TREATMENT OF FISHPOND WASTEWATER USING HYBRID CONSTRUCTED WETLANDS IN MINNA, NORTH CENTRAL NIGERIA.

Abstract

Musgola fish farm is an integrated farm located in Bosso Local Government of Niger State, North Central Nigeria. The farm uses large volume of freshwater for the purpose of fish husbandry. Wastewater generated from the fishpond leads to environmental pollution as it contains uningested food, fish dregs, faeces of different classes and chemical constituents. There is therefore the need for a study on environmental impact of these wastewaters and how it can be treated for safe disposal. This study was carried out to characterise the wastewater and thereafter evaluate the effectiveness of constructed wetlands (CWs) to treat it before discharging it into adjacent river. The results of fish pond effluent characterisation showed that the pH of the effluent ranges between 5.7 and 6.84, temperature was between 26 and 27 0C, electric conductivity ranges between 250 and 334 µs/cm, TDS ranges between 232 and 265 mg/L, BOD5 was between 102 and 123 mg/L, NH3 ranges between 1.23 and 1.92 mg/L, and Turbidity was between 9.9 and 11.2 NTU). These data were predetermined to use as baseline information for the wastewater entering the constructed wetlands. The developed hybrid CWs of two planted horizontal and vertical CWs with a corresponding two unplanted horizontal and verticals to act as control. The flow was continuous with calculated hydraulic flow rate of 20 L/day, hydraulic loading rate 15 L/day while hydraulic retention time for horizontal and vertical flow CWs were 5 and 4 days respectively. One way analysis of variance (ANOVA) at 95% significance level was used to examine the performance of the treatment. The treatment efficiency of the systems was calculated as the percentage of contaminant removal as measured from planted horizontal and vertical CWs compared with unplanted horizontal and vertical CWs. The comparison of hybrid CWs displayed removal efficiencies of 90.1 and 89.0 % for BOD5, 44.9 and 58.2% for TDS, 60.7 and 77.7% for TSS, 48.9 and 57.4% for EC, 35.2 and 45.5% for Turbidity. Sacciolepis africana-planted hybrid CWs proved to be more efficient than unplanted wetlands in the treatment of fishpond wastewater. Planted hybrid CWs had final effluent concentrations that comply very well to the discharge limits of WHO and Nigerian FEPA standards. Hence, constructed wetlands is a viable alternative to address many of the water-management problems faced by the fish industry.