been one of the solutions to address the wastewater disposal needs of poor communities, but due to the high capital investment, poor operation and maintenance or low connection rates, some disadvantages revealed. As one of the cutting edge technical company, specialized in water and wastewater treatment for industries and municipalities, Veolia Water Solutions and Technologies provides solutions for small wastewater treatment plants, which are practicable for the decentralized wastewater treatment systems in Asia. Several case studies will be presented in this article to illustrate the applications. Biologically Aerated Filter (BiostyrTM) package with Case Study Biologically aerated filtration (BAF) is an alternative to the traditional activated sludge process commonly used in biological wastewater treatment. The BiostyrTM process is an up-flow BAF system using a submerged and floating fine granular polystyrene media. The modularized design enables this technical to be applied for various scales of wastewater treatment plants. Submerged Aerated Filter (SAF) with Case Study SAF is an upflow bioreactor, without moving bed like BiostyrTM and using the MBBR media to form the biofilm. This technology is compact and easy to be installed. Pure Moving Bed Biological Reactor (MBBR) with Case Study The AnoxKaldnesTM Moving Bed Biofilm Reactor (MBBR) technology is based on the biofilm principle with an active biofilm growing on small specially designed plastic elements that are kept suspended in the reactors. Pure MBBR technology combined with ActifloTM, DiscfilterTM or high efficiency settler (MultifloTM) would be a good solution to the small plants. Membrane Biological Reactor (BIOSEPTM) with Case Study The BIOSEPTM process associates biological treatment by activated sludge to membrane filtration. The presence of membranes allows avoiding all problems related to clarification and makes the treatment line more compact. Activated Sludge Treatment (AZENITTM) with Case Study The process AZENITTM, as a high efficient nutrient removal process, is the association of a contact tank and a set of tanks treating the carbon and nitrogenous pollution. Keywords Biologically Aerated Filter (BiostyrTM) package; Bio-submerged aerated filter (SAFTM); Pure moving bed biological reactor (MBBR); Membrane Biological Reactor (BIOSEPTM); Advanced Activated Sludge Treatment (AZENITTM); Small Wastewater Treatment Plants; Decentralized wastewater treatment systems1. IntroductionAsia is facing immense challenges arising from rapid population growth and intense urbanization,where about 45% of the population now live in towns and cities, and the population densities are
  • 2. much higher than other parts of the world. Against the backdrop, the lack of wastewatermanagement continues to be a huge challenge. Conventional centralised approaches to wastewatermanagement have been one of the solutions to address the wastewater disposal needs of poorcommunities, but due to the high capital investment, poor operation and maintenance or lowconnection rates, some disadvantages revealed. The decentralized approach offers opportunities forwastewater re-use and resource recovery as well as improvements in local environmental healthconditions [1].As one of the cutting edge technical company, specialized in water and wastewater treatment forindustries and municipalities, Veolia Water Solutions and Technologies provides solutions for smallwastewater treatment plants, which are practicable for the decentralized wastewater treatmentsystems in Asia. The package scaled wastewater treatment facilities are modular design, which arecompact, suitable for installation within restricted footprint, high efficiency and easy for operationand maintenance.Several case studies will be presented in this article to illustrate the technologies and applications.2. Veolia’s Solutions and Case Studies for Small Wastewater Treatment Plant2.1 Biologically Aerated Filter (BAF) packageResponding to the demands for compact BAF system, suitable for installation within a restrictedfootprint, to meet specific biological treatment demands including total nitrogen removal, Biostyr®Package Plant is developed.Principle of BiostyrTM Package Plant [2]The BiostyrTM process consists of upflow filtration through a submerged, floating fine granularpolystyrene media (BiostyreneTM) bed. The media is of a small size and uniform shape, thusproviding a high specific surface area. In filtration mode the BiostyreneTM beads form a compactfloating media bed retained within the units below the filter nozzle floor. The co-current upflowthrough this floating media bed of the influent together with process air provides an idealenvironment for fixed film microorganisms to attach themselves to the BiostyreneTM media. Theprocess and scour air is introduced to the unit through a common air grid located at the bottom ofthe unit below the suspended media bed.The BiostyrTM Package Plant is suited for all biological treatment applications from carbon removalto tertiary nitrification. However, it is particularly well suited for Total Nitrogen removal, and forpost de-nitrification applications with the addition of an external carbon source, in the post-de-nitrification configuration no process air would be required.Fig.1 The BiostyrTM Package Plant unit Fig.2 Typical BiostyrTM Package Plant Installation
  • 3. Periodically the individual units require backwashing. This is initiated either on a pre-set timer basis,or, on a media bed head loss set point. The media is backwashed by gravity using the treatedeffluent retained above the filter nozzle floor within the units, thus removing the requirement forbackwash pumps. The suspended solids retained with the media bed, together with excess biomassare purged from the unit into a common dirty wash water storage tank. During this washing phasethe Biostyrene® media is air scoured using the process air blowers, and washed with the retainedtreated effluent on an alternate cyclic rotation to optimise the removal of the retained solids.Following completion of the washing cycle, the flow through the unit is reversed, process air is re-introduced and co-current treatment continues.The BiostyrTM Package Plant has several advantages over other BAF processes: Modular design – it is able to select the correct size, number and material for the units to meet all the application requirements. The standardized unit sizes have been selected to allow the equipment to be transported to the site location following assembly and testing at the works, helping to reduce the overall project duration considerably. The units can be off-loaded directly on to concrete foundations. Separate clean backwash tank and pumps are not required, as the retained head of treated effluent above the filter nozzle floor is sufficient to wash the filters in all applications. Access to the filter nozzles is very easy with no requirement to empty the media. Odour and aerosol emissions are minimised due to the surrounding air only being in contact with the oxygenated treated water above the nozzle floor. Stripping of volatile malodorous components in the effluent is avoided and the dirty wash water remains in an enclosed space without exposure to the atmosphere and hence potential odour release. BiostyreneTM buoyant media - Efficient washing is achieved because of its light synthetic structure. The effective size of the media can be selected from a wide range of tried and tested available sizes to suit the influent to be treated and the consents to be achieved.Case studies of BiostyrTM Package PlantThe contract for Shepton Mallet STW is for the design and construction of a new tertiary treatmentstage to meet a tighter consent standard. Flows and loads to the works vary significantly both on adaily and seasonal basis. During weekdays the predominant flow into the works is trade waste but atthe weekends generally only domestic waste is received. The apple pressing season around Octoberand November significantly increases loading to the works.Fig 3 BiostyrTM Package Plant – Shepton Mallet (UK) Fig 4 BiostyrTM Package Plant – Top view - Shepton Mallet (UK)The average daily flow to the BiostyrTM Package Plant is 7,776m3/d, and the maximum hourly flowis up to 489m3/h. The influent water quality and the effluent consents are listed as Table 1.
  • 4. Table 1. Maximum concentrations at average daily flow and final effluent consents (at 95%ile spot) Unit Influent Effluent COD mg/L 91 --- BOD mg/L 26 13 TSS mg/L 38 26 NH4-N mg/L 12.7 4The BiostyrTM Package Plant includes 5 cells, each with a surface of 12m2. The height of media is3m, formed by 3.6mm media. The design filtration velocity is 4m/h, and the maximum velocitycould be up to 9.8m/h. The treatment performance is presented as below. AmmN TSS 50 10 45 9 40 8 concentration 35 7 30 concentration 6 25 5 20 Humus tank outlet TSS 4 15 Biostyr outlet TSS 3 Humus tank outlet AmmN 10 Biostyr outlet AmmN 2 Consent - 26mg/l 5 1 Consent = 4mg/l 0 0 4 4 4 4 4 4 4 4 4 4 4 4 04 04 04 04 04 04 1/1/04 1/15/04 1/29/04 2/12/04 2/26/04 3/11/04 3/25/04 4/8/04 4/22/04 5/6/04 5/20/04 6/3/04 6/17/04 7/1/04 7/15/04 7/29/04 8/12/04 8/26/04 /0 /0 /0 /0 /0 /0 /0 /0 /0 /0 /0 /0 1/ 8/ 6/ 3/ 1/ 6/ 15 29 12 26 11 25 22 20 17 15 29 12 8/2 1/ 4/ 5/ 6/ 7/ 1/ 1/ 2/ 2/ 3/ 3/ 4/ 5/ 6/ 7/ 7/ 8/ sample date sample dateFig 5 Performance Summary – Total Suspended Solids (TSS) Fig 6 Performance Summary – Ammonia N (NH4-N)Table 2. Performance Summary – Annual Results Pre-Biostyr Post-Biostyr Unit TSS AmmN TSS AmmN Average mg/L 21.3 2.7 16 1 Max mg/L 45 9.4 35 4.5 Consent mg/L 26 4After nine months operation trial, the results shows the effluent of Biostyr® Package could meet theconsent at 95%ile spot.2.2 Submerged Aerated Filter (SAFTM)Principle of SAFTM [3]Submerged Aerated Filter (SAFTM) technology introduced by Veolia Water Solutions &Technologies over two decades ago has been further developed to include units to treat bothmunicipal and industrial wastewater from 30 PE upwards, the largest unit currently in operationtreats approx 86,000 PE. The SAFTM is an up-flow bioreactor employing a high efficiency, neutralbuoyancy and plastic media.The SAFTM consists of a containment vessel made in GRP, GCS, coated mild steel, stainless steel orconcrete with internal dividing walls, internal air and water distribution systems, plastic media andinternal support structure. The media provides a large surface area on which the bacteria attachthemselves to grow and live. Wastewater is introduced into the base of the SAFTM unit under themedia support decking. Air is introduced into the SAFTM through a separate diffuser system alsolocated near the base. An air blower supplies oxygen to the SAFTM environment on a continuous
  • 5. basis.The air and water distribution system design is such that it creates a very effective mixing patternwithin the SAFTM. This pattern allows for rapid distribution of the wastewater throughout thepacked media bed. This produces a homogeneous solution in full contact with the entire microbialpopulation for the period of time that the wastewater is in the reactor. The uniform mixing pattern isof key importance in providing a stable environment which has the ability to smooth outfluctuations that may occur in the influent concentrations.The high media voidage eliminates the need for backwashing, thus reducing operating costs andensures minimal disruption of the biological process. Because of the high media porosity, SAFsTMare characterised by high retention times making them ideally suited to both BOD5 removal and thenitrification of wastewater. The neutral buoyancy of the media also simplifies reactor constructionand maximises active biological volume.The SAFTM technology is bearing the following features: Established/robust fixed film technology. Resilience to shock & toxic loads Suitable for below ground, partially buried or above ground installation. Compact footprint Low environmental impact Minimal manpower & energy requirements Simple to operate Low maintenance Low whole life costs Computer software designed to provide accurate sizing and guaranteed effluent discharge qualityFor the package scaled application of SAFTM, VWS has the BioSAFTM Integral Package Plant andthe Modular SAFTM Package Plant.A complete Bio-SAFTM Integral treatment process, supplied in a GRP cylindrical tank supplied in avariety of sizes to treat PE between 30 and 250. Complete treatment process is in a below groundintegral unit. The standard Bio-SAFTM unit consists of 3 compartments: a primary zone for primarysettlement, a SAFTM zone for aerobic fixed film treatment and a humus settlement stage. The unitsare supplied in 1 meter lengths from 7 to 14 meters, sized for transportation in a standard containeror road vehicle. The Bio-SAFTM unit is designed with no internal moving parts and non-clog coarsebubble diffusers and is capable of attaining discharge standards of 20BOD5: 30TSS: 5NH4-N(95%ile).Fig 7 BioSAFTM Integral Package Plant (1) Fig 8 BioSAFTM Integral Package Plant (2)
  • 6. The Modular SAFTM Package Plant is supplied in a rectangular coated or stainless steel tank and isdesigned to be used as part of a separate unit process configuration e.g. PS/SAFTM/HT. Thismodular process unit is suitable for treating PEs up to 800 or in multiples up to 3000 PE. It iscompact and simple to install with minimal disruption to the existing treatment system. The unit isideal for upgrading existing works, for treatment at smaller sites or for emergency treatment duringplant failure, maintenance or upgrading. To optimize performance and provide increased processsecurity the modular SAFTM is capable of attaining discharge standards of 20BOD5:30TSS:5NH4-N (95%ile).Fig 9 Modular SAFTM Package Plant (1) Fig 10 Modular SAFTM Package Plant (2)Case studies of SAFTMThe Glaxo Smith Kline Project is to treat the wastewater from the pharmaceutical manufacturingplant, which contents the high strength fermentation and resin column effluent. The treatmentcapacity of the plant is 86,000 PE, and the treated water is discharged to sea directly. After twoyears of feasibility study and engineering study, Veolia Water Solutions & Technologies won thisproject, worth 15 million Euro. Influent Chemical Sea Balancing Trial Discharge Precipitation and Discharge Tank Tank Clarification TSSr & BOD5rFig 11 Original Process ConfigurationThe original process is shown as Fig 11, having some existing problems, i.e. the balancing tank andsludge handling facilities generated odour, the chemical precipitation and clarification producedchemical sludge with poor dewatering characteristics, and the effluent of the existing process cannotmeet the new EPA discharge standards.The raw water flow and quality is listed in Table 3.Table 3. Influent Design Characteristics Unit Without FBD With FBD Flow m3/d 1,400 1,410 TCOD kg/d 11,160 13,345 TCOD mg/L 8,000 9,465
  • 7. TBOD kg/d 3,720 4,447 TBOD mg/L 2,660 3,145 TSS kg/d 75 638 TSS mg/L 55 452 NH4-N kg/d 135 137 NH4-N mg/L 100 99 Temp ℃ 30 30By laboratory scale bio-treatability studies, the characteristics and variability of wastewater wasinvestigated, the design loading rates and HRT (hydraulic retention time) was optimized and theperformance under shock loadings was checked. Other aspects, such as the residual SCOD fractionand sludge production & dewaterability, were also studied. Influent Balancing Secondary Effluent DAF SAF Tank Clarifier TSSr & BOD5r BOD5r TSSr & BOD5rFig 12 Upgraded Process ConfigurationAccording to the laboratory studies, the upgraded process configuration is shown as Fig 12. Thehydraulic retention time (HRT) of the balancing tank is 5 hours, where coarse bubble aeration andVenturi aerator / mixer are equipped. Odour control facilities and VOC alarm are also set at thebalancing tank. Before the raw water fed into the DAF system, the pH is controlled by dosing acidor alkali. Two sets of IDRAFLOT Flotator are applied, with lamellar packs. Odour control is alsorequired in the DAF system. The SAF system is composed by 2 units in parallel, the size of whichis 16.2m in diameter and 10m in height. The total process volume is 1,185m3, with air scour andeffluent recycle facilities. A dissolved oxygen (DO) analysis was used for control, and odourcontrol is also set in the SAF system.The containments removal performances are shown in the diagrams below (as Fig 13 and Fig 14).The contract successfully took through feasibility study, bio-treatability study, engineering study,installation and commissioning. The project was completed to budget and on time, which was agood industrial reference for SAF technology. 5000 12000 4000 10000 TBOD5 - m g/l 8000 3000 6000 TCOD - m g/l 2000 4000 1000 2000 0 0 18/02/02 20/02/02 22/02/02 24/02/02 26/02/02 28/02/02 02/03/02 04/03/02 06/03/02 08/03/02 10/03/02 12/03/02 14/03/02 16/03/02 18/03/02 18/02/02 20/02/02 22/02/02 24/02/02 26/02/02 28/02/02 02/03/02 04/03/02 06/03/02 08/03/02 10/03/02 12/03/02 14/03/02 16/03/02 18/03/02 Sam ple Date Sam ple Date Influent Final Effluent Design Average Influent DAF Effluent Biotow er Inlet Final EffluentFig 13 BOD5 Removal Performance Fig 14 TCOD Removal Performance
  • 8. 2.3 Pure Moving Bed Biological Reactor (MBBR)The AnoxKaldnesTM biofilm process is patented by AnoxKaldnes and is used in several differentconfigurations and combinations to create optimal solutions for treatment of municipal wastewaters.It utilizes the advantages of activated sludge and previous bio-film systems without being restrainedby their disadvantages.Principle of Pure MBBR [4]The basic idea behind the AnoxKaldnesTM biofilm process is to have a continuously operating, non-cloggable biofilm reactor with no need for backwashing, low head loss and high specific biofilmsurface area. This is achieved by growing biofilm on carrier elements that move along with water inthe reactor.The movement is caused by the aeration in the reactor. The carrier element is made of polyethylenewith a density around that of water and shaped like small cylinders or discs about 9-65 mm indiameter, depending on the application. The filling rate of carriers in the reactor may vary between10 and 67 %, depending on the application. (Left: K1 carrier) (Right: Biofilm ChipTM) Fig 15 Example of carrier mediaThe micro-organisms grow on the carriers as a bio-film. In the biofilm, the micro-organisms arewell protected which makes the process tolerant towards variations and disturbances and evenextreme loads can be handled. With the suspended carriers, the process can be made very compact.The process is also easy to maintain and the amount of active biomass is self regulated and dependson incoming load and hydraulic retention time. Since the carriers are continuously moving, theprocess is insensitive to suspended solids in influent wastewater. Fig 16 On the carriers the micro-organisms grow as a biofilmThe oxygen needed by the micro-organisms in the process is supplied through an aeration gridcovering the bottom of the reactor. The aeration system is a medium bubble one, usually with 4 mmholes. The advantages of this system is that it is maintenance free and because of the presence of thecarriers the way of the air bubbles from the bottom of the tank to the surface is hindered and theefficiency of the medium bubble system is comparable with that of a fine bubble one. The aerationis also keeping the reactor content completely mixed.In order to keep the carrier elements in the reactor, a sieve or grid is placed at the outlet of the
  • 9. reactor, Fig 18. The air agitation is arranged so that the carrier elements are constantly being movedupward over the surface of the sieve. This creates a scrubbing action that prevents clogging. Boththe aeration system and the sieves are designed to work well with the chosen carrier elements.Fig 17: A medium bubble aeration system supplies the Fig 18: Sieves at the outlet to keep the carriers in thebiofilm process with oxygen reactorThe treated wastewater together with the excess sludge formed in the process passes through theoutlet sieves and passes on to the post-treatment step for further treatment and ultimate removal. Ifnecessary, the wastewater influent to the bioreactors will be supplemented with nutrients, N and P,to provide proper conditions for biological degradation and biomass growth.To sum up, pure MBBR technology has the following advantages compared with the traditionalactivated sludge technology: A secondary clarifier is omitted since there is no need for recirculation of biological sludge. Thus, the post-precipitation in connection with a final sludge separation unit (such as ActifloTM, DiscfilterTM and High efficiency settler MultifloTM) could be used directly to enhance the separation of the suspended solids leaving the KaldnesTM biofilm process. Long sludge age. Since the bacteria grow in a biofilm on carriers that are retained in the reactor with sieves or grids, slowly growing bacteria may also be kept in the reactor. Hydraulically robust process. The high flows and shock loads will not cause sludge escaping problems in the KaldnesTM biofilm process. Independent of sludge characteristics. The variation of sludge sedimentation characteristics and the sludge bulking could be completely avoided by application of KaldnesTM biofilm process. Compact process. The KaldnesTM biofilm process often considerably needs less volume than activated sludge process.Case studies of Pure MBBRThe Handeland WWTP (Norway) is a good application for the combination of pure MBBR andActifloTM. The area of Øvre Sirdal is a rural area, characterized by a small residential populationand a great seasonal tourist activity. New hotels and cabins are built, and the municipality expectsan intensive growth in the tourist sector in the coming years. In order to meet the challenge fromthis extensive development, the municipality chose to build a new treatment plant for the wholecommunity [5].As required, a greenfield waste water treatment plant was built. The plant consists of a pumpingstation for incoming waste water, screening, Kaldnes™ MBBR process, and ActifloTM for sludgeseparation. Both biological and chemical treatment units are comprised of two interchangeabletrains. This gives operational flexibility in handling huge variations in flow and load. Sludge isdewatered in a filter press. The treatment process is shown in the flow diagram in Fig 19.
  • 10. Fig 19 Process Flow Diagram of Handeland WWTPTwo trains of MBBR reactors are proposed. The volume of the pure MBBR is 130m3, with a mediafilling degree of 45%, which could be increased to 67% to meet future load. In each reactor,dissolved oxygen is measured, and the aeration capacity is 720Nm3/h.ActifloTM unit serves as a separator, which was design with high load. It only need 1 minute forcoagulation, 1 minute for injection and 3 minutes for maturation. The surface load for settling areais 82m3/h, and the maximum upflow velocity could be up to 125m/h.The treatment results in the year of 2007 shows that the solution with the combination of pureMBBR and ActifloTM worked very well with the variation of raw water characteristics, to ensure agood effluent quality. Fig 20 Treatment results of Handeland WWTPThe application of the combination of pure MBBR and DiscfilterTM was also studied and applied ata municipal wastewater treatment plant at Sjo lunda, Malmo, Sweden. With 10~50mg SS/L in theinfluent, the effluent solid concentrations from the 10 and 18 mm opening DiscfilterTM were2~5mg/L and 2~8 mg/L TSS, respectively, which is comparable to, or better than, the traditionalclarification process, such as settling and flotation[6]. It showed that the disc filtration process
  • 11. worked very well in combination with a post-denitrifying Kaldnes Moving Bed Process.2.4 Membrane Biological Reactor (BIOSEPTM)Principle of Pure BIOSEPTMThe BIOSEPTM process associates biological treatment by activated sludge to membrane filtration.The membranes can be directly immersed in a tank (submerged configuration) or implemented asskids on an external loop. The presence of membranes allows avoiding all problems related to thefinal clarification step and makes the treatment line compact. The use of membranes instead of aclarifier changes the definition of the “soluble” part of the pollution, since a fraction or the totalityof the colloids cannot go through the membrane walls depending on the membrane retentionthreshold. This leads to a significant increase in COD removal in case of a high COD concentrationin the influent, compared to a conventional activated sludge (CAS) process. Furthermore themembrane surface is sized based on the hydraulic load of the plant. The higher the hydraulic load,the more membrane surface is needed. The above two factors make the BIOSEPTM process verycompetitive for treating highly concentrated waste water.Generally, the BIOSEPTM process consists of a pre-treatment stage, one or more activated sludgebasins and membrane modules. The treated water called permeate is sucked up under depression bypumping or by gravity while the excess sludge is withdrawn like in a conventional activated sludgeprocess.The membrane filtration range is usually intermediate between ultrafiltration and microfiltration.The membranes are generally made out of PES (Poly Ether Sulfone) or PVDF (PolyvinylideneFluoride) and may display a broad spectrum in terms of performances depending on the membranesuppliers.Every membrane supplier has its own procedures for installation, commissioning and operation.However they all address the main issue of membrane filtration – membrane clogging – bycontinuously or sequentially insufflating scouring air to prevent the formation of a solid cake layeron the membrane surface that would lead to bad filtration performances and recommending regularmembrane cleanings with chemicals.Case studies of BIOSEPTMIn january 2006, OTV France South got a contract to revamp the existing WWTP of Roussetlocated near the highly touristic area of the Sainte Victoire Moutain. This plant was in operation in2007.The city of Rousset is located in South of France, near Aix en Provences. Due to its populationincrease, the municipality has decided to modify the treatment capacity (to treat up to 12,000 p.e.)by building a new wastewater treatment. Rousset in addition to its microelectronic technical centreis in a middle of a natural environment protected (Arc brook and Sainte Victoire mountain).Therefore, the new plant has to achieve an excellent effluent quality to preserve the naturalenvironment.The capacity of the plant is 12 000 p.e. to treat a daily flow of 1,800 m3/d with a peak flow of 330m3/d. The treatment line is shown in Fig 20.
  • 12. Fig 22 Treatment Line of Rousset WWTPBIOSEP™ consists of an aeration tank in which the membrane modules are located vertically. Twopipes are used to extract the filtered water, a third delivers scour air. The membranes selected forthis project are hollow fibers type, supplied by Puron. The membranes are providing a cut offbetween the micro and the ultra filtration (200,000 Daltons). To prevent any clogging issue, thediameter of the selected membranes has been increased from 1.9 mm to 2.6 mm. This choice willmake the operation of the plant easier. Scheme of membrane support One membrane module Installation of the membrane modules View of the membrane modules in operation Fig 23 Membrane modules and InstallationUsing those membranes, with the influent loads, the quality of the effluent discharged into asensitive area is shown in Table 4.Table 4. The Influent Loads and the Effluent Quality Influent Loads Max Concentration Min Removal BOD5 720 kg/d 5 mg/L -% COD 1440 kg/d 50 mg/L -% TSS 840 kg/d 1 mg/L -% TKN 144 kg/d 5 mg/L 85% TN 15 mg/L 70% TP 36 kg/d 2 mg/L 80%
  • 13. Coliforms Total 500 u / 100 mL 5 log Bacteria - 3 log2.5 Activated Sludge Treatment (AzenitTM)Principle of Pure AZENITTMThe process AZENITTM is the association of a contact tank and a set of tanks treating the carbonand nitrogenous pollution. It is particularly interesting to apply this process which limits theformation of foam and the risks of bulking.The contact zone, which has a role of biological selector, is one agitated but non aerated tank, oflow volume, situated upstream of the biological tanks. The carbon and nitrogenous pollution will be,in preference, treated in a single ditch type tank.The recirculation of sludge from the clarifier maintains a constant quantity of biomass in the tanks.The recirculation flow rate must be controlled to conserve a sludge top layer favourable to the SSconcentration in the clarifier and to perturb settling as little as possible. An excessive retentionperiod, due the most often to over-sizing the clarifier, may bring about an anaerobic state, and inconsequence foaming, degradation of biological treatment and poor clarification. anaerobic Treated water Raw water Anoxic one Biological reactor (aerobic tank) Sludge recirculation Excess sludge Fig 24 AZENITTM Process Diagram Fig 25 AZENITTM PlantThe main differences of AZENITTM process compared to traditional A/A/O process are: Anoxic zone and aerated zone are put in the single biological reactor and aeration is sequenced, fully automatically controlled by both ORP and dissolved O2.
  • 14. Submersible mixer propellers are used. The race track shape tank assures the high inter circulation ratio and avoid the dead corner. Water depth is very deep, about 8 m so we obtain an economy of the land. It improves the process operation affection when the influent loads changes.Case studies of AZENITTMBeijing Beiyuan WWTP has a treatment capacity of 40,000m3/d, located at north suburb of the city.The influent water quality and the effluent criteria are listed in Table 5.Table 5. The Influent Loads and the Effluent Criteria Unit Influent Effluent Criteria BOD5 mg/L 200 < 20 COD mg/L 350 < 60 TSS mg/L 250 < 20 TN mg/L 40 <20 TP mg/L 5 < 1.0Based on activated sludge principle, AZENIT-PTM could provide a complete control of nitrificationand phosphorus removal. AZENIT-PTM process is based on experience gained over many years ofresearch, development and plant M&O. Depending upon the characteristics of raw wastewater,AZENIT-PTM can be used in this plant.The key part in AZENIT-PTM design is that distinct compartments are required for anaerobic zone,and aerated zone. Coarse & Grit & Grease AZENITTM Secondary Disinfection Fine Screen Removal Chamber Biological Tank Clarifier Fig 26 Process Diagram of Beijing Beiyuan PlantThe combination of ditch and propellers presents the following advantages with which a traditionalA/A/O process can not offer: No MLSS recirculation pumping is necessary, however mixer-propellers ensure in fact this function, but with much higher rate, 1000 % against a maximum of 400 % using pumping system.This configuration allows: Low civil and equipment cost, Good effluent quality due to high MLSS recirculation rate, Low maintenance cost due to energy saving (high efficiency of propellers and no MLSS pumping equipment).This is the reason why AZENIT ® was proposed in this project.
  • 15. 3. ConclusionsA range of Veolia’s technologies for small wastewater treatment plants are presented, and therelated case studies have shown that these technologies are suited to decentralized wastewatertreatment systems and could be adopted for use in low-income peri-urban communities [1].These technologies, combined with other compact and effective solutions of Veolia have beenutilised widely in Europe and America. Thanks to the characteristics of these technologies, such ascompact, modular design, high efficiency and easy for operation and maintenance, they are alsovery suitable to the current situations of Asia. The rapid development of manufacture industries inAsia also makes it possible for the localization of these advanced technologies.These affordable but effective wastewater treatment technologies could be applied to meet theincreasing demand for sanitation and has been demonstrated to be a cost-effective and efficient wayto improve environmental health conditions as well as providing opportunities for re-use andresource recovery.References[1] Jonathan Parkinson, Kevin Tayler. Environment and Urbanization, April, 2003, vol. 15, no.1,75-90.[2] BiostyrTM Package Plant, VWS Internal Newsletter, July, 2006.[3] Submerged Aerated Filter, VWS Commercial Brochure.[4] System description of the KaldnesTM biofilm process, VWS Internal Technical Description.[5] Handeland WWTP (Norway), VWS Municipal Case Study.[6] E. Persson, M. Ljunggren, etl. Water Science & Technology, Vol 53, No 12, 139–147.

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