Wetlands For Wastewater Treatment Research Articles

Performance assessment of hybrid constructed wetlands planted with different macrophytes for industrial wastewater treatment

ABSTRACT The aim of this study was to assess the performance of a laboratory-scale Hybrid Constructed Wetland (HCW) for industrial wastewater treatment planted with different macrophytes at different hydraulic retention times (HRT). The results revealed that the HCW planted with Phragmites australis and Lemna minor (PA/LMs), and the HCW planted with Typha latifolia and Lemna minor (TL/LMs) were able to improve the physicochemical proprieties of industrial wastewater, and were efficient enough to remove the heavy metals.

Machine learning exhibited excellent advantages in the performance simulation and prediction of free water surface constructed wetlands

Optimizing the design and operation parameters of free water surface constructed wetlands (FWS CWs) in runoff regulation and wastewater treatment is necessary to improve the comprehensive performance. In this study, nine machine learning (ML) algorithms were successfully developed to optimize the parameter combinations for FWS CWs. The scale effect of surface area on wetland performance was determined based on consistently smaller predictions (−6.2% to −28.9%) of the nine well-established ML algorithms. The models most suitable for FWS CW performance simulation and prediction were random forest and extra trees algorithms because of their high R2 values (0.818 in both) with the training set and low mean absolute relative errors (4.7% and 3.8%, respectively) with the test set. Results from feature analysis of the six tree-based algorithms emphasized the importance of water depth and layout of inlet and outlet, and revealed the negligible effect of the aspect ratio. Feature importance and partial dependence analysis enhanced the interpretability of the tree-based algorithms. The proposed ML algorithms enabled the implementation of an extended scenario at a low cost in real time. Therefore, ML algorithms are suitable for expressing the complex and uncertain effects of the design and operation parameters on the performance of FWS CWs. Acquiring datasets consisting of more extensive, uniform, and unbiased parameter combinations is crucial for developing more robust and practical ML algorithms for the optimal design of FWS CWs.

The Historical Development of Constructed Wetlands for Wastewater Treatment

Constructed wetlands (CWs) for wastewater treatment are engineered systems that are designed and operated in order to use all natural processes involved in the removal of pollutants from wastewaters. CWs are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment. The basic classification is based on the presence/absence of wastewater on the wetland surface. The subsurface flow of CWs can be classified according to the direction of the flow to horizontal and vertical. The combination of various types of CWs is called hybrid CW. The CWs technology began in the 1950s in Germany, but the major extension across the world occurred during the 1990s and early 2000s. The early CWs in Germany were designed as hybrid CWs; however, during the 1970s and 1980s, horizontal subsurface flow CWs were mostly designed. The stricter limits for nitrogen, and especially ammonia, applied in Europe during the 1990s, brought more attention to vertical subsurface flow and hybrid systems. Constructed wetlands have been used to treat various types of wastewater, including sewage, industrial and agricultural wastewaters, various drainage and runoff waters and landfill leachate. Recently, more attention has also been paid to constructed treatment wetlands as part of a circular economy in the urban environments: it is clear that CWs are a good fit for the new concept of sponge cities.

Effects of dissolved organic matter characteristics on the photosensitized degradation of pharmaceuticals in wastewater treatment wetlands

Wastewater treatment wetlands are aquatic systems where diverse dissolved organic matter (DOM) compositions physically interact. Complex photochemical behaviors ensue, leading to uncertainties in the prediction of indirect photodegradation rates for organic contaminants. Here, we evaluate the photosensitization ability of whole water DOM samples from a treatment wetland and wastewater treatment plant (WWTP) in North Carolina to photodegrade target pharmaceuticals. Optical characterization using ultraviolet-visible and excitation-emission matrix spectroscopy shows that wetland DOM has higher aromaticity than WWTP DOM and that WWTP secondary treatment processes increase aromaticity, overall molecular weight, and humic character of wastewater DOM. Our application of a reversed-phase HPLC method to assess DOM polarity distinctly reveals that a subset of the wetland samples possesses an abundance of hydrophobic DOM moieties. Hydroxyl radicals (˙OH) mediate the majority (>50%) of the indirect photodegradation for amoxicillin (AMX), atenolol (ATL), and 17α-ethinylestradiol (EE2), while singlet oxygen (1O2) is presumed to be solely responsible for the photodegradation of cimetidine (CME). Our findings suggest that hydrophobic interactions and improved accessibility to photogenerated reactive intermediates lead to significant increases in photosensitization efficiencies and overall indirect photodegradation rates of AMX, ATL, and EE2 for the hydrophobic wetland samples. In contrast, CME photosensitization yields are unaffected by polarity and trend positively with optical indicators of sunlight-induced DOM photobleaching and humification, suggesting that wetland processing favors faster 1O2 photogeneration. These relationships highlight the uncertainties in photosensitization yields and effects of DOM optical properties and polarity on the photochemical fate of organic contaminants.

Spatiotemporal water quality variability in a highly loaded surface flow wastewater treatment wetland.

This study evaluates spatiotemporal relationships between water quality parameters (WQPs), nutrients, suspended solids, and biochemical oxygen demand (BOD) concentrations within an engineered wastewater treatment wetland system in the Georgia Piedmont, USA. We explored factors related to treatment efficiency within a heavily loaded 630-m2 surface flow wetland system over a 2-yr period. Relationships between temperature, dissolved oxygen (DO), and oxidation-reduction potential (ORP) were observed; relationships were also seen between these WQPs and nutrient concentrations. Because temperature, DO, and ORP affect nitrogen (N) cycling rates, seasonal trends in N forms were evident in the system. Organic N and inorganic/organic phosphorus concentrations correlated with solids concentrations in the vegetated system without exhibiting seasonal trends. Surface water within the vegetated section generally exhibited anoxic conditions, leading to removal of nitrate-N within the system; however, limited mineralization and nitrification occurred, which greatly limited overall N removal. Plant selection and lack of maintenance likely led to high solids and BOD contributions to treatment wetland surface water, which varied substantially between and along monitored transects. Because so few studies have investigated treatment dynamics within treatment wetland cells, focusing solely on influent/effluent characterization, radical spatiotemporal variability may be the norm as opposed to the commonly accepted assumptions of relatively uniform pollutant degradation across treatment wetland cells. This spatiotemporal variability in WQPs underscores the dynamic nature of treatment wetlands and the need for routine maintenance, including sludge removal and plant harvesting.

Impact of a Natural Disturbance on the Performance and Microbial Communities in a Full-Scale Constructed Wetland for Industrial Wastewater Treatment

Impact of a Natural Disturbance on the Performance and Microbial Communities in a Full-Scale Constructed Wetland for Industrial Wastewater Treatment

Reliability and probability of organic and biogenic pollutants removal in a constructed wetland wastewater treatment plant in the aspect of its long-term operation

Reliability and probability of organic and biogenic pollutants removal in a constructed wetland wastewater treatment plant in the aspect of its long-term operation

Construction and implementation of floating wetpark as effective constructed wetland for industrial textile wastewater treatment

Fimbristylis dichotoma, Ipomoea aquatica, Pluchea tomentosa and their co-plantation (consortium FIP) autonomously degrade Orange 3R. Consortium FIP showed 84% removal of Orange 3R within 48 h, which is a higher dye elimination rate than individual plant systems. Oxidoreductase enzymes like tyrosinase (76%), varatryal alcohol oxidase (85%), lignin peroxidase (150%), riboflavin reductase (151%), laccase (171%), NADH-DCIP reductase (11%) and azo reductase (241%) were expressed in consortia FIP during Orange 3R degradation. UV–vis spectroscopy, enzyme activities, HPTLC, FTIR and GC-MS confirmed mineralization of Orange 3R into its metabolites. Microscopic investigation of root tissue revealed the harsh effect of dye on root tissues. Toxicity assessment on the HepG2 cell line demonstrated the toxic nature of Orange 3R, which gets reduced after phyto-treatment with consortia FIP. Floating wetpark of consortia FIP was found more efficient for the treatment of industrial textile waste and accomplished 87%, 86%, 75%, 49% and 46% removal of COD, BOD, color, TSS and TDS of effluent.

Does water flow type influence performances of reed based constructed wetland for wastewater treatment?

The application of Phragmites australis based constructed wetlands (CW) have been widely used in various climates and also used for secondary treatment of diverse wastewater and polluted water. This work compares the treatment performance of two Phragmites-based mesocosms: the first with surface horizontal flow (SF), and the other with subsurface horizontal flow (SSF), in the same conditions of feeding and climate. The results showed a significantly high mineral content of the effluent water exiting SSF-CW. The last one was significantly more efficient in terms of removal of Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), Total Nitrogen (TN), ammonium (NH4–N), and Total Phosphorus (TP) compared to SF-CW, i.e. 26.3, 3.12, 1.59, and 0.62 g. m−2. day−1 in the same order. The microbiological load reduction is also significantly higher in SSF-CW. On the contrary, the other parameters of pollution monitored do not allow the identification of a significant difference between SF- and SSF-CW. The atmospheric evapotranspiration value was higher in SSF-CW by 24.8 ± 20 mm. d−1, corresponding also to a higher harvestable biomass of Phragmites of 58.2 t. ha−1. year−1.

Constructed wetlands for rural domestic wastewater treatment: A coupling of tidal strategy, in-situ bio-regeneration of zeolite and Fe(Ⅱ)-oxygen denitrification

Constructed wetlands (CWs) offer a promising method to treat domestic wastewater in rural areas, but CWs usually limiting in nitrogen removal and large area. In this study, zeolite and pyrite were used to construct tidal wetlands to address the problems of insufficient oxygen supply and carbon source. The results show that the fully drained wetland achieved the highest ammonia removal load of 34.67 ± 1.72 g/(m2·d) with 8.57 ± 1.13 mg/L of effluent. Pyrite was found to compensate for the lack of carbon source in the denitrification process in half-drained wetland, which achieved a 78.36 ± 5.3% TN removal rate with 7.09 ± 1.85 mg/L effluent concentration. Pyrite released Fe(II) to promote nitrate reduction for denitrification in the subsequent flooded period. Microbial community analysis indicates that the tidal flow constructed wetlands simultaneously achieved nitrification and denitrification by the coupling of in-situ zeolite regeneration and Fe(II) oxidation denitrification.

Flower growing firms’ contribution to community water use management in Naivasha Sub County, Kenya

Water is a life necessity and is central to various social, economic and environmental aspects such as sanitation, health, economic growth, species protection, food etc. Companies require water for their production activities and can only thrive where the social, environmental and economic dimensions are well facilitated. Healthy and vibrant communities and environments cannot exist if water management is neglected. In a period of growing environmental concerns, collaborating and working collectively among entities in public sector, private sector and community based organizations to solve environmental problems seems more viable than ever. Naivasha area portrays an interesting case consisting of different formal and informal institutions as it has a long history of formal regulations as well as of self-organized water user groups all aimed at addressing sustainability in the use of water resources. With the observed lax on the authorities end in regulating the utilization of water resources among the diverse users, this study attempted to draw out the role played by flower growing firms in conjunction with the resident communities by examining how their activities affect the water resources available and the counter measures put in place to ensure availability of the resource for both mentioned stakeholders. The study was conducted among four wards in Naivasha Sub-County with the target population and subsequent sample size encompassing both flower growing firms and the residents inhabiting the selected areas. Majority of the residents interviewed confirmed having access to piped water. It was noted that the flower farms relied more on Lake Naivasha and ground water sources in the form of boreholes for their water requirements and made use of constructed wetlands for wastewater disposal and treatment to a larger extent. Waste water disposal systems were however not well developed among the resident communities with unrestricted disposal noted, leading to contamination of the surroundings. Whilst the local authorities confirmed efforts made by the flower growing firms in waste water disposal were efficient, their contribution to local water management efforts was noted to be low with their initiatives barely recognized by the surrounding communities. The study recommended use of low cost techniques among the resident communities in waste water disposal and uptake of well-designed corporate social responsibility codes and standards by the flower growing firms to manage water abstraction while assisting the surrounding communities in their water use management efforts.

Unveiling the role of sediments in phosphorus removal in pilot-scale constructed wetlands for swine wastewater treatment

The accumulation rate, fractions, and sorption capacity of phosphorus in sediments determine the removal efficiency and service life of constructed wetlands (CWs). Nine pilot-scale three-stage surface flow CWs were constructed to treat three loading rates of lagoon-pretreated swine wastewater, and surface sediment samples at initial and one-year treatment were collected to analyze the phosphorus fractions and sorption capacity. After one-year treatment, concentration of total phosphorus (TP) in sediments increased for high loading rates of wastewater, but remained stable for low loading rates. The annual accumulation rate of TP in sediments (Ma) was −43–445 mg kg−1 yr−1 at surface loading rate (SLR) of 36–355 g P m−2 yr−1. Their association could be described well using a sigmoid model, i.e., Ma = −23 + 538/(1 + exp.(−(SLR–262)/48)) (R2adj = 0.897, RMSE = 40.8, p < 0.01), indicating that the phosphorus accumulation rates in sediments were loading rate-dependent. The sum of inorganic phosphorus fractions contributed to 80–100% of the TP concentration, and accumulation of aluminum-bound phosphorus (AlP) and iron-bound phosphorus (FeP) was responsible for variability of TP concentration in sediments. Phosphorus sorption capacity of CW1 sediments increased by 1.3–1.8 times, attributed to increased pH, and concentrations of ammonium oxalate-extractable aluminum and iron in sediments due to the wastewater input. Selecting iron and aluminum-rich materials preferentially as substrates and regulating the ratio of metal ions to phosphorus in wastewater should be alternative enhancement strategies of CWs for phosphorus removal.

Monitoring of horizontal subsurface flow constructed wetlands for tertiary treatment of municipal wastewater

This paper explores the feasibility of the electrical resistivity (ER) method as non-invasive technique to detect dysfunctions of full-scale tertiary wastewater treatment wetlands, such as clogging, that ultimately limit the system lifetime and performance. ER measurements were carried out according to the Werner’s method on two (overloaded) horizontal subsurface wetlands (HSF-CW1 and HSF-CW2) operated in parallel since the end of 2017, while still achieving satisfactory treatment efficiencies. Layered clog-induced preferential flow pathways through the HSF-CW beds and premature deterioration of the wetland’s liner with a possible development of dead zones associated with a low/heterogeneous density of vegetation could be confirmed by analysis of ER profiles. These results suggest that the ER method is a promising and feasible technique, as simplified then adapted/adopted to local context, for better monitoring and assessment of treatment wetlands with early process failure.

Performance of Canna Indica based microscale vertical flow constructed wetland under tropical conditions for domestic wastewater treatment

Constructed wetlands (CWs) have great potential as low-cost natural wastewater treatment in developing countries. The present study appraises the performance of the vertical flow constructed wetland for domestic wastewater treatment. More specifically, the potential of Canna Indica in the removal of carbon, nitrogen, and phosphorus (CNP) from wastewater under tropical conditions. CW cell was fabricated with a vegetative layer of Canna Indica and tested with domestic wastewater. Based on the test results, Canna Indica shows a high Removal Efficiency (RE) of Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5) on the order of 87% and 91%, respectively. Similarly, nutrients removal efficiency for total nitrogen (TN), total phosphorus (TP) was found to be 97% and 98%, respectively. The investigation also revealed that there is considerable removal of sulfates with efficiency equal to 78.4%. Overall, the Canna Indica based CWs were found to be suitable for wastewater treatment in the tropical regions, provided a viable medium for treating the wastewater in peri-urban and rural areas of developing countries. Novelty statement This study investigates the performance of Canna indica based vertical flow wetlands for greywater treatment. The study investigates the results at different hydraulic retention times and loading rates. There are no much studies reporting the performance of this variety of plant species under a tropical humid climate. The results from the study can encourage adoption of this plant variety, indigenous to this part of the country, for wastewater treatment Highlights It could emphasize the importance of familiarity with constructed wetlands to comprehend the RE of various climatic zones. It is possible to highlight the Canna-based CW's efficiency in removing organics and nutrients from domestic wastewater. The possibility for field-scale Canna-based CW to remove pollution in tropical climates was investigated, and Decentralization of wastewater treatment at the household level to apply CWs that will improve wastewater quality.

Natural wetlands contribution on phosphorus removal in small northern communities in Canada

ABSTRACT This study focuses on understanding the role of passive wastewater treatment (wastewater lagoon plus wetland) in reducing the phosphorus discharge levels in a northern small community in Manitoba, Canada. The facultative lagoon system of that small community treats domestic wastewater and seasonally discharges effluent into a wetland that connects to Lake Manitoba. This research assesses phosphorus removal efficiency through the natural wetland during the vegetation growing season. The average total phosphorus (TP) concentration reduction for the observed treatment area of 1.3 ha was more than 70%, achieving the desired TP discharge concentration below 1 mg/L. Data analysis showed that the main accumulation of TP occurred at the 21–40 cm soil depth, which indicates the potential of natural wetland treatment applications under cold continental climate conditions as an effluent polishing step to satisfy regulatory requirements for phosphorus reduction.

A Review on Design Basis for Constructed Wetlands for Wastewater Treatment

Since last few years Constructed Wetlands (CWs) are being used to treat secondary or tertiary municipal or domestic wastewater effluents have been recognized as an effective means of “green technology” for wastewater treatment. Constructed wetlands (CWs) provide a natural way for simple, inexpensive, and robust wastewater treatment. The idea of natural management systems is the restoration of disturbed ecosystems and their sustainability for remuneration to nature. The Constructed wetlands (CWs) are designed to copy natural wetland systems, utilizing wetland plants, soil and associated microorganisms using various biological, physicochemical processes to remove unwanted constituents from wastewater effluents. This review paper studies various types of constructed wetlands, i.e., surface or subsurface, vertical or horizontal flow and their type of operation, i.e., continuous, batch or intermittent flow, loading rate, selection of plants and wastewater characteristics that affect the treatment efficiency. The design models with their suitability for various parameters and operational conditions such as Darcy’s equation, Kadlec and Knight Model (K-C* model), Arrhenius equation, and population equivalent calculation have been discussed. Lastly, future research requirements have been considered.

Response of constructed wetland for wastewater treatment to graphene oxide: Perspectives on plant and microbe

The wide application of graphene oxide (GO) increases its release into environment with less known on environmental effects. This work investigated 120-day interaction between GO (500 and 5000 μg/L) and constructed wetlands (CWs) planted with Iris pseudacorus. CWs showed the effective retention for GO via mature biofilm but less biodegradation. GO significantly induced enzyme activities (urease, neutral phosphatase, and catalase), which was attributed to increases in ecological association and enzyme abundance. GO decreased microbial biomass on day 30, but it had no impacts on day 120. The microbial community showed gradual self-adaption with time due to protection of antioxidant defense system (L-ascorbate oxidase, superoxide reductase, and glutathione related enzyme). The antioxidant enzymes (superoxide dismutase and peroxidase) and lipid peroxidation of Iris pseudacorus were increased by GO, accompanied by reduction on chlorophyll biosynthesis. Overall, the separate effects of GO on micro-regions and individual bodies in CWs were obvious, but it was acceptable that variations in pollutant removal were not evident due to synergetic role of plant-substrate-microbe. Organic matter and phosphorus removals reached to above 93%, and ammonia and total nitrogen removals in GO groups were reduced by 7–8% and 9–13%, respectively.

Evaluation of long-term phosphorus uptake by Schoenoplectus californicus and Phragmites australis plants in pilot-scale constructed wetlands

The aim of this study was to evaluate long-term phosphorus (P) retention in a pilot-scale system made of four horizontal subsurface flow (HSSF) constructed wetlands for wastewater treatment. Each wetland had an area of 4.5 m2 and was operated for nearly 8 years (2833 days). Two wetlands with Schoenoplectus californicus (HSSF-Sch) and the other two with Phragmites australis (HSSF-Phr) were planted. The P removal efficiency was 18% for both types of HSSF wetlands. The primary factors that correlated with long-term P retention efficiency in HSSF were phosphorus loading rate (PLR), hydraulic loading rate (HLR) and dissolved oxygen (DO). Average biomass production of HSSF-Phr and HSSF-Sch was 4.8 and 12.1 kg dry weight (DW)/m2, respectively. The P uptake by the plant increased over the years of operation from 1.8 gP/m2 to 7.1 gP/m2 for Phragmites and from 3.2 to 7.4 gP/m2 for Schoenoplectus over the same periods. Moreover, the warm season (S/Sm) was more efficient reaching 14% P uptake than the cold season (F/W) with 9%. These results suggest that both plants' P retention capacity in HSSF systems represents a sustainable treatment in the long term. Novelty statement Long-term (8 years) phosphorus uptake by Schoenoplectus californicus and Phragmites australis and retention in pilot-scale constructed wetlands are evaluated. Schoenoplectus californicus is an uncommon species that has been less studied for phosphorus uptake compared to Phragmites australis, a globally known species in constructed wetlands. Moreover, some studies evaluating the performance of constructed wetland systems for domestic wastewater treatment are usually limited in time (1–3 years). Therefore, this long-term study demonstrates that the plant plays an important role in phosphorus retention, especially the species Schoenoplectus californicus. So, the phosphorus uptake by plants can contribute between 9 and 14% of the phosphorus load of constructed wetland systems in early years of operation.

A full-scale anaerobic baffled reactor and hybrid constructed wetland for university dormitory wastewater treatment and reuse in an arid and warm climate

In low-income regions and small/medium communities, the use of conventional/mechanical methods for wastewater treatment is not always financially and technically feasible. Thus, nature-based solutions such as constructed wetlands (CW) appear as a more appropriate option. Additionally, there is limited application and reporting on the use and efficiency of this sustainable technology in arid and warm climates such as in the Middle East. In order to get a better insight into the feasibility of CWs under such climate and socio-economic context, a full-scale demonstration hybrid CW facility was built and monitored for the first time at a university campus in Iran for one year. The facility consists of an anaerobic baffled reactor, a vertical flow CW and a polishing horizontal subsurface flow CW and has a total area demand of 2.5 m2/pe. The goal was to evaluate the system's efficiency and investigate the need for one or two CW stages to reach the national effluent reuse standard. The CW were planted with local species (Arundo donax, Cortaderia selloana, Phragmites australis) and received 20 m3/day from a university dormitory at a hydraulic loading rate of 5 cm/day. The facility proved to be effective and removed 88.9%, 86.0%, 92.2%, 63.5%, 66.5%, and 65.7% of BOD5, COD, TSS, PO4-P, NH4-N, and NO3-N, respectively, while the effluent complied with the reuse standard. This study showed that hybrid CW can be effectively used under dry and warm climates using native plant species providing a technically feasible, cost-effective, and sustainable wastewater treatment solution.

Recent research challenges in constructed wetlands for wastewater treatment: A review

The review paper sis based on the analysis or nearly 700 research papers published during 2019 and the first half of 2020 and indexed by Web of Science under the password “constructed wetlands for wastewater treatment”. Out of this number 132 papers dealing with “new” topics such as new wastewaters treated in constructed wetlands (CW), new filtration materials, role of vegetation, floating treatment wetlands, microbiology of CW, greenhouse gas emissions from CWs, sustainability and secondary benefits of CWs. For the deeper analysis the supporting literature from previous periods has been cited. The analysis indicates increasing popularity and diversification of types and tasks of CWs. This supports the need for further research of processes and design-related properties of CWs. The research in full scale CWs and long-term studies are only rare and in order to upgrade the CWs technology, research must be also carried out in the field under full-scale conditions.