BREWERY AND MUNICIPAL WASTEWATER QUALITY FOR IRRIGATION AND ITS IMPACTS ON SELECTED SOIL PROPERTIES AROUND HARAR CITY, EASTERN ETHIOPIA

Abstract

Wastewater contains a variety of chemical, physical and microbial contaminants which may significantly affect soil properties as well as ecosystem function when used for different purposes such as irrigation. Around Harar city, brewery and municipal wastewater has been in use for irrigating some crops cultivated in the area which may have impacted soil properties. The study was aimed to investigate the impacts of brewery and municipal wastewater (BMWW) on selected soil physico-chemical properties and to characterize its quality for irrigation. Three irrigation sites were selected purposively from Harar city area. The sites were categorized into three groups depending on the application of BMWW and long term application: control (non-irrigated), BMWW irrigated farmland for less than ten years and BMWW for more than ten years. A total of two brewery and municipal wastewater samples were collected to characterize wastewater quality for irrigation. A total of 36 soil samples were collected at depth of 0-20 cm for analysis of physico-chemical of the soil. The brewery and municipal wastewater quality for irrigation analysis showed that pH has moderate level which is prescribe by FAO and biological oxygen demand, chemical oxygen demand and phosphorous concentrations were above the permissible limit of FAO prescription for irrigation quality of water. The results of soil analysis showed that bulk density was significantly decreased (P<0.001) with the long term application of brewery and municipal wastewater and moisture contents and total porosity was significantly increased. The soil electrical conductivity (P< 0.001), cadmium (p < 0.001), lead (p <0.05) available phosphorus (P<0.001), soil organic matter (P< 0.001) and CEC (P<0.001) levels were significantly increased as compared to the non-irrigated condition. Magnesium (Mg2+) was significantly decreased (P<0.001) by wastewater application in irrigated farmland. In conclusion, the brewery and municipal wastewater have considerable impact to soil physicochemical properties. An increase of years of application of brewery and municipal wastewater resulted in significant reduction of BD and Mg2+. The most effective way to reduce/ eliminate the impact of these brewery and municipal wastewater on the soil is to develop and implement an effective wastewater management plan.