Membrane Bioreactor (MBR)

Membrane Bioreactor Model Diagram 1

Membrane Bioreactor Model Diagram 2

1.  The sewage from the building  shall be collected and made available by gravity/pumped sewer mains at the treatment plant. The treatment plant is proposed to be installed.

The functioning of the complex is around 24 hrs. Since, the plant needs to be operated continuously; the design of the treatment system will be on 24 hours basis. The water usage for this complex is mainly for domestic usage, such as for the bath rooms, toilets, food court and for drinking.

Sewage treatment capacity:

Total water quantity would be 150 m3/day based on 100% utilization factor.

Sewage Quality:

Taking in to consideration the type of occupation in a household atmosphere, the organic loading is mainly from toilets and from the kitchens. For such kind of occupation the BOD of the wastewater varies from 200 to 400mg/lt. Hence an average BOD load of 350mg/lt considered for design of the system. The characteristics of the sewage would be like that of domestic effluent and the expected wastewater characteristics are given below.

Design Basis

Inlet Quality

pH                                                        :           7.5 – 8.5
BOD                                                     :           250 - 300 ppm
COD                                                     :           400 - 500 ppm
Total Suspended Solids                                    :           150 – 200 ppm
Oil & Grease                                         :           < 20 ppm

  • The inlet quality indicated is typical of domestic sewage.

Outlet Quality

pH                                                       :           7.0 – 9.0
BOD                                                    :           <   5  ppm
COD                                                    :           <  20  ppm
Total Suspended Solids                  :           NIL
Turbidity                                              :           < 15 NTU
The treated water should be clear, colorless, odorless and shall be free from pathogenic organisms. The plant is designed to meet the quality requirement for toilet flushing and for gardening.

Process Details

Bar Screen:

Raw sewage from the source is usually received into the bar screen chamber by gravity. Screen provided will remove all floating and big size matter such as plastic bottles, polythene bags, glasses, stones, etc., which may otherwise choke the pipeline and pumps.

Oil and Grease Trap (Civil Construction)

If the sewage generated includes maximum quantity from kitchen and canteen, there is a possibility of higher concentrations of oil and grease in the raw sewage.  It needs to be removed before biological treatment as it otherwise may cause problems for biological treatment. Usually, a small civil construction tank with a baffle wall and slotted oil pipe skimmer is provided. The oil and grease removed by gravity floats to the surface, which is removed by the oil skimmer (by client).

Equalization Tank (Civil Construction)

Usually, sewage generation is more during morning hours and evening hours. Visually no sewage is generated during night hours. Any biological system needs constant feed for bacteria to work efficiently. Hence, it is important to put an equalization tank to collect the excess flow during peak hours and feed sewage in lean hours. A typical equalization tank has a capacity of 8 – 10 hours of average flow rate. The tank is generally of civil construction by client.

 Provision of air grid is to be made for thoroughly mixing the sewage to make it of homogenous quality and to keep the suspended matter in suspension and to avoid septic conditions.

Alternatively recirculated by pumping through an ejector. In this case the feed pump is designed in such a way, partial flow is send back to equalization tank through an ejector. The ejector sucks air through the nozzle and mixing air with raw sewage homogenously.

Transfer of Sewage

Orion’s scope starts from transfer of sewage from Equalisation Tank to MBR tank.  The distance of transfer should not exceed beyond 5 meter.  The transfer pump can be either submersible or non-submersible type for this application. However Orion has considered centrifugal non-submersible type.  The layout shall be as per Orion standard.

  • The pump should not run dry and Client to ensure sufficient sewage is available in the Equalisation Tank.


2.1 MBR System

We are proposing sewage treatment plant with state-of-the-art membrane separation technology called asMembrane Bio-Reactor (MBR) which can produce very good quality with highest possible bacterial reduction without adding any chemicals.  MBR (Membrane Bio Reactor) is the latest technology in wastewater treatment. MBR has many advantages such as higher quality of treated water, smaller space for installation and easier operation compared to conventional activated sludge process.


Designed to produce high quality treated water from wastewater the Membrane Bio Reactor (MBR) is among the latest technologies in biological treatment.

The characteristic of the MBR process is the use of revolutionary submerged Ultrafiltration membranes in the biological process water tank, so as to produce high quality permeate from domestic sewage, primary and secondary waste water, cooling tower blow down etc. The  MBR is also ideal for retrofitting/augmenting capacity/quality of existing wastewater plants.

The MBR can handle very high sludge concentrations in the aeration tank because of which the size of the aeration tank reduces four to five fold.  As the membrane acts as a fine filter, it does not require any further treatment using sand filters, activated carbon filters, etc. The MBR is available in standard and customized modules.

 Activated sludge in the aeration tank is clearly removed by the flat sheet type submerged membrane. The membrane module consists of housing, aeration diffuser, permeate water manifold and membrane elements. The membrane element consisting of flat sheet membranes sandwiching a support panel is set up vertically. Feed water including activated sludge is filtrated by flat sheet membranes with pore size of 0.1 micron meter. The air bubbles supplied from the bottom of the membrane elements continuously scour off cake of activated sludge accumulated on the membrane surface. This is continuous filtration operation. The air bubbles are also used for the biological reaction to decompose organic substances included in the raw sewage. 



The material of the membrane is PVDF (Poly vinylidene fluoride). PVDF is fluorine polymer, which has high stability for chemicals and good physical strength. The form of membrane is fibre reinforced flat sheet membrane. The membrane has small and uniform pore size. Therefore, the rejection property of this membrane is excellent. Almost all particles with sizes more than 0.1 micron meter can be removed effectively using this membrane.

Treated Water Collection Tank:

The treated water collection tank can be of civil construction by client in case required.


The sludge from the MBR tank to be removed from the bottom of the tank by client and transferred to Sludge Drying Bed (SDB) either by gravity or through pump depending on site condition.  Before starting the desludging, shut off the aeration for 30 minutes and allow the sludge to concentrate at the bottom. After concentration, the bottom sludge valve can be opened to drain the required quantity of sludge.

Alternate Options:

  1. For system with flow rates up to 300 m3 / day, centrifuge can be an option.
  2. Filter Press (Manual System) can also be offered for small capacities
  3. Filter press (Automatic System) / Centrifuge is recommended for ease of operation for all the models.


1          Effluent transfer Pumps:

  • The pumps shall be of Non-clog, open impeller, preferably with a cutter type impeller. Always duty and standby pumps shall be offered.
  • The particle handling size shall not be less than 40-50mm.        
  • The pump shall of submersible type / foot mounted
  • The pump shall be of easy withdrawal type from the collection tank for cleaning / maintenance.
  • The piping system from the pump to the top of the tank will be flexible if submersible pump is selected. Helical wound plastic with suitable flange mounting for easy assembly / disassembly.
  • The pumps shall be provided with rope for lowering / raising the pump. Suitable pulley / lifting arrangement shall be provided for this purpose
  • The pump shall have float-operated switch for automatic ON/OFF operation.
  • Each pump shall be provided with a flow control valve of Ball / Butterfly type.
  • The valve shall be placed in such a way that the operator can easily access it.
  • The centerline elevation of the valve shall not be less than 1000mm and not more than 1700mm from the finished floor level.
  • The piping system connecting the pump to aeration tank shall be HDPE 6kg class of not less than 90mm OD.
  • The piping shall be neatly clamped to the wall or properly supported and no overhang that will deflect the piping is allowed.
  • All termination shall be flanged with bolted connection.
  • All bolts used in this plant would be of GI coated.
  • All bolts shall be applied with a coat of grease before assembling.
  • The nut and the extended threads shall be applied with a coat of grease to protect from atmospheric corrosion.

2          Air Blower:

  • The air blower shall be of Twin lobe type (roots blower).
  • Always duty and standby blowers shall be provided.
  • The blower shall have silencer at the suction and discharge side.
  • The delivery line shall have a dead weight safety valve, a non return valve and a pressure gauge.
  • The pressure gauge shall have isolating valve.
  • A drain line shall be provided in the point with isolating valve.
  • The capacity of the air blower shall be at least 120% of the exact air quantity required for the aerobic reactor to meet fluctuation in wastewater characteristics.
  • The blower pressure shall not be less than 0.36kg/cm2 OR to suit the tank depth.
  • The speed of the blower shall not be more than 1200 RPM
  • The blower pipeline shall be liberally sized, so that the pressure drop across the piping is minimized.
  • The air piping shall be GI class B. The air line for the diffusers shall be bifurcated in to three to four section. Each section shall have anisolation valve.
  • The isolating valves shall be laid out neatly and provided at height not more than 1600mm from floor level.
  • The air header inside the aeration tank can be of HDPE / Rigid PVC of 10kg class or GI Class B.

3          Air Diffuser Membrane:

  • The air diffuser shall be of high quality EPDM rubber & air flow rate shall not be more than 7cfm /sft of diffuser area
  • There shall be at least 5500Its slits per foot of length.
  • The dimension of the diffusers shall be 90mm and the length shall not be less than 1000mm.
  • The end clips should be SS construction. Below the end clips a belt of 1mm thick rubber to be placed and the clip is fixed over it. This would avoid a deep indentation on the membrane diffusers.
  • The layout of the diffusers shall be such that, there won’t be any dead spot in the aeration tank.
  • The diffusers shall be laid out in such a way that this forms 3 to 4 independent sections.
  • Each section shall receive independent air supply through a control valve. The header shall be placed at least 200 mm above the floor level and shall have support at the appropriate distributors

4.                     Sludge Transfer Pumps:

  • Two Nos. non-clog pumps of 5m3/hr at 10mts head shall draw the sludge from the settling tank hopper and transfer to the sludge storage tank.
  • The suction line shall not be less than 80mm dia.
  • A flushing line shall be provided for flushing the suction pipe in case of clogging.
  • An isolation valve shall be provided for the suction line puddle pipe connected to the tank.

5.         Sludge Storage:

  • The sludge storage tank shall be provided with adequate air diffusers to keep the sludge in aerobic condition and that it will not turn septic.
  • Minimum air quantity is envisaged for this purpose.
  • A separate airline is taken from the main air header with a control valve to adjust the air- flow rate.

6.Sludge Disposal:

  • Since the plant is constructed in a basement, it is not possible to have     conventional sludge decanting system.
  • The sludge decanting system envisaged is through a filter press. The quantum of sludge generated shall be taken as 50 % BOD load and other non-biodegradable suspended solids load.
  • The system shall be designed for once in a day operation to a maximum of twice in a day operation. Since opening, cleaning and handling decanted sludge in a basement system will be difficult
  • The approximate sludge quality as dried out would be30kgs. The filter press cake holding capacity shall not be less than 35lts

7. Chlorination:

  • In order to disinfect the treated water, sodium hype chlorite solution has to be dosed. The dosage shall be 8 – 10 mg/ltr. This dosage will be directly dosed in to the clarified water tank and the turbulence created by the air diffusers provided shall ensure complete mixing.

8.         Filter Press & Accessories:

  • Two Nos. Screw pumps of 2m3/hr at 40mts head shall draw stored sludge in sludge storage tank and it feed to the filter press.
  • The filter press shall be of PP molded construction complete with accessories like filter cloth, Hydraulic closing mechanism and withdrawing mechanism. 
  • The filter press shall have suitable leg support such that a ground clearance of at least 600mm is available for placing the pallets for sludge collection.
  • A drain sump and a pump shall be provided with a standby for conveying the spillage and the drippings from the filter press. The excess water shall be returned back to the collection tank by this pump.


  • Inner reinforcing structure covered with a composite polymer outer layer
    • Pore Size:
    • 0.04 micron (average)
    • 0.1 micron (maximum)
  • Strong: Single fiber can hold over 50 kg
  • Robust: Can operate with < 1.0 mg/L TSS (DW) to 50,000+ mg/L MLSS (sludge thickening)
  • Durable: Over 99% of modules ever installed are still in service (first membrane installed in 1993)
  •   Ultra-filtration (UF)
  • Outside-in Flow
  • Reinforced Hollow  Fibre
  • Immersed, shell-less module
    • Immersed,hollow-fiber
    • Outside-in filtration
    • Vacuum-driven operation (-0.15 to -0.35 kPa filtration, -20 kPa backwash)
    • Inner reinforcing structure covered with a composite polymer outer layer
    • Different pore sizes available in the range from 0.04 to  0.1 µm
    • 1.9 mm OD - 0.9 mm ID
    • Hydrophilic neutral, oxidant tolerant,chlorine-resistant polymeric membrane, compatible with coagulants & PAC
    • Air bubbling induces turbulence to keep membrane clean
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