Investigations showing the possibility of BTX biodegradation present in the water environment under anoxic conditions have been presented. The effects of transformation of benzene, toluene, o-xylene and p-xylene by indigenous to sewage microorganisms as well as by isolated species of bacteria like Aeromonas sobria, Enterobacter sakazaki, Pseudomonas aeruqinosa, Staphylococcus lentus and the mixture of these species varied distinctively. The results and calculated degradation rates have been compared to some results given by other authors. In anoxic conditions all investigated aromates have shown to be biodegradable. The highest rate of degradation was found for isolated species of bacteria from municipal sewage.

Investigations showing the possibility of BTX biodegradation present in the water environment under aerobic conditions have been presented. The effects of transformation of benzene, toluene, o-xylene and p-xylene by indigenous to sewage microorganisms as well as by isolated species of bacteria like Aeronwnas sobria, Bacillus steareothermophilus, Enterobacter sakazaki, Pseudomonas aeruginosa. Staphylococcus lentus and the mixture of these species varied distinctively. The results and calculated degradation rates have been compared to some results given by other authors. In aerobic conditions all investigated aromates have shown to be biodegradable. The highest rate of degradation was found for indigenous to municipal sewage microorganisms.

Hydrodynamic disintegration of the activated sludge and foam results in organic matter transfer from the solid phase to the liquid phase. Hydrodynamic disintegration caused an increase of COD value in activated sludge and foam of 220 mgdm3 and 609 mgdm3 - respectively, besides the degree of disintegration increases to 38% and 47%- respectively- alter 30 minutes of disintegration. Hydrodynamic cavitation affects positively the degree of disintegration and rate of biogas production. Also addition of a part of digested sludge containing adapted microorganisms resulted in acceleration of the anaerobic process. Addition of disintegrated foam (20% and 40% of volume) to the fermentation processes resulted in an improvement in biogas production by about 173% and 195% respectively - in comparison to activated sludge without disintegration (raw sludge) and 142% and 161 % respectively - in comparison to activated sludge with a part of digested sludge (80% raw sludge + 20% digested sludge).

Activated sludge systems designed for enhanced nutrients removal are based on the principle of altering anaerobic and aerobic conditions for growth ofmicroorganisms with a high capacity of phosphorous accumulation. To avoid return of large parts of accumulated phosphorous in the processes of sludge conditioning chemical precipitation is often applied. This can be not be the case, at least for a part, if prior to other processes of sludge handling, the sludge will be disintegrated. It was demonstrated that disintegration of surplus activated sludge permits removal of a substantial part of nutrients in the form of struvite. The effects of sludge disintegration on metals ions release and poly-P destruction were elucidated. Appropriated handling of disintegrated sludge allows for removal of at least 25% of the inflowing phosphorous load without addition of chemicals.