Method for treating water by ballasted flocculation and decantation
First Claim
1. A ballasted flocculation process for purifying water comprising:
- a. mixing a coagulant with the water;
b. selecting a ballast in the form of insoluble granular material where the insoluble granular material has an effective diameter between approximately 40 and 300 micrometers;
c. mixing the selected ballast with the water and mixing a flocculant with the water to form flocs and microflocs around the ballast;
d. introducing the mixture of water and flocs into a decantation zone;
e. in the decantation zone, separating purified water from a mix of sludge and ballast;
f. directing the mix of sludge and ballast from the decantation zone to a separator that is operative to separate the sludge and ballast;
g. separating the ballast from the mix of sludge and ballast and recycling the separated ballast to or upstream mixing step c. wherein the separated ballast recycled constitutes 20% or more by volume of the mix of sludge and ballast directed to the separator;
h. separating sludge from the mix of sludge;
i. concentrating the separated sludge, recycling at least a part of the sludge to or upstream mixing step c., and wasting a portion of the sludge wherein the concentration of the sludge wasted is at least 5 g/L; and
j. directing at least some of the mix of sludge and ballast from the decantation zone to an intermediary mixing zone;
directing at least some of the sludge separated by the separator to the intermediary zone and mixing the mix of sludge and ballast with at least a part of the separated sludge;
directing the mixture of the mix of sludge and ballast and the separated sludge from the intermediary mixing zone to the separator and continuing to return separated sludge from the separator to the intermediary mixing zone.
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Accused Products
Abstract
The invention concerns a water treatment method which consists in introducing coagulated water in a flocculation zone, to enable flocculation of microflocs in the presence and around a ballast; introducing the mixture in a decantation zone; separating the treated water in overflow and a mixture of sludge and the ballast in underflow; conveying at least part of said mixture to a sludge/ballast separating system and recycling into or upstream of the flocculation zone the ballast and part of the sludge introduced in said separation system. The invention is characterized in that it comprises steps which consists in conveying the mixture to the sludge/ballast separating system; in subjecting said mixture to a ballast concentration, extracting the ballast from the sludge extracted from the separation system; and more than 20% of the volume entering the sludge/ballast separating system is recycled into or upstream of the flocculation zone, after passing through at least part of the sludge/ballast separation system; and the ballast has an effective diameter greater than 60 micrometers, and the sludge extracted from the treatment system has a concentration higher than 5 g/L.
50 Citations
11 Claims
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1. A ballasted flocculation process for purifying water comprising:
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a. mixing a coagulant with the water; b. selecting a ballast in the form of insoluble granular material where the insoluble granular material has an effective diameter between approximately 40 and 300 micrometers; c. mixing the selected ballast with the water and mixing a flocculant with the water to form flocs and microflocs around the ballast; d. introducing the mixture of water and flocs into a decantation zone; e. in the decantation zone, separating purified water from a mix of sludge and ballast; f. directing the mix of sludge and ballast from the decantation zone to a separator that is operative to separate the sludge and ballast; g. separating the ballast from the mix of sludge and ballast and recycling the separated ballast to or upstream mixing step c. wherein the separated ballast recycled constitutes 20% or more by volume of the mix of sludge and ballast directed to the separator; h. separating sludge from the mix of sludge; i. concentrating the separated sludge, recycling at least a part of the sludge to or upstream mixing step c., and wasting a portion of the sludge wherein the concentration of the sludge wasted is at least 5 g/L; and j. directing at least some of the mix of sludge and ballast from the decantation zone to an intermediary mixing zone;
directing at least some of the sludge separated by the separator to the intermediary zone and mixing the mix of sludge and ballast with at least a part of the separated sludge;
directing the mixture of the mix of sludge and ballast and the separated sludge from the intermediary mixing zone to the separator and continuing to return separated sludge from the separator to the intermediary mixing zone. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification