TREATMENT OPTIONS FOR ORGANIC WASTE
Paper Presenter: Dinesh Surroop, University of Mauritius
Author: Romeela Mohee, University of Mauritius
Abstract
Solid waste is in fact material which arises from various human activities and which is
normally discarded as useless or unwanted. It consists of highly heterogeneous mass
of discarded materials from urban community as well as the more homogeneous
accumulation of agricultural and industrial wastes. In Mauritius, solid waste was
traditionally disposed of in open dumpsites. There were around nine open dumps
situated all over the island in the early 1990’s. Since the government policy in solid
waste management has been to adopt landfilling as the main treatment/disposal
option, all the dumping sites had been closed. The solid waste generated is now routed
towards the sole sanitary landfill of the island. Since there has been an increase in the
standard of living, the amount of waste generated has increased significantly. There
are around 1200 tons of solid waste generated every day from different sources. A
study was therefore conducted on the treatment options of the organic fraction of
municipal solid waste. The two biological treatment methods namely composting and
anaerobic digestion was investigated.
The organic fraction of municipal solid waste had all the necessary requirements to
undergo the composting process. A maximum temperature of 63.6oC was recorded
during the degradation process. The initial moisture content was 54.1% reduced to
38.1% at the end of the degradation process and the initial volatile solids was 91.9%
and finally reduced to 77.3%. The compost derived from the organic waste had a very
good quality. After the curing process, the compost was dark brown in colour and had
an earthy smell. It also had a pH of 7.02, a moisture content of 32.9%, a C/N ratio of
11.5 and a solvita maturity index of 6. Moreover, the compost was very rich in
nutrients like nitrate, phosphate and potassium.
The organic waste was mixed with wastewater sludge from sugar industry which was
used as inoculums for the process of anaerobic digestion. The mixture of organic
waste and sludge had a carbon to nitrogen ratio of 16, moisture content of 90% and
volatile solids of 85.9%. The mixture was degraded under mesophillic condition. The
initial chemical oxygen demand (COD) was 54265 mg/l and it reduced to 15192 mg/l
at the end of the process which represent a reduction of 72%.. The biogas produced
from the process had 60% by volume of methane. A total of 1200 cm3 of methane was
generated over a period of twenty eight days. The volume of methane produced per
unit weight of substrate was found to be 0.23 cm3/g.
It was therefore that organic fraction of municipal solid waste can undergo the process
of composting and anaerobic digestion which can be used as a treatment option.
Keywords: Municipal Solid Waste, Organic fraction, Composting, anaerobic
digestion
Corresponding authors:
Mr Dinesh Surroop,
E-mail: d.surroop@uom.ac.mu
Paper type : Oral Presentation
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