Author: Wai, Cham Man
Title: Performance study on organic and nitrogen removal of leachate by a two-stage oxic-anoxic biological aerated filter (OABAF) system with the addition of micronutrients
Degree: M.Sc.
Year: 2011
Subject: Leachate.
Sanitary landfills -- Leaching.
Refuse and refuse disposal -- Management
Sanitary microbiology.
Hong Kong Polytechnic University -- Dissertations
Department: Department of Civil and Structural Engineering
Pages: xi, 100 leaves : ill. ; 30 cm.
Language: English
Abstract: Present day waste disposal methods heavily rely on landfills and is one of the most common choices for waste disposal. Despite recent waste treatment innovations and the implementation of integrated waste management schemes in many municipalities, waste generation still increases annually. Major concerns associated with landfills is the generation of leachate, which is a toxic liquid that contains high concentrations of organic carbon, nitrogen, and traces of heavy metals. In Hong Kong, leachates originate from sanitary landfills and refuse transfer stations. Conventional treatment processes used are expensive, energy extensive, require physiochemical input, and generate biomass that requires further treatment. The two-stage OABAF can be a simple, cost-effective, and feasible alternative to treat leachate. The continual study of the two-stage OABAF system utilized actual leachate from a refuse transfer station to access the feasibility of the future application of this biological treatment method at a leachate treatment plant. An extra step to enhance the OABAF system was undertaken to explore the use of micronutrients as an additive to increase treatment efficiency. For the experimental works actual leachate was extracted from a local refuse transfer station and treated with the two-stage oxic-anoxic biological aerated filter (OABAF) system. Leachate was fed into the system while varying numerous parameters such as, the hydraulic retention time (HRT), carbon to nitrogen (C/N) ratios, and the influent organic concentration. Experimental results in the initial phase showed at HRT ranged between 8-24hrs, the OABAF system was able to achieve organic removal efficiency for COD of 71.5% to 97.2% and NHâ‚„-N removal efficiency of 29.9% to 97.08% when organic loading was 2.62 g/hr with a C/N ratio of 20:1. In the final phase, a different leachate source was tested due to stability problems found in the initial phase. Under optimum conditions of HRT 24hrs, organic loading of 7.75 g/hr, C/N ratio of 10:1, micronutrient dosage of 120 mL, the removal efficiency for organics, ammonia, and total nitrogen (TN), reached 94.98%, 80.83%, and 75.80% respectively. The addition of micronutrients enhanced the overall ammonia removal efficiency for ammonia from and TN. System treatment reached its limit in the final phase when influent leachate COD was 5000 mg/L, at which partial system failure occurred. Under limited operational capacity, the second stage of the system was found to be able to continually treat leachate samples temporarily. Given the present design criteria of the OABAF system, direct treatment of high strength leachate originating from refuse transfer stations is not feasible. With modifications to the system volume and oxygen delivery, the two-stage OABAF system with the enhancement of micronutrients can be a cost-effective and efficient treatment process utilized to remove organics and nitrogen from leachate.
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