Listeria abundance and physicochemical quality of a RW used for irrigation and fish farming in a typical urban settlement in South Africa

Iyasere O. A

Abstract

We evaluated the microbial (listerial) and physicochemical quality of a reclaimed municipal wastewater (RW) used for irrigation and aquaculture in South Africa between August 2007 and July 2008. Listerial density in RW ranged between 9.6 × 103 and 2.8 × 105 cfu/100 ml. pH varied from 6.7 to 7.75 while temperature ranged between 18 and 27°C. Turbidity varied between 1.6 and 19 NTU whereas chemical oxygen demand (COD) ranged from 10 to 965 mg/l. Total dissolved solids (TDS) for RW varied between 288 and 715 mg/l while dissolved oxygen (DO) ranged between 0.14 and 6.1 mg/l. Other parameters recorded the following values after wastewater reclamation: Nitrate (0.27 – 6.8 mg NO3 -N/l); Nitrite (0.12 - 6.3 mg NO 2 - N/l); and Orthophosphate (PO4 3- ) (0.08 – 2.17 mg PO4 3- P/l). Although the physicochemical quality of the RW was generally compliant with recommended standards, its microbial quality disqualifies it for use in agriculture and aquaculture in lieu of the public health implication for farm workers and consumers of the farm produce.