Smart monitoring for sewer management

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October 2007 Sensors & Transducers

The Holon municipality sewage system uses Solid’s SmartScan 50 to provide a non-contact, maintenance-free ultrasonic solution with remote monitoring for problem prevention and effective sewer management.

Solid’s SmartScan 50 control units and cellular interface are mounted in a control cabinet up to 50 m away from the level measuring points

The Holon sewage system, located in the centre of Israel, comprises an old underground network serving private consumers and factories. The wastewater collection system consists of buried pipelines which convey the wastewater by gravity to the water treatment plant.

The problems

The municipality experiences frequent blockages in the system. The blockages can happen at any point without warning and can lead to an overflow at an inspection point resulting in an overflow into the streets. Rainy weather or litter blocking the drainpipes entering the sewers can cause the water level to rise and overflow leading to damage to the surrounding area. This is a great nuisance for the Holon area residents and results in frequent costly call outs for the Holon wastewater department. The authorities have to respond immediately and have no other option but to shut down all the water supply to the district while treating the problem.

When considering the right technology to monitor the level in their sewage system, the Holon sewage department engineers decided not to use contact level gauging devices since they could be prone to faulty operation at times of very high humidity and would require high maintenance. They concluded that contact level gauges would not be a cost-effective solution.

Because of the frequent blockages, the engineers also wanted a level measuring device that would be unaffected by sewage submersion.

The solution

Solid AT installed 3 SmartScan 50 devices with 50 kHz sensors as part of a successful Beta trial. The installation is at the inspection point well, attached to the internal ceiling. The distance from the sensor to the channel bottom is 2,5 m. All sensor cables are connected to the control units, which are placed in a control cabinet about 15 m from the inspection point well. The information regarding the sewage level is transmitted to the municipality control centre via cellular technology. This technology uses WEB/GSM/GPRS monitoring. The customer enjoys online monitoring via regular web access or via a mobile phone. The customer has defined trigger levels that generate SMS messages allowing the municipality team to detect the exact place of the problem and fix it prior to overflow.

Summary

The SmartScan 50, non-contact gauging device was found to be the most suitable device in this environment. The 50 kHz glass reinforced epoxy is highly resistant to the methane environment. Having an IP67 rating, the sensor is unaffected by complete immersion and provides reliable measurement after being flooded. The level information is monitored 24/7 via a website, and SMS messages send alerts when the levels reach low/high limits.

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