Microwave oxidation treatment of sewage sludge

Abstract

Microwave-oxidation treatment of sewage sludge using various oxidants was studied. Two treatment schemes with a combination of hydrogen peroxide and ozone were examined: hydrogen peroxide and ozone were introduced into the sludge simultaneously, followed by microwave heating. The other involved the ozonation first, and then the resulting solution was subjected to microwave and hydrogen peroxide treatment. The set with ozonation followed by hydrogen peroxide plus microwave heating yielded higher soluble materials than those of the set with hydrogen peroxide plus ozone first and then microwave treatment. No settling was observed for all treatments in the batch operation, except ozone/microwave plus hydrogen peroxide set at 120°C. The pilot-scale continuous-flow 915 MHz microwave study has demonstrated that microwave-oxidation process is feasible for real-time industrial application. It would help in providing key data for the design of a full-scale system for treating sewage sludge and the formulation of operational protocols.

Continuous‐flow microwave enhanced oxidation process for treating sewage sludge

“…More studies on the effect of temperature on phosphorus release are currently ongoing. Overall, the results from this and our earlier microwave studies re‐affirm that the process effectively disintegrated the solids, released nutrients and metals, and improved dewaterability and settling of the sludge. The resulting solution would be ideal for struvite crystallization and anaerobic digestion for methane production.…”

“…In our earlier studies, the maximum phosphorus release occurred at 60 °C and orthophosphate was a major product . The MW/H 2 O 2 ‐AOP treatment of the sludge taken from the same MEBPR treatment system earlier (2 years ago) resulted in almost all of the soluble phosphorus being in the form of orthophosphate, and only a small fraction of polyphosphates being present in the microwave‐treated solutions . Based on our studies and others, it can be concluded that the release of phosphorus was dependent on its existent phosphorus forms in the sludge and EPS.…”

Radiofrequency-oxidation treatment of sewage sludge

“…Both RF-oxidation and MW/H 2 O 2 -AOP were very effective for cell disintegration and nutrient release from sewage sludge, as well as improving settleability, and reducing particle sizes. The treatment efficiency of RF-oxidation was comparable to MW/H 2 O 2 -AOP (Yin et al, 2007;Lo et al, 2015). RF-oxidation resulted in excellent settling compared to MW/H 2 O 2 -AOP.…”

“…Utilizing the unique features of dielectric heating, a thermalchemical treatment using a combination of microwave irradiation (MW) with hydrogen peroxide, namely, the microwave-enhanced advanced oxidation process (MW/H 2 O 2 -AOP) has been successful in destroying microbial cells and releasing nutrients from sewage sludge. It was used as a pretreatment process to produce a solution suitable for the subsequent struvite crystallization (magnesium ammonium phosphate) process for phosphorus recovery and/or anaerobic digestion to produce methane, as well as a carbon source for biological phosphorus removal process in an activated sludge system Yin et al, 2007;Chan et al, 2010;Lo et al, 2015). Unlike conventional heating methods, dielectric heat is generated via interaction of dielectric materials with electromagnetic radiation; either microwave spectrum or radiofrequency spectrum is used.…”

Cocoa pod husks as potential sources of renewable high-value-added products: A review of current valorizations and future prospects

“…It is an energy efficient technology that is applicable in chemical reactions (Chen et al 2017). Several studies have focused on microwave pretreatment of fibrous raw materials (Manzoor et al 2013;Lo et al 2015). Microwave pretreatment allows a subsequent increase in enzyme activity (Chen et al 2017), but it requires a high investment.…”