RESEARCH, MODELING AND OPTIMIZATION OF THE ANAEROBIC DIGESTION OF ORGANIC WASTE

© I.Simeonov, D.Galabova, E.Chorukova, B.Kalchev, S.Mihajlova, A.Mirkov, I.Petkov
© Государственный музей истории космонавтики им. К.Э. Циолковского, г. Калуга
Секция "К.Э. Циолковский и проблемы космической медицины и биологии"
2008 г.

Abstract. Anaerobic digestion (AD) is a biotechnological process for treatment of highly concentrated wastes from animal farms, agro industries, food industries and municipal treatment plant sludge, resulting in the production of biogas (a fuel of high energy and economic value) and in decreasing or removing of the polluting effect. The AD is a very complicated process which involves hundreds of possible intermediate compounds and reactions, each of which is catalyzed by specific enzymes. Many of the transformations can be accomplished by one of several alternative metabolic pathways; the different populations in the microorganism’s community are involved in delicate (sometimes unstable) equilibrium.

The paper represents the long-year work of a multidisciplinary team of The Institute of Microbiology of The Bulgarian Academy of Sciences in the field of mesophillic AD of different organic wastes (single and in mixtures) in laboratory conditions.

The treated organic waste in laboratory anaerobic continuously stirred tank bioreactors (single and in a cascade) are as follows: cattle manure; chicken litter; activated sludge from a municipal wastewater treatment station; milk whey; waste from alcohol production; waste from bio-diesel production; slaughter-house blood.

The influence of some appropriate stimulating substances (glucose and acetate) and surface active compounds (surfactants) at different stages of the process of AD has been studied. New models (deterministic and neural) have been developed in order to optimize and control it.

The main conclusions from this studies may be presented as follows: the AD of cattle dung is the most stable process in a large range of the influent organics concentration; in the case of AD of chicken litter with 7 % dry weight a height level of VFA with process inhibition occurs; AD of mixtures of cattle dung cattle dung and chicken litter (with different ratio) is more stable than AD of chicken litter; in the case of AD of mixture of aсivated sludge (70 %) and milk whey (30 %) height level of biogas production is assured, however it is possible to have failures of the process due to erroneous ratio C:N; AD of mixture of aсivated sludge and slaughter-house blood assures height level of biogas production; in the case of AD of mixtures containing waste from alcohol production failures of the process occur.