The influence of ultrasonic disintegration aided with chemicals on the efficiency of sewage sludge centrifugation

The dewatering efficiency of sewage sludge during its centrifugation was assessed using two methods: sludge was either conditioned by chemicals (cement, ash, gypsum) or exposed to the ultrasonic field and conditioned by these chemicals. The overall goal of this research was to prove that the ultrasonic field energy and the chemical substances can change the structure of sewage sludge by increasing the size and the packing ability of particles, and at the same time the quantity of gravitational water present in sewage sludge. This improves the efficiency of sewage sludge dewatering. The efficiency of mechanical dewatering can be increased by combining the method of initial sonication with adding chemicals during sewage sludge conditioning. We observed an increase in the velocity of flocculation which was related to the dispersing effect of ultrasounds. The addition of chemically neutral substances led to more efficient thickening of sewage sludge conglomerates. During mechanical dewatering these conglomerates maintained more rigid structure with reduced compressibility which resulted in their elevated porosity at high pressures and improved the dewatering ability of sludge. This decreased final hydration and changed the distribution coefficient in reference to the parameters of unconditioned sewage sludge during dewatering.