A Promising Process to Remove Nitrate from Solar Panel Production Wastewater and Meanwhile Generating Electricity

Abstract

For traditional heterotrophic denitrification technology, organics are usually added as the electron donor for nitrate removal, which increases the operation cost for wastewater treatment. Solar panel production wastewater contains a large amount of nitrate. To decrease the operation cost and reduce CO2 emissions, an iron anode microbial fuel cell (Fe-MFC) was constructed to treat solar panel production wastewater by sequencing batch operation. The results showed that the maximum nitrate removal efficiency reached 99.98% and the maximum removal rate was 0.049 kg·m−3·d−1. The output voltages rose rapidly to 560 ± 10 mV within 2 h and then stabilized at 520 ± 50 mV for about 40 h. Combining the detection of coulombic efficiency, CV curve, q* value and internal resistance; the decrease in denitrification efficiency and electricity generation efficiency probably resulted from the passivation of iron anode and the aging of the cathode biofilm resulted in the efficiency decrease. From the microbial analysis, Chryseobacterium, Thermomonas and Thauera predominated at the end of Fe-MFC operation. Microorganisms that cannot adapt to the autotrophic environment in Fe-MFC died out finally. Periodic replacement of the iron anode and domestication of the bio-cathode were essential to maintain the Fe-MFC efficiency. The Fe-MFC technology was feasible to be used to remove nitrate and generate electricity from solar panel production wastewater. Without organics addition, the Fe-MFC technology was cost-efficient and environmentally friendly, endowing itself with a broad prospect of application.