Abstract
This study aimed to explore the performance of denitrification deep-bed filter (DN-DBF) to treat municipal sewage for meeting a more stringent discharge standard of total nitrogen (TN) (10.0 mg L–1). A lab-scale DN-DBF was conducted to optimize operation parameters and reveal the microbiological mechanism for TN removal. The results showed that more than 12.7% TN removal was obtained by adding methanol compared with sodium acetate. The effluent TN concentration reached 6.0–7.0 mg L–1 with the optimal influent carbon and nitrogen ratio (C/N) and hydraulic retention time (HRT) (3:1 and 0.25 h). For the nitrogen removal mechanism, Blastocatellaceae_Subgroup_4 and norank_o_JG30-KF-CM45 were dominant denitrification floras with an abundance of 6–10%. Though large TN was removed at the top layer of DN-DBF, microbial richness and diversity at the middle layer were higher than both ends. However, the relative abundance of nitrite reductase enzymes (EC1.7.2.1) gradually increases as the depth increases; conversely, the relative abundance of nitrous oxide reductase gradually decreased.
Highlights
Eutrophication, caused by excessive discharged nutrients from wastewater treatment plants, has become one of the most urgent problems and gained significant attention in recent years (Piao and Kim, 2016)
Carbon Source Types CH3OH and NaAC were added to Denitrification deep-bed filter (DN-DBF)
The average total nitrogen (TN) removal efficiency was 41.11 and 51.04% with an effluent concentration of 8.09 and 6.80 mg L−1, respectively, when equal chemical oxygen demand (COD) was dosed by CH3OH and NaAC
Summary
Eutrophication, caused by excessive discharged nutrients (nitrogen and phosphorus) from wastewater treatment plants, has become one of the most urgent problems and gained significant attention in recent years (Piao and Kim, 2016). The traditional secondary biological treatment was difficult to meet due to the strict TN discharge standard (Li et al, 2014). More and more advanced treatment technologies are needed to control TN discharge and protect the limited water sources. Tertiary denitrification was required to further remove the nitrate nitrogen (NO3−-N) so as to achieve a high TN discharging standard since NO3−-N is the major component of TN in a secondary effluent. Previous studies on DN-DBF just to meet one-class A discharge standard, for the parameters [such as carbon source type, chemical oxygen demand (COD) and TN (C/N) ratio, and hydraulic retention time (HRT)] of further advanced treatment were not yet clear (Cao et al, 2016; Xu et al, 2016)
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