Each drop will go to the Baltic Sea
Although the state of water purity in the Vistula has improved significantly over the last several years, it is still the largest source of pollution flowing into the Baltic Sea. The pollution flowing by the Vistula in Bałyk causes periodic blooms of water, and this, apart from the natural effects, also causes the closing of seaside bathing areas. What is worse, pollution also carried by the Vistula is the reason for the continuous expansion of the dead anaerobic zones in the Baltic. Unfortunately, this problem will already reach very large sizes. Currently, as much as 14% of the Baltic bottom is a biologically dead area and is currently the largest such area in the world.
The cause of dead zones is too much biogen, i.e. nitrogen and phosphorus compounds (called biogens) in water. A large amount of nutrients causes a massive bloom of algae and cyanobacteria. Dying algae sink to the bottom of the tank, where they decompose. This process consumes oxygen accumulated in bottom layers of water. When there is a lack of oxygen, the number of anaerobic bacteria increases, which continue to decompose and at the same time produce hydrogen sulfide harmful to marine organisms.
The Warsaw accident will unfortunately make this situation worse. However, it seems that if the drainage of sewage to the Vistula is quickly stopped, this impact will not be significant, thanks to the self-cleaning processes of the still wild Vistula.
Happiness in misfortune - self-purification of natural rivers
The Vistula is still a largely unregulated river. A wild, unregulated riverbed promotes water mixing, which significantly increases its oxygenation, which is necessary for self-purification processes of the river. In addition, the nutrient loads that go to the Vistula from wastewater and crop fields undergo transformation due to denitrification (from nitrates to molecular nitrogen) or mineralization (phosphates). Molecular nitrogen is released into the atmosphere as a chemically neutral gas. Nitrates are also directly absorbed by plants and other self-living organisms, which in the natural, unconverted river is more than along a straight channel. Phosphorus compounds found in municipal waste water get there mainly together with detergents. In surface waters, the natural presence of phosphorus fluctuates periodically. The highest concentrations occur in autumn, winter and spring. Phosphorus is one of the basic biogenic indicators, causing massive growth of algae and higher plants. Currently, the growing season is underway, so the load of organic substances is still built into the plants.
Therefore, the Vistula River and its natural character, unique in Europe, significantly reduces the effects of the accident, which could have a much more destructive impact if the river was sewage system.
The Voivodship Inspectorate's reports, which are investigating the effects of the breakdown on an ongoing basis, show that the amounts of biogens in the Vistula immediately below the emergency discharge of sewage show large exceedances of the biogens: ammonium nitrogen, total nitrogen and total phosphorus, as well as chlorides. However, after 60 kilometers, these indicators improve and return to the values meeting the criteria of waters of the 2nd class of Uniform Surface Water Parts. (Tab. 1)
Tab. 1: Results of the Vistula water quality tests by the Voivodship Inspectorate for Environmental Protection. Source: WIOŚ Warsaw
The failure in Warsaw caught the attention of the public. However, one should be aware that similar failures, illegal discharges and other irregularities are unfortunately not uncommon.
In 2018, a similar failure occurred in Gdansk. Then, in a short time 50,000 m3 of untreated wastewater flowed into Motława and then into the Baltic Sea.
In 2015, 100 million liters of wastewater was drained into the Vistula in the center of Warsaw for 5 days in connection with the construction of a collector in the northern part of Warsaw. Unfortunately, it was only then under the pressure of the media that this fact was disclosed to the public.
Unfortunately, the situation is even worse on smaller watercourses. An example of this could be the Warsaw Służewiecki Stream - a 15 km long river, entirely lying in Warsaw. Its banks are heavily regulated, in many places built as a channel. From the results of the inspections carried out by the Provincial Inspectorate of Environmental Protection and the Municipal Police in 2016, it turned out that out of 141 inlets, only 20 had water permits to introduce sewage into waters. [I]
Other pipes discharge sewage illegally.
Such examples could be multiplied. Anglers and canoeists say that the practice of periodically draining untreated wastewater, e.g. under the cover of night, is unfortunately quite common.
Such situations appear to indicate the need to improve the situation. It is not just about increased controls and improvement of emergency procedures. It is all about broader cooperation between institutions responsible for the state of waters in Poland.
Cooperation as a response to failure
Work on minimizing the effects of the current accident in Warsaw shows how important the cooperation of various institutions is: waterworks, MPWiK, Polish Waters, the army, etc. Already now, thanks to this cooperation, wastewater entering the Vistula is ozonized (this kills most harmful bacteria and accelerates the distribution of pollution) and they are mechanically cleaned on 3 grates, thanks to which no larger solid pollutants reach the Vistula. There is also a chance that in the coming days sewage will stop flowing directly to the Vistula.
In response to crisis situations and strengthening cooperation between industrial and self-treatment plants, REC Polska is involved in the BEST project - Increasing the Effectiveness of Wastewater Treatment of Industrial Wastewater Treatment Plants, together with organizations, companies and local governments from six countries of the Baltic Sea basin. Therefore, we also see in the current problem the opportunity to engage in a dialogue to strengthen the procedures for quickly eliminating this type of threat.
The total budget of the project is EUR 3 592 237.82 (ERDF 3 284 027, 21 Euro)