The aim of this paper is to show the basic principles of the anaerobic digestion process. All the stages of degradation, such as hydrolysis, acidogenesis, acetogenesis and methanogenesis are characterized. Biodegradable organic matter consists of three main types of substances: carbohydrates, proteins and lipids; the metabolic pathways of their decomposition are described. The last part of the paper presents the co-digestion process, its benefits and technological parameters required to make that process attractive from an economical and environmental point of view.

Biomethanization of mixed organic substances is the effect of coexistence of numerous groups of microorganisms. Methanogenic degradation of such substances involves at least three different trophic groups of anaerobes, namely fermentative heterotrophs, proton-reducing syntrophs and methanogenic archaea. The development of molecular techniques allowed to detect some new groups of bacteria and archea, which often stay unculturable. The cultivation of uncultured organisms is of great significance in recognizing the function of these organisms. In the past few years, newly discovered microorganisms have been successfully isolated from anaerobic sludges, and the information regarding their physiology in connection with phylogeny is updated regularly.

Landfilling is the main method of waste disposal in Poland as well as in most countries all over the world. Leachate originating during waste deposition may be a source of ground water pollution. The aim of the paper was to characterize and compare the composition of leachate originating from three landfills in Lublin Province (Poland) and differing in their methods of waste pre-treatment. Ozonation was used in the initial trials to treat landfill leachate. Experiments were carried out to determine whether ozonation using a single dose of 1.8 gO,lm3 has the same effect on the efficiency of organic removal from leachates characterized by different ages and degrees of solid waste pretreatment. From analyses (BOD5, COD, N-NH,, heavy metals) it was concluded, that excluding some fractions (glass, paper, plastics, aluminum, fine organic fraction) from the waste mass affects the leachate quality. The studied oxidizing method was found to influence the BOD5 and COD levels