Physicochemical analysis of wastewater generated from a coating industry in Mauritius

The coating industry is one of the most important consumers of water and chemicals and consequently is a major water polluter in Mauritius. The focus of this study was to characterise wastewater generated by a coating industry in Mauritius. The objectives were to develop a wastewater sampling strategy and to analyse the pollutant parameters as per Mauritian regulations. The wastewater samples were analysed for physicochemical properties and metal abundances over a period of 6 months. The physicochemical parameters analysed were pH, electrical conductivity (EC), true colour, total suspended solids (TSS), biological oxygen demand (BOD₅), chemical oxygen demand (COD), nitrate, phosphate, sulphate and free chlorine. The wastewater samples were also analysed for metal ions such as sodium, potassium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel and zinc. The results of the physicochemical parameters indicated the presence of biologically resistant organic matters in all the wastewater samples with elevated values of BOD₅ and COD, and low biodegradability index, respectively. The coating industry wastewater samples were acidic and saline in nature. Moreover, they presented high concentrations of TSS, free chlorine and sodium ions compared to standard limits promulgated by the Mauritian Government. Spearman's rank correlation matrix with non-linear regression analysis showed significant associations among the measured parameters which were found to have a common origin in the coating industry wastewater. This research will be useful for regular monitoring and setting up an adequate coating industry wastewater treatment for the potential reuse in production processes in Mauritius.