Abstract
Biological nitrogen removal (BNR) in centralized and decentralized wastewater treatment systems is assumed to be driven by the same microbial processes and to have communities with a similar composition and structure. There is, however, little information to support these assumptions, which may impact the effectiveness of decentralized systems. We used high-throughput sequencing to compare the structure and composition of the nitrifying and denitrifying bacterial communities of nine onsite wastewater treatment systems (OWTS) and one wastewater treatment plant (WTP) by targeting the genes coding for ammonia monooxygenase (amoA) and nitrous oxide reductase (nosZ). The amoA diversity was similar between the WTP and OWTS, but nosZ diversity was generally higher for the WTP. Beta diversity analyses showed the WTP and OWTS promoted distinct amoA and nosZ communities, although there is a core group of N-transforming bacteria common across scales of BNR treatment. Our results suggest that advanced N-removal OWTS have microbial communities that are sufficiently distinct from those of WTP with BNR, which may warrant different management approaches.
Highlights
Wastewater treatment plants (WTP) and onsite wastewater treatment systems (OWTS) with biological nitrogen removal (BNR) can lower the concentration of N in effluent before it is discharged to receiving waters [1], lowering the public health and environmental risks associated with N-pollution of ground and surface waters [2,3,4]
These differences may be caused by the introduction of soil when OWTS are installed and inspected, suggesting that soil is an important source of ammonia-oxidizing bacteria for these systems
This suggests that the soil entering during inspection is important to inoculate relative abundances in OWTS are usually found in soil, including N-fixers like Bradyrhizobium and systems with denitrifying bacteria we proposed with ammonia monooxygenase (amoA), may is beimportant an important source of
Summary
Wastewater treatment plants (WTP) and onsite wastewater treatment systems (OWTS) with biological nitrogen removal (BNR) can lower the concentration of N in effluent before it is discharged to receiving waters [1], lowering the public health and environmental risks associated with N-pollution of ground and surface waters [2,3,4]. Water 2020, 12, 1688 version of a WTP with BNR [1], with designs explicitly based on engineering principles underlying a WTP [5,6] This is based on the expectation that environmental selection—in this case alternating oxic and hypoxic/anoxic conditions—drives microbial community structure [7]. The microbiome of WTPs has been well described using culture-independent, high-throughput sequencing techniques [12] that can identify low abundance and transient taxa in WTP communities more accurately than culture-dependent techniques [13,14] These advances in molecular microbial probing have allowed for analyses of the microbial community of WTPs, which have shown that communities vary as a function of geography [15,16,17], time [18,19,20], influent type [21], and zone within a treatment facility [22]. A better understanding of these communities may eventually lead to changes in design and operation that enhance N removal, especially in OWTS
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