Anaerobic treatment of sulphide- lime unhairing and liming tannery wastewater and its effects on cod and BOD parameters

Abstract

Tannery sulphide-lime unhairing and liming wastewater is known to be highly polluted with very high values of COD and BOD and many other pollutants that poses serious threat to land and aquatic systems when discharge without treatment. Five anaerobes were isolated and identify as gram positive, they were inoculated into the sulphide–lime unhairing wastewater for treatment, at room temperature, 27°C and 37°C for 5,7 and 9 days with different McFarland standards of 0.5 and 1.0 McF. The results obtained shows various percentage reduction of COD and BOD. Considering the effectiveness of individual isolates, it was observed that at day 9, the highest percentage reduction of BOD5 was recorded by isolate TIV at 67.94 %; 65.0 % and 69.84 % at room temperatures, 27°C and 37°C respectively with 0.5 McF, implying that the isolates are likely to be mesophilic (35°C – 37°C). Further reduction of COD was recorded when treatment temperature and time was increase to 37°C such that after day 9, isolate TIV indicated a reduction of 62.5 % and 79.29 %, at 27°C and 37°C respectively. The maximum reduction of COD with 1.0 McF at 37°C for day 9 treatment period was 69.91 % by isolate TV. The mechanism is based on the microorganism which induced oxidation of carbon content of the wastewater abstracts energy through the process. The process also caused the reduction of Sulphur present in the wastewater leading to the generation of hydrogen sulphide gas which suggest the source of smell of the gas in any tannery lime yard.

Keywords: Sulphide–lime, Wastewater, Microorganisms, Treatment