Constructed Wetland System Research Articles

Removal and fate of carbamazepine in the microbial fuel cell coupled constructed wetland system

Carbamazepine (CBZ), which is difficult to remove in the wastewater treatment system and easily forms toxic transformation products during the treatment process, is one of the priority pollutants of pharmaceuticals and personal care products (PPCPs). Increasing attention has been paid to explore their treatment technology without side effects from the treatment products. This study aims to reveal the removal and transformation of CBZ in the microbial fuel cell coupled constructed wetland (CW-MFC) system. The CW-MFC system was operated continuously at room temperature for nearly 80 days. The results show that CW-MFC system can effectively remove CBZ with an average removal rate of 97%. Three transformation products were identified by liquid chromatography−high-resolution mass spectrometry: 2-(2-oxoquinazolin-1(2H)-yl) benzoic acid (TP267), methyl 2-(2-oxoquinazolin-1(2H)-yl) benzoate (TP281), 2-(2,4-dioxo-3,4-dihydroquinazolin-1(2H)-yl) benzoic acid (TP283). Except TP281 in the influent, the other transformation products were formed in the system, which indicated that TP267 and TP283 were the main transformation products of CBZ. The formation pathway of transformation products could be explained by reactions including oxidation, hydrolysis, bond rupture and intramolecular reaction. The results also indicate that the CW-MFC system might be a promising technology for PPCPs treatment.

The application of steel slag in a multistage pond constructed wetland to purify low-phosphorus polluted river water

To investigate the effect of a constructed wetland (CW) with steel slag as the filler on water contaminated by low phosphorus levels, a multistage pond CW system was designed in this study. Low-phosphorus polluted river water was used as the research object. This study explored the effects of using steel slag as a CW filler on phosphorus removal and the total phosphorus (TP) purification effect of the wetland system. The results showed that the TP removal rates in the ecological pond, oxidation pond, surface flow wetlands and submerged plant pond were 5.17%, 8.02%, 21.56%, and 16.31%, respectively. Intermittent increases in phosphorus concentration were observed in the reactors and were caused by the decay of plant tissues, which released pollutants. Because steel slag was added to the filler, the TP concentrations in the effluent of the first- and second-level horizontal subsurface CWs increased by 151.13% and 16.29%, respectively, compared to the influent concentration. The 20th to 40th days of the test run was a period of rapid phosphorus release of the system. The use of steel slag has a potential risk of phosphorus release when applied in CWs used to purify low-phosphorus contaminated water bodies.

STUDI KELAYAKAN TEKNIK DAN BIAYA TERHADAP ALTERNATIF FITOREMIDIASI PADA AIR LIMBAH PENGOLAHAN KOPI

Sidomulyo Village is one of the coffee-producing location s in Silo District, Jember Regency. The coffee processing waste is no handling. Th e co ff ee p ro ce ss in g wa st ew at er could potentially lead to a decrease in environmental quality. Phytoremediation is an alternative technology that can be applied because of the availability of a waste storage pond in Sidomulyo , which ca n to become a pool for phytoremediation. Be si de s, phytoremediation is a simple technology that can reduce the concentration in coffee processing liquid waste. The purpose of this study was to compare phytoremediation alternatives using the aeration, circulation, and constructed wetland (CW) system , which is the most feasible to be applied to coffee processing wastewater treatment in Sidomulyo Village based on tech no lo gy and cost aspects. The stages of this research we re direct surveys of respondents, comparing the efficiency of phytoremediation performance with aeration, circulation and constructed wetland (CW) systems, analysis of techn ic al feasibility, and costs. The research results show that phytoremediation with the CW system is more t ha n feasible than aeration and circulation systems based on technological and cost aspects. Phytoremediation application using the CW system based on the tech no lo gy or technical aspects is more th an feasible because it easy application and has a shorter residence time (continuity). The value of the reduction efficiency of TSS, BOD, and COD parameters in coffee wastewater treatment using phytoremediation with the CW system is sequentially 29.80; 63.75; and 63.70%. Inventory cost of con structing CW for processing coffee wastewater of Rp. 64,050,000 with a storage capacity of 82.5 m 3 .

Evaluation of irrigation suitability potential of brewery effluent post treated in a pilot horizontal subsurface flow constructed wetland system: implications for sustainable urban agriculture

The use of untreated or partially treated wastewater reuse for urban and peri-urban agricultural irrigation is a common practice in developing countries like Ethiopia. Such practices, however, pose significant environmental and public health risks. The objective of this study was to evaluate the irrigation suitability of anaerobic digestion brewery effluent (ADBE) and two-stage horizontal subsurface constructed wetland post-treated ADBE (CWPBE). A series of pot experiments were conducted in a plastic - greenhouse system arranged in three sets of irrigation schemes: Treatment Group1 (TG1): municipal pipe tap water (MPTW) irrigated pots; Treatment Group2 (TG2): ADBE irrigated pots, and Treatment Group3 (TG3): CWPBE irrigated pots. Pots packed with the same amount of sandy clay loam soil and local tomato seeds sown were irrigated following an updated tomato irrigation schedule derived from the FAO CROPWAT stimulation model for 120 days. The findings from key irrigation water quality parameters showed that the CWPBE achieved the prescribed irrigation water standards with values of pH (7.4 ± 0.15), electrical conductivity (1.9 ± 0.11 dS.m−1), total suspended solids (25 ± 4.17 mgL-1), chemical oxygen demand (185.1 ± 1.66 mgL-1), total nitrogen (17.4 ± 0.7 mgL-1), total phosphorous (8.8 ± 0.26 mgkg-1), calcium (10.5 ± 3.6 mgkg-1), magnesium (4.9 ± 0.98 mgkg-1), sodium (4.4 ± 1.51 mgkg-1), potassium (2.3 ± 1.15 mgkg-1), sodium adsorption ratio (1.6 ± 0.34), and total coliform (8 ± 0.16×10−5 CFU/100 mL). Moreover, tomato plants grown in TG3 attained higher growth such as number of leaves (85.6 ± 4.68), plant height (92.2 ± 1.29 cm), stem diameter (13.1 ± 2.35 cm) and leaf area (35.5 ± 1.03 cm2) as well as higher biomass (61.2 ± 1.33 kgm−2) and fruit (46.4 ± 3.51 kgm−2) yields over other treatment groups. The results revealed that irrigation waters significantly improved both growth and yield parameters of tomato plants with the ascending order of TG1 < TG2 < TG3. Moreover, CWPBE showed minima short-term residual effect on soil physicochemical properties as compared to ADBE, and thus, it has potential suitability for agricultural irrigation reuse.

Bioreactor septic tank for on-site wastewater treatment: Floating constructed wetland integration

This study reports pollutant removal performance of two on-site wastewater treatment configurations: a field-scale bioreactor septic tank that received wastewater generated from the washrooms of an educational institute, and a combined pilot-scale bioreactor septic tank, floating constructed wetland system dosed with municipal wastewater. Each bioreactor septic tank was divided into seven compartments: two settling chambers, two anaerobic baffle reactors (ABR), two stone media-packed biowalls, and an effluent collection chamber. Wastewater hydraulic retention time (HRT) in the field and pilot-scale bioreactor septic tanks were 24 and 72 h, respectively. Nitrogen (N), phosphorus (P), organic, and coliform removal percentage in the field-scale bioreactor septic tank were 56%, 76%, 84%, and 88%, respectively. The pilot-scale bioreactor septic tank achieved 93%, 100%, 99.6%, and 99.9% removal, respectively. Pollutant removal in different compartments of the bioreactor septic tanks was achieved through physical, chemical, and microbial degradation pathways. Greater HRT of wastewater in the pilot-scale bioreactor septic tank improved overall removal performance. The floating constructed wetland provided an additional treatment of the pilot-scale bioreactor septic tank effluent; the mean nitrogen and coliform removal percentage was 35% and 91%, respectively. The hanging root-zone (inside the water column) of the floating constructed wetland supported pollutant removal kinetics. This study demonstrates the potential application of the bioreactor septic tank for on-site wastewater treatment and integration of floating constructed wetland as a polishing stage.

Pollutant Removal from Sewage in Tropical Climate by Constructed Wetland System: An Asset for Irrigation

In the global outlook, letting of untreated sewage in existing river bodies deteriorates the water quality. The seepage likely depreciates the quality of ground water too. The quality of groundwater with special reference to India has tremendously gone down in the past twenty years leading to sour taste. On the other hand, agriculture sector is deprived of water in many places of India. A solution can be arrived concurrently by treating sewage and consuming the effluent in agricultural sector. First order kinetics was applied in constructed wetland system at different flow rates and optimised. At optimised HLR, effluent met the standards of discharge that can be utilized for agricultural/ irrigational purpose. The emanating major pollutants can be effectively treated using constructed wetland system under tropical climate. A few clippings at the onsite treatment illustrated the diversity of species thus adjoining sustainable biodiversity and treatment. Thus in tropical countries like India, constructed wetland system might pave solution not only for the treatment of sewage but in deploying the effluent in agricultural sector. A clean ecosystem can be achieved with sustainability.

Treatment of Combined Dairy and Domestic Wastewater with Constructed Wetland System in Sicily (Italy). Pollutant Removal Efficiency and Effect of Vegetation

Dairy wastewater (DWW) contains large amounts of mineral and organic compounds, which can accumulate in soil and water causing serious environmental pollution. A constructed wetland (CW) is a sustainable technology for the treatment of DWW in small-medium sized farms. This paper reports a two-year study on the performance of a pilot-scale horizontal subsurface flow system for DWW treatment in Sicily (Italy). The CW system covered a total surface area of 100 m2 and treated approximately 6 m3 per day of wastewater produced by a small dairy farm, subsequent to biological treatment. Removal efficiency (RE) of the system was calculated. The biomass production of two emergent macrophytes was determined and the effect of plant growth on organic pollutant RE was recorded. All DWW parameters showed significant differences between inlet and outlet. For BOD5 and COD, RE values were 76.00% and 62.00%, respectively. RE for total nitrogen (50.70%) was lower than that of organic compounds. RE levels of microbiological parameters were found to be higher than 80.00%. Giant reed produced greater biomass than umbrella sedge. A seasonal variation in RE of organic pollutants was recorded due to plant growth rate Our findings highlight the efficient use of a CW system for DWW treatment in dairy-cattle farms.

Hybrid constructed wetlands system for domestic wastewater treatment under tropical climate: Effect of recirculation strategies on nitrogen removal

The objective of the present study was to evaluate the performance of a domestic wastewater treatment system based on hybrid constructed wetlands (CWs) under tropical climate. Moreover, the effect of different recirculation strategies particularly on nitrogen removal was also evaluated, including an analysis of nitrogen balance. The system was composed of a septic tank (pre-treatment), a horizontal subsurface flow and a vertical subsurface flow CWs. Three systems were analyzed: with the ornamental species Sagittaria lancifolia, the cattail Typha dominguensis and without vegetation as control. Evapotranspiration in the CWs was monitored during the warmest period of the year. First, the three systems were operated in serial mode evaluating two contact times of 2 d and 4 d. The three hybrid CWs were able to remove more than 92% of organic matter (COD, BOD5 and TOC), 88% of TSS and 99% (equivalent to 4.5 log10 units) of pathogens (Total Coliforms and Escherichia coli), regardless of plant selection and contact time. However, applying a contact time of 4 d resulted in higher removal of pathogens. Concerning nutrients removal, the combination of a contact time of 4 d and vegetation was required to achieve removal efficiencies over 66% for nitrogen and 90% for phosphorus. Finally, two recirculation strategies (RS) using a contact time of 4 d were evaluated in order to enhance nitrogen removal: RS1 (to the horizontal units) and RS2 (to the septic tank). The results yielded removal efficiencies similar to those obtained during serial operation in the case of organic matter (COD and BOD5) and phosphorus regardless of the RS applied. However, the removal of TSS decreased with RS2 as expected, due to the new load of solids coming from the septic tank. Nevertheless, nitrogen removal was increased over 85% in the hybrid CWs with vegetation, satisfactorily achieving system optimization. The highest nitrogen removal efficiency (≈ 97%) was obtained with the combination of RS2 and the plant species T. dominguensis. However, the use of the ornamental species S. lancifolia was not discarded since it provides an additional aesthetic benefit.

Microbial composition in different physical compartments of six constructed wetland systems in New Zealand

Microbial communities are vital for nutrient attenuation in surface-flow constructed treatment wetlands (CTWs). We used phospholipid fatty acid (PLFA) analysis to describe microbial communities in water, soil, sediment, and fresh humus compartments in six CTWs treating agricultural run-off in the Waikato Region of New Zealand. Sites ranged in their design and not all compartments could be sampled at all sites. Bacteria were the most dominant organisms in all compartments at all sites. The water compartment had less absolute abundance of all organisms, and the least relative abundance of all microbial groups except for total bacteria, at all sites. The water compartment also had a different microbial community composition than the other (more solid) compartments. Microbial communities were consistent across the 6 CTWs regardless of system design. There were more Gram-positive than Gram-negative bacteria, inferring a greater resistance and less resilience to perturbations suggesting CTW systems may not be able to respond rapidly to fluctuations in nutrient inputs due to the prevalence of K-strategist organisms. Actinomycetes were the least abundant microbial group but their role in CTWs is not clear. There were no correlations between microbial groups and compartment chemical properties. Reaching cleaner water aspirations would be facilitated by assessment of both community composition and function in CTW physical compartments.

A co-financing model for the mitigation of highway runoff pollution

Highway runoff impacts urban and natural ecosystems negatively. A financing model, that is economically feasible and accepted by all stakeholders, has been a limitation for the implementation of pollution control measures. A case-study on a 279-km Portuguese Highway is presented as a basis for a co-financing model. Runoff pollution load was estimated for quality indicators (TSS, COD, Zn, Cu, Pb), and the total cost of infiltration trenches, sand filters, bioretention filters, wet basins, dry basins and constructed wetlands systems was computed for four catchment scenarios. The effect of the equivalent catchment size and system type on the total cost was evaluated. The users 'Willingness to Pay' (defined as pay-per-user and availability to participate actively and financially) was assessed through a survey (1192 responses). A proposed co-financing model suggests that citizens will participate up to 36.8% of the constructed wetlands cost. This multidisciplinary approach results in potential outcomes that include a legal framework, proven technical solutions, and users' environmental responsibility.

FEASIBILITY STUDY OF CONSTRUCTED WETLANDS FOR THE TREATMENT OF DAIRY EFFLUENTS

This work aimed at characterizing the effluent of a small dairy in terms of flow and physical-chemical composition and at assessing constructed wetland for its treatment. The dairy produced an effluent with an average flow of 2.81 m³.d ‑ ¹ and the following characteristics: 574-4155 mg.L ‑ ¹ of BDO; 1531-7912 mg.L ‑ ¹ of TSS; and 23-173 mg.L ‑ ¹ of TKN. Using median values of BOD, three treatment systems were designed: batch activated sludge (BAS) and waste stabilisation ponds (WSP), commonly applied for the treatment of dairy effluents; and constructed wetlands (CW) as an alternative system. In terms of area requirements based on the removal of BOD, the BAS system (2.1 m²) was more advantageous than CW (15.0 m²) and WSP (46.5 m²). However, considering the removal of TKN and TSS, the WC system showed to be an attractive option for the treatment of the effluent studied. Next, a new CW system was designed aiming at removing BOD, TSS and TKN. In this case, the limiting parameter was the TKN, and not the BOD as expected. The designed CW system presented satisfactory hydraulic retention time (HRT) when compared to ranges reported in the literature, even when minimum, mean and maximum concentrations of NTK were considered for the design, corroborating the robustness of CW systems. The findings of this study confirm, therefore, the wide variation of the characteristics of dairy effluents as well as the ability of CW systems to absorb such variations without compromising the efficiency of the treatment system.

A constructed wetland system for bio-polishing palm oil mill effluent and its future research opportunities

This study was carried out to investigate the potential of Scirpus grossus in polishing final discharge of palm oil mill effluent (POME). The removal of total suspended solids (TSS) and chemical oxygen demand (COD) from POME by S. grossus was conducted in two different flow systems: a sub-surface (SS) and a free-surface (FS) batch constructed wetland (CW) systems. S. grossus was exposed to POME for 30 days. It was found that S. grossus plants performed better in TSS removal from POME in both systems (98 %) as compared with unplanted treatments (85 %). Plants developed root mats, which increased the filtration efficiency, leading to a reduction of TSS during the treatment period. Additionally, on day 7, the TSS removal by the FS system was higher than that by the SS system, with concentrations of 8 and 99 mg/L, respectively, on that day. The content of suspended solids in POME was believed to help this happen, as a system with more suspended solids will sediment faster than a system with less suspended solids. The removal of COD, on the other hand, did not differ between the two flow systems or between treatments with and without plants (96–97 %), indicating that sand medium played a significant role in COD removal from POME. It can be concluded that treatment combining sand medium, S. grossus, and the FS system is highly capable of polishing TSS and COD in final discharged POME. CW could be a promising green solution to improve the environmental ecosystem and ensure sustainability.

Efektivitas Sistem Constructed Wetland Dalam Menurunkan Jumlah Bakteri Patogen Pada Limbah Rumah Sakit

The wastewater produced in the hospital originates from activities carried out in the hospital, such as domestic waste, clinical waste, and laboratory waste. It contains many coliform bacteria. The bacteria were dangerous if it pollutes the environment because it can be the human’s disease. In general, hospitals have implemented wastewater treatment systems using disinfectants as tertiary treatment. Disinfectant itself can endanger the environment if used continuously. In addition, the use of disinfectants costs a lot. Therefore, this study uses a constructed wetland system as an alternative of the tertiary treatment using Echinodorus palaefolius. The results obtained from studies using this system are the percentage effectiveness of decreasing total coliform, BOD, nitrate, and phosphate. The removal efficiency of the total coliform, BOD, nitrate, &amp; phosphate was 96,17%, 62,92%, 69,98%, &amp; 63,53% respectively.

Pengaruh Kedalaman Rhizofer Tanaman Melati Air (Echinodorus palaefolius) Terhadap Kuantitas Oksigen Terlarut Pada Sistem Sub Surface Vertical Flow Constructed Wetland

Melati air has aerenchyma which plays an important role in the process of transferring oxygen to the rhizofer to qualify the oxygen demand in constructed wetland system. In this research, the Sub Surface Vertical Flow Constructed Wetland (SSVF CW) system was built to determine the effect of the depth of the Echinodorus palaefolius's rhizofer on the quantity of dissolved oxygen (DO) in the SSVF CW system. This system was designed to treat domestic wastewater with HRT of 4 days. SSVF CW was built using soil and stones of 1-2 cm, 2.5-5 cm, 7-10 cm as media. This study shows that melati air with an average root length of 47.25 cm and the longest root of 60 cm was able to influence DO concentration in the system. The removal efficiency of TSS, BOD, total ammonia, and phosphate was 93,48%, 89,39%, 59,39%, and 66,53% respectively. Whereas nitrate and TDS didn't decrease which could be possible due to the well running of nitrification process.

Pengolahan Limbah Tekstil dengan Metode Hibrid Menggunakan Sistem Filtrasi Bottom Ash dan Constructed Wetland

Textile wastewater that is discharged directly can cause damage to aquatic ecosystems and affects human health, thus requiring an effective alternative wastewater treatment. This research was conducted using a hybrid method that aims to eliminate pollutants in textile waste. The study was conducted by flowing textile waste into the bottom ash filtration and proceed to constructed wetland system with the residence time of 4 days. The results showed a decrease in the value of TDS, TSS, COD, and chromium by 16.47%, 97.09%, 72.14%, and 94.78% respectively in bottom ash output; and 13.12%; 57.53%; 7.52%; and 0.35% in the constructed wetland output. Therefore, the use of the hybrid method has been effective in treating textile waste by looking at the decrease in each test parameter.

Pollutant Removal from Sewage in Tropical Climate by Constructed Wetland System: An Asset for Irrigation

In the global outlook, letting of untreated sewage in existing river bodies deteriorates the water quality. The seepage likely depreciates the quality of ground water too. The quality of groundwater with special reference to India has tremendously gone down in the past twenty years leading to sour taste. On the other hand, agriculture sector is deprived of water in many places of India. A solution can be arrived concurrently by treating sewage and consuming the effluent in agricultural sector. First order kinetics was applied in constructed wetland system at different flow rates and optimised. At optimised HLR, effluent met the standards of discharge that can be utilized for agricultural/ irrigational purpose. The emanating major pollutants can be effectively treated using constructed wetland system under tropical climate. A few clippings at the onsite treatment illustrated the diversity of species thus adjoining sustainable biodiversity and treatment. Thus in tropical countries like India, constructed wetland system might pave solution not only for the treatment of sewage but in deploying the effluent in agricultural sector. A clean ecosystem can be achieved with sustainability.

Removal of phosphorus and ammonium from municipal wastewater treatment plant effluent by manganese ore in a simulated constructed wetland.

Natural manganese ore (NM) is selected as a distinguished constructed wetland (CW) substrate for nutrient pollutants removal,however, the study on municipal wastewater treatment plant (WWTP) effluent treatment remains scarce. The current study was to investigate the sorption characteristics of NM and the removal efficiency of ammonium and phosphorus from one WWTP effluent in a simulated vertical flow NM constructed wetland (NM-VFCW). Results indicated that NM could effectively sorb ammonium and phosphorus within 24 h, and the desorption ratio was less than 7%. The sorption of ammonium and phosphorus enhanced when increasing the particle size of NM, but was not sensitive with temperature. The removal efficiencies for ammonium and phosphorus were 65% and 76% in NM-VFCW, which were 61% and 31% in gravel VFCW. The much higher removal efficiency for phosphorus was mainly attributed to the precipitation of phosphorus which was identified by the SEM and EDS spectrum. Therefore, the manganese ore sand is highlighted as a powerful substrate for simultaneous advanced removal of phosphorus and ammonium in constructed wetland systems.

Removal of multiple heavy metals from mining-impacted water by biochar-filled constructed wetlands: Adsorption and biotic removal routes

Granular biochar made from walnut shells was layered into sand-based constructed wetlands (CWs) to treat simulated mining-impacted water (MIW). The results showed that the biochar media exhibited markedly high capacities for metal binding and acidity neutralization, supported notably better plant growth and mitigated metal transfer from the plant roots to the shoots. The addition of organic liquid wastes (domestic sewage and plant straw hydrolysation broth) stimulated biogenic sulfate reduction after 40 d of adaptation to effectively remove multiple heavy metals in the MIW. The microbial community compositions were prominently regulated by organic carbon, with desirable communities dominated by Cellulomonas and Desulfobulbus formed in the CWs for MIW biotreatment. The role of macrophytes in the CWs in MIW treatment was insignificant and was dependent on operation conditions and metal species. A biochar-packed CW system with liquid organic waste supplementation was effective in metal removal and acidity neutralization of MIW.

Spatial variation of physicochemical parameters in a constructed wetland for wastewater treatment: An example of the use of the R programming language

Introduction: The implementation of wastewater treatment systems such as constructed wetlands has a growing interest in the last decade due to its low cost and high effectiveness in treating industrial and residential wastewater. Objective: To evaluate the spatial variation of physicochemical parameters in a constructed wetland system of sub-superficial flow of Pennisetum alopecuroides (Pennisetum) and a Control (unplanted). The purpose is to provide an analysis of spatial dynamic of physicochemical parameters using R programming language. Methods: Each of the cells (Pennisetum and Control) had 12 piezometers, organized in three columns and four rows with a separation distance of 3,25m and 4,35m, respectively. The turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (N-NH4), organic nitrogen (N-org.) and phosphorous (P-PO4-3) were measured in water under in-flow and out-flow of both conditions Control and Pennisetum (n= 8). Additionally, the oxidation-reduction potential (ORP), dissolved oxygen (DO), conductivity, pH and water temperature, were measured (n= 167) in the piezometers. Results: No statistically significant differences between cells for TKN, N-NH4, conductivity, turbidity, BOD, and COD were found; but both Control and Pennisetum cells showed a significant reduction in these parameters (P&lt;0,05). Overall, TKN and N-NH4 removal were from 65,8 to 84,1% and 67,5 to 90,8%, respectively; and decrease in turbidity, conductivity, BOD, and COD, were between 95,1-95,4%; 15-22,4%; 65,2-77,9% and 57,4-60,3% respectively. Both cells showed ORP increasing gradient along the water-flow direction, contrary to conductivity (p&lt;0,05). However, OD, pH and temperature were inconsistent in the direction of the water flow in both cells. Conclusions: Pennisetum demonstrated pollutant removal efficiency, but presented results similar to the control cells, therefore, remains unclear if it is a superior option or not. Spatial variation analysis did not reflect any obstruction of flow along the CWs; but some preferential flow paths can be distinguished. An open-source repository of R was provided.

Enhancing nitrogen removal from anaerobically-digested swine wastewater through integration of Myriophyllum aquaticum and free nitrous acid-based technology in a constructed wetland.

Despite of low operation costs and convenient maintenance, the application of natural systems for swine wastewater treatment has been limited by large construction area and unsatisfactory effluent quality. Introducing ammonium high uptake aquatic plants and shifting nitrogen removal pathway from nitrate to nitrite in constructed wetlands (CWs) has been regarded as promising approach to promote their performances. This study aimed to establish nitrite pathway and enhance N removal via free nitrous acid (FNA)-sediment treatment and Myriophyllum aquaticum vegetation in the CWs treating anaerobically digested swine wastewater. Nitrite pathway was successfully and stably achieved in the M. aquaticum CW with FNA-treated sediment. The overall removal efficiencies of ammonium nitrogen and total nitrogen were 42.3±10.2% and 37.7±9.3% in the planted CWs with FNA-treated sediment, which were 76.3% and 65.4% higher than those in the conventional oxidation pond system, respectively. Microbial community analysis (qPCR and metagenomics) suggested that the nitrite pathway established through FNA-sediment treatment was based on the inactivation of nitrite oxidizing bacteria (lower nxrA gene abundance) and the reduction of relative abundances of NOB (especially Nitrobacter and Nitrospira). During the denitrification processes, the integration of M. aquaticum vegetation with FNA-sediment treatment can lower the nitrate reduction by decreasing narG gene abundances and decreasing the relative abundances of napA affiliated bacteria (especially Bradyrhizobium), while strengthening reduction of nitrite and nitrous oxide by increasing nirK and nosZ gene abundances and enriching the corresponding affiliated microbial taxa, Mycobacterium and Bacillus, respectively. Our findings suggest that applying FNA-based technology in CW systems is technically and economically feasible, which holds promise for upgrading current CW systems treating swine wastewater to meet future water quality requirements.