Biosolids Management (at 1.08.47 minute)
Biosolids are the nutrient r i c h by-product of
modern MSW treatment. Since the 1980s the
management of these has been increasingly focused
on recycling. Efforts to control the pollution at its
source have dramatically improved the quality of
wastewater coming into treatment plants and the
quality of biosolids produced by these plants has
increased.
WATER Solids handling (at 1.10.10 minute)
A) Sludge thickening B) Sludge digestion C) Sludge dewatering
A) The first step is the sludge thickening process and the process is very similar to that
happening in clarifiers. This process takes solids concentration from 0.5% to 6%. In the
gravity thickener we use gravity to settle the sludge out and make it thicker, so that it’s
easier to treat in the rest of the solids handling facilities. When pressure is released the
sludge floats to the top and we end up with 5% solids blanket at the top, which we scrape off
and send to our solids handling facilities for digestion.
B) In the digesters we heat the sludge up and the micro-organisms start to break it down
and get rid of some of the volatile compounds. In that process it also destroys some of the
pathogens. When we are finished the sludge is transformed into a useful product. But during
that process we also generate some methane. That methane produced is used to run
generators and those generators power part of the wastewater treatment plant. Waste heat
is also generated which is used to heat the digestion process, so it’s a nice circle and a whole
lot of the energy stored inside the sludge is used to make the whole process cheaper to
operate