Cyanobacteria in Miedwie Lake. Water in Szczecin is safe

Amid concerns about cyanobacteria in Miedwie Lake, the Municipal Water and Sewerage Company has issued a statement assuring that Szczecin’s water has been confirmed safe and clean through a series of tests. It remains safe to drink without boiling and filtration.

Nearly 90 percent of water supplied to Szczecin comes from Miedwie, Poland's fifth largest lake, with a surface area of 3,800 sq. m. The large size of the reservoir is well-illustrated by its dimensions – It is 16.6-km long, 3.2-km wide and goes as deep as 43.5 m. Our water intake is located on the western shore, 255 m from the shoreline, at a depth of 16-18 m from the water table. The water is conveyed by two pipelines with a diameter of 1,200 mm to enter pump station chambers through mechanical sieves that filter out large objects – shells, fish and plants. Afterwards, it is transported to a water treatment plant situated 2.5 km from the pump station.

The water treatment plant carries out a series of procedures and processes to make sure our tap water is of a top quality. In fact, it is at least as good as bottled water. What does the treatment process specifically involve? It consists of the following steps:

- ozone (O3) pre-disinfection,

- coagulation,

- sedimentation,

- anthracite-sand bed filtration,

- intermediate ozone (O3) oxidation,

- granular activated carbon bed filtration,

- final disinfection with chlorine dioxide (CIO₂).

Following this sequence of processes – described here in very simplified terms – the water is conveyed to two service tanks with a volume of 5,000 m³ each. From there, it flows by gravity to Szczecin, which lies about 32 km from Miedwie.  This is facilitated by two trunk water mains – the first one with a diameter of 1,200 mm and the second one with a diameter of 700 mm. The first pipeline goes to ZPW Pomorzany’s (a water production company) tanks, where water is disinfected again and then fed into the city’s left-bank water supply network. The second pipeline leads to the water pump station in Kijewo, from where it is supplied to the right-bank part of Szczecin.

The water is being monitored on an ongoing basis. There is a laboratory at the water intake which carries out daily physico-chemical and bacteriological tests of raw, processed and, in the end, clean water. Every day, it investigates a total of 26 parameters, with 60 analyses being performed monthly.

Its well-qualified staff, numbering almost 70 and increasingly using advanced automation and monitoring systems, makes sure that the water treatment station operates properly, the process regime is maintained and water is being supplied to the city without interruptions. The lab works in a three-shift, 24/7 system.

“We post regular updates on water quality on our website,” said Hanna Pieczyńska, press spokeswoman for the Municipal Water and Sewerage Company.