The climate is changing and so are heavy rainfall events. Floods, high water and mudslides are to be expected. Heavy rainfall is a particular challenge for our sewerage system. Especially for combined sewers in which wastewater meets rainwater. The sewerage system then reaches its limits. Overflows occur.
A wastewater treatment plant can only treat a certain amount of water in one day.
When rainfall causes the volume of water in the sewer system to rise sharply, mixed water – wastewater or sewage mixed with rainwater – is discharged into public watercourses.
Due to the pollutants it contains, untreated mixed water poses a threat to our environment.
Rain overflow basins or combined sewer overflow basins prevent this by storing excess water and releasing it to the sewage treatment plant at a later time.
Why should you monitor your rain or combined sewer overflow basin?
1. Meeting legal requirements
The regulations regarding wastewater treatment – and therefore also regarding rain overflow basins – vary from country to country. In some countries, such as Germany, legislation already requires the documentation of water pollution. In addition to the requirements of authorities for logging of stormwater overflow data, the data is an important factor in planning the expansion of residential areas.
2. Protecting the environment and water bodies
As already mentioned, the combined sewer can become overloaded during heavy rainfall. If sewage mixed with rainwater is discharged, public waters are polluted. In order to take appropriate action, it is necessary to know exactly how much mixed water has leaked from the sewer.
60% of Austria’s water bodies need to be restored because they are not in good condition. And only 15% of Austria’s waters are still in very good condition.
3. Preventing clogging
During heavy rain, not only rainwater flows into the sewer Mud is washed up from the surrounding fields and meadows. Dirt and flotsam are swept away by the water. This clogs the dirt trap and the sludge seals the holes in the manhole cover. The water shoots over the manhole cover. The water masses make their way and flow into deeper basements and garages. By monitoring the sewer and overflow basin, such a blockage can be detected and appropriate action can be taken.
4. Early warning as a service for citizens
If the sewer is overloaded, the pressure in the shaft will also increase. The manhole cover lifts and a large amount of mixed water escapes. If the manhole cover is located on a road, traffic is affected or even can accidents occur. If the increased pressure is registered, it is possible to react early and set up roadblocks.
Targets for documenting water pollution
In the event of persistent heavy rain showers, an overflow occurs even in the rain overflow basin. Although the water is pre-cleaned in the basin, the water itself was not yet in the treatment plant at that time. Dissolved pollutants as well as micropollutants from detergents, cosmetics and medicines are still in the water and enter public waters.
In Germany, for example, legislation already requires documentation of water pollution. But even if it is not mandatory, the pollution of public waters should be recorded.
The following targets are necessary for this:
- Frequency of pelvic congestion
- Duration of discharge events
- Frequency of discharge events
- Discharged water quantity
3 steps to document water pollution
Using the platform feature, the above target values can be determined in three steps.
- Measurement of the water level
- Settings in the platform
- Outflow determination in the platform
1. Measuring the water level
In the first step, the water level in the overflow basin is measured. With the following data loggers including software, you have a ready-made solution that can be adapted quickly and easily. You do not have to program, but configure yourself the logging of the rain overflow within a few minutes in the platform.
This is what it looks like in the platform:
2. Settings in the platform
Next, enter basic information about your rain overflow basin once in the platform. This includes information such as the height and width of the clarifying edges as well as the threshold coefficient.
3. Discharge detection in the platform
After the settings have been saved and the water level has been recorded, the last step is to calculate the discharged water volume using the POLENI formula in the platform. The determined values, as well as the previously mentioned target values, are clearly presented in a protocol. This log is automatically generated on the fourth day of each month. In addition, the protocol can be created at any time for a single month or a whole year with a click of the mouse.
The following data loggers for level measurement can also be used for logging in the rain overflow basin after minor adjustments to the software. Please contact us if you are interested.
Live demo webinar on rain overflow monitoring
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