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AGROIWATECH Résumé de rapport

Project ID: ICA2-CT-2002-10010
Financé au titre de: FP5-INCO 2
Pays: Serbia

Improved organic matter hydrolysis by physico-chemical and biological treatment of agro-industrial sludge for reuse in agriculture

The aim of the experiments carried out on mixture of brewery wastes was to improve organic matter hydrolysis by various physico-chemical and biological treatment procedures. Starting material (defined mixture composed of 25, 3, 7 and 3 parts of spent grain, hot break and spent hops, spent secondary yeast, and spent kieselguhr, respectively) was chosen for investigation on the basis of the expected production and use part of solid wastes from breweries for animal feeding.

Experiments were carried out under laboratory conditions in order to establish conditions yielding most effective hydrolysis. In view of chemical composition of solid waste from brewery (native substrate), which is characterized by a high content of proteins cellulose, nitrogen-free extractable matter, etc. the following types of hydrolysis were performed: biological hydrolysis (yeast thermolysates, rumen) and chemical hydrolysis (NaOH, H2O2).

The possibility of hydrolyzing native mixture exists, but it is a long-lasting process (about 30 days). For enriched substrate results were obtained only for COD, but it was concluded that the problems in hydrolysis are not expected with the increase of spent grain portion. For 5% of rumen added to substrate, slight acceleration of the hydrolysis process occurred and for 20% of rumen the problem with biological contamination of samples was encountered. Inhibition by ammonia is highly possible, methane-formation process very likely to occur very quickly, and results were of a poorer quality than with 5% of rumen (high ammonia, high pH).

Regarding yeast addition, a slight acceleration of hydrolysis was observed compared to control samples. Results for 450C/60 min and 650C/45 min of yeast themolysate addition were of a comparable quality. Treatment with NaOH solution improved the hydrolysis. With H2O2 addition maximum value for COD appeared earlier than in case where only NaOH was applied but it was somewhat lower value. Results for mixtures with addition of yeast thermolysate upon hydroxide treatment were not as good as the ones obtained by using anaerobic sludge as inoculum.

On the basis of characterization of the investigated hydrolytic processes under different conditions (with and without biological and chemical pretreatment) at the beginning and at the end of the experiment it was concluded that best results were obtained in the pretreatment with NaOH solution (fastest hydrolysis and the lowest C/N ratio).


Bozo DALMACIJA, (Professor)
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