Controlling Benthic Feedback in an Aeration Stabilization Basin

Effluent nutrient residuals in an aeration stabilization basin (ASB) consist of nutrients remaining after biological treatment and nutrients released from sediment in the quiescent zone known as benthic feedback. Both abiotic, mainly temperature, and biologic mechanisms control benthic feedback. Ammonia (NH3-N), orthophosphate (PO4-P), and COD were analyzed on time based increments from three experiments analyzing temperature impact during endogenous respiration, increased bacterial activity, and flow regulation. Results indicate anaerobic bacteria can reduce abiotic benthic feedback through endogenous respiration only at moderate temperatures and are highly susceptible to abiotic mechanisms outside this narrow zone. BOD breakthrough from upstream treatment causes rapid release of NH3-N and PO4-P due to an increase of nitrogen (N) and phosphorous (P) released from the organic matter and a loss of redox stability in the water column. Operation control guidelines can be created to reduce peaks in N and P based on these results.