Investigating the microwave-hydrogen peroxide treatment process for potential commercialization

Two pilot-scale, dielectric heaters, that utilize different frequencies of electromagnetic radiation (EMR), were modified to treat organic slurries with the aid of hydrogen peroxide (H₂O₂). Organic slurries investigated include: waste activated sludge (WAS), liquid dairy manure (DM), and palm oil mill effluent (POME). Treatment efficacy was evaluated in terms of changes in the substrate’s digestibility, available nutrients, and physical properties. The first heating system operated at a microwave frequency of 915MHz (MW-H₂O₂) and was modified to attain treatment temperatures above 100°C. Results showed that such high temperatures permitted the effective use of larger oxidant dosages, which was found to be beneficial for treating DM and useful for treating WAS, in select circumstances. However, the additional equipment costs and difficulties encountered in operating a pressurized high temperature dialectic heating system may prove inhibiting at larger scales. The second heating system used radiofrequency EMR at 27MHz (RF-H₂O₂) and was modified from its original batch configuration for continuous operation. The continuous RF-H₂O₂ process, the first of its kind, was demonstrated to be a viable treatment technology that achieved comparable results to the better studied MW-H₂O₂ system for DM and WAS substrates. A controlled comparison of the two dielectric heaters showed that their treatment efficacy was similar, but suggested that heating at 27MHz offers advantages with respect to its operation and the degradation of organics. The effect of higher heating rates and a 60°C treatment regime on WAS were also investigated, revealing that the treatment efficacy of the MW/RF-H₂O₂ process was suppressed in both cases, particularly in regards to the release of nutrients. Using original experimental results and information from the literature, a full-scale, RF-H₂O₂ process is presented for treating thickened WAS from one million people. The proposed system recommends three 900kW 27MHz dielectric heaters, a final treatment temperature of 95°C, a H₂O₂ dosage of 0.35%(v/v) per percent of dry solids, a heat exchanger to preheat the substrate, and an optional holding tank to enhance the release of orthophosphates.Applied Science, Faculty ofCivil Engineering, Department ofGraduat