Theoretical and experimental aspects of dewatering effects on wastewater sludge induced by high-energy electrons and gamma radiation

$\sp{60}$Co $\gamma$-source and electron beam radiation were investigated as alternative methods for sludge conditioning. Since the efficiency of sludge disinfection, and toxic organic chemical destruction with irradiation is well documented, this study concentrated on theoretical and experimental aspects of sludge dewatering enhancement due to irradiation. The primary parameters used for evaluation of dewatering were: specific resistance of filtration (SRF), bound water content, and zeta potential of sludge.A model was developed to predict how sludge particles compete for radiation induced radicals, e.g. OH$\cdot.$ Experimental results showed that the scavenging power of sludge systems were higher at large absorbed irradiation doses. When the scavenging power exceeded 10$\sp9$ (sec$\sp{-1}),$ the scavenger (KCNS), could completely eliminate the effect of conditioning of liquid sludge by radiation absorbed doses up to 2000 krads. It was observed that bound water content was reduced by irradiation processes, and sludge zeta potential became more positive toward zero. The experimental results also showed that larger absorbed irradiation dose yielded better treatment results, but generally lower efficiency within tested doses of 2000 krads. These findings confirm that irradiation can reduce sludge bound water content and enhance agglomeration by altering sludge particle surface charge. It was also found that higher irradiation dose rate yielded lower dewatering improvement efficiency because of radical recombination. Results of this study will allow for the optimization of radiation treatment, when applied to sludge conditioning