Voltage regulation of enzyme activity to control the slow release rate of novel solid carbon source to achieve high...

Solid carbon source was one of the methods to solve the lack of carbon source in the denitrification process, but there were some problems that COD of effluent exceeded the standard due to the rapid release of dissolved carbon source in the early stage, and the denitrification effect was poor due to the insufficient release of carbon source in the later stage. We therefore applied voltage to regulate the release rate of a waste-paper cellulose carbon source. The results showed that among 0-0.8 V, 0.4 V exerted the strongest inhibition. The cumulative COD release reached 1582.23 mg/L, 43 % lower than that of the non-electrified group. The activities of cellulose degrading enzymes β-glucosidase and carboxymethyl cellulase were 2.63 and 0.32 μg/min·mg protein, respectively, while those of control group were 4.79 and 0.67 μg/min·mg protein, respectively. The applied voltage not only changed the activity of cellulose degrading enzyme, but also changed the microbial community structure in the solid carbon source. The abundance of Ruminiclostridium used to degrade cellulose in solid carbon sources with different voltage duration and different voltage values was 16.27 % and 30.63 %, respectively. When the influent NO₃^--N concentration was 17.2 mg/L, the effluent NO₃^--N concentration using this solid carbon source was 0.40 mg/L, the removal efficiency was 97.63 %, and the removal load was 1.05 g/L·h. In wastewater treatment, the solid carbon source with controllable slow release rate could continuously supply carbon for denitrifying microorganisms as needed, thus achieving high-efficiency and deep denitrification at lower cost.