Raw water is natural water found in our environment, like rainwater, ground water, and water from lakes, rivers and sea. Almost all raw water requires treatment before the water can be further treated in most pure water treatment systems. The type and extent of a pretreatment system will depend on the type of source (i.e. well water, open sea, surface water). The major difference is not only the feed water composition, but also water quality variability by seasonal factors, climate conditions and/or activates on the surface waters. The pretreatment system can include various types of pretreatment equipment to remove suspended solids, dissolved solid and other contamination harmful to the pure water treatment system.
The primary objective of pretreatment of raw water is to make the feed water compatible with the pure water treatment systems. Membrane systems of differing types (microfiltration, ultrafiltration, nanofiltration, reverse osmosis (RO)) require pretreatment to increase the efficiency and life expectancy of the membrane elements by minimizing fouling scaling and degradation of the membrane.
The pretreatment systems can be chemical, mechanical or a combination. The Bernoulli Filter is an excellent mechanical filter to reduce the load of suspended solids in raw water down to 100 micron.
Case story: Eren Enerji
Since 2010, the company ZETES (Zonguldak Eren Termik Santrali) owned by EREN (Eren Enerji Elektrik Üretim A.S.) has operated a coal-fired power plant including one unit of 160 MW (ZETES-1) and two units of 615 MW (ZETES-2) in Catalagzi, Turkey.
The sea water treatment plant at ZETES has been built by Aquamatch Türkiye on turnkey bases. This is one of the biggest desalination and demineralization plant in Turkey and consists of Ultrafiltration, Sea Water Reverse Osmosis, Brackish Water Reverse Osmosis and Mixbed Demineralization systems.
Sea water from the Black Sea is pumped to a storage tank and then feed to a pre-filtration system. The sea water passes through 1 mm coarse mechanical filter before entering three Bernoulli Filters, BSG 350 with 200 micron filter baskets. In this way the Ultrafiltration (UF) system is protected from coarse and fine particles. Filtered sea water is then chlorinated for oxidation of iron and magnesium content and disinfection of microorganisms and transferred to a raw water tank.
Treated sea water is then pumped to the UF-system consisting of six parallel trains with a total capacity of 1590 m3/h. The UF-system is an advanced pretreatment system before desalination system in order to filter suspended solids down to 0,02 microns and to reduce the turbidity and SDI (Silt Density Index) to desired values. The sea water is purified by physical contamination by the UF-system before entering the sea water reverse osmosis (SWRO) system for desalination. The total capacity of SWRO is 880 m3/h. Low conductivity process water of 700 m3/h will be supplied after a second pass RO-system. 500 of the 700 m3/h process water is used for soft process water and the rest, 200 m3/h is passed through a degasifier to remove dissolved CO2 before entering a mixed-bed demineralization unit to provide pure water for steam boilers.
Facts and figures
Customer: Eren Enerji Elektrik Üretim A.S
Location: Catalagzi, Turkey.
Application: Prefilter UF-system
Filter model: 3 x BSG 350
Filtration: 0,2 mm
Operating flow: 3 x 1100 m3/h
Design pressure: 10 bar
Operating pressure: 2 bar