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.

Nutrient release from fish silage using microwave-enhanced advanced oxidation process.

The microwave-enhanced advanced oxidation process was used to treat fish silage for nutrient release and solids reduction prior to its use as a fertilizer for greenhouse operations. Fifteen sets of experiments with varying hydrogen peroxide dosages and treatment temperatures were conducted to evaluate the effectiveness of the process on the solubilization of fertilizer constituents. It was found that up to 26% of total Kjeldahl nitrogen could be released as ammonia with 6% hydrogen peroxide dosage at 170 degrees C. An increase of nitrate/nitrite concentration was observed with higher hydrogen peroxide dosage and higher microwave temperature; the highest concentration of 10.2 mg L(- 1) nitrates/nitrites was achieved at at 170 degrees C and 6% H(2)O(2) dosage. Up to 20 +/- 9.5% of total chemical oxygen demand was reduced at temperatures between 120 and 170 degrees C. Large quantities of volatile fatty acids were generated at lower temperatures, corresponding to an increase in soluble chemical oxygen demand, but not at higher temperatures. The treatment of fish silage using the microwave-enhanced advanced oxidation process appears to be promising.

Real-time treatment of dairy manure: implications of oxidation reduction potential regimes to nutrient management strategies.

A pilot-scale sequencing batch reactor (SBR) was operated at a dairy farm to test real-time based control in winter operation conditions. A combination of high loading and low oxidation reduction potential (ORP) conditions in the aerobic stage of SBR treatment (an end value of -50 to -150 mV) inhibited nitrification while maintaining carbon removal. After a period of over-aeration over several cycles, the ORP at the end of the aerobic stage increased to values of 50-75 mV. Subsequently, nitrification was observed, accompanied by higher total cycle times. Significant increase in removal efficiencies of ammonical nitrogen (alpha<0.0001) and chemical oxygen demand (alpha<0.001) were observed for the high ORP phase. It is postulated that higher ORP regimes are needed for nitrification. In low ORP regimes, nitrification is absent or occurs at an extremely low rate. It is also noted that nitrifying systems treating high strength animal manure can possibly lead to unacceptably high levels of effluent nitrate+nitrite nitrogen (NO(x)-N). Two manure management schemes are proposed that give the farmer an option to either retain the nutrients, or remove them from the wastewater. Some advantages and disadvantages of the schemes are also discussed.

Factors affecting nutrient solubilization from sewage sludge using microwave-enhanced advanced oxidation process.

A microwave-enhanced advanced oxidation process using hydrogen peroxide (MW-H2O2-AOP) was used for the solubilization of phosphate and ammonia from secondary municipal sludge. Two sets of experiments were performed to determine the factors affecting nutrient solubilization from sewage sludge. Four factors--microwave heating temperature, heating time, hydrogen peroxide treatment, and sulphuric acid treatment--were incorporated into a screening design to determine which factors were significant for maximizing nutrient solubilization. For phosphorus, the three most significant factors, following the order of significance, were (i) microwave heating temperature, (ii) the combined effect of microwave heating temperature and hydrogen peroxide hydrogen peroxide addition, (iii) microwave heating temperature, and (iv) sulphuric acid addition.

Sludge reduction and volatile fatty acid recovery using microwave advanced oxidation process.

Sewage sludge was subjected to the combined microwave-hydrogen peroxide-sulfuric acid enhanced advanced oxidation process (MW-H(2)O(2)-H(+)-AOP) to evaluate the potential of reducing suspended solids in sludge. The soluble chemical oxygen demand (SCOD) and acetic acid produced were dependent on the amounts of H(2)O(2) and acid used in the process. For sewage sludge, a higher volume of H(2)O(2) addition not only favored the destruction of sludge solids, but also conserved the carbon content in the medium. Volatile fatty acid (VFA) concentrations also increased with the amount of inorganic acid in the solution. For the soluble fraction of solutions derived from microwave-treated sludge, over 96% of the total COD was in the soluble form, and up to 25% of this soluble COD was acetic acid. The presence of an inorganic acid was a stability factor in retaining the SCOD in solution, instead of the formation of carbon dioxide, resulting in reduced total COD in the solutions. By controlling the amounts of H(2)O(2) and acid addition, the MW-H(2)O(2)-H(+)-AOP could solubilize and/or reduce the sludge mass.