Effect of steel slag on ammonia removal and ammonia-oxidizing microorganisms in zeolite-based tidal flow constructed wetlands. (December 2022)

• Record Type: Journal Article
• Authors: Zou, Yuhuan; Yang, Yongqiang; Wu, Shijun; Chen, Fanrong; Zhu, Runliang
• Is Part Of: Chemosphere. Volume 309:Part 1(2022)
• Publication Date: 2022-12
• Subjects: Tidal flow constructed wetlands -- Steel slag -- Hydraulic loading rate -- Comammox Nitrospira -- amoA; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.136727
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The ammonia removal performance of tidal flow constructed wetlands (TFCWs) requires to be improved under high hydraulic loading rates (HLRs). The pH decrease caused by nitrification may adversely affect the NH4 + –N removal and ammonia-oxidizing microorganisms (AOMs) of TFCWs. Herein, TFCWs with zeolite (TFCW_Z) and a mixture of zeolite and steel slag (TFCW_S) were built to investigate the influence of steel slag on NH4 + -N removal and AOMs. Both TFCWs were operated under short flooding/drying (F/D) cycles and high HLRs (3.13 and 4.69 m 3 /(m 2 d)). The results revealed that a neutral effluent pH (6.98–7.82) was achieved in TFCW_S owing to the CaO dissolution of steel slag. The NH4 + -N removal efficiencies in TFCW_S (91.2 ± 5.1%) were much higher than those in TFCW_Z (73.2 ± 7.1%). Total nitrogen (TN) removal was poor in both TFCWs mainly due to the low influent COD/TN. Phosphorus removal in TFCW_S was unsatisfactory because of the short hydraulic retention time. The addition of steel slag stimulated the flourishing AOMs, including Nitrosomonas (ammonia-oxidizing bacteria, AOB), Candidatus_Nitrocosmicus (ammonia-oxidizing archaea, AOA), and comammox Nitrospira, which may be responsible for the better ammonia removal performance in TFCW_S. PICRUSt2 showed that steel slag also enriched the relative abundance of functional genes involved in nitrification ( amoCAB, hao, and nxrAB ) but inhibited genes related to denitrification ( nirK, norB, and nosZ ). Quantitative polymerase chain reaction (qPCR) revealed that complete AOB (CAOB) and AOB contributed more to the amoA genes in TFCW_S and TFCW_Z, respectively. Therefore, this study revealed that the dominant AOMs could be significantly changed in zeolite-based TFCW by adding steel slag to regulate the pH in situ, resulting in a more efficient NH4 + –N removal performance. Graphical abstract: Image 1 Highlights: NH4 + -N removal rate was improved by adding steel slag in zeolite-based TFCW. Higher NH4 + -N removal rate was attributed to the neutral pH maintained by steel slag. Steel slag addition increased the diversity and abundance of AOMs. Steel slag addition shifts the dominant amoA genes from AOB to CAOB in the TFCWs.