Constructed Wetland System Research Articles

Effects of Hematite and Biochar Addition on Wastewater Treatment Efficiency, Greenhouse Gas Emission, and Microbial Community in Subsurface Flow Constructed Wetland

The type and structure of the substrate in constructed wetland affects the diversity and abundance of microorganisms, thereby influencing the effect of sewage treatment. In this study, four groups of wetlands were constructed in the greenhouse:blank-constructed wetland (CW0), hematite-constructed wetland (CW1), biochar-constructed wetland (CW2), and hematite+biochar-constructed wetland (CW3), to study the differences in sewage treatment effects, greenhouse gas emissions, and microbial community structures of constructed wetland systems under different filler substrates. The results showed that the addition of hematite or biochar increased the COD removal rate of -0.12% to 1.7%. The addition of biochar increased the removal rate of NH4+-N by 22.48% and NO3--N by 6.82% and reduced the emission flux of CH4 by 83.91% and N2O by 30.81%. The addition of hematite reduced the removal rate of NH4+-N by 1.12%, increased the removal rate of NO3--N by 3.98%, and reduced the emission flux of CH4 by 33.29% and N2O by 25.2%. Adding biochar or hematite increased the relative abundances of Actinobacteria and Proteobacteria, which was beneficial to the removal of COD. The Ace, Chao, Sobs, and Shannon indexes in the substrate treated with biochar were the largest, and the Simpson index was the smallest. The treatment with hematite was the opposite, indicating that the richness and diversity of microbial communities in the treatment system with biochar was the largest. Adding hematite reduced the richness and diversity of the microbial community in the constructed wetland system. Adding biochar or hematite increased the relative abundances of Dechloromonas, Thaurea, Saccharimonadales, and other denitrifying bacteria, which was beneficial to wetland denitrification. The addition of biochar increased the abundances of nosZ, nirS, and nirK functional genes, which were conducive to the occurrence of denitrification. The addition of biochar increased the abundances of pmoA functional genes, reduced the abundance of mcrA functional genes, and inhibited the production of CH4. It also increased the abundance of methanotrophic bacteria and promoted the occurrence of the CH4 oxidation process. Although the addition of hematite increased the abundance of mcrA functional genes, Fe3+ competed with methanogens for electron donors and inhibited the production of CH4.

Swine Wastewater Treatment in Constructed Wetland Systems: Hydraulic and Kinetic Modeling

The use of constructed wetland systems (CWS) is presented as an alternative for the treatment of effluents since these have reduced implementation costs and relative ease of operation. The present research was undertaken to evaluate to study the hydrodynamic and the fitting of first-order mathematical kinetic models for the removal of pollutants in CWS. Three CWS were built, using expanded clay as filter support: one cultivated with Polygonum punctatum (CWSw), another cultivated with Chrysopogon zizanioides (CWSV), and a control unit (CWSc). The actual retention time was 3.12 days in the CWSc, whereas, in the CWSw and CWSv, we observed values of 4.14 and 4.11 days, respectively. The dispersion values were high in all CWS. The values of chemical oxygen demand (COD) across the length of the CWS were used to fit the kinetic models that describe the first-order decay of organic matter over the CWS. The models that showed a better fit to the experimental data were the plug-flow with residual concentration, the continuous stirred tank reactor, and Shepherd’s models.

The Partial Contribution of Constructed Wetland Components (Roots, Gravel, Microorganisms) in the Removal of Phenols: A Mini Review

Constructed wetlands (CW) have attracted growing interest in wastewater treatment research in the last 20 years, and have been investigated intensively worldwide. Many of the basic processes occurring in CWs have been qualitatively established; however, much quantitative knowledge is still lacking. In this mini review, the proportionate contributions of the different system components to removal of contaminants are examined. The main objective of this mini review is to provide a more in-depth assessment of the interactions between the porous bed, plants, and microorganisms during the removal of organic contaminants from the water in a subsurface flow CW system. In addition, a unique technique to study the partial contribution to the total removal of contaminants in a CW is described. Future studies in this field will expand our knowledge of any synergistic or antagonistic interactions between the components and facilitate improved CW construction and operation. Here, phenol will be used as a model industrial organic contaminant to illustrate our current understanding of the contributions of the different components to total removal. I will also discuss the various factors influencing the efficacy of bacteria, whether planktonic or as biofilm (on porous bed or plant roots), in subsurface flow CWs.

In-depth performance study of an innovative decentralized multistage constructed wetland system treating real institutional wastewater

The performance of an innovative decentralized multistage constructed wetland (DMCW) treating institutional wastewater is studied covering three seasons. The DMCW system with Canna lily efficiently removed organics contaminants like COD and BOD, and nutrients from the wastewater, showing its dependency on meteorological factors. Overall the performance is maximum in summer and least in monsoon, with a COD removal of 85.6% in summer followed by 82.5% in winter and 61.2% in monsoon. Removal of TSS (67.7–85.5%), PO43--P (52.1–64.4%), NH4+-N (56.6–71.6%), NO3−-N (47.3–63.4%) and NO2−-N (62–75.4%) were achieved along with heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Hg and Pb. Removal of pathogens like Vibrio is >98%, E. coli 95%, Pseudomonas 99%, and Aeromonas 63% was observed. Mass removal rate of COD was maximum in summer (97.3 g/m2/d) followed by winter (78.7 g/m2/d) and monsoon (43.5 g/m2/d). Majority of organics removal during the treatment was highlighted through Gas Chromatography-Mass Spectrometry (GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed wastewater to be complex. The Canna lily accumulated various elements and oxides during the treatment with no stress on its health. The treated water quality is within the permissible limits and stands suitable for irrigational purposes. Better plant health and increased microbial diversity in the garden proves the suitability of treated water for irrigational activities. The results were validated using statistical tools like Mann-Whitney U test and principal component analysis.

Emerged macrophytes to the rescue: Perfluoroalkyl acid removal from wastewater and spiked solutions

This study evaluated the potential for three emergent aquatic macrophytes to remove perfluoroalkyl acids (PFAAs) from contaminated waters in constructed wetland systems. Three plants (Iris pseudacorus L., Phragmites australis (Cav.) Trin. Ex Steud., and Typha latifolia L.) were exposed to an effluent from a tannery wastewater treatment plant (WWTP) that contained residual PFAAs, and to three spiked solutions with increasing concentrations of 11 perfluorocarboxylic acids (PFCAs) and three perfluorosulfonic acids (PFSAs) (500, 2500, and 5000 ng L−1, each). Thirty-six lightweight expanded clay aggregate- and vegetation-filled tanks (0.35 × 0.56 × 0.31 m) were exposed to the tested solutions at the Acque del Chiampo SpA WWTP in Arzignano (NE Italy). Throughout the experiment, PFAA concentrations and physicochemical water parameters were monitored via measures of the clay material, plastic tank inner surfaces, and below- and above-ground biomasses (after harvest). Vegetation growth was shown to be unaffected by increased PFAA levels in the spiked solutions. Alternatively, total biomass was significantly reduced when WWTP water was used, although we attribute this finding to the relatively high salinity that mainly restricted Typha and Iris development. The tested macrophytes were found to remove a significant PFAA mass from the contaminated waters (36% to ca. 80%, on average) when Phragmites was subjected to the highest PFAA concentrations. Such large accumulations were primarily associated with long C-chain PFAA stabilization in belowground biomass (26%, on average). Most PFAA translocations were observed in Typha, which accumulated mostly short perfluorinated C-chain PFBA, PFPeA, and PFHxA in the aboveground biomass (16%, on average). Despite some growth limitations, Iris was still the most efficient macrophyte for translocating PFBS under WWTP.

Reuse of wastewater, treated by phytoremediation, for the irrigation of the Botanical Garden ‘‘le jardin Landon’’ (Biskra, Algeria). Sustainable solution for the preservation of a material heritage site

The green spaces of the city of Biskra (Algeria) resist the arid climate of the summer season and therefore suffer from water scarcity caused mainly by evaporation and transpiration of the plants. To remedy this problem, the study suggests to reuse the sewage for irrigation after being purified, using constructed wetlands with improved capacity by phytoremediation. As an example of a sustainable solution, it is proposed to apply this technique to the botanical garden of the city of Biskra (Algeria), «le jardin Landon». The design of a Constructed Wetland system is proposed. The Landon Garden was created in 1870 by Count Landon of Longueville, decorated with a variety of flora from the tropics and the Equatorial countries. It is currently considered as national material heritage.

Cold temperature mediated nitrate removal pathways in electrolysis-assisted constructed wetland systems under different influent C/N ratios and anode materials

Electrolysis had proven to be useful for the enhanced performance in constructed wetlands (CWs). While at cold temperature, the nitrate removal pathways, plant physiological characteristics and microbial community structure in electrolysis-assisted CWs were unclear. Therefore, the purification performance of three electrolysis-assisted horizontal subsurface-flow constructed wetlands (E-HSCWs) with different anodes and a control system in cold seasons were evaluated in this study. E-HSCWs showed a 2.02–83.21% increase of total nitrogen (TN) removal when compared to control, and the gaps were enlarged with increasing C/N (chemical oxygen demand/total nitrogen, COD/TN) ratios. Nitrite accumulation in E-HSCWs presented a first increase then went down trend with increasing C/N ratios, compared to a steady increase in control system. The optimum C/N ratio was 8 in E-HSCWs for both TN and COD removal. Moreover, Ti|IrO2–Ta2O5 (Ti) anode showed the highest potential for TN and COD removal. Less root weight, shorter root length and reduced TN and total phosphorus (TP) contents in roots were observed in wetland plants (Iris sibirica) of E-HSCWs. In E-HSCWs with Fe and C anodes, the nitrate removal was mainly accomplished by autotrophic denitrifier Hydrogenophaga. While in E-HSCWs with Ti anode, the synergistic effect of autotrophic denitrifier Hydrogenophaga and heterotrophic denitrifiers Acidovorax, Simplicispira, Zoogloea accounted for the nitrate removal. These results showed that E-HSCWs at proper C/N ratio of 8 would be promising for nitrate removal at cold temperature.

The suitable biomass carbon source for improving nitrogen removal in surface flow constructed wetland system: Fresh vs. withered

Plant biomass can be used as a carbon source to enhance the nitrogen removal effect. Related researches mainly focused on withered biomass, while little on fresh biomass. In this study, batch experiments revealed that the carbon release rate (60.5mg TOC g-1) of fresh biomass was significantly higher than that of withered biomass (44.9mg TOC g-1), while the nitrogen release rate showed the opposite trend. Compared with withered biomass, fresh biomass could release more sugar and less refractory humic acid, which means higher bioavailability. After adding fresh biomass, TN removal rate increased from 18.65% to 51.59%. The TN removal in the wetland adding withered biomass increased from 13.59% to 42.25%. The biomass addition had a slight impact on the effluent sensory quality in the first two days. After adding fresh biomass and withered biomass, the relative abundance of denitrifying bacteria like Flavobacterium and Pseudomonas in the system significantly increased. In general, fresh biomass was more suitable as a denitrification carbon source for surface flow constructed wetlands.

Comparative performance of Scirpus grossus for phytotreating mixed dye wastewater in batch and continuous pilot subsurface constructed wetland systems

Dye is one of the pollutants found in water bodies because of the increased growth of the textile industry. In this study, Scirpus grossus was planted inside a constructed wetland to treat mixed dye (methylene blue and methyl orange)-containing wastewater under batch and continuous modes. The plants were exposed to various concentrations (0, 50, 75, and 100 mg/L) of mixed dye for 72 days (with hydraulic retention time of 7 days for the continuous system). Biological oxygen demand, chemical oxygen demand, total organic carbon, pH, temperature, ionic content, and plant growth parameters were measured. Results showed that S. grossus can withstand all the tested dye concentrations until the end of the treatment period. Color removal efficiencies of 86, 84, and 75% were obtained in batch mode, whereas 90%, 85%, and 79% were obtained in continuous mode for 50, 75, and 100 mg/L dye concentrations, respectively. Fourier-transform infrared analysis confirmed the transformation of dye compounds after treatment and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis showed that most of the intermediate compounds were not absorbed into plants but adsorbed onto the surface of the root structure.

THE PROGRESS IN USING GREYWATER AS A SOLUTION TO WATER SCARCITY IN A DEVELOPING COUNTRY

Increased production of greywater prompted by the rise of urbanization and increased population in the industrial era is a growing environmental concern exacerbating the apparent water insecurity. Treatment and reuse of greywater is a promising solution to this problem since it will divert the use of limited freshwater resources to unavoidable consumptive uses. This study reviewed the various methods used to treat greywater and the progress made in taking up the practice in Kenya. Findings showed a variety of physicochemical treatment methods such as filtration, adsorption, coagulation and photocatalytic oxidation used to decontaminate greywater. Biological approaches such as the use of reactors and constructed wetland systems were discussed. Case study applications of the treatment approaches in Kenya to manage greywater were also highlighted. However, it was noted that appropriate policies, adequate funding and better designing of greywater treatment systems should be adopted to support the enhanced practices in Kenya.

Treatment Performance Assessment of Natural and Constructed Wetlands on Wastewater From Kege Wet Coffee Processing Plant in Dale Woreda, Sidama Regional State, Ethiopia.

Constructed wetlands are engineered systems built to use natural processes and remove pollutants from contaminated water in a more controlled environment. The research was an experimental research carried out to assess the effectiveness of natural and constructed wetland systems in the treatment of coffee wastewater. The 2 vertical flow constructed wetland was built. The first wetland covered an area of 132 m2. It has 12 m width and 11 m length. Open space is constructed between 2 constructed wetlands with a dimension of 11 m × 3 m × 1 m. The second wetland was constructed and its function is similar to the first one, from this wetland water is discharged to the river. The construction of the wetland is accomplished by constructing 20 cm wide furrows with a spacing of 30 cm. Vetiver grasses have planted with a spacing of 20 cm intervals. The physicochemical data were recorded, organized, and analyzed using R software (version 4.1) and Microsoft Excel. Data were processed using parametric (one-way ANOVA) and nonparametric (Mann-Whitney's U test) statistical tests of homogeneity. One-way analysis of Variance (ANOVA) was used to determine the significance of differences in variations in physicochemical variables within the constructed wetland sites. Tukey's multiple comparisons for differences between means were also assessed. Findings indicated that a natural wetland had a mean influent and effluent of total suspended solids (TSS) of 2190.78 ± 448.46 mg/l and 972.67 ± 234.312 mg/l, respectively. A Mann-Whitney U test revealed that TSS were significantly higher in natural wetland (median = 1551.50) compared to constructed wetland (median = 922.5), U = 676.5, z = -2.435, P = .015, r = .257. Natural wetlands had a mean influent of biological oxygen demand (BOD) was 4277.94 ± 157.02 mg/l, while in the effluent of BOD it was 326.83 ± 112.24 mg/l. While in constructed wetland it was 4192.4 ± 191.3 mg/l, 782.72 ± 507.6 mg/l, and 88.28 ± 20.08 mg/l in influent, middle, and effluent respectively. Average chemical oxygen demand (COD) value at influent in natural wetlands was 8085.61 ± 536.99 mg/l and in the effluent it was 675.33 ± 201.4 mg/l. In constructed wetland, it was found to be 8409.8 ± 592.9, 1372.6 ± 387.94, and 249.0 ± 7.68 for influent, middle, and effluent respectively. Comparatively, the purification efficiency of organic pollutants (TSS, BOD, and COD) of constructed wetlands was better than natural wetlands, whereas natural wetlands had better purification efficiency of nitrogen compounds such as ammonium, nitrite, and nitrate. On average, removal rates for nitrogen compounds were 39.53% and -24.41% for ammonium, 79.44% and 55.4% for nitrite, and 68.90% and 60.6% for nitrate in natural and constructed wetlands respectively, while the phosphate removal rate was 43.17% and 58.7% in natural and constructed wetlands, respectively. A Mann-Whitney U test revealed that there is no significance difference in nitrite, nitrate, ammonium, and phosphate concentration between natural and constructed wetlands(P > .05). Based on these results, both systems of treatment were effective in treating the coffee effluent since most of the values obtained were below the permissible EEPA limits. Even though the constructed wetland treatment plant performed better overall, in comparison, the natural wetlands had better purification efficiency for nitrogen compounds like ammonium, nitrite, and nitrate and the constructed wetlands had better purification efficiency for organic pollutants (TSS, BOD, and COD).

The nitrogen removal performance and microbial communities in a pilot multistage trickling constructed wetland for purifying polluted groundwater

The co-existence of phototrophic organisms, nitrifiers, and denitrifiers contributed to N removal in a multi-stage trickling constructed wetland system for the treatment of contaminated groundwater without adding organic carbon.

Adsorption performances of corn cob-derived biochar in saturated and semi-saturated vertical-flow constructed wetlands for nutrient removal under erratic oxygen supply

In this study, corn cob biochar-established Vertical-Flow Constructed Wetland (saturated and semi-saturated systems) with varying oxygen supplying blueprints were initiated to purge methane-fermented wastewater from a piggery farm. Adsorption capacity results of Iodine (2.439 ± 0.120 mmol Iodine g−1) and methylene blue (5.86*10−7 ± 1.631*10−8 mmol MB g−1) revealed the presents of enough adsorption from the aqueous solution and large surface area estimations by the Iodine (307.9 m2 g−1) and Brunauer–Emmett–Teller-BET (263.0 m2 g−1) measurements synchronously. The Bayesian statistical analysis approach was used to analyze the experimental data and the Langmuir model well described the adsorption data than the Freundlich model. The results exhibited the capability of corn cob biochar in removing nutrients from swine wastewater as prescribed shown by the adsorption mechanisms (Iodine and Methylene Blue (MB)) and Scanning Electron Microscope (SEM) images with a biofilm attached to the corn cob biomass. Both constructed wetland systems inferred their aptitude to reducing the concentration strengths of Chemical Oxygen Demand (COD), NH4+-N, and PO43− with higher removal efficiencies. The SEM images taken before and after the constructed wetland execution revealed that the biochar's surface had the attached biofilm of microbial communities that were present during the wetland's operation. The use of biochar in constructed wetlands with intermittent oxygen supply provides a better treatment of wastewater in rural areas of developing countries as a sustainable pollution control strategy.

Optimization of Acetaminophen and Methylparaben Removal within Subsurface Batch Constructed Wetland Systems

Optimization of Acetaminophen and Methylparaben Removal within Subsurface Batch Constructed Wetland Systems

Enhanced fodder production using treated wastewater from a pilot constructed wetland system

Enhanced fodder production using treated wastewater from a pilot constructed wetland system

Development and performance assessment of a castor-based vertical flow constructed wetland system for utilization of landfill leachate

Development and performance assessment of a castor-based vertical flow constructed wetland system for utilization of landfill leachate

Efficiency Evaluation of Domestic Wastewater Treatment by Three Macrophytes Using Pilot Constructed Wetland System in Covenant University, Ota, Nigeria

Efficiency Evaluation of Domestic Wastewater Treatment by Three Macrophytes Using Pilot Constructed Wetland System in Covenant University, Ota, Nigeria

Potential Use of Constructed Wetland Systems for Rural Sanitation and Wastewater Reuse in Agriculture in the Moroccan Context

Located in a semi-arid to arid region, Morocco is confronting increasing water scarcity challenges. In the circular economy paradigm, the reuse of treated wastewater in agriculture is currently considered a possible solution to mitigate water shortage and pollution problems. In recent years, Morocco has made significative progress in urban wastewater treatment under the National Wastewater Program (PNA). However, rural sanitation has undergone significant delays. Therefore, an alternative technology for wastewater treatment and reuse in rural areas is investigated in this review, considering the region’s economic, social, and regulatory characteristics. Constructed wetlands (CWs) are a simple, sustainable, and cost-effective technology that has yet to be fully explored in Morocco. CWs, indeed, appear to be suitable for the treatment and reuse of wastewater in remote rural areas if they can produce effluent that meets the standards of agricultural irrigation. In this review, 29 studies covering 16 countries and different types of wastewater were collected and studied to assess the treatment efficiency of different types of CWs under different design and operational parameters, as well as their potential application in agricultural reuse. The results demonstrated that the removal efficiency of conventional contamination such as organic matter and suspended solids is generally high. CWs also demonstrated a remarkable capacity to remove heavy metals and emerging contaminants such as pharmaceuticals, care products, etc. The removal of microbial contamination, on the other hand, is challenging, and does not satisfy the standards all the time. However, it can be improved using hybrid constructed wetlands or by adding polishing treatment. In addition, several studies reported that CWs managed to produce effluent that met the requirements of wastewater reuse in agriculture of different countries or organisations including Morocco.

Microbial community development in tropical constructed wetland soils in Taiwan

Constructed wetlands are widely used around the world as a low-cost wastewater treatment system that simultaneously provides various ecosystem services. Microorganisms in wetland soils serve as fundamental producers and decomposers that support wetland functions. However, few studies have documented the compositions of soil microorganisms in constructed wetland systems and even fewer have evaluated how soil microorganisms change after a wetland is constructed. In this study, soil samples were collected from four constructed wetlands of different ages and analyzed with a phospholipid fatty acid (PLFA) method to show how soil microbial communities change overtime. The results were that both the bacterial and fungal abundances increased with wetland age, and bacteria comprised about 90% of the soil microbial communities in all ages of constructed wetlands. Although the compositions of microbial communities remained similar among the wetlands, the stress indices showed that microbial stress may be affected by changes in the availability of in situ nutrients, e.g. ammonium, nitrate, soluble organic nitrogen and total dissolved nitrogen.

Performance of constructed wetland system using different species of macrophytes in the treatment of domestic sewage treatment

The objective is to assess the initial performance of a constructed wetland system and the development of the macrophyte species cattail(Typha spp.) (CWt), piripiri (Cyperus giganteus) (CWp), and white garland lily (Hedychium coronarium Koehne) (CWl) and an suncultivated (UNc) on the treatment of sewage from toilets and from a restaurant. Changes in hydrogen potential, electrical conductivity, total suspended solids, total solids, biochemical oxygen demand, chemical oxygen demand, turbidity, nitrate, ammonium nitrogen, total phosphate, hydraulic retention time (HRT), and potential evapotranspiration (PET) and the development and adaptation of macrophytes were measured. The surface area of ??each constructed wetland (CW) had a surface area of 16.25 m2 and average volume treated of 0.40 m3 d-1, with continuous variable horizontal subsurface flow equally fed with sewage previously treated in three septic tanks in series, with an individual useful volume of 5.100 L. The PET in CWt, CWp and CWl was higher than that of UNc. The highest pH values were obtained in the effluent of CWp, CWt, and CWl. The use of macrophytes did not influence the EC, TS, BOD5,20, COD, and nitrate were lower and ammonium nitrogen and total phosphate were higher in the effluent of CWs and UNc in relation to the influent. The efficiency indexes that showed a very strong Pearson correlations (> 90%) were pH correlated with N-NH4+, turbidity correlated with COD, TS correlated with EC, and BOD5,20 and COD correlated with NO3-.Piripiri and cattails showed the best development of plants in the second half of CW.