Evaluation of the performance of Mzuzu Central Hospital wastewater oxidation ponds and its effect on water quality in Lunyangwa River, Northern Malawi

Abstract

Mzuzu Central Hospital wastewater oxidation ponds discharge effluent onto Lunyangwa River, but data on its performance is scant. It was thus imperative to assess the performance in terms of levels of pH, EC, TDS, phosphates, feacal coliforms, biological oxygen demand (BOD5) and total suspended solids (TSS) removal from the influent. Grab water samples were collected from the influent, facultative pond, effluent and upper, point of discharge and downstream of the discharge point. Levels of temperature, pH, EC, TDS were determined on site using HANNA instrument model H19812 pH-EC-TDS meter. Levels of BOD5 were determined using DO meter. Feacal coliforms were determined using dilution method. Nitrates and phosphates were determined spectrophotometrically, whereas TSS was determined gravimetrically. Data was analysed using Minitab version 17. The removal efficiencies of TSS, TDS, E.coli, nitrates and EC were observed to be 46.67%, 59.43%, 96.23%, 6.34% and 59.34%, respectively. Except for E.coli, the performance of Mzuzu Central Hospital Wastewater Oxidation Ponds in removal of all parameter was generally low (i.e < 60%). In addition, the removal efficiencies of pH, temperature, PO43− and BOD were −23.19%, −4.35%, −20.65% and −69.23%, respectively, indicating that regardless of the weak wastewater (BOD5< 200 mg/L) of a raw wastewater collected, the performance of the oxidation is a challenge. Levels of BOD5, fecal coliform, phosphate, and pH, above Malawi Standards specifications for industrial effluents tolerance limits for Malawi in both the effluent and the receiving waters, were indicative of significant pollution resulting from the oxidation ponds, suggesting a pressing need for improvement in wastewater treatment in order to improve the water quality ratings prior to discharge into Lunyangwa River. There is also a dire need for risk communication and public sensitization with respect to the need to boil and filter the water prior to consumption for communities that rely on downstream of the discharge point as their drinking water sources.