Assessment of the Impact of Discharged Brewery Effluent on a Receiving Body of Water

Abstract

Industrial wastewater entering a water body represents a heavy source of environmental pollution in Nigerian rivers. It affects both the water quality as well as the microbial and aquatic flora. This study was carried out to assess the impact of effluent from Consolidated Brewery on the microbiological and physico-chemical properties of Njaba River. Water and wastewater samples for this study were collected from five different stations and different months (October 2012 to February 2013) along the course of Njaba River. Station 1: Effluent sample alone (from the pipe before contact with the river), station II: upstream 200 m to the point of entry of effluent, station III: the point where wastewater from the consolidated brewery enters the river, station IV: 200 m downstream of station III and station V: 200 m downstream of station IV. The samples were serially diluted (10-fold) and 0.1 ml was plated on Eosin-methylene blue, Nutrient agar and Sabouroud dextrose agar using spread plate method. The organisms were isolated and counted using standard microbiological techniques. The dissolved oxygen and biological oxygen demand were determined using dissolved oxygen meter. The physico-chemical properties were determined using titrimetric and gravimetric method while temperatures and pH of the samples were determined using thermometer and pH meter, respectively. The cations, iron, lead and copper were analyzed using atomic absorption spectrophotometer. A total of eight bacteria and nine fungi were isolated from the water and wastewater samples from Njaba River. The stations displayed varying degrees of bacterial and fungal counts. The highest fungal count was obtained at station two with mean fungal count of 5.2 x 103Cfu/ml while the least was obtained at station three. The result showed a significant difference (P < 0.05) in the mean fungal and bacterial counts at different stations and months. The result of the suspended solid varied from 100 to 2800 mg/l throughout the study period. Station one had the highest amount of dissolved solids (660-1650 mg/l) while least amount was observed at station five (50-165 mg/l). The chemical oxygen demand was highest at station five (150-320 mg/l) and least at station one (16-30 mg/l). The result showed a gradual increase in acidity from station I to V whereas alkalinity was lowest at station V and highest at station I. The result of suspended solid, dissolved oxygen, biological oxygen demand and chloride were not statistically different at different months and stations. There was a significant difference (P < 0.05) in the value of lead, phosphorous and sulphate obtained at different stations and months. The pH values were within weak acid range in all the stations while surface temperature fluctuated between 26 and 33oC during the entire period of study. The results of this study showed that some of the physico-chemical characteristics are within the acceptable limit of World Health Standards while the bacterial isolates from the effluents and receiving water body have the potential to cause water-borne diseases