Long-term performance of subsurface-flow constructed wetlands treating Cd wastewater

2008 ◽  
Vol 43 (7) ◽  
pp. 765-771 ◽  
Author(s):  
Varangkana Visesmanee ◽  
Chongrak Polprasert ◽  
Preeda Parkpian
Keyword(s):  
Constructed Wetlands ◽  
Subsurface Flow ◽  
Subsurface Flow Constructed Wetlands ◽  
Long Term Performance ◽  
Term Performance

Reversing clogging in subsurface-flow constructed wetlands by hydrogen peroxide treatment: two case studies

2009 ◽  
Vol 59 (10) ◽  
pp. 2037-2046 ◽  
Author(s):  
Jaime Nivala ◽  
Diederik P. L. Rousseau
Keyword(s):  
Hydrogen Peroxide ◽  
Constructed Wetlands ◽  
Subsurface Flow ◽  
Pilot Scale ◽  
Hydrogen Peroxide Treatment ◽  
Negative Effect ◽  
Subsurface Flow Constructed Wetlands ◽  
Full Scale Tests ◽  
Wetland Cell

One of the most frequently encountered operational problems in subsurface-flow constructed wetlands is clogging. Traditionally, the restoration procedure is to remove the clogged gravel or sand and replace it with clean material. This method, while effective, is costly and may require sections of the facility to be taken offline for extended periods of time. Another common remediation strategy is to have a resting period for each wetland cell, although this is not an option for very small systems which often consist of only one treatment cell. Recently, a more radical approach has been tested on a number of lab-scale and pilot-scale setups which consists of an aggressive oxidation of organic matter by means of hydrogen peroxide (H2O2). Results indicate that after treatment, clogging was substantially reduced and that H2O2 did not appear to have a long-term negative effect on plants and biofilms. The outcomes of two full-scale tests are discussed in this paper.

Using constructed wetlands to treat subsurface drainage from intensively grazed dairy pastures in New Zealand

2003 ◽  
Vol 48 (5) ◽  
pp. 207-213 ◽  
Author(s):  
C.C. Tanner ◽  
M. Long Nguyen ◽  
J.P.S. Sukias
Keyword(s):  
New Zealand ◽  
Constructed Wetlands ◽  
Subsurface Drainage ◽  
Organic N ◽  
Nutrient Concentrations ◽  
Start Up ◽  
Catchment Areas ◽  
Long Term Performance ◽  
Term Performance

Performance data, during the start-up period, are presented for constructed wetlands treating subsurface drainage from dairy pastures in Waikato (rain-fed) and Northland (irrigated), North Island, New Zealand. The wetlands comprised an estimated 1 and 2% of the drained catchment areas, respectively. Nitrate concentrations were high in the drainage inflows at both sites (medians 10 g m-3 at Waikato and 6.5 g m-3 at Northland), but organic N was also an important form of N at Waikato (37% of TN). Comparison of wetland inflow and outflow nutrient concentrations showed overall nutrient reductions during passage through the wetlands for NO3-N (34 and 94% for medians, respectively), TN (56 and 33%, respectively), and DRP (80%, Northland only). Median NH4-N (both sites) and DRP (Waikato) concentrations showed apparent increases between the wetland inlets and outlets. However, a mass balance calculated for the 3 month preliminary monitoring periods showed substantial mass removal of DRP (80%) and all measured forms of N (NO3-N 78%, NH4-N 41%, Org-N 99.8% and TN 96%) in the Waikato wetland. Monitoring of these systems needs to be continued through a range of seasons and years to fully assess their long-term performance.

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