Factors affecting microwave-enhanced advanced oxidation process for sewage sludge treatment.

The microwave-enhanced advanced oxidation process (MW/H(2)O(2)-AOP) was applied to sewage sludge for nutrient solubilization and solids' disintegration. Four factors, temperature, hydrogen peroxide dosage, mixing, and solids concentration were chosen for a screening experiment, and were ranked according to their significance of influence on the process. In general, temperature and hydrogen peroxide dosage are the two significant factors affecting the process, while mixing is the least significant factor. Temperature was the most significant factor for the release of orthophosphate, and hydrogen peroxide dosage was most important in ammonia release. Solids disintegration, in terms of soluble chemical oxygen demand (SCOD), was largely dependent on temperature and hydrogen peroxide dosage. For volatile fatty acids (VFA) release, mixing was the most significant factor. At higher temperatures with mixing, more VFA was released into the headspace, resulting in less VFA retained in the solution. The best results of solids' disintegration and nutrient release were obtained at 120 degrees C, and 0.80 g H(2)O(2)/g dry sludge.

Solubilization of municipal anaerobic sludge using microwave-enhanced advanced oxidation process.

The effect of microwave enhanced advanced oxidation process on the release of nutrients and solids disintegration from municipal anaerobic sludge was investigated. Three levels of temperature (160, 120, and 80 degrees C) and two sets of pH, (7.8 and 4) were selected and tested at a microwave heating time of 5 minutes and hydrogen peroxide dosage of approximately 1 mL per 1% total solids. Total chemical oxygen demand concentrations in samples decreased after the treatments at pH 4, while they remained the same as the initial at pH 7.8. The soluble chemical oxygen demand concentrations increased in all sets, regardless of treatment conditions. There was an increase in orthophosphate concentration with an increase of temperature at pH 4, while a decrease of orthophosphate at pH 7.8 was observed. Ammonia concentration also increased with an increase of temperature at pH 4. A small amount of ammonia was converted to nitrates/nitrites in the absence of acid. Acid addition helped in the destruction of sludge solids. Low pH and high temperature gave the highest nutrient release and solids destruction.

Treating solid dairy manure using microwave-enhanced advanced oxidation process.

The microwave enhanced advanced oxidation process (MW/H(2)O(2)-AOP) was used to treat separated solid dairy manure for nutrient release and solids reduction. The MW/H(2)O(2)-AOP was conducted at a microwave temperature of 120 degrees C for 10 minutes, and at three pH conditions of 3.5, 7.3 and 12. The hydrogen peroxide dosage at approximately 2 mL per 1% TS for a 30 mL sample was used in this study, reflecting a range of 0.53-0.75 g H(2)O(2)/g dry sludge. The results indicated that substantial quantities of nutrients could be released into the solution at pH of 3.5. However, at neutral and basic conditions only volatile fatty acids and soluble chemical oxygen demand could be released. The analyses on orthophosphate, soluble chemical oxygen demands and volatile fatty acids were re-examined for dairy manure. It was found that the orthophosphate concentration for untreated samples at a higher % total solids (TS) was suppressed and lesser than actual. To overcome this difficulty, the initial orthophosphate concentration had to be measured at 0.5% TS.

Role of mixing on microwave-enhanced advanced oxidation process in treating sewage sludge.

The microwave enhanced advanced oxidation process (MW/H2O2-AOP) was used for the release of nutrients and the disintegration of suspended solids from both anaerobic sludge and aerobic sludge. The purpose of this study was to determine the effects of mixing on the performance of the process, in terms of soluble ammonia, orthophosphate and soluble chemical oxygen demands. Experiments were conducted on sludge samples with various total solids concentrations (1.1-3.7%) and hydrogen peroxide dosage (1% per 1% of total solids) at 80 degrees C of microwave temperature and five minutes of heating time. The results indicated that mixing affected solids disintegration and nutrient solubilization of sewage sludge, regardless of the sludge used, anaerobic or aerobic. However, the effects of mixing on the MW/H2O2-AOP were dependent on the total solids concentration of the sludge. A paired t-test was performed on data for aerobic sludge: at 2.9% of total solids (TS), the difference for solubilization of nutrients and solids disintegration was statistically significant at a 95% confidence level between mixing and non-mixing samples. At a lower TS of 1.7% only soluble chemical oxygen demand showed significant difference between mixing and non-mixing. The results suggest that, for sludge with higher solids content, the MW/H2O2-AOP can be more effective if a mixing device is implemented.