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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Publications at this Location » Publication #382600
Research Project: Develop Water Management Strategies to Sustain Water Productivity and Protect Water Quality in Irrigated Agriculture

Location: Water Management Research

Title: Improving denitrification efficiency in constructed wetlands integrated with immobilized bacteria under high saline conditions

Author
item WANG, XINYI - Chinese Academy Of Agricultural Sciences
item ZHU, HU - Chinese Academy Of Agricultural Sciences
item YAN, BAIXING - Chinese Academy Of Agricultural Sciences
item SHUTES, BRIAN - Middlesex University London
item Banuelos, Gary
item WEN, HUIYANG - Chinese Academy Of Agricultural Sciences
item CHENG, RUI - Chinese Academy Of Agricultural Sciences

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2021
Publication Date: 6/18/2021
Citation: Wang, X., Zhu, H., Yan, B., Shutes, B., Banuelos, G.S., Wen, H., Cheng, R. 2021. Improving denitrification efficiency in constructed wetlands integrated with immobilized bacteria under high saline conditions. Environmental Pollution. 287. https://doi.org/10.1016/j.envpol.2021.117592.
DOI: https://doi.org/10.1016/j.envpol.2021.117592

Interpretive Summary: The increasing discharge of untreated saline wastewater from aquaculture and industrial production has been threatening the aquatic, terrestrial and wetland ecosystems worldwide. Constructed wetlands (CWs) have been widely used for the treatment of various types of wastewaters. However, high salinity will inhibit both the growth of plants and microorganisms, which limits the removal capacity of pollutants, especially nitrogen, in CWs. Microorganisms play a dominant role in nitrogen removal by CWs, and their activity is often negatively affected by salinity. In this study, we developed salt-tolerant bacterium and incorporated them with a carbon source and evaluated their feasibility for improving the nitrogen removal capacity of the CW under saline conditions. After 60 days, we demonstrated that the CWs incorporated with immobilized bacteria can effectively increase the abundance of exogenous salt-tolerant bacteria. As a result, the mean NO3--N and TN removal percentages were 97.8% and 88.1%, respectively, for inoculated CWs compared to 48.7% and 67.2% for the uninoculated CWs. This study demonstrates a breakthrough in the durable removal of nitrogen from saline wastewater in CWs by the addition of the immobilized bacteria. Moreover, the positive results by adding only one inoculum application may have also solved the problem of high costs that are associated with repeated inoculations with other forms of microorganisms under saline conditions.

Technical Abstract: Constructed wetlands (CWs) inoculated with exogenous microbes have great potential for removing pollutants in adverse environments. The rapid loss of functional bacteria and the high cost of repeated additions of inoculum, however, limit the practical application of this technology. In this study, immobilized bacteria were developed and utilized in CWs. Our 60-day experiment demonstrated that bioaugmented CWs (Bio-CWs) with the addition of C-F2 immobilized bacteria (i.e., immobilized salt-tolerant bacterium Alishewanella sp. F2 incorporated with carbon source) into the bottom gravel layer of CW microcosms (B-CF2 treatment) exhibited high nitrogen removal efficiency under saline conditions (electrical conductivity of 15 mS/cm). We measured mean NO3--N and TN removal percentages of 97.8% and 88.1%, respectively, which were significantly (p < 0.05) higher than those in Bio-CWs with microbial inoculum (MI-F2 treatment, at 63.5% and 78.2%, respectively) and unbioaugmented CWs control (CK), at 48.7% and 67.2%, respectively.The TN content of the entire plant was significantly (p < 0.05) increased in B-CF2 (636.06 mg/microcosm) compared with control (372.06 mg/microcosm). The relative abundances of the genera Alishewanella (i.e., the exogenous bacterium, 5.5%), Clostridium-XlVa (8.8%) and Bacteroides (21.1%) in B-CF2 were significantly (p < 0.05) higher than MI-F2 and CK, which improved the denitrification capacity of CWs. Overall, a high denitrification efficiency and durability were achieved in the newly developed Bio-CWs with immobilized bacteria under saline conditions, which provides an alternative technology for the rapid removal of nitrogen from saline wastewater.