Process to stabilize bioorganic, raw or treated wastewater sludge

• US 5,417,861 A
• Filed: 12/21/1993
• Issued: 05/23/1995
• Est. Priority Date: 11/30/1990
• Status: Expired due to Term

• Current Assignee: Medical College of Ohio
• Original Assignee: N-Viro International Corporation
• Inventors: Burnham, Jeffrey C.
• Primary Examiner(s): Hruskoci, Peter A.
• Application Number:
  US08/170,705
• Time in Patent Office: 518 Days
• Field of Search: 71/9, 71/12, 71/13, 71/21, 71/22, 71/63, 210/609, 210/613, 210/631, 210/710, 210/713, 210/751, 210/752, 210/764, 210/916, 210/667
• US Class Current: 210/609
• CPC Class Codes: C02F 1/281 using inorganic sorbents
• CPC Class Codes: C02F 1/586 by removing ammoniacal nitrogen for biological methods C02F3/00
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 11/12 by de-watering, drying or thickening
• CPC Class Codes: C02F 11/18 by thermal conditioning by pyrolysis C02F11/10
• CPC Class Codes: C05D 3/00 Calcareous fertilisers C05D7/00 takes precedence
• CPC Class Codes: C05D 9/00 Other inorganic fertilisers
• CPC Class Codes: C05F 17/40 Treatment of liquids or slurries
• CPC Class Codes: C05F 7/00 Fertilisers from waste water, sewage sludge, sea slime, ooze or similar masses
• CPC Class Codes: Y02A 40/20 Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02P 20/145 the feedstock being materials of biological origin
• CPC Class Codes: Y02W 30/40 Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse
• CPC Class Codes: Y10S 210/916 Odor, e.g. including control or abatement

Abstract

A method for treating bioorganic or raw or treated wastewater sludge so that a stability based upon achieving a significant microbial population, conductivity level and percent solids, is developed rapidly, is provided for indefinitely and is independent of climatic conditions. A dewatered sludge that has not been treated (i.e., raw) or a sludge that has been treated to a PSRP level or a sludge that has been treated to a PFRP level, i.e., pasteurized or sterilized sludge when still in a wet condition, i.e., between 12%-30% solids, or when in a dry condition, i.e., between 30-60% solids, is mixed with alkaline adsorptive materials to reduce odor, to increase the percent solids and to facilitate granulation, is adjusted to a mildly alkaline pH, and is adjusted to an ionic conductivity which will allow the sludge to mature rapidly when seeded with a beneficiating microbial flora. This process will reduce the pH or a high alkaline treated sludge, e.g., often above pH 12, to a physiological pH of between 7 and 9.5 or will raise the pH of a treated acid sludge to a similar range so that microbial activity can proceed to facilitate stability. Heat may be applied to the mixture to accelerate the carbonation and aid the overall drying process. The granular product, substantially due to its active microbial population, is useful as an agricultural product and topsoil blend.

Claims

1. A method of treating bioorganic or raw or treated wastewater sludge to provide a stable product for use as a beneficial soil or fertilizer for agricultural lands comprising the steps of:

treating the bioorganic or wastewater sludge with a high adsorbent material selected from the group consisting of cement kiln dust, lime kiln dust, fluidized bed ash, lime injection multistage burner ash, dry sulfur scrubbing residue, slag fines, pulverized calcium carbonate, fly ash, gypsum or a combination thereof to provide a sludge mixture, such that odorant sludge organics and inorganics are bound to the adsorbent particles,

adjusting the pH of the sludge mixture such that it is in the range of 7.0-9.5,

adjusting the conductivity of the sludge mixture such that it is raised to between 5 and 30 mmhos,

adjusting the solids to a minimum of 50% and

adjusting the microflora content within the range of about 10⁶ to 10¹⁰ aerobic bacteria and about 10⁴ to 10⁷ fungi per gram soil solids, if necessary because of the absence of a sufficient microflora, with a soil, a sludge product containing microflora, a microbial culture or mixture thereof, by introducing the microflora of the soil, the sludge product or the microbial culture directly into the sludge mixture; and

thereafter maintaining the pH range and conductivity range for a time sufficient to allow the microbial population of the sludge under the influence of the conductivity range to establish and to commence catabolism of the organics present in the sludge mixture, to continue the odor reduction initially begun by the addition of the adsorptive material, to prevent regrowth of pathogenic organisms, and to continue to carbonate any residual calcium hydroxide or calcium oxide components to form said stable product.

2. The method according to claim 1 wherein the sequence of steps comprises:

(a) initially treating the sludge to achieve dewatering;

(b) treating the sludge for pathogen reduction;

(c) adjusting the sludge mixture for pH;

(d) adjusting the sludge mixture for conductivity;

(e) adjusting the solids contents to at least about 50%;

(f) adjusting the microflora content by introducing directly into the sludge a microflora from natural soil, or mixture sludge product containing microflora or a microbial culture into the sludge mixture;

(g) treating the sludge mixture with activated carbon for additional odor control; and

(h) allowing the sludge mixture to mature in static pile to form said stable product.

3. The method set forth in claim 2 including the step of treating the sludge mixture with activated carbon for additional odor control and allowing the sludge mixture to mature in static pile prior to forming said stable product.

4. The method set forth in claim 1 wherein the sludge is raw primary sludge.

5. The method set forth in claim 1 wherein the sludge has been treated to reduce pathogens.

6. The method according to claim 5 wherein the sludge has been initially treated by sterilization.

7. The method according to claim 6 wherein the sludge has been initially treated as follows:

wastewater sludge containing odor, animal viruses, pathogenic bacteria, and parasites is treated to provide a fertilizer for agricultural lands which can be applied directly to the lands which consists essentially of the following steps;

mixing said sludge with at least one material selected from the group consisting of lime, cement kiln dust and lime kiln dust to form a mixture,

wherein the amount of added material mixed with said sludge being sufficient to raise the pH of said mixture to 12 and above for at least one day;

and drying said mixture to produce a granular material,

the amount of added material mixed with said sludge and the length of time of drying being sufficient to reduce significantly offensive odor of the sludge to a level that is tolerable;

to reduce animal viruses therein to less than one plaque forming unit per 100 ml of said sludge;

to reduce pathogenic bacterial therein no less than three colony forming units per 100 ml of said sludge;

to reduce parasites therein to less than one viable egg per 100 ml of said sludge;

to reduce vector attraction to said sludge; and

to prevent significant regrowth of the pathogenic microorganisms.

8. The method according to claim 1 wherein the sludge has been initially treated by sterilization.

9. The method according to claim 8 wherein the material added to raise the conductivity while maintaining an alkaline pH is selected from the group consisting of cement kiln dust, lime kiln dust, fluidized bed ash, dry sulfur scrubbing residue, slag fines, pulverized calcium carbonate, fly ash, gypsum, sodium chloride, potassium chloride, calcium chloride, ammonium sulfate, or a combination thereof.

10. The method according to claim 1 wherein the adsorbent material is added to maintain the pH and to adsorb sludge organics and inorganics and to aid in granulation and is selected from the group consisting of cement kiln dust, lime kiln dust, fluidized bed ash, lime injected multistage burner ash, dry sulfur scrubbing residue, slag fines, pulverized calcium carbonate, fly ash, gypsum or a combination thereof.

11. The method according to claim 1 wherein the material added to raise the conductivity while maintaining an alkaline pH is selected from the group of adsorbent materials consisting of cement kiln dust, lime kiln dust, fluidized bed ash, lime injected multistage burner ash, dry sulfur scrubbing residue, slag fines, pulverized calcium carbonate, fly ash, gypsum, or a combination thereof.

12. The method according to any one of claims 1 and 8 wherein the pH reduction is wholly or partly effected by addition of one or more of the following materials:

alum, alum sludge, concentrated acids comprising phosphoric or nitric or hydrochloric, yard waste and agricultural soil or dredgings containing clay minerals containing aluminum ions, carbonates, bicarbonates and phosphates to affect the buffering of the sludge mixture to the required pH range.

13. The method set forth in claim 12 wherein pH reduction and carbonation are enhanced by heating input soil, air or CO₂ containing gas immediately prior to its contacting the sludge mixture.

14. The method according to claim 1 wherein the carbonation is wholly or partly effected by addition of a carbon dioxide containing gas selected from the group consisting of carbon dioxide gas, flue gas or emission gases resulting from the combustion of methane or other organic material wherein the carbon dioxide is a major constituent of said flue gas, or emission gases.

15. The method according to claim 14 including the step of heating the sludge mixture to 52°

C. to 62°

C. during CO₂ exposure.

16. The method according to claim 1 wherein the carbonation is effected by an air which contains 0.03% CO₂.

17. The method according to claim 1 wherein the sludge comprises an acid sludge which is made alkaline within the range of pH 7.0 to 9.5 by the addition of a material selected from the group consisting of cement kiln dust, lime kiln dust, calcium oxide, calcium hydroxide, fluidized bed ash, dry sulfur scrubbing residue, slag fines, bicarbonate pulverized calcium carbonate, fly ash, gypsum.

18. The method according to claim 1 wherein the microflora added to the sludge mixture includes bacteria produced in controlled cultures and are selected from indigenous bacterial and fungal microflora of agricultural soils.

19. The method according to claim 18 wherein the bacteria added includes members of the actinomycete class of bacteria.

20. The method according to claim 18 wherein the bacteria added to the sludge mixture are obtained from a stored sludge product resulting from the method.

21. The method according to claim 1 wherein the pH is adjusted such that ammonia emissions are reduced from that caused by high alkaline pH of over 10 thereby reducing the odor of the sludge product and increasing the agronomic value of the product as a nitrogen containing fertilizer.

22. A method according to claim 1 wherein the sludge is heated to a temperature of 85°

C. or above for at least several minutes.

23. The method set forth in claim 1 by which the product of the method is blended with yard waste at a rate of 10 percent to 25 percent of the wet weight of the yard waste and subjected to composting in order to reduce the odors that emanate from the composting.

24. The method set forth in claim 1 wherein the sludge is initially treated for pathogen control by heating or radiation.

25. The method set forth in claim 1 wherein the sludge is initially treated with carbon dioxide.

26. The method set forth in claim 1 wherein the sludge is a bioorganic sludge.

27. The method set forth in claim 1 wherein the sludge is an organic sludge.