Biological treatment of waste water
First Claim
1. A method for biologically purifying waste water containing biodegradable substances comprising the steps of:
- a. contacting the waste water with microorganisms in a biological fixed film type reactor under conditions sufficient to degrade the biodegradable substances and to produce a sludge which contains a mixture of bacteria, protozoa, and large organisms;
b. separating and concentrating the sludge from the biologically treated waste water discharged from the reactor of step (a) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a static inclined screen separator;
c. aerobically digesting the sludge discharged from the separator of step (b) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a digester; and
d. returning substantially all of the digested sludge containing live protozoa and live organisms to the reactor of step (a) or to a line upstream thereof, whereby substantially all of the sludge is recycled.
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Abstract
A method for biologically purifiying waste water which produces substantially no excess waste sludge is provided. In this method, a waste water containing biodegradable substances is treated in a biological fixed film type reactor and aqueous water sludge discharged from the reactor is aerobically digested after being separated from the biologically treated waste water. The digested aqueous sludge is returned to the reactor or the upstream thereof. This method can be advantageously combined with any installed activated sludge type water purification process, to thereby substantially eliminate the production of excess waste sludge from the water purification system.
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Citations
22 Claims
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1. A method for biologically purifying waste water containing biodegradable substances comprising the steps of:
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a. contacting the waste water with microorganisms in a biological fixed film type reactor under conditions sufficient to degrade the biodegradable substances and to produce a sludge which contains a mixture of bacteria, protozoa, and large organisms; b. separating and concentrating the sludge from the biologically treated waste water discharged from the reactor of step (a) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a static inclined screen separator; c. aerobically digesting the sludge discharged from the separator of step (b) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a digester; and d. returning substantially all of the digested sludge containing live protozoa and live organisms to the reactor of step (a) or to a line upstream thereof, whereby substantially all of the sludge is recycled. - View Dependent Claims (2, 3, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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4. A method for biologically purifying waste water containing biodegradable substances comprising the steps of:
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a. dividing a stream of the waste water into two portions; b. contacting a portion of the waste water with suspended microorganisms in water in an activated sludge type reactor under conditions sufficient to degrade the biodegradable substances to produce a sludge; c. simultaneously and separately treating another portion of the waste water by contact with microorganisms in a biological fixed film type reactor under conditions sufficient to degrade the biodegradable substances and to produce a sludge which contains a mixture of bacteria, protozoa, and large organisms; d. separating and concentrating the sludge from the biologically treated waste water discharged from the reactor of step (c) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a static inclined screen separator; e. aerobically digesting a mixture of sludges discharged from the reactor of step (b) and the separator of step (d) in the presence of sufficient oxygen to maintain life in the protozoa and large organisms of the sludge by using a digester; and f. returning substantially all of the digested sludge containing live protozoa and live organisms to the reactor of step (b), to the reactor of step (c) or to a line upstream thereof, whereby substantially all of the sludge is recycled. - View Dependent Claims (5, 6, 7, 8)
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Specification