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Design of Anaerobic Digestion for Solid Waste Treatment

Babaee, Azadeh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41638 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Shayegan, Jalaleddin
  7. Abstract:
  8. In this project, performance of anaerobic digestion of organic waste in liquid phase has been investigated in an experimental process. Thus, the objective of this study was to optimize the organic loading rates, temperature and mixing of anaerobic digestion to the treatment of municipal solid wastes. To achieve this, the pilot scale experiment was conducted in 70l, fully mixed reactor. The start-up process was established over a period of 2 months. Starting the digestion in two stages was done with two different feed stocks, in which the feed stock of the first stage was star and in the second stage vegetables were considered as the organic waste. Experiment was investigated in mesophilic condition with different organic loading rates in range of 0.4-2.75 (kg VS)/(m³ .d) for constant retention time of 25 days. The reactor showed stable performance with highest biogas yield (0.4m3biogas/KgVS) with VS reduction of around 88% during loading rate of 1.4 (kg VS)/(m³ .d). As the organic loading rate was increased, the COD degradation and biogas yield decreased. In the next experiment, municipal solid waste (MSW) was used as a feed stock. MSW needs more retention time than vegetables waste for complete digestion. In the next part of the investigation, digester temperatures were set between 25-34C. Digestion with temperature in these range resulted in biogas yield of 0.23-0.33 m3biogas/KgVS , with a methane content in the biogas of 52.4-62.6%. The methane content and yield decreased with reduction of digestion temperature. However this reduction was almost negligible from 34C to 30C. In the third part of the investigation, the digester was set at various mixing mode: continuous, intermittent and minimal (twice in a batch, 30 minutes each time). In comparison to intermittent mixing, continuous and minimal mixing modes reduced the biogas production by 40% and 50%, respectively. At the end of the experiment, digested material was investigated and nutrient content (C, N, P ) of digested material states that digested material is suitable in respect to current fertilizers. COD increase of sample with digested output is about 50% less than similar sample with animal fertilizer.

  9. Keywords:
  10. Biogas ; Anaerobic Digestion ; Municipal Solid Waste ; Vegetabe Waste ; Mesophilic

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