water protects the lake against acid rains. Due to the prevalence of western winds, the reed belt is continuous and lush on the sheltered western shore and broken at the open eastern one. The narrow southern end, especially beginning from Pähksaar Island is totally overgrown with yellow and white lilies, pondweeds, arrowhead, bulrush, and other water plants. The amount of planktonic algae can reach 30g per cubic metre, with blue- green algae prevailing in summer. Water is turbid, yellowish-green or greenish yellow, with a transparency of about 1m. Mud particles stirred up by the wave action contribute to turbidity. The zooplankton of the lake consists of smaller animals building up the summer biomass. The amount of bottom animals is low but variable in different years. pic: plaktonic algae About 35 fish species are in Lake Võrtsjärv. Pike-perch, eel, bream and
consumed. Rapid sand filtration First, to quickly remove the impurities from the raw water, a coagulant is added, forming the impurities into large clumps that settle to the bottom. After this process, the water passes through a coarse sand layer in a filter bed, which cleanly removes the impurities. This method is effective even when the raw water is relatively turbid, and can be used to treat large amounts of water using only a small area of land. Slow sand filtration First, the flow of raw water is slowed considerably to allow impurities to settle naturally. The water then passes through a relatively fine sand layer in a filter bed to filter it. However, the water is actually purified through the decomposition action of microorganisms that exist on the surface of the sand layer.
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