Quality of greywater treated in biochar filter and risk assessment of gastroenteritis due to household exposure during maintenance and irrigation.

Abstract

This study evaluated treatment of greywater (GW) by a biochar filter in Jordan and assessed the annual risks of infection (Pi-annual ), annual risk of disease (Pd-annual ) and disease burden (in disability-adjusted life years; DALYs) of gastroenteritis caused by Salmonella spp. and rotavirus due to ingestion of GW during system maintenance and consumption of green onions irrigated with treated and nontreated GW. The biochar filter efficiently removed 93% of biochemical oxygen demand (BOD5 ) and 85% of solids, while removal of Escherichia coli was insignificant. Treatment of GW decreased the median Pd-annual due to ingestion of GW from 1·39×10-2 to 6·0×10-3 for Salmonella spp. but did not affect Pd-annual caused by rotavirus (9·73×10-1 to 1·0). Consumption of onions irrigated with treated GW had a median Pd-annual of 1·25×10-9 to 1·2×10-8 for Salmonella spp. and 4·96×10-4 to 4·37×10-3 for rotavirus infection, which was 99·9 and 90% lower, respectively, than the risk when consuming onions irrigated with nontreated GW. The highest risks of gastrointestinal disease were thus associated mainly with direct ingestion of GW when maintaining the system. Garden produce irrigated with GW treated in biochar filter did not display intolerable risks of rotavirus-based gastroenteritis during summer season in the study area given that the produce is harvested 1 to 2days, and washed, before consumption. This study contributes to scientific-based knowledge on the suitability of biochar filters for onsite greywater treatment and confirms the microbial safety of recycling treated greywater for garden irrigation.