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

AimThis 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. Methods and resultsThe 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 139x10(-2) to 60x10(-3) for Salmonella spp. but did not affect Pd-annual caused by rotavirus (973x10(-1) to 10). Consumption of onions irrigated with treated GW had a median Pd-annual of 125x10(-9) to 12x10(-8) for Salmonella spp. and 496x10(-4) to 437x10(-3) for rotavirus infection, which was 999 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. ConclusionsGarden produce irrigated with GW treated in biochar filter did not display intolerable risks of rotavirusbased gastroenteritis during summer season in the study area given that the produce is harvested 1 to 2days, and washed, before consumption. Significance and Impact of the StudyThis 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.