Rakkola river is the river in Finland (Rakkolanjoki) and Russia (Seleznevka). In Russia, it flows through the territory of the Vyborg district of the Leningrad region, in Finland – through the territory of Lappeenranta. Its length is 53 km (20 km in the Russian territory). The source is near the town of Lappeenranta, the mouth is in the Vyborg Bay of the Gulf of Finland.

According to the state water register of Russia, the river belongs to the Baltic basin district, water management section of the river belongs to the basin of the Gulf of Finland from the Russian border with Finland to the Northern border of the basin of the Neva river sub-basin of the river Neva and the river basin of Lake Ladoga  It belongs to the river basin of the Neva river (including the river basins of Lake Onega and Lake Ladoga).

From the Finnish side of the border, the Rakkola river is often considered with Haapa lake (Haapajärvi) because of the similar presence of water pollutants.

The main problem associated with the Rakkola river nowadays remains the pollutions of eutrophication and phosphorus

The main pollution sources on Finnish territory are treated wastewaters from the town of Lappeenranta (40%-60%), agriculture (20%-40%), and natural leaching (15%-20%). Another pressure factor is the limestone industry. The inertial load of Lake Haapajärvi also contributes to the pressure; this load originates from nutrients, which have been accumulated during a long period of time.

The overall pollution load is too big compared to the size of the water source and its run-off. This is one reason for its poor water quality. The wastewater treatment plant is not yet sufficient for Rakkola river water purification.

Several studies investigated the water quality of the Rakkola River basin and concluded that water contaminants from the wastewater affect the river water quality greatly. The water contaminants were researched in the following studies as well, leading to the conclusion that the main pollutions are eutrophication, phosphorous, and nitrogen.

Research groups from Russia and Finland, the partners of the CBC OneDrop project are currently testing water samples taken at the Rakkola river and Haapa lake. The total amount and diversity of water contaminants are needed to discover first, before applying water treatment with sodium ferrate.

The research group from Saint Petersburg State University is taking water samples from the Seleznevka river on the Russian part of the border in North Karelia.

On November 4, water samples were taken from the Seleznevka River. Sampling was carried out at three points. The first point was after all settlements. But before the place where the Malaya Lipovka river flows into the Seleznevka river. The second point was before the village of Luzhayka. The third point was in the village of Kutuzovo. The village of Kutuzovo is located in a 5-kilometer zone before the border area between the countries. Therefore, the third point is the closest one to the border where water can be taken.

During sampling, the coordinates of the sampling site, air and water temperatures, weather conditions, and sampling time were recorded. The weather was changing during the day from sunny to rainy. After taking and preserving the samples, glass and polyethylene bottles were placed in a portable refrigerator to maintain the temperature of 4 ° C.

The next day, the samples were delivered to the Institute of Chemistry of St. Petersburg State University (SPbSU) for analysis.

The research group from LUT University is taking water samples from the Rakkolanjoki on the Finnish part of the border in the South Karelia region.