Vertical Subsurface Flow Wetland Research Articles

A TESTING STUDY OF WASTE WATER TREATMENT USING REED BED SYSTEM

Following industrialisation, a number of companies generate poisonous waste materials are carelessly dumped into streams and rivers, harming both aquatic and terrestrial life. In this study, a reed bed system for harmful metal removal from industrial waste water was examined. In the Amrutha water treatment plant, a vertical subsurface flow wetland was created to remove hazardous metals from industrial effluent. For the Wetland system, phragmites Karka was employed, and the substrates used were granite and washed sand. Hydraulic retention times of 5, 9, 10, 14, and 18 days were used to record treatment performance. You can create a waste water treatment facility in your own garden with a reed bed sewage system. It must be used in conjunction with a septic tank in order to function as a sewage system. Two reed beds are required for a reed bed sewage system to function properly. One bed must fill for a while while the other drains, and then the process must be reversed. The results indicated that the hazardous metals gradually decreased as the retention times increased. The reed bed rate removal ranges from 36.8% to 61.5%. These findings support the phragmites karka reed plant's ability to effectively treat industrial effluent.

Kinetic modelling and performance evaluation of vertical subsurface flow constructed wetlands in tropics

The design of vertical subsurface flow (VSSF) constructed wetlands (CWs) uses kinetic models to calculate the area based on the kinetic reaction rate constant (k) specific to local environmental conditions and target pollutants. Currently, kinetic modelling does not fully account for the impact of the hydraulic loading rate (HLR), which influences the wetland performance. This study used four experimental VSSF CWs operated at HLRs of 5, 10, 20 and 40 cm/day to investigate the applicability of three first order kinetic models combining plug-flow and continuous stirred tank reactor (CSTR) flow patterns. The target pollutants were BOD5, NH4+ and NO3-. For each pollutant, estimated k values varied between different HLRs and between plug flow and CSTR models. Assessment of uncertainty in kinetic modelling showed that all three models exhibit a similar trend in predicting the concentrations of BOD5 and NH4+ at 5–20 cm/day HLRs. A substantial removal of BOD5 (>88 %) and NH4+ (>70 %) were found for the investigated HLRs, although NO3- removal was not satisfactory. The HLR had a positive impact on mass removal rates (MRRs) for BOD5 and NH4+. Accordingly, 20 cm/day was deemed as the highest viable HLR for designing effective VSSF wetlands for the removal of BOD5 and NH4+. All three models can be employed to design VSSF wetlands at 20 cm/day HLR to treat BOD5 using k values of 0.352 (k-C), 0.380 (k-C*) and 0.996 (CSTR) m/day and to treat NH4+ using k values of 0.170 (k-C), 0.173 (k-C*) and 0.273 (CSTR) m/day.

Life cycle assessment and costing of wastewater treatment systems coupled to constructed wetlands

This study evaluates the environmental and economic performance (ecoefficiency) of two decentralized, small-scale, wastewater treatment systems coupled to constructed wetlands. System One comprises a vertical and a horizontal flow wetland. System Two comprises a vertical subsurface flow wetland with artificial aeration. A life cycle assessment based on data from two actual pilot structures was carried out. The functional unit was 1 m3 of treated water over a 20-year long lifetime. The systems were modeled in open LCA software, with the aid of Ecoinvent 3.3 data, and the impact assessment was based on the ReCIPe method. Results have demonstrated that foreground emissions such as direct greenhouse gas released from the septic tank and nutrients released in the effluent have driven potential impacts related to Climate Change, Photochemical Oxidants, and Freshwater Eutrophication. Artificial aeration reduces the area required for the installation of the system and electricity consumption was responsible for only 7% of total Climate Change related potential impact. Technologies that reduce direct (foreground) liquid and airborne emissions will improve the environmental performance of the systems. The analysis of the aerated wetland has shown that the operation stage had the greatest environmental impact potential for all analyzed impact categories, with results varying between 64% for Human Toxicity and 100% for Freshwater Eutrophication. The life cycle cost per cubic meter of treated sewage for the aerated system was 1.8 times smaller than that of the system without aeration. Thus, aeration is cost-effective for small-scale wastewater treatment systems coupled to constructed wetlands.

Influence of Different Porous Media and Ornamental Vegetation on Wastewater Pollutant Removal in Vertical Subsurface Flow Wetland Microcosms

Abstract To investigate the effects of porous media and ornamental plants on pollutant removal in vertical subsurface flow constructed wetlands (CWs), 24 microcosm systems were tested from March to...

Enhancement of total nitrogen removal through effluent recirculation and fate of PPCPs in a hybrid constructed wetland system treating urban wastewater.

The effect of effluent recirculation on the removal of total nitrogen (TN) and eight pharmaceuticals and personal care products (PPCPs) was evaluated during 9months in an experimental hybrid constructed wetland (CW) system applied in the treatment of urban wastewater. An Imhoff tank was followed by three stages of CWs (two 1.5-m2 vertical subsurface flow (VF) beds alternating feed-rest cycles, a 2-m2 horizontal (HF) and a 2-m2 free water surface (FWS) wetland in series). A fraction of the final effluent was recycled back to the Imhoff tank with a recirculation rate of 50% (hydraulic loading rate=0.37md-1). The system's performance varied throughout the study. In Period I (summer) consistently high load removal efficiencies of TN (89±5%) and a removal rate of 6.6±1.4gTNm-2d-1 were exhibited. In Period II (fall), the poor performance of the FWS during the senescence of macrophytes caused a large increase in organic matter, solids and nutrient concentrations, drastically deteriorating water quality. The determination of PPCPs was conducted during this period. Recalcitrant compounds, namely sulfamethoxazole, carbamazapine, TCEP and sucralose were negligibly removed in all CWs. However, noteworthy was the ≈30% removal of sucralose in the VF wetland. Caffeine (80%) and fluoxetine (27%) showed similar elimination rates in both VF and HF units, whereas trimethoprim and DEET were significantly better removed in the VF than in the HF. The concentration of the four latter compounds showed a severe increase in the FWS, indicating possible desorption from the sediment/biomass during adverse conditions. Harvesting of the aboveground biomass in this unit returned the system's performance back to normality (Period III), achieving 77±7% TN removal despite the winter season, proving effluent recirculation as an effective strategy for TN removal in hybrid CW systems when stringent restrictions are in place.

Performance of Tropical Vertical Subsurface Flow Constructed Wetlands at Different Hydraulic Loading Rates

The hydraulic loading rate (HLR) plays a vital role in pollutant removal in constructed wetlands. This study evaluated the effects of HLR variation on pollutant removal in continuously fed vertical subsurface flow (VSSF) constructed wetlands in tropical conditions. Three VSSF wetland beds (Length: 1.4 m, Width: 0.5 m and Depth: 0.6 m), filled with 10–20 mm gravel media, were set up in a tropical region. Two beds were planted with a locally available emergent macrophyte narrow‐leaf cattail (Typha angustifolia), and the remaining bed was used as a control without plants. The performance of these wetland mesocosms was tested at different HLRs of 2.5, 5, 7.5, 10, 12.5, 15, 20, 25, and 30 cm day−1 changing at 2 week intervals in two phases over a period of 6 months. The results revealed that both VSSF wetland systems are capable of substantial reduction of pollutants with a good buffering capacity up to 25 cm day−1 HLR.

Carbamazepine removal in three pilot-scale hybrid wetlands planted with ornamental species

The aims of this one-year study, were to evaluate the removal of carbamazepine (CBZ) in three pilot-scale two-stage hybrid constructed wetlands as well as to evaluate the performance of three emergent species (Thypha latifolia, Iris sibirica and Zantedeschia aethiopica) planted as a polyculture. The systems included horizontal subsurface flow wetlands (HSSF-CW), vertical subsurface flow wetlands (VSSF-CW) and stabilization ponds (SP). The three different configurations were: HSSF-CWs followed by SPs, HSSF-CWs followed by VSSF-CWs and VSSF-CWs followed by HSSF-CWs, which were identified as system I (SI), system II (SII) and system III (SIII) respectively. In addition, measurements of DO, Eh and pH, were taken in situ in order to know the internal system conditions. Out of the three hybrid systems, two were equally effective (SI and SII) and superior to SIII (p>0.05). In these two systems (HSSF-CWs- SPs and HSSF-CWs-VSSF-CWs) the average mass removals were 62.5±4.5% and 59.0±4.5%, respectively. CBZ removal was more effective under reductive environment (∼−60 to +50mV) and near-anoxic conditions (<1.5mg/L of DO). In addition, the two ornamental plants exhibited a better capacity to tolerate and take up CBZ in comparison to T. latifolia. These results demonstrate that it is possible to obtain higher CBZ removal efficiencies in CWs than those reported so far, under subtropical climate by using hybrid systems planted with a polyculture that include ornamental species and using a ground local filter material.

Emerging organic contaminant removal in a full-scale hybrid constructed wetland system for wastewater treatment and reuse

A full-scale hybrid constructed wetland (CW) system based on three stages of different wetlands configurations showed to be a very robust ecotechnology for domestic wastewater treatment and reuse in small communities. It consisted of a 317-m2 vertical subsurface flow (VF), a 229-m2 horizontal subsurface flow (HF), and a 240-m2 free water surface (FWS) CWs operating in series. VF and HF wetlands were planted with Phragmites australis and the FWS contained a mixture of plant species. An excellent overall treatment performance was exhibited on the elimination of conventional water quality parameters (98–99% average removal efficiency for TSS, BOD5 and NH4–N; n=8), and its final effluent proved to comply with existing Spanish regulations for various reuse applications. The removal of studied emerging contaminants, which included various pharmaceuticals, personal care products and endocrine disruptors, was also very high (above 80% for all compounds), being compound dependent (n=8). The high rates were achieved due to high temperatures as well as the differing existing physico-chemical conditions occurring at different CW configurations, which would allow for the combination and synergy of various abiotic/biotic removal mechanisms to occur (e.g. biodegradation, sorption, volatilization, hydrolysis, photodegradation). While aerobic metabolic pathways and solids retention are enhanced in the VF bed, other removal mechanisms such as anaerobic biodegradation and sorption would predominate in the HF bed. At last, photodegradation through direct sunlight exposure, and less importantly, sorption onto organic matter, seem to take an active part in organic contaminant removal in the FWS wetland.

Nitrogen reduction in stormwater from livestock lots by vertical subsurface flow wetlands packed with woodchips

This study was done to investigate the performance of vertical subsurface flow (VSF) wetlands with additional carbon sources in reducing the nitrogen in stormwater from livestock lots. Three experimental lab-scale VSF wetlands packed with woodchips were constructed. The wetlands were operated with number of dry days (NDD) of 2, 4, and 8, respectively, for a duration of 136 d. The average removal efficiencies of total nitrogen (TN) were 26.2, 34.1, and 50.0% at NDD as 2, 4, and 8, respectively. The average nitrogen removal rate based on woodchips volume was 3.6g N m−3 d−1 for NDD of 2, 2.1g N m−3 d−1 for NDD of 4, and 1.7g N m−3 d−1 for NDD of 8. Nitrification and denitrification were the major mechanisms of nitrogen reduction in the studied wetlands. The contribution of other pathways to nitrogen removal was small. The removal of total Kjeldahl nitrogen (TKN) and TN was not affected by the influent pH, whereas the removal of TKN was enhanced by the increase in influent alkalinity. Nitrification was promoted by the abundant oxygen supplied during the course of recirculation, whereas denitrification might be suppressed to some degree by the oxygen.

Post-treatment schemes of the outflow from hydrocyclone treating paved-road stormwater runoff

Results of water quality analysis indicated that the outflow from a hydrocyclone treating road runoff still requires further treatment before discharging into receiving waters. Hence, several treatment designs were presented for the post-treatment of the hydrocyclone outflow (including pollutant-concentrated underflow and pollutant-separated overflow). The design criteria were based on some of the main affecting factors, such as treatment level, land availability, and construction cost. With respect to the determination of the treatment goal, the primary consideration should lie on the water quality requirement. The treatment should normally include both underflow and overflow depending on the required discharged water quality. In terms of the treatment method selection, land availability and construction cost should be considered first in the design. In order to achieve the most appropriate treatment, the design process should be based on the overall analysis of the affecting factors and local conditions. In this study, three types of post-treatment (vertical sub-surface flow wetland, baffled settling tank and surface sand filter) were proposed for dealing with highly concentrated underflow from a hydrocyclone. For the treatment of both underflow and overflow, the wetland system equipped with a settling tank or a sand filter was recommended under the conditions that further treatment is required and the land and funding are available.

Performance of a hybrid constructed wetland treating piggery wastewater

A full-scale hybrid constructed wetland (HCW) designed to treat 5m3/d of piggery wastewaters built in 2008 on a private pig farm in northern Italy was monitored from May to December 2009 to determine its efficiency in treating COD, total nitrogen (TN), ammonia nitrogen (NH4–N), nitrate nitrogen (NO3–N) and total phosphorus (TP). In situ measurements were also taken of pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature (T). The system was composed of three vertical-subsurface flow wetlands (VF) (10m2 each, one planted with Canna indica and the other two with Symphytum officinale) working in parallel, followed by one horizontal-subsurface flow wetland (HF) connected in series (100m2 planted with Phragmites australis). The system was fed with pre-treated piggery wastewater with the total daily load (5m3) divided in two batches 11h apart. Wastewater samples were collected at the inflow (IN), outflow of VF unit (OUT-VF) and outflow HF unit (OUT-HF). Median COD concentration decreased from 1126 at the inlet to 235mg/L at the outlet (79% abatement). TN concentration was abated by 64% (671–240mg/L). NH4–N and NO3–N median inflow concentrations (390 and 6.61mg/L) were reduced by 63% and 53%, respectively, with median outflow concentrations of 145 and 3.14mg/L. Inflow phosphorus concentration of 23mg/L was abated by 61%. Average daily mass removal rates were 31.4g/m2 for COD, 17.5g/m2 for TN and 0.54g/m2 for TP.The HF unit was more efficient than VF in reducing COD concentration; VF and HF gave similar abatements for TN and TP, but VF occupied a quarter of the surface of the HF.The results show that the HCW is an effective solution for treating the excess pollutants deriving from animal wastewaters where sufficient land is not available for spreading.

Performance of a vertical subsurface flow (VSF) wetland treatment system using woodchips to treat livestock stormwater

This study was conducted to develop a vertical subsurface flow (VSF) wetland remediation system packed with woodchips to control stormwater pollution arising from livestock agriculture. Three lab-scale VSF wetlands were operated with recirculation during the interval (Δ) between storms as 2, 4 and 8 days, respectively. The fed water was 100% recirculated one time per 24 h; the recirculation frequency was 1, 3 and 7 times at Δ of 2, 4 and 8 days, respectively. The constructed wetland systems proved to be effective in reducing total suspended solid (TSS), but also had potential for increasing TSS in the effluent due to the properties of the woodchips. The release of organic matter, especially in the dissolved form, occurred during the initial 60 days. The removal efficiencies of total nitrogen (TN) were 26.2%, 34.1% and 50.0% at Δ of 2, 4 and 8 days, respectively. Nitrification was promoted by the abundant oxygen supplied when the water in wetland was recirculated and fed into the wetland. Denitrification was stable and effective due to the availability of carbon sources. The influent total phosphorus (TP) was reduced from an average of 2.05 mg L(-1) to 1.79 mg L(-1), 1.36 mg L(-1) and 0.86 mg L(-1) at Δ as 2, 4 and 8 days, respectively. The result shows that woodchips can be used as substrate material for VSF wetland treatment systems to control nutrient influx from livestock stormwater.

Vertical Subsurface Wetlands for Wastewater Purification

Abstract In this paper, firstly, was carry out the design of a vertical subsurface flow wetland, this treatment system was designed to be placed after the already existing treatments in the company of weld rails (SOLCAR) in Placetas Cuba, the existent treatment in this company consists of septic moat and a settlement. These treatments do not reduce the pollutants below the limits of download, these wastewaters are discharged to a basin of national importance because water supplies to the population. The characterization of the wastewater was realized according to Standard Methods for the Examination of Water and Wastewater and show high levels of nutrients and organic matter, as well as, low levels of dissolved oxygen, having anoxic characteristics the wastewater effluent from the settlement. Is proposed a vertical subsurface wetland by characteristics of wastewater with low levels of dissolved oxygen and intermittent feeding (twice a week), the calculation of the necessary area for the wetland was carried out considering the kinetic behaviour of these systems like of first order for the removal of the BOD. A vertical subsurface wetland with a superficial area of approximately 20 m 2 with 0.8 m of height and as substrate the red ferralitic soil that presents high contain of iron and aluminium, which favours the phosphorus removal, planted with Scirpus Alternifolios . After of the wetland construction was realized an evaluation of the efficiency in the purification of the main polluting agents, results demonstrated the use of vertical subsurface flow wetland as an appropriate treatment to reduce pollutants in wastewater, having been obtained a significant increase of dissolved oxygen (5 mg/L), the reduction of the nutrients in the effluent wastewater (around 1.5 mg of total phosphorus per litre and 2 mg of total nitrogen per litre) and the level of BOD (6 mg/L) and COD (15 mg/L) also were reduced. According to these results, it can be concluded that the wetland system utilized in this research could be a suitable solution for wastewater purification.

Effects of water level fluctuation on radial oxygen loss, root porosity, and nitrogen removal in subsurface vertical flow wetland mesocosms

Laboratory experiments were conducted to investigate the effects of water level fluctuation on plant radial oxygen loss (ROL), root porosity, plant growth performance, and nitrogen dynamics in vertical subsurface flow wetland mesocosms. Four types of mesocosms were used: control with static water level, control with fluctuating water level, static water level with plants, and fluctuating water level with plants. Typha orientalis, an emergent macrophyte, was used in this study. Changes of ROL, root porosity, and plant biomass were measured every six weeks. Shoot height and density of plants were also observed. Every two weeks, the nitrogen removal efficiency of the four systems was monitored. Maximum ROL values under static and fluctuating conditions were 7.58 and 2.73 μmol/g DW/h, respectively. The porosity values of roots under static and fluctuating conditions ranged between 33–47% and 30–37%, respectively. Average removal efficiency of both total nitrogen (TN) and ammonium nitrogen (NH 4-N) in the fluctuating condition with plants was about 65%, and nitrate nitrogen removal in the static condition with plants was about 75%. Although the water level fluctuation caused a considerable reduction in ROL and root porosity, it clearly produced a significant improvement in TN and NH 4-N removal.

Effect of Water Level Fluctuations on Nitrogen Removal and Plant Growth Performance in Vertical Subsurface-Flow Wetland Mesocosms

ABSTRACT The effects of Typha orientalis and water level fluctuation on nitrogen and organic carbon removal were studied in vertical subsurface flow mesocosm columns over a six month period. The treatments were control (U1, without plants); conventional (U2, no fluctuation); drawdown (U3, daily removal of wastewater from the upper 5 cm layer); and, drained (U4, removal of all pore water once every 10 days). Synthetic wastewater containing 20 mg L−1 of total nitrogen (TN) and 10 mg L−1 of total organic carbon (TOC) was used as the influent water. Influent and effluent waters were sampled every two weeks; T. orientalis was sampled at six-week intervals to evaluate biomass, shoot density, cumulative height and root porosity. The U3 system outperformed the U2 and U4 treatment systems (P < 0.05) in nitrogen removal, and the U4 system outperformed U3 and U2 in TOC removal. Estimated plant biomasses under treatments systems U2, U3, and U4 were 2.43, 2.19 and 2.49 kg/m2, respectively. T. orientalis that were grown under treatment U2 had the highest root porosity.

Nitrogen Removal from Landfill Leachate Using a Compact Constructed Wetland and the Effect of Chemical Pretreatment

Onsite treatment of leachate was implemented at the Tveta Landfill, adjacent to the city of Södertälje, Sweden. The system consists of leachate collection in a pond, precipitation of metals with chemicals, a constructed wetland, and forest irrigation. This article describes the constructed wetland and its effectiveness at removing ammonia in the system. Pulsed-discharge hydrology and wetland ecology formed the basis for the development of a compact constructed wetland (CCW). The system presented here has most design similarities with vertical sub-surface flow wetlands, though this system is run in batch mode. Chemically purified leachate and untreated leachate were applied to separate sections of the CCW using a filling and emptying schedule. A leachate treatment cycle of about 14 days duration was used, involving a 7 day submerged phase followed by a 7 day drained period. The removal efficiency varied between 40 and 75% on a mass basis. A maximum mass removal rate of up to 5.1 g m− 2 d− 1 was achieved in wetlands receiving leachate after chemical pretreatment. In wetlands receiving non-treated leachate a net release of up to 18 g m− 2 N occurred in the form of nitrate. This indicated a considerable nitrification but limited denitrification in those systems. It was unclear whether the chemical treatment enhanced the nitrogen removal efficiency because of lower toxicity and/or content of fewer competing cations, or other mechanisms. Mechanisms responsible for the NH4-N removal in the CCW system have to be further investigated.