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Abstract 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. Graphical abstract Image 1 Highlights • Pilot-scale three-stage CWs can remove organics from swine wastewater effectively. • Probabilistic approach was used to evaluate variability of organics removal. • Organics removal was little affected by influent loading rates and seasons. • Organics accumulation slowed down in the substrate under plant multiple harvesting. [ABSTRACT FROM AUTHOR]

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 NH 4 + -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. [ABSTRACT FROM AUTHOR]

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 15N-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 15N. Meanwhile, above-ground tissues of M. aquaticum had significantly higher biomass and TN content than below-ground ( P < 0.05). 15N mass balance analysis indicated that gas losses contributed 52.0% to the added 15N, but the N2O flux constituted only 7.5% of total gas losses. The dynamics of NO3−-N and N2O 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. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Although constructed wetlands (CWs) are used as one relatively low-cost technology for livestock wastewater treatment, the improvement of phosphorus removal in CWs is urgently needed. In this study, a three-stage pilot-scale CW system consisting of three surface flow CWs (SFCWs; CW1, CW2, and CW3) in series from inlet to outlet was constructed to treat swine wastewater (SW) from a lagoon. The CWs were planted with Myriophyllum aquaticum . Considering different inlet loading rates, three strengths of swine wastewater (low: 33% SW, medium: 66% SW, and high: 100% SW) were fed to the CW system to determine total phosphorus (TP) removal efficiency and clarify the important role of plant harvest. Results from the period 2014–2016 indicate that the three-stage CW system had mean TP cumulative removal efficiencies and removal rates of 78.2–89.8% and 0.412–0.779 g m − 2 d − 1 respectively, under different inlet loading rates. The TP removal efficiency and removal rate constant had temporal variations, which depended on temperature condition and the annual growth pattern of M . aquaticum . The harvested phosphorus mass was 15.1–40.9 g m − 2 yr − 1 in the CWs except for CW1 with high strength SW, and contributed 22.5–59.6% of TP mass removal rate by the SFCWs. The TP removal was mainly by adsorption and precipitation in the substrate in CW1 but by uptake and multiple harvests of M . aquaticum in CW2 and CW3. The results suggest the three-stage CW system planted with M . aquaticum is suited for removing high TP concentrations from swine wastewater with a high removal efficiency. However, TP removal in high strength SW amounted to 70.1 ± 23.3%, and the outflow concentration of 17.0 ± 14.9 mg L − 1 was still high. Optimal loading rates for high strength SW still need to be investigated for the CW system presented here. [ABSTRACT FROM AUTHOR]

The aim of this research was to assess the applicability of Myriophyllum ( M. ) aquaticum for swine wastewater treatment. Nitrogen (N) removal processes were investigated in M. aquaticum mesocosms with swine wastewater (SW), 50% diluted swine wastewater (50% SW), and two strengths of synthetic wastewater, 200 mg NH 4 + - N L −1 (200 NH 4 + - N ) and 400 mg NH 4 + - N L −1 (400 NH 4 + - N ). During a 28-day incubation period, the average NH 4 + - N and TN removal rates were 99.8% and 94.2% for 50% SW and 99.8% and 93.8% for SW, which were greater than 86.5% and 83.7% for 200 NH 4 + - N , and 73.7% and 74.1% for 400 NH 4 + - N , respectively. A maximum areal total nitrogen (TN) removal rate of 157.8 mg N m −2 d −1 was found in M. aquaticum mesocosms with SW. During the incubation period, the observed dynamics of NO 3 − - N concentrations in water and gene copy numbers of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), nirK and nirS in soil unraveled strong nitrification and denitrification processes occurring in M. aquaticum mesocosms with swine wastewater. The N mass balance analysis indicated that plant uptake and soil N accumulation accounted for 17.9–42.2% and 18.0–43.8% of the initial TN load, respectively. The coupled nitrification and denitrification process was calculated to account for, on average, 36.8% and 62.8% of TN removal for 50% SW and SW, respectively. These findings demonstrated that the N uptake by M. aquaticum contributed to a considerable proportion of N removal. In particular, the activities of ammonia-oxidizing and denitrification microbes responsible for nitrification and denitrification processes in M. aquaticum mesocosm accelerated NH 4 + - N and TN removal from swine wastewater. [ABSTRACT FROM AUTHOR]