Stormwater and lamella settlers: Efficiency and reality

Two settling devices treating rainwater from urban drainage areas and equip ped with secondary sludge treatment were monitored over a period exceeding one year. The two devices differ in their design and in the quantity and qu ality of effluents received. Full analyses over approximately 30 mean sampl es of the intake and discharge effluents allowed judgment of the mean effic iency of pollution control and the reduction in impact of the storm water. The observed settlement was compared to measurements of settling velocity d uring several rainfalls. From analyses of the settled or extracted sludge i t was possible to characterize the pollutants retained in the sludge. Parti cular attention was paid to the functioning and operation of the devices. ( C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.