The sensor system measures the flow of the river and the sewage tanks in real time. It has already alerted 22 connections that have been diverted in order to lower the effluent treatment bill.
Tratave, the company responsible for the Vale do Ave Integrated Pollution Control System (SIDVA), has developed an intelligent real-time monitoring system for the flow of the river and the effluent that is transported through the high-level sewage pipes in the municipalities of Guimarães, Vizela, Vila Nova de Famalicão, Santo Tirso and Trofa.
The measurement is made by sensors and is directly linked to a computer program that sends alerts whenever there is a significant deviation from the amount of sewage being transported. If the amount of effluent flowing through the pipes is low, “we’re looking at a possible obstruction or even a pumping station stoppage”, explains António Pereira da Silva, a civil engineer at Tratave who developed the system.
In other words, if the sanitation flow is abnormally low, the polluting effluent that should be flowing into Tratave’s pipes is most likely falling into the river or along the banks, since the SIDVA network is installed along watercourses. Conversely, if the flow is abnormally high and it’s not raining, “it’s either industrial or it could be a break in the network”.
Another 20,000 euros on the bill
Over the years, some industries operating in the SIDVA area have created illicit connections to the sewage network, allowing them to drain effluent into the network without anyone knowing where it was coming from, in order to reduce their treatment bill.
Now, whenever one of these illegal networks is used by an industrialist, the increase in flow sends a warning signal to Tratave which, in turn, goes to the field to find out the causes. “We’ve detected 22 irregularities that have been corrected thanks to the implementation of the system,” António reveals. Some companies were paying only 20% of the actual flow rate and the adjustment meant, in some cases, an increase of 20,000 euros in the monthly bill.
In order to measure with high precision, 31 sensors were placed, one for every 1.5 kilometers of high-level sewage network. Each sensor has been programmed to record a certain amount of average flow and, “if there are any changes, it sends out an alert because it knew what was supposed to arrive there,” adds Cláudio Costa, Tratave’s general manager.
At the company’s headquarters, on a television set fixed to the wall, António can follow in real time the status of the flow detected by each of the 31 sensors installed in the network.
