Performance evaluation of microbial fuel cell for removing chromium from textile wastewater

Abstract

Textile industry is one of the largest industries in Bangladesh. The industries discharge a large volume of wastewater containing organic pollutants and heavy metals. Heavy metal contamination in water is a serious threat to environment and human health. Chromium is a strictly regulated heavy metal in wastewater due to its high toxicity at low concentration. Heavy metals are difficult to remove in conventional wastewater treatment approaches because they are bio-accumulating, non-biodegradable, and more persistent than organic pollutants. Advanced treatment methods e.g. membrane filtration or ion exchange, can be applied but they often require a high energy input and a large amount of chemicals for pre- or post-treatment. Microbial fuel cell (MFC) is full of promise to take the edge off environment pollution. MFC can be used without these external and expensive requirements of wastewater treatment. The microbial metabolism enables MFC to produce bio-electricity simultaneously while removing chromium from waste water. This research work evaluated the performance of MFC for bioelectricity generation as well as removing chromium from textile wastewater. In order to develop an energy-efficient and cost-effective cell, the performance was analyzed by power density and coulombic efficiency. On the other hand, the removal percentages of total chromium and chemical oxygen demand (COD) provided waste removal efficiency of the MFC. This research progressed with a gradual development of an experimental setup by considering the optimum effect of electrode materials, aeration, salt bridge, and nutrient. The novelty and significance of this system is that it uses an uncomplicated and economical salt bridge which replaces costly membranes like Nafion. As a result, the lab-scale MFC operations demonstrated successful microbial bioremediation of chromium. The commonly investigated removal mechanism for heavy metals in MFCs is reduction at the cathode. However, this thesis work emphasized the anodic removal of chromium to highlight the microbial mechanism for removing chromium from textile wastewater. The fully developed MFC resulted in 53.75% removal of chromium from the anodic chamber where the initial concentration of Cr was less than 1 mg/L. The analytical assessment of SEM – EDX and XRD provided the surface morphology, mass percentage, and elemental identification of chromium in the anode. The analytical experiments of anode also confirmed the active presence of microbes for removing chromium from textile wastewater.