An investigation of the dual co-disposal of a phenolic wastewater and activated sewage sludge with refuse and treatment of high-strength leachate obtained from a closed co-disposal landfill.
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Date
1996
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Abstract
Co-disposal with refuse in a controlled landfill is the cheapest option for the disposal of
hazardous waste and, if carefully controlled, can be an effective treatment option. In this
present study a high-strength phenolic wastewater and activated sewage sludge were co-disposed
with refuse. The effectiveness of phenol catabolism at two organic loading rates
(500mgt1 and 1000mgtl) was assessed in the presence of various co-disposal strategies.
Leachate recycle at the lower phenol organic loading rate was found to facilitate the
greatest rate of phenol catabolism. Despite the effective removal of phenol, however,
leachate recycle promoted the production of high concentrations of ammoniacal-N and
hydrogen sulphide. At the higher phenol organic loading rate, recirculation was ineffective
in reducing the residual phenol concentration due to inhibition of the phenol-catabolisers.
Microcosms operated with single elution and batch co-disposal strategies at both phenol
organic loading rates resulted in serious detrimental effects on the refuse fermentation and
subsequent leachate quality.
A high-strength leachate obtained from a closed co-disposal site was characterised to
determine its chemical composition and was assessed for its susceptibility to biological
treatment. If carefully controlled, co-disposal sites should produce leachates which differ
little in quality to those produced by municipal waste sites. The exceptionally high specific
conductivity of the leachate used in this present study was, however, uncharacteristic of
a leachate from a municipal waste site. The leachate required dilution to 25 % (v/v) before
responding to aerobic biological treatment due to the presence of bactericidal/bacteriostatic
components. Anaerobic treatment was ineffective even at a final dilution of 10% (v/v) of
the original due to the inhibition of methanogenesis caused indirectly by the high
concentration of sulphate in the leachate. Following phosphate addition, aerobic biological
treatment effected a significant reduction in the chemical oxygen demand (COD) but did
not reduce the ammoniacal-N concentration. Scaling and precipitation occurred following
addition of the phosphate, and although these did not affect the biological process they can
cause operational problems in full-scale leachate treatment plants. Ion exchange, with soil,
and lime treatment, were, therefore, considered for their ability to reduce the inorganic
content of the leachate prior to biological treatment. However, these particular pretreatments were unsuitable due to their ineffectiveness to
reduce calcium, the main inorganic element involved in scaling, to an acceptable
concentration.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.
Keywords
Sanitary landfills--Leaching., Sewage--Purification--Phenol removal., Leachate--Analysis., Refuse and refuse disposal., Waste disposal in the ground., Theses--Microbiology.