Microbial fuel cells (MFCs) represent a novel platform for treating wastewater and at the same time generating electricity. Using Pseudomonas putida (BCRC 1059), a wild-type bacterium, we demonstrated that the refinery wastewater could be treated and also generate electric current in an air-cathode chamber over four-batch cycles for 63 cumulative days. Our study indicated that the oil refinery wastewater containing 2213 mg/L (ppm) chemical oxygen demand (COD) could be used as a substrate for electricity generation in the reactor of the MFC. A maximum voltage of 355 mV was obtained with the highest power density of 0.005 mW/cm2 in the third cycle with a maximum current density of 0.015 mA/cm2 in regard to the external resistor of 1000 Ω. A maximum coulombic efficiency of 6 × 10−2% was obtained in the fourth cycle. The removal efficiency of the COD reached 30% as a function of time. Electron transfer mechanism was studied using cyclic voltammetry, which indicated the presence of a soluble electron shuttle in the reactor. Our study demonstrated that oil refinery wastewater could be used as a substrate for electricity generation.

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Abstract

The soil quality in a paddy field is the most crucial element for the supply and the production of rice in India. However, the pressure on the paddy field creates a challenge for preventing soil degradation. Soil microflora are most vulnerable to soil pollution, and a decrease or increase of the soil bacteria may reflect the health of soil. In this study, we try to understand the effect of crop management and weed control systems on the native soil bacterial colony. Our study consists of three types of crop management systems, such as zero-tillage, the system of rice intensification (SRI), brown manuring, and three types of weed removal processes, i.e. chemical, integrated and mechanical. In the chemical and integrated treatment, two herbicides were used for weed removal, but in mechanical weeding, a conoweeder was used. The colony forming unit (CFU) of different soil bacteria (nitrogen fixing and phosphate solubilizing) were measured during different stages of the crop growth. It was observed that the mechanical weeding has the least impact for both soil bacteria, but the chemical treatment showed a decrease of PSB count in all three systems. Whereas, the integrated treatment produced a better result in crop management and soil microbial population.