Sewer Overflow Monitor

Observator has developed her own hydrological monitoring system for sewage overflow: sewer overflow monitor. For good water management of the sewer system, it is necessary to register when the overflow takes place onto open water. The sewer overflow monitor monitors the level of the sewage water and registers the frequency and volume of the overflow into open water.


SewerGuard is a monitoring system for Combined Sewer Overflows. In a CSO, waste water is discharged onto open water when the capacity of the sewage system is exceeded. For proper management of the sewage system, it is necessary to monitor the level of the sewage water and to register the frequency and volume of the discharge onto open water.

With SewerGuard, monitoring equipment is installed in each CSO. The measured data is transmitted to a server computer via the mobile telephone network (GPRS). User-friendly software allows users to view recent and historical data. Also, automated overview reports can be generated and alarm conditions can be signaled.

The equipment installed in the CSO consists of:

  • A pressure sensor for measuring the water level.
  • A data logger with GPRS modem for logging the water level and transmitting it to the server.
  • A liquid level sensor (float switch) for activating the logger in case an overflow is imminent.

If the water level is low, the logger will wake-up twice a day, measure the water level, send it to the server and go back to sleep. Power consumption is extremely low in this case. If the water level rises high enough to activate the liquid level sensor, the logger will wake-up every minute to measure and store the water level. Every 15 minutes the stored values are send to the server. (The numbers are just examples.) Thus frequent data is available during high water, while power is saved during low water. For most CSO's the small battery in the logger (which powers the complete system) will last for one to two years.

The measurement data from multiple CSOs is received on a server computer. The SewerGuard software stores data in an SQL or other data base. The overflow rate (volume per second) is calculated from the water level and the physical structure and dimensions of the CSO. Advanced software allows multiple users to view the data in the form of charts and tables. The software generates easy readable reports showing the number of overflow events & the associated overflow volume. All data can be accessed via a web interface. Data can be exported in various formats.

The standard version of SewerGuard can easily be augmented with additional sensors, for example for measuring the level at two points or for measuring water quality parameters. Alternative power options (power grid or solar) are available. The software can be licensed or be hosted by Observator.

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