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(1) General requirements for chemicals and materials used in water treatment: (1) Coagulants and coagulant aids used in the treatment of potable water must not have any harmful effects on human health as a result of the treated water quality. Water treatment agents used for industrial water treatment must not contain components that are harmful to production. (2) Water treatment agents for water purification should be subject to quality testing upon arrival at the plant and before use after being stored for a long time. (3) All chemical treatment agents and materials used in potable water must undergo health and safety evaluations, or the manufacturers of such agents must provide safety evaluation test reports issued by **authorized testing institutions. (4) Requirements for harmful substance indicators: ① When the harmful substances brought into drinking water by chemical treatment agents used in domestic drinking water are those specified in the \"Hygienic Standards for the Quality of Domestic Drinking Water\" (2001), the allowable limit for such substances is 10% of the corresponding specified limit. ②For harmful substances introduced into drinking water by chemical treatment agents used in domestic drinking water, where no specifications are provided in the \"Hygienic Standards for the Quality of Domestic Drinking Water\" (2001), relevant domestic and international standards can be referred to for determination; the allowable limit is 10% of that allowable concentration. (II) Common Water Treatment Chemicals and Materials Table of common water treatment chemicals and materials Name of raw material Testing items Quality standards and testing methods Aluminum sulfate Aluminum oxide, iron, insoluble matter in water, pH value, arsenic, heavy metals HG2227—91 Potassium aluminum sulfate Potassium aluminum sulfate, heavy metals, iron, arsenic, bound water HG/T2565—94 Crystalline aluminum chloride Crystalline aluminum chloride, iron, insoluble matter in water, pH value, arsenic, heavy metals ZBG77001—90 Anhydrous ferric chloride Ferric chloride, ferrous chloride, free acid, arsenic, insoluble matter, lead GB4482—93 Ferric chloride solution Ferric chloride, ferrous chloride, free acid, arsenic, lead, density, insoluble matter in water GB4483—93 Ferrous sulfate Ferrous sulfate, titanium dioxide, free acid, arsenic, lead, insoluble matter in water GB 10531—89 Polyaluminum chloride Insoluble matter in water, pH value, aluminum oxide, alkalinity GB 15892—1995 Polysulfate of iron Density, total iron content, amount of reducing substances, pH, basicity, arsenic, insoluble matter, lead GB 14591—93 Polyaluminum ferric chloride Aluminum oxide, basicity, iron oxide, insoluble matter in water Polyacrylamide Solid content, degree of ionization, solubility, molecular weight, free monomers Lime Calcium oxide, magnesium oxide, insoluble matter in water, iron oxide, aluminum oxide Sodium carbonate Total alkali content, chlorides, sulfates, iron, insoluble matter in water, amount of caustic ash GB210—89 Water glass Sodium oxide, silicon dioxide, relative density, number of layers, iron, insoluble matter in water GB4209—84 Sulfuric acid Sulfuric acid content, ash content, transparency, color, iron, arsenic, lead GB 534—89 Liquid chlorine Chlorine content, moisture content GB 5138—85 Wood-based activated carbon Iodine adsorption value, methylene blue decolorization capacity, strength, particle size, packing density GB/T 13804.2—1999 Coal-based activated carbon Iodine adsorption value, methylene blue decolorization capacity, strength, particle size, packing density GB/T 7701.4—1997 Quartz sand filter media and support materials Crushing rate and wear rate, silt content, density, loss on ignition, particle size, salt-solubility rate GJ24•1—88 Bituminous coal (anthracite) Crushing rate and wear rate, density, silt content, particle size, salt-solubility rate GJ24•2—88 Magnetite filter media Silt content, density, particle size GJ24•3—88 Natural manganese sand filter media and manganese ore support materials Manganese content, density, salt-solubility rate, crushing rate and wear rate, silt content, particle size CJ/T3041—1995 II. Inorganic salt polymers (I) Polyaluminum chloride Polyaluminum chloride is also known as basic aluminum chloride. Its molecular formula is m, where n is any integer between 1 and 5, and m is an integer ≤10. This formula represents a polymer composed of m Al2(OH)nCl6-n monomers (referred to as hydroxyaluminate chlorides). Therefore, polyaluminum chloride is actually an inorganic polymer. The ratio of OH- to Al3+ in the molecular formula has a significant impact on the coagulation effect; this is generally expressed as the basicity (alkalinity) B. For example, when n=4, it is usually required that liquid polyaluminum chloride contain more than 10% Al2O3, a basicity B of 50% to 85%, and more than 0.5% insoluble matter. Polyaluminum chloride exhibits good coagulation effects on water with high or low turbidity, high color intensity, and low temperatures. It forms flocs (also known as alum flowers) rapidly; these flocs are large and heavy, making them easy to settle. The amount required for its use is less than that of aluminum sulfate. It operates within a wide pH range, from 5 to 9. Moreover, it is possible to produce the most suitable polyaluminum chloride depending on the quality of the water to be treated, whereas this is not possible with aluminum sulfate. Its amount added should not be excessive, otherwise it will also make the water cloudy. The coagulation mechanism of polyaluminum chloride is similar to that of aluminum sulfate; that is, regardless of the form in which the aluminum salts are added, they do not exist in water as pure Al3+ ions, but mainly as compounds of trivalent aluminum – hydrated aluminum complex ions, Al(H2O)63+. When pH