Patent ID: 7476322

Claim:
A process for treating effluent in a sequenced membrane batch reactor (SMBR) comprising; (a) providing a sequenced batch reactor having a biological section and a membrane filtration section; (b) treating the effluent in the biological section by (i) passing the effluent continuously into a biological treatment tank provided with at least one transverse baffle across the tank; (ii) dividing the tank into a first portion adjacent the inlet and a second portion remote from the inlet, wherein the volume ratio of the first portion to the second portion is between 1:10 to 1:3, the first portion having dimensions that enable operation with sludge having biological activity measured as oxygen uptake rate in units of milligrams of oxygen per gram of mixed liquor suspended solids per hour of up to 300, and a solids content of up to 15 pounds of biological solids per square foot of vessel floor area; (iii) aerating and mixing the effluent at least in the second portion of the tank; (iv) ceasing the aeration and mixing to allow sludge in the second portion to settle, while still allowing effluent to enter the tank through the inlet; (c) removing the treated effluent in the filtration section by: (i) providing the membrane filtration section with one or more ultrafiltration or microfiltration membrane assemblies submerged in mixed liquor at ambient pressure; (ii) drawing filtrate through the membrane assemblies; and (iii) providing air bubble scouring of the membrane assemblies only during periodic backwash cycles of the filtration system, and not during filtration cycles, wherein the air bubble scouring provided during the backwash cycle has a duration of 1/12 to 1/40 of the filtration time; and (d) repeating the aerating, settling and removing steps to treat additional effluent.