This study was carried out to gain knowledge of the degradation processes in an
anaerobic environment of pre-treated waste for different degrees of pre-treatment and the
evolution of waste pre-treatment by forced aeration. Pre-sorted MSW (MSW) was pretreated
by composting for 16 weeks in a laboratory scale using forced aeration. Oxygen
concentrations were maintained at 15-18% of oxygen in air for the first 8 weeks and 10-15
% for the later 8 weeks. The ambient temperature was kept constantly between of 20-35
QC. Representative samples of waste from the reactor were collected every fortnight
wherein analysis and full characterisation on the solid matter (C/N ratio, TS and VS, R17,
Biogas) and on the eluate (BOO, COD, TOC, TKN, Conductivity, pH, NOx and NH3)) were
conducted.
The process showed a sharp increase in temperature in the first 6 weeks, ranging from 30-
70 QC indicating a period of high biological activity, a decrease from day 30 to day 50 from
70 to 30 QC and a consistent decrease throughout the later days of the process from 35-25
QC. The sharp increase in temperature signifies a period of maximum biological activity,
where readily biodegradable material decomposes as well as some of the resistant
materials pointing out the success and efficiency of the forced aeration process. For the
first 25 days in an anaerobic environment, waste pre-treated for four weeks was the most
active, indicated by a large volume of gas produced. For the MSW pre-treated for 8, 10, 12
and 16 the volume of gas produced remained basically similar throughout the length of the
experiments. CH4 production in an anaerobic reactor shows an increasing trend for all
degrees of stabilisation up to 6 weeks, after that the gas production and quality deceases
and is comparable to the remaining degrees of treatment.
A gradual decrease in concentration of key parameters (organics) analogous to the
European limit in Europa (1998), were observed after 5 weeks pre-treatment. The study
highlighted that the highest efficiency of pre-treatment is achieved in 6 to 8 weeks and,
therefore it is not recommended to prolong the treatment any further. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5868 |
| Date | January 2007 |
| Creators | Asah, Miranda Kahndi. |
| Contributors | Trois, Cristina. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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