Poor settling in clarifier WWTP
Hydraulic overload during especially during Peak times can cause you to lose solids from clarifier to final effluent. Clarifier skimmers effluents to another tank can cause hydraulic surge. Also, not back-flushing the sludge pumps, if you are getting good settling, can cause coning. This is a weak spot in settled sludge when sludge pumps are pumping solids deep down in the sludge blanket and a weak spot is found in the sludge going to sludge pumps. When this happens you just start pumping water instead of sludge. That is why you need to backflush your pumps on a regular basis to break-up concentrated sludge settling, which can cause your sludge to bulk. So coning is when your sludge pumps intake suction finds a weak spots in the sludge and just pumps water. These are just a few of the many variables that can happen.