Effects of adsorption and filtration processes on greywater microbiological contamination and the potential human health risk reduction

Recycling treated greywater (GW) for onsite, non-potable applications can reduce the potable water demand typically used for non-potable purposes. The conventional methods for GW treatment are limited in their ability to remove wide-ranging pollutants that are inexpensive and use low energy. For this reason, effective and low-cost onsite treatment options are in demand. This study examines the effectiveness of sand filtration (SF), granulated blast furnace slag (GBFS), and activated carbon (AC) in the treatment of GW from a residential apartment building in Sharjah, United Arab Emirates. The study relies on four different pilot-scale experimental setups to investigate the effectiveness of SF, AC, and GBFS in treating microorganisms from GW and evaluate the microbial risk reduction using these treatment processes. A quantitative microbial risk assessment (QMRA) approach is used for risk assessment. Results show that GBFS achieves a higher reduction of total coliform (TC) (0.54–2.05 log removal) and fecal coliform (FC) (1.96–2.30 log removal) than AC. SF improves reduction by 0.13–3.39 log removal and 1.11–3.68 log removal for TC and FC, respectively. The study also reveals substantial FC and Escherichia coli risk reduction by SF, AC and GBFS.