A pilot study on testing of full denitrification in existing leachate treatment works of north east New Territories (NENT) landfill

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A pilot study on testing of full denitrification in existing leachate treatment works of north east New Territories (NENT) landfill

 

Author: Chan, Chung-tak Thomas
Title: A pilot study on testing of full denitrification in existing leachate treatment works of north east New Territories (NENT) landfill
Degree: M.Sc.
Year: 1999
Subject: Sanitary landfills -- China -- New Territories (Hong Kong) -- Leaching
Leachate -- China -- New Territories (Hong Kong)
Denitrification -- China -- New Territories (Hong Kong)
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Civil and Structural Engineering
Pages: xvi, 104 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1480026
URI: http://theses.lib.polyu.edu.hk/handle/200/1861
Abstract: A post-denitrification process using methanol as external carbon source was selected for the modification of the existing Leachate Treatment Works of North East New Territories (NENT) Landfill in order to denitrify the nitrified leachate for the new discharge standard of Total Nitrogen < 200 mg/L. In the mean time, another on-site denitrification pilot study was carried out in order to find out the possibility of full denitrification encouraged by high methanol dosing rate in the existing aeration lagoons. In Testing Stage I from 08/07/98 to 24/08/98, the mixed liquor from the aeration lagoon with NO3-N concentration of 3200 mg/L was used for the commissioning of the pilot plant. The raw leachate of NENT Landfill with average NH3-N concentration of 4000 mg/L and average COD concentration of 4200 mg/L was fed into the pilot plant with an average HRT of 22 days. The methanol dosing rate was increased from 2 g per liter of raw leachate to 16 g per liter. The NO3-N concentration of the pilot plant was reduced from 3000 mg/L to 1100 mg/L in the treated effluent. The possibility of full denitrification was confirmed. In Testing Stage II from 24/08/98 to 16/10/98, the raw leachate of NENT Landfill with similar quality as that in Testing Stage I was fed into the pilot plant. The average HRT was about 20 days. High methanol dosing rates as 24 g per liter of raw leachate was tested at the beginning of Testing Stage II, and then decreased gradually to 14 g per liter. The NO3-N concentration in treated effluent of the pilot plant was maintained at an average of 150 mg/L. The optimum methanol dosing rate was determined as 16 g per liter of raw leachate with average NH3-N concentration of 4000- 4500 mg/L. Comparing of the chemical consumption in this pilot study and that in the post denitrification process, the chemical cost in terms of the consumption of sodium hydroxide (50% w/w), sulphuric acid (98%) and ethanol for this pilot process was more expensive than that of the post denitrification process by about 41.5%. However, only two chemicals (methanol and sulphuric acid) were required in this pilot process instead of all three chemicals in post denitrification process. In the mean time, only slightly modification such as methanol storage and dosing system was required if this pilot process was chosen to be applied for the existing Leachate Treatment Works. So, the capital cost for the new denitrification plant could be saved.

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