Key findings of full-scale tests of a sludge digestion technology
with biomass recycling

Summary

The results of laboratory studies and full-scale tests of the technology of wastewater sludge digestion with biomass recycling are presented. While conducting industrial tests of the technology with biomass recycling an increase in the disintegration of ash-free matter on average up to 56.6% (the value in the control option is 42.2%) was achieved. The disintegration of ash-free matter significantly improved the dewaterability of sludge. The average increase in biogas yield was 3%. During the experiments no negative impact of the sludge recycling technology on the operation of the digester was recorded. The obtained research results allow concluding that the introduction of sludge digestion technology with biomass recycling at the Moscow Wastewater Treatment Facilities is highly promising. Calculations showed that with the introduction of this technology a decrease in the dry matter amount at the outlet of the digesters compared with traditional technology by 9–10% can be expected. The demand for a flocculant for thickening the recycle is minimized by the improved dewaterability of sludge and, thus, the consumption of flocculant during dewatering is reduced.

Key words

anaerobic fermentation , wastewater sludges , sludge thickening , recycle , increase of ash-free matter disintegration