Waste water treatment facilities do their bit to protect climate | Umweltbundesamt

The greatest consumption of power in waste water treatment is accounted for by the aeration systems in the activation basin, where biodegradation of pollutants occurs by means of supplying oxygen from the atmosphere.  This power consumption could be reduced by an average 30 percent if: firstly, cities were to use electric motors in the highest efficiency class; secondly, better control engineering were in place; and thirdly, pressure gauges and consumption monitors were installed that provide timely indication of malfunctions or system wear and tear.

There is a lot of energy lurking in the sludge itself.  Municipalities can extract biogas from it, which can then be used to generate energy in cogeneration plants.  Use of biogas is particularly efficient in larger treatment facilities serving populations of more than 10,000.  Waste water treatment facility operators are already making partial use of biogas today, but optimal operation can almost double energy yield.  Sewage sludge in smaller facilities where the generation of biogas is non-profitable can best be put to use by drying with waste heat from power plants or cement works, or with solar energy, for subsequent use as a substitute fuel.  The digested and dried sludge from larger facilities is another energy-efficient substitute fuel.

The Federal Water Act requires implementation of energy-saving technologies in waste water treatment.  There are a number of good opportunities for municipalities to meet these requirements—much to the satisfaction of both the climate and finance authorities.