Overview of the sewage treatment process
April 2012
Valves, Actuators & Pump Control
Initially, incoming domestic sewage is discharged into the pre-settling basin where it is mechanically cleaned. Then the pre-purified sewage is conveyed to the activating basin, where, in the first, the nitrification phase, oxygen is added in the form of compressed air to support the growth of oxygen-consuming bacteria to form what is known as ‘activated sludge’.
In the second, the denitrification phase, no oxygen is added subjecting the previously strongly multiplying bacteria to oxygen deficiency. They now have to utilise other oxygen compounds, thus the chemical compounds of the nitrogen oxides are cracked and rendered harmless.
In the last phase the sewage is placed into the final sedimentation tank where the remaining matters are precipitated by adding ferric chloride. In this process the heavier substances settle and the lighter substances float to the top and are skimmed off. Then the clarified water can be passed into rivers. During regeneration, compressed air is added to the settling basin beneath the surface. The intermediate and end valves used are metal butterfly valves. In addition to manually operated types, automatic valves with motorised actuators are used. Sizes range from DN 80 to 1000 mm.
Plant technology
There are several large air pumps in a compressor house from where the air, compressed to 4 to 6 bar, is brought together in a collecting main and transported to settling basin through a piping system. At the border of a basin the collecting main opens into a manifold from where it discharges into the sewage along the basin, under the surface the compressed air is distributed via nozzles. Each pipe section and the individual feeding conducts are closed by butterfly valves. The compressor pipes and main distributors are equipped with motorised butterfly valves, the individual distribution pipes with manually operated butterfly valves and the sewage inlet and outlet is controlled by butterfly valves installed under water. Their gear is flooded and the motorised actuator is mounted outside the basin.
The valve solution
Gemü wafer-type butterfly valves in cast iron/epoxy coated (400 µm) with stainless steel discs and nitrile packing ring (NBR/Perbunan) in sizes DN 80 to 100 mm. The butterfly valves up to DN 125 are manually operated by means of a lever, they have a LUG design, and those larger than DN 400 are in double flange design. The flange class is PN 10 (DIN).
For more information contact Philipp Tholen, Gemü Valves Africa, +27 (0)11 462 7795, [email protected], www.gemue.co.za
Further reading:
Compact valve position indicator
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson’s new TopWorx DVR Switchbox is an entry-level addition to the DV Series of valve position indicators. It combines a durable resin enclosure, compact size, and a patented cam design that provides a reliable valve position feedback for water and wastewater systems, food and beverage production lines, and industrial utilities.
Read more...
Precision, control and performance in regulators and control valves
Valve & Automation
Valves, Actuators & Pump Control
Cashco has long been a trusted name in industrial control solutions, offering a broad range of regulators and control valves designed to meet the rigorous demands of various industries. There are two key Cashco product lines, its regulators and the Ranger QCT control valve.
Read more...
Advanced solutions for valves
Bearing Man Group t/a BMG
Valves, Actuators & Pump Control
BMG delivers state-of-the-art valve solutions to diverse industries across Africa, in collaboration with InterApp, a global leader in the design and manufacture of high-quality valves.
Read more...
ENERGYValves expands operations
Valves, Actuators & Pump Control
ENERGYValves is expanding its operations with a new facility in Cape Town. The new premises will significantly enhance the company’s capacity to serve the Cape Town market and surrounding areas.
Read more...
Revolutionising slurry management in mining operations
Valves, Actuators & Pump Control
Dynamic Fluid Control has launched the Vent-O-Mat Slurry Air Release Valve, designed to set new standards in performance and technology for the mining industry.
Read more...
Inspection system for leak detection in valves in hazardous areas
Extech Safety Systems
Valves, Actuators & Pump Control
Leaking valves in industrial plants not only lead to loss, safety risks and possible contamination and pollution, but also result in high economic costs. Therefore, valves in hazardous areas require regular proper inspection and preventive maintenance to ensure their functionality.
Read more...
High-flow solenoid valve
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has introduced the new ASCO Series 327C solenoid valve, which features a direct-acting, high-flow design that provides superior flow-to-power ratio. It permits high flows at minimum power levels, making it ideal for use in power plants, refineries, and chemical processing facilities.
Read more...
New system improves performance of magnetic drive pumps
Valves, Actuators & Pump Control
KSB Pumps and Valves has introduced its ground-breaking MagnoProtect system for the local petrochemical, chemical and general industry markets ,to enhance the safety and performance of its magnetic drive pumps.
Read more...
Emerson software optimises maintenance
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has announced the Plantweb Insight Valve Health Application, a powerful software tool that combines Fisher control valve expertise with advanced analytic algorithms. The new app makes it possible for users to visualise an entire connected fleet of valves, while prioritising actions based on the health index of each valve.
Read more...
Inline pumps for space-saving applications
Valves, Actuators & Pump Control
Pump manufacturer, KSB Pumps and Valves has introduced its latest EtaLine range of inline pumps, including the advanced EtaLine Pro for diverse applications such as HVAC, industrial recirculation, and heating systems.
Read more...
printer friendly version