Effect of anaerobic treatment on sulphide concentration, TSS, TDS and electrical conductivity parameters of sulphide-lime unhairing wastewater

Abstract

Five microorganisms were isolated from aged sulphide-lime tannery wastewater following conventional method. The same was inoculated into similar wastewater collected after the production of upper leathers from Sokoto red goatskins, Nigeria. The effects of anaerobic treatment of the tannery effluent resulted to the reduction of pollutants determined by Sulphide and TSS and reducing sludge formation expected from sulphide-lime effluent. However, TDS which was observed as being proportional to electrical conductivity increase with respect to time, temperature and McF standard. At day 9 with 1.0 McF, isolate TII effected an increase in TDS by 51.09 % at 25°C and 64.03 % at 27°C, while isolate TI had an increase in TDS to 81.67 % and TV to 80.12 % at 37°C as the highest percentage recorded. Isolate TI was observed to increase electrical conductivity by 5.9 % at 25°C with 0.5 McF, 45.5 % at 27°C and isolate TIII by 52.83 % at 37°C for the same period of treatment. At day 7 with increase temperatures, the same isolate had 108.22% increase in electrical conductivity at 27°C and 104.85 % at 37°C. Although increase of electrical conductivity of the treated wastewater is expected, this abrupt increase is abnormal, and may be due to complex nature of tannery wastewater The maximum percentage reduction of sulphide was 25.35 % and 20.42 % by day 5 with 1.0 McF at 25°C, for isolates TIII and TV respectively. This is most probable because the anaerobes that induced the oxidation of carbon content of the wastewater while abstracting energy for their respiration. This causes Sulphur to get reduced to sulphide bringing about an increase of the parameter at the beginning of the treatment later decline, while depleting the carbon substances in the wastewater.

Keywords: wastewater, Anaerobic, Microorganisms, Treatment, Oxidation