Investigation on Characteristics of Microwave Treatment of Organic Matter in Municipal Dewatered Sludge

Abstract

This study aimed to utilize a microwave technology to degrade active organic matters of the municipal dewatered sludge in a high-temperature environment. The effects of extraction agent, nanomaterial assistants, and microwave-absorbing agents and activating agents on the degradation efficiency were investigated. Dimethyl carbonate was used as the extraction agent. Nanostructured titanium oxide (TiO2) and zinc oxide (ZnO) exhibited effective assistance in the process of microwave treatment. We also developed a kind of microwave-absorbing agent, which was the sludge-based biological carbon. The sodium sulfate (Na2SO4), calcium hydroxide (Ca(OH)2), and magnesium chloride (MgCl2) were selected as activating agents to facilitate the organic matter discharging from the sludge. Through optimizing the experimental factors, it was confirmed that 0.1 wt% TiO2, 0.1 wt% ZnO, 2 wt% dimethyl carbonate, 10 wt% sludge-based biological carbon, 7.5 wt% Ca(OH)2, 0.5 wt% MgCl2, and 6 wt% Na2SO4 were the most appropriate addition amounts in the municipal dewatered sludge to make the organic matter decrease from 42.17% to 22.45%, and the moisture content reduce from 82.98% to 0.48% after the microwave treatment. By comparison, the organic matter degradation is almost zero, and the moisture content decreases to 8.69% without any additives. Moreover, the residual inert organic matter and sludge can be further solidified to lightweight construction materials by using liquid sodium silicate as the curing agent. The research provides a significant reference for the effective, fast, and low-cost treatment of the organic matter in the municipal sludge.

Detection of efficiency of microwave-enhanced sludge treatments by dielectric measurements

“…Alkaline dosage is a suitable chemical treatment method the increase disintegration of bacterial cell wall however, many studies pointed out that in combination with physical pre-treatments, the efficiency could be enhanced [7,8]. The characteristics of microwave treatment of municipal sludge is vigorously investigated [5,6,9], but there is few studies available related to wastewater and sludge originated from the food industry. Dielectric materials, like wastewater and sludge can absorb the microwave interval of the electromagnetic spectrum, and its extent depends on the material properties, structure, temperature and frequency.…”