Smart system traps stormwater pollution before it reaches rivers

A system developed by Tallinn University of Technology researchers could use sensors in drainage networks to trap the dirtiest stormwater before it reaches bays and rivers, ERR reported.

Led by Kristjan Suits and Ivar Annus, the researchers tested the system in a computer model of a nearly 270-hectare catchment in Viimsi municipality serving about 10,000 people.

They selected four locations in the area’s pipes and ditches and fitted them with virtual sensors measuring water levels and turbidity. The model then simulated heavy rainfall and monitored the system’s response.

When the system tracked both water levels and turbidity, the amount of suspended pollution carried into the environment fell by half during small and medium-sized rainfall events, and in some cases by nearly 80 percent. The system also delayed the discharge of the dirtiest water, known as the first flush, by more than 24 hours.

The system did not increase the risk of street flooding by deliberately retaining the stormwater. As rainfall begins, the sensors detect rising water levels and automatically close the drainage outlets. The water remains in ditches, ponds and pipes, allowing solid particles washed from streets to settle instead of flowing immediately into rivers or the sea. If water levels rise dangerously and threaten to flood streets, the sensors send an alert and the gates reopen.

Unlike systems that use rain gauges to predict when rainfall will start or end, this solution makes decisions based solely on the behaviour of water flowing through the drainage network.

The researchers cautioned that the system may not work as smoothly in real-world conditions. The sensors would require regular maintenance, the relationship between turbidity and pollution would need to be calibrated for each sensor, and the system would have to be regularly cleared of sediment.

The findings were published in the journal Urban Water Journal.