Preparation and Properties of Sewage Sludge Ceramic Pellets

The object of this study is to investigate the sintering processes of sewage sludge ceramic pellets (SSCP) as filter media. The effects of adding coal fly ash and farmland clay were tested, and the feasibility of using SSCPs in a biological aerated filter (BAF) was determined by comparing their performance with that of commercial ceramic pellets (CCP). Unlike the procedure to make lightweight sewage sludge aggregates as construction material, the sintering techniques for formation of the SSCP filter material were as follows: a maximum mass ratio of 35% dried sewage sludge mixed with clay and fly ash was preheated at 400°C for 20 min, then sintered at 1000°C to 1050°C for 5-10 min. The main chemical composition of SSCP and CCP was similar, and the environmental suitability of SSCP is satisfactory. Scanning electron microscopy images showed that the dimensions of the pores on the surface and interior of SSCP were much larger than those of CCP. Removal of NH₃-N in BAFs filled with SSCP as carrier was higher about 10% than with CCP, which indicated that SSCP supplied a much better environment for the nitrifying and denitrifying bacteria.