Summary
The volume of sewage sludge generated by municipal sewage treatment plants is constantly on the increase. This growth stems from the rising number of households connected to the sewage system and the increasingly stringent requirements for water quality, thereby necessitating a more thorough decontamination process.
A substantial proportion of sewage sludge is spread on agricultural land. An argument against this practice, however, stems from the high concentrations of organic and inorganic pollutants which are frequently found in sewage sludges. These pollutants, which include heavy metals, dioxins, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), represent a threat to plants, animals and humans.
The object of this research project was the development of a process for the reduction of organic pollutants in sewage sludge. Using aerobic-thermophilic sludge treatment, it was intended to verify the reduction of pollutants such as 4-nonylphenol, PAHs and the phthalate material group by the performance of semi-industrial and laboratory tests.
Results:
Tests have shown that the aerobic-thermophilic sludge treatment process is capable of decontaminating both municipal and, to a limited extent, industrial sludges to a degree where they will be suitable for agricultural use.
A combination of this process with an abbreviated upstream digestion stage has also proved to be highly promising.
