Study on denitrification of hydroponic wastewater reverse osmosis concentrate using sulfur-autotrophic denitrification

Hydroponic agriculture is one of the sectors that generate the highest amounts of nitrogen-containing waste-water. Sulfur-autotrophic denitrification is considered a promising technology due to its stable and excellent denitrification performance, cost-effectiveness, and operational advantages. In order to investigate the denitri-fication performance and the contribution of the filter layer under high NO3 --N concentration (600 mg center dot L-1), this experiment designed a denitrification system using Na2S2O3 as an electron donor. The results showed that the reactor achieved the highest denitrification efficiency with a hydraulic retention time of 12 h, pH of 7, and sulfur to nitrogen ratio of 2, maintaining a stable NO3 --Nremoval efficiency of 99%. The majority of NO3 --Nwas removed by the bottom filter layer (0-300 mm), accounting for 86% of the total denitrification. The microbial community in the lower part of the filter column was dominated by Proteobacteria, with relatively high abun-dances of the genera Chryseobacterium, Thiobacillus, and Sulfurimonas. Similarly, the microbial community structure in the upper filter layer was dominated by Proteobacteria, with an increased abundance of the genus Chryseobacterium and a significant reduction in the abundance of Sulfurimonas. The study indicates that SAD can achieve stable and efficient denitrification of wastewater from hydroponic reverse osmosis concentrate. More -over, higher NO3 --Nconcentrations can influence the bacterial community structure within the reactor.

Automated summary

Sulfur-autotrophic denitrification is a promising technology for treating wastewater from hydroponic agriculture. This study found that under suitable conditions, the filter layer can effectively remove nitrogen from the wastewater, with the bottom layer contributing the most. The nitrogen concentration in the wastewater also affects the bacterial community structure within the reactor.