Industrial Wastewater Loads and Pretreatment Performance of Beverage Industries Discharging to Mbeya Municipal Waste Stabilisation Ponds

Industrial wastewater is a growing threat to municipal Waste Stabilisation Ponds (WSPs) in rapidly urbanising Sub-Saharan cities. This study evaluated the pretreatment efficiency and quantified pollutant loads from three major beverage industries—Tanzania Breweries Limited (TBL), Coca-Cola Kwanza, and Pepsi—that discharge into the Kalobe WSP in Mbeya, Tanzania. Weekly grab samples were collected over a one-month period (n = 12 per industry), and physicochemical parameters, including BOD₅, COD, TSS, nutrients, and pH, were analysed following Standard Methods. Daily pollution loads (kg/day) were calculated from measured flows and concentrations, and statistical differences were tested using one-way ANOVA and Pearson correlation at a 95% confidence level. Results showed significant variation in wastewater quality among the industries (p < 0.05). In terms of treatment efficiency, Coca-Cola consistently maintained the lowest pollutant concentrations, demonstrating effective pretreatment and compliance with national standards. TBL recorded elevated suspended solids due to brewing by-products, while Pepsi exhibited the poorest pretreatment performance, discharging the highest organic loads (BOD: 124.81 kg/day; COD: 245.46 kg/day) despite moderate flow. Collectively, Pepsi accounted for 71% of BOD and 76% of COD loads entering the WSP, underscoring that industries with insufficient pretreatment disproportionately stress municipal systems. The findings underscore the urgent need for targeted upgrades to Pepsi’s pretreatment facility, stricter enforcement of load-based discharge permits, and improved industry–utility collaboration. This study is the first in Tanzania to apply a mass-based load assessment framework for industrial discharges, providing a replicable model for regulatory action. The results support implementation of Tanzania’s Industrial Wastewater Regulations (2020) and contribute to achieving SDG 6.3 on reducing untreated wastewater.