Product category:
Waste-water handling, monitors + treatment
News Release from: Emotron | Subject: Svenljunga VSD application
Edited by the Processingtalk Editorial
Team on 22 November 2006
VSD units improve sewage plant
efficiency
Emotron variable speed drives and softstarters control pumps, blowers and mixers, and Emotron shaft power monitors protect other equipment on a new sewage works at Svenljunga
When the sewage treatment plant in Svenljunga, a community of 10,000 inhabitants, was renovated in the summer of 2005, investments were made in order to increase operational efficiency and reliability One measure taken was to install Emotron variable speed drives and softstarters to control pumps, blowers and mixers, and Emotron shaft power monitors to protect equipment
This article was originally published on Processingtalk on 8 Jun 2006 at 8.00am (UK)
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"We used to regulate most of the equipment manually, but today everything is controlled by Emotron products," says electrician Johan Arvidsson.
In a sewage treatment plant, the objective is to keep a constant flow despite the large variation in load during the day and night.
In Svenljunga, Emotron products ensure efficient operation continuously adjusted to demand.
Variable speed drives and softstarters regulate pumps, blowers and mixers, and shaft power monitors protect screw conveyors.
"One advantage of Emotron products is that they can withstand harsh environments and be located within the plant," says Johan Arvidsson: "No costly cabling or cabinets are required.
We also minimise the risk of damage and downtime, since we are warned in good time of process disturbances".
The Emotron products react immediately to deviations and send a warning or stop the process if operation is not optimal, for example if a pipe is blocked or a valve is not fully opened.
The operator can take action quickly in order to prevent damage and downtime.
Common and costly problems such as cavitation and dry-running can be avoided.
The stop sequence is a critical moment in pump operation, often causing stress on pipes, valves and other equipment.
The Emotron solution offers soft stops by gradually reducing the pump speed, thereby avoiding water hammer and other potential damage.
A total of 17 Emotron FDU variable speed drives are installed in the plant.
They control, among other things, three inlet pumps that pump in untreated sewage.
Two of the pumps are normally used to handle storm overflow water, i.e water that is allowed to pass the plant after only limited treatment, for example in the case of heavy rainfall.
The flow must not exceed 220 m3/hour in order for the particles that are to be removed to have time to settle to the bottom and not run out with the water.
If the flow is too high, the system regulates this by starting the third pump to pump water past so that the particles can settle.
The operation of the blowers supplying oxygen to the sewage water was also made more efficient by installing Emotron FDU variable speed drives.
"Until now the blowers were either running at maximum speed or standing still," says Johan Arvidsson: "That was wasting energy.
The Emotron FDU now continuously adjusts to demand, ensuring that the water maintains the correct oxygen content.
In this way we minimise our energy consumption and equipment wear".
The sludge scrapers in the sedimentation basins are monitored by Emotron M20 shaft power monitors.
The monitors send a warning or stop the process if operation is not optimal, for example if a scraper is blocked, a blade is worn or a chain is broken.
Equipment wear and downtime are minimised.
The monitors are connected to the motor cable.
No sensors are required.
Emotron FDU variable speed drives control the sludge pumps that pump out surplus sludge from the basins.
The FDU units are located in cabinets outside near the basins.
An eccentric screw pump that pumps sludge to a thickener is also controlled by an Emotron FDU.
An Emotron M20 shaft power monitor on the screw conveyor sends a warning or stops the process if a blockage occurs.
Mixers placed down in the basins are regulated by Emotron FDUs, as are the sludge pumps that pump sludge to centrifuges where it is dewatered.
Seven Emotron MSF softstarters control the screw conveyors for the centrifuges.
The sludge is used as fertiliser or sent for final disposal.
As Svenljunga sewage treatment plant was being renovated, the largest local industry, Elmo Leather, built their own treatment plant next to the municipal plant.
The sewage water from the tannery had been putting high demands on its capacity.
"Now our plant is rated at 3000 pe, compared to the 100,000 pe required to treat the sewage from Elmo Leather," says Johan Arvidsson.
The new Elmo Leather wastewater treatment plant is the first of its kind.
A fully biological process is used that has never been tested before on an operation that uses such large quantities of chemicals.
The EU environmental fund contributed to the financing and the good results mean that the company will show the way for other tanneries in Europe.
The new technique reduces nitrogen emissions by 80%, compared to 30% in the old plant.
Emotron variable speed drives control, amongst other things, the blowers that oxygenate the waste water.
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