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Long lasting, cost-effective solutions for water-related applications, integrating our customers’ know-how with KELLER’s H2O-expertise.
Sewage Overflow Measurement
Waste Water Level Monitoring
Avoiding Pump Failures
Continuous Level Measurement
A Smart Solution to Measure Sewage Overflow
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 DCX-22 AA 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 DCX-22 AA measures the water levels. It is achieved as follows:
The DCX-22 AA 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
- Heavy rainfall fills the sewer
- Sewer cannot process the excess water
- Sewage overflow tank fills
- As soon as the waterlevel passes the "Trigger ON" value DCX-22 AA activates and begins measuring once every minute
- As soon as the water flows over the internal barrier it is called an official overflow
- When the water returns to below the "Trigger OFF" value the DCX-22 AA switches back to normal datalogging with 1 measurement per hour and the overflow has passed
- With Logger DCX the DCX-22 AA's memory is read out
- A special conversion module calculates the flow and volume as follows:
- 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
- From all the remaining water levels the average level is calculated and converted to flow (volume/time) with the formula of Poleni
- 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)
- Finally our software creates an official report of this overflow location
How the Flow is Calculated
- With our software the DCX-22 AA'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.
- A special conversion module calculates the flow and volume as follows:
- 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
- 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
- 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)
- 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.
Waste Water Level Monitoring
Since 2007 KELLER Poland has installed more than 5000 pieces of Series 46 X transmitters in waste water applications. The transmitters are mostly used in newly built or upgraded lift stations.
The 46 X level transmitters serve as a main sensor for waste water level monitoring, whereas the floating switches are used as a secondary control element. The main advantage of the 46 X is a chemically resistant AL2O3 diaphragm with gold layer, which is also more immune against mechanical damage when compared to the thin steel diaphragm used in piezoresistive transmitters. Another huge advantage are the modern digital electronics, which allow many users to take advantage of MODBUS i communication, as well as a freely scalable 4…20mA output. The outstanding reliability of the 46 X in this extremely tough application deserves to be mentioned too.
Liftstations
A Non-Fouling Solution to Avoid Pump Failures Resulting from Grease Accumulation
In wastewater measurement, accurate readings are essential to ensure proper pump operation. Failures in this area result in unhygienic liquid waste overflow i and costly repairs to pump mechanisms.
False Measurements Due to Equipment Malfunction
In Newport News, Virginia, several restaurants were built in an area serviced by the same municipal wastewater lift stations. The introduction of heavy grease content to the wastewater caused the existing level measurement equipment to foul, and fail.Antiquated Solutions
Prior to the development of the commercial district, the Newport News Waterworks and the Hampton Roads Sanitation District relied on a combination of mechanical floats and traditional submersible level transmitters. Once the restaurants were in operation, the increased volume of grease would cling to both instruments and, as a result, both the primary and redundant level measurement failed to properly transmit level data to the pump controller.The accumulation of grease to the submersible level transmitter clogged the pressure ports, which blocked the free flow of liquid, making a proper application of hydrostatic pressure to the sensing diaphragm impossible. On the redundant float switch, whose purpose was to trigger the pump in the event of a failed level transmitter, the accumulation of grease blocked the mechanical operation of the float ball. With the level transmitter and backup system inoperable, the affected lift stations would fail, either reading too much wastewater, or too little, which caused the pumps to run continuously or not at all.
Kynar® Diaphragm for Superior Abrasion and Puncture Resistance
Several instrumentation companies offer non-fouling products, which offer only minor variations of their existing and unsuitable solutions. These instruments use a Teflon-coated elastomer diaphragm that is relatively weak and prone to puncture. Their answer is to employ a bulky protective cage, consisting of a shield mounted on bolts and standoffs. However, these shields can collect rags, grease and biosolids from the wastewater, which leads to erroneous readings.Newport News officials contacted KELLER, whose 36 XKY, also known in the U.S. as the LevelRat, provided a unique approach to wastewater level measurement. The tougher Kynar® i diaphragm employed on the 36 XKY provides superior abrasion and puncture resistance relative to other “non-fouling” solutions. This design also minimizes the 36XKY profile, creating a sleeker design without the need for bulky shields, resulting in a truly non-fouling instrument.
Water Treatment Plant
With 36 XKY KELLER level transmitters pump failures due to grease accumulation as well as the use of bulky protective cages belong to the past. The solution combines the non-stick quality of Teflon with superior toughness and a resistance to abrasion.
Continuous Level Measurement Instead of Float Switches
Switching from float devices to a modern solution with the 26 Y KELLER Level Transmitter provides a continuous measuring system to control wastewater levels.
Inefficient Wastewater Level Measurement System
The customer needed a wastewater level measurement system, which was initially solved with floating switches. Switch one would cause the tank to fill when the level dropped to a minimum, switch two would stop filling the tank at maximum level, whereas switch three acted as an alarm not to refill the tank.
Taking the Shortcut
Instead of using several floating devices, the company opted for the 26 Y KELLER Level Transmitter.
The main advantages of hydrostatic measurement compared to float switches in an application with wastewaters are:
- Hydrostatic level sensors do not detect foam as a level of liquid (as it is the case with ultrasonic sensors), and therefore provide precise level values
- No false signals because of no mechanical parts inside
- Continuous measurement
- Level values can be read off a display
Sewage i Pumping Stations Equipped with Continuous Measuring System to Control Level in Wastewater Capacity
Example of Wastewater Capacity with Level Measuring Systems
