Comparative Performance Studies of Macrophyte and Algal Ponds Using Medium Strength Sewage

The potential of water lettuce (Pistia stratiotes ), duckweed (Spirodela polyrhiza ), and algal (natural colonization) pond systems to treat domestic wastewater for the removal of faecal bacteria ( Escherichia coli , coliforms, Salmonella , other enterobacteria and enterococci), organic matter and nutrient loads were evaluated for a period of 12 months in waste stablisation ponds operating in series of four for each treatment system. Biomass yield and protein content of macrophytes in the ponds were measured. When macrophytes and algae were visibly healthy, (performance was at its peak) an 8week intensive measurements of environmental conditions were determined at various depths (0.10m, 0.35m and 0.63m) in each pond of all 3-pond systems. Faecal bacteria were determined in the effluent from each pond in series. Neutral conditions and low DO concentrations were associated with the macrophyte ponds. The algal ponds had high DO concentrations. Removal of E. coli, Salmonella and other enterococci were the same in all three systems with no significant (p