Comparison of the treatment performances of blast furnace slag-based and gravel-based vertical flow wetlands operated identically for domestic wastewater treatment in Turkey

In 2001, to foster the practical development of constructed wetlands (CWs) used for domestic wastewater treatment in Turkey, vertical subsurface flow constructed wetlands (30 m² of each) were implemented on the campus of the METU, Ankara, Turkey. The main objective of the research was to quantify the effect of different filter media on the treatment performance of vertical flow wetlands in the prevailing climate of Ankara. Thus, a gravel-filled wetland and a blast furnace granulated iron slag-filled wetland were operated identically with primarily treated domestic wastewater (3 m³ d⁻¹) at a hydraulic loading rate of 0.100 m d⁻¹, intermittently. Both of the wetland cells were planted with Phragmites australis. According to the first year results, average removal efficiencies for the slag and gravel wetland cells were as follows: total suspended solids (TSS) (63% and 59%), chemical oxygen demand (COD) (47% and 44%), NH₄⁺–N (88% and 53%), total nitrogen (TN) (44% and 39%), PO₄³⁻-P (44% and 1%) and total phosphorus (TP) (45% and 4%). The treatment performances of the slag-filled wetland were better than that of the gravel-filled wetland in terms of removal of phosphorus and production of nitrate. Since this study was a pioneer for implementation of subsurface constructed wetlands in Turkey using local sources, it has proved that this eco-technology could also be used effectively for water quality enhancement in Turkey.     

Recycling of aquaculture wastewater using charcoal based constructed wetlands

Abstract

The competitive demand for water makes it a scarce resource for agricultural use. This necessitates wastewater reuse for irrigation and any other agricultural purpose, especially in developing countries where treatment of wastewaters is not a priority. The aim of this study was to evaluate the performance of a charcoal-based constructed wetland (CBCW) in treating aquaculture wastewater. Aquaculture wastewater from a Research Fishpond Farm was treated in a CBCW planted with Sacciolepsis africana and Commelina cyannae for 5?days retention time. Raw wastewater and the treated wastewater from the constructed wetland (CW) was sampled and the physicochemical parameters determined. The performance of the CW in treating aquaculture wastewater was conducted. The result showed that the CBCW was capable of removing 50% TSS, 88% COD, 93% BOD_5, and 100% nitrate nitrogen. The pH and DO of the wastewater before treatment and after treatment ranged from 6.68 to 6.91 and 4.13 to 6.30?mg/l, respectively. Thus, CWs have great potential for the treatment of aquaculture wastewater and prevention of environmental degradation through wastewater treatment, thereby solving the problem of water scarcity for agriculture for optimum food production.     

Kinetics of pollutant removal from domestic wastewater in a tropical horizontal subsurface flow constructed wetland system: Effects of hydraulic loading rate

The treatment capacity of constructed wetlands is expected to be high in tropical areas because of the warm temperatures and the associated higher rates of microbial activity. A pilot scale horizontal subsurface flow constructed wetland system filled with river sand and planted with Phragmites vallatoria (L.) Veldkamp was set up in the southern part of Vietnam to assess the treatment capacity and the removal rate kinetics under tropical conditions. The system received municipal wastewater at four hydraulic loading rates (HLRs) of 31, 62, 104 and 146 mm day^?1. Removals of TSS, BOD₅ and COD were efficient at all HLRs with mean removal rates of 86–95%, 65–83% and 57–84%, respectively. Removals of N and P decreased with HLRs and were: NH₄-N 0–91%; TN 16–84% and TP 72–99%. First-order area-based removal rate constants (k, m year^?1) estimated from sampling along the length of the wetland from inlet to outlet at the four HLRs were in the range of 25–95 (BOD₅), 22–30 (COD), 31–115 (TSS), 5–24 (TN and TKN) and 41–84 (TP) at background concentrations (C*) of 5, 10, 0, 1.5 and 0 mg L^?1, respectively. The estimated k-values should not be used for design purposes, as site-specific differences and stochastic variability can be high. However, the study shows that domestic wastewater can be treated in horizontal subsurface flow constructed wetland systems to meet even the most stringent Vietnamese standards for discharge into surface waters.     

Nitrogen and phosphorus removal from wastewater by subsurface wetlands planted with Iris pseudacorus

Subsurface horizontal flow constructed wetlands are being evaluated for nitrogen (N) and phosphorus (P) removal from wastewater in this study through different gravel sizes, plant densities (Iris pseudacorus), effects of retention times (1 to 10 days) on N and P removal in continuously fed gravel wetland. The inlet and outlet samples were analyzed for TKN, NH₄-N, and NO₃-N, as standard methods. The planted wetland reactor with fine (SG) and coarse (BG) gravels removed 49.4% and 31.4% TKN, respectively, while unplanted reactors removed 43.4% and 26.8% TKN. Also, the efficiencies for NH₄-N were 36.7–43% and 21.6–25.4% for SG and BG planted reactors, respectively. The efficiencies for NO₃-N were 53.5–62.5% and 21.6–25.4% for SG and BG planted reactors, respectively. Roles of plants in SG reactors for O-PO₄ were 5–12% and 3–8% in BG. Also, the roles of plants in the reactors for TP were 9% and 7.4%. The minimum effective detention time for the removal of NO₃-N was 4–5 days. The subsurface constructed wetlands planted with I. pseudacorus can be an appropriate alternative in wastewater treatment natural system in small communities.     

柊叶和象草波式潜流人工湿地的对比研究

为探索柊叶和象草在人工湿地中的应用及其净化机理,该研究以柊叶和象草为人工湿地植物分别构建了波式潜流人工湿地系统,分析了柊叶和象草波式潜流人工湿地对生活污水中COD_(cr)、TN和TP的净化效果,观察了柊叶和象草两种植物在不同季节的生长状况。结果表明:经过15个月的连续运行,在表面水力负荷约0.3 m·d~(-1)的条件下,柊叶和象草波式潜流人工湿地平均去除率是COD_(cr)分别为66.1%和70.1%,TN分别为60.4%和63.7%,TP分别为74.1%和75.1%。两种植物生长良好,根系发达,象草的地上生物量是柊叶的2.1倍,地下生物量相当;冬季象草生长缓慢,柊叶部分叶片的四周干枯,但二者都不会枯亡。这说明两个人工湿地对COD_(cr)、TN和TP都具有较好的去除效果,但无显著性差异,柊叶和象草能明显提高潜流人工湿地的净化效果。     

Evaluation of the treatment performance of lab-scaled vertical flow constructed wetlands in removal of organic compounds,color and nutrients in azo dye-containing wastewater

The objective of this study is to examine the treatment performance of vertical flow intermittent feeding constructed wetland (VFCW) in removal of organic pollution, nutrients and color in azo-dye containing wastewater. The systems consisted of PVC reactors, some filling materials such as gravel, sand and zeolite and wetland plants including Typha angustifolia and Canna indica. The average treatment efficiency of the systems for COD, color, sulphate, NH₄-N, and PO₄-P were in the range of 57–63%, 94–99%, 44–48%, 39–44%, and 84–88%, respectively among the VFCW reactors. It is concluded that VFCW reactor system can effectively be used in the treatment of dye-rich wastewater, especially for the removal of color and in the reduction of COD. Biofilm formation and cleavage of azo bonds could be observed by SEM and FTIR results, respectively. Almost similar NH₄-N and PO₄-P removal were obtained in all reactors by using same amount of zeolite media.     

Occurrence of Pathogenic Free‐Living Amoebae and Bacterial Indicators in a Constructed Wetland Treating Domestic Wastewater from a Single Household

Constructed wetlands are effective wastewater treatment systems because of their ability to remove large amounts of organic matter and pathogens. The goals of this study were to characterize the presence of pathogenic free‐living amoebae and bacterial indicators (total and fecal coliforms), and to ascertain the removal efficiencies of physical and chemical pollutants, in a constructed wetland treating domestic wastewater from a single household. Influent and effluent samples were collected monthly over a ten‐month period for biological, physical and chemical analyses. Thirty‐two species of free‐living amoebae were isolated from the system. The genus Acanthamoeba was the most frequently encountered (59 %) and was removed from the wastewater with the greatest efficiency (80 %). Removal of bacteria was low, the highest removal rates were found in August (4 logarithmic units) and January (3 logarithmic units). The average removal efficiencies of suspended solids, BOD₅ and ammoniacal nitrogen were 71.5 %, 50.6 % and 13.1 %, respectively. The relatively low removal efficiencies of the various bacteriological, physical and chemical parameters suggest that the hydraulic retention time was probably insufficient for optimal treatment to occur. The effluent quality was unacceptable for unrestricted irrigation of crops that are eaten uncooked.     

The use of sub-surface constructed wetlands for wastewater treatment in the Czech Republic: 10 years experience

Wetlands have been intensively studied in the Czech Republic for more than 30 years, but the first full-scale constructed wetland (CW) for wastewater treatment was built in the Czech Republic in 1989. By the end of 1999, about 100 CWs were put in operation. The majority of the systems are horizontal subsurface flow (HSF) CWs and are designed for the secondary treatment of domestic or municipal wastewater. The size of CWs ranges between 18 and 4500 m² and between 4 and 1100 population equivalent (PE). Most frequently used filtration media are gravel and crushed rock with size fractions of 4/8 and 8/16 mm and Phragmites australis is the most commonly used plant. The treatment efficiency is high in terms of BOD₅ (88.0% for vegetated beds) and suspended solids (84.3% for vegetated beds). The removal of nutrients is lower for vegetated beds, and averages 51 and 41.6% for total phosphorus and total nitrogen, respectively.     

Treatment of high-strength wastewater in tropical constructed wetlands planted with Sesbania sesban: Horizontal subsurface flow versus vertical downflow

Treatment of various types of wastewaters is an urgent problem in densely populated areas of many tropical countries. We studied the potential of using Sesbania sesban, an N₂-fixing shrub, in constructed wetland systems for the treatment of high-strength wastewater. A replicated horizontal subsurface flow system and a saturated vertical downflow system was established with planted and unplanted beds to assess the effects of system design and presence of plants on treatment performance. The systems were loaded with a mixture of domestic and pig farm wastewater at three hydraulic loading rates of 80, 160 and 320 mm d^?1. The S. sesban plants grew very well in the constructed wetland systems and produced 17.2–20.2 kg dry matter m^?2 year^?1 with a high nitrogen content. Mass removal rates and removal rate constants increased with loading rate, but at 320 mm d^?1 the effluent quality was unacceptable and hydraulic problems appeared. Mass removal rates and removal rate constants were much higher than reported in other studies probably because of the high-strength wastewater, the high loading rates and the tropical conditions. Planted systems removed pollutants much more efficiently than the unplanted controls. Direct plant uptake constituted only up to 8% of the total-N removal and 2% of the P removal at the lowest loading rate, and was quantitatively of low importance compared to other removal processes. The significant effects of plants were therefore related more to their indirect effects on the removal processes. This study for the first time documents that S. sesban can be used in constructed wetland systems for the treatment of polluted water while at the same time producing a valuable N rich biomass that can be used for animal fodder or soil amendment.     

Collection strategies for quantifying protist assemblages in temperate headwater streams

We aimed at indicating some regularities of a constructed wetland treating agricultural runoff in China. The regularities, including the nitrogen removal capacity all year round, the nitrogen distribution pathways, and the nitrogen species removal kinetics, of a free water surface constructed wetland (2,800 m²) in the Dianchi Valley, which has been in operation for 27 months, were studied. The planted Phragmites australis and Zizania caduciflora were harvested biannually. The average inflow rate was recorded by an ultrasonic flow instrument, and then the hydraulic loading rate (HLR) and hydraulic retention time (HRT) were calculated. The average inflow and outflow concentrations of total nitrogen (TN), ammonia, and nitrate were measured, while the corresponding removal rates were calculated, showing better results than other constructed wetlands. Then the distribution pathways of nitrogen were analyzed, which indicated that plant harvesting was more important in wetland-treated agricultural runoff than in domestic wastewater. The reason for a good nitrogen removal capability and the obvious function of plants in the present wetland is the sound climate and intermittent inflow in the wetland. Results showed that inflow load had significant correction with both TN and ammonia removal efficiency. HLR, inflow rate, inflow nitrogen concentration, and temperature had significant and positive correction with both TN and ammonia removal. However, HRT had negative correction with both TN and ammonia removal, and the nitrate removal efficiency and parameters mentioned earlier were not significantly correlated. The rate constant values for nitrate and ammonia in summer were obviously larger than in winter. It is possible that bacterial and microbial activities were more active in summer than winter, and more conducive to bacterial and vegetative growth in summer than winter. Since this study was a pioneer for the implementation of constructed wetlands in China treating agricultural runoff, it has proved that this eco-technology could be used effectively for water quality enhancement in China and other areas with a similar climate.     

Effect of Cyclic Phytoremediation with Different Wetland Plants on Municipal Wastewater

Phytoremediation is a promising cleanup technology for contaminated soils, groundwater, and wastewater that is both low-tech and low-cost. The objective of this study was to investigate the ameliorative effect of phytoremediation on municipal wastewater (MWW). For this purpose, a phytoremediation garden was established using different aquatic plants species [Pistia stratiotes, Eichhornia crassipess, Hydrocotyle umbellatta, Lemna minor, Tyhpa latifolia, and Scirpus acutus ] in seven earthen pond systems (P1-P7) for the cyclic treatment of MWW. The physico-chemical analysis of MWW was carried out before and after the cyclic phytoremediation. Results showed that pH, EC and turbidity of MWW were reduced by 5.5%, 33.7%, and 93.1%, respectively after treatment (from P1 to P7). Treatment system also reduced total dissolved solids (TDS) by 35.2%, Cl by 61%, HCO₃ by 29.2%, hardness by 45.7%, Ca by 32.3% and Mg by 55.9%. Nitrate concentration was reduced by 77.6% but SO₄ was enhanced slightly. An ameliorative combined effect of wetland plants namely L. minor, T. latifolia, and S. acutus on MWW was noticed. Sequential phytoremediation with a mixture of plants was more effective than that relying only on a single plant species.     

Environmental conditions and the performance of free water surface flow constructed wetland: a multivariate statistical approach

During the past three decades, constructed wetlands have become an integral part of the suite of technologies for removing domestic and industrial wastewater contaminants. The use of constructed wetlands has disproportionately focused on domestic and agricultural wastewaters and storm water runoff and less on oil and gas-related produced water. In this context, the cumulative effect of environmental factors on the treatment/removal efficiency of contaminants in produced water is underserved by research. Therefore, this study assessed the effect of environmental factors (temperature, dissolved oxygen, oxidation–reduction potential, and pH) on contaminant removal efficiency in free water surface flow constructed wetland (FWSFCW) using ordinary least squares regression and experimental data from a waste treatment facility in Ghana. The results showed that environmental factors did not systematically vary across the experimental group and control set-up. Generally, the environmental factors explained relatively far less of the variance in contaminant removal efficiency compared with the plant species (Typha latifolia, Ruellia simplex and Alternanthera philoxeroides). Environmental factors cumulatively explained only 1.3%, 16.4%, 22.6%, and 5.6% of the variance in removal efficiency of BOD, COD, oil and grease, and total coliform bacteria, respectively. Temperature was the most important environmental predictor of the removal of BOD and phosphorus whereas DO was most important for removing nitrates and total coliform bacteria. ORP and pH were the most important predictors of COD, and oil and grease, respectively. These findings underscore the complex relationships among environmental factors and contaminant removal efficiency and the need for contaminant management practices and remedial techniques that address these complexities.

     

The Potential of Canna lily for Wastewater Treatment Under Indian Conditions

Low cost treatment of polluted wastewater has become a serious challenge in most of the urban areas of developing countries. The present study was undertaken to investigate the potential of Canna lily towards removal of carbon, nitrogen, and phosphorus from wastewater under sub-tropical conditions. A constructed wetland (CW) cell supporting vegetative layer of Canna lily was used to treat wastewater having high strength of CNP. Removal of biological oxygen demand (BOD₃) and chemical oxygen demand (COD) varied between 69.8–96.4% and 63.6–99.1%, respectively. C. lily could efficiently remove carbon from a difficult to degrade wastewater at COD:BOD ratio of 24.4. Simultaneous reduction in TKN and nitrate pointed to good nitrification rates, and efficient plant assimilation as the dominant nutrient removal mechanism in the present study. Suitable Indian agro-climatic conditions favored plant growth and no evident stress over the Canna plant was observed. High removal rate of 809.8 mg/m²-day for TKN, 15.0 mg/m²-day for nitrate, and 164.2 mg/m²-day for phosphate suggests for a possible use of Canna-based CW for wastewater treatment for small, rural, and remote Indian communities.     

Improving water quality in polluated drains with free water surface constructed wetlands

In Egypt, disposing of partially treated or untreated domestic and industrial wastewater into agricultural drains deteriorates their water quality. A growing interest in effective low-cost treatment of polluted water and wastewater has resulted in many studies on constructed wetlands.This study evaluates free water surface constructed wetlands (by far the largest application project is named “Lake Manzala Engineered Wetland [Egypt]”) utilized to improve the water quality in Bahr El Baqar drain, which is located at the northeastern edge of the Nile Delta. This drain discharges its water into Manzala Lake, which in turn has many fishing activities and is connected to the Mediterranean Sea. The full capacity of the constructed wetland system is 25,000 m³/day. Three various flow rate wetlands were investigated; five wetland beds of high flow rate of 0.344 m³/m²-day, five wetland beds of low flow rate of 0.048 m³/m²-day and reciprocated cells of flow of 500 m³/day.The concentrations of different contaminants along the constructed wetlands system were measured to determine the treatment efficiency. The effluent was compared with the Egyptian standards of water quality in agricultural drains (Law 48/1982). Due to the high percentage of the agricultural water drain, the concentrations of contaminants in the influent were relatively low. The percentages of removal for the different contaminants were BOD₅: 52%, COD: 50%, TSS: 87%, TDS: 32%, NH₄-N: 66%, PO₄: 52%, Fe: 51%, Cu: 36%, Zn: 47% and Pb: 52%. The natural vegetation considerably increased the value of dissolved oxygen in the treated effluent. There were little differences in the removal efficiency between the high and low flow rates beds in the system.     

COD,nutrient removal and disinfection efficiency of a combined subsurface and surface flow constructed wetland: A case study

A constructed wetland system composed of a subsurface flow wetland, a surface flow wetland and a facultative pond was studied from July 2008 until May 2012. It was created to treat the domestic sewage produced by a hamlet of 150 inhabitants. Monthly physicochemical and microbiological analyses were carried out in order to evaluate the removal efficiency of each stage of the process and of the total treatment system. Pair-wise Student's t-tests showed that the mean removal of each considered parameter was significantly different (α = 0.05) between the various treatment phases. Two-way ANOVA and Tukey's HSD tests were used to find significant differences between wetland types and seasons in the removal efficiency of the considered water quality parameters. Significant differences in percent removal efficiency between the treatment phases were observed for total phosphorus, total nitrogen, ammonia nitrogen and organic load (expressed as Chemical Oxygen Demand). In general, the wastewater treatment was carried by the sub-superficial flow phase mainly, both in growing season and in quiescence season. Escherichia coli removal ranged from 98% in quiescence season to >99% in growing season (approximately 2–3 orders of magnitude). The inactivation of fecal bacteria was not influenced by the season, but only by the treatment phase.     

Influence of recirculation over COD and N-NH4 removals from landfill leachate by horizontal flow constructed treatment wetland

Abstract

Treatment of landfill leachate is a challenge due to its complex chemical composition and high recalcitrance and because of high costs for conventional wastewater treatment. In our study, leachate from the Quitaúna Landfill, Sao Paulo Metropolitan Region, Brazil, was treated at a laboratory scale with a horizontal subsurface flow constructed treatment wetland (HF-CTW) operating under a recirculation regime. Two units planted with Heliconia psittacorum (HP) and Cyperus papyrus (CP), and one unplanted control unit were assessed. With a recirculation regime over 21?days, the planted units removed 40% of chemical oxygen demand (COD) while the control unit removed only 29%. True color removal efficiencies were 2, 22, and 23% for the control, HP, and CP HF-CTWs, respectively. The ammonium nitrogen removal efficiencies for a 21-day hydraulic retention time (HRT) were 63–81% for planted units and 72% for the control. The increase of the HRT from 7 to 21?days led to the enhancement of ammonium nitrogen removal but did not affect the COD and total nitrogen removals. This phenomenon is a consequence of leachate’s low biodegradability. The present study shows the importance of the HRT and plant presence for landfill leachate treatment using HF-CTWs.     

Treatment of domestic wastewater and production of commercial flowers in vertical and horizontal subsurface-flow constructed wetlands

In developing countries, the use of non-conventional plant species as emergent plants in constructed wetlands may add economic benefits besides treating wastewater. In this work, the use of four commercial-valuable ornamental species (Zantedeschia aethiopica, Strelitzia reginae, Anturium andreanum and Agapanthus africanus) was investigated in two types of subsurface wetlands for domestic wastewater treatment. Several water quality parameters were evaluated at the inlet and outlets of a pilot-scale system. Physical measurements were used to evaluate and compare the development of the ornamental plants under two patterns of flow in subsurface wetlands.The results for pollutant removal were significantly higher in the vertical subsurface-flow constructed wetlands (VFCW) for most pollutants. The average removals were more than 80% for BOD and COD; 50.6% for Org-N; 72.2% for NH₄⁺, 50% for Total-P and 96.9% for TC. Only two pollutants were removed in statistically higher percentages in the horizontal subsurface-flow constructed wetlands (HFCW) (NO₃^?, 47.7% and TSS, 82%). The pollutant removal efficiencies were similar to the results obtained in many studies with conventional macrophytes. Most ornamental plants survived the 12-month period of experimentation and their development depended on the type of constructed wetland they were planted. Z. aethiopica looked healthier and produced around 60 flowers in the HFCW. The other three species developed better in the VFCW, although A. andreanum died during the winter. S. reginae produced healthier flowers (and more) and bigger leaves and A. Agapanthus produced more leaves and more lasting flowers. This suggests that it is possible to produce commercial flowers in constructed wetlands without reducing the efficiency of the treatment system.     

Integrated constructed wetland systems employing alum sludge and oyster shells as filter media for P removal

This research aimed to investigate the technical feasibility of integrated constructed wetland system consisting of a pre-filter unit and a constructed wetland (CW), in series; packed with alum sludge (AS) and oyster shells (OS) as the filter media, respectively, for nitrogen and phosphorus removal from domestic wastewater. Based on the 240 days of operation from January to August 2007, this integrated system was highly effective in removing BOD, N, P and TSS compounds which were found to be 89.5%, 68.8%, 99.4% and 89.9%, respectively. After this period, the integrated system was modified as the CW and post-filter unit, in series. The post-filter of this modified integrated system was operated during 60 days with cover for light shield and during another 60 days with no cover from September to December 2007. The treatment performance of modified integrated system was effective in removing BOD₅, N, P and TSS compounds which were found to be 91.4%, 86.8%, 99.7% and 73%, respectively, during which the post-filter had operated with no cover. To simulate high rainfall conditions, the integrated system was tested under hydraulic shock loading at the overall hydraulic retention time of 0.7 day during one day. This hydraulic shock loading conditions made BOD₅, TN, TSS concentration increase, but made no effect on P concentration. Integrated system combined a pre-filter and a CW unit or a CW unit followed by a post-filter is recommended for use in domestic wastewater which should result in high treatment performance, especially on P removal.     

Life-cycle greenhouse gas emissions assessment and extended exergy accounting of a horizontal-flow constructed wetland for municipal wastewater treatment: A case study in Chile

The life-cycle greenhouse gaseous emissions and primary exergy resources consumption associated with a horizontal subsurface flow constructed wetland (HSSF) were investigated. The subject of study was a wetland for municipal wastewater treatment with a 700-person-equivalent capacity. The effects of two types of emergent aquatic macrophytes (Phragmites australis and Schoenoplectus californicus) and seasonality on greenhouse gas (GHG) gas emissions, the environmental remediation cost (ERC) and the specific environmental remediation cost (SERC) were assessed. The results indicate that GHG emissions per capita (12–22 kgCO2eq/p.e/yr) and primary exergy resources consumed (24–27 MJ/m³) for the HSSF are lower than those of a conventional wastewater treatment plant (67.9 kgCO2eq/p.e/yr and 96 MJ/m³). The SERC varied between 176 and 216 MJ/kg biological oxygen demand (BOD₅) removal, which should be further reduced by 20% for an improved BOD₅ removal efficiency above 90%. The low organic matter removal efficiency is associated with a high organic load and low bacterial development. Seasonality has a marked effect on the organic removal efficiency and the SERC, but the macrophyte species does not.     

Characterization of enterococci populations collected from a subsurface flow constructed wetland

Aims: The aim of this study was to identify and characterize the population of Enterococcus sp. in domestic wastewater as it flows through a constructed wetland. Methods and Results: Four hundred and eighty‐four Enterococcus isolates were collected from the inlet, various sites within and from the outlet of a plastic lined constructed wetland in College Station, TX. The wetland treated septic tank effluent that passed sequentially through two 1·89 m³ septic tanks and a 1·89 m³ pump tank allowing 48 l doses at a 24 l min^?1 rate. The Enterococcus isolates were identified to species using the commercial Biolog system. The 484 Enterococcus isolates were comprised of ten different species, including Enterococcus faecalis (30·6%), Enterococcus pseudoavium (24·0%), Enterococcus casseliflavus (12·8%), Enterococcus faecium (11·2%), Enterococcus mundtii (7·9%), Enterococcus gallinarum (6·2%), Enterococcus dispar (3·7%), Enterococcus hirae (2·1%), Enterococcus durans and Enterococcus flavescens both 0·8%. Of the 88 isolates collected from the inlet, only 9·1% of the isolates were identified as Ent. faecalis and Ent. pseudoavium (36·4%) was identified as the predominant species. Whereas of the 74 isolates collected from the outlet, the predominant species were identified as Ent. faecalis (29·7%). Species identification varied among sites within the wetland, but often Ent. faecalis was the predominant species. Conclusions: Our data suggest that while Ent. faecalis is the predominant species of Enterococcus found in domestic wastewater, the populations may shift during treatment as the wastewater flows through the constructed wetland. Significance and Impact of the Study: We found that shifts in Enterococcus species composition occurred during domestic wastewater treatment. This has implications for the identification of faecal pollution based on the presence of specific bacterial types associated with domestic wastewater.