Greywater treatment by vermifiltration for sub-Saharan urban poor

Abstract

The treatment of greywater collected from an urban slum area of Ouagadougou, Burkina Faso, by vermifiltration (VF) was investigated using locally available sawdust as bedding material and Eudrilus eugeniae earthworm. The filtration system was made up of layers of sand, and fine and coarse gravel from the top to the bottom, which was spread inside a cylindrical DN200-PVC pipe. The fine sawdust and density of 6370 worms/m2 were added while the same filtration system without earthworms was used as an experimental control. Batch experiments were conducted at ambient temperature, with hydraulic loading rate of 64 and 191 L m−2 d−1. The raw greywater was highly concentrated with biochemical oxygen demand (BOD5) varying from 690 to 2200 mg/L and pH varying from 4.37 to 7.32. The results showed that Eudrilus eugeniae were able to tolerate temperatures above 40 °C and avoided odour and clogging problems inside the filter. The removal efficiencies of BOD5, chemical oxygen demand, total suspended solid, E. coli and thermotolerant coliforms were better in the vermifilter than in the control system. Moreover, the pH at the exit of the system was close to neutral. Therefore, VF could be applied as an alternative low-cost technology to treat greywater for the urban poor in hot climate areas.