Value-added waste potential of wastewater sludge from pharmaceutical industry: a review

Abstract

Wastewater treatment (WWT) plant treating pharmaceutical processing water produces sludge that may contain residue of the pharmaceutical products. This residue, known as Active Pharmaceutical Ingredient (API) is known to show ecotoxicity to the environment. The sludge potential to be utilised as value added products or to be used as raw material for other processes is explored in this review. Currently there is lack of studies on the content of pharmaceutical WWT (pWWT) sludge and its added value usage, partly due to vast varieties of pharmaceutical products, each utilising different process with different removal success in WWT and different effect on bacterial growth. Residue API from pharmaceutical manufacturing is known to be sorbed on the surface of the sludge. Cross comparison using limited sources of studies of bacterial composition in pWWT with municipal WWT (mWWT) shows that there are similarities between the bacterial compositions and thus sludge composition since sludge from biological WWT is constituted mainly of microorganism and Extracellular Polymer Substance (EPS). Studies on pWWT sludge composting shows usability of the sludge for agriculture purpose, but with concern over the sorbed API content causing ecotoxicity on the soil. Converting pWWT to energy using gasification and biodiesel production and construction material are the most promising value-added usage for the sludge.