What are the monthly operating costs of a wastewater treatment plant?

Monthly operating costs of a reed bed wastewater treatment plant are practically zero. A reed bed WWTP operates without electricity and without replenishment of bacteria, which eliminates the two largest regular expenses. The only cost is an annual service inspection for €60–€80, which translates to €5–€7 per month. For comparison, a cesspool costs €50–€100 per month for emptying, and a conventional biological WWTP costs €15–€25 for electricity and bacteria.