Water intake at the treatment plant can come from a number of different sources. Surface waters come from rivers, lakes and reservoirs, which may have a wide range of chemistries with high mineral and metal contents, chloride levels and particulates. Ground waters taken from underground springs, water tables and wells are low in oxygen or fully de-aerated with varying amounts of hydrogen sulphides and sulphate reducing bacteria.
The incoming water streams are usually screened and then treated with oxidising chemicals such as chlorine and potassium permanganate, to precipitate iron and manganese. Filters remove these precipitates, floc and particulate matter. Inside the treatment plant, additional chemical treatments using ferrous sulphate, alum, caustic soda and other reagents assist in neutralising water streams and the precipitation of metallic ions and particulate matter.
The treated waters will often undergo a final filtration process, using stone/gravel filter beds or activated carbon, followed by a final disinfection by an oxidant such as chlorine before distribution as drinking waters.
Table 6 provides a list of applications where stainless steels have been successfully used within water treatment plants.
Table 6. Typical Water Treatment Applications
|Well linings and filters
|Well head components
||Ozone generators and piping
||Railings and platforms
||Pumps and Valves
||Tanks and ladders
||Electrical fitting covers
||Granulated activated carbon towers
|Sampling and sensor lines
||Central control gravity filters
|Chemical treatment lines
References and Links
Applications for Stainless Steel in the Water Industry, IGN 4-25-02, WRc. UK (1999)
Operational Guidelines and Code of Practice for Stainless Steel Products in Drinking Water Supply, British Stainless Steel Association (2002)
Stainless Steel for Potable Water Treatment Plants, NI Publication 10087
SCI P245 – Steel Package Water and Waste Water Treatment Units (2000)
Stainless Steels and Drinking Waters around the World (C.P.Cutler EuroInox Publication)
Raising Drinking Water Guidelines - The World Health Organization has increased the permitted concentration of nickel in drinking water (Nickel Magazine, Mar. 2006)
Italy's Underground Water Plant
The Italian tourist town of Como has built an underground drinking water plant that uses nickel stainless steel, ensuring corrosion-resistance and low maintenance. (Nickel Magazine, Feb. 2003)
Water Tank Built to Last 60 Years, NI Publication 14030
The city of Matsuyama on the Japanese island of Shiboku has built the country's first stainless steel municipal water tank in order to ensure its residents a safe, steady supply of drinking water well into the 21st Century. This article tells why they chose stainless steel.