Švařec water treatment plant
The construction of the Vír Regional Water Supply System (VOV) commenced in 1988. This water-related structure includes the Švařec water treatment plant. The investor and the owner of the system is Vírský oblastní vodovod, sdružení měst, obcí a svazků obcí. The whole water system including the Švařec water treatment plant is operated by Brněnské vodárny a kanalizace, a.s.
Reasons for deciding on commencing the construction work
As a result of a low subsidised price, the water consumption in Brno rose to 65 mil. m3 a year in 1989 compared to 43 mil. m3 a year in 1968. The capacity of water resources did not suffice to cover the peak demands, water supply was disconnected and it was necessary to introduce regulatory measures limiting water consumption.
The water resources were overloaded, above all the Pisárky plant, which had an adverse impact on the quality of treated drinking water, which was rightfully criticised by the consumers. The quality of raw water in the Svratka used in the water treatment plant was also deteriorating and was susceptible to a high risk of being contaminated by oil products and other substances from adjacent roads with heavy traffic etc.
Need of supplying water to the municipalities in the district of Brno-venkov suffering from a lack of water and poor quality water in local resources. This mainly concerned the area south of Brno – Želešice, Rajhrad, area of „bitter water“ (Žatčany, Moutnice, Nesvačilka, Sokolnice, Těšany etc.) and the areas of Tišnov, Rosice, Ivančice and Židlochovice.
Water treatment technology
The water treatment plant was designed to a maximum performance of 2,300 l/s. In the course of the construction work, the planned performance was temporarily reduced by a decreased capacity of filtration to 1, 150 l/s as a result of a declining water demand trend. The water consumption, which is presently nearly as low as half the 1989 consumption, has dropped as a result of progressive rise in the water and wastewater tariffs after cancelling subsidies for production and distribution of drinking water and collection and treatment of wastewater. The social and economic changes after the year 1989 also contributed to the reduced water consumption.
Water flows from the abstraction plant constructed in the dam of the reservoir Vír I. Water can be abstracted from three different height horizons according to the currently best quality of raw water in the Vír reservoir. These abstraction points are situated 18, 36 and 51 meters above the bottom. Three stainless steel pipes are led from the abstraction points to analysers measuring O2, pH, turbulence and temperature. The values measured by the analysers are transferred to the control room at the water treatment plant. The abstracted water flows through a Francis turbine into a tank downstream the reservoir. The abstraction pipe HOBAS DN 1 600, length of 590 m, leads from the bottom of the separate part of the stilling basin to the inlet of the raw water tunnel. The raw water tunnel is 4, 190 m long, with an internal diameter of 2,100 mm. The armoured outlet of the tunnel is connected to a feeding pipe HOBAS DN 1 400 discharging into the inlet structure of the Švařec water treatment plant.
A Francis turbine with a throughput of 210 kW is installed at the raw water inlet to the water treatment plant. Chlorine dioxide or ozone is dosed to the overflow in the inlet structure (in the ionisation plant) is an oxidising agent, aluminium sulphate, or potassium permanganate is dosed to remove manganese from raw water. When using pre-ozonisation, the coagulant is does downstream this unit. The technological process also includes slow mixing and contact filtration through sand filters. Out of twenty installed filters, a total of ten filtration units are equipped and in use. These are classic high-speed filters with intermediate bottoms arranged in pairs with a ground plan of 100 m2. Water is drained from the filters by a common discharge channel to:
Storage tanks. In this case, limewater is dosed to the overflow to adjust pH.
Disinfecting ozonisation. If the disinfecting ozonisation is used, the limewater is dosed to the overflow downstream the cooling tank. The disinfecting agent, chlorine dioxide, or chlorine as a back-up, is dosed to the overflow to the storage tanks. The storage tanks are located on the lowest floor of the filtration building, their capacity is 20,000 m3 and they are designed so that water flows along all the profile from the inlet to the abstraction point.
Water is taken from the storage tank using a pipe DN 1 600:
By gravity to the Švařec - Čebín conduit
By pumping via three systems into:
o The water network of the water treatment plant
o Production and dosing of lime and chlorine dioxide
o Network supplying water to the municipalities of Švařec, Koroužné, Štěpánov nad Svratkou
Sludge management is used to dispose of water management sludge. It consists of sedimentation and homogenisation tanks and filter presses. Drinking water from the water treatment plant flows in a pressure tunnel, length of approx. 15.8 km and a pipe conduit of a profile of 1,400 mm to the Čebín water reservoir, where it is mixed with groundwater from the 2nd Březová conduit and is distributed to the service area to the consumers. The technological process in the water treatment plant, the transport of water from the Vír lake all the way to the final consumers is by gravity in all the Vír Regional Water Supply System.
Water quality in the Švařec water treatment plant
The Vír impounding reservoir is the source of surface water. The quality of raw water has been verified by 25-year operation of the existing water treatment plant supplying water to the municipalities in the district of Žďár. The impounding reservoir is a zone of sanitary protection and bathing and fishing are forbidden. Raw water is little mineralised and soft, with a relatively low content of organic substances of natural origins. Toxic sewer metals and organic matters are not detected in concentrations important in hygienic terms.
Compared to the Pisárky water treatment plant, replaced by this new WTP, the risk of raw water contamination by oil products and other industrial accidents is significantly reduced.
The Švařec water treatment plant can produce quality drinking water fully complying with all criteria set for drinking water. The quality of water is constantly checked by the drinking water laboratory.