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 (Biostyr

TM) 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 systems

1. Introduction 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. The decentralized approach offers opportunities for wastewater re-use and resource recovery as well as improvements in local environmental health conditions [1]. 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. The package scaled wastewater treatment facilities are modular design, which are compact, suitable for installation within restricted footprint, high efficiency and easy for operation and 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 Plant

2.1 Biologically Aerated Filter (BAF) package Responding to the demands for compact BAF system, suitable for installation within a restricted footprint, to meet specific biological treatment demands including total nitrogen removal, Biostyr® Package Plant is developed. Principle of Biostyr

TM Package Plant

[2]

The BiostyrTM process consists of upflow filtration through a submerged, floating fine granular polystyrene media (BiostyreneTM) bed. The media is of a small size and uniform shape, thus providing a high specific surface area. In filtration mode the BiostyreneTM beads form a compact floating media bed retained within the units below the filter nozzle floor. The co-current upflow through this floating media bed of the influent together with process air provides an ideal environment for fixed film microorganisms to attach themselves to the BiostyreneTM media. The process and scour air is introduced to the unit through a common air grid located at the bottom of the unit below the suspended media bed. The BiostyrTM Package Plant is suited for all biological treatment applications from carbon removal to tertiary nitrification. However, it is particularly well suited for Total Nitrogen removal, and for post 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

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 treated effluent retained above the filter nozzle floor within the units, thus removing the requirement for backwash pumps. The suspended solids retained with the media bed, together with excess biomass are purged from the unit into a common dirty wash water storage tank. During this washing phase the Biostyrene® media is air scoured using the process air blowers, and washed with the retained treated 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 Biostyr

TM Package Plant

The contract for Shepton Mallet STW is for the design and construction of a new tertiary treatment stage to meet a tighter consent standard. Flows and loads to the works vary significantly both on a daily and seasonal basis. During weekdays the predominant flow into the works is trade waste but at the weekends generally only domestic waste is received. The apple pressing season around October and 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 flow is up to 489m3/h. The influent water quality and the effluent consents are listed as Table 1.

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 4

The BiostyrTM Package Plant includes 5 cells, each with a surface of 12m2. The height of media is 3m, formed by 3.6mm media. The design filtration velocity is 4m/h, and the maximum velocity could be up to 9.8m/h. The treatment performance is presented as below.

TSS

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Fig 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 4

After nine months operation trial, the results shows the effluent of Biostyr® Package could meet the consent at 95%ile spot. 2.2 Submerged Aerated Filter (SAF

TM)

Principle of SAF

TM [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 both municipal and industrial wastewater from 30 PE upwards, the largest unit currently in operation treats approx 86,000 PE. The SAFTM is an up-flow bioreactor employing a high efficiency, neutral buoyancy and plastic media. The SAFTM consists of a containment vessel made in GRP, GCS, coated mild steel, stainless steel or concrete with internal dividing walls, internal air and water distribution systems, plastic media and internal support structure. The media provides a large surface area on which the bacteria attach themselves to grow and live. Wastewater is introduced into the base of the SAFTM unit under the media support decking. Air is introduced into the SAFTM through a separate diffuser system also located near the base. An air blower supplies oxygen to the SAFTM environment on a continuous

basis. The air and water distribution system design is such that it creates a very effective mixing pattern within the SAFTM. This pattern allows for rapid distribution of the wastewater throughout the packed media bed. This produces a homogeneous solution in full contact with the entire microbial population for the period of time that the wastewater is in the reactor. The uniform mixing pattern is of key importance in providing a stable environment which has the ability to smooth out fluctuations that may occur in the influent concentrations. The high media voidage eliminates the need for backwashing, thus reducing operating costs and ensures minimal disruption of the biological process. Because of the high media porosity, SAFsTM are characterised by high retention times making them ideally suited to both BOD5 removal and the nitrification of wastewater. The neutral buoyancy of the media also simplifies reactor construction and 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

quality For the package scaled application of SAFTM, VWS has the BioSAFTM Integral Package Plant and the Modular SAFTM Package Plant. A complete Bio-SAFTM Integral treatment process, supplied in a GRP cylindrical tank supplied in a variety of sizes to treat PE between 30 and 250. Complete treatment process is in a below ground integral unit. The standard Bio-SAFTM unit consists of 3 compartments: a primary zone for primary settlement, a SAFTM zone for aerobic fixed film treatment and a humus settlement stage. The units are supplied in 1 meter lengths from 7 to 14 meters, sized for transportation in a standard container or road vehicle. The Bio-SAFTM unit is designed with no internal moving parts and non-clog coarse bubble 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)

The Modular SAFTM Package Plant is supplied in a rectangular coated or stainless steel tank and is designed to be used as part of a separate unit process configuration e.g. PS/SAFTM/HT. This modular process unit is suitable for treating PE's up to 800 or in multiples up to 3000 PE. It is compact and simple to install with minimal disruption to the existing treatment system. The unit is ideal for upgrading existing works, for treatment at smaller sites or for emergency treatment during plant failure, maintenance or upgrading. To optimize performance and provide increased process security 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 SAFTM

The Glaxo Smith Kline Project is to treat the wastewater from the pharmaceutical manufacturing plant, which contents the high strength fermentation and resin column effluent. The treatment capacity of the plant is 86,000 PE, and the treated water is discharged to sea directly. After two years of feasibility study and engineering study, Veolia Water Solutions & Technologies won this project, worth 15 million Euro.

Fig 11 Original Process Configuration

The original process is shown as Fig 11, having some existing problems, i.e. the balancing tank and sludge handling facilities generated odour, the chemical precipitation and clarification produced chemical sludge with poor dewatering characteristics, and the effluent of the existing process cannot meet 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

Balancing Tank

Chemical Precipitation and

Clarification

Trial Discharge Tank

Influent

Sea Discharge

TSSr & BOD5r

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 30

By laboratory scale bio-treatability studies, the characteristics and variability of wastewater was investigated, the design loading rates and HRT (hydraulic retention time) was optimized and the performance under shock loadings was checked. Other aspects, such as the residual SCOD fraction and sludge production & dewaterability, were also studied.

Fig 12 Upgraded Process Configuration

According to the laboratory studies, the upgraded process configuration is shown as Fig 12. The hydraulic retention time (HRT) of the balancing tank is 5 hours, where coarse bubble aeration and Venturi aerator / mixer are equipped. Odour control facilities and VOC alarm are also set at the balancing tank. Before the raw water fed into the DAF system, the pH is controlled by dosing acid or alkali. Two sets of IDRAFLOT Flotator are applied, with lamellar packs. Odour control is also required in the DAF system. The SAF system is composed by 2 units in parallel, the size of which is 16.2m in diameter and 10m in height. The total process volume is 1,185m3, with air scour and effluent recycle facilities. A dissolved oxygen (DO) analysis was used for control, and odour control 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 a good industrial reference for SAF technology.

Fig 13 BOD5 Removal Performance Fig 14 TCOD Removal Performance

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/l

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Balancing Tank

DAF Secondary

Clarifier

Influent

Effluent SAF

TSSr & BOD5r BOD5r TSSr & BOD5r

2.3 Pure Moving Bed Biological Reactor (MBBR) The AnoxKaldnesTM biofilm process is patented by AnoxKaldnes and is used in several different configurations 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 restrained by 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 biofilm surface area. This is achieved by growing biofilm on carrier elements that move along with water in the reactor. The movement is caused by the aeration in the reactor. The carrier element is made of polyethylene with a density around that of water and shaped like small cylinders or discs about 9-65 mm in diameter, depending on the application. The filling rate of carriers in the reactor may vary between 10 and 67 %, depending on the application.

(Left: K1 carrier) (Right: Biofilm ChipTM)

Fig 15 Example of carrier media

The micro-organisms grow on the carriers as a bio-film. In the biofilm, the micro-organisms are well protected which makes the process tolerant towards variations and disturbances and even extreme 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 depends on incoming load and hydraulic retention time. Since the carriers are continuously moving, the process is insensitive to suspended solids in influent wastewater.

Fig 16 On the carriers the micro-organisms grow as a biofilm

The oxygen needed by the micro-organisms in the process is supplied through an aeration grid covering the bottom of the reactor. The aeration system is a medium bubble one, usually with 4 mm holes. The advantages of this system is that it is maintenance free and because of the presence of the carriers the way of the air bubbles from the bottom of the tank to the surface is hindered and the efficiency of the medium bubble system is comparable with that of a fine bubble one. The aeration is 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

reactor, Fig 18. The air agitation is arranged so that the carrier elements are constantly being moved upward over the surface of the sieve. This creates a scrubbing action that prevents clogging. Both the 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 the

biofilm process with oxygen reactor

The treated wastewater together with the excess sludge formed in the process passes through the outlet sieves and passes on to the post-treatment step for further treatment and ultimate removal. If necessary, 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 traditional activated 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 MBBR

The Handeland WWTP (Norway) is a good application for the combination of pure MBBR and ActifloTM. The area of Øvre Sirdal is a rural area, characterized by a small residential population and a great seasonal tourist activity. New hotels and cabins are built, and the municipality expects an intensive growth in the tourist sector in the coming years. In order to meet the challenge from this extensive development, the municipality chose to build a new treatment plant for the whole community [5]. As required, a greenfield waste water treatment plant was built. The plant consists of a pumping station for incoming waste water, screening, Kaldnes™ MBBR process, and ActifloTM for sludge separation. Both biological and chemical treatment units are comprised of two interchangeable trains. This gives operational flexibility in handling huge variations in flow and load. Sludge is dewatered in a filter press. The treatment process is shown in the flow diagram in Fig 19.

Fig 19 Process Flow Diagram of Handeland WWTP

Two trains of MBBR reactors are proposed. The volume of the pure MBBR is 130m3, with a media filling 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 for coagulation, 1 minute for injection and 3 minutes for maturation. The surface load for settling area is 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 pure MBBR and ActifloTM worked very well with the variation of raw water characteristics, to ensure a good effluent quality.

Fig 20 Treatment results of Handeland WWTP

The application of the combination of pure MBBR and DiscfilterTM was also studied and applied at a municipal wastewater treatment plant at Sjo lunda, Malmo, Sweden. With 10~50mg SS/L in the influent, the effluent solid concentrations from the 10 and 18 mm opening DiscfilterTM were 2~5mg/L and 2~8 mg/L TSS, respectively, which is comparable to, or better than, the traditional clarification process, such as settling and flotation[6]. It showed that the disc filtration process

worked very well in combination with a post-denitrifying Kaldnes Moving Bed Process. 2.4 Membrane Biological Reactor (BIOSEP

TM)

Principle of Pure BIOSEP

TM

The BIOSEPTM process associates biological treatment by activated sludge to membrane filtration. The membranes can be directly immersed in a tank (submerged configuration) or implemented as skids on an external loop. The presence of membranes allows avoiding all problems related to the final clarification step and makes the treatment line compact. The use of membranes instead of a clarifier changes the definition of the “soluble” part of the pollution, since a fraction or the totality of the colloids cannot go through the membrane walls depending on the membrane retention threshold. This leads to a significant increase in COD removal in case of a high COD concentration in the influent, compared to a conventional activated sludge (CAS) process. Furthermore the membrane 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 very competitive for treating highly concentrated waste water. Generally, the BIOSEPTM process consists of a pre-treatment stage, one or more activated sludge basins and membrane modules. The treated water called permeate is sucked up under depression by pumping or by gravity while the excess sludge is withdrawn like in a conventional activated sludge process. The membrane filtration range is usually intermediate between ultrafiltration and microfiltration. The membranes are generally made out of PES (Poly Ether Sulfone) or PVDF (Polyvinylidene Fluoride) and may display a broad spectrum in terms of performances depending on the membrane suppliers. Every membrane supplier has its own procedures for installation, commissioning and operation. However they all address the main issue of membrane filtration – membrane clogging – by continuously or sequentially insufflating scouring air to prevent the formation of a solid cake layer on the membrane surface that would lead to bad filtration performances and recommending regular membrane cleanings with chemicals. Case studies of BIOSEP

TM

In january 2006, OTV France South got a contract to revamp the existing WWTP of Rousset located near the highly touristic area of the Sainte Victoire Moutain. This plant was in operation in 2007. The city of Rousset is located in South of France, near Aix en Provences. Due to its population increase, 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 centre is 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 natural environment. 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 330 m3/d. The treatment line is shown in Fig 20.

Fig 22 Treatment Line of Rousset WWTP

BIOSEP™ consists of an aeration tank in which the membrane modules are located vertically. Two pipes are used to extract the filtered water, a third delivers scour air. The membranes selected for this project are hollow fibers type, supplied by Puron. The membranes are providing a cut off between the micro and the ultra filtration (200,000 Daltons). To prevent any clogging issue, the diameter of the selected membranes has been increased from 1.9 mm to 2.6 mm. This choice will make 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 Installation

Using those membranes, with the influent loads, the quality of the effluent discharged into a sensitive 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%

Coliforms Total 500 u / 100 mL 5 log

Bacteria - 3 log

2.5 Activated Sludge Treatment (AzenitTM) Principle of Pure AZENIT

TM

The process AZENITTM is the association of a contact tank and a set of tanks treating the carbon and nitrogenous pollution. It is particularly interesting to apply this process which limits the formation of foam and the risks of bulking. The contact zone, which has a role of biological selector, is one agitated but non aerated tank, of low 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 SS concentration in the clarifier and to perturb settling as little as possible. An excessive retention period, due the most often to over-sizing the clarifier, may bring about an anaerobic state, and in consequence foaming, degradation of biological treatment and poor clarification.

Fig 24 AZENITTM Process Diagram

Fig 25 AZENITTM Plant

The 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.

Sludge recirculation

Anoxic one

Biological reactor (aerobic tank)

Treated water

Raw water

Excess sludge

anaerobic

� 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 AZENIT

TM

Beijing 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 < 1.0

Based on activated sludge principle, AZENIT-PTM could provide a complete control of nitrification and phosphorus removal. AZENIT-PTM process is based on experience gained over many years of research, 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.

Fig 26 Process Diagram of Beijing Beiyuan Plant

The combination of ditch and propellers presents the following advantages with which a traditional A/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.

Coarse &

Fine Screen

Grit & Grease

Removal Chamber

AZENITTM

Biological Tank

Secondary

Clarifier Disinfection

3. Conclusions A range of Veolia’s technologies for small wastewater treatment plants are presented, and the related case studies have shown that these technologies are suited to decentralized wastewater treatment 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 been utilised widely in Europe and America. Thanks to the characteristics of these technologies, such as compact, modular design, high efficiency and easy for operation and maintenance, they are also very suitable to the current situations of Asia. The rapid development of manufacture industries in Asia also makes it possible for the localization of these advanced technologies. These affordable but effective wastewater treatment technologies could be applied to meet the increasing demand for sanitation and has been demonstrated to be a cost-effective and efficient way to improve environmental health conditions as well as providing opportunities for re-use and resource 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.