Methods and systems for treating fluid using a biochemical process under vacuum pressure
Methods and systems are described for treating a fluid that includes a particulate fraction and a soluble fraction, such as wastewater fluid including biosolids. The treatment includes biochemically transforming solids in the particulate fraction of the fluid in a biochemical process while simultaneously subjecting the fluid to a vacuum pressure, and evaporating off at least a portion of the soluble fraction of the fluid and thereby thickening a remaining portion of the fluid. A residence time of the particulate fraction can be controlled to be at least 25% greater than a residence time of the soluble fraction, for example. A solids content of the particulate fraction can be controlled to be in a range of from 2% to 99%, for example.
1 . A method for treating a fluid that includes a particulate fraction and a soluble fraction, the method comprising:
feeding the fluid to a treatment chamber;
physically and biochemically transforming solids in the particulate fraction of the fluid with microbes in the treatment chamber;
feeding at least a portion of the fluid that has been physically and biochemically treated in the treatment chamber to a vacuum chamber in which a vacuum pressure is applied to the fluid;
evaporating off at least a portion of the soluble fraction of the fluid in the vacuum chamber as evaporate so that a thickened fluid remains in the vacuum chamber;
recirculating at least some of the thickened fluid to the treatment chamber so that it is further physically and biochemically transformed; and
controlling an amount of a dissolved gas that is stripped from the fluid into the evaporate by adjusting at least one parameter of the fluid in the treatment chamber.
2 . The method according to claim 1 , wherein 100% of the thickened fluid that is removed from the vacuum chamber is recycled to the treatment chamber.
3 . The method according to claim 1 , wherein the treatment chamber is an anaerobic digester or an aerobic digester.
4 . The method according to claim 1 , wherein the fluid is treated at pressures greater than the vacuum pressure for a longer duration than periods at which the fluid is subjected to the vacuum pressure.
5 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a pH that is in a range of from 2.39 to 6.68.
6 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a conductivity that is in a range of from 1.52 mS/cm to 2.50 mS/cm.
7 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a total chemical oxygen demand that is in a range of from 22,550 mg/L to 51,750 mg/L.
8 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a soluble chemical oxygen demand that is in a range of from 660 mg/L to 3420 mg/L.
9 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having volatile fatty acids in an amount of from 296.9 mg/L to 1691.7 mg/L.
10 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having total phosphorous in an amount of from 12.4 mg/L to 138.3 mg/L.
11 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having ammonium in an amount of from 25 mg/L to 93.6 mg/L.
12 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a total solids that is in a range of from 2.2% to 3.5%.
13 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge having a total volatile solids that is in a range of from 1.4% to 2.6%.
14 . The method according to claim 1 , wherein (i) the fluid that is fed to the treatment chamber is a sludge, and (ii) the method further comprises condensing the portion of the soluble fraction that is evaporated off in the vacuum chamber to provide a condensate.
15 . The method according to claim 14 , wherein the condensate has a pH that is in a range of from 3.68 to 9.26.
16 . The method according to claim 14 , wherein the condensate has a conductivity that is in a range of from 0.09 mS/cm to 0.58 mS/cm.
17 . The method according to claim 14 , wherein the condensate has a total chemical oxygen demand that is in a range of from 160 mg/L to 2025 mg/L.
18 . The method according to claim 14 , wherein the condensate has a soluble chemical oxygen demand that is in a range of from 123 mg/L to 2,190 mg/L.
19 . The method according to claim 14 , wherein the condensate has volatile fatty acids in an amount of from 24.8 mg/L to 671.5 mg/L.
20 . The method according to claim 14 , wherein the condensate has total phosphorous in an amount of from 3.6 mg/L to 70.3 mg/L.
21 . The method according to claim 14 , wherein the condensate has ammonium in an amount of from 5.4 mg/L to 87.5 mg/L.
22 . The method according to claim 14 , wherein the condensate has total suspended solids in an amount of from 0.4 mg/L to 18.8 mg/L.
23 . The method according to claim 14 , further comprising recovering heat from the evaporate during the condensing step, and preheating the fluid with the recovered heat before the fluid is fed to the treatment chamber.
24 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a pH in a range of from 5.7 to 6.7.
25 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a conductivity that is in a range of from 1.7 mS/cm to 21.0 mS/cm.
26 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a total chemical oxygen demand in a range of from 22466.7 mg/L to 501147.1 mg/L.
27 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a soluble chemical oxygen demand that is in a range of from 3,430.0 mg/L to 59,837.4 mg/L.
28 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has volatile fatty acids in a range of from 368.4 mg/L to 14,701.8 mg/L.
29 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has total phosphorous (sP) in an amount of from 303.6 mg/L to 1,142.0 mg/L.
30 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has ammonium in an amount of from 110.8 mg/L to 2,165.9 mg/L.
31 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has ammonium in an amount of from 100 mg/L to 50,000 mg/L.
32 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a total solids that is in a range of from 3.0% to 28.9%.
33 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein the thickened fluid has a total volatile solids that is in a range of from 1.0% to 19.5%.
34 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber is a sludge, and wherein a residence time of the particulate fraction of the sludge is controlled so that biosolids in the sludge are stabilized to Class A biosolids.
35 . The method according to claim 1 , wherein the fluid that is fed to the treatment chamber includes biosolids that are selected from the group consisting of wastewater treatment biosolids, biosolids from an organic fraction of municipal solid wastes, food waste biosolids, organic industrial waste biosolids, agricultural waste biosolids, and combinations thereof.
36 . The method according to claim 1 , further comprising feeding the recirculated thickened fluid to the vacuum chamber and applying the vacuum pressure to the recirculated thickened fluid to further dewater the recirculated thickened fluid to produce ultra-dewatered biosolids.
37 . The method according to claim 36 , further comprising sending the ultra-dewatered biosolids to a downstream process.
38 . The method according to claim 36 , wherein the ultra-dewatered biosolids have a particulate solids concentration that exceeds a capability of mechanical separation devices.
39 . The method according to claim 1 , wherein, once the recirculated thickened fluid reaches a desired level of transformation, further comprising applying the vacuum pressure to the recirculated thickened fluid to further dewater the recirculated thickened fluid to produce ultra-dewatered biosolids.
40 . The method according to claim 1 , wherein the dissolved gas includes carbon dioxide, and the controlling step includes controlling an amount of carbon dioxide that is stripped from the fluid into the evaporate in the evaporate by adjusting the at least one parameter of the fluid.
41 . The method according to claim 1 , wherein the dissolved gas includes ammonia, and the controlling step includes controlling an amount of ammonia that is stripped from the fluid into the evaporate by adjusting the at least one parameter of the fluid.
42 . The method according to claim 1 , wherein the at least one parameter of the fluid is selected from the group consisting of salinity, temperature, and pH.
43 . The method according to claim 1 , wherein the at least one parameter of the fluid includes pH.
44 . The method according to claim 1 , wherein the dissolved gas includes ammonia, the at least one parameter includes pH, and the controlling step includes controlling an amount of ammonia that is stripped from the fluid into the evaporate by adding a pH adjusting agent to the fluid to adjust a pH of the fluid.
45 . The method according to claim 44 , further comprising recovering the ammonia from the evaporate.
46 . The method according to claim 45 , wherein recovering the ammonia from the evaporate includes bubbling the evaporate through a sulfuric acid bath.
47 . The method according to claim 14 , wherein the condensate is rich in ammonia relative to the fluid, and the method further comprises recovering the ammonia in the condensate.