INVESTIGATION OF THE POSSIBILITY OF RECYCLING EXCESS ACTIVATED SLUDGE TO PRODUCE SORPTION MATERIAL

The paper presents research on the possibility of obtaining sorbent from excess activated sludge from biological wastewater treatment facilities by thermal decomposition in the absence of oxygen (pyrolysis). Parameters for the pyrolysis of excess activated sludge to produce charcoal were selected. The following experimental data were accepted as constant: moisture content of excess activated sludge not exceeding 5%, particle size of sludge not exceeding 0.5-1 mm; heating rate in the furnace to the specified temperatures of 5 °C/min. The effect of pyrolysis at temperatures of 550-650 °C and a holding time in the furnace of 0.5-1 hour on the characteristics of the obtained coals was evaluated. The parameters were selected based on the properties of excess activated sludge and its similarity to plant biomass in terms of carbon content in dry weight. The completeness of the formation of the porous structure of the carbonized material was evaluated depending on various pyrolysis parameters. The evaluation was carried out by determining the sorption efficiency using methylene orange. It was established that excess activated sludge can be used to obtain sorption materials. The best sorption efficiency indicators are achieved at a waste heating rate in the furnace of 5 °C/min, a pyrolysis temperature of 600-650 °C, and a holding time of 1 hour. This also means more complete development of the porous structure of the sorption material. It has also been shown that further increasing the pyrolysis temperature does not significantly affect the sorption capacity and, on the contrary, can lead to a deterioration in the quality of the coals. It has been found that coal obtained by pyrolysis of excess activated sludge has a sorption efficiency for methylene orange close to that required for clarifying activated coals of grades OU-A and OU-B and sufficient for coals of grades OU-V and OU-G.