Treatment of municipal sewage sludge by electron beam irradiation

Irradiation treatment of sewage sludge was carried out using an electron beam accelerator. The effects of irradiation dose, sludge water content and sludge thickness on the breakdown of sludge flocs, thus the formulation of soluble chemical oxygen demand (SCOD) and soluble total nitrogen (STN), and the reduction of MLSS and endogenous OUR, and so on, were investigated. It was observed that, with increased doses, the SCOD, STN and UV absorption intensity of the sludge supernatant increased rapidly with similar trends, and MLSS considerably decreased, all indicating that a large amount of the cell contents of sewage sludge were released by electron beam irradiation. The results of endogenous OUR also showed that a large number of microorganisms in sewage sludge were killed or deactivated. Zeta potential sludge became more positive with increased doses, implying that the dewatering performance of sewage sludge was not adversely affected. It was also found that the thickness of sludge was an operation parameter of great importance in the electron beam treatment of sewage sludge due to the relatively short penetration depth in water/sludge of the high-energy electrons.