The effect of using pig manure as an internal carbon source in a traditional piggery wastewater treatment system for biological denitrification

Abstract

Due to a low ratio of chemical oxygen demand (COD) to total nitrogen (TN) and poor biodegradability of digested piggery wastewater, lack of a carbon source in subsequent biological treatment limits denitrification, resulting in an accumulation of NO2-N and NO3-N and a low denitrification efficiency. In this project, combined ultrasonication/alkali treatment of pig manure was used to generate a source of pig manure carbon source(PMC). This report mainly discusses the effects of adding the PMC on subsequent biological denitrification and microbial community changes. The experimental results showed that in subsequent biological treatment with the addition of 1.78% PMC, the effluent NO2-N and NO3-N were 0.02 mg·L−1 and 0.90 mg·L−1, respectively. The TN removal percentage was 72.29%, which was 62.29% higher than that obtained without an added carbon source and 36.74% higher than that obtained with added raw wastewater carbon (RWC). High-throughput sequencing revealed that the relative abundances of the dominant microflora Thauera and Thermomonas, which are related to denitrification, increased from 1.13% and 0.55% to 6.19% and 4.69%, respectively, after the addition of PMC. The addition of PMC improved the denitrification of digested piggery wastewater in subsequent biological treatment, and the denitrification effect was obvious and could enable waste resource utilization.