Use of Rice Husk Ash as an Admixture to Remove Chromium from a Tannery Waste

Abstract

This laboratory-scale study explored the use of rice husk ash (RHA) as an admixture to stabilize and solidify the waste sludge from a chrometanning process. Various ratios of RHA and tannery sludge were used, ranging from 0.25 to 1.0 by weight of the cement content, resulting in an experimental matrix of 16 runs. It was observed that although the compressive strength of solidified sludge improved at longer curing times, the increase was moderate after 7 days of curing. In addition, higher RHA and/or sludge ratios progressively reduced the strength of the samples. On the other hand, curing time had a positive effect on chromium leachability since the leaching concentration decreased considerably with an increase in curing time, up to 28 days. Furthermore, both the RHA and/or sludge content affected leachability, producing acceptable results, from a Thai regulatory perspective, at ratios of 0.50 or lower. Finally, the solidified sludge can be disposed of in a secure landfill and/or used as a construction material in a number of applications.

The Problems in Achieving Sustainable Development in the Tannery Industry in Regard to Sewage Sludge Management

“…The solidified samples compressive strength was inversely proportional to the share of the sewage sludge in the composite. The highest compressive strength after 28 days of curing was noted for a mixture containing around 17% of tannery sludge, 16% of rice husk ash and almost 67% of cement (Fongsatitkul et al, 2011). The highest investigated share of tannery sludge in the solidified material was 44.5% which required the same amount of cement, and rice husk ash addition of 11%.…”

“…An additional problem is the obtained chromium solution, which as stated by many Authors is of low quality and numerous impurities (Cassanoet al A very promising approach in solving the issue of tannery sludge management seems to be of solidification which incorporates the use of numerous binding agents such as cement. The possibility of solidifying tannery sewage sludge (chromium content of 474 000 mg/kg) using rice husk ash and cement was investigated by Fongsatitkul et al (2011). The solidified samples compressive strength was inversely proportional to the share of the sewage sludge in the composite.…”