Recycling of domestic wastewater treated by vertical-flow wetlands for watering of vegetables

Abstract

The aim was to assess if domestic wastewater treated by different vertical-flow wetlands can be successfully recycled to water commercially grown crops. The growth of both Sweet Pepper (California Wonder; cultivar of Capsicum annuum Linnaeus Grossum Group) and Chilli (De Cayenne; Capsicum annuum (Linnaeus) Longum Group 'De Cayenne') fed with different treated and untreated wastewater types were assessed. The overall growth development of Sweet Peppers was poor due to the high concentrations of nutrients and trace minerals. In contrast, chilies did reasonably well but the growth of foliage was excessive and the harvest was delayed. High yields were associated with tap water and an organic growth medium, and a wetland with a high aggregate size, leaving sufficient space for biomass. Low fruit numbers correlated well with inorganic growth media and irrigation water contaminated by hydrocarbons. Findings indicate that nutrient concentrations supplied to the Chillies by a combination of compost and treated waste water are usually too high to produce a good harvest. However, as the compost is depleted of nutrients after about 8 months, the harvest increased for pots that received pre-treated wastewater. Findings will lead to a better understanding of the effects of different wetland treatment processes.