66. Treatment of Coke Oven Effluents by Duckweeds Ponds – A Laboratory Scale Study

Duckweeds are small; floating aquatic plants belongs to Lemnaceae, capable to degrade phenol in wastewater. Synthetic wastewater, similar to the characteristics of coke-plant effluents, was prepared in the laboratory, and tested the degradation efficiency in terms of reduction of COD and phenol under different organic loading rate (OLR) at 4 d and 8 d of hydraulic detention time (HRT). Artificial duckweeds ponds were kept in outdoor conditions and meteorological parameters were monitored and used for the estimation of evapo-transpiration rate and degradation of phenol. From the present experiment, it can be concluded that, for phenol concentration of 250 mg/L, 4 d detention is sufficient for the removal of 91% phenol. At higher phenol concentration of 600 mg/L, a detention time of 8 d is essential. If phenol concentration in the effluent exceeds greater than 800 mg/L pre-treatments wastewater is required. A design example for the treatment of low temperature coal carbonization wastewater by duckweeds pond system also given.