THE POTENTIAL USE OF ANAEROBIC BAFFLED REACTOR (ABR) EFFLUENT FOR PERI-URBAN HORTICULTURE

Abstract

Currently under investigation by the eThekwini Water and Sanitation is the use of anaerobic baffled reactors (ABR) by local communities to treat wastewater. Studies undertaken at the University of KwaZulu-Natal, South Africa show that ABR effluent has the potential to improve soil nutrient status without adversely affecting soil properties. However, the availability of these nutrients for plant uptake up these nutrients has not been investigated and the effect on crop growth and yield is not known. This study aimed to (i) compare the use of ABR effluent as a fertilizer source and standard inorganic fertilizer recommendations for bean (Phaseolus vulgaris) and Swiss chard (Beta vulgaris) growth and; and (ii) determine the effect of high nutrient concentrations in ABR effluent on bean seed germination and seedling growth. Pot experiments were laid out for each crop species as a 3×3×2 factorial treatment structure using a completely randomized design with the following factors: soil type (3 levels - Inanda, soil from Newlands Mashu (Sepane soil form) and Cartref); Fertilizer application (3 levels - no fertilizer, recommended rate and half the recommended rate); Water (2 levels - ABR effluent and tap water, applied as ‘bucket’ irrigation). Obtained data indicated that Swiss chard plants grown at recommended fertilizer rates using tap water in irrigation did not differ significantly (P>0.05) with respect to dry matter accumulation and leaf area from those irrigated with ABR effluent at recommended and half rates in all three soil types. Bean seeds germinated using ABR effluent showed radicle protrusion earlier than those under tap water; radicles were longer and produced more root mass compared to those germinated using tap water. These findings suggest that the type of crop species and its nutrient requirements, stage of growth and development and the timing of application and soil properties would be important factors to consider when using ABR effluent. High P concentration (mg/L) in the ABR effluent may be associated with increased shoot mass and extensive root growth.