Wastewater treatment, aluminum sulfate

The pulp and paper industry and potable and wastewater treatment industry are the principal markets for aluminum sulfate. Over half of the U.S. aluminum sulfate produced is employed by the pulp and paper industry. About 37% is used to precipitate and fix rosin size on paper fibers, set dyes, and control slurry pH. Another 16% is utilized to clarify process waters. The alum sold for these purposes is usually Hquid alum. It is frequendy acidic as a result of a slight excess of H2SO4. Aluminum sulfate consumption by the pulp and paper industry is projected to remain constant or decline slightly in the near term because of more efficient use of the alum and an increased use of alkaline sizing processes (13). 

Aluminum sulfate octadecahydrate [7784-31 -8]y Al2(S0 2 I8H2O, and its aqueous solutions are used primarily in the paper (qv) industry for sizing and as a flocculating agent in water (qv) and wastewater treatment. This material is often called papermakers alum or alum. Because this salt is precipitated from aqueous solution, aluminum sulfate hydrate [17927-65-0] Al2(SO 7/H2O, can have variable composition and is sometimes referred to as cake alum or patent alum. The solid commercial hydrate, generally written as the 18-hydrate, is typically dehydrated to correspond to from 17.0 —17.5% Al O where n = 13 14 (1,2). This dehydrated form is called dry alum, ground or lump. Aluminum sulfate solutions are typically 7.5—8.5% Al O and are known as liquid alum. 

Poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride] coagulant, wastewater Polyaluminum chloride coagulant, wastewater treatment Acrylates/acrylamide copolymer Polyaluminum hydroxide chloride sulfate Poly (2-hydroxypropyl-N,N-dimethyl ammonium chloride) Polyquaternium-6 coagulant, water clarification Polyquaternium-6 coagulant, water purification Ammonium alum Ferric sulfate coagulant, water purification plants Aluminum sulfate coagulant, water treatment Acrylates/acrylamide copolymer Aluminum chloride anhydrous Bentonite Calcium hydroxide Calcium monocarbonate Calcium oxide Cetrimonium chloride Diethylaminoethyl acrylate dimethyl sulfate quat. Dimethylamine/epichlorohydrin copolymer Dimethylaminoethyl acrylate dimethyl sulfate... 

The water is brought in from a lake, stream, or reservoir and initially filtered to remove sticks, leaves, dead fish, and such. The turbidity (haziness) that s commonly present in river or lake water is removed through treatment with a mixture of alum (aluminum sulfate) and lime (calcium hydroxide), which forms gelatinous aluminum hydroxide and traps the suspended solids. This is basically the same treatment used in wastewater treatment plants (see Primary sewage treatment . ... 

Qiu, Z.M. Jiang, W.T. 2009. Post-treatment of banknote printing wastewater using polysilicate ferro-aluminum sulfate (PSFA). Journal of Hazardous Materials 166 740-745. 

Induced flocculation is important industrially in the purification of drinking water and for wastewater treatment. Suspended particles in water are often too tiny to be filtered out of the water directly, so to solve this problem flocculation agents can be added to the water. Flocculation agents often contain multivalent charged ions (alum, ferric sulfate, or aluminum chlorohydrate, for example) or charged polymers, and they induce aggregation of suspended particles into floes by electrostatic screening. 

Some innovating treatment technologies may be introduced in the treatment of wastewater generated in the aluminum fluoride industry to make its effluent safer. The ion exchange process can be applied to the clarified solution to remove copper and chromium. At a very low concentration, these two pollutants can be removed by xanthate precipitation.24 A combination of lime and ferric sulfate coagulation will effectively reduce arsenic concentration in the wastewater. 

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