Vermifiltration as a Final-Stage Process for Rural Sewage Purification in China

The performance of a pilot-scale vermifiltration treatment process for municipal wastewater was investigated at hydraulic loadings of 2.4, 4.8, 5.6, 6.7m³/m².d. The results indicated that the removal efficiencies of COD_cr, BOD₅, SS and NH₄-N were in the range of 47.26%~57.55%, 54.78%~59.29%, 62.06%~77.90%, and 21.01%~52.58%, respectively. The average sludge reductions were from 38.2% to 44.7%. The average VSS/SS ratio of the effluent sludge ranged from 44.8% to 48.1%, and the average VFA of the effluent sludge were in the range of 36.9mg/L~39.3 mg/L.Various microorganisms thrived under vermifiltration conditions. Compared to the conventional activated sludge process, the key characteristics of vermifiltration include low capital and operating costs, and simple process management. The characteristics mesh well with the requirements for viable sewage treatment processes for rural settlements in China.