Process improvement of the leachate treatment plant at West New Territories (WENT) landfill
新界西堆填區滲濾液處理廠工藝流程改善
Student thesis: Doctoral Thesis
Author(s)
Detail(s)
Awarding Institution | |
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Award date | 15 Jul 2010 |
Link(s)
Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(ccaabc1a-9ade-4004-869d-8ab3d175b10f).html |
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Other link(s) | Links |
Abstract
Reduction on treatment efficiency has been experienced by the Leachate Treatment
Plant at West New Territories (WENT) Landfill. The leachate received is considered to
be stabile and is characterized by the presence of bio-refractory humic substances.
Humic substances are natural organic matters which can be divided into humic and
fulvic acids. Biological treatment is effective for young leachate, but it has limitations
in treating stabilised leachate. As the leachate ages, a combination of a biological
process together with other physico/chemical processes are required to provide an
effective result for the treatment of bio-refractory humic substances. In this study,
bench scale and pilot scale tests were conducted in order to obtain a full picture on the
evolution of leachate quality at the WENT Landfill, as well as to identify a suitable
process which could effectively treat the refractory organic matters in the biologically
treated leachate.
After the tests, the evolution of leachate quality was better understood. The major
source of refractory organic matters present in the biologically treated leachate was
found to be contributed by the sewage sludge received from the landfill. For the search
of a suitable process, three different methods were short-listed, namely, membrane
filtration, adsorption by activated carbon and oxidation by ozone. During the tests, all
three methods were able to remove refractory organic matters at certain degrees.
Membrane filtration by microfiltration and reverse osmosis achieved the highest
removal rate, but the low throughput rate made this method ineffective for
consideration. The next method was adsorption by granular activated carbon which
also achieved a high removal rate, but the high consumption of carbon and the technical
issues regarding the regeneration of spent carbon were major drawbacks. The last
method, oxidation by ozone, achieved a moderate removal rate, but the relatively lower
operating costs made this the most preferred option, and the one which is recommended
for full-scale implementation.
Future work is recommended to improve the findings on each of the pilot studies. For
membrane filtration, a higher operating pressure and a different type of membrane
might improve the throughput rate. Moreover, trials on the in-situ regeneration of spent
carbon should be undertaken as it might be a cost-effective solution to cut down the
consumption of carbon. For oxidation by means of ozone, further fine-tuning on the
dosage rate would lower the ozone required as well as the capital costs.
- Leachate, Management, China, Sanitary landfills, Hong Kong, Leaching, Purification