Studies on lignin removal by soil perfusion technique

Abstract

Studies were carried out using a soil perfusion apparatus for the removal of lignin from waste water. It was observed that when a medium (pH 7.0) with lignin having about 1200 color units was perfused through a soil column, perfusate contained only 250 to 300 color units after three days of perfusion and pH was reduced to less than 5.0 with 70 to 80% reduction in Total Organic Carbon (TOC). With a sterile soil column the color was not removed and there was no change in TOC content. When the medium was buffered at pH 7.0, there was no reduction in color units. When the pH of the perfusate reduced to less than 5.0, it was also observed that the nitrate content had increased considerably. These results indicated that due to microbial activity lignin molecules might have been biotransformed and adsorbed on the soil column at lower pH. The major group of microorganisms were also isolated from the soil and their significance is discussed in this paper.