Water intakes and water treatment plants
The city Toruń is supplied with ca 50% of its water from groundwater intakes.
These intakes include:
– “Mała Nieszawka”
– “Wrzosy II”
– “Czerniewice” – local intake which doesn't have connection with urban water-pipe network and serves only the residents of Czerniewice district
– “Jedwabno” which is an infiltrating intake
The remaining quantities of water are obtained from the “Drwęca” surface water intake.
CHARACTERISTICS OF GROUNDWATER INTAKES
Groundwater intakes (ground and infiltrating) are located within the Main Groundwater Reservoir - GZWP 141 “Lower Vistula Reservoir”. They all use the Quaternary aquifer.
These waters have features of typical fresh waters and they are described by low value of colour, low alkalinity, and TDS ranging between 400 and 600 mg/ dm³. The water is moderately hard or hard. These are bicarbonate-calcic waters.
The "Drwęca" intake is a bay intake of surface water from the Drwęca River. Water is taken form a water basin (approx 42 ha) which is part of the Drwęca River. This water basin is closed with a weir located in the bend of the river 12.7 km from the estuary to the Vistula River. Its role is to raise the water in the regulated channel of the river and holding the right level of water in the bay.
From this water basin water flows into the bay (approx 1700 m2 area) which is responsible for braking the river's drift with simultaneously leaving a deposit of bigger suspensions, stopping objects carried by the river (like: fish, the plankton and others). The bay ends with a chamber of intake which is linking the bay by a pumping station (first grade pumping station).
TECHNICAL DESCRIPTION AND TECHNOLOGY OF INTAKES:
1. The "Mała Nieszawka" water intake and water treatment plant
2. The "Czerniewice" water intake and water treatment plant
3. The “Jedwabno” water intake
4. The “Drwęca” water intake and the water treatment plant "Drwęca-Jedwabno"
MODERNISATION OF the “Drwęca- Jedwabno” Water Treatment Plant
After ordering the construction of a surface water intake and water treatment plant, it turned out that the quality of raw water obtained from Drwęca River is unacceptable considering this treatment technology, particularly the bacteria count and organic matter content were too high. This could have been caused by delayed installation of sewage treatment system in the cities located along the Drwęca River. Another important problem was the high content of iron and manganese, typical for this region.
In the water treatment process emphasis was placed on the supply of water clean in bacteriological terms by increasing the chlorine dose. The high content of organic substances in raw water and incomplete oxidation makes the treatment process and filtration inefficient, which in turn leads to a high concentration of pollutants in treated water. Additionally, organic matter hinders iron and manganese removal through peptisation. The presence of ammonia and chlorine in tap water indicates that dichloramine can be formed, increasing odour and unpleasant taste.
Modifications aimed at increasing the efficiency of coagulation did not fulfil their role due to the composition of organic matter. Humus compounds turned out to be invariable in biological and chemical terms. However, a significant, though insufficient, reduction in trihalomethanes, especially chloroform, was achieved.
In December 1994, pilot water treatment plant was opened. Since then many tests have been carried out to identify the optimum water treatment configuration. These tests lead to the treatment system currently implemented by the modernisation of the “Drwęca- Jedwabno” Water Treatment Plant which includes: application of ozonisation processes, change of the filtration process through the introduction of sand and anthracite beds in place of sand beds and activated carbon sorption, and disinfection with chlorine dioxide. As a result of these changes the taste, odour and other parameters of the water will improve. The plant's activity after modernisation will equal 66,000 m³/ day of extending it to 84,000 m³/day.