The wastewater treatment plant in Sindelfingen, near Stuttgart, treats wastewater for 250,000 residents. The process valves with their pneumatic valve actuators DLP and DRD from Festo are distributed throughout the entire plant, sometimes in locations that are not easily accessible.
There are six centrifugal pumps in the pumping cellar, each with a power consumption of 90 kw and a delivery rate of up to 500 L per sec at a delivery height of 8 to 9 meters. Before the use of pneumatic automation technology, the non-return valves had to be held open continuously via the pumps. This lowered the delivery rate by up to 10%. Now the new pneumatic automation of the existing knife gate valves has fully replaced the functionality of all non-return valves and thus increased operational reliability.
The Sindelfingen wastewater treatment plant now achieves the same pump delivery rate as before with significantly lower energy consumption, saving 89,469 kwh or €11,300 on energy costs per year. This corresponds to a total savings of 2% of the entire plant's electricity demand.
The Benefits For the Pumping Station
The pumping station is now more clearly laid out and the system requires less space. The noise level has also been reduced considerably. Because the knife gate valves close tightly, there are no more undetected leaks. When closing the knife gate valves, no water hammers occur and thus no vibrations in the pipeline that have negative effects on service life. Gas bubbles that form when the pump unit is at rest can now escape when the knife gate valve is opened. This ensures the pump units start automatically.
Pneumatic components are resistant to continuous loads and maintenance-free over their entire service life. They are very easy to install and are cheaper than comparable electrical solutions, particularly when implementing complete system solutions. Pneumatic components are also safe. Compressed air continues to be available even during a power failure. An air reservoir is always available along with a compressor for generation and preparation purposes.
With the pneumatic solutions from Festo, the plant operator has managed to significantly increase the durability, service life and energy efficiency with an amortisation period of less than a year.
The energy consumption of water treatment plants has a major impact on local authority budgets. Its share accounts for up to 20% of energy costs. According to the study "Enhanced energy efficiency in wastewater treatment plants" published by the Federal Environment Agency (UBA), German wastewater treatment plants consumed 4,400 gwh/a of electricity in 2006. Aerators, large pumping stations and stirrers as well as sludge treatment in particular require large amounts of energy. Only around one-fifth of the entire electricity consumption is covered by the wastewater treatment plants themselves through the generation of power from biogas.
Experts believe that enormous potential can be unlocked through the reduction of electricity consumption and the generation of power by the plants themselves. Process engineering optimizations such as energy-efficient design and regulation of the ventilation or the use of highly efficient pump impellers also have a positive effect on plant operation.
Pneumatic automation solutions are an economical alternative. In wastewater treatment plants, process valves are often actuated only infrequently or not at all for long periods of time. This leads to the formation of deposits and caking and thus to increased breakaway torques or forces. Pneumatic actuators can overcome this problem simply by increasing the air pressure. They cope well with loads without getting damaged and are not affected by differences in temperature, contamination and humidity. Pneumatic actuators only require electricity for regulating and generating compressed air and act directly on the shut-off valve.