A Smart Solution to Measure Sewage Overflow

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Sewage i overflows are a big problem because they pollute the environment. In the example below you’ll learn how KELLER Netherlands successfully uses the DCX22AA datalogger i together with the KELLER "Logger" Software to solve the sewage overflow problem.
Sewage overflow occurs when more rain falls than the sewers can process. If there was no management facility in place, manhole covers would be launched into the air due to the enormous pressure, which builds up over a very short period by the large amounts of rainwater accumulating in the sewer.
In order to counteract this tendency, the sewage system has walls built in in several places. On the other side of the wall there is a river or a canal. When necessary the surplus of water flows over the wall into the natural water.
Of course this should only be an option in cases of emergency. Therefore, the local governments are forced by the national government to register the number of overflows and the total quantity of water, which is dumped into natural waterways. The KELLER "Logger" Software calculates the total volume of overflow, while the DCX22AA measures the water levels. It is achieved as follows:

The DCX22AA is installed into the sewer system with the level sensor placed as low as possible but NOT in the residue layer. The battery pot is installed just below the steel manhole cover on the pavement or the street.

Three trigger levels, by which the datalogger increases the logging speed, can be programmed in the "Logger" Software.

Trigger i 1 is used to activate expedited logging
Trigger 2 to switch it back to normal logging speed and
Trigger 3 to calculate flow and overflow quantities.

The following graph makes it easier to understand.

The Event Sequence

  1. Heavy rainfall fills the sewer
  2. Sewer cannot process the excess water
  3. Sewage overflow tank fills
  4. As soon as the waterlevel passes the "Trigger ON" value DCX22AA activates and begins measuring once every minute
  5. As soon as the water flows over the internal barrier it is called an official overflow
  6. When the water returns to below the "Trigger OFF" value the DCX22AA switches back to normal datalogging with 1 measurement per hour and the overflow has passed
  7. With Logger DCX the DCX22AA's memory is read out
  8. A special conversion module calculates the flow and volume as follows:
    1. From every measurement's water level, which is measured level sensor, the calculation is deducted. Only the water level on top of the sewer barrier remains
    2. From all the remaining water levels the average level is calculated and converted to flow (volume/time) with the formula of Poleni
    3. The average flow is multiplied by the total endurance of the overflow (end date/time-begin date/time), which results in the total volume of overflow waste water (time*volume/time=volume)
  9. Finally our software creates an official report of this overflow location

How the Flow is Calculated

  1. With our software the DCX22AA's memory is read out (data manager is used to read the GSM i -2 files). The advantage of a GSM-2 is the wireless transfer of data; i.e. the user does not need to be on site to retrieve the data.
  2. A special conversion module calculates the flow and volume as follows:
    1. From every measurement's water level, which is measured level sensor, the calculation value is deducted. Only the water level on top of the sewer barrier remains
    2. From all the remaining water levels the average level is calculated and converted to flow (volume/time) with Poleni's formula: Q = m x b x h 3/2
    3. The average flow is multiplied by the total endurance of the overflow (end date/time - begin date/time) which results in the total volume of overflow waste water (time *volume/time=volume)
  3. Finally our software creates an official report of the overflow location

The Report as Basis for Precaution Decisions

The report created by the KELLER software is used to report the number of overflows and the volume of waste water dumped into a “Waterschap“ i , which is a state-owned institute responsible for water management in Holland. If overflows occur too often, the National Government can force a local Government to build a waste water buffer - a large circular concrete tank with a capacity of thousands of m3s.

Construction of a Waste Water Buffer Tank


In this buffer the surplus waste water is buffered and when possible pumped to the waste water cleaning location.

Waste water cleaning facilities.

Used KELLER Products
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