Greywater treatment by slanted soil system

Slanted soil system is a low cost, simple system suitable for greywater treatment. Performance of the slanted soil system for greywater was evaluated in light of required water quality for irrigation reuse. Removal rate of particle COD and BDOC, those may cause clogging of irrigation facility, were 94–97% and 88–89%, respectively. LAS removal rates were more than 90% and final concentrations (2.3–3.3mgL−1) were sufficiently lower than proposed target level for irrigation use (8mgL−1). Only fine soil (1–4mm) performed 5 log10 and 3 log10 reductions of Escherichia coli and MS2 phage, while coarse soil could not remove those pathogens. Clogging was observed in fine soil after 3–5 weeks operation, however combination of coarse soil chamber and fine soil chamber could extend it to 8 weeks. Reductions of total COD and LAS were described by 1st order reaction model and reaction coefficient k was described by equation of per area discharged rate.