A new and innovative way to measure turbidity

2021-02-24 14:52:02

The Gothenburg case study is focusing on water quality related to construction sites. Monitoring is done both at the construction site and in the stormwater system, where the treated water ends up. Turbidity is an important parameter that gets measured to assess water quality.

The “Turbinator”

Today there are several types of sensors installed in the field within the case study of Gothenburg. We are currently measuring turbidity, water level, pH, conductivity and temperature at ten monitoring points. These parameters are a good indicator for water quality. Through this monitorization we can increase the knowledge about the impact water runoff from construction sites have on the water bodies. Also, it aims to be able to detect pollutants and give early warnings to the operators, to faster fix the problem and minimize the impact of the pollution.

To measure turbidity and water level in the stormwater system, the case study is using the “Turbinator” (working title), a sensor developed by IVL Swedish Environmental Research Institute, who has a patent on the technique used by the sensor.

“The sensor started as an idea three years ago. After discussions with municipalities and experts within the water sector, we identified a huge need for a product like this. The main challenges where the sensor could help the cities are environmental monitoring, preventive maintenance and leak detection in their sewage network. When monitoring turbidity in difficult places as in the stormwater grid you always want to minimize the maintenance since it is hard to access the sensor. Also, this sensor can be produced at low cost and hence be suitable for large deployment in the sewage network.” - Fredrik Hallgren, Project Manager, IVL.

How it works

The sensor sends a laser beam into the water, takes a photo of where the light hits the surface and uses an AI algorithm to calculate the turbidity based on the photo. To develop the algorithm, IVL has gathered thousands of images together with reference measurements. The images are used in the training process of the algorithm.

Figure 1 Sketch of the Turbinator’s functionality.

Figure 1 | Sketch of the Turbinator’s functionality.

The Turbinator is contactless and installed well above the water level. Since the sensor is not in contact with water, it does not need to be cleaned, which minimizes the need for maintenance drastically. The sensor is battery powered and does not require any external power supply. Currently, the sensor uses LoRaWAN (Long Range Wide Area Network), a wireless communication protocol to transfer gathered information to Talkpool’s servers which will be published on the SCOREwater platform.

The planning for developing the sensor started during 2019 and the development since then has been a journey.

“Since the start, we have come a long way in the development, and it is really great to be able to use the sensors in real environments and applications. We have learned a lot in this process and discovered and solved several issues we couldn’t foresee. It’s always exciting, and a struggle to develop software, hardware and communication simultaneously.” - Jens Wilhelmsson, Developer, IVL.

Figure 2 | A Turbinator installed at the construction site next to a reference sensor. It is installed above a tank of water and in the dark environment you can clearly see the laser beam hitting the water.

The first Turbinator was installed in the spring of 2020 and several more have been installed during the year. IVL has also built a test facility in Stockholm, Sweden to be able to increase efficiency in development as well as gathering more training data for the AI algorithms.

Figure 3 | Six cropped images put together from photos taken by the Turbinator. The laser hits the surface of the water at the top of the pictures. From left to right the amount of scattered light decreases, which means that the turbidity is lower and lower. In the three images to the right, a clear dot at the bottom is visible, which is where the laser beam hits the bottom of the water tank due to the combination of low turbidity and low water level.

The benefits that the Turbinator can bring to your city

The Turbinator is continuous developed and improved at IVL. It is used in several different projects to better understand its potential and its limitations in real world applications.

By monitoring turbidity and water level over time the data can be used to preventive maintenance of a city or municipality pipeline network for waste- and stormwater. This can lead to several benefits.

Increased capacity, which leads to less environmental impact and fewer floods.
Fewer manual inspections, which saves time / travel and creates fewer traffic disruptions.
Longer service life on the pipe network as you only flush when needed.
Leakage detection in the pipe network by monitor trends of turbidity in nearby sensors to distinguish local changes in sections of pipes.

If you are interested to learn more about the Turbinator, or have additional questions please reach out to Anton Jacobson, Environmental Engineer at IVL: anton.jacobson[at]ivl.se

Anton Jacobson | 24-02-2021

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The Turbinator is also being deployed within the SCOREwater project. This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no 820751