Use of specially prepared iron floc to oxidize and remove iron in water treatment processes

Claim 1

A process for treating water containing ferrous compounds comprising the following steps: (a) a first step of adding approximately 1 to 50 mg/l of alum to the untreated water; (b) a second step of aerating the water by intimate contact with air to remove dissolved gases and add oxygen to the water and to oxidize said ferrous compounds into iron oxides; (c) a further step of adding lime to the water to adjust the pH of the water to a value approximately from 7 to 9; (d) a further step of adding to the water recycled hydrous aluminum-iron floc sludge, collected in step (h) to produce a water to sludge ratio of about 2 to 30 percent by volume, said hydrous aluminum-iron floc sludge having an iron to aluminum ratio in the range of 15.7-57.3 by weight; (e) a further step of detention of the water for a time, after steps (a)-(d), and prior to the addition of chlorine in step (f) said detention time being effective in forming said hydrous aluminum-iron floc sludge including said iron oxides; (f) a further step of addition of chlorine to the water to produce a final concentration of at least about 0.5 mg/l; (g) a further step of separating the hydrous aluminum-iron floc sludge, formed in the prior steps, from the treated water; and (h) collecting the hydrous aluminum-iron floc sludge and recycling a part thereof for use in step (d).