Effects of ionizing radiation in wastewater treatment and residuals processing

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Civil and Architectural Engineering

First Committee Member

Thomas D. Waite, Committee Chair


Laboratory and pilot scale tests were conducted to evaluate the feasibility of applying ionizing radiation technology as a means to enhance overall operation at an activated sludge wastewater treatment facility with residuals processing. Effects of ionizing radiation were investigated with respect to applications of bulking control, thickening enhancement, and anaerobic stabilization. Irradiation induced permanent effects in several sludge parameters including solids content, COD, ammonia-nitrogen, zeta potential, specific surface area, resistance to filtration, bound water, sludge volume index, microbial inactivation, pH, organic acid production, and digester gas evolution. After compiling the beneficial effects from preliminary studies and pilot tests, it was determined that at a dose of 2--3 kGy, radiation technology would be potentially successful for bulking control and to a lesser degree, enhanced thickening and radiation-assisted anaerobic digestion. For this total absorbed dose range, experimental results showed that thickening rates, sludge conditioning, and dewaterability characteristics could be enhanced, although many parameters showed properties of a competing mechanism, in which larger doses induced undesirable effects. Differences were also noted between gamma irradiation and electron beam irradiation, indicating the possibility of a dose rate effect. A cost analysis based on preliminary tests determined that a centralized electron beam irradiator might be applied economically in an integrated, multi-application approach at an estimated annual savings of $0.2--2.8 million. Considering that the annual cost of operating an accelerator unit was estimated at $2.4 million ($2.16/m 3), this might translate into an important savings for a large-scale wastewater treatment facility. Results of this study will allow for the optimization of radiation-assisted processes at full scale, when applied to activated sludge bulking control, enhanced thickening, and anaerobic digestion.


Engineering, Environmental

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