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15 pages, 3467 KiB

Open AccessArticle

Flume Experiments for Optimizing the Hydraulic Performance of a Deep-Water Wetland Utilizing Emergent Vegetation and Obstructions

by Shang-Shu Shih, Shang-Shang Hong and Tsang-Jung Chang

Water 2016, 8(6), 265; https://doi.org/10.3390/w8060265 - 21 Jun 2016

Cited by 11 | Viewed by 6141

Abstract

Constructed ponds and wetlands are widely used in urban areas for stormwater management, ecological conservation, and pollution treatment. The treatment efficiency of these systems is strongly related to the hydrodynamics and hydraulic residence time. In this study, we developed a physical model and [...] Read more.

Constructed ponds and wetlands are widely used in urban areas for stormwater management, ecological conservation, and pollution treatment. The treatment efficiency of these systems is strongly related to the hydrodynamics and hydraulic residence time. In this study, we developed a physical model and used rhodamine-WT as a tracer to conduct flume experiments. An equivalent Reynolds number was assumed, and the flume was a 1/25-scale model. Emergent obstructions (EOs), submerged obstructions (SOs), and high- and low-density emergent vegetation were placed along the sides of the flume, and 49 tracer tests were performed. We altered the density, spatial extent, aspect ratio, and configurations of the obstructions and emergent vegetation to observe changes in the hydraulic efficiency of a deep-water wetland. In the cases of low-aspect-ratio obstructions, the effects of the EOs on the hydraulic efficiency were significantly stronger than those of the SOs. In contrast, in the cases of high-aspect-ratio obstructions, the improvement effects of the EOs were weaker than those of the SOs. The high-aspect-ratio EOs altered the flow direction and constrained the water conveyance area, which apparently caused a short-circuited flow phenomenon, resulting in a decrease in hydraulic efficiency. Most cases revealed that the emergent vegetation improved the hydraulic efficiency more than the EOs. The high-density emergent vegetation (HEV) improved the hydraulic efficiency more than the low-density emergent vegetation (LEV). Three cases involving HEV, two cases involving LEV, and one case involving EOs attained a good hydraulic efficiency (λ > 0.75). To achieve greater water purification, aquatic planting in constructed wetlands should not be overly dense. The HEV configuration in case 3-1 achieved optimum hydraulic performance for compliance with applicable water treatment standards. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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20 pages, 2643 KiB

Open AccessArticle

Evaluation of Phytodesalination Potential of Vegetated Bioreactors Treating Greenhouse Effluent

by Soheil Fatehi Pouladi, Bruce C. Anderson, Brent Wootton and Lloyd Rozema

Water 2016, 8(6), 233; https://doi.org/10.3390/w8060233 - 31 May 2016

Cited by 13 | Viewed by 6194

Abstract

The dissolved salt ions that are not absorbed during irrigation of greenhouse crops are gradually accumulated in the nutrient solution resulting in levels of salinity high enough to damage the crops. This water salinity presents operational and environmental challenges as the nutrient-rich greenhouse [...] Read more.

The dissolved salt ions that are not absorbed during irrigation of greenhouse crops are gradually accumulated in the nutrient solution resulting in levels of salinity high enough to damage the crops. This water salinity presents operational and environmental challenges as the nutrient-rich greenhouse effluent should be discharged to the environment when deemed unsuited for irrigation. In this pilot-scale study, the potential of passive salt reduction (phytodesalination) in gravel and wood-chip flow-through reactors was evaluated using seven plant species including Schoenoplectus tabernaemontani, Andropogon gerardii, Typha angustifolia, Elymus canadensis, Panicum virgatum, Spartina pectinata and Distichlis spicata along with an unplanted control reactor. While the unplanted system outperformed the planted units with gravel media, the wood-chip bioreactors with S. tabernaemontani and S. pectinata improved the greenhouse effluent reducing the solution conductivity (EC) by a maximum of 15% (average = 7%). S. tabernaemontani and D. spicata showed higher accumulated contents of Na⁺ and Cl⁻ in comparison with T. angustifolia and S. pectinata. Overall, S. tabernaemontani was selected as the most capable species in the wood-chip bioreactors for its better salt management via EC reduction and salt accumulation. It was however concluded that further treatment would be required for the greenhouse effluent to meet the stringent irrigation water quality guidelines in order not to pose any adverse effects on sensitive crops. Finally, the present hydraulic residence time (HRT = 3.7 days) and the solution salinity concentration were identified as the potential factors that may be limiting the efficiency of plant salt uptake, emphasizing the need for conducting more research on the optimization and enhancement of passive desalination systems for the greenhouse effluent. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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14 pages, 1742 KiB

Open AccessArticle

Performance of a Constructed Wetland and Pretreatment System Receiving Potato Farm Wash Water

by Vera Bosak, Andrew VanderZaag, Anna Crolla, Christopher Kinsley and Robert Gordon

Water 2016, 8(5), 183; https://doi.org/10.3390/w8050183 - 29 Apr 2016

Cited by 27 | Viewed by 6884

Abstract

Many potato processors require on-farm washing of potatoes, creating large quantities of wastewater that requires treatment, starting in the fall until the end of the potato storage period in mid-summer. We studied the treatment of wastewater from a potato farm in Ontario, Canada, [...] Read more.

Many potato processors require on-farm washing of potatoes, creating large quantities of wastewater that requires treatment, starting in the fall until the end of the potato storage period in mid-summer. We studied the treatment of wastewater from a potato farm in Ontario, Canada, using a system of pretreatment (sedimentation, aeration) followed by a surface-flow wetland with a dense growth of cattails (Typha sp.). The raw wastewater had high average concentrations of 5-day biochemical oxygen demand (BOD₅; 1113 mg·L⁻¹), total suspended solids (TSS; 4338 mg·L⁻¹), total nitrogen (TN; 311 mg·L⁻¹) and total phosphorus (TP; 42.5 mg·L⁻¹). Due to high influent loads, the pretreatment was enlarged during annual sediment cleaning at the end of Year 1 (Y1), which increased the hydraulic retention time and delayed the seasonal onset of wetland loading from winter in Y1 to spring in Year 2 (Y2). Total concentration reduction for the treatment system (pretreatment + wetland) in Y2 was 96% BOD₅, 99% TSS, 86% TN and 90% TP; and in Y1 was 79% BOD₅, 97% TSS, 62% TN and 54% TP. Overall, the best treatment in both the pretreatment and the wetland was seen in spring months. The enlarged pretreatment system enabled seasonal loading of the wetland during the spring and summer, which facilitated improved treatment performance. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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18 pages, 2371 KiB

Open AccessArticle

Decline in Performance of Biochemical Reactors for Sulphate Removal from Mine-Influenced Water is Accompanied by Changes in Organic Matter Characteristics and Microbial Population Composition

by Parissa Mirjafari and Susan A. Baldwin

Water 2016, 8(4), 124; https://doi.org/10.3390/w8040124 - 30 Mar 2016

Cited by 12 | Viewed by 6584

Abstract

Successful long-term bioremediation of mining-influenced water using complex organic matter and naturally-occurring microorganisms in sub-surface flow constructed wetlands requires a balance between easily and more slowly degrading material. This can be achieved by combining different types of organic materials. To provide guidance on [...] Read more.

Successful long-term bioremediation of mining-influenced water using complex organic matter and naturally-occurring microorganisms in sub-surface flow constructed wetlands requires a balance between easily and more slowly degrading material. This can be achieved by combining different types of organic materials. To provide guidance on what mixture combinations to use, information is needed on how the ratio of labile to recalcitrant components affects the degradation rate and the types of microbial populations supported. To investigate this, different ratios of wood and hay were used in up-flow column bioreactors treating selenium- and sulphate-containing synthetic mine-influenced water. The degradation rates of crude fibre components appeared to be similar regardless of the relative amounts of wood and hay. However, the nature of the degradation products might have differed in that those produced in the hay-rich bioreactors were more biodegradable and supported high sulphate-reduction rates. Microorganisms in the sulphate-reducing and cellulose-degrading inocula persisted in the bioreactors indicating that bio-augmentation was effective. There was a shift in microbial community composition over time suggesting that different microbial groups were involved in decomposition of more recalcitrant material. When dissolved organic carbon (DOC) was over-supplied, the relative abundance of sulphate-reducers was low even through high sulphate-reduction rates were achieved. As DOC diminished, sulphate-reducers become more prevalent and their relative abundance correlated with sulphate concentrations rather than sulphate-reduction rate. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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9 pages, 1215 KiB

Open AccessArticle

Salts Removal from Synthetic Solution-Potash Brine by Non-Planted Constructed Wetlands

by Warawut Chairawiwut, Dena W. McMartin and Shahid Azam

Water 2016, 8(4), 113; https://doi.org/10.3390/w8040113 - 24 Mar 2016

Cited by 9 | Viewed by 5038

Abstract

Four pilot-scale non-planted constructed wetlands (CWs) were employed to study the fate and transport of the two dominant chloride salts contained in brine resulting from solution mining activities in the potash industry. The simulated brine contained a 10:1 ratio of NaCl:KCl based on [...] Read more.

Four pilot-scale non-planted constructed wetlands (CWs) were employed to study the fate and transport of the two dominant chloride salts contained in brine resulting from solution mining activities in the potash industry. The simulated brine contained a 10:1 ratio of NaCl:KCl based on authentic brine characteristics. The multi-layer soils functioned as a main salt filtering component comprising of Regina Clay, sand and gravels. The CW systems were operated in three batches of 16 days (experiments 1–3). K⁺ ions were removed by 92% (4.6 mg/L) from the effluent, while Cl⁻ and Na⁺ were removed in lower proportions of 51% (85.3 mg/L) and 45% (53.2 mg/L), respectively. Over time, the retained quantities of the three target salt ions decreased, indicating that clay sorption capacity may have been reached. This study demonstrated that Regina Clay has substantial sorbent capacity for salt ions contained in simulated potash brine solution. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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14 pages, 2485 KiB

Open AccessArticle

The Potential Growth of Sugarcane in Constructed Wetlands Designed for Tertiary Treatment of Wastewater

by Dina M. R. Mateus, Mafalda M. N. Vaz, Isabel Capela and Henrique J. O. Pinho

Water 2016, 8(3), 93; https://doi.org/10.3390/w8030093 - 10 Mar 2016

Cited by 15 | Viewed by 8089

Abstract

This research was conducted to evaluate the feasibility of using the bioenergy crop Saccharum officinarum (sugarcane) as vegetation and mineral wastes for filling in constructed wetlands (CWs) designed for the removal of nutrients from wastewater. Four horizontal subsurface flow pilot-scale CWs were monitored [...] Read more.

This research was conducted to evaluate the feasibility of using the bioenergy crop Saccharum officinarum (sugarcane) as vegetation and mineral wastes for filling in constructed wetlands (CWs) designed for the removal of nutrients from wastewater. Four horizontal subsurface flow pilot-scale CWs were monitored during one year: two filled with fragmented limestone and two with clay brick fragments, two planted and two unplanted controls. Sugarcane stalk height, diameter and foliar area were evaluated during the plant-cane cycle along with total phosphorus (TP) and total nitrogen (TN) removal efficiencies from the wastewater. Sugarcane biomass production was 107 ton/ha for the brick fragments filled CW and 67 ton/ha for the fragmented limestone filled CW. Planted CWs show better nutrient removal efficiencies than the unplanted. Planted CW filled with brick fragments show average efficiencies of 77% ± 4% for TP and 60% ± 12% for TN, and planted CW filled with fragmented limestone 68% ± 3% for TP and 58% ± 7% for TN. Results showed that the use of sugarcane as CW vegetation is a viable alternative to produce a bioethanol raw-material without the use of arable land and irrigation water, while it maintains the wastewater treatment capabilities of CWs. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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14 pages, 807 KiB

Open AccessArticle

Efficiency of a Horizontal Sub-Surface Flow Constructed Wetland Treatment System in an Arid Area

by Abeer Albalawneh, Tsun-Kuo Chang, Chi-Su Chou and Sireen Naoum

Water 2016, 8(2), 51; https://doi.org/10.3390/w8020051 - 5 Feb 2016

Cited by 26 | Viewed by 6471

Abstract

The main objective of this study was to evaluate the performance and treatment efficiency of the Horizontal Sub-Surface Flow Constructed Wetland treatment system (HSF-CW) in an arid climate. Seventeen sub-surface, horizontal-flow HSF-CW units have been operated for approximately three years to improve the [...] Read more.

The main objective of this study was to evaluate the performance and treatment efficiency of the Horizontal Sub-Surface Flow Constructed Wetland treatment system (HSF-CW) in an arid climate. Seventeen sub-surface, horizontal-flow HSF-CW units have been operated for approximately three years to improve the quality of partially-treated municipal wastewater. The studied design parameters included two sizes of volcanic tuff media (i.e., fine or coarse), two different bed dimensions (i.e., long and short), and three plantation types (i.e., reed, kenaf, or no vegetation as a control). The effluent Biological Oxygen Demand (BOD₅), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), and phosphorus from all of the treatments were significantly lower as compared to the influent and demonstrated a removal efficiency of 55%, 51%, 67%, and 55%, respectively. There were significant increases in Electrical Conductivity (EC), sulfate, and calcium in the effluent of most HSF-CWs due to evaporative concentration and mineral dissolution from the media. The study suggests that unplanted beds with either fine or coarse media are the most suitable combinations among all of the studied designs based on their treatment efficiency and less water loss in arid conditions. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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10 pages, 721 KiB

Open AccessArticle

Effect of Plant Harvesting on the Performance of Constructed Wetlands during Summer

by Zhongchen Yang, Qian Wang, Jian Zhang, Huijun Xie and Suping Feng

Water 2016, 8(1), 24; https://doi.org/10.3390/w8010024 - 16 Jan 2016

Cited by 37 | Viewed by 6539

Abstract

Plants can remove pollutants through direct absorption and by providing habitats for microbes to stimulate their activities. The aboveground plant biomass is usually harvested to remove pollutants absorbed in plant tissues. However, the effect of plant harvesting during summer on the performance of [...] Read more.

Plants can remove pollutants through direct absorption and by providing habitats for microbes to stimulate their activities. The aboveground plant biomass is usually harvested to remove pollutants absorbed in plant tissues. However, the effect of plant harvesting during summer on the performance of constructed wetlands and microbial abundance is unclear. In this study, three types of microcosms were set up, including: cleared group (both shoots and roots were harvested), harvested group (only shoots were harvested) and unharvested group. The concentrations of ammonia nitrogen and chemical oxygen demand in the effluent of the harvested group were the lowest. The nitrogen mass balance showed that summer harvesting improved nitrogen absorbance by plants, which was 1.24-times higher than that in the unharvested group. Interestingly, the other losses were taken up by the highest amounts in the cleared group, which were 1.66- and 3.72-times higher than in the unharvested and harvested group, respectively. Quantitative polymerase chain reaction revealed that harvesting of shoots during summer increased the microbial abundance. Additionally, Proteobacteria was the dominant phylum among all bacteria according to pyrosequencing analysis. These results indicate that harvesting of shoots during summer has positive effects on pollutant removal and microbial abundance. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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Review

Jump to: Research

14 pages, 237 KiB

Open AccessReview

Constructed Wetlands for Agricultural Wastewater Treatment in Northeastern North America: A Review

by Eric R. Rozema, Andrew C. VanderZaag, Jeff D. Wood, Aleksandra Drizo, Youbin Zheng, Ali Madani and Robert J. Gordon

Water 2016, 8(5), 173; https://doi.org/10.3390/w8050173 - 27 Apr 2016

Cited by 45 | Viewed by 9717

Abstract

Constructed wetlands (CW) are a treatment option for agricultural wastewater. Their ability to adequately function in cold climates continues to be evaluated as they are biologically active systems that depend on microbial and plant activity. In order to assess their performance and to [...] Read more.

Constructed wetlands (CW) are a treatment option for agricultural wastewater. Their ability to adequately function in cold climates continues to be evaluated as they are biologically active systems that depend on microbial and plant activity. In order to assess their performance and to highlight regional specific design considerations, a review of CWs in Eastern Canada and the Northeastern USA was conducted. Here, we synthesize performance data from 21 studies, in which 25 full-scale wetlands were assessed. Where possible, data were separated seasonally to evaluate the climatic effects on treatment performance. The wastewater parameters considered were five-day biochemical oxygen demand (BOD₅), total suspended solids (TSS), E. coli, fecal coliforms, total Kjeldahl nitrogen (TKN), ammonia/ammonium (NH₃/NH₄⁺-N), nitrate-nitrogen (NO₃⁻-N), and total phosphorus (TP). Average concentration reductions were: BOD₅ 81%, TSS 83%, TKN 75%, NH₄⁺-N 76%, NO₃⁻-N 42%, and TP 64%. Average log reductions for E. coli and fecal coliforms were 1.63 and 1.93, respectively. Average first order areal rate constants (k_a, m·y⁻¹) were: BOD₅ 6.0 m·y⁻¹, TSS 7.7 m·y⁻¹, E. coli 7.0 m·y⁻¹, fecal coliforms 9.7 m·y⁻¹, TKN 3.1 m·y⁻¹, NH₄⁺-N 3.3 m·y⁻¹, NO₃⁻-N 2.5 m·y⁻¹, and TP 2.9 m·y⁻¹. In general, CWs effectively treated a variety of agricultural wastewaters, regardless of season. Full article

(This article belongs to the Special Issue Constructed Wetlands Systems and Management)

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