|Title:||Performance study on organic and nitrogen removal of leachate by a two-stage oxic-anoxic biological aerated filter (OABAF) system|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Sanitary landfills -- Leaching.
Refuse and refuse disposal -- Management.
|Department:||Department of Civil and Structural Engineering|
|Pages:||94,  leaves : ill. ; 30 cm.|
|Abstract:||In most countries, the most common way to dispose municipal solid wastes (MSW) is sanitary landfilling. In spite of many advantages, the generation of highly polluted liquid leachates can bring contamination of groundwater and soil contamination during landfill usage. Year by year, the risk of the cumulated landfill leachate has become a severe environmental issue. In Hong Kong, most of the leachate is come from landfill and refuse transfer stations. Activated sludge process has been introduced for leachate treatment. However, the conventional biological treatment processes is very complicated, expensive and requires various process applications due to high concentration of chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrogen, heavy metals and colour. Under the extreme high organic (BOD & COD) and nitrogen (NH4-N) strengths, leachate removal efficiencies are usually limited. So that, new technologies have been developed and tried to be financially attractive. From the previous research study with a two-stage OAB system, the organic treatment efficiency (in term of TOC) was ranged from 38.7% to 99.8%, and 31.2% to 99.5% for ammonia removal efficiency was also achieved at various operating conditions. It was found that this system can achieve a 98.4% organic removal and 79.4% ammonia reduction of simulated leachate at 5.4 g/hour organic loading, and 7 hrs hydraulic retention time (HRT). From this preliminary stage of study, it indicated the potential of the application of organic and nitrogen removal in the leachate treatment from transfer station. Therefore, a further research on the removal efficiencies of leachate under various operation conditions for oxic and anoxic treatment is necessary. In this study, a two-stage oxic-anoxic biological aerated filter (OABAF) system was proposed for the enhancement of nitrogen removal in the treatment of simulated leachate. Laboratory experiments were conducted at different hydraulic retention times (HRTs) carbon to nitrogen ratios, carbon and nitrogen concentration and the reactor effective volume. Results of the long-term operation of the OABAF system showed that, the organic treatment efficiency for TOC was ranged from 76.2% to 96.9%, and 57.7% to 93.4% for its overall NH4-N removal efficiency was also achieved at various operating conditions. It was found that when coral stone was used as filter media, this system can achieve a 97% organic removal and 94% ammonia reduction of simulated leachate at 2.4 g/hour organic loading, and 10.5 hrs hydraulic retention time (HRT) under the effective volume is 33% of the reactor volume. When significant amount of biological plastic spores were mixed with coral stone to increase the effective volume to 50% of the reactor volume, this system can achieve an 86% organic removal and 62% ammonia reduction of simulated leachate at 18 g/hour organic loading, and 10.4 hours HRT. Due to its reliability, simplicity and high cost-effectiveness, it was concluded that the two-stage OABAF system was excellent in nitrogen removal performance and can be applied to treat effectively the leachate generated from refuse transfer stations or landfills.|
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