Don't forget, the heat is also keeping the pipes unclogged. If you remove the heat a lot of the fats turn into hard mass that is extremely difficult to get rid of.
Reminds me of the story of what happened when traffic lights got "upgraded" to LED to save on energy. First winter all traffic lights got completely covered in snow and traffic ground to a halt. The "waste" heat as was not such a complete waste after all, it was continuously melting snow off the lights.
This is what happens when sewage is given time to cool: https://www.youtube.com/watch?v=3i_axpk0a7Q
Reminds me of the story of what happened when traffic lights got "upgraded" to LED to save on energy. First winter all traffic lights got completely covered in snow and traffic ground to a halt. The "waste" heat as was not such a complete waste after all, it was continuously melting snow off the lights.