Bioleaching Approach for Enhancing Sewage Sludge Dewaterability

Abstract

Sewage sludge is an unavoidable byproduct of the wastewater treatment course. Rising population, and growing urbanization contributes to a sizeable quantity of sewage sludge production. Disposal of such a huge amount of waste requires environmentally safe and economically viable options. Though the applications of sludge to the agricultural field can help recycling in nutrients and organic matter, the heavy metal in sewage sludge, various toxic substances and pathogens often make it unfit for direct agricultural application without any treatment. Moreover, the sewage sludge is very bulky and hence the cost of transport and/or subsequent processing/treatment becomes difficult. Dewatering of sewage sludge can help in reducing sludge volume, facilitates easy transport, increases the calorific value and can decrease leachate output in the landfill site. The strong interaction between solids and water in sewage sludge makes it difficult to remove water. Conditioning of sludge by physical and chemical methods has been successful improvement of the dewaterability of sludge, however, these practices are limited by high cost, high energy requirement, and use of non-green chemicals. Bioleaching, a bio-acidification strategy widely discussed for heavy metal decontamination, is operative in improvement of the dewaterability of sludge and gives many benefits over other methods. In the present chapter, the process of bioleaching, its process and mechanism and role in improving the dewaterability of sludge have been discussed.