Subsurface Flow Wetlands Research Articles

Behavior of horizontal sub-surface flow wetlands as an alternative for the wastewater treatment contaminated with florfenicol

In recent years, the increase in the use and production of antibiotics for the protection of animals has been associated not only with human health problems due to bacterial resistance, but also with environmental problems, which have led to the deterioration of the water resources, since a large part of these are discharged into the environment without any type of treatment. This situation has highlighted the fact that a large part of the antibiotics are not efficiently removed in conventional wastewater treatment plants, being necessary to implement efficient and low-cost treatment alternatives. The evaluation of the removal of the antibiotic florfenicol was carried out using pilot horizontal subsurface flow wetlands, with a hydraulic retention time of 4.2 d, planted with macrophytes (Phragmites australis) and using concentrations of 10, 15, 20 and 25 mg/L of florfenicol. It was concluded that the removal of the antibiotic and the COD was decreasing over time, with a maximum removal percentage of 77.9% of florfenicol and 85.2% of COD during the first days of exposure. The results found allowed to demonstrate that florfenicol was not retained in the granular material of the wetlands, even in the macrophytes and that the predominant removal mechanism was biological degradation.

Resilience of Micropollutant and Biological Effect Removal in an Aerated Horizontal Flow Treatment Wetland

The performance of an aerated horizontal subsurface flow treatment wetland was investigated before, during and after a simulated aeration failure. Conventional wastewater parameters (e.g., carbonaceous biological oxygen demand, total nitrogen, and Escherichia coli) as well as selected micropollutants (caffeine, ibuprofen, naproxen, benzotriazole, diclofenac, acesulfame, and carbamazepine) were investigated. Furthermore, the removal of biological effects was investigated using in vitro bioassays. The six bioassays selected covered environmentally relevant endpoints (indicative of activation of aryl hydrocarbon receptor, AhR; binding to the peroxisome proliferator-activated receptor gamma, PPARγ; activation of estrogen receptor alpha, ERα; activation of glucocorticoid receptor, GR; oxidative stress response, AREc32; combined algae test, CAT). During the aeration interruption phase, the water quality deteriorated to a degree comparable to that of a conventional (non-aerated) horizontal subsurface flow wetland. After the end of the aeration interruption, the analytical and biological parameters investigated recovered at different time periods until their initial treatment performance. Treatment efficacy for conventional parameters was recovered within a few days, but no complete recovery of treatment efficacy could be observed for bioassays AhR, AREc32 and CAT in the 21 days following re-start of the aeration system. Furthermore, the removal efficacy along the flow path for most of the chemicals and bioassays recovered as it was observed in the baseline phase. Only for the activation of AhR and AREc32 there was a shift of the internal treatment profile from 12.5% to 25% (AhR) and 50% (AREc32) of the fractional length.

A curve-shift technique for the use of non-conservative organic tracers in constructed wetlands

Understanding the flow behaviour and accounting for time in constructed wetlands is necessary for the modelling and design of these systems. The addition of a tracer into the feed of a horizontal subsurface flow wetland allows the researcher to understand the flow of the fluid through the system, especially if the mass of the tracer is conserved (i.e. the mass of tracer injected is equal to the mass of tracer leaving the system). Conservative tracers, however, may pose a problem when it comes to the disposal of the effluent of the system if they are hazardous to the environment. In this study, the use of benzoate as a non-conservative degradable hydraulic tracer was investigated. The response curve of such a tracer is distorted due to its degradation within the wetland and hence the mass leaving the system is not equal to the mass injected. As a result, the typical hydraulic performance parameters obtained from tracer-response curves cannot be accurately calculated. In this paper, a curve-shift technique was developed by using a benzoate step-change curve as an input and using mathematical techniques to transform it into a conservative tracer-response curve. This was done through establishing a mathematical relationship between the retardation and hydrodynamic dispersion of benzoate and a known conservative tracer, uranine. This methodology was tested by conducting a dual tracer study using both benzoate and uranine and comparing the shifted benzoate response curve with the uranine response curve. Hydraulic parameters including mean residence time, effective volume ratio and hydraulic efficiency for each of these tracers were also compared.

Environmental and Economic Approach to Assess a Horizontal Sub-Surface Flow Wetland in Developing Area

Many urbanized areas in tropical climate regions are coping with water contamination due to inadequate sewage collection, particularly in communities that inhabit marginal land of rapid-growth. Relying on large-scale Waste-Water Treatment Plants -WWTPs and implementation of traditional sewage collection infrastructures have proven limited success to cope with the mentioned problem. Alternatives based on Nature-based Solutions - NbS, have the potential to deliver des-centralized treatment as well as additional socio-environmental benefits for the improvement of urban poor conditions. This research focused on modelling cost-efficiency and environmental performance of Nb-S implemented in fast-growing urban areas of the developing countries. A Horizontal Sub-Surface Flow Constructed Wetland - HSSF-CW is proposed to perform as complementary cost-effective decentralized treatment of local sewage. P-K-C* model is applied as sizing approach of the system for a 60% minimum removal of Biological Oxygen Demand - BOD in the influent. Cost-Benefit Analysis (CBA) has been used to analyse the feasibility of the CW proposal with environmental performance of CW modelled through shadow prices methodology. Shadow prices of contaminants, i.e. phosphorus, nitrogen and BOD, act as a proxy of environmental benefit in monetary units, allowing to include the environmental performance of CW into CBA. This new method combines both P-K-C* sizing approach and environmental performance through shadow prices to enhance best allocation of resources for water treatment.

Isolation of Cultivable Bacteria Associated with the Root of Typha latifolia in a Constructed Wetland for the Removal of Diclofenac or Naproxen

In this work, we designed at the level of microscale, subsurface flow wetlands planted with Typha latifolia, and used to remove diclofenac and naproxen from solutions that contained them. The wetlands were operated for 105 days with a hydraulic residence time (TRH) of 5 days. In these conditions, the removal efficiencies for diclofenac and naproxen were 98.4% and 97.7%, respectively. Moreover, we identified cultivable bacteria associated with the roots of plants exposed to either diclofenac or naproxen. We obtained 898 isolates that clustered in 9 morphotypes from the roots of Typha latifolia exposed to diclofenac, and 563 isolates grouped in 7 morphotypes, in the case of naproxen. All isolates were identified by 16S ribosomal sequencing. The BLASTn analysis indicated that 16 morphotypes showed an identity higher than 95% with the 16S rDNA gene of bacteria belonging to the genus Pseudomonas. Biochemical characterization based on plant growth-promoting activities suggests that bacteria contribute to plant growth in the wetland conditions. The results indicate that Typha latifolia and bacteria associated with their roots removed diclofenac and naproxen in subsurface flow wetlands.

Selection of macrophytes and substrates to be used in horizontal subsurface flow wetlands for the treatment of a cheese factory wastewater

The aims of this study were to select the most suitable macrophyte species and substrate to be used in horizontal subsurface flow (HSSF) wetlands for the treatment of a local cheese factory wastewater, and to quantify the influence of plant species and substrates by applying of a simple first-order kinetic model. Microcosms-scale HSSF wetlands were planted with Canna glauca or Typha domingensis. LECA and river stones were used as substrates. Both studied macrophytes showed a high tolerance to the treated wastewater. HSSF wetlands were efficient for the treatment of diluted cheese production wastewater. COD, TP, NH4+-N and TN showed high removal efficiencies in all the HSSF wetlands. HSSF wetlands planted with C. glauca showed the best performance for removal of NH4+-N. The highest SRP removal was obtained in HSSF wetlands planted C. glauca with LECA as substrate. A simple first-order kinetics model was applied. The fitted parameters of the modified first-order model k-C* allowed to demonstrate the effect of the plants in the treatment of the effluent. HSSF wetlands planted with C. glauca using river stones were the systems that showed the fastest TIN removal. According to the obtained results, it is proposed to use C. glauca and river stones as substrate in a HSSF wetland for the treatment of this wastewater. The present study provides useful data to design a wetland at a larger scale.

Perfluoroalkyl substances in the Lingang hybrid constructed wetland, Tianjin, China: occurrence, distribution characteristics, and ecological risks.

In this study, the occurrence, spatial distribution, sources, and ecological risks of perfluoroalkyl substances (PFASs) in the surface waters of the Lingang hybrid constructed wetland were systematically investigated. Twenty-three PFASs were analyzed from 7 representative sampling zones. The obtained results indicated that PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFBS, PFOS, and HFPO-DA were frequently detected; and PFBA, PFOA, and PFOS were the dominant PFASs with the relative abundances in ranges of 26.91 to 52.26%, 11.79 to 28.79%, and 0 to 31.98%, respectively. The total concentrations of 8 PFASs (Σ8PFASs) ranged from 25.9 to 56.6ng/L, and the highest concentration was observed in subsurface flow wetland. Moreover, HFPO-DA with high toxicity was detected in wetlands for the first time. Based on the principal component analysis-multiple linear regression (PCA-MLR) analysis, three sources and their contributions were fluoropolymer processing aids (67.6%), fluororesin coatings and metal plating (17.9%), and food packaging materials and atmospheric precipitation (14.5%), respectively. According to the risk quotients (RQs), the ecological risk of 8 PFASs was low to the aquatic organisms.

Promoting effects of corn straw and exceed sludge as carbon sources on denitrification of constructed wetlands

As the low C/N ratio of effluent from wastewater treatment plant, the advanced treatment of constructed wetlands (CWs) on the effluent is often unsatisfactory, especially for the removal of N. In order to increase the N removal efficiency, this paper tested three kinds of carbon sources acid and alkali treated straw, alkali treated straw and exceed sludge for promoting the denitrification of CWs. The results showed that alkali treated straw performed the strongest carbon release ability (0.43mg?g-1?h-1) and the maximum C/N ratio (27.3). While acid and alkali treated straw’s carbon release ability and C/N ratio were 0.37 mg?g-1?h-1 and 12.8, exceed sludge’s carbon release ability and C/N ratio were 0.37 mg?g-1?h-1 and 8.4. In order to improve the C/N ratio in CWs to 5/1, 450g alkali treated straw and exceed sludge were added into tide flow wetlands (TFCWs) and subsurface flow wetlands (SSFWs) respectively to test the improvement of denitrification. Compared with the control groups, the N removal of CWs with carbon sources were significantly improved. CWs with alkali treated straw showed better removal effects of N than CWs exceed sludge. The analysis results of the first-order kinetic process suggested that the denitrification rate constants of TFCW control group, TFCW with exceed sludge and TFCW with alkali treated straw were 0.126, 0.262 and 0.345, respectively. The denitrification rate of TFCW with alkali treated straw was 2.74 times of TFCW control group, and 1.32 times of TFCW with excess sludge. This study has contributed to understand the possibility of straw and exceed sludge as the carbon sources to strengthen the denitrification in CWs.

Evaluation of three lignocellulosic wastes as a source of biodegradable carbon for denitrification in treatment wetlands

Lignocellulosic wastes are a good alternative to provide biodegradable carbon in treatment wetlands to promote denitrification, specifically in partially saturated subsurface vertical flow wetlands in which such residues can be added both in the free-drainage zone and in the saturated zone. Although the composition of lignocellulosic wastes is similar (lignin, cellulose and hemicellulose), the rate of releasing biodegradable carbon, recalcitrant compounds, color, etc., could be different. Furthermore, their degradation rate may be different under unsaturated and saturated conditions Therefore, in order to optimize their use in treatment wetlands, the aim of this study was to evaluate three lignocellulosic wastes (corncob, pine wood shavings and agave bagasse) with respect to their capacity to generate biodegradable carbon, as well as the release of recalcitrant compounds, total suspended solids and color, in unsaturated and saturated conditions. It was found that corncob and pine wood shavings were the most suitable wastes to be used as a carbon source in partially saturated subsurface vertical flow wetlands. Corncob released low content of biochemical oxygen demand in unsaturated conditions but high content in saturated conditions, while pine-wood shavings released a moderate-low content in both conditions. In contrast, agave bagasse increased the concentrations of biochemical oxygen demand, chemical oxygen demand, total suspended solids and color in the effluents indicating a very fast degradation, which was confirmed with its weight loss in around 44% in both unsaturated and saturated conditions.

Constructed Wetlands in Latin America and the Caribbean: A Review of Experiences during the Last Decade

The review aims to report the state-of-the-art constructed wetlands (CW) in the Latin America and Caribbean (LAC) region not limited to national and local conditions. The aim is with a broader view, to bring updated and sufficient information, to facilitate the use of the CW technology in the different countries of LAC. Thus, 520 experiences extracted from the 169 reviewed documents in 20 countries were analyzed. According to the data, horizontal subsurface flow wetlands are the most reported CW in the region (62%), the second most common CW technology in the region is free water surface CW (17%), then vertical flow systems (9%), followed by intensified constructed wetlands (8%), and finally French systems (4%). The performance for nutrient removal is analyzed, finding that the mean of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorous (TP) removal efficiencies varies from 65% to 83%, 55% to 72%, and 30% to 84%, respectively. The results suggest a generally good performance for COD and TN removal, but a low performance for TP removal. Regarding plant species used for CWs, 114 different plant species were reported, being until now the most extensive report about plant species used in CWs in the LAC region.

Study on Domestic Wastewater Treatment of the Horizontal Subsurface Flow Wetlands (HSSF-CWs) Using Brachiaria mutica

This study aimed to evaluate the effect of domestic wastewater treatment on the horizontal subsurface flow-constructed wetlands (HSSF-CWs) using Brachiaria mutica vegetation. We used two wetland models: one with plants and the other without plants. These models were built according to the following dimensions (L × W × H = 1.2 × 0.4 × 0.8 m) and operated at four organic loads (30, 60, 90, 120 kg COD/ha.day) for 3 months. Parameters including pH, COD, BOD5, TSS, total nitrogen (TN), total phosphorus (TP), total coliforms were analyzed. The levels of pollutants in domestic wastewater after treatment were significantly reduced. The values of percentage removal (%) were as follows: COD 81.58%, BOD5 93.3%, TSS 67.2%, TN 58.6%, TP 85.5%, and total coliforms 90.4%. Our results also indicate that the organic loading rate (OLR) ranging between 60 and 120 kg COD/ha.day is suitable to be implemented in the actual domestic wastewater treatment.

Application of integrated local plant species and vesicular basalt rock for the treatment of chromium in tannery wastewater in a horizontal subsurface flow wetland system

In this study, integrated local plant species and vesicular basalt were used in the constructed units with a horizontal subsurface flow wetland system to investigate the removal efficiency of chromium in tannery wastewater. Four pilot units were vegetated with Pennisetum purpureum, Typha domingensis, Cyprus latifolius, and Echinochloa pyramidalis, and a fifth unit was left unvegetated (control). The constructed wetland units vegetated with P. purpureum and C. latifolius were effective in removing chromium up to 99.38 % and 99.21 % respectively in the 6 days of hydraulic retention time. All the constructed wetland units were effective in removing chromium from the tannery wastewater and there was no statistically significant difference between the vegetated and control units. The plant species used for removal of Cr (III) indicated bioconcentration factor >1 and translocation factor <1. Based on its rapid growth and biomass production, P. purpureum can accumulate more Cr (III) in its above-ground parts compared to the other three plant species. The integrated horizontal subsurface flow wetland units indicated high treatment potential of chromium (III) in the tannery wastewater, which is below the standard discharge limit set to surface water bodies (2 mg L−1) according to Ethiopia EPA.

Purification Effect of Sequential Constructed Wetland for the Polluted Water in Urban River

Constructed wetlands can play an active role in improving the water quality of urban rivers. In this study, a sequential series system of the floating-bed constructed wetland (FBCW), horizontal subsurface flow constructed wetland (HSFCW), and surface flow constructed wetland (SFCW) were constructed for the urban river treatment in the cold regions of North China, which gave full play to the combined advantages. In the Yitong River, the designed capacity and the hydraulic loading of the system was 100 m3/d and 0.10 m3/m2d, respectively. The hydraulic retention time was approximately 72 h. The monitoring results, from April to October in 2016, showed the multiple wetland ecosystem could effectively remove chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphate (TP), and suspended solids (SS) at average removal rates of 74.79%, 80.90%, 71.12%, 78.44%, and 91.90%, respectively. The removal rate of SS in floating-bed wetland was the largest among all the indicators (80.24%), which could prevent the block of sub-surface flow wetland effectively. The sub-surface flow wetland could remove the NH4-N, TN, and TP effectively, and the contribution rates were 79.20%, 64.64%, and 81.71%, respectively. The surface flow wetland could further purify the TN and the removal rate of TN could reach 23%. The total investment of this ecological engineering was $12,000. The construction cost and the operation cost were $120 and $0.02 per ton of polluted water, which was about 1/3 to 1/5 and 1/6 to 1/3 of the conventional sewage treatment, respectively. The results of this study provide a technical demonstration of the restoration of polluted water in urban rivers in northern China.

Nutrient Leaching from Green Waste Compost Addition to Stormwater Submerged Gravel Wetland Mesocosms

AbstractSubmerged gravel wetlands (SGWs) are subsurface-flow wetlands that can act as effective stormwater control measures (SCMs). To investigate SGW nitrogen (N) and phosphorus (P) performance an...

Nitrogen Removal in Woodchip‐based Biofilters of Variable Designs Treating Agricultural Drainage Discharges

Subsurface flow wetlands with a woodchip‐based biofilter are known to act as effective measures in mitigating site‐specific nutrient losses in agricultural drainage. To optimize operation, the combined effect of water temperature, hydraulic residence time (HRT), and filter design is fundamental. This 2‐yr study evaluated a combination of three flow designs and two woodchips mixtures at a test facility receiving agricultural drainage discharge from a 78‐ha catchment. The biofilter test facility consisted of six independent parallel‐constructed wetlands (CW1–CW6), with two types of filter mixtures and three different hydraulic designs (horizontal, vertical upward, and vertical downward flow). Horizontal CWs performed best with an annual removal of total N (TN) amounting to 53 to 54% of the load, corresponding to a daily removal of 2.16 to 2.32 g N m−3d−1. Removal by the vertical CWs amounted to 38 to 60% of the TN load or 1.19 to 2.31 g N m−3d−1. Despite low temperatures and HRT down to 3 h, all CWs functioned well in winter with 20 to 30% N removal. In contrast, during summer when the hydraulic load was low and HRT was up to &gt;96 h, N removal was ∼100%, and the reduction sequence proceeded with sulfate reduction and formation of H2S. Statistical analysis and model development revealed that the percentage removal of both TN and nitrate N was mostly dependent on water temperature and HRT, explaining 81.7 to 91.1 and 83.5 to 89.5% of the variation, respectively.Core IdeasThe hydraulic design influences seasonal and annual N removal efficiency.Water temperature and hydraulic residence time control N removal efficiency.Operational models can be used for dimensioning biofilters for N removal efficiency.

Fractal analysis in rural domestic wastewater quality under dissolved oxygen stability in wetlands planted with Chrysopogon zizanioides

Chrysopogon zizanioides is a plant with adaptability characteristics in a variety of soils and climatic conditions, improves quality of wastewater and industrial water, due to the root system, allows the consumption of organic matter and capture pollutants. One of the water quality indicators is the amount of dissolved oxygen present. To analyze the recovery behavior of dissolved oxygen in wastewater, an artificial subsurface flow wetland was designed with stone as a filter material with dimensions 0.9 m wide, 2.5 m long and 0.60 m deep and 30 Vetiver plants. These dimensions and quantity of plants were considered appropriate in terms of space and low cost in order to replicate in rural and semi-urban areas, because in some of these they do not have an appropriate aqueduct, then this strategy becomes an option for people residing in these places. The water treated in this wetland is domestic wastewater from a rural house in the municipality of Floridablanca, Colombia. For 4 weeks the data of the dissolved oxygen present in said water was recorded using a multiparameter probe, to observe how effective the process is in a shorter time and using fractal dimension the volatility of this time series was observed.

Innovative Effluent Capture and Evacuation Device that Increases COD Removal Efficiency in Subsurface Flow Wetlands

The objective of this work is to evaluate the impact of innovative modifications made to conventional effluent capture and discharge devices used in subsurface flow wetlands (SSFW). The main modifications that have been developed extend the influence of the capture and discharge device in such a way that the SSFW width and height are fully covered. This improved innovative device was applied and evaluated in two subsurface flow wetlands, one on a pilot scale and one on a real scale. To evaluate the impact of the innovative device with respect to the conventional one in the operational functioning of subsurface flow wetlands, the elimination of chemical oxygen demand (COD) was measured and compared. The results show that for the innovative device, the COD removal was 10% higher than for the conventional device, confirming the validity and effectiveness of the modifications implemented in the effluent capture and discharge devices used in SSFW.

Performance of Subsurface Flow Constructed Wetland Systems in the Treatment of Al-Rustumia Municipal Wastewater using Continuous Loading Feed

This study aimed at comparing the performance of vertical, horizontal and hybrid subsurface flow systems in secondary treatment for the effluent wastewater from the primary basins at Al-Rustumia wastewater treatment plant, Baghdad, Iraq. The treatments were monitored for six weeks while the testsduration were from 4 to 12 September 2018 under continuous wastewater feeding for chemical oxygen demand (COD), total suspended solid (TSS),ammonia-nitrogen(NH4-N) and phosphate (PO4-P) in comparison with FAO and USEPA standards for effluent discharge to evaluate the suitability of treated water for irrigation purposes. Among the systems planted with Phragmites Australia, the hybrid subsurface flow system which consisted of vertical unit followed by horizontal one, considerably removed the pollutants more efficiently than the single operated systems. The planted hybrid subsurface flow wetland system was achieved the highest removal with a mean removal rate of COD,TSS, NH4-N, and PO4-Pat 99.3, 83.2,67.4 and 53% respectively and these percentages were decreased in the other systems. The results proved that the planted vertical subsurface flow unit can be removed the COD, TSS, NH4-N and PO4-Pwith values of 93, 71.1, 43.3 and 30.7%, respectively while the achieved removals by horizontal subsurface flow unit of 99, 74.3, 54.5 and 20.3%, respectively. The planted horizontal subsurface flow wetland, however, showed a good efficacy for all parameters in the treatment process except for PO4-P when it is compared with vertical system, however, there is a clear increase in the NO3-N effluent concentration for all treatment units.

Spatial distribution behavior of basic pollutants in a subsurface-Flow wetland with thalia geniculata

Spatial distribution behavior of basic pollutants in a subsurface-Flow wetland with <i>thalia geniculata</i>

Bioreactor and wetland combinations

Wastewater treatment plants combining bioreactors and natural processes, designed to achievecost efficient treatment, are described and evaluated. The plants have a common generallayout: an anaerobic pretreatment, an aerated bioreactor, sedimentation with sludge return anda final sub-surface flow wetland treatment. Variations in this design, adaptations to variousapplications, process control strategies and sludge handling are discussed. Removalefficiencies obtained varies in the range: 96-99 % BOO7, 72-88 % COD, 92-96 % SS, 80-99% P, 37-91% N, where more advanced control yield higher efficiency. Thermo-tolerant fecalcoliform bacteria are typically removed by 99.9 %. Most of the nitrogen is removed in thebioreactors. Computer controlled aeration and sludge handling is required to obtain the hightotal nitrogen removal (&gt; 80 %) Phosphorus can also be removed in the bioreactors andexported as sludge, or, more cost effectively, mainly removed in the wetland part of the plants.The cost efficiency of such treatment plants is good compared to alternative solutions.