Process improvement of the leachate treatment plant at West New Territories (WENT) landfill


Student thesis: Doctoral Thesis

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  • Lun Cheung CHIANG


Awarding Institution
Award date15 Jul 2010


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.

    Research areas

  • Leachate, Management, China, Sanitary landfills, Hong Kong, Leaching, Purification