Removal, transformation and ecological risk assessment of pesticide in rural wastewater by field-scale horizontal flow constructed wetlands of treated effluent.

Constructed wetlands (CWs) are widely used in sewage treatment in rural areas, but there are only a few studies on field-scale CWs in treating wastewater-borne pesticides. In this study, the treatment and metabolic transformation of 29 pesticides in rural domestic sewage by 10 field-scale horizontal flow CWs (HF-CWs), each with a treatment scale of 36‒5000 m3/d and operated for 2‒10 years, in Guangzhou, Southern China was investigated. The risk of pesticides in treated effluent and main factors influencing such risk were evaluated. Results demonstrated that HF-CWs could remove pesticides in sewage and reduce their ecological risk in effluent, but the degree varied among types of pesticides. Herbicides had the highest mean removal rate (67.35 %) followed by insecticides (60.13 %), and the least was fungicides (53.22 %). In terms of single pesticide compounds, the mean removal rate of butachlor was the highest (73.32 %), then acetochlor (69.41 %), atrazine (68.28 %), metolachlor (58.40 %), and oxadixyl (53.28 %). The overall removal rates of targeted pesticides in each HF-CWs ranged from 11 %‒57 %, excluding two HF-CWs showing increases in pesticides in treated effluent. Residues of malathion, phorate, and endosulfan in effluent had high-risks (RQ > 5). The pesticide concentration in effluent was mainly affected by that in influent (P = 0.042), and source control was the key to reducing risk. The main metabolic pathways of pesticide in HF-CWs were oxidation, with hydroxyl group to carbonyl group or to form sulfones, the second pathways by hydrolysis, aerobic condition was conducive to the transformation of pesticides. Sulfones were generally more toxic than the metabolites produced by hydrolytic pathways. The present study provides a reference on pesticides for the purification performance improvement, long-term maintenance, and practical sustainable application of field-scale HF-CWs.

Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system.

The presence of per- and polyfluoroalkyl substances (PFASs) in water environments has been linked to a slew of negative health effects in both animals and humans, but the green and eco-sustainable removal technologies remain largely unknown. Constructed wetland coupled microbial fuel cell (CW-MFC) is termed a "green process" to control pollutants and recover energy. However, so far, no study has investigated the removal of PFASs and their effects on the performance of the CW-MFC systems. Here, we investigated the removal performance of PFOA and PFOS in the CW-MFC systems both in the absence and presence of electricity circuit, and explored the distribution and fate of PFASs and their interactions with other elements in the systems. Our findings demonstrated excellent removal efficiency of >96% PFOA and PFOS in CW-MFC systems. PFOA and PFOS were distributed throughout the system via wastewater flow, while electrode material and plants are the main enrichment sites in which MFC enhanced up to 10% PFASs removal. However, a loss of 7.2-13.5% of nitrogen removal and a decrease of 7.3% in bioelectricity output were observed when PFASs were introduced in the system. The driven force led to the loss of nitrogen removal and bioelectricity generation lies in the accumulation of PFASs in system composition, which affected microbial activity and community composition, damaging the health of the plant, and in turn reducing CW-MFC's functioning. No doubt, CW-MFC systems provide an alternative technique for PFASs removal, alleviating some limitations to the physical and chemical techniques, but further investigation is highly needed.

Initial ecological restoration assessment of an urban river in the subtropical region in China.

Rivers in urbanised cities are often polluted, black, and odorous, with poor water quality and deteriorated ecology. Despite many river restoration studies, assessments of ecological responses to river restoration practices remain scant. Benthic animals are useful biological indicators showing the change and succession of river ecosystems; however, previous studies have mainly focussed on a few target species without considering overall ecosystem integrity. Here, we used a multi-index biological assessment method, benthic index of biological integrity (B-IBI) to assess ecological responses to river restoration of the Shahe River in subtropical region of China. Spatiotemporal changes in the macrobenthos community structure after restoration were monitored to explore species succession. We found that the number of macrobenthos species increased from 16 to 42, with the emergence of some pollution-sensitive species during the restoration period. Molluscs showed widespread recovery, and their relative proportions almost doubled from 12.5% to 24.4%. Oligochaetes and chironomids were the pioneer species in the recovering communities, while gastropod molluscs and pollution-sensitive aquatic insects were transitional species that first settled during the initial recovery period. Based on our survey data, 25 candidate metrics were selected, and five core metrics (total taxa, Simpson diversity index, percentage of crustaceans and molluscs, percentage of predators, and percentage of collector-gatherers) were identified after screening to establish the B-IBI. Our analysis revealed a distinct improvement in the overall health of the river, with the proportions of "excellent" and "good" sites increasing from zero to 28.6% and from 14.3% to 42.9%, respectively. A correlation analysis indicated that water flow, molluscs, and total phosphorus content were the three drivers of ecological recovery in the Shahe River. Overall, our study demonstrates the importance of governance and restoration of rivers in tropical and subtropical cities, and provides valuable evidence that can guide the design and evaluation of river restoration works.

The combination sequence effect on nitrogen removal pathway in hybrid constructed wetlands treating raw sewage from multiple perspectives.

The combination sequence of traditional hybrid constructed wetlands (HCWs) affects the removal of nitrogen in raw sewage, but the effect of the combination sequence on nitrogen removal pathway have seldom been reported, especially the specific conditions allowing anammox to occur. Three-stage HCWs, namely vertical flow (VF), horizontal flow (HF) and surface flow (SF) constructed wetlands, were arranged in six different sequences to investigate nitrogen removal efficiencies and microbial removal pathways using metagenomic and stable isotope analyses. Results showed that the combination sequence significantly affected nitrogen removal pathways in HCWs. We found the best removal of total nitrogen (~50%) and ammonium (NH4+-N, ~99%) in HCWs with a VFCW in the 1st stage. Metagenomic results and stable isotope analyses further indicated that simultaneous nitrification and heterotrophic denitrification were the main pathways in unsaturated VFCW, which depended on the energy substance and electron donor supplied by chemical oxygen demand (CODCr) in raw sewage. Nitrifier, anammox bacteria and autotrophic denitrifies prevailed in the subsequent saturated CWs, which tend to nitrogen loss by partial nitrification and anammox in HFCW when fed with NH4+-N wastewater with low CODCr. Providing NH4+-N and oxygen in low CODCr wastewater was the essential step to facilitate anammox process in HFCW. It implied that the problem of poor nitrogen removal due to carbon limitation could be overcome by optimizing conditions in anammox's favor.

Bibliometric analysis of microbial sulfonamide degradation: Development, hotspots and trend directions.

Microbial sulfonamide degradation (MSD) is an efficient and safe treatment in both natural and engineered ecosystems. In order to systematically understand the research status and frontier trends of MSD, this study employed CiteSpace to conduct a bibliometric analysis of data from the Web of Science (WoS) and the China National Knowledge Infrastructure (CNKI) published from 2000 to 2021. During this time, China, Germany, Spain, the United States and Australia played leading roles by producing numerous high impact publications, while the Chinese Academy of Sciences was the leading research institution in this interdisciplinary research category. The Chemosphere was the top journal in terms of the number of citations. MSD research has gradually progressed from basic laboratory-based experiments to more complex environmental microbial communities and finally to deeper research on molecular mechanisms and engineering applications. Although multi-omics and synthetic community are the key techniques in the frontier research, they are also the current challenges in this field. A summary of published articles shows that Proteobacteria, Gammaproteobacteria, Burkholderiales and Alcaligenaceae are the most frequently observed MSD phylum, class, order and family, respectively, while Bacillus, Pseudomonas and Achromobacter are the top three MSD genera. To our knowledge, this study is the first to investigate the development and current challenges of MSD research, put forward future perspective, and form a relatively complete list of sulfonamide-degrading microorganisms for reference.

The effect of rhizosphere and the plant species on the degradation of sulfonamides in model constructed wetlands treating synthetic domestic wastewater.

The effects of and main contributors in rhizosphere and plant species on the degradation of sulfonamides (SAs) in constructed wetland (CW) models for the treatment of domestic wastewater are currently unclear. To investigate the degradation and key rhizosphere factors of mixed SAs with sulfadiazine (SDZ), sulfapyridine (SPD), sulfamerazine (SMZ1), sulfamethazine (SMZ2), and sulfamethoxazole (SMX) at millimeter distances from the root surface, a multi-interlayer rhizobox experiment planted with Cyperus alternifolius, Juncus effusus, Cyperus papyrus, and an unvegetated control was conducted. There was a higher O2 saturation and dissolved organic carbon (DOC) content and a lower SA content in the rhizosphere and near/moderate-rhizosphere (0-3 and 3-8 mm from rhizosphere) than the far/non-rhizosphere (8-40 and 40-90 mm from rhizosphere). Bacterial abundance and community composition was indicative of the microbial degradation of SAs. Both the O2 and DOC contents promoted total bacterial abundance in different zones from CW rhizoboxes. The relative abundance of the most dominant bacteria was significantly correlated with O2, DOC, and SAs, except SMX, which also indicates other dissipation processes for SMX in the rhizosphere. Furthermore, more metabolites and aerobic SA-degrading bacteria were observed in the rhizosphere and near/moderate-rhizosphere than in the far/non-rhizosphere zones, suggesting that the effect of O2 in the rhizosphere is important in the degradation of SAs in CWs.

Keystone Species and Niche Differentiation Promote Microbial N, P, and COD Removal in Pilot Scale Constructed Wetlands Treating Domestic Sewage.

The microbial characteristics related to nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) removal were investigated in three pilot scale constructed wetlands (CWs). Compared to horizontal subsurface flow (HSSF) and surface flow (SF) CWs, the aerobic vertical flow (VF) CW enriched more functional bacteria carrying genes for nitrification (nxrA, amoA), denitrification (nosZ), dephosphorization (phoD), and methane oxidation (mmoX), while the removal of COD, total P, and total N increased by 33.28%, 255.28%, and 299.06%, respectively. The co-occurrence network of functional bacteria in the HSSF CW was complex, with equivalent bacterial cooperation and competition. Both the VF and SF CWs exhibited a simple functional topological structure. The VF CW reduced functional redundancy by forming niche differentiation, which filtered out keystone species that were closely related to each other, thus achieving effective sewage purification. Alternatively, bacterial niche overlap protected a single function in the SF CW. Compared with the construction type, temperature, and plants had less effect on nutrient removal in the CWs from this subtropical region. Partial least-squares path modeling (PLS-PM) suggests that high dissolved oxygen and oxidation-reduction potential promoted a diverse bacterial community and that the nonkeystone bacteria reduced external stress for functional bacteria, thereby indirectly promoting nutrient removal.

Potential for phytoremediation of neonicotinoids by nine wetland plants.

Broad-spectrum insecticides such as neonicotinoids tend to accumulate and detrimentally impact natural ecosystems. Accordingly, we aimed to assess the neonicotinoid phytoremediation abilities of nine wetland plant species commonly used in constructed wetland systems: Acorus calamus, Typha orientalis, Arundo donax, Thalia dealbata, Canna indica, Iris pseudacorus, Cyperus alternifolius, Cyperus papyrus and Juncus effusus. We assessed their removal of six neonicotinoids and explored the mechanisms responsible for the observed removal in a 28-day experiment. The planted systems effectively removed the neonicotinoids, with removal efficiencies of 9.5-99.9%. Compared with the other neonicotinoids, imidacloprid, thiacloprid and acetamiprid were most readily removed in the planted systems. C. alternifolius and C. papyrus exhibited the best removal performance for all six neonicotinoids. Based on our assessment of mass balance, the main removal processes were biodegradation and plant accumulation. Plants can enhance neonicotinoid removal through enhancing biodegradation. The differences in transport and accumulation behaviors may be related to plant species and physicochemical properties of neonicotinoids. Further research is merited on the toxicity of neonicotinoids to plants and microorganisms and the metabolic pathways by which neonicotinoids are broken down in wetland systems.

Impact of Phytoplankton Blooms on Concentrations of Antibiotics in Sediment and Snails in a Subtropical River, China.

The present three-year field investigation on sediment in the eutrophic Pearl River in South China showed that concentrations of sulfonamides (SAs), fluoroquinolones (FQs), and macrolides (MLs) in the river areas where blooms occurred were 4.6, 2.4, and 3.4 times higher than those without blooms, respectively, but the respective concentrations of tetracycline (TC) and oxytetracycline (OTC) in the areas with blooms were 2.6 and 3.8 times lower than those without. Significant positive correlations were found between concentrations of chlorophyll a in water and most antibiotics in sediment. Further investigation in each season suggested that lower diffusion but higher sinking were possible reasons driving the burial of sulfapyridine (SPD), sulfamethoxazole (SMX), and trimethoprim (TMP) in sediment from areas where blooms occurred, with burial rates up to 14.86, 48.58, and 52.19 g month-1, respectively. Concentrations of TCs in both water and sediment were inversely correlated with phytoplankton biomass, which might be related to the enhanced biodegradation capacity of bacteria caused by phytoplankton blooms. Phytoplankton also affected concentrations of antibiotics in the snail, Bellamya purificata, with higher values in March but lower values in September. The concentration of antibiotics in snails positively correlated with that in sediment when snails were dormant but with antibiotics in water after dormancy.

Irrigation using hybrid constructed wetland treated domestic sewage: Uptake of phthalic acid esters and antibiotics by Ipomoea aquatica forssk.

Irrigation with treated wastewater (WW) has been promoted to meet global water demands. This study investigates the occurrence and accumulation of targeted phthalic acid esters (PAEs) and antibiotics in soil and Ipomoea aquatica Forssk. irrigated with WW discharged from six hybrid constructed wetlands (HCWs), with evaluation of the associated human health risks. Results revealed that HCWs can effectively reduce the transfer of PAEs and antibiotics to soil and I. aquatica. HCW2 (VF-SF-HF) was found to be most efficient for the removal of PAEs (68.4%-95.3%) and antibiotics (28.5%-99.4%). Among the targeted PAEs, the concentration of bis (2-ethyl) hexylphthalate (DEHP) was the highest in irrigation water, soil and I. aquatica, while benzylphthalate (BBP) exhibited the highest bioconcentration factor (BCFF). Among the targeted antibiotics, the concentration of sulfapyridine (SPD) was highest in various environmental media, while norfloxacin (NFX) exhibited the highest BCFF. The properties of PAEs and antibiotics were found to be responsible for the differential uptake patterns. The estimation of the threshold of toxicological concern and hazard quotient showed that I. aquatica irrigated with HCWs treated wastewater presented a minor risk to human health. However, comprehensive safety evaluation is required for the widespread use of HCWs treated wastewater for irrigation purposes.

Differences in bacterial N, P, and COD removal in pilot-scale constructed wetlands with varying flow types.

The mechanisms of bacterial nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) removal in pilot-scale constructed wetlands (CWs) were investigated in the present work. Three types of CWs were assessed: vertical flow (VF), horizontal flow (HF), and surface flow (SF), each with three planting conditions, with either Thalia, Canna or without plants. The results show that construction types affected microbes more than planting conditions. VF CWs promoted the aerobic processing of total N, total P, COD, and NH3-N, increasing the respective removal efficiencies by 4-19%, 13-32%, 19-29%, and 75-80%, respectively, compared with SF CWs. The relative abundance of nitrifying, denitrifying, methanotrophic and dephosphorized bacteria, and functional genes such as nxrA, nirK, nosZ, mmoX, and phoD were higher in VF CWs. Positive and simple gene networks in VF CWs can effectively reduce the redundancy in functional genes, enhance bacterial function and gene interactions, thus promoting nutrient removal.

Enhanced performance of pilot-scale hybrid constructed wetlands with A/O reactor in raw domestic sewage treatment.

The aim of this study was to improve the nutrient removal efficiency by optimizing aeration time, hydraulic loading rate (HLR) and combination type in hybrid constructed wetlands (HCWs) with anoxic/oxic (A/O) reactor. The results showed that, the highest removal percentages of TN, NH4-N, TP, PO4-P and COD were 87.9%, 98.1%, 86.1%, 85.3% and 95.2%, respectively, in horizontal subsurface flow (HF) - surface flow - vertical subsurface flow CW with A/O reactor at 0.1 m/d HLR and 2 h aeration. HLR, aeration time and combination type had a significant impact on the removal of nutrients, though plant diversity did not have any significant influence. Presence of the A/O reactor improved the removal of TN in the HCWs by reducing influent loading and changing influent characteristics, thereby affecting the role of nitrification, anammox, and denitrification processes. The anammox process was the dominant pathway in the 1st HF CWs during the aeration period, where the highest removal of phosphorus was observed.

Pesticides in three rural rivers in Guangzhou, China: spatiotemporal distribution and ecological risk.

Frequent and widespread pesticide use is a major concern for both human and environmental health. The aim of this study was to screen for 19 pesticides in rural rivers in Guangzhou, China, evaluating the potential impact of detected pesticides on the local ecosystem. Sampling was performed in rural rivers in three environment types: agricultural, industrial, and unpolluted, with sampling of water and sediments in both wet and dry seasons. A total of 11 pesticides were detected overall and their spatiotemporal distribution in water and ecological risk were assessed. Five pesticides were detected at concentrations above 100 ng L-1, with the highest concentration pesticides being dimethoate (1318 ng L-1) in surface water and quinalphos (328 ng g-1 dry weight (dw)) in sediments. The most commonly detected pesticides were chlorpyrifos, acetochlor, and butachlor with detection frequencies of 50-57% and 29-43%, in water and sediments, respectively. Samples from the agricultural rural river contained the most pesticides and at higher concentrations, as compared to industrial and unpolluted areas, especially during the wet season. Ecotoxicological risk assessment through Risk Quotients (RQs) showed that chlorpyrifos and fenvalerate pose high ecological risks in water and therefore, reduction of the source input of these pesticides is essential.

Removal of chlorpyrifos in recirculating vertical flow constructed wetlands with five wetland plant species.

The removal efficiency of the pesticide chlorpyrifos (50 and 500 µg L-1) by five wetland plant species (Cyperus alternifolius, Canna indica, Iris pseudacorus, Juncus effusus and Typha orientalis) was studied in recirculating vertical flow constructed wetland systems (RVFCWs). Results reveal that for chlorpyrifos at different concentrations, good removal efficiencies (94-98%) were observed using the same plant systems, while no significant differences in removal efficiencies were seen between the different plant systems. In addition, the chlorpyrifos removal efficiency of the planted systems increased significantly compared with the unplanted controls. The chlorpyrifos removal efficiency for wetland systems over time fit to the first-order kinetic model, with the first-order kinetic constant (k) ranging from 0.045 to 0.065 h-1. The half-life of chlorpyrifos in the systems ranged from 10.66-15.43 h. The shortest chlorpyrifos half-life was detected in the wetland system containing C. indica, followed by that with C. alternifolius and I. pseudacorus. The main pathways to remove chlorpyrifos in these wetland systems were sorption (accounting for 64.6-86.4% of the total removal efficiency) and biodegradation (8.1-33.7%). Plants can enhance chlorpyrifos removal through enhanced biodegradation in the system. Plants with high biomass and transpiration were able to accelerate the removal of chlorpyrifos and conventional pollutants. Hence, C. indica, C. alternifolius and I. pseudacorus could be used as optimal plants for pesticide removal in wetland systems.

Improved DNA purification with quality assurance for evaluation of the microbial genetic content of constructed wetlands.

Efficient isolation of target DNA is a crucial first step of DNA-based metagenomic analyses of environmental samples. Insufficient quantity and purity of DNA isolated using commercial kits result in missing genetic information, especially for large-diameter substrates in constructed wetlands (CWs). Here, we addressed this problem by devising a cost-effective calcium chloride lysozyme-sodium dodecyl sulfate (SDS) method (CCLS), with key improvements in the steps of humic acid removal and cell lysis. The buffer comprising Tris, EDTA, Na2O2P7 and PVPP (TENP), and skim milk, could reduce adsorption between microorganisms and substrates, and calcium chloride precipitated and removed over 94% of humic acid. This humic acid removal step, when compared to the PowerSoil DNA kit (MO BIO Laboratories Inc.) (MBKIT), significantly enhanced the DNA purity (A260/230) from 0.68 to 1.63 (p < 0.01). When gentle and extended cell lysis in CCLS replaced the short but violent bead-beating in the MBKIT, DNA yield and the amount of lysed bacteria detected by quantitative real-time polymerase chain reaction (qPCR) on average increased by 2 and 4 folds, respectively, compared to that obtained using the MBKIT (p < 0.01). Furthermore, the full-length bacterial 16S rRNA gene and nirK gene from denitrifying microorganisms were successfully amplified from CCLS-generated DNA. Additionally, bacterial diversity indices of richness, Shannon, and evenness examined by denaturing gradient gel electrophoresis (DGGE) increased by 75, 30, and 7%, respectively, by CCLS compared to that using the MBKIT. Hence, the CCLS method enables improved evaluation of microbial density and diversity in CW systems.

Biogenic manganese oxides generated by green algae Desmodesmus sp. WR1 to improve bisphenol A removal.

Biogenic manganese oxides (BioMnOx) have attracted considerable attention as active oxidants, adsorbents, and catalysts. This study investigated the characteristics of algae-generated BioMnOx and determined its oxidative activity towards bisphenol A (BPA), an endocrine disrupter. Amorphous nanoparticles with a primary Mn valency of +3 were found in BioMnOx produced by Desmodesmus sp. WR1. The mechanism might be that algal growth created conditions favorable to Mn oxidation through increasing DO and pH. Initial Mn2+ concentrations of 6, 30, and 50mgL-1 produced a maximum of 5, 13, and 11mgL-1 of BioMnOx, respectively. Mn2+-enriched cultures exhibited the highest BPA removal efficiency (∼78%), while controls only reached about 27%. BioMnOx may significantly promote BPA oxidation in algae culture, enhancing the accumulation of substrates for glycosylation. Moreover, continuous BioMnOx increase and Mn2+ decrease during BPA oxidation confirmed Mn oxide regeneration. In conclusion, Mn oxide formation by microalgae has the potential to be used for environmental remediation.

Transformation of chlorpyrifos in integrated recirculating constructed wetlands (IRCWs) as revealed by compound-specific stable isotope (CSIA) and microbial community structure analysis.

Carbon isotope analysis and 454 pyrosequencing methods were used to investigate in situ biodegradation of chlorpyrifos during its transport through three model integrated recirculating constructed wetlands (IRCWs). Results show that plant and Fe-impregnated biochar promoted degradation of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol (TCP). Carbon isotope ratios in the IRCWs shifted to -31.24±0.58‰ (IRCW1, plant free), -26.82±0.60‰ (IRCW2, with plant) and -24.76±0.94‰ (IRCW3, with plant and Fe-biochar). The enrichment factors (Ɛbulk,c) were determined as -0.69±0.06‰ (IRCW1), -0.91±0.07‰ (IRCW2) and -1.03±0.09‰ (IRCW3). Microbial community analysis showed that IRCW3 was dominated by members of Bacillus, which can utilize and degrade chlorpyrifos. These results reveal that plant and Fe-biochar can induce carbon isotope fractionation and have a positive impact on the chlorpyrifos degradation efficiency by influencing the development of beneficial microbial communities.

Factors Affecting Behavior of Phenolic Endocrine Disruptors, Estrone and Estradiol, in Constructed Wetlands for Domestic Sewage Treatment.

This study investigated the efficiency of 12 pilot-scale constructed wetlands (CWs) with different configurations on the removal of estrone and estradiol from raw domestic sewage. An orthogonal design was employed to evaluate the impact of four principal design parameters of CWs, including four wetland types, three substrates, three plant conditions, and three hydraulic loading rates, in summer and winter. A bench-scale anoxic simulation test was performed in the laboratory to clarify the photolysis, sorption, and degradation of estrogens. Estrogens were more effectively removed by the 12 CWs during summer. The experiment showed that target estrogens were efficiently removed by wetland substrate under anoxic conditions through exothermic sorption and degradation even in winter. This suggests that the inefficient removal in CWs in winter likely resulted from subsequent cleavage of a considerable amount of estrogen conjugates in influent due to insufficient decomposition at low temperatures. The transformation from estradiol to estrone could be driven by residual microbial activities not inhibited by azide, and the reversible process was then driven by active microorganisms but not solely abiotic redox reactions. Among the four design parameters, wetland-type was the most important and downward-vertical flow CWs performed best.

Fate of mixed pesticides in an integrated recirculating constructed wetland (IRCW).

In this study, three model integrated recirculating constructed wetlands (IRCWs) planted with and without Cyperus alternifolius were used to investigate their ability to remove four pesticides (chlorpyrifos, endosulfan, fenvalerate, diuron). Iron (Fe)-impregnated biochar produced by Cyperus alternifolius was added as a primary substrate. Results showed that all four pesticides were efficiently removed in the three IRCWs. The highest pesticide removals were achieved when Fe-impregnated biochar was added to the IRCW (99%), followed by the planted (64-99%) and plant-free IRCW (45-99%). The removal of pesticides in IRCWs followed first-order kinetics, with half-lives of 1.5-11.6h. A mass balance study revealed that sorption (32.2-98.6%) and microbial degradation (1.3-52.8%) were the main removal processes in all IRCWs. This study suggests that the IRCW is a promising system to treat pesticide-contaminated water, and plant and Fe-impregnated biochar can enhance pesticide removal.

Removal and factors influencing removal of sulfonamides and trimethoprim from domestic sewage in constructed wetlands.

Twelve pilot-scale constructed wetlands with different configurations were set up in the field to evaluate the removal and factors that influence removal of sulfonamides (sulfadiazine, sulfapyridine, sulfacetamide, sulfamethazine and sulfamethoxazole) and trimethoprim from domestic sewage. The treatments included four flow types, three substrates, two plants and three hydraulic loading rates across two seasons (summer and winter). Most target antibiotics were efficiently removed by specific constructed wetlands; in particular, all types of constructed wetlands performed well for the degradation of sulfapyridine. Flow types were the most important influencing factor in this study, and the best removal of sulfonamides was achieved in vertical subsurface-flow constructed wetlands; however, the opposite phenomenon was found with trimethoprim. Significant relationships were observed between antibiotic degradation and higher temperature and redox potential, which indicated that microbiological pathways were the most probable degradation route for sulfonamides and trimethoprim in constructed wetlands.