Upgrade of the Želivka water treatment plant
Czech-republic
Úpravna vody Želivka a.s.
Surveys, Basic design (for the location permit), Enabling and administrative services Detailed Design (for construction permit), Tender Documents for Works, Design Conformity Supervision, Emergency plans, Contractor’s Design Documentation, As-built Documentation including 3D model, Operation manuals, Consulting and assistance in testing
The Želivka water treatment plant, with a capacity of 7.7 m3/s of treated water, is the largest water treatment plant in central Europe. It serves as drinking water source for 1.3 million inhabitants living in the Czech Republic capital Prague, and in parts of the Central Bohemian and Vysočina regions.
The Švihov water reservoir covers an area of 1602 hectares and has a total volume of 309 million m3 that provides raw water for the treatment process.
Seasonal changes affect certain parameters of raw water
Presently, the existing treatment process meets the requirements for drinking water quality. However, fluctuations in quality of raw water occur during certain seasons, which might have a negative impact on the quality of produced drinking water in the future.
The original studies have found that the gradual deterioration of certain parameters of raw water occurred during the change from winter to spring, and at the end of the summer season with resulting extreme conditions of microbiological pollution.
In addition, water quality was affected by periods of increased concentrations of specific organic substances in raw water, mainly pesticides and their metabolites. The original process line of the Želivka water treatment plant was not designed to remove such pollution. The dosing of ozone, which was added in the 90s, can only partially cope with increased specific organic substances and microbiological pollution.
Major upgrade of the water treatment plant with new design and construction
By assessing the current and future needs, a decision was taken to design and construct a major upgrade of the Želivka water treatment plant with an extension of the process line and a new treatment step – GAC filtration (Granual Active Carbon).
Providing higher security of operation of the water treatment plan as well as to secure the quality of the water produced and the ability to produce drinking water in crisis situations were key aims of the project.
After the upgrade the Želivka water treatment plant can reliably ensure the removal of specific organic substances (such as xenobiotics, pesticides, and pharmaceuticals) and their products, which are either contained in the raw water or are formed during the water treatment process during ozonation.
Additional benefits include the ability to minimise the risks of non-compliance with the relevant legislative limits for pesticides and their metabolites in the produced drinking water and to improve the parameters of the produced drinking water in the period of the spring when there are significant increased numbers of microorganisms in the Švihov water reservoir.
New GAC filtration hall
Sweco experts worked together with the client on the project for the new GAC filtration hall, its design and construction. There are 16 filtration units arranged in four sections, or basins. Each basin has a total filter area of a 400 m2 with a filtration layer that is 1.70 m deep. The total area of all filters is 1604 m2. The entire GAC filtration facility is designed for flow rates from 1.1 to 3.5 m3/s.
The filtration bed is formed by a stainless-steel drainage system, with each of the four filter basins covered with a polycarbonate segment roof and equipped with a ventilation system in order to mitigate the risk of residual ozone leakage and to reduce moisture in the GAC filtration hall area.
