title: Testing biological effects of hand-washing grey water for reuse in irrigation on an urban farm: a case study.
abstract: The feasibility of reusing hand-washing grey water contaminated with antibacterial hand-washing liquid for irrigation purposes in an urban farm is explored in this case study. Experiments are carried out to investigate if the quality of this grey water allows for its reuse in agriculture as per the guidelines established by the World Health Organization (WHO). However, there is no guideline to test the biological effect of grey water prior to agricultural use. It is plausible that the antibacterial property of the grey water can harm the soil microbial system and plants when applied to land, even if all other water quality parameters satisfy the WHO limit. We use algae (Chlorella vulgaris) and indigenous soil bacteria as initial plant and soil bacteria indicators, respectively, to test the potential inhibition of the water on plants and soil bacteria. Results show that the chemical oxygen demand (COD) of the grey water is 10% higher than the WHO permissible level, while all other water quality parameters are within the limits after four days of our experimental period. An inhibitory effect is observed in all of the biological tests. However, the inhibitory effect on algae and soil bacteria is not observed after the four-day period. The case study demonstrates a new approach for testing the biological effect of grey water, which can be used in conjunction with the WHO guideline, and provides data for this urban farm to set up a future water treatment system for grey-water reuse in irrigation.
authors.affiliation: Healthy Infrastructure Research Centre, Department of Civil, Environmental and Geomatic Engineering, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Mohammad Zain
authors.initials: MZ
authors.lastname: Khan
authors.forename: Yei Lin
authors.initials: YL
authors.lastname: Sim
authors.forename: Yang Jian
authors.initials: YJ
authors.lastname: Lin
authors.forename: Ka Man
authors.initials: KM
authors.lastname: Lai
mesh_terms: D057914:Agricultural Irrigation; D057919:Biological Oxygen Demand Analysis; D000460:Chlorophyta / Q000254:growth & development; D002947:Cities; D004553:Electric Conductivity; D004755:Enterobacteriaceae / Q000302:isolation & purification; D005240:Feasibility Studies; D006235:Hand Disinfection; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D059027:Recycling; D062065:Wastewater; D060753:Water Quality; D014944:World Health Organization
chemical_list: D009566:Nitrates; D010100:Oxygen; D010758:Phosphorus; D062065:Wastewater