Nutrient recovery process
First Claim
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1. A method of recovering ammonia and precipitating phosphorous from a waste stream, comprising:
- separating an anaerobically digested waste stream into a solids-rich stream and an solids-depleted stream;
reacting the solids-depleted stream with lime or a lime-based solution to form a first mixture;
introducing compressed gas into the first mixture to form an aerated first mixture;
passing the aerated first mixture through a reaction zone;
passing the aerated first mixture stream through a flocculation zone, where a flocculation agent is added to the aerated first mixture to form a second mixture;
passing the second mixture stream through a settling zone, thereby removing precipitated settled solids from the second mixture stream and removing an ammonia-laden gas and a softened solids-depleted stream from the second mixture stream via sparged compressed gas;
scrubbing the ammonia-laden gas using an acidic solution to remove ammonia therefrom; and
passing at least a portion of the softened solids-depleted stream through at least one ammonia absorption column to remove ammonia therefrom,wherein introducing the compressed gas into the first mixture removes ammonia and enhances phosphorous precipitation.
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Abstract
Embodiments include a method and apparatus for cost-effective and efficient nutrient recovery from a waste stream. The nutrients recovered may include ammonia, phosphorous, and/or potassium. The ammonia and phosphorous recovery may be simultaneously accomplished. In some embodiments, ammonia is recovered along with other nutrients using lime or lime-based products.
101 Citations
38 Claims
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1. A method of recovering ammonia and precipitating phosphorous from a waste stream, comprising:
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separating an anaerobically digested waste stream into a solids-rich stream and an solids-depleted stream; reacting the solids-depleted stream with lime or a lime-based solution to form a first mixture; introducing compressed gas into the first mixture to form an aerated first mixture; passing the aerated first mixture through a reaction zone; passing the aerated first mixture stream through a flocculation zone, where a flocculation agent is added to the aerated first mixture to form a second mixture; passing the second mixture stream through a settling zone, thereby removing precipitated settled solids from the second mixture stream and removing an ammonia-laden gas and a softened solids-depleted stream from the second mixture stream via sparged compressed gas; scrubbing the ammonia-laden gas using an acidic solution to remove ammonia therefrom; and passing at least a portion of the softened solids-depleted stream through at least one ammonia absorption column to remove ammonia therefrom, wherein introducing the compressed gas into the first mixture removes ammonia and enhances phosphorous precipitation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. An apparatus for removing ammonia and phosphorous from a waste stream, comprising:
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a reacting and settling vessel comprising; at least one reaction chamber for reacting a lime or lime-based product with a solids-depleted stream, at least one flocculation chamber for adding a flocculating agent to the solids-depleted stream, at least one settling chamber for settling and precipitating a solids stream from an ammonia-laden gas, and a capability to recirculate at least a portion of settled solids back to the at least one reaction chamber; at least one gas compressor for compressing a gas prior to its introduction into the at least one reaction chamber; and at least one ammonia absorption column for separating ammonia from the compressed gas subsequent to its contact in at least one of the chambers of the reacting and settling vessel, wherein the compressed gas removes ammonia from the solids-depleted stream and enhances phosphorous precipitation. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for slow softening a waste stream having soluble calcium compounds present therein, wherein at least one alkaline precipitating agent is admixed with the waste stream to be softened in a mixing zone and then the calcium compounds are changed inside a reaction zone through which the waste stream passes after being admixed with the alkaline precipitating agent into insoluble calcium carbonate matter which is subsequently changed in a flocculation zone into settleable flocs by the addition of a flocculating agent containing trivalent metal ions, comprising:
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(1) mixing the waste stream, the alkaline precipitating agent, and an agitated liquid, gas, or combination of liquid and gas with finely divided crystalline calcium carbonate in the mixing zone prior to the addition of and in the absence of the flocculation agent to form seeds for the calcium carbonate matter which newly precipitates from the waste stream inside the reaction zone; (2) presettling and discharging at least a part of the insoluble calcium carbonate matter which has been precipitated inside the reaction zone; (3) passing the waste stream into a flocculating zone, wherein the waste stream is mixed with the flocculating agent; and (4) passing the waste stream into a sedimentation zone. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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Specification