Constructed Wetlands For Wastewater Treatment Research Articles

Organic Pollutants Removal in a Hybrid Constructed Wetland Wastewater Treatment Plant with an Aeration System

This study presents the efficiency of TSS and organic pollutants (BOD5 and COD) removal in a hybrid constructed wetland wastewater treatment plant (VF-HF type) with an aeration system. This study was conducted over 6 years (2017–2022) in a facility with a capacity of 4.5 m3/day located in southeastern Poland and designed to treat real domestic wastewater from a school building. The studied facility consists of a three-chambered septic tank, a pumping station with an aeration system, and two beds with vertical and horizontal flow planted with giant miscanthus and willow. As a result of artificial aeration, the dissolved oxygen concentration in wastewater after mechanical treatment increased significantly, by an average of 1.18 mg O2/L, and was negatively correlated with wastewater temperature. The cumulative pollutant removal effects of the treatment plant (primary settling tank + VFCW + HFCW) were 81% for TSS, 98% for BOD5, and 89% for COD. There was no statistically significant effect of aeration on the organic pollutant removal effects in the VF bed, and such an effect was found for the temperature of wastewater entering the VF bed. The TSS, BOD5, and COD removal effects in the VF bed and BOD5 in the VF-HF system were positively correlated with air temperature. The technological reliability of the treatment plant was 98% for TSS and 100% for BOD5 and COD. The use of artificial aeration of wastewater makes it possible to achieve high organic pollutant removal efficiency in SSF CWs and to compensate for limitations due to the reduction in the area of constructed wetland beds.

Recycled clay bricks and palm kernel shell as constructed wetland substrate for wastewater treatment: An engineered closed circuit circular economy approach

Wastewater treatment using green technologies contributes significantly to a circular economy. Constructed wetlands (CW) using green substrates or recycled materials are low-cost cleaner technologies that further contribute to a closed circuit. This study assessed the performance of two recycled materials, Waste Clay Brick (WCB) and Palm Kernel Shells (PKS), as suitable substrates in a CW for wastewater treatment. Five (5) horizontal subsurface flow constructed wetlands (HSSF CW), designed and fabricated using galvanized steel, were set up for the treatment of domestic wastewater (sewage). The wetland cells were packed with small (WCBS, PKSS) or large (WCBL or PKSL) particle size substrates with one cell using sand as control. The CW operated under two hydraulic loading rates (HLR), 50l/d (HLR-1) and 80l/d (HLR-2). Overall, the effluent quality of HLR-1 was relatively better than HLR-2. pH and turbidity of effluent were satisfactory and within the Ghana Environmental Protection Agency (EPA) guidelines for discharge of wastewater into surface water bodies. For both hydraulic loading rates, the highest removal efficiencies of BOD5 (73.97%), COD (71.89%), TSS (90.82%), TP (71.13%), TN (49.41%) were recorded for WCB. Coliform removal was highest in the Palm Kernel Shell (98.6%), followed by the control (97.39%). Wastewater treatment efficiency decreased with increasing wastewater loading rates for all parameters in Waste Clay Brick and BOD5 and TP in Palm Kernel Shell. WCB demonstrated superior treatment potential compared to PKS for all parameters except coliform removal.

Influence of the Bed Temperature on the Operational Reliability of a Hybrid Constructed Wetland Wastewater Treatment Plant in South-Western Poland—A Case Study

The aim of this study was to assess the influence of atmospheric air temperature on the efficiency and reliability of pollutants removal from wastewater. The studied facility was a hybrid constructed wetland wastewater treatment plant with vertical and horizontal flow serving a single-family building in the village of Krajanów in south-western Poland. The operation of the facility was evaluated on the basis of studies conducted in 2021–2022. The tests included a physico–chemical analysis of wastewater treated mechanically in a settling tank and effluents from constructed wetland beds with the vertical and horizontal flow. The following parameters were determined: BOD5, COD, total suspended solids, total nitrogen, and total phosphorus. No statistically significant effect of air temperature on the analyzed pollutants removal levels was found. The temperature in the soil–plant bed never fell below 0 °C, and so the wastewater flowing through the beds never froze. The discussed facility was characterized by high efficiency and reliability of the tested pollutants removal across the seasons. The mean concentrations of pollutants in treated wastewater did not exceed the limit values specified in the currently binding legal act. It was shown that hybrid constructed wetlands can be successfully used for wastewater treatment in the climatic conditions of southern Poland.

Constructed Wetlands for the Wastewater Treatment: A Review of Italian Case Studies

Wastewater is one of the major sources of pollution in aquatic environments and its treatment is crucial to reduce risk and increase clean water availability. Constructed wetlands (CWs) are one of the most efficient, environmentally friendly, and less costly techniques for this purpose. This review aims to assess the state of the art on the use of CWs in removing environmental pollutants from wastewater in Italy in order to improve the current situation and provide background for future research and development work. To evaluate the CWs performances, 76 research works (2001–2023) were examined, and the parameters considered were the type of wastewater treated, pollutants removed, macrophytes, and the kinds of CWs utilized. The pollutant removal efficiencies of all CWs reviewed showed remarkable potential, even though there are biotic and abiotic factor-driven performance variations among them. The number of articles published showed an increasing trend over time, indicating the research progress of the application of CWs in wastewater treatment. This review highlighted that most of the investigated case studies referred to pilot CWs. This finding suggests that much more large-scale experiments should be conducted in the future to confirm the potential of CWs in eliminating pollutants from wastewater.

Microplastics removal and characteristics of a typical multi-combination and multi-stage constructed wetlands wastewater treatment plant in Changsha, China

Wastewater treatment plants (WWTPs) are an important source of microplastics (MPs) entering the aquatic environment. As environmental awareness increases, WWTPs are gradually using constructed wetlands (CWs) in the depth treatment stage. There were few studies related to MPs removal efficiency of CWs, especially in multi-stage and multi-combinations CWs. Therefore, we studied MPs characteristics and removal in a typical CWs WWTP in Changsha, comparing the MPs removal efficiencies of different processes in a WWTP, focusing on the MPs abundance variation in different stages CWs. Result showed that the MPs removal efficiency of Phase Ⅰ was 87.72% and that of Phase II was 80.65%. Approximate estimates showed that the daily discharge of MPs reached 7.20 * 108 items. The MPs removal efficiency of vertical flow CWs was 25.71%. The MPs removal efficiencies of secondary and tertiary horizontal subsurface flow CWs (HSSFCWs) were 32.00% and 21.43%. The MPs removal efficiencies of secondary and tertiary surface flow CWs were 23.53% and 12.50%. The MPs removal efficiencies of three bio-ponds were -23.08%, -12.90%, and -27.27%. Combined system of bio-pond + CWs reduced the MPs removal efficiency. The most dominant shape of MPs in wastewater was fibers. The most common MPs were polyethylene and polystyrene. The primary treatment in the Changsha WWTP had the highest MPs removal efficiency. Results of this investigation showed the multi-combination and multi-stage CWs WWTP can remove most of MPs in influent, which greatly reduced the amount of MPs discharged into the aquatic environment through WWTP and provided data for analyzing the distribution of MPs in the aquatic environment.

Impact of Implementing Constructed Wetlands on Supporting the Sustainable Development Goals

The United Nations Sustainable Development Goals’ (UN SDGs) action call promotes worldwide social, environmental, and economic prosperity. Each country developed a local plan to achieve the SDGs’ objectives and targets. The UN presents an annual global SDG progress report, based on an international indicator framework and regional available data. Wetland ecosystems contribute to the SDGs; however, more research is required to evaluate wetlands’ impact on sustainable development. This study investigates how implementing constructed wetlands (CW) at a local scale can contribute to achieving and promoting the SDGs with application in Kuwait. A preliminary design of a constructed wetlands wastewater treatment system is proposed alongside a local scoring framework based on regional information to assess the future projection of the SDGs in Kuwait. Overall, CW implementation plans contributed positively to improving the level of achievement of SDG 2: Zero Hunger, SDG 3: Good Health, SDG 6: Clean Water, SDG 7: Affordable and Clean Energy, and SDG 15: Life on Land. The analysis also highlights synergies that need to be considered for integrated environmental governance and enhanced policy coherence for Kuwait’s sustainable development management.

Towards Sustainable Wastewater Treatment: Bioindication as a Technique for Supporting Treatment Efficiency Assessment.

Constructed wetlands (CWs) are a promising alternative for conventional methods of wastewater treatment. However, the biggest challenge in wastewater treatment is the improvement of the technology used so that it is possible to remove micropollutants without additional costs. The impact of wastewater treatment in CWs on toxicity towards Aliivibrio fischeri, Daphnia magna and Lemna minor was investigated. The effects of feeding regime (wastewater fed in five batches per week at a batch volume of 1 L, or twice per week at a batch volume of 2.5 L) and the presence of pharmaceuticals (diclofenac and sulfamethoxazole), as well as the presence of Miscantus giganteus plants in CW columns (twelve of the 24 columns that were planted) were analyzed. A reduction in toxicity was observed in all experimental setups. The effluents from constructed wetlands were classified as moderately toxic (average TU for A. fischeri, D. magna and L. minor was 0.9, 2.5 and 5.5, respectively). The feeding regime of 5 days of feeding/2 days of resting resulted in a positive impact on the ecotoxicological and chemical parameters of wastewater (removal of TOC, N-NH4 and pharmaceuticals). Extended exposure of Miscantus giganteus to the wastewater containing pharmaceuticals resulted in elevated activity of antioxidant enzymes (catalase and superoxide dismutase) in leaf material.

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

A novel plant-girdling study in constructed wetland microcosms: Insight into the role of plants in oxygen and greenhouse gas transport

Constructed wetland (CW) wastewater treatments could be potential hotspots of greenhouse gas emissions to the atmosphere when removing pollutants, and the existence of wetland plants is an important factor in carbon and nitrogen cycling in CWs. In this study, the wetland mesocosms planted with Phragmites australis were conducted by using the novel plant-girdling method to assess the role of plants in potential O2, N2O, CO2 and CH4 production and transport in treating wastewaters with and without carbon sources. The system with girdling plant showed an obvious decrease of O2 release, but the higher O2 release rates of 157.78 mg O2 m−2 d-1 was obtained with an addition of carbon source. Average values of N2O, CO2 and CH4 fluxes in wetland mesocosms were 0.85 mg N2O m−2 d-1, −152.4 mg CO2 m−2 d-1 and 0.31 mg CH4 m−2 d-1, respectively when girdling and adding carbon source. Girdling plants and adding carbon source facilitated the removal of organics and nitrogen. Our study indicated that girdling wetland plants stimulated transformation of organics and nitrogen by net oxygen release from plants, but it could bring a raising greenhouse gas emission, which provided new slights into an improved understanding of wetland plants functioning in greenhouse gas transport and pollutant removal in CWs for wastewater treatment.

Crushed recycled glass as a substrate for constructed wetland wastewater treatment: a case study of its potential to facilitate pharmaceutical removal

The use of recycled glass as a substrate for constructed wetlands was assessed through two studies. The first study examined the dissipation of atenolol, carbamazepine, and sulfamethoxazole in mesocosm-modeled wetlands using glass or limestone gravel as substrates, with or without cattails (Typha spp.). Following pseudo-first-order kinetics, atenolol dissipated the fastest from the water surface of the mesocosms (t1/2~1 day), followed by sulfamethoxazole (t1/2~14 days), and carbamazepine (t1/2~48 days), with no significant differences across treatments. Increased half-lives were observed at greater depth, likely due to light screening. A Monte Carlo sensitivity analysis diagnosed sunlight absorption rates and second-order hydroxyl-mediated indirect photolysis rates to be the main sources of uncertainty in our dissipation rate estimates, compared to our observed rates. The second study examined in situ pharmaceutical removal in tertiary pilot-scale subsurface filters made of crushed recycled glass or sand in a wastewater treatment facility in Manitoba, Canada. Glass and sand showed no significant differences for pharmaceutical removals; atenolol and metoprolol were removed below limits of detection, while carbamazepine and sulfamethoxazole persisted over a retention time of 24 h. Overall, recycled glass performed similarly to traditional substrates for wetland-based wastewater treatment.

Improving Nutrient Removal in Constructed Wetland Wastewater Treatment

The percentage pollutant removal obtained by the previous work were very good in terms of BOD5 which was 95% removal, TSS was 97% removal, but unsatisfactory in terms of NH4-N, NO3-N and P which was 39%, 41% and 44% removal respectively-The effect of recycling portion of the effluent discharged from the 2ND. Cell, of a VSSF constructed wetland back to the 1ST. cell on the nutrient removal efficiency of the wetland was studied in this research.The intermittent feeding of influent and the recycled quantity had good effect on system aeration by dissolving the air trapped in the voids of the substrates before each doss and using it to activate aerobic bacteria.The Nitrification and denitrification were enhanced by the recycling process. Recycling effluent with low BOD & COD when mixed with raw wastewater infeed will increase system aeration which helps the nitrification process and when most of the oxygen has been consumed, by microorganisms during biological and chemical degradation of pollutant, than the denitrification process will start and transfer the NO3-, ultimately, to N2 gas.The hydrology condition of the system was good, the water was running in the constructed wetland in a laminar form and the detention time was highest in July and lowest in January as expected due to the effect of evapotranspiration which reaches its highest in July and lowest in January.The maturity of reed plant and extension of their stems and roots may have a positive influence on:- Aerobic condition required for the nitrification process and BOD5 removal by supplying more air from the outside atmosphere to the system.- Adsorbing of heavy metal and metal ions on the extended roots of reed plant.- Increased nutrient uptake by reed plants which results in lowering nutrient in effluent.

Pharmaceutical compound removal efficiency by a small constructed wetland located in south Brazil.

The fate of pharmaceuticals during the treatment of effluents is of major concern since they are not completely degraded and because of their persistence and mobility in environment. Indeed, even at low concentrations, they represent a risk to aquatic life and human health. In this work, fourteen pharmaceuticals were monitored in a constructed wetland wastewater treatment plants (WWTP) assessed in both influent and effluent samples. The basic water quality parameters were evaluated, and the removal efficiency of pharmaceutical, potential for bioaccumulation, and the impact of WWTP were assessed using Polar Organic Chemical Integrative Sampler (POCIS) and biofilms. The pharmaceutical compounds were quantified by High Performance Liquid chromatography coupled to mass spectrometry. The sampling campaign was carried out during winter (July/2018) and summer (January/2019). The WWTP performed well regarding the removal of TSS, COD, and BOD5 and succeeded to eliminate a significant part of the organic and inorganic pollution present in domestic wastewater but has low efficiency regarding the removal of pharmaceutical compounds. Biofilms were shown to interact with pharmaceuticals and were reported to play a role in their capture from water. The antibiotics were reported to display a high risk for aquatic organisms.

Effects of substrate combinations on greenhouse gas emissions and wastewater treatment performance in vertical subsurface flow constructed wetlands

Climate warming would be generally influenced by the quantity and component of greenhouse gases during the carbon and nitrogen removal in constructed wetlands (CWs). In this study, the impacts of the combinations by walnut shell (organic-rich substrate improving denitrification), manganese (Mn) ore (electron-exchange substrate transferring CH4 to CO2) and activated alumina (phosphorus-adsorption substrate) on global warming potentials (GWPs) were investigated to propose a strategy for both mitigating GWPs and performing well in wastewater treatment. During hybrid CWs, the highest COD and TP removal efficiencies were respectively 89.4% and 98.1% in CWs with the substrate combination of Mn ore and activated alumina, and the highest TN removal efficiency was in CWs with walnut shell and Mn ore. The substrate combination of walnut shell and Mn ore would simultaneously strengthen the nitrification and denitrification process resulting in the lowest N2O flux in CWs. The combinations of Mn ore with walnut shell or activated alumina could significantly decrease the GWPs through promoting the conversion of CH4 to CO2 due to the better redox potential environment favorable for methanotrophs (pmoA) instead of methanogenesis (mcrA) provided by Mn ore. This study provided a feasible way to mitigate climate warming during wastewater treatment in CWs by using substrate combination of Mn ore and walnut shell.

Research on perfermance improvement of constructed wetland wastewater treatment system

Constructed wetland is a kind of wastewater ecological treatment technology. It has the advantages of low investment, convenient operation and management, stable water quality, and has certain landscape effects. Therefore, it is widely used in the field of wastewater treatment. However, this technology still has certain problems in practical engineering applications, such as irregular design and clogging, resulting in limited service life and processing performance of the wetland. The type selection of constructed wetlands, matrix type and particle size, plant type and configuration, and water inflow mode and operating parameters are the main factors affecting the operating life and purification effect of constructed wetlands. Based on the author’s practice, the article introduces in detail the current process structure, basic design methods and economic and technical comparison of constructed wetland wastewater treatment for reference by relevant scientific research and design units.

Productivity and chemical properties of Salix viminalis in a horizontal subsurface flow constructed wetland during long-term operation

The paper presents the results of a study of selected parameters of common osier (Salix viminalis) biomass sampled annually, over a 12-year period, from a constructed wetland wastewater treatment plant. The focus of the study was on parameters that were relevant to biomass energy management. The study was conducted in a constructed wetland wastewater treatment plant consisting of one horizontal flow bed with a total area of 186 m2, planted with osier willows. The following biomass parameters were analysed: biomass yield, volume, humidity, ash content, higher and lower heating values, and contents of N, P, K in different parts of plant stems. The study showed that osier biomass harvested from the investigated constructed wetland system could be used as an energy source in thermochemical processes. The higher and lower heating values were similar to those obtained by other authors (18.13 and 17.38 MJ·kg−1, respectively). The energy yield (17.49 MJ·m−2) and energy density (3486–5411 MJ·m−3) were also calculated. Young shoot parts had higher ash and micronutrient contents and lower energy parameters than old parts.

Long-term impacts of graphene oxide and Ag nanoparticles on anammox process: Performance, microbial community and toxic mechanism

The increasing application of engineered nanoparticles (NPs) has posed an emerging challenge to constructed wetland wastewater treatment. The performance, microbial community and toxic mechanism of anammox-based unplanted subsurface-flow constructed wetlands (USFCWs) were investigated under the long-term exposure of different graphene oxides (GOs) and Ag NP concentrations. Results showed that the addition of GO could promote TN removal, manifesting as function anammox bacteria C. Anammoxoglobus having a relative high abundance, for GO did not cause significant damage to the cell integrity though there was an increase in ROS concentrations. TN removal would not be obviously affected under exposure of 1 mg/L Ag NPs, for the function gene related to cell biogenesis and repair was up-regulated; while the addition of 10 mg/L Ag NPs would have an inhibiting effect on TN removal in the USFCWs, for the disappearance of some species having anammox ability. Key enzymes of anammox process (NIR and HDH) decreased to some extent under GO and Ag NP exposure, and function gene of defense mechanisms had an increase trend in samples.

Maximizing the energy harvest from a microbial fuel cell embedded in a constructed wetland

Direct energy harvesting from the newly established constructed wetland-microbial fuel cell (CW-MFC) offers it a competitive position compared with traditional constructed wetlands (CWs) to allow the CWs for wastewater treatment and concomitantly achieve power generation. However, the integration of MFC into CWs always faces a large portion of energy losses due to the existence of higher internal resistance. This paper reports tests of a novel strategy, namely a capacitator engaged duty cycling (CDC) strategy, to harvest energy from an open air bio-cathode CW-MFC. Results show that with duty cycle value of 31.6% (D = 31.6%), the effective charge obtained from CDC strategy is 19.81% higher than the conventional continuous loading (CL) mode within the same discharging time. With a lower D value of 20% (D = 20%), the total charge harvested increased about 25.0%. The CDC operation mode shows advantages over the higher internal resistance system and contributes to a higher normalized COD removal rate. This operation strategy can minimize the energy losses with a suitable D value. It is a simple but effective way to maximize the energy harvesting from the CW-MFC system.

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.

Long-term investigation of constructed wetland wastewater treatment and reuse: Selection of adapted plant species for metaremediation

A highly diverse plant community in a constructed wetland was used to investigate an ecological treatment system for human wastewater in an arid climate. The eight-year operation of the system has allowed the identification of a highly adapted and effective plant consortium that is convenient for plant-assisted metaremediation of wastewater. This constructed wetland pilot station demonstrated effective performance over this extended period. Originally, there were twenty-five plant species. However, because of environmental constraints and pressure from interspecific competition, only seven species persisted. Interestingly, the molecular phylogenetic analyses and an investigation of the photosynthetic physiology showed that the naturally selected plants are predominately monocot species with C4 or C4-like photosynthetic pathways. Despite the loss of 72% of initially used species in the constructed wetland, the removal efficiencies of BOD, COD, TSS, total phosphorus, ammonia and nitrate were maintained at high levels, approximately 90%, 80%, 94%, 60% and 50%, respectively. Concomitantly, the microbiological water tests showed an extremely high reduction of total coliform bacteria and streptococci, about 99%, even without a specific disinfection step. Hence, the constructed wetland system produced water of high quality that can be used for agricultural purposes. In the present investigation, we provide a comprehensive set of plant species that might be used for long-term and large-scale wastewater treatment.

The possibility of using plants from hybrid constructed wetland wastewater treatment plant for energy purposes

In recent years, constructed wetland systems are used widely for the purification of small amounts of wastewater because they provide very high effects of removing impurities. The existing research results show that constructed wetland systems can be used not only for highly efficient wastewater treatment, but at the same time in order to produce biomass for energy purposes.The aim of this paper was to determine the possibilities of energy use of the plants: common reed, willow, Jerusalem artichoke, giant miscanthus, obtained from constructed wetland system.The yield of common reed was the highest compared to the other plant species used in analyzed object and amounted to 13.6MgDMha−1 and then 8.7MgDMha−1 for willow. The lowest dry matter yield was 5.9MgDMha−1 in the case of Jerusalem artichoke.High Heating Value was similar in all analyzed plants (17.9–19.2MJkg−1), the highest results were obtained from willow. Biomethane production during anaerobic digestion was the highest from common reed (108m3Mg−1 FM) and the lowest from Jerusalem artichoke (66m3Mg−1 FM). The methane concentration in biogas was rather low (50.9–54.9) comparing to other typical substrates for biogas production.