Energy-Efficient Sewer Systems
Gravity sewers should be provided where possible. Pumping requires approximately 4 Wh per m³ and m head.
Sewer flushing by means of tanker lorries requires much fuel and labour. Average annual costs are about 1 € per m sewer length, if sewers are flushed every 1 to 2 years. Over 250 million € are spent in Germany for sewer flushing every year, with limited effect.
Regular and frequent flushing reduces surface water pollution through combined sewer overflows as well as peak freights to treatment plants. Storm water storage volumes of combined sewer systems can be designed up to 50 % smaller because remobilization of deposits during storm events is greatly reduced.
Surge flushing of sewers, particularly of storage sewers is far more effective and energy-efficient to prevent or remobilize deposits. It can be effective over distances of over 1 km.
Storm screens are provided to retain solids at combined sewer overflows and reduce surface water pollution. Their power consumption is very low since they operate only periodically (See HUBER Storm Screens).
Storm tank cleaning with water surges (See HUBER Tipping Buckets) is most economical and energy efficient. The following energy consumption comparison applies for a 1,000 m³ storm tank:
- Jet nozzles: 1,000 – 10,000 kWh/a
- Agitators: 300 – 3,000 kWh/a
- Tipping buckets: 10 – 100 kWh/a