System and method for reducing the pathogen concentration of sludge
First Claim
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1. A method of treating sludge to reduce pathogens within the sludge, comprising:
- a. directing incoming sludge through a first heat exchanger;
b. directing the incoming sludge from the first heat exchanger to one or more reactors for holding and treating the sludge;
c. directing the treated sludge from the one or more reactors through a second heat exchanger;
d. directing a heat transfer medium through the first and second heat exchangers for efficiently heating the incoming sludge and cooling the treated sludge;
e. directing the treated sludge from the second heat exchanger and ultimately to a digester; and
f. varying the flow of the heat transfer medium through the first and second heat exchangers so as to cool the treated sludge to a target temperature range before reaching the digester.
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Abstract
A waste treatment system comprises a first heat exchanger positioned before one or more reactors. The reactors discharge treated sludge to a second heat exchanger. The first and second heat exchangers share a heat transfer medium wherein the heat from the treated sludge is transferred to the incoming sludge. The treated sludge is cooled to reach an optimal temperature range before entry into a digester. The system also is adapted to allow a pipe cleaning device or “pig” to clean the heat exchangers by being forced through the heat exchangers by pressurized and pasteurized wastewater.
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Citations
23 Claims
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1. A method of treating sludge to reduce pathogens within the sludge, comprising:
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a. directing incoming sludge through a first heat exchanger;
b. directing the incoming sludge from the first heat exchanger to one or more reactors for holding and treating the sludge;
c. directing the treated sludge from the one or more reactors through a second heat exchanger;
d. directing a heat transfer medium through the first and second heat exchangers for efficiently heating the incoming sludge and cooling the treated sludge;
e. directing the treated sludge from the second heat exchanger and ultimately to a digester; and
f. varying the flow of the heat transfer medium through the first and second heat exchangers so as to cool the treated sludge to a target temperature range before reaching the digester. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A predigestion pathogen reduction system for removing pathogens from sludge, comprising:
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a. a first heat exchanger for receiving incoming sludge and heating the same;
b. one or more reactors in fluid communication with the first heat exchanger for receiving sludge therefrom, the one or more reactors adapted to hold and treat the heated sludge;
c. a second heat exchanger disposed in fluid communication with the one or more reactors for receiving treated sludge therefrom and cooling the treated sludge as it passes through the second heat exchanger;
d. a digester located down stream from the second heat exchanger for receiving treated sludge after the same has been cooled by the second heat exchanger;
e. a heat transfer medium contained within a closed loop that extends in a heat exchange relationship with both the first and second heat exchangers and wherein the heat transfer medium functions to remove heat from the treated sludge and add heat to the incoming sludge; and
f. a variable speed pump connected within the closed loop for pumping the heat transfer medium through the first and second heat exchangers and for varying the flow rate of the heat transfer medium in the closed loop so as to cool the treated sludge to a target temperature range prior to the treated sludge reaching the digester. - View Dependent Claims (13, 14, 15, 16)
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17. A method of transferring heat in a pathogen reduction system for sludge, comprising:
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a. directing incoming, pathogen bearing sludge through a first heat exchanger and heating the incoming sludge;
b. introducing the heated incoming sludge to one or more reactors to reduce the pathogens therein to create treated sludge;
c. directing the treated sludge from the one or more reactors to a second heat exchanger and cooling the treated sludge;
d. transferring the treated sludge to a digester; and
e. transferring heat from the treated sludge to the incoming sludge by directing a closed loop through the first and second heat exchangers and channeling a heat exchange medium through the closed loop in a direction counter to the flow of both the incoming sludge and the treated sludge and relying solely on the heat transfer characteristics of the heat transfer medium to transfer heat from the treated sludge to the incoming sludge. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification