Treatment of dairy wastewater by water hyacinth.

The present study addresses potential of water hyacinth for treating small-scale dairy wastewater to satisfy effluent standards for disposal into public sewers. The batch experiments were conducted on dairy wastewater using reactor with water hyacinth and without water hyacinth. The Chemical Oxygen Demand (COD) was varied from 507 mg/L to 4,672 mg/L and the maximum Hydraulic Retention Time (HRT) adopted was 8 days. The loss of water due to evapo-transpiration and evaporation was also measured. The water hyacinth system performed better when initial COD concentration was maintained less than 1,672 mg/L for six days HRT. The performance of water hyacinth system was more effective than reference by 30% to 45% for COD removal. However, water hyacinth had no significant impact in reducing Total Dissolved Solids (TDS). The evapo-transpiration loss was almost double than the evaporation loss. The first order reaction kinetics was applicable and reaction rate parameters were estimated for various organic strengths of wastewater. The reaction rate parameters for water hyacinth system were three times higher than a system without water hyacinth and also found to vary with initial COD values. Water hyacinth can be adopted to treat dairy wastewater from small-scale dairy effectively for disposal into public sewers.