Wastewater influx monitoring

Wastewater influx monitoring | Digital Water | InfoTiles

Leaking wastewater pipes allow surface water (eg rain) to penetrate the sewage grid which overloads the wastewater system resulting in the release of untreated wastewater. It also increases the riskcross-contaminationtion of drinking water. 

Influx occurs when water penetrates the sewage water grid from wet soil, or when drains are directly connected to the wastewater system. This makes the wastewater system sensitive to rainfall. Climate change has also resulted in more frequent and extreme rainfall events, which further amplifies the problem.  

 

When influx occurs, a lot more water than normal is pushed through the wastewater system, sometimes up to 10 times the intended load or more. This puts extra strain on the wastewater pumps, requiring extra capacity and energy to deal with the extra load. The pumps then push the extra water forward to treatment plants, which also need the capacity and dimension to handle the increased load.   

This overload of the wastewater system can also result in overruns and the release of untreated sewage into the environment. It also increases the risk of cross-contamination of drinking water and can cause disease.

With a lack of evidence of where the influx is occurring, many opt to increase the capacity of wastewater evacuation and treatment to avoid overruns. This, however, does not solve the underlying problem, and results in increasing investment and energy costs. 

To avoid environmenhazardszard and misguided investments into treatment capacity, the challenge is to determine when and where the influx is occurring, and to decide the right measure to close the influx leakage. 

InfoTiles applies control system (SCADA) data to analyse dry and wet weather behaviour. The amount of influx in every pump station is calculated in real-time, allowing you to see trends, resulting costs and where to focus maintenance. Once key problem areas have been identified, IoT devices can be placed in critical points, and included in the live dashboards to obtain more detailed measurements if necessary.  

For one of our customers, we discovered that the pumps were pushing 5 million m3 of wastewater per year, of which more than 1 million m3 was influx surface water (20%). The cost of treatment of this extra water was around 16 million NOK per year, or 1,5 mEUR, not including the energy costs of transporting the water to treatment. 

About 50% of the excess water was handled by 3 pump stations of about 30 in total (10%). This enabled the maintenance team to rapidly identify focal points for further measurements, and eventually the critical points to remedy in order to reduce the influx.  

Furthermore, the analysis discovered that some pumps were in constant overload. Influx was occurring even in dry weather. Upstream pipes were situated close to the banks of the nearby river, in soil that was constantly saturated by water from the river.  

In essence, the wastewater system was being used to absorb and pump river water, treat it, and release the water back into the river once cleansed. 

The pumps in question had already been chosen for upgrade due to the strain. This decision however had to be challenged, as an upgrade would lead to pumping river water to treatment faster. An alternative investment would be to improve the integrity of upstream wastewater pipes.  

Using InfoTiles, the actual costs of influx became clear to the customer, and informed financial and operational decisions could be made to improve the most vulnerable parts of the wastewater grid. 

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