Industrial wastewater pollution and public health implications in the Shinta River receiving brewery and malt processing effluents
摘要
Breweries are highly water-intensive industries that generate substantial wastewater requiring effective treatment prior to environmental discharge, reflecting a broader global challenge where agro-industrial effluents increasingly threaten freshwater ecosystems, public health, and sustainable water resource management, particularly in rapidly industrializing regions with limited treatment capacity. This study presents the first comprehensive assessment of the Shinta River system in Ethiopia, evaluating both physicochemical and microbiological characteristics of effluents from two major agro-industrial sources: Dashen Brewery and Gondar Malt Factory- and offering a rare comparative analysis of their pollution profiles and impacts on a shared receiving water body. Parameters analyzed included temperature, pH, heavy metals, organic load indicators, nutrients, dissolved oxygen, and microbial contamination. Most physicochemical parameters- temperature (22.4–27.4 °C), pH (6.9–9.7), zinc (0.08–0.45 mg/L), iron (0.00–0.065 mg/L), and alkalinity (0–19.5 mg/L) generally complied with WHO and Ethiopian Environmental Protection Authority standards. However, this study uniquely reveals substantial divergence in organic pollution loads between the two industries, with biochemical oxygen demand (BOD) ranging from 11.2 to 239.28 mg/L and chemical oxygen demand (COD) from 39.0 to 409.7 mg/L. Nutrient concentrations, including phosphate (7.5–54.5 mg/L) and ammonia (0.02–3.4 mg/L), frequently exceeded permissible limits, highlighting previously undocumented eutrophication risks in the Shinta River. Dissolved oxygen levels were critically low at wastewater discharge points (0.31 mg/L) but improved downstream following treatment (up to 3.6 mg/L), demonstrating spatial variation in recovery capacity along the system. Microbiological analysis further showed high contamination, with total plate counts of 2.51 × 105 to 3.02 × 106 cfu/mL and detection of pathogenic organisms such as Salmonella and Shigella at multiple sites. While treatment processes reduced microbial loads, this study identifies persistent residual contamination and incomplete removal of organic pollutants, underscoring inefficiencies in current treatment systems. Overall, this work provides the first integrated, multi-source evaluation of industrial wastewater impacts on the Shinta River, establishing a critical baseline for future monitoring and management. The findings demonstrate that effluent discharges from these facilities pose significant environmental and public health risks, and they highlight the urgent need for improved treatment technologies, particularly for organic load reduction, nutrient removal, and effective microbial disinfection to ensure regulatory compliance and protect aquatic ecosystems.