Roles of baffles in waste stabilization ponds

Performance of baffles in waste stabilization ponds (WSP) comprising laboratory-scale ponds with different number of baffles was evaluated. This study was aimed at promoting waste stabilization ponds practice for wastewater treatment in tropical countries by reducing the land area requirement through the use of baffles which increased the biofilm and biomass concentrations. The experiments started with the tracer study to find out the hydraulic characteristics of each pond. It was shown that the dispersion number decreased with increasing flow length and number of baffles, which indicates more plug flow conditions. The deviation of actual HRT from theoretical HRT was computed and the flow pattern suggested the existence of an optimum spacing of baffles in baffled waste stabilization pond (BWSP) units. The investigations by feeding with synthetic wastewater further revealed that more than 65% TN and 90% NH3-N removal were achieved at HRT of 5 days in 6-baffled pond which corresponds to the specific area of 35.20 m(2)/m(3). TN and NH3-N removal was increasing with number of baffles in the BWSP units. COD removal increased with higher number of baffles with its maximum removal efficiency at 6 baffles. The computed COD removal encompassed first-order reactions of both suspended and biofilm biomass was higher than that without the biofilm biomass activity and agreed well with the observed data. Compared with normal WSP, BWSP gave higher TN, NH3-N and COD removal. The effluent SS concentrations from 6 baffled-pond were less than 20 mg/l at HRT of 3 days. (C) 1997 IAWQ. Published by Elsevier Science Ltd.