I'm interested to know whether you have solved the problem of your sewage treatment plant humming. We have just had a Tricel plant for 12 people installed at the bottom of the garden which is 50m from the house and the humming is very noticeable and annoying. The guy who installed it has simply said this is normal as it has electrical moving parts, but we were not expecting this level of noise and would not have agree to the system had we known. Is Tricel a bad make for noise? Friends nearby have a Klargester which you can only hear if you stand right next to it and even then it's almost inaudible. I can see from google research that there are non-electric silent makes such as Biorock and Clearwater,we are thinking of getting ours changed for one of these. The Tricel seems a waste of money!