Process Design For Removal of Heavy Metals By A Bio-sorbent Trickle Bed System: A Proof of Concept

Abstract

Most heavy metals are well-known toxic and carcinogenic agents and when discharged into the wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. The development of a novel biofilter was aimed in this project. The various parameters of the biofiltration processes, their mechanism for heavy metals removal along with the efficiency of the biofilters and its scale up aspects have been studied. The work was targeted towards removal of Iron (Fe) and Chromium (Cr), two very common contaminant in urban as well as rural ground water. These are also found in industrial spent waters. The efficiency of the biofiltration process for heavy metals removal have been critically analysed. In a proof-of-concept study, a laboratory-scale closed biofilter system employing the trickle bed process was operated to remove Iron (Fe) and Chromium (Cr) from a synthetic waste water sample at a load of 1000mg/L of the heavy metal. Gravel, citrus peels and spent tea leaves after proper pre-treatment was used as filter media. Depth profile analysis of the filter bed showed the reduction of a steep gradient of Iron and Chromium from the top layer to the bottom layer of filter media in the biofilter. Iron and Chromium level at the bottom of the biofilter decreased over 85% over a period of 6-8 hours of experiment. With these observations we have scaled up the process from a 0.050 L to 15.0 L operating volume. The results were consistent.