Hybrid Wetland Systems Research Articles

Performance of a multi-stage hybrid wetland system for the treatment of a dairy effluent

This work evaluates the performance of a pilot-scale hybrid wetland (HW) system for the effluent treatment from a dairy industry, located in Santa Fe (Argentina). The system consists of three stages in a serial configuration: vertical flow (S1) – free water surface (S2) – horizontal subsurface flow (S3) wetlands. The HW was operated during nine months. Wastewater, plant and sediment samples were taken from the system. Main pollutant concentrations were determined in wastewater. N and P concentrations were determined in plant tissues and in sediments to evaluate the accumulation in the system. The mean COD, BOD, TN, and TP removals in the whole HW system were 91 %, 94 %, 76 %, and 64 %, respectively. Organic matter concentration decreased due to aerobic and anaerobic degradation processes in all stages, mainly in S2. S1 presented proper conditions for nitrogen compounds interconversions by ammonification and nitrification processes. The highest total nitrogen removal was achieved in S2. Plant uptake contributed significantly to nutrient retention in S2 and S3. In S2, sediment did not participate significantly in nutrient retention. Phosphorus removal showed the lowest system efficiency. The obtained results determine the system performance under site-specific conditions, which contributes to the scaling process of the treatment wetland.

Pollutant removal modeling in a hybrid wetland system for industrial wastewater treatment

Modeling of treatment wetlands allows the prediction of system behavior and facilitates large-scale design by evaluating the effects of modifying the operating parameters. The aim of this study was to calibrate and verify applicable models in vertical flow (VF) and horizontal subsurface flow (HSSF) wetlands -first and second stage of the hybrid wetland (HW) system- operating in site-specific environmental conditions. Stepwise multiple linear regression analysis, oxygen demand model, and k-C* model, were applied to each stage of the HW system as appropriate. All models were calibrated and verified based on the data observed by monitoring the HW system. Afterwards, simulations were performed at each stage of the HW system. The simulations show the dependence of nitrification on the availability of NH4+-N and also that both, the increase in Org-N and COD loading, affect the efficiency of nitrification in the VF stage. In the HSSF stage, simulations show that the increase in hydraulic or pollutants loading rate has a positive impact on the performance of the system. The fit achieved in the models was satisfactory and the results obtained by simulation provide a useful tool to evaluate the performance of the HW system in different possible operating scenarios.

Constructed Wetland for Low- Cost Waste Water Treatment

Engineered and managed wetland systems that are receiving increasing global attention for wastewater treatment and reclamation. Compared to conventional wastewater treatment plants, constructed wetlands are inexpensive and easy to operate and maintain, and they have strong potential for application in a small community. Constructed wetlands for wastewater treatment have developed significantly in recent decades. As an environmentally friendly treatment method, constructed wetlands can enable effective, economic and ecological treatment of agricultural, industrial and municipal wastewater. Built-up wetlands are very effective in removing organic matter and suspended matter, while nitrogen removal is relatively low, but could be improved by using a combination of different types of built-up wetlands that meet irrigation reuse standards. Phosphorus removal is usually low unless special media with high sorption capacity are used. Removing pathogens from wetland effluent to meet irrigation reuse standards is a challenge unless additional lagoons or hybrid wetland systems are used. This paper examines and also describes various case studies related to wetlands in Indian cities, including systems that include both built and natural wetlands, habitat creation and restoration.

Potentialities of plant based hybrid wetland systems for the treatment of household waste water using Canna indica, Agave americana, Pistia stratiotes and Tagetes erecta

The ever increasing population is generating large amount of waste water and it is increasing with time especially with the higher per capita consumption of water in the country. Besides, the ample amount of energy required by the conventional water treatment methods is hampering the economic viability of the procedure. This asks for newer and efficient low cost nature based water treatment system which along with cost takes into consideration the sustainability of the ecosystem. In this study a hybrid plant based wetland system consisting of four plant species were used to treat the household grey water. Agave americana and Tagetes erecta were used in constructed wetland, Canna indica plant was used in floating raft wetland and Pistia stratiotes in oxidation pond for a period of 24 h retention to know the efficiency. The pollution reduction was analysed after 2 h, 4 h, 6 h, 8 h and 24 h hydraulic retention period (HRT) in all these systems. Three parameters basically BOD, COD and salinity reduction were checked as an initial research to know the viability. The results showed that BOD reduction ranged from 6.67 to 41.18% in various systems within 24 h of retention, whereas COD showed a reduction range of 5.32–35.47% and salinity exhibited a reduction range of 6.93–21.49% based on the different systems.

A comparative landfill leachate treatment performance in normal and electrodes integrated hybrid constructed wetlands under unstable pollutant loadings.

This study provides a comparative pollutant removal performance assessment between organic or construction materials-based four hybrid wetland systems that received landfill leachate. The hybrid systems included vertical flow (VF) followed by horizontal flow (HF)-based unplanted and planted systems, and planted electrodes incorporated microbial fuel cell (MFC) integrated hybrid wetlands systems. All the systems were run in free-draining mode. Overall mean chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) removal percentage of the hybrid systems ranged between 81 and 99%, 82 and 96%, 74 and 99%, respectively, under unstable input pollutant loading conditions. Additionally, up to 27% organic and up to 14% nitrogen removal improvement was observed in electrodes integrated free-draining VF wetlands. Free-draining and additional oxygen availability from atmospheric diffusion, rootzone improved the removal performance of MFC-based VF wetlands. Input load increment decreased organic, nutrient removals in second stage HF units due to saturated media. The chemical composition of the employed media supported biotic, abiotic organic, nutrient removal pathways. Nutrient accumulation percentage in plants tissue was very low, i.e., ≤3%. Bioenergy production across the MFC-based VF-HF wetlands decreased with input pollutant load increment. The single anode electrode-based VF wetland achieved maximum power density production, i.e., 294 mW/m2.. The electrodes integrated hybrid systems achieved comparatively stable removal performance despite input pollutant/hydraulic load variation.

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.

Household Scale Treatment and Reuse of Laundry Greywater Through a Hybrid Wetland System

Household Scale Treatment and Reuse of Laundry Greywater Through a Hybrid Wetland System

Pilot-Scale Hybrid Wetland System for the Final Treatment of Dairy Wastewater

Pilot-Scale Hybrid Wetland System for the Final Treatment of Dairy Wastewater

Effect of effluent recirculation on nutrients and organics removal performance of hybrid constructed wetlands: Landfill leachate treatment

Landfill leachate treatment is challenging because of complex chemical composition. This study identifies the factors associated with organics and nutrients removal performance improvement in construction or organic materials based four hybrid wetland systems dosed with landfill leachate. The imbalanced pollutant composition ratio of leachate influenced removal pathways in the hybrid wetlands; effluent recirculation (50 and 25% ratios) adjusted leachate composition and improved removal performances. Mean nitrogen (N), phosphorus (P), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) removal percentages in the hybrid wetlands during without, with recirculation periods ranged between 50 and 93, 69–100, 34–89, and 55–76%, respectively. Pollutant removals were achieved through adsorption, microbial (heterotrophic organic removal, ammonia assimilation, nitrification, denitrification) degradation, and plant uptake. Removal rates did not vary substantially among organic or construction materials based first stage VF (vertical flow) wetlands because of leachate composition. Constant water saturation depth variation influenced pollutant removal rates among the second stage wetlands. Shallow water depth HF (horizontal flow) wetlands appeared to be a promising wastewater treatment technology due to the coexistence of unsaturated, saturated bed matrix that supported diverse removal pathways.

Removal of Fluoride and Arsenic by a Hybrid Constructed Wetland System.

A pilot-scale hybrid wetland system was constructed for the removal of fluoride and arsenic from synthetic wastewater. After five months of operation, the fluoride and arsenic removal rate were at the value of 65 % and 90 %, respectively. Through calculation, the accumulation of fluoride in plants only accounted for 1.63 % of the accumulation in substrates, and the accumulation of arsenic in plants accounted for 3.3 % of that in substrates. Both the accumulation of fluoride and arsenic in plants were much higher in roots than that in leaves. And for substrates, the accumulation in the first layer was higher than the second layer. The changes of microbial community in the substrate of the wetland during the operation were also analyzed to investigate the effects of operating condition on the microbial community and to study the role of microorganism on the removal of fluoride and arsenic. The results showed that the relative abundance of Firmicutes reduced, while the relative abundance of Proteobacteria increased, indicating that the fluoride and arsenic in solution had a great influence on the microbial community. Findings of this study suggest that the hybrid constructed wetland system may be a promising process for the removal of fluoride and arsenic from synthetic wastewater.

Organic matter and nutrients removal in hybrid constructed wetlands: Influence of saturation

Three hybrid wetland systems were studied for organics and nutrients removal from synthetic wastewater recipe. Each system included a vertical flow (VF) followed by a horizontal flow (HF) wetland. The wetlands were filled with common and unconventional media (gravel, biochar and sand) with different saturation and water depth ratio. Input N, P and COD loadings ranged between 48–145, 1–7 and 56–191 g/m2 d, respectively across first stage VF wetlands. Recalcitrant compounds of synthetic recipe reduced organics removals in VF wetlands. NH4-N adsorption and carbon leaching properties of biochar triggered N removals (19–102 g/m2 d) in partially saturated VF wetlands. Carbon unavailability influenced N removals in gravel based unsaturated VF wetland. Input N load increment reduced nitrification and NH4-N adsorption in VF wetlands. However, such increment improved N removal percentages in shallow water depth second stage HF wetlands, primarily due to removals in previous stages and atmospheric oxygen transfer via unsaturated zone; HF wetland with deep water depth showed opposite removal trend. P removal in experimental wetlands was achieved via media based adsorption; decrease of P concentration in synthetic recipe enhanced removals. N and P contents percentage (with respect to total removal) in plants ranged between 1 and 7% (VF), 5–17% (HF) and 2–36% (VF), 23–35% (HF), respectively, indicating dominance of microbial transformation and media based adsorption on observed removals. Partially saturated-shallow water depth hybrid wetland systems achieved ≥90% BOD, ≥97% N and 100% P removals. This study signifies potential application of partially saturated-shallow water depth hybrid wetland systems packed with unconventional media for wastewater treatment.

Bacterial community activity and dynamics in the biofilm of an experimental hybrid wetland system treating greywater.

The objectives of this study were to determine the biofilm microbial activity and bacterial community structure and successions in greywater treatment filters and to relate the treatment efficiency to the bacterial community parameters. This 10-month study was performed in a newly established experimental system for domestic greywater treatment that consisted of three parallel vertical flow filters (VFs) followed by a horizontal flow filter (HF). A rapid increase in the bacterial community abundance occurred during the first 85days of filter operations, followed by a short-term decrease and the stabilization of the 16S rRNA gene copy numbers at average levels of 1.2 × 109 and 3.2 × 108 copies/g dw in VFs and HF, respectively, until the end of the experiment. The dominant bacterial phyla and genera differed between the VFs and HF. The temporal variation in the bacterial community structure was primarily related to the species replacement, and it was significantly affected by the influent organic carbon and nitrogen compounds in the VFs and the ammonia and organic carbon in the HF filters. Despite the differences in the community structure and assembly mechanisms, the temporal dynamics of the bacterial community showed high congruence between the filter types. The treatment efficiency was related to the biofilm bacterial community diversity and abundance and the abundance of certain bacterial genera in the VF filters. The results suggest that the dominant pathway of nitrogen removal by greywater treatment VFs occurs via coupled heterotrophic nitrification and denitrification, while the contribution of aerobic denitrification is temporally variable in these filters.

Post-treatment of effluents from UASB reactor treating industrial wastewater sediment by constructed wetland

ABSTRACTThe improvement of water quality parameters by wetland systems is an increasingly global practice. In the present study, the utilization of a treatment method comprising of an upflow anaerobic sludge blanket (UASB) reactor followed by a surface flow (SF) and a vertical flow (VF) wetland (hybrid wetland) in the arrangement has been tested experimentally. Lemna minor was used in wetland units at a planting density about 3 kg wet m−2. The UASB reactor effluents were diluted with tap water to keep the influent chemical oxygen demand (COD) at about 1000 mg L−1 and then fed semi-continuously to lab-scale hybrid wetland system. Removal efficiency ranged from 80 to 93% treatment for COD and biochemical oxygen demand (BOD5), about 92–98% for total phosphorus (TP) treatment and total Kjeldahl nitrogen (TKN), and except Hg (approximately 83%), heavy metal removal was over 90%. Post-treatment of UASB reactor effluents with hybrid wetland provided a high COD, BOD5, TKN, ammonia–nitrogen, TP and phosphate–phosphorus removal and efficiently removed heavy metals (Hg, Cr, Zn, Al, As, Cd, Co, Cu, Pb and Ni). In addition to this, the bioconcentration factor of these heavy metals by the L. minor was also studied in the present study.

Wetlands for wastewater treatment and subsequent recycling of treated effluent: a review

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used.

伏流式ヨシ濾床人工湿地処理によるバレイショ澱粉工場廃液中のジャガイモそうか病菌Streptomyces turgidiscabies の菌密度変化

伏流式ヨシ濾床人工湿地処理によるバレイショ澱粉工場廃液中のジャガイモそうか病菌Streptomyces turgidiscabies の菌密度変化

Study on treatment of aquaculture wastewater using a hybrid constructed wetland

This paper reported the pollutant removal performances of a hybrid wetland system for the treatment of aquaculture wastewater. The system consisted of two treatment stages: a subsurface vertical flow (VF) wetland, followed by a horizontal flow (HF). The aquaculture wastewater with the different concentrations such as eutrophy and mesotrophy was treated using hybrid constructed wetland. The experimental results showed that the removal efficiencies of eutrophy aquaculture wastewater achieved 56%, 71%, 73% for nitrite, phosphate and nitrate, respectively. At the same conditions, it can be found that the removal efficiencies of mesotrophy aquaculture wastewater achieved 39%, 74%, 73% for nitrite, phosphate and nitrate, respectively.

Effluent quality and reuse potential of domestic wastewater treated in a pilot-scale hybrid constructed wetland system

The study investigates treatment and reuse potential of domestic wastewater of a small community of about 30 people sequentially by anaerobic pretreatment followed by horizontal (HSSF-CW) and vertical (VSSF-CW) sub-surface flow constructed wetlands operated in series. The organic and suspended solids load to the hybrid wetland system was decreased by anaerobic pretreatment. HSSF-CW mainly removed organic matter and supported denitrification whereas VSSF-CW mainly obtained nitrification and phosphorus removal. Recirculation of the effluent increased particularly total nitrogen removal in the wetland system. The study involves evaluation of the whole system in terms of effluent quality. It was achieved on average >95% organic matter and >90% nitrogen removal in the hybrid constructed wetland system with anaerobic pretreatment at a specific wetland surface area of only about 1 m2 per person. Average mass removal rates were 21.17 gCOD/m2day, 5.58 gBOD5/m2day, 2.78 gTKN/m2day, 1.35 gTN/m2day, 0.44 gTP/m2day and 5.21 gTSS/m2day throughout the total duration of the operation. Consequently, the effluent met the regulations for discharge limits for organic matter and suspended solids. COD and TN concentrations decreased to below 20 mg/L in the effluent. It was also shown that effluent of the system could be reused for irrigation if it is disinfected properly.

Pollutant removal from municipal wastewater employing baffled subsurface flow and integrated surface flow-floating treatment wetlands

This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland units (of the hybrid system) included organic, inorganic media, and were planted with nineteen types of macrophytes. The wetland train was operated under hydraulic loading fluctuation and seasonal variation. The performance analyses (across the wetland units) illustrated simultaneous denitrification and organics removal rates in the first stage vertical flow wetland, due to organic carbon leaching from the employed organic media. Higher mean organics removal rates (656.0 g COD/(m2·day)) did not completely inhibit nitrification in the first stage vertical flow system; such pattern could be linked to effective utilization of the trapped oxygen, as the flow was directed throughout the media by the baffle walls. Second stage horizontal flow wetland showed enhanced biodegradable organics removal, which depleted organic carbon availability for denitrification. The final stage integrated wetland system allowed further nitrogen removal from wastewater, via nutrient uptake by plant roots (along with nitrification), and generation of organic carbon (by the dead macrophytes) to support denitrification. The system achieved higher E. coli mortality through protozoa predation, E. coli oxidation, and destruction by UV radiation. In general, enhanced pollutant removal efficiencies as demonstrated by the structurally modified hybrid wetland system signify the necessity of such modification, when operated under adverse conditions such as: substantial input organics loading, hydraulic loading fluctuation, and seasonal variation.

Performance of six multi-stage hybrid wetland systems for treating high-content wastewater in the cold climate of Hokkaido, Japan

The performance of six multi-stage hybrid wetland systems, which were designed and constructed for treating high-content wastewater, was evaluated in the cold climate of Hokkaido, northern Japan. The systems were designed to treat four kinds of wastewater: dairy wastewater (three systems, average inflow 4.9–46.6m3d−1, average inflow content 2400–5000mgCODl−1, 2–5 years of operation); wastewater from a pig farm, including liquid food washing wastewater (one system, 4.1m3d−1, 9500mgCODl−1, 2 years of operation); wastewater from potato starch processing (one system, 5.4–13.3m3d−1, 24,000–54,000mgCODl−1, 2 years of operation); and wastewater containing pig farm swine urine (one system, 16.9m3d−1, 10,100mgCODl−1, 1 year operation). Our systems were composed of three to four vertical (V) flow beds with self-priming siphons and surface partitions and no or one horizontal (H) flow bed (total of three to five beds). In some V flow beds, treated effluents were recirculated (Vr) through the inlet to improve performance, mainly during the growing season. The total bed area was 168–2151m2. Mean annual temperature was 5–8°C at all locations. To overcome clogging due to the high load in a cold climate, we applied a safety bypass structure and floating cover material (Supersol: lightweight porous glass) to the V flow beds. The safety bypass structure and floating cover material helped to prevent clogging and freezing and maintained dry conditions and abundant growth of reeds and earthworms. The average purification rates were 70–96% for chemical oxygen demand (COD), 39–90% for total nitrogen (TN), 36–82% for NH4–N, and 70–93% for total phosphorous (TP). Calculated average oxygen transfer rates (OTRs) were 16–99gO2m−2d−1. OTRs increased in proportion to influent load, and the OTR value was Vr>V>H. Recirculating the treated effluents was expected to enhance removal of nitrogen in V flow beds mainly by a combination of nitrification and denitrification. By treating higher organic loads per area without clogging, it was possible to minimize the area and cost of treating high-content wastewater. However, more data are needed concerning load and OTR to design a more efficient multi-stage wetland system.

A lab-scale study of constructed wetlands with sugarcane bagasse and sand media for the treatment of textile wastewater

This paper reports the pollutant removal efficiencies of two lab-scale hybrid wetland systems treating a textile wastewater. The two systems had identical configurations, each consisting of a vertical flow (VF) and a horizontal flow (HF) wetland that were filled with organic sugarcane bagasse and sylhet sand as the main media. The systems were operated under high hydraulic loading (HL) (566–5660mm/d), and inorganic nitrogen (254–508gN/m2d) and organics loadings (9840–19680g COD/m2d and 2154–4307g BOD5/m2d). Simultaneous removals of BOD5 (74–79%) and ammonia (59–66%) were obtained in the first stage VF wetlands, demonstrating the efficiency of the media for oxygen transfer to cope with the high pollutant loads. The organic carbon (C) content of sugarcane bagasse facilitated denitrification in the VF wetlands. Second stage HF wetlands provided efficient color removal under predominantly anaerobic condition. Overall, the wetland systems showed stable removal performances under high, and unsteady, pollutant loadings.