Only Stainless Will Do
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Corrosion-resistant nickel stainless steels help improve the service life of waste
water treatment plants. By Steve Dawson
Nickel magazine, February 2003 -- Health concerns have made the treatment of
potable water and waste water a primary environmental issue worldwide. As a result, many municipalities and
local industries have turned to environmental technology companies to develop products to improve water
quality.
One such company is Florida, U.S.A.-based Parkson Corporation, which provides a range of clean-water services and manufactures complete treatment systems and individual components. Many of the components are manufactured entirely from nickel-containing stainless steel.
One of the more innovative products manufactured by Parkson is the Z Complete SuperScraper system. The SuperScraper line of products was developed in 1973 by Waterlink, now a division of Parkson Corporation, and includes bottom scrapers, surface scrapers, sludge removers, scum pipes and various accessories. These products, manufactured entirely from S30400 or S31600 stainless steel, have long service lives and, according to Parkson, many of the early installations are still in use today.
The Z Complete SuperScraper system is used in the primary sedimentation process, within rectangular sedimentation tanks measuring up to 80 by 11 metres. The primary sedimentation tanks are used in drinking water purification plants and in plants that treat municipal and industrial waste water. The system includes a bottom scraper, a surface scraper and a rotating scum pipe.
The bottom scraper is designed for the continuous movement of sediment that collects at the bottom of a tank. Typically this sediment contains 0.5% to 8.0% solids. Concave stainless steel sections are welded together to form a single unit that moves along the bottom of the tank on high-density polyethylene slides. The scraper slides gently forward by means of a system of levers attached to a hydraulic cylinder. During forward motion, the sediment is moved toward the sludge pit for removal. The unit then recedes at about three times the speed of the forward rate. Since the sections are inclined, they slide under the sediment without disturbing the sedimentation process. These steps are then repeated, resulting in a constant flow of sediment to the sludge pit.
Nickel-containing stainless steel is used because of its strength and reliability, as well as its resistance to corrosion and wear, all of which reduce maintenance costs by ensuring that the components last a long time.
While the Z 2000 is used to remove sediments, the surface scum in a primary sedimentation tank is removed with the surface scraper. This is generally used in conjunction with a rotating scum pipe. The blade of the surface scraper placed in the water moves along the tank surface, drawing foreign material toward the rotating scum pipe. The pipe is automatically angled downward as the blade nears and material is then skimmed into the pipe without any accompanying water. The surface blade features a unique switching link, which rotates the blade out of the water as it returns to the back of the tank, thereby preventing material from being drawn back along surface. This is an important benefit for many industrial and municipal applications where the conservation of water is a concern.
First installed in Europe in the 1970s, Parkson is attracting attention from North American customers.
Already, the company has installed many Z Complete SuperScraper systems in the U.S.
Steve Dawson is a Toronto-based freelance science writer.
Photo: PARKSON CORP.
 Parkson Corporation 2727 NW 62nd Street P.O. Box 408399 Fort Lauderdale, Florida U.S.A. 33340-8399 Tel: 1-954-974-6610 Fax: 1-954-974-6182 E-mail: Website: www.parkson.com |
