Performance of constructed wetlands in the reduction of cadmium in a sewage treatment cum fish farm at Kalyani, West Bengal, India

The distribution pattern of cadmium was investigated in waste stabilization ponds designed for three-step sewage treatment processes. The overall mean concentration of cadmium in water and sludge was reduced by 30% and 33%, respectively, from the inlet of the anaerobic pond to the final outlet of the maturation pond. The level of cadmium in water hyacinth, plankton and fish remained higher in all the samples collected from the anaerobic or facultative pond compared to the last maturation pond. It may be reasonable to conclude that three-step ecological treatments accompanied by physical, chemical and biological processes of the waste stabilization ponds were effective in reducing the load of cadmium from sewage effluents.