Piggery slurry - Aerobic treatment with heat recovery

Svoboda, Ivo F (1993) Piggery slurry - Aerobic treatment with heat recovery. PhD thesis, University of Glasgow.

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Abstract

The objectives of the study were to evaluate a mathematical model, derived from empirical data obtained from laboratory experiments, for the prediction of the characteristics of aerobically-treated piggery slurry in a large-scale reactor operating under practical conditions. This model was extrapolated for use in the prediction of extractable heat and heat losses from the process and written as a computer program "Farm Waste Management". Predicted heat values from this program were then compared with observed experimental data. The 23m3 reactor, insulated for heat conservation, was built together with a commercial piggery for fattening and weaning pigs. The reactor was fitted with an aerator and a water to water heat exchanger. Energy recovered from the reactor was measured and used in the weaner house. The slurry collected from the piggery varied in composition and the total solids concentration ranged from 25.2g/l to 101.8g/l. Several of the major analytical values were correlated to enable, in the future, the calculation of a whole complex of analyses from the results of a few relatively simple analyses within the range of total solids experienced. Aeration of slurry and operation of the treatment plant met with some technical difficulties in the early stages, but after four months the plant was commissioned and an experimental program initiated. The effects of treatment time, temperature and dissolved oxygen concentration on the quality of the treated slurry were determined and the characteristics of the treated slurries were compared with the predicted values from the model and computer program. Differences between the observed experimental results and the predicted values are discussed and possible explanations offered. Some changes in the model would improve the accuracy of the predictions although variations in some of the experimental data may be due to the inability to control operating conditions in the large scale reactor. Incomplete mixing in particular caused sedimentation, with resultant anoxic or anaerobic zones. The highest quality effluent slurry in terms of pollution potential was produced by treatment at mesophilic temperatures during which nitrification occurred. In general, the performance equalled or exceeded that predicted by the model except for the BOD5 of the supernatant effluent. Shorter treatment times and low dissolved oxygen concentrations prevented nitrification and the results of treatment were similar to those predicted except again for the BOD5 of the supernatant. Thermophilic treatments at 50

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: S Baines
Keywords: Chemical engineering, Agricultural engineering, Environmental engineering
Date of Award: 1993
Depositing User: Enlighten Team
Unique ID: glathesis:1993-72641
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72641

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