Nutrient Removal Efficiency of Activated Sludge Plants Treating Industrial and Municipal Wastewater in Ghana

Abstract

Discharge of untreated or poorly treated wastewater constitutes a major source of organic compounds to surface water posing serious threats to ecology and human health. The nutrient removal efficiency of three full-scale conventional activated sludge plants treating municipal and industrial wastewater in Ghana was investigated using standard methods. Industrial wastewater treatment plant had generally higher nitrogen removal efficiency (high as 75%) compared to municipal wastewater treatment plants (21%), with no significant differences in removal efficiency observed for phosphorus. However phosphorus removal efficiency was significantly higher (p-value = 0.005) in the wet season than dry season. A strong correlation between nutrient levels for the various plants was observed, with municipal wastewater plants recording generally higher levels. Effluent total nitrogen (TN) values ranged between 16.5 and 53.8mg/L and 29.4 and 71.5 mg/L for the wet and dry seasons respectively, with total phosphorus (TP) values also ranging between 3.23 and 6.57 mg/L and 6.3 and 15.8mg/L respectively. The effluent quality guideline value for nitrogen was missed by one of the municipal plants while all plants missed that of phosphorus. On the basis of these results, there is need for modifications to existing activated sludge plants in Ghana to improve their nutrient removal efficiency.