Membrane bioreactor (MBR)  Sewage Treatment System

 When used with domestic wastewater, MBR processes could produce effluent of high quality enough to be discharged to coastal, surface or brackish waterways or to be reclaimed for urban irrigation. Other advantages of MBRs over conventional processes include small footprint, easy retrofit and upgrade of old wastewater treatment plants.

It is possible to operate MBR processes at higher mixed liquor suspended solids (MLSS) concentrations compared to conventional settlement separation systems, thus reducing the reactor volume to achieve the same loading rate.

Recent technical innovation and significant membrane cost reduction have pushed MBRs to become an established process option to treat wastewaters.As a result, the MBR process has now become an attractive option for the treatment and reuse of industrial and municipal wastewaters, as evidenced by their constantly rising numbers and capacity. 

COD removal and sludge yield

Simply due to the high number of microorganism in MBRs, the pollutants uptake rate can be increased. This leads to better degradation in a given time span or to smaller required reactor volumes. In comparison to the conventional activated sludge process (ASP) which typically achieves 95%, COD removal can be increased to 96-99% in MBRs. COD and BOD5 removal are found to increase with MLSS concentration. Above 15g/L COD removal becomes almost independent of biomass concentration at >97%.

 Arbitrary high MLSS concentrations are not employed, however, as oxygen transfer is impeded due to higher and Non-Newtonian fluid viscosity. Kinetics may also differ due to easier substrate access. In ASP, flocs may reach several 100 μm in size. This means that the substrate can reach the active sites only by diffusion which causes an additional resistance and limits the overall reaction rate (diffusion controlled). Hydrodynamic stress in MBRs reduces floc size (to 3.5 μm in sidestream MBRs) and thereby increases the apparent reaction rate. Like in the conventional ASP, sludge yield is decreased at higher SRT or biomass concentration. Little or no sludge is produced at sludge loading rates of 0.01 kgCOD/(kgMLSS d).Due to the biomass concentration limit imposed, such low loading rates would result in enormous tank sizes or long HRTs in conventional ASP.

Nutrient removal

Nutrient removal is one of the main concerns in modern wastewater treatment especially in areas that are sensitive to eutrophication. Like in the conventional ASP, currently, the most widely applied technology for N-removal from municipal wastewater is nitrification combined with denitrification. Besides phosphorus precipitation, enhanced biological phosphorus removal (EBPR) can be implemented which requires an additional anaerobic process step. Some characteristics of MBR technology render EBPR in combination with post-denitrification an attractive alternative that achieves very low nutrient effluent concentrations.

Main treatment unit 
(1) Front pretreatment tank:

 In front of this device is anoxia tank, in one end of anoxia tank set water inlet, another side top set water weir tank and outlet water, can make the sewage stable nature flow into membrane reaction tank, equip floating packing and anoxia sludge, the sludge in anoxia tank HRT is 3-8h, give oxygen by interval, to make acidify,nitration and denitrification function, make the organism gradate translate into inorganics remove.  

(2)MBR bio-reaction tank:

 It has set water inlet in one side, and the immersed flat membrane module set in reaction tank, accommodate activated sludge, around aeration and membrane unit aeration pipeline connect with air blower, the matched collecting pipe in membrane module connect with suction pump, the untreated sewage enter into MBR biochemical reaction tank by water inlet, sewage HRT is 5h in reaction tank.  After degrade by activated sludge in reaction tank, by resistance pollutant flat membrane module, then enter into cleaning water disinfection tank by suction pump. There set sludge lifting pump in aeration, it can lift the surplus sludge to sludge digestion tank interior; there has overflow in reaction tank top, it can make the sewage backflow into tank outside equalize tank; in below side open vent , in order to convenient for tank interior maintenance, cleaning.

 (3) Sludge tank:

 there are set sludge collecting hopper and sludge pipeline in sludge tank bottom, in order to convenient for sludge concentration, set weir water tank in top, there open mud discharge inlet in bottom, rely on static pressure automatic discharge mud.

(4)Cleaning water tank: 

 (5) Operation room: 

 It set 2 pcs air blower in operation room, operate 12h automatic shift 1 time, air blower equip with silencer damping measures; suction pump 2pcs, electric control cabinet 1pc, lighting system; in the top, equip with rain-proof air vent and ventilate convection device.

The above treatment unit integrated in a tank body, electric control cabinet automatic control each power plant operation.