Microbial contamination of Capsicum annuum irrigated with recycled domestic wastewater treated by vertical-flow wetlands

•Chillies can be grown successfully using wastewater treated by constructed wetlands.•Highest number of Chillies in class A for tap water and an organic growth medium.•Low Chilli numbers correlate well with an inorganic sand-based growth medium.•Overall proportion of bacteriologically contaminated harvest was less than 5%.•No bacteriological contamination of Chillies harvested at a plant height above 50 cm

Due to water scarcity in many arid countries, there is considerable interest in recycling various wastewater streams such as treated urban wastewater for irrigation in the agricultural sector. The aim was therefore to assess if domestic wastewater treated by different wetlands can be successfully recycled to water commercially grown crops. The objectives were (i) to study the effect of irrigation on Chilli (De Cayenne; Capsicum annuum (Linnaeus) Longum Group ‘De Cayenne’) with domestic wastewater treated by wetland compared to tap water (fresh water); (ii) to assess the overall quality and particularly the microbiological contamination of Chilli fruits; and (iii) to determine the persistence of microbial contaminants in the soil irrigated by treated wastewater between September 2013 and September 2014. High yields were associated with tap water and an organic growth medium. No bacterial contamination was detected for fruits harvested from plants irrigated by wetland outflow water. In contrast, fruits harvested from those plants irrigated by preliminary treated wastewater showed high contamination by total coliforms, Streptococcus spp. and Salmonella spp. This was especially the case for fruits, which were located close to the contaminated soil surface. However, findings indicate that vegetable pots receiving wastewater treated with wetlands can be considered as safe compared to those receiving only preliminary treated wastewater.