Thu, 12 Jan 2012 15:18:22 GMT

Our wastewater utility is in design of a new activated sludge plant, going from lagoon to a nutrient removal process. New system (bio-denipho ditch) will have two clarifiers. Design engineer has designed a RAS line from each clarifier to come together in a box (RAS box), with weir plates at the location each line enters the RAS box to adjust for balancing the sludge flow from each clarifier. After the two lines enter the RAS box one RAS suction line feed the RAS pumps (2 pumps, VFD on each, each sized from 50 - 100% return rate, both operating can achieve 150% return rate). Any opinions out there on whether we should have a dedicated RAS line and dedicated RAS pumps for each clarifier, for example 2 dedicated RAS pumps for each clarifier with a dedicated RAS suction line to each set of pumps? Concern here is ability to balance the sludge flow from each clarifier. Design is such that both clarifiers will be online during operation to provide around 450 gpd/sq ft overflow rate.

Thu, 02 Feb 2012 11:17:05 GMT

You could have seperate pumps etc but it is common practice to bring it the two together with only one set of pumps.

I am sure at times some inbalance exists but it generally works out okay.

regards

TerryF

WEF Discussion Forums : Operation and Maintenance : RAS lines and clarifier balancing