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).

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 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

2. 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 BiostyrTM 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

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 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 BiostyrTM 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.

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 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.
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 date
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 (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 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

5. 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)

6. 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.
Influent
Chemical Sea
Balancing Trial Discharge
Precipitation and Discharge
Tank Tank
Clarification
TSSr & BOD5r
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

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 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.
Influent
Balancing Secondary Effluent
DAF SAF
Tank Clarifier
TSSr & BOD5r BOD5r TSSr & BOD5r
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.
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 Effluent
Fig 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 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

9. 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.

10. 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

11. worked very well in combination with a post-denitrifying Kaldnes Moving Bed Process.
2.4 Membrane Biological Reactor (BIOSEPTM)
Principle of Pure BIOSEPTM
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 BIOSEPTM
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.

12. 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%

13. Coliforms Total 500 u / 100 mL 5 log
Bacteria - 3 log
2.5 Activated Sludge Treatment (AzenitTM)
Principle of Pure AZENITTM
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.
anaerobic
Treated water
Raw water
Anoxic one
Biological reactor (aerobic tank)
Sludge recirculation Excess sludge
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.

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 AZENITTM
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.
Coarse & Grit & Grease AZENITTM Secondary
Disinfection
Fine Screen Removal Chamber Biological Tank Clarifier
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.

15. 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.