Surface Flow Constructed Wetlands Research Articles

Peat as Substrate for Small-Scale Constructed Wetlands Polishing Secondary Effluents from Municipal Wastewater Treatment Plant

With the recent development of constructed wetland technology, it has become a mainstream treatment technology for the mitigation of a variety of wastewaters. This study reports on the treatment performance and pH attenuation capacity of three different configurations of small-scale on-site surface flow constructed wetlands (SFCW): T1 (Peat + Typha latifolia), T2 (T. latifolia alone), and T3 (Peat alone) treating secondary effluent from the Amherstview Water Pollution Control Plant (WPCP) for two treatment periods (start-up period and operational period). The aim of this study was to compare the nutrients removal efficiencies between the different treatments, as well as to evaluate the effects of substrate and vegetation on the wetland system. For a hydraulic retention time of 2.5 days, the results showed that all treatment systems could attenuate the pH level during both the start-up and operational periods, while significant nutrient removal performance could only be observed during the operational period. Peat was noted to be a better SFCW substrate in promoting the removal of nitrate (NO3-N), total nitrogen (TN), and phosphorus. The addition of T. latifolia further enhanced NO3-N and TN removal efficiencies, but employing T. latifolia alone did not yield effluents that could meet the regulatory discharge limit (1.0 mg/L) for phosphorus.

Macroinvertebrate Community in Subsurface-Flow Constructed Wetlands for Wastewater Treatment under High and Low Pollutant Stress in China

Constructed wetlands (CWs) for wastewater treatment had drawn much attention for their additional function of conserving freshwater ecosystems. The purpose of this study was to evaluate the macroinvertebrate biodiversity of two subsurface-flow and surface-flow hybrid CW systems (Qimei CW system (QCWS) and Kejiyuan CW system (KCWS)) under high and low pollutant stress in China. Nonmetric multidimensional scaling (NMDS) and canonical correspondence analysis (CCA) were used to analyze the water quality and aquatic macroinvertebrates community data. The results indicated that the subsurface-flow CW could conserve significant macroinvertebrate biodiversity (total taxon richness 17). The community structure was influenced by habitat types (i.e., subsurface-flow vs. surface-flow CWs) under low pollutant stress, and this influence was somehow masked by influence of water quality under high pollutant stress. Good pollutant removal rates were obtained in decreasing the concentrations of total nitrogen (66.37% and 27.28%), total phosphorus (58.93% and 37.55%), and loadings of biochemical oxygen demand (28.38% and 73.71%) in QCWS and KCWS, respectively. This study implied that subsurface-flow CWs could achieved good performance in both water purification and biodiversity conservation, which could provide a more solid basis for the application of subsurface-flow CWs.

Secondary effluent purification by a large-scale multi-stage surface-flow constructed wetland: A case study in northern China

Assessment of treatment performance in the large-scale constructed wetland (CW) for secondary effluent purification remains limited. The aim of this case study was to therefore to investigate the long-term treatment capacity of organics and ammonium pollutants in a large-scale multi-stage surface-flow (SF) CW fed with secondary effluents from the wastewater treatment plants (WWTPs) in northern China. The results for two-and-half-year study period indicated that the water quality parameters including chemical oxygen demand (COD) and ammonium (NH4+-N) met the Chinese Grade III of Environmental Quality Standards. The mass reductions of COD and NH4+-N were 53% (4032 kg ha−1 y−1) and 72% (511 kg ha−1 y−1), respectively. However, there was a significant positive correlation between influent loads and treatment performance. The optimal loading of 2.5 g m−2 d−1 for COD and 0.3 g m−2 d−1 for NH4+-N could be recommended for designing the sustainable large-scale multi-stage SF CW wastewater treatments.

Nitrite-dependent methane-oxidizing bacteria seasonally and spatially shift in a constructed wetland used for treating river water

Nitrite-dependent anaerobic methane oxidation (n-damo) process, performed by “Candidatus Methylomirabilis oxyfera” (M. oxyfera), can be an important methane sink in wetland anoxic layers. However, little is known about the distribution and variability of M. oxyfera-like bacteria in constructed wetlands (CWs). The current study investigated spatial and seasonal dynamics of M. oxyfera-like bacteria in a free water surface flow CW (FWSF-CW) used to improve river water quality and explored the influences of wetland environmental variables. In the FWSF-CW, M. oxyfera-like bacterial abundance was found to change considerably among both sampling sites and seasons, ranged between 8.99×105 and 4.34×106 16S rRNA gene copies per gram dry sediment/soil. Considerable spatial and seasonal variations of M. oxyfera-like bacterial richness, diversity, and community structure were also observed in the FWSF-CW. In addition, both nutrients and temperature were the key factors determining the community structure of wetland M. oxyfera-like bacteria.

Myriophyllum aquaticum Constructed Wetland Effectively Removes Nitrogen in Swine Wastewater.

Removal of nitrogen (N) is a critical aspect in the functioning of constructed wetlands (CWs), and the N treatment in CWs depends largely on the presence and activity of macrophytes and microorganisms. However, the effects of plants on microorganisms responsible for N removal are poorly understood. In this study, a three-stage surface flow CW was constructed in a pilot-scale within monospecies stands of Myriophyllum aquaticum to treat swine wastewater. Steady-state conditions were achieved throughout the 600-day operating period, and a high (98.3%) average ammonia removal efficiency under a N loading rate of 9 kg ha-1 d-1 was observed. To determine whether this high efficiency was associated with the performance of active microbes, the abundance, structure, and interactions of microbial community were compared in the unvegetated and vegetated samples. Real-time quantitative polymerase chain reactions showed the abundances of nitrifying genes (archaeal and bacterial amoA) and denitrifying genes (nirS, nirK, and nosZ) were increased significantly by M. aquaticum in the sediments, and the strongest effects were observed for the archaeal amoA (218-fold) and nirS genes (4620-fold). High-throughput sequencing of microbial 16S rRNA gene amplicons showed that M. aquaticum greatly changed the microbial community, and ammonium oxidizers (Nitrosospira and Nitrososphaera), nitrite-oxidizing bacteria (Nitrospira), and abundant denitrifiers including Rhodoplanes, Bradyrhizobium, and Hyphomicrobium, were enriched significantly in the sediments. The results of a canonical correspondence analysis and Mantle tests indicated that M. aquaticum may shift the sediment microbial community by changing the sediment chemical properties. The enriched nitrifiers and denitrifiers were distributed widely in the vegetated sediments, showing positive ecological associations among themselves and other bacteria based on phylogenetic molecular ecological networks.

A novel aerated surface flow constructed wetland using exhaust gas from biological wastewater treatment: Performance and mechanisms

In this study, a novel aerated surface flow constructed wetland (SFCW) using exhaust gas from biological wastewater treatment was investigated. Compared with un-aerated SFCW, the introduction of exhaust gas into SFCW significantly improved NH4+-N, TN and COD removal efficiencies by 68.30 ± 2.06%, 24.92 ± 1.13% and 73.92 ± 2.36%, respectively. The pollutants removal mechanism was related to the microbial abundance and the highest microbial abundance was observed in the SFCW with exhaust gas because of the introduction of exhaust gas from sequencing batch reactor (SBR), and thereby optimizing nitrogen transformation processes. Moreover, SFCW would significantly mitigate the risk of exhaust gas pollution. SFCW removed 20.00 ± 1.23%, 34.78 ± 1.39%, and 59.50 ± 2.33% of H2S, NH3 and N2O in the exhaust gas, respectively. And 31.32 ± 2.23% and 32.02 ± 2.86% of bacterial and fungal aerosols in exhaust gas were also removed through passing SFCW, respectively.

Spatiotemporal and species variations in prokaryotic communities associated with sediments from surface-flow constructed wetlands for treating swine wastewater

Microorganisms are the main mechanisms of pollutants removals in constructed wetlands (CWs) used for wastewater treatment. However, the different biological processes and variations of prokaryotic community in CWs remain poorly understood. In this study, we applied a high-throughput sequencing technique to investigate the prokaryotic communities associated with sediments from pilot-scale surface-flow constructed wetlands (SFCWs) treating swine wastewater (SW) of varying strengths. Our results revealed that highly diverse prokaryotic communities were present in the SFCWs, with Proteobacteria (16.44–44.44%), Acidobacteria (3.25–24.40%), and Chloroflexi (5.77–14.43%) being the major phyla, and Nitrospira (4.14–12.02%), the most dominant genus. The prokaryotic communities in the sediments varied greatly with location and season, which markedly altered the microenvironmental conditions. Principal co-ordinates analysis indicated that SW strength significantly influenced the community structure in sediments of the SFCWs, and canonical correspondence analysis illustrated that the shifts in prokaryotic communities were strongly related to NO3−–N and TN in winter; and in summer with NH4+N, NO3−–N, NO2−–N, TN, TP, SOM, and pH. In conclusion, the use of high-throughput sequencing greatly enhanced our understanding of prokaryotic communities with different functional groups in SFCWs.

Spatio-temporal shifts in the archaeal community of a constructed wetland treating river water

The distribution of archaeal community and the associated environmental variables in constructed wetland (CW), especially in free water surface flow CW (FWSF-CW), remain poorly understood. The present study explored the spatial and temporal dynamics of archaeal community in an FWSF-CW used for surface water treatment and evaluated the driving environmental variables. The archaeal density varied considerably among sites and seasons, ranging from 3.37×108 to 3.59×109 16S rRNA gene copies per gram dry sediment/soil. The archaeal population density was adversely affected by high temperatures and tended to be lower during summer than during spring and winter. Moreover, considerable spatio-temporal variations of archaeal richness, diversity and community structure also occurred in the FWSF-CW. Higher nutrient contents correlated with a lower archaeal richness and diversity. Nitrate and carbon/nitrogen ratio were found to play important roles in shaping the overall archaeal community structure. Euryarchaeota and Bathyarchaeota were the dominant archaeal phyla in wetland sediments, while Thaumarchaeota tended to be dominant in wetland soils. In addition, the wetland archaeal community was related to vegetation type.

Seasonality distribution of the abundance and activity of nitrification and denitrification microorganisms in sediments of surface flow constructed wetlands planted with Myriophyllum elatinoides during swine wastewater treatment

Surface flow constructed wetlands (SFCWs) planted with Myriophyllum elatinoides for treatment of swine wastewater were examined to evaluate the effect of season, segment (site S1, S2, and S3), and treatment (100mgL−1 TN, T1; 300mgL−1 TN, T2; 500mgL−1 TN, T3) on the activity, and abundances of nitrifying and, denitrifying microorganisms, and on the abundance of sediment bacteria. The activity and abundances of nitrifiers, denitrifiers, and the abundance of bacteria were the highest in T3 samples, especially in S1 (P<0.05). The potential nitrification rate (PNR) was highest in the summer and potential denitrification rate (PDR) showed an increasing trend over seasons. The abundance of ammonia-oxidizing bacteria (AOB) was strongly correlated with PNR, while abundance of denitrifying gene (nirK) was strongly correlated with PDR. These results indicate that M. elatinoides SFCWs for swine wastewater treatment stimulate the growth of nitrifiers, denitrifiers and bacteria in sediments.

Ammonia, phosphate, phenol, and copper(II) removal from aqueous solution by subsurface and surface flow constructed wetland.

Water pollution is a global problem. During current study, ammonia, phosphate, phenol, and copper(II) were removed from aqueous solution by subsurface and surface flow constructed wetland. In current investigation, distilled water was polluted with four contaminants including ammonia, phosphate, copper (Cu), and phenol. Response surface methodology and central composite design were applied to optimize pollutant removal during treatment by subsurface flow constructed wetland (SSFCW). Contact time (12 to 80h) and initial pollutant concentration (20 to 85mg/L) were selected as independent factors; some upper and lower ranges were also monitored for accuracy. In SSFCW, water hyacinth transplanted in two substrate layers, namely zeolite and cockle shell. SSFCW removed 87.7, 81.4, 74.7, and 54.9% of ammonia, phosphate, Cu, and phenol, respectively, at optimum contact time (64.5h) and initial pollutant concentration (69.2mg/L). Aqueous solution was moved to a surface flow constructed wetland (SFCW) after treating via SSFCW at optimum conditions. In SFCW, Typha was transplanted to a fixed powdered substrate layer, including bentonite, zeolite, and cockle shell. SFCW could develop performance of this combined system and could improve elimination efficacy of the four contaminants to 99.99%. So this combined CW showed a good performance in removing pollutants. Graphical abstract Wetlands arrangement for treating aqueous solution in current study.

Swine Farm Wastewater Treatment by Constructed Wetland Planted with Vetiver Grass

This research investigated the pollutant removal efficiencies in swine farm wastewater with Vetiveria zizanioides (L.) Nash (Sri Lanka ecotype) in a surface flow constructed wetland (SFCW). The SFCW units were set up to 3 treatments at 10, 15 and 30 cm water levels to find the proper depth for vetiver grass in wastewater treatment. The water quality indicator such as pH, temperature (T), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total kjeldahl nitrogen (TKN), total phosphorus (TP) and heavy metals (Cu, Fe, Pb, Zn) were analyzed and compared with terms of removal efficiency. The 30 cm water depth has a better removal efficiency of organic substance treatment (BOD and COD). The BOD, COD, TKN and TP removal efficiency had no statistically significant differences between the water depths. TP has the best removal efficiency with average 95.18-96.53%. The treatment of heavy metals such as Cu, Pb, Fe and Zn with vetiver grass in different water depths was showed no statistical significance since it can reduce only a small number of these metals. However, the results showed that the effluent from all the treatment units contained averages of BOD, COD, TKN and pH that followed Thailand’s swine wastewater quality standard.

Storm event-scale nutrient attenuation in constructed wetlands experiencing a Mediterranean climate: A comparison of a surface flow and hybrid surface-subsurface flow system

Among different Water Sensitive Urban Design options, constructed wetlands (CWs) are used to protect and restore downstream water quality by attenuating nutrients generated by stormwater runoff. This research compared the nutrient attenuation ability during a diverse population of storm events of two CWs: (a) a hybrid CW with multiple alternating surface flow (SF) and laterite-based subsurface flow (SSF) compartments, and (b) a single stage SF CW. Within-storm variability, nutrient concentrations were assessed at 2 to 3-h intervals at both the main inlet and outlet of each CW. Dissolved oxygen concentrations of the surface waters were also monitored at 10-min intervals using high frequency in situ sensors. Nutrient loads into the CWs were observed to be higher when a high rainfall event occurred, particularly after longer antecedent dry conditions. Longer hydraulic retention times promoted higher attenuation at both sites. However, the relative extent of nutrient attenuation differed between the CW types; the mean total nitrogen (TN) attenuation in the hybrid and SF CW was 45 and 48%, respectively. The hybrid CW attenuated 67% total phosphorus (TP) loads on average, while the SF CW acted as a net TP source. Periodic storm events transitioned the lentic CW into a lotic CW and caused riparian zone saturation; it was therefore hypothesized that such saturation of organic matter rich-riparian zones led to release of TP in the system. The hybrid CW attenuated the released TP in the downstream laterite-based SSF compartments. Diel oxygen metabolism calculated before and after the storm events was found to be strongly correlated with water temperature, solar exposure and antecedent dry condition during the pre-storm conditions. Furthermore, the SF CW showed a significant relationship between overall nutrient load attenuation and the change in oxygen metabolism during the storm perturbation, suggesting oxygen variation could be a useful proxy indicator of CW function.

Temporal dynamics of stormwater nutrient attenuation of an urban constructed wetland experiencing summer low flows and macrophyte senescence

The attenuation of urban stormwater nutrient is essential for maintaining ecological health of downstream waterways. Constructed wetlands (CWs) are widely used for stormwater management due to the economic and environmental benefits they create by attenuating nutrients. This research assessed stormwater nutrient attenuation in a surface flow CW located in Western Australia, by assessing data spanning decadal, seasonal and diurnal time-scales. The study site was built in 2004 and restored in 2010, and the significance of such restoration was also assessed in this research. The CW designed to minimize nutrient loads to downstream sensitive waterways despite experiencing Mediterranean climates with strong hydrological seasonality including prolonged low or no flow conditions during the dry summer periods and nutrient-rich pulses during the wet winter periods. Furthermore, seasonal ungauged water inputs and macrophytes senescence made the system complex to optimize nutrient attenuation. The annual average attenuation of nitrogen (N) and phosphorus (P) based nutrients were 2–4 times higher during the post-restoration periods than that observed during the pre-restoration periods. The attenuation of inorganic, organic, dissolved and total N was higher during the dry periods of the post-restoration regimes, while P species showed higher attenuation during the wet periods of the post-restoration regimes. Inorganic N showed greater attenuation than attenuation of inorganic P throughout the year. Baumea articulata and Schoenoplectus validus were the dominant macrophyte species across the site; B. articulata was estimated to store about 3 and 2 times higher N and P pools, respectively than that stored in S. validus. Low dissolved oxygen (DO) occurred in the site and DO showed a decreasing trend over the decade and a distinct diurnal signature of day-time peaks and night-time anoxia. Diurnal pattern in aquatic metabolism, defined as the daily fluctuation of DO levels within the water column of CW, was related to solar radiation and nutrient concentrations, and could be considered as a proxy of CW function.

Influence of substrate depth and particle size on phosphorus removal in a surface flow constructed wetland.

Substrate adsorption is one of the main processes by which redundant phosphorus is removed from wastewater in surface flow constructed wetlands (SFCWs). The physical properties of the substrate, such as depth and particle size, will influence the amount of phosphorus adsorption. This study was carried out in a long-running intermittent inflow constructed wetland that covered a total area of 940.4 m2 in the Shunyi District of Beijing, China. We investigated how the concentrations of four phosphorus fractions, namely calcium phosphate (CaP), iron phosphate (FeP), adsorbed phosphorus (AdsP), and organic phosphorus (OP), varied between the surface (0-10 cm) and subsurface (10-20 cm) substrate and among the different substrate particle sizes. The total phosphorus concentrations in the substrate ranged from 154.97 to 194.69 mg/kg; CaP accounted for more than 80% of the total phosphorus content. The concentrations of OP were significantly higher in the surface layer than in the subsurface layer, but the concentrations of inorganic phosphorus were not significantly different between the two layers. The CaP, AdsP, and OP adsorption capacities were greater for small-sized substrate particles than for large-sized substrate particles. The results from this study provide a theoretical basis for the construction of constructed wetlands.

Effect of salinity on nitrogen removal performance in a &lt;i&gt;Phragmites australis&lt;/i&gt; constructed surface flow wetland

利用芦苇湿地去除农业污水中的氮是博斯腾湖流域控制富营养化的重要手段.但是，污水中的盐分往往会抑制芦苇（Phragmites australis）湿地的除氮效果.为了探索不同盐度对芦苇湿地脱氮效果的影响和机制，研究4个不同的盐度梯度（淡水、2‰、5‰和10‰）对芦苇表流湿地中氮去除的影响，测定不同盐度下湿地表层（0~10.0 cm）和下层土壤（10.0~20.0 cm）中硝化、反硝化作用强度的变化.结果表明，盐度上升显著降低了湿地氮的去除率，但是不同离子形态的氮变化趋势并不一致.5‰和10‰盐度下的芦苇湿地中总氮、铵态氮去除率分别下降了9.03%、31.80%和23.10%、39.20%，亚硝态氮累积率分别上升了190%、690%，而硝态氮并未发生明显变化.相对于参与反硝化作用的菌群，盐度对参与硝化作用菌群的抑制作用更强是产生此现象的主要原因.除此之外，盐度升高导致植物根系泌氧减少也是土壤中的硝化作用强度降低的重要原因之一.

Application of a full-scale newly developed stacked constructed wetland and an assembled bio-filter for reducing phenolic endocrine disrupting chemicals from secondary effluent

To mitigate the detrimental risk of residual phenolic endocrine disrupting chemicals (PEDCs) from the discharge of sewage treatment plants (STPs) and to increase the utilization of constructed wetlands (CWs), both a stacked CW (SCW), comprising vertical and horizontal flow CWs, and an assembled bio-filter (ABF) were developed and their capability to remove PEDCs from STP discharge at high hydraulic loading rates (HLRs) of 0.5–2.0 m/d evaluated. The SCW and ABF showed different performance on PEDCs removal because of process structural difference. The removal percentages of PEDCs were associated with their octanol-water partition coefficients (LogKow), except 4-nonlyphenol (4-NP) whose apparent removal rate was affected by its precursors, and declined in the order of triclosan (TCS) at 80% and 69%, 4-t-octylphenol (4-t-OP) at 58% and 51%, estrone (E1) at 48% and 44%, and bisphenol-A (BPA) at 45% and 32% in the SCW and ABF systems on average, respectively. The efficiencies of SCW and ABF were superior to the single type of CWs, such as surface flow CW, vertical flow CW, and horizontal flow CW, in terms of removal rates or first-order removal rate constants. Recommended value of HLR for optimal utilization of SCW and ABF to ensure essential removal of PEDCs from STP discharge was between 1.5 and 2.0m/d.

Enhanced nutrient removal and mechanisms study in benthic fauna added surface-flow constructed wetlands: The role of Tubifex tubifex

This study designed a combined benthic fauna-T. orientalis-substrate-microbes surface-flow constructed wetlands (SFCWs) through the addition of T. tubifex. Results showed that, the removal efficiencies of nitrogen and phosphorus in the tested SFCWs achieved 81.14±4.16% and 70.49±7.60%, which were 22.27% and 27.35% higher than that without T. tubifex. Lower nitrate (2.11±0.79mg/L) and ammonium (0.75±0.64mg/L) were also observed in the tested SFCWs, which were 3.46mg/L and 0.52mg/L lower than that without T. tubifex. Microbial study confirmed the increased denitrifiers with T. tubifex. The lower nitrogen in effluent was also attributed to higher contents of nitrogen storage in sediment and T. orientalis due to the bioturbation of T. tubifex. Furthermore, with T. tubifex, higher proportions of particulate (22.66±3.96%) and colloidal phosphorus (20.57±3.39%) observed promoted phosphorus settlement and further absorption by T. orientalis. The outcomes of this study provides an ecological and economical strategy for improving the performance of SFCWs.

Anaerobic ammonium oxidation in sediments of surface flow constructed wetlands treating swine wastewater.

Anaerobic ammonium oxidation (anammox) was suggested to be involved in the nitrogen (N) removal process in constructed wetlands (CWs). Nevertheless, its occurrence and role in CWs treating swine wastewater have not been well evaluated yet. In this study, we investigated the diversity, activity, and role of anammox bacteria in sediments of mesoscale surface flow CWs (SFCWs) subjected to different N loads of swine wastewater. We found that anammox bacteria were abundant in SFCW sediments, as indicated by 7.5×105 to 3.5×106 copies of the marker hzsB gene per gram of dry soil. Based on stable isotope tracing, potential anammox rates ranged from 1.03 to 12.5nmol Ng-1 dry soilh-1, accounting for 8.63-57.1% of total N2 production. We estimated that a total N removal rate of 0.83-2.68kg Nyear-1 was linked to the anammox process, representing ca. 10% of the N load. Phylogenetic analyses of 16S ribosomal RNA (rRNA) revealed the presence of multiple co-occurring anammox genera, including "Candidatus Brocadia" as the most common one, "Ca. Kuenenia," "Ca. Scalindua," and four novel unidentified clusters. Correlation analyses suggested that the activity and abundance of anammox bacteria were strongly related to sediments pH, NH4+-N, and NO2--N. In conclusion, our results confirmed the presence of diverse anammox bacteria and indicated that the anammox process could serve as a promising N removal pathway in the treatment of swine wastewater by SFCWs.

Dynamics of chloroacetanilide herbicides in various types of mesocosm wetlands

Constructed wetlands (CWs) for pesticide mitigation from agricultural runoff became widespread in the last decade. However, comparison of different types of CWs at one location is missing. Therefore, site by site comparison of three different types (subsurface flow, surface flow and floating hydroponic root mat) of CWs treating four chloroacetanilide herbicides (acetochlor, s-metolachlor, metazachlor, dimethachlor) were carried out. All three planted systems are effective in removing the four herbicides with removal efficiency >92% after 9days. The metabolites ethane sulfonic acids (ESA) and oxanilic acids (OA) of the four herbicides peaked at 9days in the surface flow CWs with soil, but all the metabolites didn't peaked in the subsurface flow with gravel systems and the floating hydroponic root mat system after 21days. All the detected metabolites account about 20% of the mother compounds. There is no noticeable metabolites accumulation in the control system (no plants and no substrate), which indicate no microbial degradation taken place. Plant accumulation and soil adsorption are negligible for the removal of the four herbicides, which are <0.6%. In conclude, plants can enhance the removal of chloroacetanilide herbicides in all the CWs, and the floating hydroponic root mat is the most cost-efficient alternatives for chloroacetanilide herbicides removal due to the absence of substrate.

Enhancement of surface flow constructed wetlands performance at low temperature through seasonal plant collocation

In the present study, a novel seasonal plant collocation system (SPCS), specifically the Potamogeton crispus and Phragmites australis series system, was investigated to enhance the performance of surface flow constructed wetlands (SFCWs) at low temperature. Results of a year-round experiment showed that SPCS conquered the adverse effect of low temperature and achieved sustainable nutrients removal. In addition, during winter, removal efficiencies of NH4-N, TP, COD, and TN in SPCS were 18.1%, 17.6%, 10.1% and 5.2% higher than that in the control, respectively. P. crispus and P. australis complemented each other in terms of plant growth and plant uptake during the experiment period. Furthermore, it emerged that P. crispus could increase the quantity of ammonia oxidizing bacteria by 10.2%, due to its high oxygen enrichment ability. It is suggested that seasonal plant collocation has a promising future in SFCWs of areas being affected by climate change, e.g. northern China.