Wastewater treatment process with pH adjustment

Claim 2

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with acid to reduce the pH of the wastewater and combining the wastewater with sufficient SO 2 so that the wastewater has a selected free SO 2 content of at least about 5 mg/liter and less than about 200 mg/liter and a pH of from about 1 to about 4; (b) maintaining the combined SO 2 /wastewater in a treatment zone at the selected free SO 2 content and pH for about 5 to about 60 minutes; and (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.

Claim 3

A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of: (a) combining the wastewater with sufficient SO 2 and with sufficient acid that the wastewater has a selected free SO 2 of at least about 5 mg/liter and less than about 200 mg/liter, and the pH of the wastewater is reduced to a pH of from about 1 to less than about 4; (b) maintaining the combined SO 2 /wastewater in a treatment zone at the selected free SO 2 content for about 10 to about 60 minutes; and (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no coliform bacteria.

Claim 4

A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of: (a) combining the wastewater with sufficient SO 2 and with sufficient acid that the wastewater has a selected free SO 2 of at least about 5 mg/liter and less than about 200 mg/liter, and the pH of the wastewater is reduced to a pH of from about 1 to less than about 4; (b) maintaining the combined SO 2 /wastewater in a treatment zone at the selected free SO 2 content for about 10 to about 60 minutes; and (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no coliform bacteria.

Claim 5

The process of claim 2 in which the step of maintaining comprises maintaining the combined SO 2 /wastewater at the selected free SO 2 content in the substantial absence of particulate iron.

Claim 6

The process of claim 2 in which the step of maintaining comprises maintaining the combined SO 2 /wastewater at the selected free SO 2 content without agitation.

Claim 7

The process of claim 1 or 2 in which the combined SO 2 /wastewater is maintained in the treatment zone for about 10 to about 60 minutes.

Claim 8

The process of claim 1 or 2 in which the combined SO 2 /wastewater is maintained in the treatment zone for about 10 to about 40 minutes.

Claim 9

The process of claim 1 or 2 in which the selected free SO 2 content is less than about 100 mg/liter.

Claim 10

The process of claim 1 or 2 in which the selected free SO 2 content is less than about 75 mg/liter.

Claim 11

The process of claim 1 or 2 in which the combined SO 2 /wastewater is maintained in the treatment zone at a pH of from about 1 to about 4.

Claim 12

The process of claim 2 including the step of burning sulphur in the presence of no more than the amount of oxygen required to insure substantially complete oxidation of the sulphur to SO 2 to produce a combustion gas comprising SO 2 and no more than about 15% by volume oxygen.

Claim 13

The process of claim 10 wherein the step of combining comprises introducing the combustion gas without any additional oxygen into the wastewater.

Claim 14

The process of claim 1 or 2 in which the combined SO 2 /wastewater is maintained in the treatment zone at a pH of from about 2 to about 3.

Claim 15

The process of claim 1 or 2 in which the step of combining with SO 2 comprises contacting a first portion of the wastewater with gaseous SO 2 to dissolve SO 2 therein and mixing the first portion with SO 2 dissolved therein with a second portion of the wastewater.

Claim 16

The process of claim 2 in which the SO 2 is gaseous.

Claim 17

The process of claim 1 or 2 in which the step of combining with SO 2 comprises mixing the wastewater with SO 2 dissolved in water.

Claim 18

The process of claim 1 or 2 in which the acid is sulfuric acid.

Claim 19

The process of claim 2 in which the acid is hydrochloric acid.

Claim 20

The process of claim 1 or 2 in which the wastewater is combined with acid before it is combined with SO 2 .

Claim 21

The process of claim 1 or 2 in which the wastewater is combined with SO 2 before it is combined with acid.

Claim 22

The process of claim 1 or 2 in which the wastewater is combined with SO 2 and acid simultaneously.

Claim 23

The process of claim 1 or 2 including the step of stripping SO 2 from the withdrawn wastewater.

Claim 24

The process of claim 21 wherein the step of combining the wastewater with SO 2 comprises combining the wastewater with SO 2 stripped from withdrawn wastewater.

Claim 25

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with sufficient SO 2 so that the wastewater has a selected free SO 2 content of from about 10 to about 75 mg/liter; (b) reducing the pH of the combined SO 2 /wastewater to a selected pH of from about 1 to about 4; (c) maintaining the combined SO 2 /wastewater of reduced pH in a treatment zone at the selected free SO 2 content and the selected pH for about 10 to about 60 minutes; (d) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; and (e) neutralizing the wastewater withdrawn from the treatment zone to a pH of from about 6 to about 8 and dissolving oxygen in the wastewater withdrawn from the treatment zone to raise its oxygen content.

Claim 26

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with sufficient SO 2 so that the wastewater has a selected free SO 2 content of from about 10 to about 75 mg/liter; (b) reducing the pH of the combined SO 2 /wastewater to a selected pH of from about 1 to about 4; (c) maintaining the combined SO 2 /wastewater of reduced pH in a treatment zone at the selected free SO 2 content and the selected pH for about 10 to about 60 minutes; (d) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; and (e) neutralizing the wastewater withdrawn from the treatment zone to a pH of from about 6 to about 8 and dissolving oxygen in the wastewater withdrawn from the treatment zone to raise its oxygen content.

Claim 27

The process of claim 23 including the step of stripping SO 2 from the wastewater withdrawn from the treatment zone before the withdrawn wastewater is neutralized.

Claim 28

The process of claim 24 in which the step of combining the wastewater with SO 2 comprises combining the wastewater with SO 2 stripped from the withdrawn wastewater.

Claim 29

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with from about 10 to about 500 mg of SO 2 per liter of wastewater so that the wastewater has a selected free SO 2 content of from about 5 to about 100 mg/liter; (b) combining the combined SO 2 /wastewater with sufficient acid so that the wastewater has a selected pH of from about 1 to about 4; (c) maintaining the combined SO 2 /wastewater/acid in a treatment zone at the selected free SO 2 content and the selected pH for about 5 to about 60 minutes; and (d) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.

Claim 30

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with from about 10 to about 500 mg of SO 2 per liter of wastewater so that the wastewater has a selected free SO 2 content of from about 5 to about 100 mg/liter; (b) combining the combined SO 2 /wastewater with sufficient acid so that the wastewater has a selected pH of from about 1 to about 4; (c) maintaining the combined SO 2 /wastewater/acid in a treatment zone at the selected free SO 2 content and the selected pH for about 5 to about 60 minutes; and (d) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.

Claim 31

The process of claim 25 or 26 in which the wastewater is combined with no more than about 300 mg of SO 2 per liter of wastewater.

Claim 32

The process of claim 26 in which the wastewater is combined with at least about 20 mg of SO 2 per liter of wastewater.

Claim 33

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) introducing a first portion of the wastewater and a SO 2 containing gas into a gas-liquid contact zone for dissolving at least a portion of the SO 2 into the first portion of the wastewater; (b) withdrawing wastewater containing SO 2 from the contact zone; (c) combining a second portion of the wastewater with SO 2 by introducing substantially all of the withdrawn wastewater containing SO 2 directly into a mixing zone and introducing the second portion of the wastewater into the mixing zone to form mixed wastewater; (d) treating the mixed wastewater with sufficient acid to reduce the pH of the mixed wastewater to a selected pH of from about 1 to less than about 4; (e) maintaining the acid treated wastewater in a treatment zone for about 5 to about 60 minutes; and (f) withdrawing treated wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms, wherein sufficient SO 2 is introduced into the contact zone and sufficient acid is combined with the mixed wastewater so the water in the treatment zone has a selected free SO 2 content of at least about 5 to less than about 200 mg/liter.

Claim 34

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) introducing a first portion of the wastewater and a SO 2 containing gas into a gas-liquid contact zone for dissolving at least a portion of the SO 2 into the first portion of the wastewater; (b) withdrawing wastewater containing SO 2 from the contact zone; (c) combining a second portion of the wastewater with SO 2 by introducing substantially all of the withdrawn wastewater containing SO 2 directly into a mixing zone and introducing the second portion of the wastewater into the mixing zone to form mixed wastewater; (d) treating the mixed wastewater with sufficient acid to reduce the pH of the mixed wastewater to a selected pH of from about 1 to less than about 4; (e) maintaining the acid treated wastewater in a treatment zone for about 5 to about 60 minutes; and (f) withdrawing treated wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms, wherein sufficient SO 2 is introduced into the contact zone and sufficient acid is combined with the mixed wastewater so the water in the treatment zone has a selected free SO 2 content of at least about 5 to less than about 200 mg/liter.

Claim 35

The process of claim 29 in which the amount of SO 2 introduced into the contact zone is such that the wastewater in the treatment zone has a selected free SO 2 content of less than about 100 mg/liter.

Claim 36

The process of claim 29 in which the amount of SO 2 introduced into the contact zone is such that the wastewater in the treatment zone has a selected free SO 2 content of less than about 75 mg/liter.

Claim 37

The process of claim 29 in which the combined withdrawn wastewater and the second portion of the reduced pH wastewater are maintained in the treatment zone for a residence time of from about 5 to about 60 minutes.

Claim 38

The process of claim 29 in which sufficient SO 2 is introduced into the gas-liquid contact zone that the wastewater withdrawn from the contact zone has a free SO 2 content of at least about 10 mg/liter.

Claim 39

The process of claim 29 in which sufficient SO 2 is introduced into the gas-liquid contact zone that the wastewater withdrawn from the contact zone has a free SO 2 content of from about 10 to about 150 mg/liter.

Claim 40

The process of claim 29, 33, or 34 in which the first portion of the wastewater comprises from about 10 to about 70 volume percent of the total wastewater.

Claim 41

The process of claim 29 including the step of introducing SO 2 containing gas into the mixing zone.

Claim 42

The process of claim 29 in which the step of maintaining comprises maintaining the contents of the treatment zone at the selected free SO 2 content in the substantial absence of particulate iron.

Claim 43

The process of claim 29 in which the step of maintaining comprises maintaining the contents of the treatment zone unagitated.

Claim 44

The process of claim 29 including the step of stripping SO 2 from wastewater withdrawn from the treatment zone.

Claim 45

The process of claim 39 in which the step of introducing SO 2 into the gas-liquid contact zone comprises introducing SO 2 stripped from withdrawn wastewater into the gas-liquid contact zone.

Claim 46

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with sufficient acid and sufficient SO 2 so that the wastewater has (i) a free SO 2 content of from about 5 to about 175 mg/liter and (ii) a pH of from about 1 to about 4; (b) maintaining the combined SO 2 /wastewater in a treatment zone at the selected free SO 2 content and the selected pH for about 5 to about 60 minutes; (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; (d) stripping SO 2 from the wastewater withdrawn from the treatment zone; (e) removing contaminants from the stripped wastewater by increasing its pH to at least about 8, flocculating it, and removing flocculated material from the flocculated wastewater; and (f) neutralizing the flocculated wastewater and dissolving oxygen in the flocculated wastewater.

Claim 47

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) combining the wastewater with sufficient acid and sufficient SO 2 so that the wastewater has (i) a free SO 2 content of from about 5 to about 175 mg/liter and (ii) a pH of from about 1 to about 4; (b) maintaining the combined SO 2 /wastewater in a treatment zone at the selected free SO 2 content and the selected pH for about 5 to about 60 minutes; (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; (d) stripping SO 2 from the wastewater withdrawn from the treatment zone; (e) removing contaminants from the stripped wastewater by increasing its pH to at least about 8, flocculating it, and removing flocculated material from the flocculated wastewater; and (f) neutralizing the flocculated wastewater and dissolving oxygen in the flocculated wastewater.

Claim 48

The process of claim 41 in which the step of combining the wastewater with SO 2 comprises combining the wastewater with SO 2 stripped from the wastewater withdrawn from the treatment zone.

Claim 49

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) treating the wastewater by combining the wastewater with sufficient SO 2 so that the wastewater has a selected free SO 2 content of at least about 5 mg/liter and a pH of less than about 4; (b) maintaining the combined SO 2 wastewater in a treatment zone at the selected free SO 2 content and pH for at least about 5 minutes; (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; (d) stripping SO 2 from the treated withdrawn wastewater; and (e) combining the SO 2 stripped from withdrawn wastewater with untreated wastewater.

Claim 50

A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of: (a) treating the wastewater by combining the wastewater with sufficient SO 2 so that the wastewater has a selected free SO 2 content of at least about 5 mg/liter and a pH of less than about 4; (b) maintaining the combined SO 2 wastewater in a treatment zone at the selected free SO 2 content and pH for at least about 5 minutes; (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms; (d) stripping SO 2 from the treated withdrawn wastewater; and (e) combining the SO 2 stripped from withdrawn wastewater with untreated wastewater.

Claim 51

The process of claim 43 including the additional step of combining wastewater having SO 2 stripped therefrom with a base to raise the pH of the wastewater.

Claim 52

The process of claim 43 including the step of combining the wastewater containing infectious microorganisms with acid.