Constructed Wetland Treatment Research Articles

Designing appropriate site determination criteria for installing constructed wetland treatment system based on multi-criteria decision-making analyses

Constructed wetlands have recently started to be applied as the most important type of nature-based solution against the effects of climate change. This study investigates the determination of the most suitable site determination criteria for the application of this important nature-based solution tool by multiple decision-making methods. For this purpose, first of all, the literature was reviewed and the ten most important criteria for constructed wastelands were determined. Then, fieldwork was carried out according to these determined criteria, and a location was determined in the field according to each criterion. The global positioning system device is used to mark 10 locations that have been determined as waypoints for 10 criteria. The determined waypoints were then scored using the relevant criteria, and the best location was determined using the Multiple Attribute Utility Theory methods. Waypoint 1 received the highest score, 8.4, according to the results. Later, waypoint 7 received a score of 6.2, and waypoint 9 received a score of 5.7.

Hybrid constructed wetlands amended with zeolite/biochar for enhanced landfill leachate treatment

Landfill leachate contains high concentrations of ammonia and recalcitrant organic compounds, which can interfere with wastewater treatment processes. Hybrid constructed wetlands (CWs), consisting of Vertical Flow (VF) CWs followed by Horizontal Flow (HF) CWs, are low cost technologies for onsite leachate treatment. This study investigated the potential of low-cost adsorbent materials, a natural zeolite mineral (clinoptilolite) and biochar, to enhance leachate treatment in hybrid CWs. Two mesocosm hybrid CWs were set up at a Florida (US) landfill. In the Adsorbent-CW 10% (v/v) of zeolite was added to the VF-CW to enhance nitrification and 13% (v/v) biochar was added to the HF-CW to increase microbial activity and plant growth. A Control-CW contained only gravel. Both systems were planted with cattails (Typha latifolia) and cordgrass (Spartina alterniflora) and operated at varying hydraulic loading rates for ~2 years. A HF-CW containing wood chips (Woodchip-CW) was added downstream of the Adsorbent-CW during the final 6-months of operation to enhance denitrification. Results showed that zeolite addition to the VF-CW significantly increased nitrification rates by 16–93% due to cycles of ammonium adsorption and bioregeneration under intermittent loading conditions. Biochar addition increased removal of organic matter (21–26% to 29–44%) and color (1–18% to 7–49%), and improved wetland plant growth and nitrogen removal due to enhanced plant growth and rhizosphere microbial activity. Addition of the Woodchip-CW reduced nitrate accumulation, resulting in total nitrogen removals of up to 79%.

Stems of Phragmites australis are buffering methane and carbon dioxide emissions

Internal concentrations in the culm nodes of Phragmites australis and fluxes of methane (CH4) and carbon dioxide (CO2) were recorded in the treatment bed of constructed wetland (CW) with subsurface wastewater horizontal flow. Fluxes of CH4 and CO2 from the CW treatment bed were in ranges of 0 to 490 μmol m−2 h−1 and from 0 to 4499 μmol m−2 h−1 for CH4 and CO2, respectively. The highest CH4 soil fluxes were recorded in the unvegetated coarse gravel inflow zone of the CW treatment bed. The nearby inflow zone exhibited the highest CO2 fluxes. Internal culm node concentrations of CH4 and CO2 were related to oxygen (O2) stem concentrations and environmental conditions during diurnal courses. The concentrations of CH4 and CO2 gases were significantly correlated and opposing O2 concentrations. Culm node parameters and shoot density of P. australis influenced internal gas concentrations and the buffering of CH4 and CO2 emissions. The effect of buffering CH4 emissions is distinctive in the outflow zone of the treatment bed and is less important in the highly polluted inflow zone of the CW. Buffering of CH4 and partially also CO2 emissions by stems of P. australis is a process which affects the diurnal dynamics of CH4 and CO2 fluxes from common reed wetlands.

Microplastic biofilm, associated pathogen and antimicrobial resistance dynamics through a wastewater treatment process incorporating a constructed wetland

Microplastics in wastewater are colonized by biofilms containing pathogens and antimicrobial resistance (AMR) genes that can be exported into receiving water bodies. This study investigated establishment and changes in microplastic-associated biofilm and AMR during a conventional full-scale 2100 population equivalent wastewater treatment process combined with a free water surface polishing constructed wetland. Sequential microplastic colonization experiments were conducted at different stages of the wastewater treatment process, including in raw sewage, treated effluent and the constructed wetland. Two scenarios were tested in which the constructed wetland served as either (i) a polishing step or (ii) as primary recipient of sewage inoculated microplastics. Bacterial 16S rRNA gene sequencing was carried out for qualitative bacterial community analysis. qPCR was applied for quantitative analysis of AMR genes (sul1, ermB, tetW, intiI1), bacterial biomass (16S rRNA) and a human fecal marker (HF183). Microbial diversity on microplastics increased with incubation time. The initial sewage-derived biofilm composition changed more significantly in the wastewater effluent compared to the constructed wetland. Pathogen and AMR load decreased by up to two orders of magnitude after coupled conventional and constructed wetland treatment, while less impact was observed when sewage-inoculated microplastic material was directly transferred into the constructed wetland. Aeromonas, Klebsiella, and Streptococcus were key pathogenic genera correlated with AMR in microplastic-associated biofilms. Despite decreasing trends on human pathogens and AMR load along the treatment process, microplastic-associated biofilms were a considerable potential hotspot for AMR (intI1 gene) and accommodated Cyanobacteria and fish pathogens.

Genomic Characterization and Wetland Occurrence of a Novel Campylobacter Isolate from Canada Geese.

Populations of resident, non-migratory Canada geese are rapidly increasing. Canada geese are known to transmit viral and bacterial diseases, posing a possible threat to human health. The most prevalent pathogens vectored by geese are Campylobacter species, yet the current understanding of the identity and virulence of these pathogens is limited. In our previous study, we observed a high prevalence of Campylobacter spp. in the Banklick Creek wetland-a constructed treatment wetland (CTW) located in northern KY (USA) used to understand sources of fecal contamination originating from humans and waterfowl frequenting the area. To identify the types of Campylobacter spp. found contaminating the CTW, we performed genetic analyses of Campylobacter 16s ribosomal RNA amplified from CTW water samples and collected fecal material from birds frequenting those areas. Our results showed a high occurrence of a Campylobacter canadensis-like clade from the sampling sites. Whole-genome sequence analyses of an isolate from Canada goose fecal material, called MG1, were used to confirm the identity of the CTW isolates. Further, we examined the phylogenomic position, virulence gene content, and antimicrobial resistance gene profile of MG1. Lastly, we developed an MG1-specific real-time PCR assay and confirmed the presence of MG1 in Canada goose fecal samples surrounding the CTW. Our findings reveal that the Canada goose-vectored Campylobacter sp. MG1 is a novel isolate compared to C. canadensis that possesses possible zoonotic potential, which may be of human health concern.

Application of Constructed Wetland in Rural Sewage Treatment and Its Strengthening Technology

This paper starts from the current situation of rural sewage, analyzes the current common sewage treatment process at home and abroad and the existing mainstream sewage treatment process, compares and analyzes rural domestic sewage with urban domestic sewage, and proposes suitable treatment measures for the characteristics of rural domestic sewage - constructed wetland, because a single constructed wetland treatment measure will have problems such as low treatment efficiency and substandard effluent quality, so This paper presents its views on how to improve and optimize the constructed wetland using the existing reinforcement process, and improve the efficiency of the constructed wetland for rural sewage treatment by using some reinforcement measures. The article introduces and analyzes various existing reinforcement processes, compares the advantages and disadvantages of each reinforcement process, and especially discusses magnetic field reinforcement technology in detail, showing that magnetic field reinforcement technology has a certain role in sewage treatment, and compared with the traditional process without magnetic field reinforcement treatment, the reinforcement measures have significantly improved the treatment effect of sewage, and finally, the constructed wetland and reinforcement technology in rural Finally, the application of constructed wetland and intensification technology in rural sewage treatment is proposed.

Integrated Methods for Household Greywater Treatment: Modified Biofiltration and Phytoremediation.

Most countries around the world have experienced water scarcity in recent decades as fresh water consumption has increased. However, untreated wastewater is routinely discharged into the environment, particularly in developing countries, where it causes widespread environmental and public health problems. The majority of wastewater treatment method publications are heavily focused on high-income country applications and, in most cases, cannot be transferred to low and middle-income countries. An experimental study was conducted to evaluate the performance efficiency of pilot-scale physicochemical and biological treatment methods for the treatment of household greywater in Jimma, Ethiopia. During the experiment, grab samples of greywater were taken from the combined treatment system's influent and effluent every 7 days for 5 weeks and analyzed within 24-48 hours. Temperature, DO, EC, turbidity, TDS, and pH were measured on-site, while BOD, COD, TSS, TP, TN PO4 -3-P, NO3-N, NH4-N, Cl-, and FC were determined in the laboratory. During the five-week pilot-scale combined treatment system monitoring period, the combined experimental and control system's mean percentage reduction efficiencies were as follows: turbidity (97.2%, 92%), TSS (99.2%, 97.2%), BOD5 (94%, 57.4%), COD (91.6%, 54.7%), chloride (61%, 35%), TN (68.24, 42.7%), TP (71.6%, 38.7%), and FC (90%, 71.1%), respectively. Similarly, the combined experimental and control systems reduced PO4 -3-P (12.5 ± 3 mg/L), NO3-N (4.5 ± 3 mg/L), and NH4-N (10.19 ± 2.6 mg/L) to PO4 -3-P (3.5 ± 2.6 mg/L, 7.5 ± 1.6 mg/L), NO3-N (0.8 ± 0.5, 3.6 ± 2.3 mg/L), and NH4-N (7 ± 2.9 mg/L, 15.9 ± 3.9 mg/L), respectively. From the biofiltration and horizontal subsurface flow constructed wetland combined systems, the experimental combined technology emerged as the best performing greywater treatment system, exhibiting remarkably higher pollutant removal efficiencies. In conclusion, the combined biofiltration and horizontal subsurface flow constructed wetland treatment system can be the technology of choice in low-income countries, particularly those with tropical climates.

Effect of Loading Frequency on Ammonia-Nitrogen Removal Kinetics in Early-Stage Pilot-Scale Vertical Flow Constructed Wetlands Treating Landfill Leachate

This study measured the effects of loading frequency and plant species on the removal of ammonia-nitrogen (NH3-N) in a vertical flow constructed wetland (VFCW). Eight pilot-scale VFCW columns were constructed for this experiment; half of the columns were planted with Typha latifolia and the other half Scirpus californicus. To test the effect of loading frequency, half of the columns for each plant species were fed diluted leachate over the course of 24 h, and the other half were fed diluted leachate over the course of 8 h. This study was conducted in the early stages of plant and biofilm development within the system. Removal of chemical oxygen demand (COD) was observed but inconsistent, as was denitrification. Average NH3-N removal efficiencies in the various configurations ranged from 39.4 to 55.1%, and all configurations experienced peak removal efficiencies at a 1:20 dilution of leachate. Columns planted with T. latifolia and fed over 24 h performed significantly better than those planted with S. Californicus; this effect was not observed for columns fed over 8 h. Of the four configurations, columns planted with T. latifolia and fed over the course of 24 h performed best. The mechanisms responsible for this deserve further study.

Dyeing wastewater treatment in horizontal-vertical constructed wetland using organic waste media

A hybrid constructed wetland (CW) system with horizontal and vertical flow combination was evaluated for treating carbon-deficient synthetic dyeing wastewater containing 100 mg/L Reactive Yellow 145 dye. Organic waste products such as cow manure and wood chips were added as media in horizontal CW, and gravel as vertical CW media. Horizontal and vertical CWs were planted with Typha angustifolia. Horizontal CW was operated in continuous mode at hydraulic retention time (HRT) of 3 d and vertical CW in batch mode at 1 d HRT. The results suggested the potential application of a cost-effective horizontal-vertical hybrid CW to remove azo dyes from low-carbon dyeing wastewater. In horizontal CW, organic media was used as the carbon source for microbial dye degradation, resulting in 90% colour removal in the absence of available carbon in dyeing wastewater. Proteobacteria, Firmicutes and Bacteroidetes played a dominant role in dye degradation in horizontal CW. Vertical CW removed dye degradation organics, 69% ammonium-nitrogen and 39% organic-nitrogen. Phytotoxicity assays indicated toxicity reduction along the CW treatment path.

Research progress on antibiotic removal process in wastewater for aquatic environment protection

The serious issue of antibiotic contamination has become a pressing concern. Antibioticcontaminated wastewater that is not effectively treated can have detrimental effects on both aquatic environments and human health. Therefore, it is imperative to intensify research efforts towards developing efficient and effective processes for removing antibiotics from aquatic environments. This paper provides a comprehensive review of common antibiotic removal processes used in sewage treatment plants, including physical adsorption and membrane filtration. It also examines various chemical treatments such as ozone oxidation, hydrolysis, photolysis, Fenton oxidation, persulfate oxidation, and electrochemical oxidation. In addition, the paper discusses biological treatments including anaerobic biological treatment, aerobic biological treatment, and constructed wetland treatment, as well as the combination of related processes. Through this review of the relevant literature, it is evident that advanced oxidation technology demonstrates superior performance in single removal processes for antibiotics. Furthermore, the combination of different removal processes yields even more effective antibiotic removal outcomes, indicating great potential for future development. Finally, this paper highlights the importance of future research in antibiotic removal to further advance the field and promote the growth of antibiotic removal technology.

Domestic Wastewater Disinfection Planning for Constructed Wetland Treatment Effluent

Excessive water consumption to meet water needs has changed aquatic water quality and quantity. Focus on domestic wastewater treatment via built wetlands. Disinfection protects humans against disease-causing viruses, bacteria, and protozoan parasites in wastewater. This study planned the disinfection of artificial wetland wastewater to fulfill microbiological criteria. From the examined data, each unit's design criteria and disinfection effectiveness for the created wetland outlet in the WWTP unit will be discussed. The created wetland must process 8696 cfu/100mL of fecal coliform. Despite good processing efficiency, 94% of fecal coliforms do not fulfill quality criteria. WWTP's wetland emits 8.011 mg/L of Ammonia. 90% chlorine costs Rp. 35,000/kg on the market. Total disinfection costs are rough Rp. 1,018,210.73. Water quality, lamp output power, and exposure distance affect lamp intensity. The lamp's electric power controls the beam's intensity; the more power, the more emission. The emitted power isn't equal to the lamp's electric power. According to the state electricity provider, families with a 900VA power limit will pay Rp. 1,352/kWh in July-September 2021. Nine 30-W bulbs irradiate bacteria. The lights will run for 24 hours non-stop. Hence the monthly electricity usage is 194.4 kWh or Rp 262.829.00.

Tertiary Wastewater Treatment Processes Can Be a Double-Edged Sword for Water Quality Improvement in View of Mitigating Antimicrobial Resistance and Pathogenicity.

Despite the high removal efficiency for chemical pollutants by tertiary wastewater treatment processes (TWTPs), there is no definite conclusion in terms of microbial risk mitigation yet. This study utilized metagenomic approaches to reveal the alterations of antibiotic resistance genes (ARGs), virulence factor genes (VFGs), their co-occurrence, and potential hosts during multiple TWTPs. Results showed that the TWTPs reduced chemical pollutants in wastewater, but the denitrifying biofilter (DB) significantly increased the absolute abundances of selected antibiotic-resistant bacteria and ARGs, and simultaneously elevated the relative abundances of ARGs and VFGs through the enrichment of multidrug resistance and offensive genes, respectively. Moreover, the co-occurrence of ARGs and VFGs (e.g., bacA-tapW, mexF-adeG) was only identified after the DB treatment and all carried by Pseudomonas. Then, the ultraviolet and constructed wetland treatment showed good complementarity for microbial risk reduction through mitigating antibiotic resistance and pathogenicity. Network and binning analyses showed that the shift of key operational taxonomic units affiliating to Pseudomonas and Acinetobacter may contribute to the dynamic changes of ARGs and VFGs during the TWTPs. Overall, this study sheds new light on how the TWTPs affect the antibiotic resistome and VFG profiles and what TWTPs should be selected for microbial risk mitigation.

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.

Evaluation of constructed wetland systems toward naturalization of the elemental composition and microbial community in wastewater treatment plant effluent

Numerous studies have been conducted on the advanced treatment of wastewater treatment plant (WWTP) effluent by constructed wetlands (CWs); however, no studies have focused on the effect of the naturalization function of CWs on WWTP tailwater, i.e., reducing imbalances in the elemental composition and microbial community, compared with natural surface water (NSW). Therefore, the possible naturalization functions of CWs were evaluated by comparing the elemental composition, microbial structure and function in NSW with the influent and effluent of CW. Surveys were conducted in seventeen full-scale wetlands constructed to treat WWTP tailwater in eastern China, and the largest lake in the region, Taihu Lake, was selected as the reference for NSW. The imbalance index (IMI) was proposed to characterize the difference in the elemental proportions between tailwater and the references. The results showed that the IMI values for the WWTP effluent ranged from 0.51 to 0.10 and from 0.95 to 0.37 for macroelements and microelements, with average values of 0.30 and 0.62, respectively. When macronutrient IMI>0.27 or micronutrient IMI>0.43, the CWs alleviated the element imbalance; otherwise, the CWs increased the IMI and aggravated the imbalance. With the Hoagland formula as the reference, a similar result was obtained. CW treatment reduced the difference in bacterial composition between tailwater and NSW. According to FAPROTAX and BugBase function prediction, CW treatment reduced the difference in the relative abundance of microbial functions related to C, N, and S cycles, pathogenicity and antibiotic resistance genes between tailwater and NSW. The CW area and hydraulic retention time were significantly positively correlated with the naturalization index. Therefore, the CW system can naturalize tailwater in terms of both elemental composition and microbial composition and function, indicating the necessity of re-evaluating CW functions in treating WWTP tailwater.

The Potential of Constructed Wetland Systems and Photodegradation Processes for the Removal of Emerging Contaminants—A Review

The presence of emerging organic contaminants (EOCs) in the environment is increasing and requires the development of technologies for their effective removal. Therefore, a literature review on the behavior of EOCs during municipal wastewater treatment, both in major treatment systems and particularly in constructed wetlands (CWs), was carried out. The study also reviewed the behavior of EOCs in anaerobic digesters (ADs) and advanced oxidation processes, particularly in TiO2-based photocatalysis, which are being proposed as promising pre- and post-treatments for combination with CW. The following ten compounds were screened: acetaminophen (ACE), ofloxacin (OFL), caffeine (CAF), carbamazepine (CBZ), ketoprofen (KET), ibuprofen (IBU), diclofenac (DCL), clofibric acid (ACB), bisphenol A (BPA), and sotalol (SOT). The degradation pathways of the selected EOCs are largely influenced by their physicochemical and biochemical properties. Sorption and biodegradation are the main elimination mechanisms found in AD and CW treatment systems, where the combination of anaerobic and aerobic environments improves the elimination efficiency of EOCs. However, various contaminants appear recalcitrant. In this sense, in combination with CWs, TiO2-based photocatalysis emerges as a promising post-treatment for advanced EOC removal from wastewater.

Longitudinal Analysis of Sucralose at a Water Treatment Wetland

Sales of low-calorie sweeteners are increasing in the Unites States, with sucralose representing the second largest of the U.S. market share. Since >99% of ingested sucralose is excreted as the parent compound, it represents a contaminant of emerging concern and has been proposed as an indicator of pollution of natural waters by anthropogenic waste. Many report that it is increasingly omnipresent in surface, coastal, and drinking water. Given the increasing consumption of low-calorie sweeteners, changes in influent and effluent sucralose concentrations presage their concentrations in natural waters. The aim of this research was to quantify sucralose at a constructed treatment wetland that was designed to remove nutrients (nitrogen and phosphorus) from secondary treated wastewater. We report the concentrations of sucralose in the surface water, sediment, and porewater throughout the flow train of the wetlands over a period of three years and include surface water sampling following an extreme weather event. The average influent surface water concentration of sucralose was 24 ± 2 ppb, and the average outfall concentration was 20 ± 6 ppb, indicating the sucralose is not subjected to chemical or physical adsorption in the sediment within the wetland.

What Is the Suitable Sampling Frequency for Water Quality Monitoring in Full-Scale Constructed Wetlands Treating Tail Water?

Three years of hourly COD and NH4+-N measurements for two full-scale integrated constructed wetlands (CWs) treating secondary effluents from sewage treatment plants (STPs) were used to quantify the proper sampling frequency (SF). The modified coefficient of variation (CVm) and average variation rate (VRa) were calculated to monitor the dynamics and annual average performance, respectively. It was found that (1) under CVm 5%, VRa 5%, and VRm 5%, the sampling intervals (SI) of COD can be set as 1.19 h, 526.5 h, and 110.1 h, respectively, and the SI of NH4+-N should be 4.51 h, 66.3 h, and 26.8 h, respectively; (2) under CVm 10%, VRa 10%, and VRm 10%, the monitoring intervals of COD can be set as 11.92 h, 1401.7 h, and 233.5 h, respectively, and the monitoring intervals of NH4+-N should be 30.73 h, 139.3 h, and 50.5 h, respectively. Therefore, to meet the need of monitoring the dynamic changes in data, hourly and 4 h SIs were recommended for COD and NH4+-N evaluation, respectively, when it is necessary to consider the operation and maintenance costs at the same time, 11 h and 30 h SIs were proper for COD and NH4+-N evaluation, respectively. The methods proposed in this study could provide reference to improve the management and evaluation level of full-scale CWs.

Evaluation of Physicochemical and Microbiological Parameters of Wastewater Submitted to Constructed Wetland Treatment System

The use of natural systems such as wetlands constructed in the treatment of wastewater has become increasingly important due the ability of these systems to remove large amounts of macronutrients and microorganisms and to promote the degradation of organic matter. Given this background, the main objective of this study was to evaluate the efficiency of an experimental constructed wetland horizontal flow system subsurface cultivated with Zantedeschia aethiopica filled with sand and gravel substrates. The parameters were evaluated by the characterization of physicochemical and microbiological indicators of wastewater from the septic tank of the State University of Goiás in Anápolis city, Goiás, Brazil. The reductions of macronutrients ranged from 57.9 to 94.7%, and 87.0 to 91.0% for organic matter. In addition, a significant reduction in coliform levels in wastewater was observed after wetland treatment. It was concluded that the constructed wetland system could be proposed to treat wastewater from septic tanks at both secondary and tertiary levels, due to its high percentage efficiency in the removal of organic matter and macronutrients. The results obtained demonstrated the applicability of the studied system to be used as a versatile, sustainable, and economical treatment of effluents complementary to the septic tank treatment system.

Removal of organochlorine pesticides and metagenomic analysis by multi-stage constructed wetland treating landfill leachate.

Constructed wetlands (CWs) can effectively treat landfill leachate (LL). However, there is limited research on the removal of organochlorine pesticides (OCPs) refractory organics during LL treatment in CWs. In this study, multi-stage subsurface flow CWs was used to treat LL, and the removal fate of hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) in CWs was investigated. The structural differences between plant roots and substrate microbial communities were compared and the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway of organic matter was analyzed based on metagenomic analysis. The results showed that substrate adsorption (50.55%-72.74%) and microbial degradation (20.38%-27.89%) were the main ways to remove OCPs. The Proteobacteria occupied a dominant position in the CWs system, among which Betaproteobacteria (34.37%-35.90%) were contained in the substrate, and Alphaproteobacteria (21.19%-23.84%) was a more dominant microorganism in plant roots. Formaldehyde assimilation and serine pathway were the main pathways of methane metabolism. This study provides a reference for the removal mechanism of OCPs to promote the application of CWs technology in LL treatment.

Photochemical behavior of constructed wetlands-derived dissolved organic matter and its effects on Bisphenol A photodegradation in secondary treated wastewater

Free water surface flow (FWS) constructed wetlands (CWs) have been broadly applied for polishing secondary treated effluents. Dissolved organic matter derived from FWS CWs (WDOM) plays key roles in contaminants transformations. Conversely, photodegradation could shape the quantity and quality of WDOM, thereby affecting its roles in the photolysis of organic micropollutants (OMPs). Nevertheless, whether and how solar irradiation-induced photodegradation modify the properties of WDOM, and the effects of WDOM on the photodegradation of OMPs remain unclear. This study elucidates the photochemical behavior of two WDOM isolated from field-scale FWS CWs for effluent polishing under simulated sunlight irradiation using spectroscopic tools and high-resolution mass spectra. Furthermore, the roles of WDOM in the photodegradation of Bisphenol A (BPA), as a representative endocrine-disrupting compound (EDC), were comprehensively investigated. Solar irradiation was demonstrated to lower the molecular weight and aromaticity of WDOM, as well as weaken its light absorption. Ultrahigh-resolution mass spectra further confirmed that aromatic and unsaturated structures were susceptible to solar irradiation-induced photodegradation reactions. Subsequently, less aromatic and more saturated structures eventually formed under sunlight irradiation, consistent with the result from spectroscopic characterization. The reactive species produced from WDOM significantly enhanced the photodegradation of BPA with the kobs noticeably increasing 4-fold compared with the kobs for direct photolysis. Additionally, 3WDOM* was identified as the dominant reactive species leading to the photolysis of BPA in the presence of WDOM. These findings improve understanding of the phototransformation behavior of WDOM under sunlight irradiation and the roles that WDOM plays in the photochemical fate of coexisting OMPs in CWs treatment systems.