Seasonal variation in physico-chemical characteristics of wastewater from domestic treatment plant

Discharge of wastewater contains a high level of contaminants that need sufficient treatment for legitimate applications and further reuse. This study investigated the effect of seasonal variations on the treatment performance of the Kombolcha Wastewater Treatment Plant. The values of characterized wastewater were compared against the international standard discharge limit. The range values of pH, total suspended solids (TSS), electrical conductivity (EC), temperature, turbidity, chemical oxygen demand (COD), alkalinity, sulfate, nitrite, nitrate and phosphate levels were in the range of 8.6–9.3, 196–226 mg/L, 1143–1244 μS/cm, 23–31 °C, 820–896 NTU, 580–622 mg/L, 241–290 mg/L, 8.3–11 mg/L, 7.1–7.8 mg/L, 3.1–3.9 mg/L, and 4.1–4.8 mg/L, respectively. The observed ranges of physicochemical parameters show how seasonal and operational factors together affect the efficiency of domestic wastewater treatment. The study found that variations in COD, TSS, and turbidity and nutrient levels resulted from three factors, which included changes in hydraulic loading and influent characteristics and treatment efficiency. The study found that temperature and electrical conductivity and alkalinity levels changed because of seasonal rainfall patterns and ambient temperature and dilution effects. The study found that higher temperatures in summer months increased microbial activity which led to more organic matter decomposition but that rainfall brought uncontrolled water flow which changed pollutant levels. The wastewater treatment system follows seasonal patterns because of these combined factors. Alkalinity, conductivity, TSS, turbidity, sulfate, phosphate, and COD values exhibited considerable month-to-month variation. The results showed that the values of conductivity, turbidity, TSS, COD, and phosphate of characterized wastewater were above the acceptable limit values suggested by the United State Environmental Protection Agency (USEPA). However, the average value of phosphate concentration was within the permissible limit of World Health Organization (WHO) and Ethiopian standard (ES). Before the wastewater is released into the environment, monitoring should be taken to prevent the risk of contamination in the receiving environment. Identifying seasonal variations of parameters promotes the optimization and performance of the operational conditions of the wastewater treatment plant.