Subsurface Flow Wetlands Research Articles

Evaluation the Efficiency of Subsurface Flow Constructed Wetland (SSF) for Wastewater Treatment and Reuse in Semi-arid Environment

The efficiency of subsurface flow (SSF) constructed wetlands was evaluated on the treatment of secondary treated wastewater to improve the quality of the effluent for reuse purposes. A horizontal SSF system was constructed to evaluate the efficiency to enhance the quality of secondary treated wastewater effluent from Ramtha wastewater treatment plant WWTP and its potential uses for crop production at Hydrulic retention time HRT of 1 day. The SSF was planted with barley crop (Hordium vulgare), retrieved from the Arab Center for the Studies of Arid Zones and Dry-land (ACSAD) variety followed by corn crop (Zea mays L.), using BONANZA, F1 variety in the other season. Weekly physicochemical and microbiological analyses were carried out on the outlet from the wetlands in addition to the TWW treated wastewater effluent (inlet) in order to assess the removal efficiency of each stage of the treatment process and the total treatment system and it was used for irrigation of a fodder crop field. The SSF wetland subsequently influenced the physicochemical parameters. The SSF reduced the concentration of COD, NO-3, and TKN by 48%, 18%, and 20% respectively. Water use efficiency (WUE) for corn and barley were improved tremendously compared to the traditional irrigation techniques used in the field. The results showed a great possibility of using the SSF wetlands for the growth and production of fodder crops.

Hybrid wetland system for a pet-care center wastewater treatment

A hybrid wetland (HW) consisting of a free-water surface flow wetland (FWSW) followed by a horizontal subsurface flow wetland (HSSFW) was constructed for the final treatment of wastewater from a pet-care center. Typha domingensis was planted in both wetlands. During the first year of operation, wastewater was separated from solid pet waste (first period). Then, that solid waste and liquid wastewater were treated together, causing a significant increase in the concentration of the pollutants (N, P, and organic matter) in the effluent treated in the HW (second period). The objectives of this work were to evaluate the performance of the system and compare its efficiency between periods. The HW was efficient in both periods, except for nitrate removal. Total mean removals were: 66.9 and 82.8% for COD, 74.9 and 88.3% for BOD, 61.9 and 83.0% for ammonium, 67.7 and 83.8% for TKN, 5.65 and 20.37% for nitrate, and 56.9 and 62.1% for TP in the first and second period, respectively. In the second period, mean removal efficiency percentages increased and the contaminant concentrations in the outlet were not significantly different from those of the first period. In the second period, the highest pollutant removal occurred in the FWSW mainly for COD, BOD and TKN. TP and TKN concentrations in plant tissues of the inlet area of FWSW were significantly higher than those in plants from the HSSFW. The study showed that this HW is a low cost, efficient and sustainable solution for the pet-care center wastewater treatment.

Escherichia coli removal in a treatment wetland - pond system: A mathematical modelling experience

A full-scale treatment wetland (TW) (100 inhabitants, 14 m3·d−1), composed of two horizontal subsurface flow wetlands (TW1–400 m2 and TW2–200 m2) and a small pond (13 m2), has been evaluated for Escherichia coli (E. coli) removal. The results indicate a global removal from 1.74·106 to 685 MPN·100 mL−1 (3.41 log units), reducing E. coli sufficiently to reach values suitable for reuse purposes such as agricultural reuse, without energy and reagent consumption. The small pond at the end of the treatment train plays an important role in E. coli removal and biodiversity enhancement. Data from TW1 and TW2 have been fitted to the P-k-C* model, giving values of 134 and 100 m·yr−1 for the first-order kinetic reaction coefficient. For the pond, a process-based model using continuous stirred-tank reactor (CSTR) and a 3d-CFD model have been implemented and compared. The models indicate that solar disinfection and predation by daphnids are the most important mechanisms in the studied pond, representing 65% and 25% of the removal respectively. It can be concluded that CSTR can provide good results for small ponds and 3d-CFD model provides extra information, useful to enhance their design.

Distribution coefficients of nitrogen pollutants between water and sediment and their environmental risks in Lingang hybrid constructed wetland fed by industrial tailwater, Tianjin, China.

Exploring the fate of nitrogen pollutants in constructed wetlands (CWs) fed by industrial tailwater is significant to strengthen its pollution control and promoting the development of CWs in the field of micro-polluted water treatment. In this study, the distribution coefficients and the environmental risks of nitrogen pollutants between water and sediment of the hybrid CW in Tianjin were systematically investigated. From a spatial perspective, the nitrogen pollutants could be removed in this hybrid CW, and subsurface flow wetland played a key role in nitrogen pollutant removal. From a temporal perspective, the concentration of nitrogen pollutants was largely affected by the dissolved oxygen (DO) and temperature. The distribution coefficient of nitrogen pollutants between water and sediment was further clarified, suggesting that NH4+-N was more likely to be enriched in sediments due to microbial process. The overall level of pollution in hybrid CW was moderate according to the nutritional pollution index (NPI) analysis. The risk assessment indicated that timely dredging control measures should be considered to maintain the performance of hybrid CW.

Pengembangan Booklet Pengolahan Limbah Industri Tahu Menggunakan SSF-Wetlands dengan Tanaman Eceng Gondok

Liquid waste generated from the tofu industry contains organic substances, namely 40%-60% protein, 25%-50% carbohydrates, 10% fat, and other suspended solids that can undergo physical, chemical, and biological changes to produce toxic substances. To overcome the pollution caused by the disposal of industrial liquid waste, research on the development of a tofu industrial waste treatment booklet using subsurface flow-wetlands was carried out with water hyacinth plants. This aims to improve the understanding and skills of tofu industry owners so that tofu industry owners can practice on their own about tofu industrial waste treatment after reading the booklet. This research method uses the Thiagarajan media development model, there are 4 stages, namely: definition, design, development, and disseminate. However, this research was carried out only until the development stage. The results of the validation assessment validation test from material experts obtained an assessment percentage of 86% and media experts obtained an assessment percentage of 82.85% with the achievement criteria being very suitable or very valid according to the BSNP criteria. In conclusion, the booklet developed has very interesting qualifications, is very appropriate, and is effective, and has few revisions. so that the booklet media is suitable to be used and disseminated as a media for outreach to the owners of the tofu industry.

Using subsurface flow wetlands with Phragmites australis as a bioremediation alternative for surface sources affected by acid drainage from coal mines

espanolLa mineria genera impactos ambientales como drenajes acidos de minas (DAM). El rio Cali es uno de los principales recursos hidricos de la ciudad de Santiago de Cali, Colombia, y esta afectado por los drenajes procedentes de minas abandonadas que llegan a traves de la quebrada Las Minas. Como alternativas de biorremediacion se evaluo el uso de humedales de flujo subsuperficial, ademas de piedra caliza como pretratamiento. La metodologia de la investigacion se estructuro en dos etapas: a) caracterizacion fisicoquimica del agua de la quebrada y b) operacion de los sistemas de tratamiento. Se evaluaron cuatro sistemas: 1) humedal con especie vegetal (H1); 2) piedra caliza + H1 (PC + H1); 3) humedal sin especie vegetal (H2), y 4) piedra caliza + H2 (PC + H2). Los resultados mostraron que el agua de la quebrada Las Minas presenta caracteristicas similares a DAM (pH: 2.4-4.0 unidades; acidez: 1 303.2 mg/l ± 139.2; hierro: 715.3 mg/l ± 70.6; sulfatos: 1 134.5 mg/l ± 314.6), y afecta al rio Cali principalmente por el incremento del hierro, aluminio y presencia de precipitados de hidroxido ferrico. Se observo que los sistemas de tratamiento que emplearon PC lograron mayores eficiencias; es recomendable la configuracion PC + H1. Todos los sistemas lograron reducir la acidez del afluente en un rango promedio de 31 y 52 %, y se alcanzaron eficiencias de remocion promedio de hierro total entre 54 y 67 %; sulfatos entre 16 y 35 %; niquel entre 25 y 50 %, y aluminio entre 0 y 73 %. No se logro remover manganeso. EnglishMining generates environmental impacts such as Acid Mine Drainage (AMD). The Cali River is one of the main water resources in the city of Santiago de Cali, Colombia and it is affected by drainage from abandoned mines, which reach the Cali River through the Las Minas brook. As bioremediation alternatives, the use of subsurface flow wetlands coupled with a limestone-based pretreatment was assessed in this study. The research methodology was structured in two stages: a) physicochemical monitoring of Las Minas brook waters, and b) treatment system operations. For these purposes, four systems were evaluated: 1) Wetlands with plants (WL1), 2) Limestone + WL1 (LS + WL1), 3) Wetlands without plants (WL2) and 4) Limestone + WL2 (LS + WL2). The results revealed that the water from the Las Minas brook presents characteristics similar to AMD (pH: 2.4-4.0; acidity: 1 303.2 mg/l ± 139.2; iron: 715.3 mg/50 ± 70.6; sulfate: 1 134.5 mg/l ± 314.6) and affects the Cali River mainly owing to the increase in iron, aluminum, and the presence of ferric hydroxide precipitates. In addition, limestone-based treatment systems achieved greater efficiencies, and the LS + WL1 configuration is recommended. All systems were able to reduce the affluent acidity from 31 to 52 %. Furthermore, the average iron removal efficiencies achieved were between 54 and 67 %; sulfates between 16 and 35 %, nickel between 25 and 50 %, and aluminum between 0 and 73 %. However, manganese could not be removed.

Treatment of swine effluent mixed with domestic wastewater and vegetation development in monoculture and polyculture horizontal subsurface flow wetlands

The aim of this study was to evaluate horizontal subsurface flow (HSSF) treatment wetlands (TW) for the treatment of swine effluents mixed with domestic wastewater, as well as to compare the efficiency of systems with monocultures and polycultures. Three species of plants were used in both monoculture and polyculture experimental systems: a) Heliconia latispatha, b) Typha latifolia, c) Cyperus alternifolius, d) Heliconia latispatha + Typha latifolia, e) Heliconia latispatha + Cyperus alternifolius and f) control (without plant). Each cell operated with a hydraulic loading rate of 5.4 cm/d. The measured variables included environmental parameters (temperature, relative humidity, light intensity, evapotranspiration, pH and dissolved oxygen –DO–), vegetative growth (plant height, width and leaf length, stem thickness, leaf number and biomass production) and pollutant measurements (chemical oxygen demand –COD–, total coliforms –TC–, total suspended solids –TSS–, volatile suspended solids –VSS–, total nitrogen –TN– and total phosphorus –TP–). The results indicated that there were significant differences (p ≤ 0.001) between the systems. In general, those systems with vegetation removed more TP (from 44.3% to 63.4%) and TN (from 68.1% to 74.9%) than the system without vegetation (32.9% for TP and 55.6% for TN). In addition, the experimental configuration as mono or polyculture was a determinant factor in the efficiency of the systems; the polyculture system with H. latispatha + T. latifolia was the most efficient in the removal pollutants such as COD (68.9 ± 10.6%), TSS (55.6 ± 0.5%), VSS (57.8 ± 0.6%), TC (69.5 ± 6.1%) and TN (74.9 ± 1.4). With regard to the evaluated species, H. latispatha showed the highest relative growth in both monoculture and polyculture systems with this high nutrient-concentration wastewater. These results demonstrate the HSSF TWs planted with monocultures and polycultures of plants in tropical climates represent an option to reduce the pollutant load of wastewater resulting from the mixing of domestic wastewater and pig farming wastewater.

CONSTRUCTED WETLANDS A COMPREHENSIVE REVIEW

Constructed wetlands are wastewater treatment systems composed of one or more treatment cells in a building designed and constructed to provide wastewater treatment. Constructed wetlands are classified into two types: free water surface (FWS) wetlands (also known as surface flow wetlands) closely resemble natural wetlands in appearance because they contain aquatic plants that are rooted in a soil layer on the bottom of the wetland and water flows through the leaves and stems of plants. Subsurface flow wetlands (SSF) or known as a vegetated submerged bed (VSB) systems do not resemble natural wetlands because they have no standing water. They contain a bed of media (such as crushed rock, small stones, gravel, sand, or soil) that has been planted with aquatic plants. When properly designed and operated, wastewater stays beneath the surface of the media, flows in contact with the roots and rhizomes of the plants, and is not visible or available to wildlife. Constructed wetlands are an appropriate technology for areas where inexpensive land is generally available and skilled labor is less available. In this paper, a comprehensive review covered types, characteristics, design variation and considerations, limitations, and the advantages and disadvantages of constructed wetlands.

장기운영을 통한 친환경 수처리 기술의 하천수 수질개선 효율 평가

Eco-friendly water treatment technology is emerging as a countermeasure to improve the quality of river water and source water. Among various eco-friendly water treatment technologies such as subsurface flow (SSF) and surface flow (SF) wetlands, vertical flow constructed wetland (VFCW) which is one of the SSF wetland is being used in the Netherlands as post-treatment for decentralized sewage treatment plants due to greater cold tolerance than general SF wetlands. In addition, SSF wetlands are less affected by seasonal water temperature fluctuations than SF wetlands, so they have the advantage of providing stable water treatment. In this study, an eco-friendly water treatment test-bed was installed for evaluation of applicability on river water (Yeongsan river water) at near Seung-chon weir and was operated for more than one year. A VFCW with 0.4 m/d showed excellent treatment efficiency of 83.8% turbidity 83.8%, SS 95.6%, BOD 93.6%, and T-P 73.7% and showed low treatment efficiency of 33.8% TOC and 31.0% T-N. At 1m/day, the treatment efficiency was similar to 0.4m/day. However, in the case of 2m/day or more, the treatment efficiency tended to decrease somewhat as the filtration speed increased. In the seasonal evaluation, there was little change in treatment efficiency by season in most of the water quality items except for T-N. As a result of organic material characterization, the proportion of non-degradable organic matter in both accounted for most of 74.4~81.4%, resulting in a low treatment efficiency of about 5.7%.

Removal of micropollutants and biological effects by conventional and intensified constructed wetlands treating municipal wastewater

Seven treatment wetlands and a municipal wastewater treatment plant (WWTP) were weekly monitored over the course of one year for removal of conventional wastewater parameters, selected micropollutants (caffeine, ibuprofen, naproxen, benzotriazole, diclofenac, acesulfame, and carbamazepine) and biological effects. The treatment wetland designs investigated include a horizontal subsurface flow (HF) wetland and a variety of wetlands with intensification (aeration, two-stages, or reciprocating flow). Complementary to the common approach of analyzing individual chemicals, in vitro bioassays can detect the toxicity of a mixture of known and unknown components given in a water sample. A panel of five in vitro cell-based reporter gene bioassays was selected to cover environmentally relevant endpoints (AhR: indicative of activation of the aryl hydrocarbon receptor; PPARγ: binding to the peroxisome proliferator-activated receptor gamma; ERα: activation of the estrogen receptor alpha; GR: activation of the glucocorticoid receptor; oxidative stress response). While carbamazepine was persistent in the intensified treatment wetlands, mean monthly mass removal of up to 51% was achieved in the HF wetland. The two-stage wetland system showed highest removal efficacy for all biological effects (91% to >99%). The removal efficacy for biological effects ranged from 56% to 77% for the HF wetland and 60% to 99% for the WWTP. Bioanalytical equivalent concentrations (BEQs) for AhR, PPARγ, and oxidative stress response were often below the recommended effect-based trigger (EBT) values for surface water, indicating the great benefit for using nature-based solutions for water treatment. Intensified treatment wetlands remove both individual micropollutants and mixture effects more efficiently than conventional (non-aerated) HF wetlands, and in some cases, the WWTP.

Pollutants removal efficiency assessment of constructed subsurface flow wetlands in lakes with numerical models

Ecological remediation with subsurface flow wetland is one of the most widely used methods for pollution abatement. Assessment on its implementation efficiency is necessary but difficult. To evaluate the pollutant removal effect of constructed subsurface flow wetlands, a wetland growth model coupling with a hydrodynamic water quality model has been put forward. The coupled model has been used to assess the impact of constructed subsurface flow wetlands on a polluted lake in Hubei Province, China. Four pieces of constructed subsurface flow wetlands composed of Reed and Smooth cordgrass with total area of 38.9 thousand square meters for pollutant removal have been designed for the lake. Results showed that reductions of chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN) were 246.38, 28.14 and 3.29 tons/year, respectively. Compared with the different pollutants, the removal efficiency of subsurface flow wetlands on TN (49%) is bigger than TP (34%), but less than COD (60%). Furthermore, the higher water temperature, smaller flow velocity and bigger water depth will improve the pollutants removal performance of subsurface flow wetlands.

Coupling transformation of carbon, nitrogen and sulfur in a long-term operated full-scale constructed wetland.

The coupling transformation of carbon, nitrogen and sulfur compounds has been studied in lab-scale and pilot-scale constructed wetlands (CWs), but few studies investigated full-scale CW. In this study, we used batch experiments to investigate the potentials of carbon, nitrogen and sulfur transformation in a long-term operated, full-scale horizontal subsurface flow wetland. The sediments collected from the HSFW were incubated for 48h in the laboratory with supplying various dosages of carbon, nitrogen and sulfur compounds. The results showed that heterotrophic denitrification was the main pathway. At the same time, the sulfide (S2-)-based autotrophic denitrification was also present. Increasing TOC concentration or NO3- concentration could promote heterotrophic denitrification but did not inhibit the sulfide-based autotrophic denitrification. In our experiment, the highest NO3- removal via autotrophic denitrification was 25.23% while that via heterotrophic denitrification was 73.66%, leading to the total NO3- removal of 98.89%. The results also demonstrated that NO3- rather than NO2- was the preferable electron acceptor for both heterotrophic and sulfide-based autotrophic denitrification in the CW. Increasing S2- concentrations promote NO3- removal from 12.99% to 25.23% without organic carbon, but varying NO3- or NO2- has no effects. These results indicated that concentrations of S2-, instead of NO3- or NO2-, was the limiting factor for sulfide-based autotrophic denitrification in the studied CW. The microbial community analysis and correlation analysis between the transformation of carbon, nitrogen and sulfur compounds and relative abundance of bacteria further confirmed that in the CW, the key pathways coupling transformation were heterotrophic denitrification and sulfide-based autotrophic denitrification. Overall, the current study will enhance understanding of carbon, nitrogen, and sulfur transformation in CW and support better design and treatment efficiency.

Influence of plant types, bed media and feeding patterns on wastewater treatment performance of wetland roofs

This study investigated the effects of two local plants (Wedelia Trilobata - WT, Axonopus Compressus - AC), feeding patterns (continuous and intermittent), and types of bed media (sand and charcoal) on the treatment performance of shallow bed subsurface flow wetland roofs (WRs). Results showed that changing plant from AC into WT led to an increase in removal rate by 6–12 % for COD and 11–13 % for total nitrogen (TN). The removal rate accelerated by 8 % for COD, 45–64 % for TN and 125 % for total phosphorus (TP) when changing from sand to charcoal as bed media. Continuous feeding mode enhanced the removal rate by 17–19 % for COD and 11–13 % for TN, compared to intermittent feeding mode. The findings suggested that the treatment capacity of WR was significantly affected by the type of plant, bed material and feeding pattern.

Promotion of full-scale constructed wetlands in the wine sector: Comparison of greenhouse gas emissions with activated sludge systems

The aim of this study was to quantify and compare greenhouse gas (GHG) (i.e. carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)) emissions from two full-scale winery wastewater and sludge treatment systems (i.e. constructed wetlands (CWs) and activated sludge system) located in Galicia (Spain). GHG fluxes were measured using the static chamber method in combination with an on-site Fourier transform infrared spectroscopy (FTIR) gas analyser in the CWs system. These on-site innovative techniques proved to be very accurate and reliable. In the activated sludge treatment systems, the floating chamber method in combination with the FTIR gas analyser was used. Measurements were carried out during the vintage season, when winery wastewater has the highest flow and loads, and the rest of the year. Emission rates of CO2, N2O and CH4 in the CWs units (i.e. vertical flow, horizontal subsurface flow and sludge treatment wetlands) ranged from 1.35E+02 to 7.54E+04, 1.70E-01 to 3.09E+01 and − 3.05E+01 to 1.79E+03 mg m−2 day−1, respectively. In the case of the activated sludge units (i.e. reactor, secondary settler and sludge storage tank) emission rates of CO2, N2O and CH4 ranged from 1.56E+04 to 1.43E+05, 1.13E+01 to 4.75E+01 and 2.52E+01 to 1.01E+03 mg m−2 day−1, respectively. Seasonally, daily and instantaneous variability in emissions as well as spatial variability was found. Comparing CWs with the activated sludge system, surface emission rates were lower in the CWs system in both seasons considered. Results highlighted that CWs are suitable technologies that can help to reduce GHG emissions associated with winery wastewater treatment.

Occurrence of Chlorinated Paraffins in a Wetland Ecosystem: Removal and Distribution in Plants and Sediments.

Constructed wetlands (CWs) are of great socioeconomic significance because they can remove anthropogenic compounds from aquatic environments. However, no information is available about the removal of persistent chlorinated paraffins by CWs. This study investigates the occurrences, fates, and mass balances of short-chain chlorinated paraffins (SCCPs), medium-chain chlorinated paraffins (MCCPs), and long-chain chlorinated paraffins (LCCPs) in a CW ecosystem. MCCPs were the predominant compounds in water, sediments, and plants within the system. The amounts of SCCPs, MCCPs, and LCCPs entering the wetland were 3.3, 6.8, and 3.4 g/day, respectively. Overall removal efficiencies were 51-78%, 76-86%, and 76-91% for SCCPs, MCCPs, and LCCPs, respectively, and the greatest reduction in CPs was observed in the subsurface flow wetland unit. CPs were predominantly adsorbed onto the sediment and bioaccumulated in the plants, and their organic carbon-water partitioning and plant-water accumulation increased as the carbon and chlorine numbers increased. Sediment sorption (12-38%) and degradation (12-50%) contributed the most to the removal of CPs, but bioaccumulation of CPs in plants (3.8-12%) should not be neglected. Wetlands can economically remove large amounts of CPs, but sediment in the wetland systems could be a sink for CP pollutants.

Effectiveness of Subsurface Flow-Wetlands to Reducing TSS Levels and Stabilizing pH in Tofu Liquid Waste

Small and medium industries are experiencing growth every year. The home industry of tofu production is one of the small and medium industries that continues to grow and develop. However, there is a problem if the tofu production waste is disposed of directly into the waters, it will cause pollution due to the deposition of organic material. The research objective was to analyze the subsurface flow-wetlands with plants namely water hyacinth, apu wood and lemna minor to reducing TSS levels and stabilizing pH. This research an experimental with treatments including SSF-Wetlands without water plants (A1), SSF-Wetlands with water hyacinth (A2), SSF-Wetlands with apu wood (A3), SSF-Wetlands with lemna minor (A4) and SSF-Wetlands with water hyacinth, and apu wood (A5). The stages of this research are the sampling stage, the SSF-Wetlands manufacturing stage, the waste treatment stage and the pH and TSS testing stages. Data were analyzed using one-way ANOVA (SPSS 20). The results showed that the liquid waste of tofu in the initial sample was acidic, namely 3.94 and the TSS level was 858 mg / L. The pH condition of the waste after processing by the quality standard.  The highest increase in pH and decrease in TSS levels in the tofu liquid waste treatment was the SSF-Wetland processing with water hyacinth plants (A2). This shows that water hyacinth plants have a greater role in neutralizing pH and can absorb the most suspended matter compared to apu wood and lemna minor plants.

Study on water purification effects and microbial community compositions of the estuarine wetland buffer zones during a low-temperature period

The estuarine wetland buffer zone of the Fuhe river plays an important role in terms of improving water quality of Baiyangdian lake. In this study, the water purification effect and microbial community composition of an estuarine wetland buffer zone during a low-temperature period were investigated (March, 2021). The results indicated that the pre-sedimentation ecological pond (Pep), the subsurface flow wetland (Sfw), and the aquatic plant pond (App) exhibited good removal effects on total phosphorus (TP) and NH3-N. In contrast, the removal effects on chemical oxygen demand (COD) and total nitrogen (TN) was unsatisfied. Various phosphorus removal bacteria were detected in the water samples from the Pep and the Sfw, such as Arthrobacter, Flavobacterium, and Planococcus. These findings indicated the water purification performance and the microbial community composition in an estuarine wetland buffer zone during a low-temperature period.

Characteristic of a Suspended Media Bed to Reduce or Eliminate Clogging in Subsurface Constructed Wetland

Clogging is a common and difficult problem in subsurface flow wetlands. In this study, 2-4mm, 4-8mm, 8-10mm lightweight ceramsite were used as suspended media beds and 5-10mm gravel was used as traditional substrate bed as control. The effects of these four substrate beds on the purification of water quality and the change of flow capacity in the clogging process in the non-deformable inorganic particle wastewater, deformable inorganic particle wastewater and organic particle wastewater were studied. After the beds were clogged, using the characteristics of lightweight ceramsite floating up and down with water level, the mitigation effect of clogging with water level fluctuation at different heights (10 cm, 20 cm, 30 cm, 40 cm) was explored. The results showed that four kinds of beds had effect on the removal of turbidity and suspended particles. The beds in the treatment of non-deformable inorganic particle wastewater were more likely to cause wetland gap clogging; In the absence of plants, compared with inorganic particles, the clogging degree of substrate in the treatment of organic suspended particulate wastewater was not obvious. After clogging, lightweight ceramsite floats up and down with the water level, three kinds of wetland clogging have been alleviated to some extent.

Long term effect of biochar on the efficiency of subsurface flow wetland pollutant treatment

Long term effect of biochar on the efficiency of subsurface flow wetland pollutant treatment

Factors influencing the persistence of enteropathogenic bacteria in wetland habitats and implications for water quality.

To better understand the persistence dynamics of enteropathogenic bacteria in freshwater wetland habitats, we constructed lab-scale mesocosms planted with two different wetland plant species using a subsurface flow wetland design. Mesocosms were treated with either a high-quality or a poor-quality water source to examine the effects of water quality exposure and plant species on Escherichia coli, Salmonella spp. and Enterococcus spp. in the rhizoplane, rhizosphere and water of wetland habitats. Quantities of study micro-organisms were detected using real-time PCR in wetland mesocosms. A combination of molecular and culture-based methods was also used to enumerate these organisms from surface water and plant material at high, medium and poor water quality sites in the field. We found that all three enteropathogenic micro-organisms were influenced by microhabitat type and plant species. Organisms differed with respect to their predominant microhabitat and the extent of persistence associated with wetland plant species in the mesocosm study. Of the monitored pathogens, only E. coli was influenced by both water quality treatment and plant species. Salmonella spp. quantities in the rhizoplane consistently increased in all treatments over the course of the mesocosm experiment. Plant species selection appears to be an overlooked aspect of constructed wetland design with respect to the removal of enteropathogenic micro-organisms. Escherichia coli and Enterococcus concentrations in wetland outflow were significantly different between the two plant species tested, with Enterococcus concentrations being significantly higher in mesocosms planted with Phalaris arundinaceae and E. coli concentrations being higher in mesocosms planted with Veronica anagallis-aquatica. Furthermore, there is evidence that the rhizoplane is a significant reservoir for Salmonella spp. within wetland habitats. This is the first time that Salmonella spp. has been shown to proliferate under natural conditions within the rhizoplane. This will contribute to our understanding of wetland removal mechanisms for enteropathogenic bacteria. This study identifies the rhizoplane as a potentially important reservoir for human pathogenic micro-organisms and warrants additional study to establish whether this finding is applicable in non-wetland habitats.