Application of constructed wetlands to treat some toxic wastewaters under tropical conditions

This study evaluated the potential of a free water surface constructed wetland system in treating some toxic wastewaters (i.e. phenolic and heavy metals). In a temperature range of 22–30°C, the constructed wetland units, whose hydraulic retention times (HRT) were 5–7 days, could remove more than 99% of the input phenol when they were operated at or below the organic loading rates (OLR) and influent phenol concentrations of 270 kg COD/(ha.d) and 400 mg/l, respectively. The effluent dissolved oxygen (DO) levels were 4–7 mg/l at OLR of 40–140 kg COD/(ha.d), but these DO levels decreased to 0.2–0.3 mg/l when the OLR were increased to 165–270 kg COD/(ha.d). Under similar operating conditions, the constructed wetland units could remove more than 99% of the applied chromium (Cr) and nickel (Ni), when either the Cr or Ni influent concentrations were 1–50 mg/l. The phenolic and heavy metal compounds were found to accumulate mostly at the roots of Typha, followed by the stems and leaves.

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Community Wastewater Treatment with Attached Growth Assisted Constructed Wetland Reactor

IRA-International Journal of Technology & Engineering (ISSN 2455-4480) ◽

10.21013/jte.icsesd201731 ◽

2017 ◽

Vol 7 (2 (S)) ◽

pp. 327

Author(s):

Nitin Ingole ◽

Mangesh Gulhane

Keyword(s):

Wastewater Treatment ◽

Constructed Wetlands ◽

Constructed Wetland ◽

Operating Conditions ◽

Laboratory Scale ◽

Scale Model ◽

Reactor Model ◽

Attached Growth ◽

Growth System ◽

Wetland System

Constructed wetlands are systems of artificial wastewater treatment which consists of shallow ponds or channels that have been planted with aquatic plants. The treatment is based on the natural, biological, physical and chemical treatment of wastewater. The technique is reported to be cost effective as compared to other methods. The constructed wetlands have impermeable clay or synthetic coatings and artificial structures for controlling the direction of flow, liquid retention time and the water level. However, there are certain limitations of constructed wetland system, which need improvement for its wide adoptability. As such the effort was made to assist the constructed wetland system with attached growth system with the aim to design an economical and user friendly waste water treatment option for the small community. The laboratory scale model was fabricated using GI sheet of thickness 0.5 mm. The overall capacity of the model was 275 L. The laboratory scale reactor model consisted of four compartments out of which first three compartments were based on attached growth system and the fourth compartment acted as constructed wetland reactor. All the three compartments were packed with different types of artificial, semi-artificial and natural media. The fourth compartment consisted of media packed from bottom as aerocon stone layers 03 in numbers followed by snail shell, followed by a soil layer of 80 mm thick which holds the plants in rows. The reactor was operated as continuous flow reactor with varying detention time and change of different type of media packed in the reactor. The performance of Customized Constructed Wetland reactor was observed under various operating conditions for removal of BOD, COD and TS parameters. The paper presents the details regarding the development of the reactor model, operation of the reactor model and results obtained during the course of study. The paper also cover the discussion regarding the improved performance of reactor noted during the study and adoptability of the developed reactor model for community waste treatment.

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Flow Pattern Analysis of Constructed Wetlands Treating Landfill Leachate

Water Science & Technology ◽

10.2166/wst.1999.0176 ◽

1999 ◽

Vol 40 (3) ◽

pp. 309-315 ◽

Cited By ~ 2

Author(s):

Jonathan K. Rash ◽

Sarah K. Liehr

Keyword(s):

Constructed Wetlands ◽

Vertical Mixing ◽

Subsurface Flow ◽

Free Water ◽

Chemical Reactor ◽

Operating Conditions ◽

Conservative Tracer ◽

Residence Time Distributions ◽

Physical Barriers ◽

Interior Points

Three series of tracer studies were performed on three constructed wetlands at the New Hanover County Landfill near Wilmington, North Carolina, USA. One vegetated free water surface wetland (FWS-R), one vegetated subsurface flow wetland (SSF-R), and one unvegetated control subsurface flow wetland (SSF-C) were studied. A conservative tracer, lithium chloride, was used to study the chemical reactor behavior of these wetlands under normal operating conditions. Results indicated that short-circuiting is quite common in SSF wetlands, while FWS wetlands are well-mixed and not as subject to short-circuiting. These results were obtained from and reinforced with tracer measurements at interior points in these wetlands, analysis of residence time distributions from two different formulations, and the construction of residence volume distributions. The short-circuiting in the SSF wetlands can be attributed to the following: (1) Vertical mixing is inhibited by a combination of physical barriers and density gradients caused by rainfall and runoff dilution of the upper layer; and (2) Leachate is drawn from the bottom of the wetland, causing it to further prefer a flow path along the bottom.

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Constructed wetland for water quality improvement: a case study from Taiwan

Water Science & Technology ◽

10.2166/wst.2010.492 ◽

2010 ◽

Vol 62 (10) ◽

pp. 2408-2418 ◽

Cited By ~ 9

Author(s):

C. Y. Wu ◽

J. K. Liu ◽

S. H. Cheng ◽

D. E. Surampalli ◽

C. W. Chen ◽

...

Keyword(s):

Water Quality ◽

Wastewater Treatment ◽

Constructed Wetlands ◽

Constructed Wetland ◽

Water Reuse ◽

Oxygen Demand ◽

Sediment Oxygen Demand ◽

Nucleotide Sequence Analysis ◽

Sediment Samples ◽

Wetland System

In Taiwan, more than 20% of the major rivers are mildly to heavily polluted by domestic, industrial, and agricultural wastewaters due to the low percentage of sewers connected to wastewater treatment plants. Thus, constructed or engineered wetlands have been adopted as the major alternatives to clean up polluted rivers. Constructed wetlands are also applied as the tertiary wastewater treatment systems for the wastewater polishment to meet water reuse standards with lower operational costs. The studied Kaoping River Rail Bridge Constructed Wetland (KRRBCW) is the largest constructed wetland in Taiwan. It is a multi-function wetland and is used for polluted creek water purification and secondary wastewater polishment before it is discharged into the Kaoping River. Although constructed wetlands are feasible for contaminated water treatment, wetland sediments are usually the sinks for organics and metals. In this study, water and sediment samples were collected from the major wetland basins in KRRBCW. The investigation results show that more than 97% of total coliforms (TC), 55% of biochemical oxygen demand (BOD), and 30% of nutrients [e.g. total nitrogen (TN), total phosphorus (TP)] were removed via the constructed wetland system. However, results from the sediment analyses show that wetland sediments contained high concentrations of metals (e.g. Cu, Fe, Zn, Cr, and Mn), organic contents (sediment oxygen demand = 1.7 to 7.6 g O2/m2 d), and nutrients (up to 18.7 g/kg of TN and 1.22 g/kg of TN). Thus, sediments should be excavated periodically to prevent the release the pollutants into the wetland system and causing the deterioration of wetland water quality. Results of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis reveal that a variation in microbial diversity in the wetland systems was observed. Results from the DGGE analysis indicate that all sediment samples contained significant amounts of microbial ribospecies, which might contribute to the carbon degradation and nitrogen removal. Gradual disappearance of E. coli was also observed along the flow courses through natural attenuation mechanisms.

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The effect of a vertical flow filter bed on a hybrid constructed wetland system

Water Science & Technology ◽

10.2166/wst.2005.0305 ◽

2005 ◽

Vol 51 (9) ◽

pp. 137-144 ◽

Cited By ~ 9

Author(s):

A. Noorvee ◽

E. Põldvere ◽

Ü. Mander

Keyword(s):

Constructed Wetland ◽

Flow System ◽

Subsurface Flow ◽

Oxygen Demand ◽

Vertical Flow ◽

Efficient Removal ◽

Loading Rates ◽

Purification Efficiency ◽

Wetland System ◽

Filter Bed

Data from 18 sampling wells in Kodijärve horizontal subsurface flow (HSSF) constructed wetland (CW) (South Estonia) is presented and differences in purification efficiencies inside the HSSF CW are calculated. Temporarily anaerobic conditions in the Kodijärve HSSF system did not allow efficient removal of BOD7, NH4-N, Ntot and Ptot. In 2002 a vertical subsurface flow filter was constructed to enhance aeration. The design of the system was based simply on the oxygen demand of the wastewater and on the aeration potential of vertical flow wetlands. The vertical flow system has shown satisfactory results. The purification efficiency of BOD7 in the Kodijärve CW has improved significantly and there has been a slight increase in purification efficiencies of NH4-N and Ntot. On the ohther hand, the removal efficiency of Ptot has decreased significantly. Although, the mass loading rates have increased, mass removal rates of all four parameters have improved significantly. Nevertheless, optimization of the constructed wetland system is essential in order to meet effluent standards during wintertime.

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Operation of a horizontal subsurface flow constructed wetland – Microbial fuel cell treating wastewater under different organic loading rates

Water Research ◽

10.1016/j.watres.2013.09.005 ◽

2013 ◽

Vol 47 (17) ◽

pp. 6731-6738 ◽

Cited By ~ 127

Author(s):

J. Villaseñor ◽

P. Capilla ◽

M.A. Rodrigo ◽

P. Cañizares ◽

F.J. Fernández

Keyword(s):

Fuel Cell ◽

Microbial Fuel Cell ◽

Constructed Wetland ◽

Subsurface Flow ◽

Organic Loading ◽

Loading Rates ◽

Subsurface Flow Constructed Wetland ◽

Horizontal Subsurface Flow

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Oxygen demand, nitrogen and copper removal by free-water-surface and subsurface-flow constructed wetlands under tropical conditions

Environment International ◽

10.1016/s0160-4120(01)00023-x ◽

2001 ◽

Vol 26 (5-6) ◽

pp. 425-431 ◽

Cited By ~ 49

Author(s):

P.E. Lim ◽

T.F. Wong ◽

D.V. Lim

Keyword(s):

Constructed Wetlands ◽

Water Surface ◽

Subsurface Flow ◽

Oxygen Demand ◽

Free Water ◽

Copper Removal ◽

Free Water Surface ◽

Tropical Conditions ◽

Subsurface Flow Constructed Wetlands ◽

Surface And Subsurface Flow

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Technical Note — The Use of a Very Large Constructed Sub-Surface Flow Wetland to Treat Glycol-Contaminated Stormwater from Aircraft De-Icing Operations

Water Quality Research Journal ◽

10.2166/wqrj.2002.053 ◽

2002 ◽

Vol 37 (4) ◽

pp. 785-792 ◽

Cited By ~ 7

Author(s):

James Higgins ◽

Michael Maclean

Keyword(s):

Constructed Wetlands ◽

Scale Up ◽

Free Water ◽

Technical Note ◽

Surface Flow ◽

Wetland Plants ◽

Design Parameters ◽

Management Options ◽

Marsh Type ◽

Wetland System

Abstract All of the pollutants found in stormwater runoff at airports, including surface and aircraft de-icing/anti-icing glycols, can be treated and removed to low levels in well-designed sub-surface flow (SSF) constructed wetland systems. There are two common forms of constructed wetlands used for pollution control: those where water flows over the surface among wetland plants (free water surface or marsh type wetlands); and SSF types where the wastewater flows below the normally dry surface of a gravel substrate in which the wetland plants grow. SSF wetlands have no open water to attract waterfowl and are particularly suitable for use at airports. Of the glycol used at Edmonton International Airport (EIA), 80 to 90% eventually entered surface runoff. Edmonton International Airport's operator, the Edmonton Regional Airports Authority (Edmonton Airports) evaluated a number of glycol management options, including constructed wetlands. As a result, a very large SSF wetland system was installed to handle glycol-contaminated stormwater. This paper reviews results of a feasibility study carried out to define design parameters and scale up kinetics for this wetland system, the detailed design that resulted, the SSF wetland's construction, and the start-up of the Edmonton facilities in August of 2000. It also compares the Edmonton wetland system with a similar facility at Heathrow Airport in the United Kingdom.

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Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions

Water Science & Technology ◽

10.2166/wst.2007.517 ◽

2007 ◽

Vol 56 (3) ◽

pp. 49-55 ◽

Cited By ~ 15

Author(s):

P. Gui ◽

R. Inamori ◽

M. Matsumura ◽

Y. Inamori

Keyword(s):

Plant Growth ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Constructed Wetlands ◽

Constructed Wetland ◽

Seasonal Changes ◽

Free Water ◽

Domestic Wastewater ◽

Pollutant Removal ◽

Gas Emissions

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.

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Assessment of classical surface organic loading design equations based on the actual performance of primary and secondary facultative ponds

Water Science & Technology ◽

10.2166/wst.2010.953 ◽

2010 ◽

Vol 61 (4) ◽

pp. 971-977 ◽

Cited By ~ 1

Author(s):

Sílvia C. Oliveira ◽

Marcos von Sperling

Keyword(s):

Performance Evaluation ◽

Hydraulic Retention Time ◽

Operating Conditions ◽

Empirical Equations ◽

Organic Loading ◽

Actual Performance ◽

Loading Rates ◽

Limit Value ◽

Classical Design ◽

Operational Aspects

This article presents results from a performance evaluation of 73 full-scale primary facultative ponds and 37 secondary facultative ponds in Brazil. The data were used to test the applicability of some classical design equations for recommended surface BOD loading rates. The empirical equations proposed by Mara in 1976 and 1987 and the equation developed by McGarry and Pescod in 1970 were evaluated. The loading and hydraulic operating conditions were also evaluated to support the analysis of the influence of the parameters surface BOD loading (Ls) and hydraulic retention time (HRT) on the performance of the ponds. The results showed that the design equations proposed by Mara showed good applicability for primary facultative ponds, representing good indicators of the limit value of loading rates to be applied on the units. But the secondary facultative ponds showed good and poor performances for all loading rates and the best ponds, in general, were not those which followed the design equations recommendation. Finally, the influence of the actual loading conditions on the ponds performance was very small and scattered, indicating that other unquantified design and operational aspects were playing an important role.

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