Settled activated sludge is thicker than raw sludge
Nature always has the best answer. The Archaea microbes can easily handle this minor problem. The only item of concern is sludge parameters. The archaea have a ph range of 5.5 to 10.0. temp range in 34 F to 180 F they are aerobic and they can fully function when pollution is no more than 6% by volume. (mix with other sludge should eliminate this concern).