By order of the Federal State Institution “State Research Institute of Industrial Ecology” (FSI SR&DIIE), researchers of the St. Petersburg Federal Research Center of the Russian Academy of Sciences (SPC RAS) have developed and successfully tested a technique for prompt detection of illegal discharge of waste by enterprises into sewers and water bodies based on the passive radio frequency identification technology using encapsulated RFID labels. The project results were partially published in the leading scientific journal “News of the Kabardino-Balkarian Scientific Center of the Russian Academy of Sciences”.
Protecting water bodies against industrial pollution is a critical task, since right now the said water bodies are the main sources of drinking water for millions of people, animals and plants. Their pollution can lead to serious health problems for the population, as well as to the destruction of flora and fauna, and the entire ecosystems. Clean water bodies are the most important factor for the successful operation of agriculture, fisheries, tourism, and for the comfortable life of indigenous peoples living nearby. Protecting the water resources against toxic substances is regulated by many legislative acts.
Nevertheless, cases arise when industrial enterprises illegally connect their wastewater to storm sewers not equipped with complex treatment facilities. Wastewater often contains toxic reagents, heavy metals, oils and other pollutants eventually ending up in water bodies through the said storm sewers.
The way to address this problem is to regularly inspect industrial facilities and monitor storm sewers to detect illegal connections and prevent pollution. However, most monitoring methods (visual inspection, smoke tests, dyes, flow monitoring, and chemical analysis of water) are either expensive or not versatile enough to detect all types of pollution.
“We have studied the possibility of using the passive radio frequency identification technology of the EPC Class 1 Gen2 standard for a prompt detection of unauthorized connections and discharges of industrial wastewater into storm sewers. It is based on the use of reasonably cheap sensors with a built-in RFID label, whose movement hrough sewer pipes can be tracked automatically,” says Vladimir Dashevsky, Senior Researcher at SPC RAS.
Core element of the sensor developed by specialists at SPC RAS is a passive RFID-label. It is just a chip assembled with a small printed antenna that stores information about the object and allows for its reading via a special RFID-reader from a distance of several meters. Passive RFID-labels are lightweight, compact and inexpensive. However, in sewerage conditions, reading RFID – labels is significantly hampered by the absorption of the radio signal by the earth layer thickness, as well as by the water shielding effect. Therefore, the main research was aimed at finding the optimal sensor design and methods for reliable reading in storm sewer pipes.
The method idea is that during control activities, sensors are dropped into the industrial facilities’ drain wells. At that, the EPC code specifying the place and time of each sensor’s discharge is recorded in the RFID-label. In the event of an illegal connection of industrial wastewater to the storm sewer, the sensor after some time ends up in the storm sewer’s control well, where its EPC code is read by a reader submerged into the well and ten transmitted to the data processing server.
The proposed approach allows for the simultaneous diagnostics of several drains of one sewer system, what distinguishes it from the conventional method involving the addition of dyes or isotopes to water. The time and location of the dropping, recorded in the memory of each sensor, allows for its identification and the unambiguous determination of its migration path, even when it takes quite a time.
To assess the sensors success while overcoming pipes of various bends, diameters and fillings, several stands simulating sections of storm sewers were assembled. In general, this work demonstrated the prospects of the proposed method. Based on the information collected at the stands, a design of the sensor’ case was improved.
Then the researchers performed a full-scale experiment on a straight section of a real storm sewer on the site of the industrial partner of the SPC RAS - ECOPROM (LLC), responsible for the operation of the sewer networks of the Obukhovo industrial zone in St. Petersburg.
“Experiments proved that RFID technology works reliably underground: all sensors that arrived to the control well were repeatedly and reliably read by the reader. However, their travel time along the pipes through shallows and blockages can be somewhat long and poorly predictable. To increase the speed and convenience of deploying the monitoring system, the operator's seat was equipped in a minibus. Nevertheless, in a general case, such a mobile post is obviously not enough.” – notes Vladimir Dashevsky.
Therefore, further development of the technology supposes a development of stationary automated complexes that would track sensors at the points of storm sewer discharges into water bodies. Automated monitoring of storm sewers will allow for prompt detecting the presence of an overflow of domestic and industrial discharges into the storm sewer and fining violators who discharge their emissions bypassing the treatment facilities.