Dynamics of Bacterial Community Abundance and Structure in Horizontal Subsurface Flow Wetland Mesocosms Treating Municipal Wastewater

Abstract

Dynamics of bacterial community abundance and structure of a newly established horizontal subsurface flow (HSSF) pilot-scale wetland were studied using high-throughput sequencing and quantitative polymerase chain reaction (PCR) methods. Bacterial community abundance increased rapidly within one month and stabilised thereafter in three replicate HSSF constructed wetland (CW) mesocosms. The most dominant phylum was Proteobacteria, followed by Bacteroidetes in wetland media biofilms and Firmicutes in influent wastewater. CW bacterial community diversity increased over time and was positively related to the wastewater treatment efficiency. Increase in the abundance of total bacteria in the community was accompanied with the abundance of denitrifying bacteria that promoted nitrate and nitrite removal from the wastewater. During the 150-day study period, similar patterns of bacterial community successions were observed in replicate HSSF CW mesocosms. The data indicate that successions in the bacterial community in HSSF CW are shaped by biotic interactions, with a significant contribution made by external abiotic factors such as influent chemical parameters. Network analysis of the bacterial community revealed that organic matter and nitrogen removal in HSSF CW could be, in large part, allocated to a small subset of tightly interconnected bacterial species. The diversity of bacterial community and abundance of denitrifiers were good predictors of the removal efficiency of ammonia, nitrate and total organic C in HSSF CW mesocosms, while the removal of the seven-day biochemical oxygen demand (BOD 7 ) was best predicted by the abundance of a small set of bacterial phylotypes. The results suggest that nitrogen removal in HSSF CW consist of two main pathways. The first is heterotrophic nitrification, which is coupled with aerobic denitrification and mediated by mixotrophic nitrite-oxidizers. The second pathway is anaerobic denitrification, which leads to gaseous intermediates and loss of nitrogen as N 2 .

Microbial Diversity in Continuous Flow Constructed a Wetland for the Treatment of Swine Waste

“…One major advantage of pyrosequencing is high-throughput and a large dataset of sequences, which can identify many microorganisms in a single analysis. As shown in this study, and from our previous study with bacteria [3], 16S rDNA sequences from different segments of the wetland may be used to determine the efficiency of the constructed wetland. This approach can monitor changes of microbial communities as waste flows through the wetland and has high potential for improving water quality based on bacterial concentrations.…”

“…Constructed wetland (CW) is a natural process for the treatment of waste from a variety of sources [1][2][3]. They are cost-effective, ecologicallyfriendly, and a simple alternative to conventional technologies for wastewater treatment [3,4].…”

“…They are cost-effective, ecologicallyfriendly, and a simple alternative to conventional technologies for wastewater treatment [3,4]. It has also been shown that, significant benefits to human populations in both [2] developed and developing countries can be achieved through constructed wetlands, and these benefits may include water-quality improvement, water reclamation, conservation of habitat for species, flood control, recreational and educational activities [1,[4][5][6][7].…”

Constructed Wetlands for Water Treatment: New Developments

“…Oopkaup et al [17] present a deep insight into the dynamics of bacterial community abundance and structure in a newly-established unplanted horizontal subsurface flow (HSSF) mesocosm (from a broader experimental plant). High-throughput sequencing and qPCR analysis were successfully applied to determine the bacterial community structure and abundance, respectively.…”

“…Moreover, the factors affecting bacterial community composition were screened through the distance-based regression analysis, and denitrification potential and the relationship between treatment efficiency and bacterial community structure were assessed. Based on the obtained data, the authors suggest that nitrogen removal in their system consists of two main pathways: (i) heterotrophic nitrification, which is coupled with aerobic denitrification and mediated by mixotrophic nitrite-oxidizers; and (ii) anaerobic denitrification [17].…”