Anaerobic digestion of sewage sludge with grease trap sludge and municipal solid waste as co-substrates.

The feasibility of simultaneous treatment of multiple wastes via co-digestion was studied in semi-continuous mode at mesophilic conditions. The obtained results indicated that sewage sludge, organic fraction of municipal waste (OFMSW) and grease trap sludge (GTS) possess complementary properties that can be combined for successful anaerobic digestion. During the co-digestion period, methane yield and VS removal were significantly higher in comparison to digestion of sewage sludge alone. Addition of GTS to digesters treating sewage sludge resulted in increased VS removal and methane yield up to 13% (from 50 to 56.4) and 52% (from 300 to 456,547m3/Mg VSadd), respectively. While the use of OFMSW as the next co-substrate in the feedstock, can boost methane yield and VS removal up to 82% (300-547m3/Mg VSadd) and approximately 29% (from 50% to 64.7%), respectively. Moreover, the results of the present laboratory study revealed that the addition of co-substrates to the feedstock had a significant influence on biogas composition. During the experiment methane content in biogas ranged from 67% to 69%. While, the concentration of LCFAs was increasing with the gradual increase in the share of co-substrates in the mixtures, wherein only the oleic acid was higher than some inhibition concentrations which have been reported in the literature. However, it did not significantly affect the efficiency of the co-digestion process.

Co-composting as an oxygen stabilization of an organic fraction of municipal solid waste and industrial sewage sludge.

The purpose of this work is to study the characteristics of the co-composting of municipal solid waste (MSW), sewage sludge, grass and sawdust. Differing proportions of biodegradable waste were investigated through changes of temperature, oxygen consumption, organic matters, moisture content, carbon, nitrogen, C/N ratio as well as heavy metals and pathogen microorganisms content. The present study has shown that addition of MSW above 10% had a negative impact on the composting process. The initial C/N of the mixtures with a higher MSW content was below 18. Lower losses of organic matter occurred during composting for the mixture with the highest addition of MSW. Although studies have shown that composting is a good method for the disposal of organic waste additional research is required in order to optimize the organic and nitrogen compounds degradation during the co-composting process. In conclusion, a 1:4:4:1 mixture of MSW:sewage sludge:grass:sawdust is recommended because it can achieve high temperature as well as the highest organic matter degradation and highest N content in the final composting product. The concentration of heavy and light metals in all composts was within the limits of regulation of the Polish Minister of Agriculture and Rural Development.

Ultrasound as a pre-oxidation for biological landfill leachate treatment.

In this study, the effects of low energy ultrasound irradiation on landfill leachate treatment by means of sequencing bath reactor were investigated. The aim of this work was to estimate the influence of leachate irradiation time on aerobic treatment efficiency. The sonification of the leachate was carried out in static conditions using the disintegrator UD-20. The field frequency of 22 kHz (the power output equals to 180 W) and amplitude of 12 microm was applied. The sonification time was changed in the range of 30-140 s. It was found that ultrasonic pretreatment enhances the subsequent aerobic digestion resulting in a better degradation of landfill leachate. The sonification of raw leachate leads to enhancement of COD and ammonia removal as compare to experiment without ultrasound.