Enhancing the nitrogen removal from swine wastewater digested liquid in a trickling biofilter with a soil layer

Trickling biofilters (TFs) allow for a simultaneous nitrification and denitrification (SND) process, and offer a favorable solution for the treatment of swine-wastewater digested liquid due to their simple operation and low cost. In this study, a soil trickling biofilter (STF) was developed to enhance nitrogen removal. A gravel trickling filter (GTF) and a woodchip trickling filter (WTF) were also constructed and operated synchronously to demonstrate the advantage of micron-sized media. The results showed that the STF had a higher ammonium nitrogen (NH₄ ⁺-N) removal capacity of 21.4%, 24.9%, and 18.3% in comparison to the GTF when the influent NH₄ ⁺-N was 192.9 mg L^-1, 500.2 mg L^-1 and 802.1 mg L^-1, respectively. The total nitrogen (TN) removal capacity of the STF was 104.6%, 89.4%, and 37.5% higher than that of the WTF. Thus, the addition of micron-sized soil to TF could increase the systemic nitrogen removal capacity.