Assessment of Physicochemical and Metal Concentrations in Wastewater from the Industrial Zone of Cotonou Benin

Abstract

The present study aimed to assess the physico-chemical quality of wastewater(s) in order to better control the flow of various pollutants generated by the industries from the industrial zone of Cotonou. Water samples were collected in triplicate in each collector and analyzed for their nutrient and metal content (Cu2+, Fe2+, Cd2+, Al3+ and Pb2+) and chemical oxygen demand (COD) and a five-day biochemical oxygen demand (BOD5) were carried out by spectrophotometry. The results revealed highly mineralized waters, indicated by average pH (6.97± 0.34), dissolved oxygen (5.16 ± 0.29 mg/L), electrical conductivity (2280.58 ± 263.97 µS/cm) and total dissolved solids (1076.04 ± 51.01 mg/L). The values of COD (482.05± 1.18 mg/L) and BOD5 (291.67 ±2.19 mg/L) were very high, exceeding the standard for industrial wastewater discharge in Benin respectively by 5 and 11 which is indicative of the presence of very poor biodegradable materials coming essentially from industrial discharge in the study area. The concentration of Cd2+, Pb2+ and nutrient salts indicative of eutrophication were relatively low in the collectors. However, the concentration of Al3+ (2.65±0.03 mg/L) and Cu2+ (10.20 ± 0.14 mg/L) were very high with the later cation being four times higher than the wastewater standard in Benin (2.5 mg/L) for the most heavily loaded collectors. In conclusion, the results of this study provide useful insights for implementation of purification system and efficient management of wastewater from industries.