Water stand posts: operation experience and advanced technical solutions

Summary

At present about 2.5 thousand water stand posts (mainly KV-4) are operating in the water distribution network of SUE «Vodokanal of St. Petersburg». Their maintenance is complicated by freezing in winter and uncontrolled water consumption. To improve the reliability of water stand posts Okkervil model was designed. A ball valve is used as a shutoff valve. Substituting steel pipe with a plastic one provided for the substantial reduction of the risk of water freezing over the inner surface of the feeding pipe. Improving the design provided for eliminating ejector moveability. The new design lacks sealing rubber rings; the stand post lever force at turning on is reduced. The new fixed ejector has a double seal at the connection to the stand post body. Okkervil water stand posts were tested during two years in the water distribution network of the Primorsk district of St. Petersburg, and starting from December 2012 they have been successfully operating in five cities of the North-Western region of Russia. The advance design of stand posts provides for the reliable operation of municipal and community water networks supplying the residents of houses that lack service pipes.

Key words

water supply network , stop valves , water stand post , ejector , ball valve

Process concentrate treatment by flotation at CHP plants

Summary

The problem of processing oily wastewater generated at power plants is discussed. Much attention is paid to the purification of process concentrate that is characterized by higher temperature (55–70 °С). A pneumatic flotation unit used for the process concentrate treatment at the South CHP plant operated by Lenenergo OJSC is considered. The major drawback of the unit is pointed out: the changes in the rubber properties result in the changes in air bubble dimensions, and the efficiency decreases. A possible solution to the problem can be the use of an ejection aeration system with a disperser. The experiments in a laboratory unit on determining the size distribution of the bubbles generated by the ejection aeration system at 55°С were conducted. In addition, model oily wastewater was subject to purification in a unit with the pneumatic and ejection aeration systems. The average size of the finely dispersed bubbles generated by the ejection aeration system with a disperser was 60 μm, and that of the coarse bubbles was 105 μm. It is shown that the use of the ejection aeration system with a disperser provides for reducing the residual concentration of oil products from 4 to 1 mg/l or reducing the purification time from 25 to 15 minutes.

Key words

flotation , ejector , pneumatic aeration system , air bubble size , dispersant , process condensate

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