Surface Flow Wetland Research Articles

A Comparative Performance Assessment of the Integrated Upflow and Surface Flow-Based Constructed Wetlands Dosed with Landfill Leachate: Electrode Coupling and Input Load Variation

This study reports organic, nutrient, and coliform removal performances of two integrated wetlands designed to treat landfill leachate. Each integrated system included two components: a normal or electrode-integrated upflow-based wetland and a surface flow wetland (with internal baffle walls). The components were fully or partially filled with stone dust media and planted with Canna indica. Two hydraulic loading rates, i.e., 15 L and 60 L (per day), were applied. The integrated wetlands achieved a mean biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and coliform removal efficiency ranges of 89–94%, 95–97%, 85–91%, 91–98%, and 70–88%, respectively, within the applied loading ranges. The electrode-dependent system achieved better pollutant removal performances due to the influence of electrochemical-based bioreactions that fostered microbial decomposition. Nitrogen accumulation percentage (with respect to observed removal) in plant tissues ranged between 0.6 and 25%; phosphorus accumulation percentage was negligible, i.e., ≤0.009%. The chemical composition of the stone dust media supported nutrient adsorption. Stable nutrient removal performance was observed with both systems despite variable loading ranges due to pollutant removal in the upflow-based wetlands followed by controlled flow direction (induced by baffle walls) in the surface flow wetlands that triggered chemical and biological removals. Mean power density production ranged between 235 and 946 mW/m3 with the electrode-based integrated wetland system. In summary, this study demonstrates the application of integrated wetland systems to treat landfill leachate and the associated factors to achieve stable removal under variable loading ranges.

Promoting Aquatic Health in Constructed Wetlands: Removal of Pathogens and Nitrogen

Due to urbanization and population growth, freshwater resources have become a long-term concern for most developing countries. With the growth of population, the demand for fresh water is increasing and the requirement for sewage treatment is also increasing. In recent years, the demand for sewage recycling has increased sharply. Constructed wetlands (CWs) are an effective sewage treatment system with low energy consumption, minimal maintenance requirements, and a low operation cost, which will meet the current demand for the removal of nutrients and pathogens. The application of CWs in sewage treatment has attracted more and more attention because it is also a nature-based solution (NbS). These systems are capable of removing not only nitrogen (N) and phosphorus (P), but also pathogen indicators, such as fecal coliform and Escherichia coli. The presence of these indicators also suggests the influx of other pathogens into aquatic systems, thereby threatening aquatic ecological health. However, research on the removal of pathogens in CWs is relatively scare and their removal mechanisms are not fully understood. Despite their widespread application, the role of plants in CWs, particularly in the specific mechanism of pathogens and nitrogen removal, remains largely unknown. This article will help us to better understand this technology and provide help for our further research. In this paper, the coupled denitrification mechanism between microorganisms and plants in the process of nitrogen transformation was discussed. Plants affect nitrogen transformation microorganisms by releasing oxygen and secretions from their roots and provide substrates for bioremediation. The removal effects of different types of CWs on pathogen and nitrogen species were also summarized. Overall, the removal effect of subsurface flow wetlands outperforms that of surface flow wetlands, with multi-stage wetland systems being the most effective. The main factors affecting the removal of pathogens and nitrogen species in CWs include plants, substrates, operating parameters, UV radiation, temperature, water composition, and pH. Finally, the research frontiers on the removal of pathogens in CWs were prospected.

Development and testing of a mechanistic model for wetland treatment of neutral and polar organic contaminants in oil sands process-affected water

A mechanistic model of the fate of neutral and polar organic contaminants in a free water surface flow wetland was developed to assess the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids (O2-NAs), which are chemicals primarily responsible for oil sands process-affected water (OSPW) toxicity. The model simulates wetland mechanisms of chemical removal based on physicochemical properties, environmental conditions, and wetland design and operation. Good agreement between model estimated and observed concentrations of PAHs and O2-NAs in OSPW in the Kearl Treatment Wetland (Alberta, Canada) was observed over time. Model simulations indicate that the removal of PAHs and O2-NAs from OSPW is highly sensitive to biotransformation rates and that sustained wetland treatment is feasible with robust PAH and NA degrading microbial communities in the wetland. Wetland treatment efficiency is greatest for substances with a log KOW or log D between 3.0 and 5.5 whereas substances with a log KOW or log D >6.0 are not suitable for wetland treatment, even if they can be biodegraded. The log KOW of PAHs and log D for O2-NAs range from 0.7 to 6.7 suggesting most organic contaminants in OSPW are suitable for wetland treatment. Chemical removal via evapotranspiration is not significant pathway of chemical removal from wetlands for PAHs and O2-NAs due to their very low log KAW (less than −1.6). The treatment wetland model presented is the first model to evaluate the fate of both neutral and polar organic contaminants in a flow-through treatment wetland operation, making it a helpful tool to assess the feasibility of these treatment systems for the oil sands industry. The model is particularly useful in evaluating chemical removal efficiency of OSPW contaminants, whether specific water quality objectives can be achieved after treatment, and to assess trade-offs in wetland design and operation to balance treatment performance with design and operational features.

Wetland water quality assessment of eco-engineered landscaping practices: a case study of constructed wetland parks in Hangzhou

Abstract Urban constructed water quality treatment (WQT) wetlands are often applied to be integrated with ecological engineered landscaping (EEL) measures for wastewater treatments. This study aims to identify the interrelationships between the hydrological factors and pollutant removal contributions of typical WQT wetlands at each WQT stage, i.e., subsurface flow wetlands (SSF), vertical flow wetlands (VF), free surface flow wetland (FSF), floating wetland island (FWI), aeration ponds (APs), and ornamental ponds (OPs) in four typical wetland parks in Hangzhou, China. Water quality indices (WQIs) of wetland parks have been monitored. Interactive comparisons and correlations between hydrological indicators and WQIs (i.e., pH, DO, NH3-N, CODCr, and TP) are developed, while the removal contribution of each WQI was explained. It is found that each stage had heterogeneous effects on wastewater treatment due to various geo-ecological factors, including hydraulic conditions, plant type, and microbial microenvironment, whereas the temperature of waterbodies affected WQT performances at full sites in all seasons. Three corresponding EEL guiding principles were derived, i.e., optimising the EEL measures, adapting planting methods, and incorporating multifunctional design and adaptive management. The findings will be helpful for improving the efficacy of WQT stages as one of the potential ecosystem services provided by wetland parks.

The fate of microplastics from municipal wastewater in a surface flow treatment wetland

Microplastics (MPs) are an anthropogenic pollutant of emerging concern prominent in both raw and treated municipal wastewater as well as urban and agricultural run-off. There is a critical need for the mitigation of both point- and diffuse sources, with treatment wetlands a possible sustainable nature-based solution. In this study, the possible retention of MPs in treatment wetlands of the widely used surface flow (SF) type was investigated. In- and outflow water, as well as atmospheric deposition, at a full-scale reed-based SF wetland (operating as a polishing phase of municipal wastewater treatment) was analyzed for MPs in a size range of 25–1000 μm. FPA-based μFT-IR spectroscopic imaging was used in combination with automated data analysis software, allowing for an unbiased assessment of MP numbers, polymer types and size distribution.Inflow water samples (secondary treated wastewater) contained 104 MPs m−3 and 56 MPs m−3 in sampling campaigns 1 and 2, respectively. Passage through the SF wetland increased the MP concentration in the water by 92 % during a rain intense period (campaign 1) and by 43 % during a low precipitation period (campaign 2). The MP particle numbers, size and polymer type distribution varied between the two sampling campaigns, making conclusions around the fate of specific types of MPs in SF wetlands difficult.Atmospheric deposition was measured to be 590 MPs m−2 week−1 during the rain-intense period. Our findings point towards atmospheric deposited MPs as an important factor in the fate of MPs in SF wetlands, causing an increase of MP concentrations, and potentially explaining the variations observed in MP concentrations in wetland effluent and removal efficiency. Furthermore, atmospheric deposition might also be a reason for the considerable inter-study variation regarding MPs removal efficiency in SF wetlands found in the available literature.

Efficacy of an off-line constructed wetland for mitigating nitrogen loss from a pastoral catchment

ABSTRACT Constructed wetlands are an established mitigation option for reducing contaminant loads from pastoral land in New Zealand. We assess the long-term performance of a 0.5 ha, off-line, horizontal surface flow wetland, installed on a dairy farm with the primary objective of nitrate removal. Over seven years the median removal rates for nitrate-nitrogen (NO3–N), total nitrogen and total suspended solids were 45%, 33% and 74%, respectively. Whilst dissolved reactive phosphorus (DRP) was initially removed, over time the wetland progressed to a small exporter of DRP. Median NO3–N mass removal was 417 kg yr−1 , which is considerable for such a small wetland, and equivalent to 7% of total modelled ‘farm-scale’ losses. Nitrate removal was found to be seasonal and although it could be simulated using a conventional wetland model with Arrhenius temperature dependence, the resulting joint estimates of k 20 and Θ were uncertain. We estimate the NO3–N removal cost-effectiveness of the wetland (over a 25-year lifespan) to be NZ$34 kg N−1. We foresee opportunities for off-line constructed treatment wetlands to be an effective nitrate mitigation option in perennial drains and lowland streams in pastoral catchments, but also emphasise the need for on-going maintenance to ensure longevity of performance.

Removal characteristics of microplastics in sewage flowing through a long-term operation surface flow wetland

Microplastics (MPs) in sewage pose significant threats to aquatic system. Surface flow wetland (SFW) is a common natural wetland type, and is also used as a cheap and easy-to-build sewage treatment system for small and scattered settlements. However, seasonal variation patterns of MPs in sewage removed by SFW are still limited. Therefore, a field investigation was conducted in an SFW that has been operated for 17 years. The concentration of microplastics in the influent of the SFW (CMPs, in) ranged from 56 ± 6 to 250 ± 14 items L−1. The dominant plastic types were fibers and polyethylene terephthalate (PET). CMPs, in were high in summer and winter, significantly related to the seasonal dressing habits. The removal efficiencies of MPs in SFW were 48.03–92.32 % in different seasons, and the mechanisms of MP removal were different with traditional pollutants. Before flowing out occasionally or by heavy precipitation, MPs were primarily trapped in the SFW and underwent certain oxidation. Simulation experiments demonstrated that 47.5–92.9 % of MPs would be trapped in the SFW, and plants would significantly enhance the trapping capacities. This study sheds light on the seasonal variation characteristics and patterns of MPs in actual sewage, and clarifies the fate of MPs in a long-term operation SFW.

Aquatic plant root exudates: A source of disinfection byproduct precursors in constructed wetlands

Aquatic plant-derived dissolved organic matter (DOM) in water bodies is an important source of disinfection byproduct (DBP) precursors. It is therefore very important to investigate DBP formation, and the main DBP precursors that enter drinking water during treatment processes. In this study, Lythrum salicaria root extract (LSRE) and Acorus calamus root extract (ACRE) were analyzed. The LSRE and ACRE were chlorinated and disinfected to generate trihalomethanes, haloacetic acids, haloketones, and haloacetaldehydes. The DBP formation potential of LSRE, dominated by humus, was higher than that of Suwannee River natural organic matter (SRNOM), and trichloroacetic acid was the main DBP. It was calculated that 2.09 % of the increased DOC brought by the surface flow wetland planted with emergent aquatic plants, and the contribution rates of TCMFP, DCAAFP and TCAAFP in effluent were 3.34 %, 3.23 % and 3.05 %, respectively. A total of 706 chlorinated-formula were detected by FTICR-MS, among which mono- and di-chlorinated formulae were the most abundant. Macromolecular hydrophobic organics and tannins were the main precursors for LSRE. Unlike LSRE, the DOM composition of ACRE was dominated by protein or aliphatic compounds; therefore, the risk of DBP formation was not as high as that for LSRE. This study is the first to determine the risk of DBP formation associated with aquatic plant root extracts, and confirmed that tannins in plant-derived DOM are more important DBP precursors than lignins.

‘Dual Purpose’ Surface Flow Constructed Treatment Wetlands Support Native Biodiversity in Intensified Agricultural Landscapes

In agricultural landscapes, free-water surface flow wetlands (FWS) are constructed mainly to improve water quality; however, their contribution to biodiversity conservation is increasingly recognised. To inform biodiversity management in FWS treating agricultural runoff, we surveyed the vegetation and fauna assemblages in five established FWS in a lowland, pastoral landscape in the central North Island, New Zealand. The FWS had been established for between 3 and 19 years, planted with a restricted range of native plant species, and fenced to exclude livestock access. Larger wetlands hosted significantly more plant and mammal species. However, other than wetland size, we found few other significant relationships between wetland habitat, landscape characteristics, and measures of biodiversity (total species, proportion of native species, number of wetland specialists, or threatened species). We recorded one-hundred and thirteen plant, twenty bird, five mammal, eighty-five terrestrial invertebrates, forty-seven aquatic invertebrates, six fish, and two amphibian species inhabiting the FWS. Native species comprised 96% of the total aquatic invertebrate fauna identified. For other taxa, native flora and fauna accounted for half or less than half of all species identified: 53% terrestrial invertebrates, 50% fish, 45% birds, 32% plants, and 0% amphibian and mammal species. Few wetland specialists (aquatic or wetland-adapted) or threatened native species were detected, probably reflecting the limited range of wetland plant species in initial plantings and the difficulties native taxa face when colonising new habitat where potential reservoirs of colonist species are also depauperate or too distant. FWS support native biodiversity, but further enhancements may require active management of exotic and pest species to minimise competition or predation on native species.

Comparative analysis of greywater pollutant removal efficiency with horizontal free water surface flow wetland with other wetland technologies

The reuse of treated wastewater for agriculture and other purposes is globally recognized as a reliable water source. Constructed wetlands are cost-effective and reliable green technologies for wastewater treatment, offering an environmentally friendly and affordable solution with minimal operational and maintenance requirements. This study assessed four wetland technologies (HFWSF, VFSF, VSSF, and HSSF) for treating greywater according to regulatory standards. The technologies effectively maintained pH levels, and both treated and untreated greywater samples met FEPA limits. They efficiently reduced dissolved and suspended particles, remaining below FEPA discharge limits for conductivity, TDS, turbidity, and TSS. However, elevated ammonia levels in both treated and untreated samples required additional treatment or mitigation. Sulphate levels were successfully mitigated, and phosphorus limits were met, with HFWSF already compliant even before treatment. Nitrate levels were reduced to meet FEPA limits, ensuring regulatory compliance. While BOD limits were met in both treated and untreated samples, untreated samples exceeded COD limits, necessitating more efficient treatment methods. HFWSF and HSSF complied with COD limits, whereas VFSF and VSSF did not. Both treated and untreated samples exceeded FEPA limits for oil and grease, indicating the need for additional treatment. Untreated samples exhibited high coliform contamination levels, underscoring the importance of effective treatment. However, all technologies successfully reduced coliform levels in treated samples, meeting FEPA limits and confirming treatment effectiveness. The combination of Typha (Domingensis) in the horizontal subsurface flow constructed wetland improved pollutant removal, nutrient removal, and contaminant elimination. Incorporating water Hyacinth (Eichhornia crassipes) with horizontal free water surface flow wetland technology demonstrated the highest efficacy in removing various pollutants. This combination outperformed other wetland technologies in effectively removing pollutants, including ammonia (60%), oil and grease (78.46%), COD (85%), TP (37.04%), FC (75%), and TC (79.59%), representing significant progress in greywater treatment.

The effects of cold frozen conditions on nitrogen removal and transformation in wetlands purifying wastewater: Insights from combined full- and pilot-scale observations

In wastewater treatment, wetlands are regarded as cost-efficient and sustainable purification systems. Currently, different types of wetland are used for year-round treatment of municipal wastewater (the polishing step after the secondary or tertiary units) in cold climate regions. However, there is a lack of understanding regarding the effect of freezing cold conditions on pollutant removal processes, in particular regarding those linked to nitrogen cycling. This study evaluated the effect of cold winter conditions on contaminant removal, with a focus on nitrogen transformation and removal in a pond-type surface flow wetland with reed (Reed-SF) and a peat-based horizontal subsurface flow (Peat-HSSF) wetland. Year-round full-scale wetland monitoring was complemented with pilot-scale laboratory experiments, which allowed to follow the cold-climate induced effects on contaminant removal and nitrogen processes, along with other water quality, environmental, and microbial parameters. Overall, it was observed that the effect of cold climate conditions on nitrogen removal was dependent on the wetland type in combination with the quality of the inflow water. When treating ammonium (NH4) rich wastewater, removal of total nitrogen (Ntot), as well as NH4, was higher in the Peat-HSSF than in the Reed-SF wetland. Under frozen conditions, NH4 removal decreased slightly but remained positive in the pilot Peat-HSSF, whereas it declined and even turned into leaching in the pilot Reed-SF wetland. Conditions encountered in the Peat-HSSF wetlands (high abundances of active nitrifying bacteria, high levels of dissolved oxygen (DO) and redox potential) supported nitrification, which continued under cold conditions. Whereas in the Reed-SF, a low abundance of active nitrifying bacteria was found, especially in the water column under frozen conditions. DO here was low and decreased in cold conditions with ice cover.

Development of a novel sizing approach for passive mine water treatment systems based on ferric iron sedimentation kinetics

The removal of dissolved and particulate iron (Fe) from contaminated mine drainage is an omnipresent challenge in, and legacy of, the mining industry worldwide. The sizing of settling ponds and surface-flow wetlands for passive Fe removal from circumneutral, ferruginous mine water is based either on a linear (concentration-independent) area-adjusted removal rate or flat assignment of an experience-based retention time, neither of which reflects the underlying Fe removal kinetics. In this study, we evaluated the Fe removal performance of a pilot-scale passive system operating in three identical, parallel lines for treatment of mining-influenced, ferruginous seepage water to determine and parameterise a robust, application-orientated model approach for sizing of settling ponds and surface-flow wetlands, each. By systematically varying flow rates (and thus residence time), we were able to demonstrate that the sedimentation-driven removal of particulate hydrous ferric oxides in settling ponds may be approximated by a simplified first-order approach at low to moderate Fe levels. The first-order coefficient was found in the order of 2.1(±0.7) × 10−2 h−1, which corresponds well with previous laboratory studies. The sedimentation kinetics may be combined with the preceding Fe(II) oxidation kinetics to estimate the required residence time for pre-treatment of ferruginous mine water in settling ponds. In contrast, Fe removal in surface-flow wetlands is more complex due to the phytologic component, which is why we advanced the established area-adjusted Fe removal approach by parameterising the underlying concentration-dependency for polishing of pre-treated mine water. The quantitative results of this study provide a novel, conservative approach for customised sizing of settling ponds and wetlands in integrated passive mine water treatment systems.

Management proposal of a naturally occurring wetland modeled as a constructed wetland

Environmental management and restoration aim to accelerate the recovery of ecosystems that have been affected by human activities. This paper presents the diagnosis and management proposal for the Valsequillo wetland, Puebla, Mexico. The study site is a natural wetland dominated by water hyacinth (Eichhornia crassipes) which performs a biofiltration process by reducing the pollutant load of the water. To increase the efficiency of the wetland, an annual harvest plan is proposed in this work. However, the ideal amount of biomass to harvest is unknown. In order determine the optimal annual harvest plan, this natural wetland was modeled as if it were a surface flow wetland by using the equations described. A total of 48 surface water samples were collected in three different seasons of the year (dry, rainy, and winter) and 34 water quality physicochemical parameters were measured. Additionally, two water quality indices were determined, namely: Overall Index Pollution (OIP) and Heavy Metal Evaluation Index (HEI) to determine the degree of contamination in different zones of the study area. The model results showed that in order to achieve the desired removal of total phosphorus (TP) or chemical oxygen demand (COD), 274 ha or 306 ha of aquatic plants must be harvested, respectively. The results of the modeling showed that this action will optimize the function of the wetland by improving the removal of total suspended solids (TSS, 6%), total nitrogen (TN, 24%) TP (31%), chemical oxygen demand (COD, 11%) and biochemical oxygen demand (BOD5, 101%).

Degradation of sulfonamide antibiotics in the rhizosphere of two dominant plants in Huixian karst wetland, Guangxi, China

Abstract In this work, Phragmites australis and Vallisneria natans were selected as the research objects and were cultured for 10 d under 0.10 μg L−1 sulfadiazine (SD) stress in a simulated surface flow wetland reactor. SD degradation was conducted at pH = 7 and 25 °C for 96 h. Each plant group conformed to the first-order kinetic model of degradation, and the degradation rate increased with time, reaching the maximum at 96 h. At 96 h, the degradation rate of P. australis communities was higher than that of V. natans. SD metabolites showed that the degradation pathways in the plant rhizosphere were mainly hydroxylation, aminolation, and S–N bond cleavage. In the analysis of rhizosphere bacterial community structure, the bacterial phyla that could degrade antibiotics accounted for a large proportion. Compared with before degradation, the dominant phylum and genus did not change after degradation (96 h), but their abundance changed to varying degrees, and new genera appeared in the P. australis group. This research provides a reference for the degradation of antibiotics in karst areas and new information on the mechanism of SA degradation in the plant rhizosphere.

Peat Soil Ecosystem Restoration for Development of a Wetland- a review

Constructed wetlands are sustainable wastewater treatment technology and have been used to treat a variety of wastewaters for decades, including domestic and industrial wastewaters. They take advantage of many of the same processes that occur in natural wetlands but do so in a more controlled or engineered system. To date, surface flow and subsurface flow wetlands are the two main categories of constructed wetland applications. On the other hand, peat soil is the decomposed organic matter that have built up over thousands of years, with high moisture content. Peat soil management is imperative to maintain the mire ecosystem. The use of rhizosphere biodegradation, phyto-stabilization and phyto-accumulation have shown the possibility of improving water quality of wetland associated with peat soil. Thus, the aim of this work is to present a review in the role of constructed wetland system for peat soil management and the water quality as restoration measures of the peat soil ecosystem to promote its suitability for agricultural purpose.

Characteristics of resistome and bacterial community structure in constructed wetland during dormant period: A fullscale study from Annan wetland

As a green technology, constructed wetlands (CWs) can provide a low-cost solution for wastewater treatment. Either as a standalone treatment or integrated with conventional treatment, nutrients, antibiotic resistant bacteria (ARB)/antibiotic resistance genes (ARGs) can be removed by CW efficiently. While, few studies have focused on characteristics of resistome and bacterial community (BC) structure in CW during dormant period. Therefore, in this study, Annan CW (a full-scale hybrid CW) was selected to characterize resistome and BC during dormant period. The profiles of bacteria / ARGs were monitored in combination of shotgun sequencing and metagenomic assembly analysis. And multidrug ARGs are the most abundant in Annan CW, and surface flow wetland had the relatively high ARG diversity and abundance compared with subsurface flow wetland and the front pond. The most dominant phylum in CW is Proteobacteria, while the other dominant phylum in three parts have different order. COD, TP, TN, ARGs, and mobile genetic genes (MGEs) were removed by subsurface flow CW with better performance, but virulent factors (VFs) were removed by surface flow CW with better performance. Based on the spatiotemporal distribution of ARGs, the internal mechanism of ARGs dynamic variation was explored by the redundancy analysis (RDA) and variation partitioning analysis (VPA). BCs, MGEs and environmental factors (EFs) were responsible for 45.6 %, 28.3 % and 15.4 % of the ARGs variations. Among these factors, BCs and MGEs were the major co-drivers impacting the ARG profile, and EFs indirectly influence the ARG profile. This study illustrates the specific functions of ARG risk elimination in different CW components, promotes a better understanding of the efficiency of CWs for the reduction of ARG and ARB, contributing to improve the removal performance of constructed wetlands. And provide management advice to further optimize the operation of CWs during dormant period.

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.

Dissolved organic matter derived from aquatic plants in constructed wetlands: Characteristics and disinfection byproducts formation

Constructed wetlands are used to improve water quality in the drinking water sources, but aquatic plants planted in constructed wetlands may be a source of disinfection by-product (DBP) precursors. This study explored the characteristics of aquatic plant-derived dissolved organic matter (DOM) and DBP formation in micro-polluted raw water treated by constructed wetlands. A simulated surface flow wetland (SSFW) planted with the typical aquatic plants Lythrum salicaria and Acorus calamus was studied. Raw water, control samples, effluent, and Suwannee River natural organic matter (SRNOM) were analyzed. via ultraviolet-visible (UV-Vis) spectroscopy, three-dimensional excitation emission matrix (3D-EEM) fluorescence combined with a parallel factor (PARAFAC) analysis, liquid chromatography-organic carbon detection (LC-OCD), principal component analysis (PCA), and other detection and analysis methods. A DBP formation potential (DBPFP) index was also constructed. Treatment by the SSFW increased the effluent dissolved organic carbon (DOC), UV254, trihalomethane formation potential (THMFP), haloacetic acid formation potential (HAAFP) by 72.2%, 171.4%, 83.7% and 88.6%, respectively. Planting aquatic plants in surface wetlands will negatively affect the water quality of micro-polluted raw water, with the plants being an important source of increased DBP precursors in wetland effluent. The effluent properties were similar to those of SRNOM, and had a higher degree of aromatization and larger molecular weight than raw water. The increased DBP precursors were mainly fulic acid and humus with higher aromatic and molecular weight, which derived from the growth and metabolism of aquatic plants. Humic substances (HS) accounted for the highest proportion of DOM in this study, with the average molecular weight of HS increasing from 648 to 698 g·mol−1 as the DOM content increased. Results from this study are particularly applicable to the establishment of constructed wetlands planted with aquatic plants in the drinking water sources, and the DOM derived from aquatic plants in constructed wetlands may be important precursors in the subsequent water disinfection process.

Passive Treatment of Circumneutral Mine Drainage from the St. Louis Mine Tunnel, Rico CO: Part 3—Horizontal Wetlands Treatment Train Pilot Study

AbstractMine drainage from the St Louis Tunnel (located at the Rico-Argentine Site) is circumneutral most of the year, with spring freshets increasing flow, decreasing pH and increasing metals concentrations. This study was designed to test the performance of a demonstration-scale horizontal wetlands passive treatment train, comprised of a settling basin, surface flow wetland, horizontal-flow anaerobic wetland, aeration channel, and rock drain, during two years of influent water chemistry at a constant 113 L/min (30 gpm) flow rate. Total Zn, Cd, and Mn effluent concentrations met project treatment goals (PTGs) 75, 96.9, and 100% of the time, respectively, and 93.9, 100, and 100% of the time for the dissolved metals. Most PTG exceedances occurred during the freshet events. Most Zn and Cd attenuation was attributed to sulfide precipitation in the anaerobic cell and capture/filtration of suspended ZnS particles in the anaerobic wetland and rock drain. Manganese was attenuated in the aerobic portion of the anaerobic cell (influent transition zone) as Mn oxides and carbonates. Oxidation of Mn occurred in the rock drain as biogenically formed Mn oxides adhered to the rock matrix. Carryover of dissolved sulfides from the anaerobic cell limited the rock drain’s Mn removal efficiency. Low temperatures did not significantly affect biological activity within the system; the effects of seasonal water quality were more important.

Water quality improvement performance of two urban constructed water quality treatment wetland engineering landscaping in Hangzhou, China.

For typical wastewater treatment processes of urban sewage, plants are often noneffective to improve water qualities of lightly polluted domestic sewage, and urban constructed water quality treatment (WQT) wetlands designed with engineering landscape methods are utilized to optimize both water qualities and landscape values in recent years. The research determines the effects of two typical ecological engineering landscaping projects of urban constructed WQT wetlands by analysing their effects of wastewater quality improvements. Differences of water quality indicators (WQI) respectively among different treatment stages of wetlands includes surface flow wetland, vertical flow wetland, floating wetland islands etc., which have been measured and compared. Evaluation of urban constructed WQT wetlands engineering landscaping has been concluded based on comparisons among hydrological indicators and water quality indicators, i.e. pH, DO, NH3-N, CODCr, TP. Removal effects of individual indicators, includes NH3-N, CODCr and TP during different treatment stages have been quantitatively analysed. In accordance with quantitative analysis, benefits and deficiencies of practical landscape design of urban constructed WQT wetlands are concluded. By adapting proper principles in engineering landscaping, environmental and economic benefits can be achieved to create sustainable landscapes of urban constructed WQT wetlands.