LAUSR

The benefit of biochar as a soil fertility enhancer is well known and are broadly investigated. Equally, many tropical and sub-tropical countries utilize wastewater for irrigation in urban agriculture. To assess the related health risks, we determined pathogen and heavy metal fate associated with biochar application and wastewater irrigation in the urban agriculture of Northern Ghana. Rice husk biochar (20 t ha-1 ), NPK 15:15:15 fertilizer (212.5 kg ha-1 ), and their combinations were evaluated in a field-based experiment. Untreated wastewater and tap water served as irrigation water, and Amaranthus cruentus used as a test crop, grown in wet (WS) and dry (DS) cropping seasons. Irrigation water, soil and vegetables were analyzed for heavy metals, E. coli, faecal coliform, helminth egg and Salmonella spp. Unlike the pathogens, analyzed heavy metals from irrigation water and soil were below FAO/WHO permissible standard for agricultural activities. Wastewater irrigation caused an E. coli concentration between 0.5 - 0.6 (WS) and 0.7 - 0.8 (DS) log10 CFU gFW -1 on vegetables and 1.7 - 2.1 (WS) and 0.6 - 1.0 (DS) log10 CFU gDW -1 in soil. An average log10 CFU gFW -1 of 6.19 and 3.44 faecal coliform were found on vegetables, while in soil, 4.26 and 4.58 log10 CFU gDW -1 were observed in WS and DS respectively. Helminth eggs population were high in wastewater and were transferred to the crops and soil. Biochar did not affect bacteria contamination. Pathogen contaminations on vegetable and in soil were directly linked to the irrigation water with minimal or no difference observed from biochar application. This article is protected by copyright. All rights reserved.