Sanitary Level Transducer to Measure Milk Level

Because I own a milk processing plant, the milk generated by the waste water must be timely treatment, otherwise will be fined. Therefore, I need a sanitary level sensor to measure or monitor the change of milk level, so as to inform me to change the milk can in time. Does anybody know that?
It's not clear what you mean by sanitary.

Is this a can that is floor standing normally in the same place with the lid open - if so a fixed straightfoward ultrasonic level probe would suffice.

I'm guessing this is waste milk separated from washwater collected in a canister, to be disposed of when the canister is full.