PROCEDURE FOR PROVIDING AND IMPROVING PUMPABILITY OF HIGH TO VERY HIGH BIOSOLIDS CONTAINING DEWATERED SOLID SEWAGE SLUDGE

Abstract

The invention provides a process for the drying and re-hydration of high solids Biosolids cake to be converted into a pumpable organic liquid fertilizer. This process may be carried out at ambient pressure without aggressive shearing of the mixture of added process water and the high solids Biosolids cake. The drying step removes the bound water, while the re-hydration step includes mixing which breaks down the particulate matter to produce a fairly homogeneous suspension.

Claims

1. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake including an initial biosolids component content greater than 18% w/w and limited free water, as an organic liquid fertilizer, comprising: (a) firstly, increasing the biosolids content of the mass by more than 5% w/w from the initial biosolids content by partially drying the biosolids component to a resultant dried biosolids content, (a) secondly, re-hydrating the mass by mixing a quantity of process water into the mass to produce a re-hydrated mass with a biosolids content of greater than 18% w/w, and then, (b) evaluating the viscosity of the mass as pumpable.

2. An industrial procedure for improving pumpability of a mass of solid high solids biosolids case as claimed in claim 1 wherein the procedure is carried out at ambient pressure.

3. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the procedure does not include aggressive shearing of the mass.

4. (canceled)

5. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1, wherein the procedure alters the character of the biosolids component substantially only by drying.

6. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the biosolids content of the mass is increased to 24-25% w/w in the first step and the re-hydration step produces a re-hydrated mass with a biosolids component content of 18% w/w or more.

7. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the biosolids content of the mass is increased to 25-30% in the first step and the re-hydration step produces a re-hydrated mass with a biosolids component content of 18% or more.

8. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the biosolids component of the mass is increased to more than 30% and less than 80% in the first step while remaining sticky and the re-hydration step produces a re-hydrated mass 18% or more.

9. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the biosolids component content of the mass is more than 80% in non-sticky hard pellet form after the first step, including a step of grinding the pellets, along with mixing and evaluating.

10. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 5 wherein the initial biosolids content of the mass is between 22-30% biosolids w/w and the resultant mass includes a biosolids component content of one of: (a) 35% or more, (b) 35-37%, (c) 40% or more, (d) 45% or more, (e) 50% or more, (f) 60% or more, or (g) 70% or more.

11. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 10 wherein the resultant mass is re-hydrated to a biosolids component content of: (a) 20%, (b) 22.5%, (c) 24%, (d) 25%, (e) 26% or (f) 30% while mixing in the process water.

12. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 11 wherein the procedure includes the further steps of mixing in supplemental process water while retaining the biosolids content above 20% w/w and re-evaluating the viscosity of the mass as pumpable.

13. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the initial biosolids content of the mass is between 24-25.6% biosolids w/w and the resultant dried mass includes a biosolids component of 35-37%.

14. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the drying is carried out at an elevated temperature below 100 degrees Celsius.

15. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein the drying is carried out at an elevated temperature provided by a heat source of either: (a) less than 100 degrees Celsius, or (b) between 100 and 200 degrees Celsius.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

21. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 1 wherein either: (a) the re-hydration step includes the addition of a hydrolizing agent, and/or (b) an extended period of further thermal incubation following completion of the mixing step.

22. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 21 wherein the hydrolizing agent is lime.

23. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 21 wherein the hydrolizing agent comprises less than 4% of the total solids in the re-hydrated mass, w/w.

24. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 18 wherein the extended period is more than 2.5 hours at a temperature greater than 90 degrees Celsius.

25. (canceled)

26. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake, including a biosolids component of greater than 10% w/w and limited free water, as an organic liquid fertilizer, comprising: (a) firstly, reducing the free water component by de-watering the mass to a biosolids component of 18% w/w or more, and (b) secondly, increasing the biosolids content of (in description defined as drying, evaporation or desiccation) the mass by more than 5% w/w by partially drying the biosolids component, (c) thirdly, re-hydrating the mass by mixing a quantity of process water back into the mass to produce a re-hydrated mass with a biosolids component of greater than 18% w/w, and then, (d) evaluating (defined term in the description, broad) the viscosity of the mass as pumpable.

27. (canceled)

28. (canceled)

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35. (canceled)

36. (canceled)

37. (canceled)

38. (canceled)

39. An industrial procedure for improving pumpability of a mass of solid high solids biosolids cake as claimed in claim 21 where the alkali dose rate for treatment of biosolids cake is proportional to cake solids concentration.

40. (canceled)

41. (canceled)

42. (canceled)

43. A method of making a mass of dried biosolids products pumpable, the method comprising: (a) re-hydrating the mass by mixing a quantity of process water into the mass to produce a re-hydrated mass with a biosolids content of greater than 18% w/w; and (b) evaluating the viscosity of the re-hydrated mass as pumpable.

Description

DRAWINGS

[0104] FIG. 1 is a table (1) providing process details of the first embodiment.

[0105] Title: Table 1 Summary from Individual Thermal Treatment (Drying) (Except Microwave) without Lime

TABLE-US-00001 Legend For FIG. 1 The numbers across the top of the table indicate column numbers The reference letters in the first column are row references Rows A, B, C1, C2, C4 display prior art results In this table Column 1 Row 02 Cake Heating System Column 2 Row 02 Temperature degrees Celsius Column 3 Row 02 Hold Time (hours) Column 4 Row 02 Start Cake Solids (BSC) percent (%) Column 5 Row 02 End Cake Solids (DBSC) percent (%) Column 6 Row 02 Dilute to Solids content of (RDBSC) percent (%) Column 7 Row 02 Aggressively Mix Column 8 Row 02 Viscosity cP Column 9 Row 02 Viscosity Next Day cP Column 10 Row 02 Dilute to: percent (%) Column 11 Row 02 Viscosity cP Column 12 Row 02 Viscosity Next Day cP Column 13 Row 02 Note Column 1 Row A &A2 Autoclave Column 7 Row A Shake Column 7 Row A2 Shear 1 minute Column 1 Rows B, C1, C2, C3 Waterbath Column 7 Rows B, C1, C21, C4 Shear 1 minute Column 1 Row F & F2 Crock Pot Column 7 Row F &F2 Mix Column 1 Row G& G2 Saucepan on Hot Plate Column 3 Row G & G2 Hot plate at temperature 180 degrees Celsius Column 7 Row G& G2 vigorously mix Column 1 Row H Pyrex in Oven Column 7 Row H vigorously mix Column 13 Row H Pyrex contents raised to 90° Celsius in waterbath then transferred to oven Column 1 Row P4.1 Pyrex in oven Column 7 Row P4.1 vigorously mix Column 13 Row P4.1 Diluted to 28%, mixed, held at 95° C. 3 h and 21 h, diluted to 26% Column 1 Row P4.2 Pyrex in Oven Column 7 Row P4.2 vigorously mix Column 1 Row U Pyrex in Oven Column 7 Row U vigorously mix Column 3 Row U Pyrex contents raised to 90 degrees Celsius in waterbath then transferred to oven Column 1 Row Q & Q2 Pyrex in Oven Column 7 Row Q&Q2 vigorously mix

[0106] FIG. 1a is a summary table (1a) showing the FIG. 1 embodiment graphically.

[0107] Title: Thermal Treatment (Drying) Experiments (Except Microwave) without Lime

[0108] Estimated Solids content of Liquid Product at 6000 cP (Next Day Values)

TABLE-US-00002 Legend For FIG. 1a Rows A, B, C1, C2, C4 show results described in “prior art”. Column 1 Row 00 Cake Heating System Column 2 Row 00 Temperature - degrees Celsius Column 3 Row 00 Hold Time (hours) Column 4 Row 00 Start Cake Solids percent (%) Column 5 Row 00 End Cake Solids percent (%) Column 6 Row 00 Dilute to Solids content of percent (%) Column 7 Row 00 Mix Columns 8+ Row 00 Solids Content of Liquid Product @ 6000 cP (Next Day Values) in percent (%) Column 1 Row A1 & A2 Autoclave (No evaporation) Column 7 Row A1 Shake Column 7 Row A2 Shear 1 minute Column 1 Rows B.C1, C2, C4 Waterbath (No evaporation) Column 7 Rows B.C1, C2, C4 Shear 1 minute Column 1 Row F & F2 Crock Pot Column 7 Row F & F2 Mix Column 1 Row G &G2 Saucepan on Hot Plate Column 2 Row G & G2 Hot Plate Temperature 180° C. Column 7 Row G &G2 vigorously mix Column 1 Rows H, P4.1, P4.2 Pyrex in Oven Column 7 Row H, P4.1, P4.2 vigorously mix Column 1 Row U, Q Pyrex in Oven Column 7 Row U, Q vigorously mix

[0109] FIG. 2 is a table (2) providing process details of the second embodiment.

[0110] Title: Table 2 Microwave Thermal Treatment (Drying) without Lime

TABLE-US-00003 Legend For FIG. 2 Column 1 Row 1 Cake Heating System Column 2 Row 1 24-25 percent (%) (BSC) Column 3 Row 1 Hold time in minutes Column 4 Row 1 End Cake Solids (DBSC) percent (%) Column 5 Row 1 Dilute to Solids content of (RDBSC) percent (%) Column 6 Row 1 Mix Column 7 Row 1 Heat 3 hours at 95 degrees Celsius Column 8 Row 1 Viscosity cP Column 9 Row 1 Viscosity Next Day cP Column 10 Row 1 Dilute to 15 percent (%) Viscosity cP Column 11 Row 1 Viscosity Next Day cP Column 1 Row R1 Microwave Column 6 Rows R1& S3 Aggressive mix for 1 minute Column 1 Row S3 Microwave Column 6 Row S3 Aggressive mix for 1 minute Column 10 Row S3 Dilute and Retest Column 11 Row S3 Dilute and Retest N = no Y = yes

[0111] FIG. 2a is a summary table (2) showing the FIG. 2 embodiment graphically.

[0112] Title: TABLE 2a Microwave Thermal Treatment (Drying) without Lime

TABLE-US-00004 Legend For FIG. 2a Column 1 Row 00 Cake Heating System Column 2 Row 00 Hold Time in Minutes Column 3 Row 00 End Cake Solids (DBSC) percent (%) Column 4 Row 00 Rehydrate to Solids content of percent (%) Column 5 Row 00 Mix Column 6 Row 00 Heat 3 hours at 95 degrees Celsius Column 7+ Row 00 Solids Content of Liquid Product @ 6000 cP (Next Day Values) Column 1 Row R1 Microwave 1000 watt Column 5 Row R1 Aggressive mixing for 1 minute Column 1 Row S3 Microwave 1000 watt Column 5 Row S3 Aggressive mixing for 1 minute N = no Y = yes

[0113] FIG. 3 is a table (3) providing process details of the third embodiment.

[0114] Title: Table 3 Thermal Treatment (Conventional Drying Except Microwaved) with Lime Addition

TABLE-US-00005 Legend For FIG. 3 Column 1 Row 00 Cake Heating System 180-200 degrees Celsius Column 2 Row 00 Cake Weight grams + BS % Column 3 Row 00 Temperature Hold Time in hours Column 4 Row 00 After Cook solids % Column 5 Row 00 Cal 85% added per 24% BS Column 6 Row 00 Dilute to BS content of Column 7 Row 00 Mix Column 8 Row 00 Incubate (hours/temperature - degrees Celsius) Column 9 Row 00 Viscosity cP Column 10 Row 00 Next Day Viscosity cP Column 11 Row 00 Dilute to BS Content of Column 12 Row 00 Viscosity cP Column 13 Row 00 Next Day cP Column 14 Row 00 Dilute to BS content of Column 15 Row 00 Viscosity cP Column 16 Row 00 Dilute to BS content of Column 17 Row 00 Viscosity cP Column 1 Row J Convection Cook Column 7 Row J Mix for 1 minute Column 1 Row K Convection Cook Column 7 Row K Mix for 1 minute Column 1 Row M Convection Cook Column 7 Row M Mix for 1 minute Column 1 Row V Convection Cook at 200 degrees Celsius Column 7 Row V Mix for 1 minute

[0115] FIG. 4 is a table (4) providing process details of the forth embodiment.

[0116] Title: Table 4 Microwave Thermal Treatment (Drying Experiments with Lime Addition)

TABLE-US-00006 Legend For FIG. 4 Column 1 Row 00 Cake Heating System Column 2 Row 00 Cake Weigh (grams)/% BS Column 3 Row 00 Temperature hold time in minutes Column 4 Row 00 After Cook Solid (DBSC) % Column 5 Row 00 Cal 85 based on 24% BS (%) Column 6 Row 00 Dilute to BS percent (%) of Column 7 Row 00 Mix (RDBSC) for minutes Column 8 Row 00 Incubate hours/degrees Celsius Column 9 Row 00 Viscosity cP Column 10 Row 00 Next Day Viscosity cP Column 11 Row 00 Dilute to BS Content of Column 12 Row 00 Viscosity Column 1 Rows S1, S2, 54 Microwave 1000 watt Column 1 Rows S52, S6 Microwave 1000 watt Note: RDBSC in rows S52 & S6 receive aggressive mixing for 1 minute

[0117] FIG. 4a is a summary table (4a) showing the FIG. 4 embodiment graphically.

[0118] Title: Microwave Thermal Treatment (Drying) Experiments with Lime

TABLE-US-00007 Legend For FIG. 4a Column 1 Row 00 Cake Heating System Column 2 Row 00 Cake Weight grams/% BS Column 3 Row 00 Hold time in minutes Column 4 Row 00 After cook Solid percentage (%) Column 5 Row 00 Cal 85, % based on 24% BS Column 6 Row 00 Dilute to BS % of Column 7 Row 00 Mix (RDBSC) time in minutes Column 8 Row 00 Incubate (hours at degrees Celsius) Column 9+ Row 00 Solids Content of Liquid Product @ 6000 cP (Next Day Values) Column 1 Rows S1, S2, Microwave 1000 watt S52, S6

[0119] FIG. 5 is a table (5) providing process details of the fifth embodiment with air drying.

[0120] Title: Table 5: Non-Thermal Air Drying (Low Temperature) without and with Lime

[0121] Solids Content of Liquid Product at 6000 cP (Next Day Values)

TABLE-US-00008 Legend for FIG. 5 Column 1 Row 00 Cake Drying System Column 2 Row 00 Temperature (degrees Celsius) Column 3 Row 00 Hold time in hours Column 4 Row 00 Start Cake Solids BSC percent (%) Column 5 Row 00 End Cake Solids DBSC percent (%) Column 6 Row 00 Dilute to Solids content of (RDBSC) percent (%) Column 7 Row 00 Cal 85, % based on 24% BS Column 8 Row 00 Mix Column 9+ Row 00 Solids Content of Liquid Product @ 6000 cP (Next Day Values) Column 1 Rows (1), (1)a Salton Air Dryer Column 1 Rows (2), (2)a Salton Air Dryer Column 8 Rows (1), (1)a, Aggressive mixing Column 8 Rows (2), (2)a Aggressive mixing Column 9+ Row (1) No Heat Column 9+ Row (2) No Heat

[0122] FIG. 6 is a table (6) providing process details of a variation of the fifth embodiment.

[0123] Title: Table 6. Drying without Heat ie Dehumidification Drying Followed by Aggressive Mixing

TABLE-US-00009 Legend For FIG. 6 Column AA Row 00 Cake Drying System Column BB Row 00 Cake Weight 25% (grams) Column CC Row 00 After Drying Solid % Column DD Row 00 Water Removed - milliliters Column EE Row 00 Cal 85 based on 24% BS (%) Column FF Row 00 Mixing Column GG Row 00 Rehydrate % BS Column HH Row 00 Incubate (hours/degrees Celsius) Column II Row 00 Viscosity (cP) Column JJ Row 00 Drying Time (approximate) hours Column KK Row 00 6000 cps liquid BS content at Column LL Row 00 Water removed per hour Column AA Rows 1-9 Dehumidifier (rating 70 p/24 hours) Column FF Rows 1-9 60 seconds-90 seconds increasing down the table with dryer material

[0124] FIG. 7 is a table (7) providing process details of another embodiment with the drying step a combination of air drying and thermal drying.

[0125] Title: Table 7. Dehumidification Drying with Convention Oven Completion

TABLE-US-00010 Legend For FIG. 7 Column 1 Row 00 Starting BS weight (g)/BS % Column 2 Row 00 Dehumidify to Column 3 Row 00 Heat Dry To Column 4 Row 00 Rehydration to (Total weight/% BS/% TS) Column 5 Row 00 Cal 85, % added Column 6 Row 00 Aggressive Mixing - minutes Column 7 Row 00 Incubate 3 hours/95 degrees Celsius Column 8 Row 00 Viscosity cP Column 2 Row 001 Weight/percent (%) Column 2a Row 001 Water Removed/grams Column 3 Row 001 Weight/percent (%) Column 3a Row 001 Water Removed/grams Column 4 Row 001 Weight/percent (%) Column 5 Row 001 based on 25% BSC Y = yes N—no

[0126] FIG. 8 is a table (8) providing process details of another embodiment with air drying to 90%, rough grinding and re-hydration with/without lime addition.

[0127] Title: Table 8. Rehydration 90% Air Dried Biosolids (Quick Mix) to 45% Pumpable Liquid: Effect of Lime Concentration

TABLE-US-00011 Legend For FIG. 8 90% BSC prepared from 25% cake by air drying using a (Food) air dryer. 90% Dry material was rough ground in a Ninja.sup.( ™.sup.) professional signal homogenizer (approx time 10 seconds) Column AA Row 00 Starting BS Weight/% Column BB Row 00 Water Added - grams Column CC Row 00 Add Ca(OH)2 (based on 4% Cal85/Kg of 25% Cake (grams/%) Column DD Row 00 BS Concentration Column EE Row 00 TS Concentration Column FF Row 00 Mix augur BD hand mixer - 30 seconds Column GG Row 00 Viscosity Start Column HH Row 00 Next Day Dilute to [BS] % Column II Row 00 Viscosity (cP)

[0128] FIG. 9 (table 11 is a table providing a summary of options in respect of Dried Biosolids Cake materials.

[0129] Title: Table 11 Summary of Options: Drying to Produce High Concentration Pumpable Liquids or Slurries

TABLE-US-00012 Legend For FIG. 9 Column 1-6 Row 0 Process Combination Column 7-9 Row 0 Product Properties Column 10 Row 0 Key Parameter Impact Column 1-2 Row 00 Drying Process Column 3-4 Row 00 Liquid Rehydraftion Column 6 Row 00 Drying Range Achieved due to A and H (A = Air drying; H = thermal drying Column 7 Row 00 Consistency Column 1 Row 001 Air Column 2 Row 001 Heat Column 3 Row 001 Lime Added Column 4 Row 001 Liquid Added Column 5 Row Ao Air drying followed by hydration thoughout Column 5 Rows Ao, A, pumpable liquid B, C, D, Column 5 Row A Air drying followed by rehydration + lime Column 10 Row A As lime dose increased achievable solids concentration of pumpable liquid increased Column 5 Row B Partial heat drying following by rehydration, no lime Column 10 Row B As extent of heat drying increased from (34- 70%) achievable solids concentration of pumpable liquid increased. Column 5 Row C Partial air drying, rehydration with lime + heat Column 10 Row C As extend of air drying increased from (30->90%) achievable solids concentration of pumpable liquid increased. Column 5 Row D Partial heat drying, rehydration, with lime + heat Column 10 Row D As lime dose increased achievable solids concentration of pumpable liquid increased. Column 5 Row E Air drying, heat drying finish rehydration Column 5 Row F Air drying, heat drying finish rehydration with lime + heat Column 5 Row G Heat drying followed by rehydration +/− lime Column 10 Row G Liquid heating had no beneficial effect. Lime addition no initial beneficial effect. Y = yes N = no

OPERATIONAL DETAILS—PREFERRED EMBODIMENTS

[0130] Some examples of preferred procedures that embody the present technology will now be described.

[0131] The present Bio-Solids Cake treatment procedure can be controlled by monitoring/evaluating the pumpability of results until a required degree of pumpability has been achieved and then periodically re-hydrating and evaluating for a preferred degree of pumpability over a period of time.

Preferred Embodiments

[0132] The first 5 rows of Table 1, FIG. 1, (rows A, B, C1, C2, C4) show prior art examples for comparison.

[0133] The first preferred embodiment shown in FIG. 1, at rows F through Q, provides a process for converting 24% (no or limited free water) Biosolids Cake (BSC), a solid material, into a pumpable liquid, preferably with a viscosity of less than 6,000 cP, comprising: [0134] (a) firstly, thermally treating a mass of the Biosolids Cake by conventional heating, and, [0135] (b) secondly, drying the mass of Biosolids Cake (preferably without microwaves or added lime) beyond the free water point to a concentration of more than 35% Biosolids, preferably 35-37% Biosolids, to form a dehydrated {dried} Dried Biosolids Cake, and [0136] (c) thirdly, holding the drying Biosolids Cake mass at or above a certain drying temperature for the drying period, and, [0137] (d) fourthly, mixing, preferably thoroughly mixing, the dehydrated Dried Biosolids Cake with water to re-hydrate the Dried Biosolids Cake back to a re-hydrated mass (RDBSC) with a biosolids content higher than 24%, and, [0138] (e) fifthly, evaluating the resulting viscosity of the re-hydrated RDBSC for pumpability, preferably at less than 6,000 cP.

[0139] Further, this first embodiment may include additional repetitive extra steps each being: [0140] (a) the addition of supplemental water (biosolids remaining higher than 20%), and, [0141] (b) evaluating the resulting viscosity of the re-hydrated RDBSC for pumpability, preferably at less than 6,000 cP.

[0142] Details of the operation of the first embodiment are shown in FIG. 1 juxtaposed to the prior art processes which are detailed in rows A, B and C1 through C4, involving: [0143] (a) autoclaving at an elevated temperature (121° C.) and pressure but without drying/evaporation (Ref. A) and, [0144] (b) waterbath heating to 95° C. but without evaporation/drying (Ref B, C1, C2, C4).

[0145] In these prior art cases a mass of 24% Cake, col 4, was subjected to prolonged heating at 121 and 95 degrees Celsius (col 2) for 1.5 and 18 hours (col 3) respectively. In each case the resultant 24% (non-evaporated) Cake was diluted with water to 18 and 15% solids as noted in column 6 by mixing, col 7, and the viscosity evaluated as shown in col 8. As shown in this prior art, mixing water into the autoclaved and diluted at 18,069 cP Cake at 18%, by shaking, as in row A, produced an unpumpable material, col 8. Adding an aggressive mixing component, referred to and known as shearing/aggressive shearing (such as provided in a household blender for small batches), to the mixing reduced the 18% mix to pumpable at 3,743 cP. Shearing was accomplished by a Ninja Single Serve™ blender. By the next day the viscosity of this batch (ambient temperature) had increased on its own to 4,853 cP irreversibly.

[0146] The water bath prior art examples shown in rows B and C (95 degrees Celsius) for 18 hours (col 2 and 3) were diluted to 15% solids and sheared to reach a viscosity of about 4,000 cP.

[0147] As shown in row F, a first preferred embodiment, a 25.6% solid Cake material when heated to 97 C for 18 and 24 hours, with evaporation, reached biosolids solids contents of 35% and 40% respectively. Rehydration dilution by mixing process water back in to reduce the biosolids content back to 22.5% and 25% respectively, upon evaluation, produced a pumpable fluid at 4,847 cP and 5507 cP respectively, col 8, which viscosity was further reduced by mixing in further water (20% and 22.5%, col 10). In this example, pumpability at the expressed viscosity was achieved with no or only very minor reductions in the biosolids content of the initiating 25.6% material.

[0148] As shown in row G, a first preferred embodiment, the sample at 25.6% BS was heated on a hot plate with a temperature setting of 180 C for periods of 3 and 2 hours, col 3, respectively, to achieve an end Cake solids content of 40% and 50%, col 5. As in cols 5 and 6, this end Cake was rehydrated and diluted back to 20 and 25% by mixing and pumpability evaluated, col 8, at 5,039/cP and 5613/cP. In this case viscosity was shown as rising by the next day, with 1 sample rising to 27,000/cP, an unpumpable result. Further dilution to 22.5% again reduced the viscosity to pumpable ranges which held for the then-following next day, while continuing to rise. It is noted that hot plate heating resulted in wider variation in results which were alleviated in part by a spatula mixing.

[0149] As shown in rows H, P4.1, P4.2, U and Q, a first preferred embodiment, heating BSC of 24 and 25% solids at elevated oven temperatures for short periods (col 2 and 3) resulted in End Cake Solids of 45 to 70%, col 5. Upon dilution as shown in col 6 and mixing, col 7, in each case a readily pumpable viscosity was obtained, col 8. In the case of row P4,2 the low viscosity degraded by the next day, i.e. to 8,500 cP.

[0150] The individual elements of the first embodiment shown in FIG. 1 are displayed in FIG. 1a in a graphic manner particularly focused on the BS content of the resultant product when evaluated at 6,000 cP. In each case this resulted in a pumpable liquid with a viscosity of 6,000 cP along with a Solids Content of 20%, and 23% to as much as 33%. Rows A, B, and C1-C4 of the FIG. 1a table show the range of results for the prior art. Rows F to Q show the range of the results from the present procedure.

[0151] A second preferred embodiment is shown in FIG. 2 wherein the thermal drying is carried out by microwave heating. In this embodiment 24-25% Biosolids Cake were subjected to microwave heating to evaporate/reduce the initial Biosolids Cake to the Dried Cake Solids (DBSC) values shown in col 5. The hold times are set out in col 3. Dilution and re-hydration at ambient temperature (RDBSC) to the values shown in col 6 plus an aggressive mixing in a blender (small batch mixing) upon evaluation produced pumpable liquids as identified in col 8. Notably, the addition of a 3 hr/95 degrees Celsius heating step following the mixing, upon evaluation, yielded an unsatisfactory material with an unpumpable viscosity until greatly further diluted to 15% solids as shown in col 10.

[0152] The results shown in FIG. 2 are displayed graphically in FIG. 2a. FIG. 2a indicates the biosolids content of each liquid product which gives a viscosity of 6000 cP. The additional heating step after mixing upon evaluation degraded all of the results.

[0153] A third preferred embodiment provides a controlled process as in the first embodiment with the additional steps of the addition of a hydrolyzing agent, preferably time, to the re-watering step plus a period of heated incubation after the hydrolyzing agent (lime) is mixed in. Details of the operation of the third embodiment are shown in FIG. 3.

[0154] In row J of FIG. 3, 450 g of 24% Biosolids Cake is held in a convection oven set at 180-200 degrees Celsius for a period of 3.5 hours (col 3) with the resultant drying leaving a Dried Biosolids Cake with After Cooking Solids content (col 4) of 50%. As shown in cell J1-4 time in the form of Cal85™ (85% calcium oxide supplied by Carmeuse Lime, Ingersoll, Ontario) is added to the Dried Biosolids Cake in the amounts specified as 1, 2, 3, and 4% (ie 1-4 g per 100 g of 24% original Biosolids Cake (BSC). As shown in col 6 the Dried Biosolids Cake material of col 4, 5 is rewatered (re-hydrated) by dilution to a biosolids content of 30% and 40% as shown and the RDBSC material mixed for 1 minute. An additional step of thermal incubation, col 8, is included as 3 hours at 95 degrees Celsius. Evaluation of resulting viscosity showed unpumpable initial viscosities (col 9) for the 50%/1%/30% and the 50%/2%/30%, with a significant next day increase in the later. Further rewatering of the 50%/2%/30% (after cook solids/Cal85/Diluted BS) material to 29% biosolids content resulted upon evaluation in the pumpable liquid of the invention upon completion. This remained liquid through the next day.

[0155] In row K of FIG. 3 450 Grams of 25.6% Biosolids Cake was dried in a convection oven set at 180-200 degrees C. for variable periods of 1.5 to 3.5 hours to dry the Biosolids Cake to 30% through 40% biosolids, see col 4. Adding 3% Cal 85 (col 5), rewatering to 28% by dilution, mixing for 1 minute to form a RDBSC and incubation for 3 hours at 95 degrees Celsius produces viscosity evaluations as shown in cell K,9 as unpumpable (100,000/cP) for the 30% after-cook-solids-material and pumpable for the higher after-cook-biosolids content RDBSC materials. The pumpable evaluations remained through the next day (col 10).

[0156] In row M of FIG. 3 the same amount of 450 grams of 25.6% BSC was held at the drying temperature of 180-200 degrees Celsius for a drying time ranging between 2 to 4.5 hours (col 3) to produce an Dried Biosolids Cake with After-Cook-Solids content ranging between 40% and 65% (col 4). Processing with the addition of Cat 85 time, dilution to 32.5% and 35% Solids Content, mixing for 1 minute and incubation cooking for 2.5 hours at 99 degrees C., upon evaluation, produced a next day viscosity of 6,0000 or less for each After Cook content, col 10.

[0157] In the FIG. 3 table (3) it is noted that columns 6, 11, 14, 16 refer to biosolids content. Total solids content would be higher due to the amount of Cal 85 added. Further, FIG. 3 shows aggressive mixing for 1 minute which describes mixing the material by breaking apart solid particles, Lumps or pieces. For softer materials a simple mixing is sufficient. For the harder materials a more aggressive mixing is required to break down the hard component as by milling after adding back water. Wet or dry milling prior to adding back water are other options. The objective is to reduce particle sizes of solid particles produced through the drying step and not changing the properties of the Biosolids Cake in the material by that action alone. As the dryer materials become harder and more brittle, some breakup of the harder particles is required for efficient processing.

[0158] Further processing steps of water dilution on the next day upon evaluation further reduced the viscosity each time as shown in columns 11 through 17. In summary, in each of the row M cases an initial Biosolids Cake having a biosolids content of 25.6%, a solid, has been rendered pumpable at an elevated biosolids content and very pumpable, i.e low viscosity, at its original biosolids concentration of 25%.

[0159] In row V a 400 g mass of 25.6% BSC was heated and dried in a convection oven set at 200 degrees Celsius at atmospheric pressure for 3.5 hours to produce a Dried Biosolids Cake with After Cook Solids content of 50%. Mixing and diluting in the presence of added Cal85 lime at 2, 3 and 4% with dilution to the equivalent of 35% biosolids content to form a RDBSC plus incubation at 99 degrees Celsius for 2.5 hours, upon evaluation, produced a pumpable liquid at less than 6,000 cP upon the further steps of dilution to 30% and 28%, plus evaluation, as shown in columns 13 through 15 (ND=next day value).

[0160] A graphical summary of the operation of the third preferred embodiment is shown in FIG. 3a. FIG. 3a indicates the biosolids content of each Liquid product which gives a viscosity of 6000 cP.

[0161] A fourth preferred embodiment provides a controlled process as in the third embodiment wherein heating is provided by microwave energy and is detailed in the table shown FIG. 4 (table 4).

[0162] In this embodiment, S1, 400 grams of Biosolids Cake at 24% was microwaved for 5 minutes to a dry condition (approximate solids content of 47% based on the 24% Biosolids Cake figure), i.e. dried by ½ of the solids content. Addition of Cal85 time at 2.81% (based on the 24% Biosolids figures), dilution to a biosolids content of 20%, mixing for 2 minutes and incubation for 1 hour at 95 degrees Celsius resulted in a pumpable liquid with an initial viscosity of 4037 cP, which is noted to rise over the course of the next day but still pumpable.

[0163] In this embodiment, S2, 350 grams of biosolids at 25% was microwaved for 12 minutes to a solids content of 47% based on the 24% BSC figure, i.e dried by approximately ½ of the solids content. Addition of Cal85 time at 3% (based on the 25% BS figures), dilution to a biosolids content of 22.5%, mixing for 1 minute and incubation for 1 hour at 95 degree Celsius resulted in a barely pumpable liquid with an initial viscosity of 9000 cP. Further dilution to a biosolids content of 20% reduced the viscosity to 4415 cP.

[0164] In this embodiment, S4, 416 and 500 grams respectively of Biosolids Cake at 24% was microwaved for 18 minutes to a dry condition (approximate solids content of 47% based on the 24% Biosolids Cake figure), i.e. dried by ½ of the solids content. Addition of Cal85 lime at 4% (based on the 24% biosolids figures), dilution to a biosolids content of 25%, a more aggressive mixing as by a blender in a blender for 1 minute and incubation for 3 hours at 95 degree Celsius resulted in a pumpable liquid with an initial viscosity of 2010 and 2310 cP, respectively, which is noted to rise over the course of the next day but stilt pumpable.

[0165] In this embodiment, S52 and S6, 400 grams of BSC at 24% was microwaved for 13 minutes to a solids content of 50% based on the 24% BSC figure, ie dried by ½ of the solids content. Addition of Cal85 lime at 5% (based on the 24% BS figures), dilution to a biosolids content of 25%, a more aggressive mixing as by a blender in a blender for 1 minute and incubation for 3 hours at 95 degree Celsius resulted in a pumpable liquid with an variable initial viscosity of between 2771 cP and 6849 cP.

[0166] At tower temperatures and times this preferred embodiment of the process may require original (first) re-watering to a biosolids level lower than the original biosolids level but in any event at biosolids content of 20% or more.

[0167] A graphical summary of the operation of the fourth preferred embodiment is shown in FIG. 4a (table 4a). FIG. 4a indicates the biosolids content of each liquid product which gives a viscosity of 6000/cP.

[0168] FIG. 5 (table 5) shows the fifth embodiment of the invention in graphical format for non-thermally supported air drying (by means of a Salton™ air dryer) at above ambient temperatures without and with a lime addition. FIG. 5 indicates the biosolids content of each liquid product which gives a viscosity of 6000/cP.

[0169] In each case a Biosolids Cake sample was air-dried at 35 C for 18 hours to dry from Biosolids Cake 24% through to a Dried Biosolids Cake at 67% and 59% as shown in column 5. Re-watering dilution back to 24% biosolids for a RDBSC plus aggressive mixing (as by a blender) for 30 seconds, for the cases of both Cal85 addition or not, column 7, upon evaluation, provided a range of BS content for 6,000/cP pumpable liquid ranging from 21% through 32% depending on incubation times of 0 (no incubation) and 95 degrees Celsius for 3 hours and presence or absence of Cal85 in the mix, see column 9.

[0170] FIG. 6 (table 6) shows a variation on the non-thermal drying fifth embodiment of FIG. 5 by means of a dehumidifier rated at 70p (pints)/per 24 hours period. The dehumidifier is not providing significant heat to the process above ambient. In this embodiment 500 gram samples (col BB) of 25% BSC were dried to produce Dried Biosolids Cake end-of-drying solids contents ranging in the DBSC from 30-90% as shown in col CC. In each case re-watering by dilution to a RDBSC with a biosolids content of 20-30% plus the addition of 4% Cal85 and an aggressive mixing (as by a small batch blender) from 60-90 seconds plus the additional step of incubation after mixing for 3 hours at 95 degrees Celsius, upon evaluation, produced a pumpable liquid at 6,000 cP ranging from 20% biosolids through to 32% solids. It is noted that the mixing time component shown in column FF was increased from 60-90 seconds with the increasing dryness of the material itself in order to achieve particle breakdown and mixing. Air drying as with the fifth preferred embodiment provides the controlled process of the first and second embodiments at a lower temperature, preferably 35° C., but requires a much longer hold time requirement, such as 18 hours, to achieve the evaluated results.

[0171] FIG. 7 (table 9) provides another embodiment with a combination drying step. As shown in column 1, 500 and 650 gram samples of 25% Biosolids Cake were (dried) dehumidified to 50-71.4% BS as per column 2. Column 2 shows the final weight and % biosolids content upon completion of this dehumidification step. At col 2a the amount of water removed by dehumidification is also specified.

[0172] The second step in the drying process in this embodiment was provided by thermal drying which dried the sample weights further to 139 and 180 gram weights respectively (as set out in column 3) for a 90% biosolids content by removing the amount of water set out in column 3a from the sample.

[0173] Batch rehydration by mixed-in water addition to the levels shown in column 4 (35, 40 and 45%) with each of Cal85 lime addition and incubation for 3 hours at 95 degrees Celsius resulted in evaluation levels as pumpable liquids with the viscosities shown in column 8. Aggressive intermixing of the reconstituting water, the cal85 and the dried Biosolids Cake (90%) was included in the process by mixing for 1-2 minutes as shown in col 6. A further included step of incubation for 3 hours at 95 degrees Celsius (Column 7) following or together with the intermixing steps showed evaluations with improved pumpability as shown in col 8.

[0174] FIG. 8 (table 10) provides another embodiment. A 90% DBSC mass of material was prepared from a 25% Biosolids Cake by air drying using a food air dryer. Ninety grams of the Dried Biosolids. Cake 90% material, being hard and somewhat brittle, was rough ground in a Ninja™ single serve homogenizer (approx 10 seconds) and then processed in accordance with FIG. 8 (table 10) (col AA-H). In each case re-hydration water was added in the amount of 90 grams to form the RDBSC. As set out in col CC an amount of lime, being Ca(OH)2, was added. This resulted in a mix with a BS and a TS (total solids) concentration as set out in columns DD and EE, when mixed with a auger-style hand mixer for about 30 seconds, column FF. Evaluation of viscosity confirmed a pumpable liquid with gel like characteristics at 3,700 cP or less, well within the appropriate range for use in an industrial process. A further step taken the next day by the addition of small amounts of additional water to further dilute or re-hydrate the mix improved the evaluated viscosity in all but 1 instance. In case number 5 the initial mixed RDBSC showed signs of some settling out. While an approximate viscosity of 180 was measured and assigned, viscosity drops during measuring as settling out progresses.

[0175] FIG. 9 (Table 11) presents a summary of at least some process options involving a dehydration step to produce high biosolids concentration pumpable liquids or slurries at least partly based on the foregoing examples. As indicated in columns 1-2, the drying step may involve air or heat drying or a combination thereof. Heat drying, as understood here, includes microwave drying. As indicated in columns 3, 4, the aqueous re-hydration step may or may not include addition of lime or other hydrolysis agents and/or a liquid heating step. Column 5 provides a short process description for the process combination represented by each row entry. Column 6 shows the drying extent or range used in the dehydration step (by air or heat) for the process represented in each row. In rows E, E where a combination of air and heat drying was used the extents of dehydration by air and heat are noted. Columns 7 describes the product consistency in terms of a pumpable liquid or slurry. Columns 8/9 describe ranges of biosolids concentrations and total solids concentrations obtained as pumpable liquids in the process represented by each row. The difference between biosolids and total solids concentration in a particular product is due to added lime.

[0176] Further embodiments include the product and procedure wherein:

[0177] at least part of the first step is carried out under vacuum, and,

[0178] the first step consists of a non-heat or unheated drying step followed by a heated drying step. In this case the unheated drying may be carried out by air drying at ambient temperature and pressure, dehumidication, and drying with only slightly heated sources. and

[0179] any alkali is sufficient to maintain the mixture at a pH of greater than 11, 11.5 and/or 12 during the thermal treatment first step. and

[0180] where the alkali dose rate is greater than 20 Kg time (CaO) and/or preferably 30-40 Kg per Metric Ton biosolids having a solids concentration of 24% W/W. and

[0181] the alkali does rate for treatment of biosolids cake is proportional to cake solids concentration. and

[0182] sources of alkalis and other than lime are used at dose rates based on their OH equivalence to time. and

[0183] the first drying step is replaced by acquisition of previously dried biosolids products and pellets. This dried material is processed in steps (b) and (c). and

[0184] a preservative other than alkali is added to the product to inhibit microbial growth at any one or more of;

[0185] (1) first step drying,

[0186] (2) second re-hydration step

[0187] (3) after re-hydration.

[0188] The scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations, and/or additions to the present subject matter as would be readily apparent to a person skilled in the art.