Microbial and physicochemical quality of an urban reclaimed wastewater used for irrigation and aquaculture in South Africa

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.