Can a small town turn it sewer plant into a renewable energy source
If I understand your problem correctly, the operating budget of the wastewater treatment plant is not balanced, otherwise the costs would be compensated by all users.
In my opinion, you should not consider new fees until you have solved the budget problem.
investigate installing a bio-digester. clean biogas can be used as a trigeneration source and the end product is organic fertilizer and compost.