Sewage sludge nutrient solubilization using a single-stage microwave treatment

Abstract

The effects of an advanced oxidation process combining microwave, hydrogen peroxide and acid hydrolysis in a single stage (MW/H2O2/H+ -AOP) on the process efficiency of sewage sludge treatment and nutrient recovery were investigated. At lower temperature regimes (60-80 degrees C), the soluble phosphate was substantially higher in a two-stage process than in a single stage MW/H2O2/H+ -AOP process. However, higher soluble phosphate concentration was obtained for single-stage treatment at the higher operating temperature regimes (100-120 degrees C). With the addition of an inorganic acid, a very high yield of soluble phosphate was obtained in the solution at 120 degrees C. In tests with acid addition, soluble ammonia increased as temperature increased. For single stage MW/H2O2/H+ -AOP, maximum soluble ammonia was obtained at 120 degrees C. Significant concentrations of soluble COD were also obtained in this treatment. A threshold temperature of 80 degrees C was observed, at which all of the COD could be solubilized. However, at higher temperatures (100-120 degrees C), further oxidation processes occurred to form carbon dioxide, resulting in decreased amounts of soluble COD in the solution.

Multivariate analysis of sludge disintegration by microwave–hydrogen peroxide pretreatment process

“…Response variables of this model covered the characteristics of sludge, sludge treatment process indicators, nutrients and metals released. This unifying (AOP) model was verified by experimental data obtained from the existing literature [20,26,29,31,35,36], which was provided in Table S-1 in supplementary information. This model can be used as a tool to predict the microwave (or hybrid) treatment performance for any given values of TSS, H 2 O 2 , and pH.…”

“…Moreover, the effects of acids (e.g., HCl and H 2 SO 4 ) on sludge disintegration have been shown to enhance the release of ammonia [29]. Microwave-enhanced advanced oxidation processes have been adopted previously for the treatment of dairy manure at low pH [30]; such low-pH methods are known to offer advantages such as enhanced phosphorous release and promotion of the dewatering of sludge [31].…”

Phosphorus recovery as struvite from farm, municipal and industrial waste: Feedstock suitability, methods and pre-treatments

“…Microwave irradiation has been suggested as a pre-treatment method to release particulate P for enhanced struvite recovery (Liao et al, 2005;Pan et al, 2006;Chan et al, 2007;Qureshi et al, 2008;Lo et al, 2011) and the extent of P release depends upon the forms of P present in the source materials (Pan et al, 2006). The degree of P solubilisation depends upon microwave operating temperature and duration of heating (Liao et al, 2005) with 120 o C considered to be the optimum temperature for releasing both NH 4 + and P in sewage sludge (Chan et al, 2007).…”

Optimization and Performance of Moderate Combined Alkali and Microwave Pretreatment for Anaerobic Digestion of Waste-Activated Sludge

“…Although the combined method included the same microwave treatment, the NH 3 -N release slowed down due to NaOH addition. In this study, the NH 3 -N concentrations were all below 300 mg/L and far from causing inhibition to AD [21].…”