when mixing is adequate, bubbles on top are quarter (or loonie) sized or smaller, no mats or crust on surface, visible rotation of tank contents that continues for at least 5 minutes after mixers turn off.
Hydrolyzer tank, bacteria in there robust enough to handle continuous mixing, not going to over mix.
methanogens in digester can be damaged by overmixing
transfer from prep to hydrolyzer, and hydrolyzer to digester should happen immediately after mix cycle
when mixing is inadequate, and solids build up at edges of tank, transfer of heat is reduced
weekly remove 500 gallons from bottom of digester tank