Shut-off valves in sewage treatment plants

GEFA knife gate valves from the AT100 and AT200 series are the ideal choice for applications in sewage treatment plants. Their robust design with metal guides on the gate ensures reliable shut-off even with highly viscous media. The integrated cutting edge of the gate also enables effective separation of solids and deposits, preventing blockages and malfunctions. Solid media materials and fibers, which are typical for applications in sewage treatment plants, are cut through by the cutting edge before the tight seal is made against the elastic seat seal. In addition, the gate guide is interrupted along the stroke length so that contaminants can be expelled.

Thanks to their high-quality construction and low-maintenance design, GEFA knife gate valves have a long service life, even under extreme operating conditions. This not only reduces maintenance costs, but also ensures high system availability and long-term operational reliability.

Their main application is in piping systems for conveying mechanically dewatered sewage sludge or biomasses with high dry substance contents. Even materials with dry matter contents of up to 50% are nowadays conveyed in piping systems with the aid of pistons, screw pumps or eccentric pumps. Due to the long pipelines and geodetic height conditions in the plants, delivery pressures of 20 to 50 bar are generated, in some applications even higher. Pipelines and especially the valve technology used must be able to adapt and withstand the extreme requirements.

In these areas, the GEFA knife gate valves of the AT300 series, which can be used at pump pressures up to max. 40 bar, have proven their worth for years. Applications include chamber filter presses or centrifuges for sewage sludge drying, storage and loading of dewatered sewage sludge or in piping systems in fermentation and biogas plants.

For the higher requirements, GEFA Processtechnik GmbH has added the AT750 series to its product range. This covers applications with operating pressures up to 100 bar. In a sewage treatment plant in southern Germany, for example, ball valves that became sluggish after a few operations due to deposits of the medium in the dead spaces and had to be removed for inspection were successfully replaced by this gate valve.

Installation of DOMINO high pressure gate valves AT750 DN 150 PN 100 as a replacement for the previously installed ball valves, which blocked after a few operations due to storage of medium in the dead spaces.

• Medium: dewatered sewage sludge, 24-28% dry matter content
• Operating pressure: max. 50 bar
• Operating temperature: 20°C
• Switching frequency: 10/year (switching without pressure)
• Actuation: E-drive Auma, rising spindle

The biological purification of wastewater in sewage treatment plants is based on the targeted introduction of oxygen into so-called aeration tanks. There, microorganisms break down organic impurities, thereby purifying the wastewater. Precise control of the air supply is of crucial importance here. It ensures an even supply of oxygen to the microorganisms and helps to avoid over- or under-aeration. At the same time, optimum air control helps to minimize the energy consumption of the system, as inefficient aeration would be associated with unnecessarily high energy consumption.

Conventional control valves such as butterfly valves often have high pressure losses, which means that more energy has to be used for ventilation. This leads to rising operating costs and can impair the efficiency of the entire system. The GEFA-DOMINO AT200R control valve offers an optimum solution to this problem. With its specially developed control orifice, it enables a linear control characteristic and ensures precise control of the air flow - even under fluctuating operating conditions. Thanks to its flow-optimized design, the control slide valve also minimizes pressure losses, which has a positive effect on the energy consumption of the sewage treatment plant.

Discover how the use of DOMINO AT 200R control gate valves as a replacement for butterfly valves on aeration tanks in sewage treatment plants not only improves the control characteristics, but also leads to considerable energy cost savings. Here, using the example of a municipal sewage treatment plant, we present the outstanding advantages of our innovative technology.

• Medium: Air
• Operating pressure: 65 bar abs.
• Operating temperature: 70 °C
• Volume flow: 3700 Nm³/h
• Pressure loss valve: 1.98 mbar at 100 %