ABSTRACT
Secondary clarifiers are constructed and operated like the primary clarifiers except that they follow a biological treatment process such as a trickling filter or activated sludge. The type of biological treatment they follow dictates how they are operated.
Secondary clarifiers following trickling filters or RBCs are used to settle biological solids that have separated from the media.
Secondary clarifiers following activated sludge processes help settle and clarify the effluent while also providing a concentrated source of return sludge for process control.
Secondary clarifiers may be round or rectangular, and may be designed for natural gravity settling or enhanced chemically aided settling.
Key factors in secondary clarifier operation include the following concepts82:
– Retention time, hours= ( volume, gal ) ( 24 hrs/day ) flow, gallons per day ( inc RAS ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq16.tif"/>
– Surface loading rate, gal/day sq/ft = flow, gallons per day surface area, sq/ft ( w/o RAS ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq17.tif"/>
– Surface loading rate, lbs/day sq/ft = solids into clarifier, lbs/day surface area, sq/ft ( inc RAS ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq18.tif"/>
– Weir overflow rate, gal/day lineal ft = flow, gallons per day weit length, lineal ft ( w/o RAS ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq19.tif"/>
