Shunan Zhang

Nitrogen removal in Myriophyllum aquaticum wetland microcosms for swine wastewater treatment: 15N‐labelled nitrogen mass balance analysis

BACKGROUND Ecological treatments are effective for treating agricultural wastewater. In this study, wetland microcosms vegetated with Myriophyllum aquaticum were designed for nitrogen (N) removal from two strengths of swine wastewater, and 15 N-labelled ammonium (NH4+ -N) was added to evaluate the dominant NH4+ -N removal pathway. RESULTS The results showed that 98.8% of NH4+ -N and 88.3% of TN (TN: 248.6 mg L-1 ) were removed from low-strength swine wastewater (SW1) after an incubation of 21 days, with corresponding values for high-strength swine wastewater (SW2) being 99.2% of NH4+ -N and 87.8% of TN (TN: 494.9 mg L-1 ). Plant uptake and soil adsorption respectively accounted for 24.0% and 15.6% of the added 15 N. Meanwhile, above-ground tissues of M. aquaticum had significantly higher biomass and TN content than below-ground (P < 0.05). 15 N mass balance analysis indicated that gas losses contributed 52.0% to the added 15 N, but the N2 O flux constituted only 7.5% of total gas losses. The dynamics of NO3- -N and N2 O flux revealed that strong nitrification and denitrification occurred in M. aquaticum microcosms, which was a dominant N removal pathway. CONCLUSION These findings demonstrated that M. aquaticum could feasibly be used to construct wetlands for high N-loaded animal wastewater treatment.

Purification and reuse of non-point source wastewater via Myriophyllum-based integrative biotechnology: A review

In this review, the applications of Myriophyllum-based integrative biotechnology to remove common non-point source (NPS) pollutants, such as nitrogen, phosphorus, heavy metals, and organic pollutants (e.g., pesticides and antibiotics) are summarized. The removal of these pollutants via various mechanisms, including uptake by plant and microbial communities in macrophyte-based treatment systems are discussed. This review highlights the potential use of Myriophyllum biomass to produce animal feed, fertilizer, and other valuable by-products, which can yield cost-effective returns and attract more attention to the regulation and recycling of NPS pollutants. In addition, it demonstrates that utilization of Myriophyllum species is a promising and reliable strategy for wastewater treatment. The future development of sustainable Myriophyllum-based treatment systems is discussed from various perspectives.

The Significance of Myriophyllum elatinoides for Swine Wastewater Treatment: Abundance and Community Structure of Ammonia-Oxidizing Microorganisms in Sediments.

Myriophyllum elatinoides was reported to effectively treat wastewater by removing nitrogen (N) and phosphorus (P). However, little is known about the abundance and community structure of ammonia-oxidizing microorganisms associated with M. elatinoides purification systems. The objective of this research was to characterize the abundance and community structure of ammonia-oxidizing microorganisms in swine wastewater and determine the main nitrogen removal pathways. In this study, five different waters were treated by M. elatinoides in microcosms for one month. The five waters included tap water (Control), swine wastewater (SW), 50% diluted swine wastewater (50% SW), and two synthetic wastewaters: 200 mg NH4 +-N L−1 (200 NH4 +-N) and 400 mg NH4 +-N L−1 (400 NH4 +-N). The most dramatic changes were in NH4 +-N and total N (TN) concentrations, with average removal rates of 84% and 90%, respectively, in the treatments containing swine wastewater. On days 7, 14, and 28, the dissolved oxygen (DO) increased by 81.8%, 210.4% and 136.5%, respectively, compared with on day 0, in the swine wastewater. The results also showed that the bacterial amoA (AOB) copy numbers in the sediments of the treatments were significantly higher than those of archaeal amoA (AOA) copy numbers (p = 0.015). In addition, the high DO concentrations in swine wastewater responded well to the high abundance of AOB. The AOA and AOB community distributions were positively related with NO3 -N and were negatively related with DO in swine wastewater treatments. In summary, our experimental results suggested that the M. elatinoides purification system could improve the activity of ammonia-oxidizing microorganisms and consequently might contribute to the significant N removal from the swine wastewater.

Nitrogen removal and recovery from lagoon-pretreated swine wastewater by constructed wetlands under sustainable plant harvesting management

A series of three-stage pilot-scale surface flow constructed wetlands (CWs) planted with Myriophyllum aquaticum were fed with three strengths of lagoon-pretreated swine wastewater to study nitrogen (N) removal and recovery under sustainable plant harvesting management. The CWs had mean removal efficiency of 87.7-97.9% for NH4+-N and 85.4-96.1% for total N (TN). The recovered TN mass via multiple harvests of M. aquaticum was greatest (120-222 g N m-2 yr-1) when TN concentrations were 21.8-282 mg L-1. The harvested TN mass accounted for 0.85-100% of the total removal in the different CW units. Based on mass balance estimation, plant uptake, sediment storage, and microbial removal accounted for 13.0-55.0%, 4.9-8.0%, and 33.0-67.5% of TN loading mass, respectively. The results of this study confirm that M. aquaticum is appropriate for the removal and recovery of nutrients in CW systems designed for treating swine wastewater in conjunction with sustainable plant harvesting strategies.

Evaluating organics removal performance from lagoon-pretreated swine wastewater in pilot-scale three-stage surface flow constructed wetlands

Pilot-scale three-stage surface flow constructed wetlands (SFCWs) planted with Myriophyllum aquaticum were constructed to study the organics removal performance from lagoon-pretreated swine wastewater. The removal performance of organics in the SFCWs was evaluated using deterministic and probabilistic methods and the results were consistent. The SFCWs achieved a relatively high removal efficiency (79.0-82.7%) for a wide influent COD concentration range (456-1010 mg L-1). No significant difference (p > 0.05) of COD removal efficiency and first-order removal rate constant among the various strengths of influent suggested that the present loading rates (2.74-6.06 g m-2 d-1) have not yet reached the maximum removal capacity of the SFCWs. The mean emission fluxes of methane from the SFCW units fed with different strengths of wastewater were 25-1210 mg m-2 d-1. A significantly positive correlation (p < 0.01) between methane emission fluxes and COD loading rates indicated that the anaerobic digestion of organics was an important process for organics removal in the SFCWs. No significant organics accumulation in the sediment over time suggested that plant harvest could be in favor of reducing the organics accumulation in the substrate and should be considered important during management of constructed wetlands.