Drinking water preparation unit at South Water Supply Station of St. Petersburg
A new modern two-stage water treatment unit was commissioned at the South Water Supply Station in 2011, with the throughput of 350,000 m3/day, which is 20% of the total daily supply. The technical solutions applied at the unit: two stages of water treatment (preliminary ozonation; filters with sand/activated charcoal two-layer load); washout water treatment structures and sludge treatment structures.
The two-stage water treatment process ensures safe, harmless, and favorable drinking water, regardless of the quality of the initial water in the source. This is especially relevant for populated areas with a surface water supply source.
Components installed in the solution
The unit is installed as a new construction on the territory of the existing South Water Supply Station of natural water treatment coming from the Neva River. The unit consists of three buildings: a building of principal surface water treatment, a building of water supply sludge treatment and chemicals section, a building of water supply sludge dewatering.
The operational flexibility of the unit is ensured with a number of factors, including four interrelated treatment lines that can operate both jointly and individually.
The treatment process includes the following technologies:
- Preliminary ozonation of natural water,
- Reagent water treatment with coagulants and flocculants,
- Clarification by settlement in a settling tank with a shelf module, sludge thickening, possible sludge recirculation and its removal.
- Filtration through rapid gravity filters with two-layer load – sand/activated granulated charcoal equipped with a thorough bottom drainage system and a laser protective screen, and water-air filter backwash system.
- Decontamination with chloramines.
A system for spent washout water reclamantion and sludge dewatering on centrifuges is provided.
Basic process solutions and startup and adjustment works were performed by specialists of the Water Service Company of Belgrade (Serbia). An international consortium of specialists headed by Tahal company (Israel) worked on the project.
The new unit provides for an automatic control system that ensures efficiency and safety of the process, with continuous water quality monitoring by treatment stages allowing any changes in raw water quality to be coped with. The equipment applied in the project guarantees high level of efficiency and low operational expenses. The new water treatment unit implements the policies of resource saving. For instance, natural water ozonation can be stopped depending on the initial quality characteristics of the treated water.
The new unit solves all relevant modern ecological problems due to using ecologically clean processes and ensuring the minimum quantity of waste with its maximum disposal.
Social effect of implementation
Ensuring supplying consumers with drinking water of the guaranteed volume and quality regardless of the water quality in the Neva.
Economic (financial) result of implementation
Process solutions implemented in the project allow:
- ensuring consistent quality of drinking water at the exit from the water treatment station;
- reducing the volume of water taken from the source by 30%;
- excluding fully the dumping of washout water as a result of using structures for the turnover of washout water and sludge thickening and dewatering.