The climate is changing and so are heavy rainfall events. These present a particular challenge to 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 volume of water per day.
When there is heavy rainfall, the volume of water in the sewerage system rises sharply and mixed water — i.e. a mixture of wastewater or sewage and rainwater — enters the public waterways.
Due to the pollutants it contains, untreated mixed wastewater poses a threat to the 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. Improvement of the drainage system’s data basis
Although stormwater overflow basins are an important component of combined sewer systems, they have been monitored much less frequently than wastewater treatment plants. Continuous logging enables reliable data to be collected on accumulation and discharge processes, allowing for a well-founded evaluation and optimisation of the overall system.
2. Monitoring the function and operational safety
Measurement data can be used to monitor technical equipment, such as throttles, pumps and relief structures. This allows deviations from target operation to be recognised at an early stage, even during a rain event when no one is on site, for example due to backwater or malfunctions.
3. Traceability in the event of malfunctions and operational incidents
In the event of malfunctions or damage, the logged data provides an objective basis for analysing the cause. This enables technical and legal traceability of events, making it an important prerequisite for the responsible operation of plants.
4. Data is key to sustainable planning
Long-term optimisation requires reliable information. By using recorded measured values, it is possible to realistically simulate and optimise rainwater overflow basins in a targeted manner. This can be used for the construction of new systems, hydraulic network calculations, or the implementation of measures to comply with water legislation, for example. This makes investments more efficient and effective.
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
The platform can be used to calculate the target values mentioned above in three steps.
- Measurement of the water level
- Recognising overflows
- Calculation of the discharged water volume (overflow)
1. Measurement of the water level
In the first step, the water level in the overflow basin is measured. Use one of the following data loggers and activate the “Overflow Log” add-on. This provides you with a ready-made solution that can be customized 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 the platform looks like when you have selected a Jellox Analog:
2. Recognising overflows
Next, the measured water level is used to detect potential overflow. To do this, you only need to enter some basic information about your rainwater overflow basin into the platform once. This includes information such as the height and width of the clarifying edges as well as the threshold coefficient.
3. Calculation of the discharged water volume (overflow)
In the final step, the volume of discharged water is calculated using either the POLENI formula or a base point table. Measurement of the water level and calculation of discharged water quantities form the basis for deriving the aforementioned target values. These values are clearly displayed in a log.
Each time the water level is measured, new data is added to the log for the current year or month. This means that you can view the latest data at any time, without having to wait until the end of the year or month for the calculation to be performed. The required logs can be accessed simply by clicking on the platform interface.
Here is an example of a monthly evaluation:
