Preventing waste water overspill in sewage pools case study

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Courtesy of Solid Applied Technologies Ltd. (SolidAT)

Solid's SmartScan 50L provides an ultrasonic solution for effective sewer management in various locations.

The waste water department of Jerusalem municipality in Israel is responsible for managing the city's complex sewer system. The system incorporates several sewage pools distributed in various locations, some of them in hard to reach locations.

The problems

The city of Jerusalem, with a population of some 670,000 inhabitants, controls large amounts of waste water produced daily. The waste water is conveyed through a complex system of sewers across the city to the waste water treatment plant. Some of the sewers are located in remote places, difficult to approach and therefore not regularly serviced. Rainy weather, or refuse blocking the drainpipes entering the sewers, can cause the water level to rise and overflow, causing damage to the surrounding area. The sewers usually contain pumps activated by changes in the water level to prevent overspill of waste water.

The sewerage department engineers sought a solution for more accurate control of these sewers and prevention of water overflow. Until recently, the sewers were equipped with mechanical float devices that were configured to a specific level of water and could activate a pump or an alarm system when the water level rose. However, these devices are not sufficiently accurate and tend to wear out in time. Moreover, several float devices had to be installed in each sewer to detect the level at each point.

Another problem was to locate the problematic sewer and to repair it promptly, before any actual damage was done. This operation took time, in many cases too late to prevent the damage to the surroundings. Typically, sewer's environment is known to be gassy and tend to produce foam as result of the waste water nature. These phenomena makes the water level difficult to measure and can cause inaccurate readings.

The solution

The Jerusalem municipality decided to install the SmartScan 50L in one of its remote sewers, where maintenance is difficult and remote control is preferable. The SmartScan 50L sensor was positioned inside the sewer pool and the electronic unit outside it. The pool contains ladders and pumps which cause obstructions and make it difficult to obtain accurate measurement. To overcome this difficulty, a sophisticated algorithm available in the SmartScan 50L, as well as in other Solid's products, was used to scan the pool for obstructions and to compensate for them in future scanning. Furthermore, its glass reinforced epoxy sensor enables the SmartScan 50L to cope with the corrosive environment of the sewer. With its ultrasonic capabilities the SmartScan's 50KHz sensor overcomes the challenging environment of sewers that includes foam and gas and provides accurate readings of the sewage level.

The SmartScan 50L was connected to a PLC that controls the pumps in the sewer according to the water level indicated by the SmartScan. Continuous readings are supplied by the SmartScan, thus providing the maintenance engineers with an updated picture of the sewer.

Summary

The Jerusalem municipality replaced the old float devices used in the past. It can now receive readings of the water level in the sewers 24/7 and prevent overflow and enviromental damage.

The SmartScan 50L' sensor is water-proffed to meet IP67 standard which enables it to work in wet areas. Meaning that in cases of water overflow it will keep on supplying continuous measurement.

Furthermore, the SmartScan 50L internal control processor in charge of five independent SPDT relays can be used to control pumps and other equipment in the sewer.

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