Specialist Group on Use of Macrophytes in Water Pollution ... - IWA

APPLICATION OF CONSTRUCTED WETLAND FOR CONTROLLING
LEACHATE POLLUTION FROM SOLID WASTE DISPOSAL
Chart Chiemchaisri
Department of Environmental Engineering/National Center of Excellence for Environmental
and Hazardous Waste Management, Faculty of Engineering, Kasetsart University, Bangkok
10900, Thailand
An investigation in Thailand is focusing on the application of constructed wetland for direct
treatment of leachate at municipal solid waste disposal site. The main purpose of treatment
was to reduce the organic concentration in leachate to an acceptable concentration so that it
can be further utilize for irrigation on the landfill top soil. Two configurations of constructed
wetland were tested, i.e. horizontal sub-surface flow (HSF, Figure 1) and vertical flow (VF)
types. Cattail was used as the vegetation in both systems. They were applied for primary
treatment of young leachate as well as post treatment for stabilized leachate. In each case, the
hydraulic loading rate (HLR) is varied between 0.01-0.056 m 3 /m 2 .d, equivalent to hydraulic
retention time (HRT) in range of 28 and 5 days.
Pollutant removal efficiencies in constructed wetland
Applied leachate had COD concentration of about 3,000-5,000 mg/l with BOD/COD ratio of
0.6-0.7 and 0.05-0.1 for young and stabilized leachate respectively. In HSF and VF systems
treating young leachate, high organic removal of more than 90% was achieved up to HLR of
0.028 m 3 /m 2 .d. In stabilized leachate case, moderate organic removal efficiencies were
achieved. TKN removal was higher in VF (60-70%) as compared to HSF system (40-50%).
Temporal accumulation of oxidized nitrogen was observed at high nitrogen loading condition
(from stabilized leachate) causing some death of plant (Figure 2). Moderate nitrogen removal
efficiencies was achieved at HLR up to 28 m 3 /m 2 .d for stabilized leachate where influent
TKN concentration was controlled at about 100-300 mgL -1 .
Gravel
Influent
Coarse sand
Figure 1 Schematic of HSF constructed wetland system
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IWA <strong>Specialist</strong> <strong>Group</strong> on Use of Macrophytes in Water Pollution Control: Newsletter No. 35 15
3 m
Effluent
0.40 m
0.8 m
1.3 m