Performance of biochar and filtralite as polishing step for on-site greywater treatment plant

The purpose of this paper is to investigate the performance of biochar and fine filtralite as a polishing filter material in further removing organic matter, phosphorous, nitrogen, turbidity and indicator microorganisms from effluents of a compact greywater treatment plant (GWTP).

A filtration experiment was carried out using columns filled with biochar and fine filtralite as filter material and unfilled column as a control. The effluent from the GWTP was pumped using a peristaltic pump at a rate of 280 l/m2-d and was fed in upward flow into the columns. The quality parameters of the raw greywater, effluents from the GWTP and the polishing columns were studied for six months of operation period.

The results indicate that the process of polishing considerably improved the effluent quality of the system. Biochar performed best in removing organic matter, total N, turbidity and odor. Filtralite was superior in removing P. The contribution of the polishing step in removing total coliform bacteria (TCB) and Escherichia coli (E. coli) was remarkable. Additional log reduction of 2.18, 2.26 and 1.81 for TCB and 2.26, 2.70 and 2.01 for E. coli was obtained compared to the GWTP due to biochar, filtralite and control column, respectively.

This study demonstrates the opportunities for improving the performance of decentralized greywater treatment systems by integrating locally available polishing materials to achieve a better quality effluent.

The present study identifies efficient polishing system for decentralized and compacted greywater treatment system. The recommended polishing materials potentially improve the quality of effluents and add social, economic and environmental values.