Abstract:
Lower bounds for extraction of pollutants from sewage are investigated for the case of four floating aquatic macrophytes, water hyacinth (Eichhomia crassipes), water lettuce (Pistia stratiotes), salvinia (Salvinia rotundifolia) and water primroses (Ludvigia palustris). It is shown that lower bounds of biochemical oxygen demand (BOD), 1.3 mgL-1, chemicaloxygen demand (COD), 11.3 mgL-1, total suspended solids (TSS), 0.5 mg1:1, turbidity 0.7 NTU, ammonia 0.2 mg1:1, and phosphorus 1.4 mgl:' can be established for sewage purification with water hyacinth, and SOD, 1.8 mgL-1, COD, 12.5 mg1Z1, TSS, 0.5 mg1:, turbidity, 0.9 NTU, ammonia, 0.2 mgt:', and phosphorus 1.6 mg1.-1 with water lettuce. These lower bounds were reached in 11-17 days of experiments that were performed on diluted sewage with reduced initial contents of the tested water quality indicators. As expected, water hyacinth exhibited the highest rates and levels of pollutants removal, thereby producing the best lower bounds of the water quality indicators. Given their initially low levels, the BOD was further reduced by 86.3%, COD by 66.6%, ammonia by 97.8% and phosphorus by 65.0%, after 11 days of a batch experiment. The capacity of aquatic plants to purify dilute sewage streams opens new options for their application in the water treatment industry.
