Water Treatment > Quality Water Solutions > Operational Issues > Storage and Handling

Dry alum can be fed by gravity, mechanical or pneumatic systems. Silos, which should have a minimum capacity of 40 to 100 tons, can be made of unlined steel, concrete, fiberglass/epoxy or polyester. The silo and handling system should be weather tight and totally enclosed. It should have a dust collector with a positive blowback cleaning cycle large enough to include blowdown from pneumatic unloading systems for tanks trucks and hopper cars. It should have a 60° sloped bottom hopper equipped with a positive shut-off slide gate valve, an emergency rodding connection and clips for installation of a vibrator.

Liquid Alum. Liquid alum is best fed by gravity flow, although centrifugal pumps can be used. Storage tank pressurization is not recommended for transfer. Tanks should be installed indoors or, if outdoor, heated to maintain a temperature of 45 to 60 °F, because liquid alum can crystallize near 30 °F and freeze at about 5 °F. Lines exposed to low temperatures should be insulated. Piping should have flush-out connections at various points, esp., near pumps and metering equipment, for use if crystallization occurs.

Tanks should have a minimum capacity of 7,500 to 15,000 gallons. Materials of construction can include fiberglass/epoxy, polyester, rubber-lined steel and Type 316 stainless steel. Schedule 80 PVC piping with socket connection is recommended, provided it is adequately supported and alum temperatures do not rise above 120 °F. If temperature can go above this, Schedule 80 CPRC and Type 316 stainless steel are recommended.

Polyaluminum hydroxychloride. (PACl) can be fed by gravity or centrifugal or metering pumps. Pressurizing a storage tank for transfer is not recommended. Tanks should be maintained at 45 °F or more. Flush-out points should be included at strategic points in the piping to purge crystals. Storage tanks should be fabricated of suitably constructed fiberglass reinforced polyester or high-density polyethylene materials. For greater strength, rubber-lined steel and PVC bag liners in steel or wood-stove tanks can be used. For transfer, centrifugal pumps with wetted parts of Hastelloy-C276 or a suitable plastic are recommended.