Membrane bioreactors (MBR) are becoming increasing popular in industrial wastewater treatment due to the ability of the process to produce a high quality purified water suitable for reuse in a relatively small foot print.
The basis of OVIVO MBR Technology® is the high quality proven membrane that requires minimal cleaning with an exceptional life span. Typically the permeate from the OVIVO MBR Technology® process is < 5:5:5 BOD:SS:ammonia and free of pathogens, viruses and bacteria.
OVIVO MBR Technology® process employs simple flat sheet membrane panels housed in stainless steel units and aerated by a coarse bubble system below each unit.
A series of these membranes are submerged within an activated sludge treatment tank. The aeration necessary for treatment of the liquors also generates an upward cross-flow over the membranes; essential to keep almost eliminate fouling of the filtration surface. An advantage of this design is that the membrane panels are securely retained and do not touch or abrade each other whilst the units also act as a flume to ensure effective tank mixing and even distribution of the biomass.
The membrane panels are manufactured with a pore size in the range of 0.1 to 0.4 microns which in operation becomes covered by a dynamic layer of protein and cellular material. This further enhances the effectiveness of this filtration performance by providing an effective pore size of less than 0.01 microns, which is in the ultra filtration range.
The OVIVO membrane bioreactor treatment produces a high quality disinfected effluent. The incoming wastewater often only requires screening and de-gritting prior to entering the membrane bioreactor tank although in some industrial applications the use of an OVIVO dissolved air flotation system to reduce the load often is an economical primary stage of treatment.
The hydraulic flow determines the required number of membrane units. Each membrane unit may contain up to 400 flat sheet membrane panels housed within a rectangular box, together with an integral aeration system in the bottom section of the unit.
Treated effluent is removed from the membrane units using gravity head (typically 1 – 1.2 m), or a pumped suction operation can be utilised.
Membrane Bioreactor Technology has a number of inherent advantages. The system does not require flocs to be formed to remove the solids by settlement and therefore the biomass can operate at very high levels of MLSS, generally in the order of 12,000-18,000 mg/l, and as high as 22,000 mg/l. This high concentration enables a low tank volume and a long sludge age to be utilised, which substantially reduces sludge production.
Operating at such high MLSS levels also significantly reduces the reactor size when compared to other more traditional secondary biological processes.