ANSI AWWA B404-14 pdf free download – Liquid Sodium Silicate
In the United States, authority to regulate products for use in, or in contact with, drinking water rests with individual states.* Local agencies may choose to impose requirements more stringent than those required by the state. To evaluate the health effects of products and drinking water additives from such products, state and local agencies may use various references, including a standard developed under the direc- tion of NSF, NSF+/ANSI# 60, Drinking Water Treatment Chemicals– Health Efects. Various certification organizations may be involved in certifying products in accor- dance with NSF/ANSI 60. Individual states or local agencies have authority to accept or accredit certification organizations within their jurisdiction. Accreditation of certi- fication organizations may vary from jurisdiction to jurisdiction. Annex A,“Toxicology Review and Evaluation Procedures,” to NSF/ANSI 60 does not stipulate a maximum allowable level (MAL) of a contaminant for substances not regulated by a USEPA final maximum contaminant level (MCL). The MALs of an unspecified list of“unregulated contaminants” are based on toxicity testing guidelines (noncarcinogens) and risk characterization methodology (carcinogens). Use of Annex A procedures may not always be identical, depending on the crtifer. ANSI/AW WA B404 addresses additives requirements in Sec. 4.3.2 of the standard. ‘The transfer of contaminants from chemicals to processed water or to residual solids is becoming a problem of great concern. The language in Sec. 4.3.2 is a recommenda- tion, only, for direct additives used in the treatment of potable water to be certified by an accredited certifcation organization in accordance with NSF/ANSI 60, Drinking Water Treatment Chemicals-Health ffects.
II.A. Discission. Liquid sodium silicate is generally shipped in metal drums, tank trucks, or railroad tank cars. Most grades are fuid enough at room temperature and above to be purged easily. These liquids should be stored in closed, vented tanks. Storage tanks should have provisions for keeping the silicate from freezing. Sodium silicates are normally added to water by means of a chemical feed pump. Diaphragm, peristaltic, progressive cavity, gear, and piston pumps are satisfactory, but piston or gear pumps should have lantern-ring water glands around the pistons. For some uses, such as very low concentrations for boiler feed, hot water with elevated magnesium, and some industrial uses to minimize scale formation, the silicate solu- tions can be diluted with freshwater before use; this is especially advisable if the silicate is fed into a brine. Silica is found to some extent in all natural waters and is believed to be ecologically harmless. The addition of sodium silicate tends to slightly increase the pH and alkalin- ity of water and may increase turbidity in concentrations above 50 mg/L. II.B. Safety. Sodium silicate solutions are moderately to strongly alkaline. They are not explosive or fAammable, and corrosion- control silica products are not classified as hazardous. Some of the other more alkaline solutions are considered hazardous in US Department of Transportation (DOT) shipping regulations for sodium silicate. The principal danger of silicate solutions involves contact with the eyes. Protective goggles and/or face shields should be worn when handling these products. If silicate is splashed into the eyes, Aush immediately for 15 minutes and seek medical attention. If splashed on the skin, sodium silicate solution should be washed off quickly with water- preferably warm water. If allowed to remain in contact with the skin, irritation may result. Dried deposis of the liquid should be treated with care, because they can cause skin cuts similar to those infAicted by broken glass.