QUANTIFICATION OF Cr +3, Cr +6, TOTAL CHROMIUM, AND PHYSICOCHEMICAL CHARACTERISTICS OF TANNERY WASTEWATER EFFLUENTS: A case study of Bata Tanneries, Kenya

Abstract

Kenya's tanning industry is a key economic sector. Leather processing generates toxic effluents depending on the process. Bata leather industries in Kenya have been discharging effluent to nearby rivers leading to human and environmental pollution. The current study sought to carry out quantification of chromium and physicochemical characteristics of tannery wastewater effluents: “A case study of Bata Tanneries, Kenya”. Using grab sampler, water samples were obtained from four sites (S1 – Pre-tanning, S2 – Tanning, S3 – Post-tanning, and S4 – Drainage to the river). The samples were transported to the Tea Research Foundation of Kenya in a cold box for chemical analysis. Bis(salicylaldehyde) orthophenylenediamine reagent was used to complex Cr 6+ in non-ionic micellar media to dertermine the concentration of Cr +6. Double beam uv/vis spectrophotometer (perkinelmer) was used in the analysis. Physiochemical parameters were determined from the collected samples and results were with compared with NEMA, KEBS and WHO set standards. Total Cr level was analysed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The mean range levels obtained from (S1, S2, S3 and S4) Bata leather tanneries in Kenya were as follows; total dissolved solids (TDS) 137.70 and 270.00 mg/L, DO 8.40 and 10.60 mg/L, pH concentrations ranged between 1.52 and 8.20. EC 1348.8 and 1385.00 mS/cm at S3, temperature 22.70 and 27.90OC, biological oxygen demand (BOD) 3141.20 and 5477.70 mg/L, total suspended solids (TSS) 148.00 mg/L to 284.00 mg/L, total solids (TS) 286.00 and 554.00 mg/L. Chemical oxygen demand (COD) 5986.70 to 9093.20 mg/L, colour (Pt-Co) 488.50 and 787.20 Pt-Co. The mean levels of total chromium, Cr 3+and Cr 6+ in effluent samples were 573.71 and 72.370, 12.08 and 1.37, and 560.38 and 70.69 mg/L, respectively. It is evident from the results of this study that high percentage of 98.05 ± 0.15 % from the initial concentration, added and found concentration of 2.00 ± 0.00, 2 ± 0.00 and 2.25 ± 031, respectively. All values of physicochemical parameters exceeded WHO standards except for temperature which was within the range. In comparison with the two methods, UV spectroscopic did best in comparison with ICP- AES in a non-ionic micellar media though with no significant difference (t = 0.2222, p= 0.8350. The ministry of Environment should therefore enforce the law concerning water pollution and prosecute those who are found culpable. Polluter pay principle should be applied to the company.