Wetland Units Research Articles

Phosphorus and Nitrogen Removal by Saturated Vertical-Flow Constructed Wetlands (SVCWs) Type Micro-Pilot Using Shale from Ivory Coast as a Substrate

This study evaluates the performance of shale from Ivory Coast used as substrate in vertical-flow constructed wetlands in removal of phosphates and nitrogen. The pilot-scale artificial wetland has been duplicated: filter planted with Panicum maximun and unplanted. They were set up outdoors, and fed with a municipal wastewater. The wetlands have been fed with three batches per week (intermittent) over a period of 3 months. During the operation period, the hydraulic residence time (HRT) 52 h was used, while wastewater temperatures varied from about ~33°C. The removal performance of the constructed wetland units was very good, since it reached on an average 98%, 89.4%, 89.4%, 84%, 80%, 84.8% and 92% for TSS, DOC, BOD5, , TKN, TP and respectively. In addition, the vegetation did not demonstrate superior performance to unplanted controls. Therefore, this study focuses on the role of shale in the phosphorus and nitrogen removal from wastewater by constructed wetland.

Hybrid constructed wetlands integrated with microbial fuel cells and reactive bed filter for wastewater treatment and bioelectricity generation.

The present study aimed to develop a pilot-scale integrated system composed of anaerobic biofilter (AF), a floating treatment wetland (FTW) unit, and a vertical flow constructed wetland coupled with a microbial fuel cell (CW-MFC) and a reactive bed filter (RBF) for simultaneously decentralized urban wastewater treatment and bioelectricity generation. The first treatment stage (AF) had 1450 L and two compartments: a settler and a second one filled with plastic conduits. The two CWs (1000 L each) were vegetated with mixed plant species, the first supported in a buoyant expanded polyethylene foam and the second (CW-MFC) filled with pebbles and gravel, whereas the RBF unit was filled with P adsorbent material (light expanded clay aggregate, or LECA) and sand. In the CW-MFC units, 4 pairs of electrode chambers were placed in different spacing. First, both cathode and anode electrodes were composed of graphite sticks and monitored as open circuit. Later, the cathode electrodes were replaced by granular activated carbon (GAC) and monitored as open and closed circuits. The combined system efficiently reduced COD (> 64.65%), BOD5 (81.95%), N-NH3 (93.17%), TP (86.93%), turbidity (94.3%), and total coliforms (removal of three log units). Concerning bioenergy, highest voltage values were obtained with GAC electrodes, reaching up to 557 mV (open circuit) and considerably lower voltage outputs with closed circuit (23.1 mV). Maximum power densities were obtained with 20 cm (0.325 mW/m2) and 30 cm (0.251 mW/m2). Besides the electrode superficial areas, the HRT and the water level may have influenced the voltage values, impacting DO and COD concentrations in the wastewater.

Evaluation of Tannery Wastewater Treatment by Integrating Vesicular Basalt With Local Plant Species in a Constructed Wetland System

Tannery wastewater is composed of a complex mixture of organic and inorganic components from various processes that can critically pollute the environment, especially water bodies if discharged without treatment. In this study, integrated vesicular basalt rock and local plant species were used to establish a horizontal subsurface flow constructed wetland system and to investigate the treatment efficiency of tannery wastewater. Four pilot units were vegetated with P. purpureum, T. domingensis, C. latifolius, and E. pyramidalis, and a fifth unit was left unvegetated (control). The constructed wetland units in horizontal subsurface flow systems were effective in removing total chromium (Cr), chemical oxygen demand (COD), and 5-day biological oxygen demand (BOD5) from the inflow tannery wastewater. The removal efficiency reached up to 99.38, 84.03, and 80.32% for total Cr, COD, and BOD5, respectively, in 6 days of hydraulic retention time (HRT). The removal efficiency of total suspended solid (TSS), total phosphorus (TP), and nitrate (NO3−) of the constructed wetland units reached a maximum of 70.59, 62.32, and 71.23%, respectively. This integrated system was effective for treating tannery wastewater, which is below the Ethiopian surface water standard discharge limit set to BOD5 (200 mg L−1), COD (500 mg L−1), total Cr (2 mg L−1), NO3− (20 mg L−1), TSS (50 mg L−1), and TP (10 mg L−1).

Measuring dam induced alteration in water richness and eco-hydrological deficit in flood plain wetland

Along with wetland loss, the damming effect on hydrological modification in wetland is another less debated and challenging topic, which needs to have urgent attention. The present work intended to investigate the damming effect on the water richness and eco-hydrological condition of the floodplain wetland and its consequent ecological responses in Punarbhaba River Basin of India and Bangladesh. Satellite images derived hydro-period, water presence frequency (WPF), and water depth were generated for developing water richness model in pre (up to 1992) and post dam conditions (1993–2019). The range of variability (RVA) was modelled using time series satellite images based water index or normalized difference water index (NDWI). Based on RVA model, the hydrological failure rate was developed. Depth of water was used for preparing the flow duration curve (FDC) to estimate the eco-hydro-deficit and surplus condition in wetland at spatial scale for pre and post-dam periods. Satellite image based trophic state index models for pre and post dam conditions were constructed to investigate the ecological response of dam on floodplain wetlands. Results of water richness model showed that wetlands area under high wetland water richness zone decreased from 71.83% to 7.65% in the post-dam conditions. Results of hydrological failure rate showed that high failure rate captured 45% of total wetland area in the post-dam period. Results of eco-hydro-deficit exhibited that eco-hydro-deficit areas increased from 11.22% to 52.19% and 35.03%–52.67% respectively in post-dam conditions indicating growing ecological stress. The TSI models showed that most parts of the wetlands were converted from oligotrophic to meso-eutrophic state signifying the qualitative degradation of water and potential ecosystem health. The area under high TSI was observed in the wetland area having eco-hydro-deficit and high hydrological failure rate zones. These characteristics of wetland areas were found at the fringe of wetlands and fragmented smaller wetland units. The study concluded that damming over the Punarbhaba River adversely affected the water security of the floodplain wetlands in terms of modifying the hydrological richness, ecological condition of the wetland habitat, and ecological systems. The findings of the present study could provide a comprehensive research on the monitoring of surface water crisis in the wetlands, which will be the basic foundation to formulate water resource management plans for conservation, management and restoration of wetlands.

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.

Optimized constructed wetlands enhance the removal and reduce the risks of steroid hormones in domestic wastewater

Constructed wetland (CW) has been proved to be a reliable wastewater treatment technology for removal of various contaminants. However, the removal of specific contaminants such as steroid hormones by wetlands without optimized design parameters would be unstable. Here we investigated the removal mechanism of steroid hormones by constructed wetlands, and optimized various design parameters for the removal of these contaminants in wastewater. Four CW systems with different designs (artificial aeration or series wetland unit) were constructed outdoors to treat raw domestic sewage. The results showed that 9 steroid hormones were detected at concentrations from 7.13 ± 0.28 ng/L to 3040 ± 199 ng/L, with their removal rates ranged from 14.7 ± 3.04% to 100% by these CWs. It was also found that enhanced designs including aeration and series wetland unit can effectively improve the removal of steroid hormones. Combined with ecological risk assessment, CW4 (aerated VSSF CW and aerated HSSF CW combination) was the best design for removal of steroid hormones, but CW2 (VSSF CW with artificial aeration) may be better for urban areas with limited space. Based on mass balance calculation, biodegradation played a dominant role in removing steroid hormones by CWs, while substrate adsorption and plant uptake also played a limited role. The findings from this study suggest that CWs can be optimized to better remove steroid hormones in sewage before discharge into receiving environments.

The geomorphology and Late Quaternary sedimentary record of the Salado/Juramento fluvial megafan, Central Andes foreland basin (Chaco Plain, Argentina)

This research provides geomorphological and sedimentary data on the Salado-Juramento fluvial megafan, the second largest megafan (204,747 km2) of the Chaco aggradational plain, generated by the Salado-Juramento River in NE Argentina. It comprises one of the most extensive depositional systems of the Central Andean foreland basin system in South America, also being among the largest megafans on Earth. Despite this, it has not been previously studied from the perspective of its geomorphology, stratigraphy and dynamic evolution. An integrated approach focusing on the analysis of morpho-sedimentary processes, the resulting landforms and the reconstruction of the Late Quaternary evolution is presented here. The applied methods combine geomorphological mapping from remote sensing images analysis, assessment of landforms and processes, and field data. Historical documents were also analysed. Insights into the near sub-surface stratigraphy were obtained from analysis of research boreholes (up to 30 m depth), integrated with groundwater borehole information. The Fluvial Megafan of the Salado-Juramento Geomophological System comprises four geomorphological units: 1) the middle-proximal area of the megafan, 2) the distal area of the megafan, 3) the complex fluvio-aeolian belt of the Golondrinas-Calchaquí, and 4) the present fluvial belt of the Salado. Thirteen geomorphological sub-units were defined and mapped, representing the complexity of sub-environment interactions. Amalgamated braided channel deposits and aggradation lobes with limited floodplain muds are common in the proximal area, while mixed-load, low-energy, narrow, shallow, and sinuous palaeochannels and associated floodplain marsh deposits characterize the distal area, with groundwater discharges and hydromorphic soils. The megafan construction was dominated by short-term sedimentation and channel avulsions to overbank areas. Fan-shaped depositional lobes of the proximal area and sandy channel deposits and sand sheets linked to terminal splays that are covering mud-flat deposits (floodplains, including palaeosols) in the middle area suggest a high-flow regime. Neotectonics favoured subsidence, avulsion, and prolonged flooding events, with high potential of preservation of an extensive Late Quaternary wetland unit, ponds, lakes, soils, and loessic deposits in the distal megafan. Aggradation and progradation patterns have been conditioned by tectonic control regulating the interaction between the megafan and its axial trunk river (Paraná). Furthermore, the Late Quaternary megafan sequences would also have responded to climatic changes, primarily related to strong hydroclimatic seasonality linked to changes in the South American monsoon system strength. Seasonal high sediment load of the formative river linked to the characteristics of the Andean basin (38,000 km2) and its climatic patterns are considered as the main control on megafan dynamics over at least the Upper Quaternary. Morpho-stratigraphical data of the megafan presented here and the first interpretation of its Quaternary evolution is the key to support socio-economic decisions on aquifer exploitation, land uses, and infrastructure planning.

Vegetación de un área polderizada del Río de la Plata en la Ciudad de Buenos Aires: la Reserva Ecológica Ciudad Universitaria - Costanera Norte

Coastal reclamation constitutes a world trend and can result in new ecosystems adapted to the new coastal configuration. In Buenos Aires City, the “Ciudad Universitaria - Costanera Norte” Ecological Reserve (RECU-CN) constitutes one example of the expansion of the coastline in the Río de la Plata sector, carried out in the late 1960s. Given the lack of published works generated systematically that cover the entire area, we set as the objective to describe the RECU-CN vascular plant vegetation. For this, a systematic sampling was carried out in 79 plots of 25 m2, where the coverage of each of the vascular plant species present was registered. We identified 154 taxa, corresponding to 144 species, 123 genus and 58 families, and the total richness was estimated as 238 species. Trees and herbs had the highest coverage of all life forms. Through multivariate analysis, three vegetation units (Wetland, Forest and Grassland with groves) and 10 vascular plant communities were recognized. Vegetation was ordered according to two gradients: one of flood and another of anthropization. From the comparison with the typical plant communities of the region, similarities were found only with those registered in the Wetland unit. Results highlight that both the coexistence of physiognomically diverse vegetation units, as well as the native composition found in the plant communities of the Wetland unit, constitute main conservation values of the protected area.

Enhanced removal of nutrients and heavy metals from domestic-industrial wastewater in an academic campus of Hanoi using modified hybrid constructed wetlands.

Vietnam, like many developing countries, is facing serious water quality issues due to discharging wastewaters without treatment or with improper treatment, which can constitute a potential risk for aquatic ecosystems, food safety and human health. Hybrid constructed wetlands with four substrate layers (HCW) and modified hybrid constructed wetland (MHCW-1 and MHCW-2) with seven substrate layers were designed to evaluate the enhanced treatment capacity for wastewaters. To this end, we carried out an outdoor experiment at the Vietnam Academy of Science and Technology, Vietnam to treat its wastewaters from April to August 2019. All constructed wetland units were planted with reed Phragmites australis and cyperus Cyperus alternifolius; and specifically wetland MHCW-2 was cultured with earthworm Perionys excavates. Results indicated that MHCW-1 and MHCW-2 with seven substrate layers had higher removal efficiencies of NO3 --N, TKN and TP than HCW system. More substrate layers in MHCW-1 and MHCW-2 also resulted in increase of Cu and Pb removal efficiencies, with 73.5%, 79.4%, 71.5% and 67.8%, respectively. Particularly, earthworm addition in MHCW-2 was more efficient in decreasing the concentrations of biochemical oxygen demand (BOD5), with removal efficiency over 70%.

New insights on the combined removal of antibiotics and ARGs in urban wastewater through the use of two configurations of vertical subsurface flow constructed wetlands

The occurrence and removal of 49 antibiotics and 11 selected antibiotic resistance genes (ARGs) were investigated in 2 vertical subsurface flow (VF) constructed wetlands (1.5 m2 each): an unsaturated (UVF) unit and a partially saturated (SVF) unit (0.35 m saturated out of 0.8 m) operating in parallel and treating urban wastewater. Thirteen antibiotics were detected in influent wastewater, 6 of which were present in all samples. The SVF showed statistical significance on the removal of 4 compounds (namely ciprofloxacin, ofloxacin, pipemidic acid and azithromycin), suggesting that the wider range of pH and/or redox conditions of this configuration might promote the microbial degradation of some antibiotics. In contrast, the concentration of the latter (except pipemidic acid) and also clindamycin was higher in the effluent than in the influent of the UVF. Five ARGs were detected in influent wastewater, sul1 and sul2, blaTEM, ermB and qnrS. All of them were detected also in the biofilm of both wetlands, except qnrS. Average removal rates of ARGs showed no statistical differences between both wetland units, and ranged between 46 and 97% for sul1, 33 and 97% for sul2, 9 and 99% for ermB, 18 and 97% for qnrS and 11 and 98% for blaTEM.

Hyperspectral monitoring of a constructed wetland as a tertiary treatment in a wastewater treatment plant

Hyperspectral sensing devices are being increasingly applied in the field of environmental monitoring. High spatial and spectral resolution hyperspectral data are particularly suited for detecting the vegetation health state due to the unique spectral characteristics exhibited by green plants. Wetlands are capable of filtering polluted water, with their functionality strictly related to the health state of the plants bedded out in the lagoon. This paper presents a ground spectroscopy monitoring survey of the vegetation implanted in the constructed wetland unit located in the wastewater treatment plant for domestic sewage of Latina Mare. The measurement campaign was carried out through the collection of hyperspectral data by means of a spectroradiometer. Broadband indices of vegetation were computed from the data acquired to infer the plant health state. For the test case discussed in this contribution, there is a remarkable agreement between data acquired and the observations at the ground. The broadband indices Red Difference Vegetation Index, Simple Ratio and Transformed Vegetation Index make it possible to highlight the vegetation health state in the investigated wetland unit. Removal efficiency of the unit well reflected the values of the indices.

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.

Aquatic vegetation dynamics in two pit lakes related to interannual water level fluctuation

Water regime characteristics have been recognized as critical factors for aquatic vegetation. In this study, we examined changes in aquatic vegetation coverage area in two shallow sub-lakes of Poyang Lake (Bang Lake and Cuoji Lake) during the dry season from 1987 to 2017. The relationships between eight water regime components (annual average water level, annual maximum water level, annual minimum water level, and flooded days at five water levels [11, 13, 15, 17, and 19 m]) and aquatic vegetation coverage area were determined. The most critical water regimes were identified and results demonstrated that aquatic vegetation coverage area in Bang Lake and Cuoji Lake peaked in drier years (2005 and 2009, respectively) with no obvious up or down trend. Water regimes indicating high flow events such as annual maximum water level, flooded days at water level 19 m, and annual average water level were found to be more important for predicting aquatic vegetation. High-flow events appear to be essential for understanding aquatic vegetation dynamics in pit lakes, yet overall the influences of water level fluctuation on aquatic vegetation varied among wetland units of Poyang Lake. This study helps to understand the hydroecological dynamics in connected lakes further and provide a reference for the lake management and protection.

Wetland water-management may influence mercury bioaccumulation in songbirds and ducks at a mercury hotspot.

Mercury is a persistent, biomagnifying contaminant that can cause negative behavioral, immunological, and reproductive effects in wildlife and human populations. We examined the role of wetland water-management on mercury bioaccumulation in songbirds and ducks at Kellys Slough National Wildlife Refuge Complex, near Grand Forks, North Dakota USA. We assessed mercury concentrations in blood of wetland-foraging songbirds (80 common yellowthroats [Geothlypis trichas] and 14 Nelson's sparrows [Ammospiza nelsoni]) and eggs of upland-nesting ducks (28 gadwall [Mareca strepera], 19 blue-winged teal [Spatula discors], and 13 northern shoveler [S. clypeta]) across four wetland water-management classifications. Nelson's sparrow blood mercury concentrations were elevated (mean: 1.00 µg/g ww; 95% CL: 0.76-1.31) and similar to those reported 6 years previously. Mercury in songbird blood and duck eggs varied among wetland water-management classifications. Songbirds and ducks had 67% and 49% lower mercury concentrations, respectively, when occupying wetlands that were drawn down with water flow compared to individuals occupying isolated-depressional wetlands with no outflow. Additionally, songbirds within impounded and partially drawn-down wetland units with water flow had mercury concentrations that were 26-28% lower, respectively, than individuals within isolated-depressional wetlands with no outflow. Our results confirm that mercury concentrations in songbirds at Kellys Slough continue to be elevated and suggest that water-management could be an important tool for wetland managers to reduce bioaccumulation of mercury in birds.

Contrasting Patterns of Pomacea maculata Establishment and Dispersal in an Everglades Wetland Unit and a Central Florida Lake

The spread of non-native species raises concerns about native species displacement, while other negative effects on native species (e.g., habitat degradation) should also be considered. The highly invasive non-native apple snail Pomacea maculata has raised such concerns as it has become established in a wide range of aquatic systems worldwide. While monitoring native Florida P. paludosa populations in Lake Tohopekaliga (LTOHO) from 2001 to 2009 and in Water Conservation Area 3A (WCA3A, Everglades) from 2006 to 2015, we opportunistically documented the establishment and distribution of P. maculata. We estimated snail densities and recorded egg cluster presence in three study sites (12 total plots, LTOHO) and 137 sites (WCA3). On LTOHO, native snails were absent or at very low densities prior to finding P. maculata. Few snails of either species were found in high-stem-density vegetation of the littoral zone. Pomacea maculata immigration into the littoral zone occurred following managed vegetation removal, and Hydrilla verticillata proliferation in LTOHO likely contributed to the spread of P. maculata. We found both native and non-native apple snail species in many WCA3A sites following P. maculata invasion. We initially found the non-native snail in two sites in southern WCA3A; they were mostly restricted to within three kilometers of initial sites over the next four years. Overall plant community compositions in LTOHO and WCA3A appeared less impacted than expected based on previous reports of P. maculata invasions.

Organics and nutrients removal in vertical flow wetlands: loading fluctuation and alternative media

ABSTRACT Two wetland systems (conventional and structurally modified) were studied for the removal of organics and nutrients from municipal wastewater. Each system consisted of three vertical flow (VF) wetlands, which were filled with agricultural, construction waste materials and planted with Phragmites australis and Canna indica. The wetland units were operated under constant and consecutive shock hydraulic load (HL). Input nutrients and organics load across the wetland units ranged between 4.0–116.0 g N/m2d, 0.5–23.0 g P/m2d, 1.0–527.0 g biochemical oxygen demand (BOD)/m2d and 16.0–686.0 g chemical oxygen demand (COD)/m2d. Nitrification and organic carbon availability controlled nitrogen (N) removals in first and third stage VF wetlands, respectively, during constant load phase; organics removals were influenced by dissolved oxygen concentration of municipal wastewater. Second stage VF wetlands (of both systems) were inefficient in terms of COD removals during shock load periods, which were counter-balanced by first and third stages. First stage VF wetlands achieved higher N removal rates than following stages during shock load periods. Wetland maturation provided a buffer against substantial HL increment and sharp input load decrease in latter shock and recovery phases, respectively. Agricultural waste (sugarcane bagasse) provided carbon to support denitrification; construction materials (recycled brick and crushed mortar) removed phosphorus (P) from wastewater through adsorption. Coliform removal in VF wetlands was achieved through media filtration. Structurally modified system achieved higher removals than the conventional system. BOD, COD, total nitrogen and NH4–N removal percentage across two systems ranged between 76–79%, 59–63%, 73-77% and 90–95%, respectively. In general, this study enlightens potential application of appropriate waste materials for wastewater treatment.

Two-stage constructed wetland systems for polluted surface water treatment

Two pilot scale wetland systems were studied for the removal of organics, nitrogen, phosphorus and coliform from polluted surface water. Each system consisted of two units: a vertical flow (VF) wetland packed with construction materials gravel, brick or organic sugarcane bagasse, followed by a surface flow (SF) or floating treatment (FT) wetland. All wetland units were planted with Phragmites. The wetland systems were operated under constant and shock hydraulic load (HL) periods. Input COD, N, P loadings ranged between 61 and 2181, 7–1040, 2–194 g/m2d, respectively across first stages of each system. Mean removal percentages ranged between 39 and 97, 11–83, 20–100% and 4–85, 16–86, 1.4–100% across first and second stage wetlands, respectively. Mass balance analyses revealed ≤7% N and ≤14% P accumulation in plants; as such, microbial and adsorption kinetics controlled removal dynamics. Nitrification was the limiting nitrogen removal factor in first stage wetlands; organic carbon was supplied by the employed media. Aerobic organics removal and nitrification were diminished during initial stage of shock load periods. In contrast, second stage SF and FT wetlands showed stable removal performances under similar conditions. Resuspension of settled particles decreased removal performance in second stage wetlands, as shock periods progressed toward final stage. Coliform mortality was increased in second stage wetlands. Physico-chemical properties of brick materials in construction material based VF wetland and hanging root volume inside the water column of FT wetland supplemented removal performance. In general, this study provides evidence on potential application of constructed wetlands for polluted surface water treatment.

Efficiency of constructed wetlands in treating E. coli bacteria present in livestock wastewater

Constructed wetlands are artificial wetland units, designed for adopting the principle of natural wetlands for purifying wastewater. Well-designed and well-constructed wetlands play an important role not only in reduction in organic compound/impurities, but also in coliform reduction in wastewater. The three small laboratory-scale units were control, Typha and plant species design based on USEPA procedure. The plant species are watered for a few days to promote their stable growth. Then, the three wetland units were seeded with livestock wastewater from a nearby cattle farm. Qualitative analysis by polymerase chain reaction and quantitative analysis are carried out by doing microbial culture in selective medium of MacConkey agar. The E. coli load is monitored before and after treatment in all the three units with different trials. It is found to be at a higher level in Typha unit after 24 h than in mixed and control units. The sample from the bottom of the constructed wetland unit is withdrawn and cultured for five days, and the bacterial load is found to be 9 × 104. Meanwhile, considerable reduction is observed in the Typha wetland unit after 5 days, and the bacterial load is 4 × 102. Mixed species wetland shows excellent treatment efficiency, and the bacterial load (E. coli) is very less after 5 days. It is evident from the study that constructed wetlands are effective in the treatment of E. coli bacteria wetland plants which are used for treatment.

Recommendation of optimal design and operation parameters for constructed wetland for sludge treatment based on the effect of hydraulic retention time, sludge loading rate and vegetation

Industrial sludge is a by-product which is enormously generated in wastewater treatment plants. Constructed wetland for sludge treatment (CWST) is a low cost, effective technology. This study investigated the effect of various design and operation parameters on the efficiency of four pilot-scale CWSTs to determine the optimal parameters by using the Analytic Hierarchy Process (AHP) for Decision- Making. The wetland units were planted with Phragmites australis or Typha angustifolia, operated with four sludge loading rate (SLR) (50, 60, 70 and 80 L/m2) and monitored in six different hydraulic retention time (HRT) (2,5,7,9,12 and 14 days). AHP results provided the optimal key parameters (vegetation of P. australis, 14-day HRT, SLR of 60 L/m2) which gave the most effective sludge treatment, reducing 99.8%, 95.16% and 98.23% for COD, TKN and TP, respectively. The results also showed that HRT, SLR and vegetation remarkably affected to the efficiency of CWST. In addition, AHP is an effective method to determine the optimal design and operation parameters of CWST.&#x0D;

Constructed wetlands for industrial wastewater treatment: Alternative media, input biodegradation ratio and unstable loading

This paper reports comparative pollutant removal performances across two parallel hybrid wetland trains, that were dosed with mixed industrial wastewater (with poor biodegradability); each train included two vertical flow (VF) wetlands arranged in series, followed by a surface flow (SF) wetland as the final treatment stage. VF wetlands of system 1 and 2 were packed with biological and construction materials, respectively. Input hydraulic load (HL) was fluctuated between 113.0–226.0 mm/d across first stage wetland units of both systems. Performance analyses indicated higher organics and nitrogen removal percentages in first stage VF wetland of system 1, due to carbon leaching from the employed organic bagasse and biochar media. On the other hand, lack of carbon supply from inorganic construction materials hindered such removals in first stage VF wetland of system 2, which was counter-balanced as the wastewater passed through second stage VF unit. Enhanced P removals were quantified in VF wetlands of system 2, which could be linked to P adsorption properties of the employed construction materials. VF wetlands of both systems were inefficient in terms of color compounds removal. Physico-chemical and microbial pathways enhanced removal in the last stage SF wetlands of both systems and improved overall removal. Organics and nitrogen removal rates (g/m2 d) in experimental wetlands were high at upper input loadings; however, load based (g/m2 d) removal percentages were high in first and third stage wetlands (of both systems) during lower loading ranges. Concentration based mean overall NH4-N, TN, P, BOD, COD and color removal percentages across both systems were: ≥ 90.0, ≥ 86.0, ≥ 91.0, ≥ 92.0, ≥ 85.0 and ≥ 87.0%, respectively. Such performances signify potential combination of VF (packed with biological and construction materials) and SF wetlands, for the treatment of hardly degradable industrial wastewater.