Wastewater treatment process with pH adjustment
First Claim
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1. 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 SO2 so that the wastewater has a selected free SO2 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 SO2 /wastewater in a treatment zone at the selected free SO2 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(c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms.
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Abstract
Wastewater is continuously disinfected by combining the wastewater with sufficient acid to reduce the pH of the wastewater to less than about 4 and with sufficient SO2 that the wastewater has a selected free SO2 content of at least 5 mg/liter. The combined SO2 /wastewater is maintained at the selected free SO2 content for at least about 5 minutes. The wastewater can be treated by dissolving SO2 into a first portion of the wastewater and combining the first portion with SO2 dissolved therein with a second portion of the wastewater stream. SO2 can be stripped from the wastewater, and the stripped SO2 can be recycled.
85 Citations
45 Claims
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1. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) combining the wastewater with acid to reduce the pH of the wastewater and combining the wastewater with sufficient SO2 so that the wastewater has a selected free SO2 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 SO2 /wastewater in a treatment zone at the selected free SO2 content and pH for about 5 to about 60 minutes; and (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no infectious microorganisms. - View Dependent Claims (5, 6, 7, 8, 9, 12, 13, 15, 16, 18, 19, 20, 21, 22)
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2. A continuous process for disinfecting wastewater containing coliform bacteria comprising the steps of:
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(a) combining the wastewater with sufficient SO2 and with sufficient acid that the wastewater has a selected free SO2 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 SO2 /wastewater in a treatment zone at the selected free SO2 content for about 10 to about 60 minutes; and (c) withdrawing wastewater from the treatment zone, the withdrawn wastewater containing substantially no coliform bacteria. - View Dependent Claims (3, 4, 10, 11, 14, 17)
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23. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) combining the wastewater with sufficient SO2 so that the wastewater has a selected free SO2 content of from about 10 to about 75 mg/liter; (b) reducing the pH of the combined SO2 /wastewater to a selected pH of from about 1 to about 4; (c) maintaining the combined SO2 /wastewater of reduced pH in a treatment zone at the selected free SO2 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. - View Dependent Claims (24, 25, 27)
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26. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) combining the wastewater with from about 10 to about 500 mg of SO2 per liter of wastewater so that the wastewater has a selected free SO2 content of from about 5 to about 100 mg/liter; (b) combining the combined SO2 /wastewater with sufficient acid so that the wastewater has a selected pH of from about 1 to about 4; (c) maintaining the combined SO2 /wastewater/acid in a treatment zone at the selected free SO2 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. - View Dependent Claims (28)
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29. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) introducing a first portion of the wastewater and a SO2 containing gas into a gas-liquid contact zone for dissolving at least a portion of the SO2 into the first portion of the wastewater; (b) withdrawing wastewater containing SO2 from the contact zone; (c) combining a second portion of the wastewater with SO2 by introducing substantially all of the withdrawn wastewater containing SO2 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 SO2 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 SO2 content of at least about 5 to less than about 200 mg/liter. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) combining the wastewater with sufficient acid and sufficient SO2 so that the wastewater has (i) a free SO2 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 SO2 /wastewater in a treatment zone at the selected free SO2 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 SO2 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. - View Dependent Claims (42)
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43. A continuous process for disinfecting wastewater containing infectious microorganisms comprising the steps of:
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(a) treating the wastewater by combining the wastewater with sufficient SO2 so that the wastewater has a selected free SO2 content of at least about 5 mg/liter and a pH of less than about 4; (b) maintaining the combined SO2 wastewater in a treatment zone at the selected free SO2 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 SO2 from the treated withdrawn wastewater; and (e) combining the SO2 stripped from withdrawn wastewater with untreated wastewater. - View Dependent Claims (44, 45)
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Specification