Questions about activated sludge

1. When sampling at our wastewater treatment plant, the anaerobic sludge and aerobic sludge obtained both appeared as a thin liquid. The former is black, while the latter is earthy brown. Should sludge be like this kind of soup? Black anaerobic sludge, or the sludge has become anaerobic ； The tan-colored one is aerobic sludge ； Mixed activated sludge appears as a slurry-like substance; the higher the sludge concentration, the thicker it becomes. 2. For the new sewage treatment plant built by our company, we need to purchase activated sludge inoculum from outside. What should the appearance of the activated sludge brought in from outside be like? Should it be a thin soup as described in point 1, or a thick paste-like consistency? The thicker the sludge, the higher its concentration; this results in lower shipping costs and less effort required for addition ； Activated sludge filter cake can also be added. 3. The vehicles that deliver the sludge to us are large tanks; why does the sample taken from it look like mung bean soup? The upper layer is water, and the lower layer consists of spherical particles. How is the sludge moisture content measured? Should the water layer be filtered out? How to ensure sampling representativeness (sampling from the top of the tank tends to yield more liquid, while sampling from the bottom discharge valve tends to yield more sediment)? Samples can be taken from both the top and bottom and then mixed in equal amounts. 4. When measuring the MLVSS and MLSS of purchased sludge, how should 25 mL be measured? Those spherical clumps of mud always stick to the walls of the measuring cylinder. 100 ML can be taken, filtered through quantitative filter paper, dried, and then weighed for calculation.

It would be more intuitive to upload some pictures, although I don’t really understand it that well either