Charge-neutralizing inorganic coagulants u2014 aluminum sulfate, ferric chloride, and polyferric sulfate u2014 for clarifying source water and wastewater and for chemical phosphorus removal.
Inorganic coagulants are metal-salt chemicals u2014 aluminum and iron(III) salts u2014nthat neutralize the negative surface charge on suspended colloids, so fine particles, color,nand phosphate collapse out of water and can be removed by settling or filtration.nIn water treatment they are the first chemical step in clarifying raw, process, and wastenstreams. Match the coagulant to source-water pH and to the contaminant you are targeting.
nnThe page carries three charged metal salts, with a real trade-off between cost and pHntolerance. Aluminum sulfate (alum) is the low-cost workhorse, but it works in a narrow bandnnear pH 5.5 to 7.5 and consumes alkalinity. Ferric chloride and polyferric sulfate stayneffective across a wider pH range, settle a denser floc, and strip phosphate well u2014 at higherncost and with more corrosive handling. Specify alum for routine clarification at controllednpH; specify the iron salts for cold water, color, phosphorus removal, or variable pH.
nnCoagulants act in seconds and need rapid mixing; flocculation and settling follow. Jar-testnthe dose u2014 typical alum doses run tens of milligrams per liter but shift with turbidity andntemperature u2014 because overdosing depresses pH and re-stabilizes the particles you meant tondrop. Where a permit drives low total phosphorus, the iron salts at a molar Fe:P ratio set bynthe target residual are the usual route.
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