Thesis - faculty.ait.ac.th - Asian Institute of Technology

These systems are land intensive whilst conventional systems are energy intensive. Typical
natural systems used for landfill leachate treatment include wetlands, leachate recirculation
and aquatic systems.
Leachate Re-circulation
Moisture addition by means of rain infiltration and leachate recirculation is critical to
the stabilization of landfill waste, enhancement of gas production, improvement of leachate
quality, reducing long-term environmental consequences and liability of waste storage and
improving economic viability of waste storage. The landfill effectively acts as an
uncontrolled anaerobic filter and promotes methanogenic conditions for the enhancement
of organic degradation (Knox, 1985; Strachan, et al., 2000).
The in situ treatment of leachate by recycling the leachate to the landfill reduces the
time required for biological stabilization of the readily biodegradable leachate constituents
and increases the rate of biostablization of the leachate. Re-circulated leachate reduces the
stabilization time from 15 to 20 years to 2 to 3 years (Pohland and Harper, 1985). It can be
suggested that by managing the moisture content within the landfill, the rate and
characteristics of the leachate generated can be controlled by diluting the inhibitory and
refractory compounds. Further, seed, nutrients and buffers can be added to supplement the
biological activity within the landfill and thus, create an engineered bioreactor in the
landfill. Whilst this is effective in removing the organic constituents in the leachate, the
landfill bioreactor has been demonstrated as being ineffective in treating elevated ammonia
concentrations.
Pohland (1972, 1975), Leckie, et al. (1975, 1979) and Pohland, et al. (1990),
performed leachate recirculation studies. The results indicated a rapid decline in COD due
to the active development of anaerobic methane forming bacteria in the fill, which was
enhanced by recirculation of leachate and seeding with municipal sewage sludge. The
COD reduction showed a similar trend as reduction in BOD, TOC, VFA, phosphate,
ammonia-nitrogen and TDS.
Reed Beds
A reed bed system (Root zone treatment) can be designed to treat leachate. The
wastewater to be treated in root zone treatment passes through the rhizomes of the common
reed in a shallow contained bed of permeable medium. The rhizomes introduce oxygen
into the bed and as effluent percolates through it; microbial communities become
established at the roots and degrade contaminants. Nutrients such as nitrogen and
phosphorus may also be removed directly as the reeds utilise them for growth. Reed beds
cannot be used as a primary treatment for leachate since they are poor at removing
ammonia even from a sewage having a low concentration of 30 mg/L. Further, the
accumulation of heavy metals within the bed may affect rhizome growth and bed
permeability. Reed beds are therefore generally used as a polishing step for leachate
treatment (Robinson, et al., 1992).
2.8.5 Co-Treatment with Municipal Wastewater
Current leachate treatment practice includes discharge of leachate into municipal
wastewater (MWW) drains followed by the treatment of both domestic wastewater and
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