Level detection for brewery wastewater applications can be a lot of things. It can be as simple as a sight glass. It can also involve lasers, radar, and ultrasonic waves.
Your tank can be underground or above. For the most part level detection technologies are the same.
With an underground tank, regular old floats tend to be the most popular. The advantage of floats is they’re cheap- and that’s the only one. I usually recommend 1 float to turn the pump on and another to turn it off. Add a 3rd float for high level and a 4th for high high level. The drawback of floats is they tangle and they fail one by one. I recommend replacing them yearly as a preventive maintenance measure- compared to waiting for one to fail and dealing with a wastewater emergency. Never fun.
My favorite way to do an above ground tank and a pressure transducer mounted through the wall of the tank. Everything is outside the tank making things easily repairable and out of the corrosive environment. If you have an underground tank you could use a submersible pressure transducer, but I don’t like expensive electronics in a wastewater tank- it will probably fail in less than 2 yrs.
Another technology is metritape, and Aquatape is great product ideally suited for brewery wastewater. These drop in through the top of the tank. All sensitive electronics are outside the tank, a metal lined rubber tube drops in to the tank. Below the water level the tube is compressed creating conductivity. Above the water level the tube is expanded with no conductivity. Simple and effective.
Radar wire is also great. These should be used more often in breweries. They could be used in malt silos, spent grain silos, spent yeast tanks, and of course wastewater tanks. Of course, these are probably the most expensive option. Rosemount makes them.
I have found ultrasonic level detection to be problematic. Foam and steam cause problems with this technology.