Aeration Dark Bubbles

Too many products in solution, not enough bacterial activity. More oxigen needed and vitamins for the bacteries - milk

try fitting stirring padels to mix air into the sludge

place pipes with holes in along the bottom and pump air into the bottom of the sludge

this combined with stirring should do it

Somebody introduced some substance into the sewage system. Try and isolate the source. Check on the industrial users.

Example : the bacteria in the tank were killed because somebody poured some formalin in a manhole to get rid of bad odors.

It sounds like the presence of filamentous bacteria. This is normally caused by insufficient aeration, too high BOD loading or excessively old sludge. Try increasing aeration, reducing flow or increasing sludge wastage first.

thank u guys for all ur comments