Quantitative Flow Analysis in a Rural Waste Water System

Quantitative Flow Analysis in a Rural Waste Water System

In the past, a rural sewage treatment plant that was designed for only a few thousand inhabitants was often temporarily overloaded after heavy rainfall.
Due to the fact, that flowmeters are usually not installed in such small waste water systems, it is impossible to identify who is responsible for the elevated amount of waste water which has to be treated. It is also impossible to estimate the percentage of extraneous water. Large quantities of waste water mean the pumps are used to a high capacity with correspondingly high energy consumption. Thus, the capacity of the water treatment plant was extremely high. On the other hand, the communities of the waste water association have to take into account the potential cost of completely separating waste water and stormwater in the extensive network.

As part of the expansion and modernization of its waste water treatment plant, the local waste water association commissioned external water experts to carry out a quantitative analysis of the existing waste water system and to draw up proposals on how to improve it. In line with measuring activities, they had to determine flow rates on individual waste water transport pipelines and correlate them to local precipitation.

In a fully filled pipe, the non-invasive FLUXUS flow meter accurately measures the volume flow rate by taking into account the flow velocity of the medium as well as the geometry of the pipe.

However, the pipes of small waste water systems are often only partially filled. The solution in regard to this challenge is to create a short measuring section with a fully filled pipe.
For this purpose, a short pipe section is simply inserted into the water duct with its outlet angled upwards so that the opening lies above the top of the straight pipe. This ensures that the short measuring section is always filled.

This type of measuring system - where the measuring tube is temporarily integrated into the duct system - is usually fitted with magnetic inductive flowmeters. 
However, it is much simpler and more practical with ultrasound:
The compact transducers are mounted onto the outside of the pipe wall and weigh next to nothing. As a result, it is very easy to insert the preconfigured measuring tube in the sewage duct. In addition to that, the clamp on transducers are not subjected to any wear and tear by the medium flowing inside the tube. The inertia-free acoustic measuring method is characterized by its extraordinary measuring dynamics. Even the slightest flow velocities are detected reliably. The strong transmitting power of the FLUXUS ultrasonic flowmeter also ensures reliable measurements even if there are coating formations inside the pipe. Even very high solid contents are accurately measured via the embedded HybridTrek mode of the FLEXIM meter.

The flow rates recorded by the FLEXIM meter are transferred via GSM to an Internet-based data transfer and acquisition system so that the measurements can be visualized and evaluated on any computer with an Internet connection. The entire electronic system along with its rechargeable battery fits into a compact, sturdy case which can be stored in the manhole during the measurement campaign. Measurements carried out to record effluent flow rates are ideal for effectively analyzing the waste water network. They provide network transparency which is a prerequisite for creating fair pricing. The empirical data obtained forms a basis for further optimization measures and possible capacity expansion.

Advantages

  • Flexim meters work where others don’t
  • Obstruction less
  • Reliable detection of waste water inflow rates
  • Collection of empirical data for network analysis as a basis for improving the canal system and designing a sewage treatment plant that meets demand
  • Flexible and cost-effective: a single measuring system for a wide range of measurements
  • Intelligent solution for accurate flow measurement even in partially filled pipes
  • No need to shut off or empty the sewage pipe when installing the temporary measuring equipment – no adverse effect on waste water disposal
  • Compact measuring system can be positioned easily in the sewage manhole
  • Reliable and accurate flow measurement even when there are high levels of solids and low flow velocities
  • Wireless remote transmission via GSM (mobile telephony) – measured values can be visualized, processed and evaluated on the PC regardless of location
  • Great for wastewater collections, treatment, and effluent disposal

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