Assessment of Physico-chemical Properties of Sagana Tanneries Effluent and Its Effect on River Sagana Water Quality - Kirinyaga County, Kenya

Abstract

The tanning industry uses many complex chemicals and has a high demand for water, this makes it a pollution intensive sector that requires strict regulation and monitoring. Sagana Tanneries Limited discharges treated effluent in River Sagana and, residents downstream have in the past complained about water pollution characterized by change in water color and death of fish. River Sagana is a domestic water source and therefore, assessment of physico-chemical properties of the effluent and the river was undertaken. Management strategies and technology adopted by the tannery were also evaluated together with challenges and opportunities facing environmental management in the tanning industry. Raw and treated effluents from the entire wastewater treatment section were sampled and analyzed to ascertain the level of pollutants. Water from River Sagana was also collected at intervals of 500 m and the toxicity load was determined to inform on the impact of treated effluent disposal into the river. Assessment of samples was done to determine levels of pH, chemical oxygen demand, biochemical oxygen demand, phosphorus, nitrogen, chromium, lead, copper and zinc. The results revealed that the effluent discharged from the tannery TLG9 satisfied legal standards for pH 7.42, chromium 1.1 ppm and copper 0.41 ppm. For parameters COD 630 ppm, BOD 236.7 ppm, P 5.2 ppm, N 53.5 ppm, Pb 0.07 ppm and Zn 0.85 ppm, all were above prescribed NEMA standards. River water analysis revealed TR1, TR2, TR3 and TR4 had: pH at 7.24, 7.17, 7.25 and 7.32 respectively. COD ranged from 172 ppm - 412 ppm while BOD was between 66.4 ppm - 209.1 ppm. P ranged from 5.6 ppm - 11.8 ppm and highest level of N was at TR4 307 ppm. The highest level of Cr was at TR4 3.35 ppm, Pb at TR4 0.23 ppm, Cu at TR2 0.48ppm and Zn at TR3 1.71ppm. Pollution of River Sagana is a reality. River water upstream is polluted and although free from tannery effluent, it contains high amounts of pollutants. Disposal of treated effluent into the river is not safe since the tannery effluent contributes to direct pollution of the river. The tannery should minimize wastewater production by recycling chrome baths and refining in-plant production processes. Additionally, it should remedy chromium contamination of effluent by ensuring effluent streams don’t mix. Inadequate human resource capacity of regulatory bodies like NEMA is a challenge. This, coupled with lack of essential scientific ability to set up laboratories for analysis results in inefficient and irregular monitoring. To help improve environmental compliance, enforcement of existing regulations should be implemented by responsible authorities and proper mainstreaming executed in all tanneries. Additionally, an environmental audit of all existing tanneries in Kenya should be conducted to help understand the current environmental status of the tanning industry. Policy documents should also be reviewed and updated to incorporate specific environmental guidelines for the tanning industry as guided by technological research on cleaner production, effluent treatment and waste management. Further research is recommended on the impact of chrome sludge disposal on the environment around dumpsites and the effect on ground water. An in-depth analysis of the chemical properties of leather manufacturing chemicals used in local industries is also recommended so as to ascertain the specific sources of heavy metals in tannery effluent