Influence of Microwave Pre-Treatment on the Digestion and Higienisation of Waste Activated Sludge/Wpływ Dezintegracji Mikrofalowej Na Proces Fermentacji Oraz Higienizacji Nadmiernych Osadów Ściekowych

Abstract

Abstract:The article presents the results of determining the most appropriate conditions of microwave sludge pre-treatment (500-1200 W), prior to its anaerobic digestion in a continuous mode. The assessment of the pre-treatment conditions (microwave power, sludge temperature after pre-treatment) was based on: the release of organic (COD, protein) and inorganic (NH4 + , PO43-) substances into liquid, the quantity of methane produced, sludge higienisation and the susceptibility of the pre-treated sludge to dewatering. The power of the microwaves applied did not play significant role on the pre-treatment effectiveness. Taking into account the fact that sludge pre-treatment by microwave irradiation requires the delivery of energy, the pre-treatment by microwaves of higher power (1200 W) and resulting in sludge temperature of 70°C was recommended for further experiments. Sludge pre-treatment by means of microwave irradiation as a pre-treatment step influenced the effectiveness of the subsequent anaerobic digestion, conducted in continuous conditions, in a positive way. The largest amount of biogas was obtained for HRT in the range of 15-20 days. As compared to the sludge which did not undergo pre-treatment, daily biogas production and biogas yield increased by 18-41% and 13-35% respectively. The combination of microwave pre-treatment and mesophilic anaerobic digestion ensured the elimination of pathogens (Salmonella spp., Escherichia coli).

Disintegration of Wastewater Activated Sludge (WAS) for Improved Biogas Production

“…Another pre-treatment process that has already shown to improve the anaerobic digestion is microwave pre-treatment [146]; which is a good substitute for thermal pre-treatment, increasing the concentration of soluble proteins in solution [147] and improving biogas [148,149] production and disinfection [150]. Microwave irradiation has two main effects, thermal and non-thermal; they involve the interaction of rapidly alternating electric field with polar proteins, fats and H 2 O and the breakdown of hydrogen bonds and the consequent death of microorganisms [151].…”

Disintegration of Wastewater Activated Sludge (WAS) for Improved Biogas Production: A Mini Review

“…Another pre-treatment process that has already shown to improve anaerobic digestion is microwave pre-treatment [125]. Microwave pre-treatment is reported to be a good substitute for thermal pre-treatment, increasing the concentration of soluble proteins in solution [126] and improving biogas [127,128] production and disinfection [129].…”

Effect of low microwave temperature on the physical and chemical properties of waste activated sludge

“…The concentration of NH4-N and PO4-P increased from about 10 mg/L for raw biosludge to about 20 mg/L about 16 mg/L in the disintegrated biosludge, respectively. Bohdziewicz et al, (2011) determined also disintegrating the biosludge under the conditions of temperature at 70 °C with 900 W of MW power for 3.5 minutes of irradiation time, leads to increase in the release of both NH4-N and PO4-P. Although low amount of NH4-N and PO4-P improvement was observed in this study, about 30.00% decrease of NH4-N concentration was reported after the heat treatment at temperatures ranging from 80-120 °C for 30 min due to the formation of NH3, which was the volatile form of nitrogen.…”