Process for purifying water using fine floc and microfiltration in a single tank reactor

A method of purifying water to remove contaminants comprised of at least one of natural organic matter, color, turbidity, bacteria, cysts and oocysts, viruses and insoluble impurities on a continuous basis, the method comprising the steps of:

• (a) providing a body of water to be purified in a single tank reactor;
• (b) controlling the pH of said body in a range of 5 to 7;
• (c) adding a coagulant to said body to provide a floc;
• (d) providing a source of calcium in said body of water in a concentration in the range of 25 to 100 mg/l;
• (e) maintaining said floc in said body in a concentration in the range of 2 to 6 gm/l for purposes of adsorbing at least one of the contaminants to provide treated water;
• (f) removing a first portion of said treated water and said floc from said body of water to maintain said floc in said concentration;
• (g) providing a submerged semi-permeable membrane comprised of hollow fibers in said body of water in said single tank reactor;
• (h) removing a second portion of said treated water through a semi-permeable membrane having a pore size in the range of 0.01 to 1 .mu.m to provide a permeate comprised of purified water;
• and
• (I) bubbling air through said body of water to minimize membrane fouling and to provide mixing of said floc in said body of water to minimize settling of said floc all of the above steps occurring in the single tank reactor.

A method of purifying water to remove contaminants comprised of at least one of natural organic matter, color, turbidity, bacteria, cysts and oocysts, viruses and insoluble impurities on a continuous basis, the method comprising the steps of:

• (a) providing a body of water to be purified in a single tank reactor;
• (b) controlling the pH of said body in a range of 5 to 7;
• (c) adding a coagulant to said body to provide a floc in a concentration range of 3 to 5 gm/l having a size range of 0.5 to 5 .mu.m;
• (d) adding at least one of a source of calcium in the range of 25 to 100 mg/l, alumina particles and activated carbon in the amount of 5 to 20 gm/l to said body of water;
• (e) maintaining said floc in said body in a concentration in the range of 3 to 5 wt. %, for purposes of adsorbing at least one of natural organic matter, color and bacteria to provide treated water;
• (f) removing a first portion of said treated water and said floc from said body of water to maintain said floc in said concentration;
• (g) providing a submerged semi-permeable membrane comprised of hollow fibers in said body of water in said single tank reactor;
• (h) removing a second portion of said treated water through a semi-permeable membrane having a pore size in the range of 0.01 to 0.3 .mu.m to provide a permeate comprised of purified water;
• and
• (I) bubbling air through said body of water to minimize membrane fouling and to provide thorough mixing of said floc in said body of water to minimize settling of said floc, the above steps occurring in the single tank reactor.

A method for purifying water in a single tank reactor containing a body of impure water having submerged therein a semi-permeable membrane, said method adapted to remove contaminants comprised of at least one of natural organic matter, color, turbidity, bacteria, cysts and oocysts, viruses, arsenic compounds and insoluble impurities, the method comprising the steps of:

• (a) introducing impure water to provide a body of water in said single tank reactor;
• (b) adding a coagulant to said body to provide a floc therein in the range of 2 to 6 gm/l and having a size range of 0. 2 to 10 .mu.m for purposes of adsorbing contaminants thereon to provide treated water;
• (c) maintaining said body in a pH range of 5 to 8;
• (d) removing a portion of said treated water containing said floc from said body of water to maintain said floc in said range;
• (e) providing a submerged semi-permeable membrane in said body of water;
• (f) bubbling air past said membrane to improve flux through said membrane and to provide thorough stirring to minimize settling of floc in said tank;
• and
• (g) withdrawing water through said membrane on a continuous basis to provide a permeate comprised of purified water depleted in said contaminants, the above steps occurring in the single tank reactor.

A method for purifying water on a continuous basis in a single tank reactor containing a body of impure water having submerged therein a semi-permeable membrane, said method adapted to remove contaminants comprised of at least one of natural organic matter, color, turbidity, bacteria, cysts and oocysts, viruses, arsenic compounds and insoluble impurities, the method comprising the steps of:

• (a) introducing impure water on a continuous basis to provide a body of water in said single tank reactor;
• (b) adding a coagulant to said body to provide a floc therein in the range of 3 to 5 gm/l and in a size range of 0.5 to 5 .mu.m for purposes of removing contaminants to provide treated water;
• (c) introducing a source of calcium, activated carbon and alumina particles to said body of water in an amount sufficient to improve removal of said contaminants;
• (d) maintaining said body in a pH range of 5 to 7;
• (e) removing a portion of said treated water containing said floc from said body of water to maintain said floc in said range;
• (f) providing a submerged semi-permeable membrane comprised of a hollow fiber membrane in said body of water, the membrane having a pore diameter in the range of 0.01 to 1 .mu.m;
• (g) bubbling air past said membrane to improve flux through said membrane and to provide stirring to minimize settling of floc in said tank;
• and
• (h) withdrawing water through said membrane on a continuous basis to provide a permeate comprised of purified water depleted in said contaminants the above steps occurring in the single tank reactor.