WO2003035554A2 - Improved methods, processes and apparatus for bio-solids recycling and the product of bio-solids from such methods, processes and apparatus - Google Patents

Abstract

A biosolids treatment process and system are described. The process includes a thermophilic digestion step (1), a methane generation step (2), and a mesophilic disgestion step (3). Optionally, the process also includes a first stage solids dewatering step (4). Optionally, the process also includes an evaporative drying step (5).

Description

PATENT SPECIFICATION

TITLE: IMPROVED METHODS, PROCESSES AND APPARATUS FOR BIO-SOLIDS RECYCLING AND THE PRODUCT OF BIO-SOLIDS FROM SUCH METHODS, PROCESSES AND APPARATUS

INVENTORS: RICHARD A. HAASE

EILEEN TUROWSKI TAYLOR

RELATED APPLICATION DATA

This application claims priority of U.S. Provisional Patent Application Serial No. 60/315,464 filed 08/28/01.

Field of the Invention

In the field of water treatment, this invention relates to improved methods, processes and apparatus for sludge, separated solids and bio-solids treatment, as well as the bio-solids from these improved methods, processes and apparatus. This invention relates to economical methods, processes and apparatus for preparing Class "A" aqueous solids wherein dewatering costs and energy costs are efficiently managed; and wherein the solids product has reduced ammonia and sulfide odor; and wherein the percent solids in the aqueous product may vary from approximately 3 percent to approximately 90 percent.

Background of the Invention and Description of the Prior Art

Since the inception of the Clean Water Act of 1974, municipal and industrial wastewater treatment facilities have had to dispose of solids separated from water during treatment. The aqueous solution of these solids is often termed sludge; however, for clarity, the term aqueous solids is used wherein solids are aqueous primary solids and/or aqueous secondary solids. Primary solids are defined as aqueous solids that are separated from the treated water in primary treatment in any treatment system; primary treatment physically separates aqueous solids from the treated water, usually in a clarifier or a dissolved air flotation device. Secondary solids, bio-solids, are defined as aqueous solids that are separated from the treated water in secondary treatment; secondary treatment is biological treatment, usually in a waste water treatment plant. These aqueous separated solids, primary solids and/or bio-solids, are normally sent to digestion. In digestion, the solids volume is reduced by bacteria that consume, digest, the separated aqueous solids (SS). The performance of digestion is determined by the reduction of Volatiles in the SS. Volatiles are defined in the laboratory, as the solids remaining on a filter from a filtered sample after those filtered solids are heated to approximately 102 °C, yet do not remain after a second heating to approximately 600 °C. This mass measurement difference is a definition of the heavier organic content of the filter sample and is therefore an estimation of the biological content and organic biological food content of the solids in an aqueous sample. In a messophillic digestion system, the percent Volatiles reduction is normally 40 to 50 percent. In thermophillic digestion, the percent Volatiles reduction can be 55 to 65 percent. Messophiles are defined as bacteria that operate between the temperatures of approximately 40 and 105 °F. Thermophiles are defined as bacteria that operate between the temperatures of approximately 105 and 160 °F. To manage transportation and disposal costs, nearly all wastewater treatment facilities prefer to reduce the Volatiles content of the digested solids as much as is economically practical.

After digestion, the final digested solids product (Digested Solids) must be properly disposed of. Disposal of the Digested Solids (DS) is normally accomplished by either land application or by disposal in a landfill. To minimize the handling and transportation expense of the DS, the water content of the DS is normally reduced from approximately 94 percent, in digestion, to approximately 75 percent by chemical and mechanical separation utilizing a belt press, centrifuge or other type device. To reduce the water content further many facilities incorporate heated air-drying, evaporative air- drying, or any combination thereof with mechanical means. A drier product is required if the DS is stored for an extended time. DS placed in storage having a moisture content of greater than approximately 15 percent have the capability of spontaneous combustion. Many facilities utilize this biochemistry to heat treat the DS via composting to reduce the pathogen content of the DS. Municipal wastewaters, and usually industrial wastewaters, generally contain four types of human pathogenic organisms: bacteria, viruses, protozoa and helminthes (parasitic worms). The actual species and density of pathogens contained in the raw wastewater will depend on the health of the particular community and/or the inclusion of significant rainwater runoff from animal sources. The level of pathogens contained in the untreated DS will depend on the flow scheme of the collection system and the type of wastewater treatment. For example, since pathogens are primarily associated with insoluble solids (non-volatile solids), untreated primary solids have a higher density of pathogens than the incoming wastewater. Since pathogens only present a danger to humans and animals through physical contact, one important aspect in land application of DS is to minimize, if not eliminate, the potential for pathogen transport. Minimization of pathogen transport is accomplished through reduction of Vector attraction. Vectors are any living organisms capable of transmitting a pathogen from one organism to another either directly or indirectly by playing a key role in the life cycle of the pathogens. Vectors that are specifically related to DS could most likely include birds, rodents and insects. The majority of vector attraction substances contained in the DS are in the form of Volatiles. If left unstabilized,

Volatiles will degrade, produce odor and attract pathogen-carrying Vectors.

On February 19, 1993, the National Sewage Sludge Use and Disposal Regulations (Chapter 40 Code of Federal Regulations Part 503 and commonly referred to as the 503 Regulations) were published in the Federal Register. The 503 regulations define DS treatment methods that transform DS into Class "A" DS; Class "A" are DS free of pathogens and Vector attraction. In essence, the Regulation establishes several categories in terms of stabilization, pathogenic content, beneficial reuse and disposal practices for all land-applied DS. These regulations set forth chemical methods, temperature methods, methods that include a combination of chemical and temperature, as well as other methods, including composting to treat DS for land application. Since 1993, experience has taught that the most reliable methods of Vector reduction are the temperature methods and/or chemical methods. The temperature methods include direct heating and thermophillic digestion.

However, the direct heating and chemical methods are rather expensive to implement. The chemical methods require raising the pH of the DS to a minimum of 12 utilizing an oxidizer, typically lime is used, which is expensive, further creating very alkaline DS, which is not a good fertilizer for land application. The temperature methods require heating the DS to a minimum of 50 °C (122 °F) for a specified period of time that is dependent on the amount of temperature above 50 °C. This is expensive and energy consumptive. The most economical method of disinfection involves Thermophillic Digestion (TD). TD is inexpensive from the standpoint of the cost of disinfection. Energy cost is minimal due to the thermophillic process itself. In the case of Aerobic TD (ATAD), digestion occurs so exothermically that once initiated, the temperature is self- sustaining. In the case of Anaerobic TD (ATD), the hydrocarbon gas produced in digestion can be sent to fire a boiler producing steam to maintain the required 50 °C temperature. Moreover, as mentioned previously, a side benefit to Vector reduction is an increase in the reduction of Volatiles by TD. However, ATAD, ATD and TDS have significant issues in relation to odor and to dewatering cost. The dewatering cost of TD Solids (TDS) is much more than that of Messophillic Digested Solids (MDS) due to the nature of thermophillic bacteria as compared to messophillic bacteria. While messophillic bacteria naturally secrete tackifying polysaccharides to initiate floe formation, thermophiles do not. This biological difference can make the dewatering cost of TDS expensive and render the process of TD uneconomical. Previous work can be referenced in U.S. Patent Nos. 5,846,435 and 5,906,750. However, these patents do not incorporate a means of controlling the odor of the TDS. TDS have strong ammonia and sulfide odors that are objectionable and that attract Vectors. Further work is documented in U.S. Patent 6,083,404, wherein a three component system of dewatering is presented. This patent has no method for controlling sulfide or ammonia odor

Bacteria, Volatiles, contain a significant amount of protein and lipoic acids. A very large portion of the bacteria cell contains the proteins, DNA and RNA sequences, for cell reproduction. Significant portions of these proteins are amino acids. Lipoic acids contain sulfur. Amino acids, DNA and RNA contain nitrogen. As a result, the digestion of Volatiles releases ammonia and sulfide(s). While sulfidic odors are present in both MDS and in TDS, strong and objectionable sulfide and ammonia odors have been specifically associated with TDS. The digestion process itself is an oxidation process of the volatiles. As such, the release of ammonia and sulfide(s) biologically occurs. However, it does appear that the MD process uses a much larger portion of the ammonia as a nutrient and/or as in a conversion to nitrogen gas than does the TD process. Monitoring of ammonia nitrogen levels in TDS has found the ammonia to measure as high as 1500 to over 2000 ppm. At such levels, most of the ammonium hydroxide has converted to ammonia gas. Ammonia gas is known to be toxic at these concentrations to all messophillic organisms. Ammonia gas in the final DS can make land application of the DS objectionable; ammonia gas in the TD process can make the process itself objectionable. Further, since both the MD and the TD process create sulfide(s), the biological conversion of ammonia to nitrates, much less to nitrogen, is impractical. Sulfide(s), hydrogen sulfide and sulfur dioxide, are toxic to nitrifying bacteria. Having sulfide toxicity, MD cannot perform nitrification to remove ammonia odor from the DS, whether the DS be TDS or MDS. Further Nitrifiers, nitrosonomas and nitrobactor, are messophillic bacteria, which cannot live above 105 °F; therefore, nitrification is impractical in TD.

Previous work in thermophillic digestion has been done by Ort, U.S. Patent No. 4,040,953, which actually suggests that thermophillic digestion has certain advantages including a lower solids retention time and more readily dewatering characteristics; further, there is no discussion by Ort that thermophillic digestion would have odor issues, whether ammonia or sulfide(s). U.S. Patent No. 5,492,624 presents the ATAD; there is no mention of dewatering or odor issues in relation to thermophillic digestion or in relation to the new ATAD. US Patent 6,203,701 presents an ATAD process and apparatus; again odor and dewatering issues are not discussed. Literature published in November of 2001 indicates a lack of understanding for both the source of thermophillic digestion odors and for a solution. "The Future of Solids Treatment?" Water, Environment and Technology, Vol. 12, No. 11 , pp. 35-39. This literature documents that there are odor issues with thermophillic bio-solids; there is no understanding of the source of the odor or any anticipated solution. Literature published in May of 2001 reviews the requirements for Class A bio-solids per the 503 regulations, yet has no discussion of odor or dewatering. "Is It Really Class A?" Water Environment and Technology, Vol. 13, No. 5, pp. 39-42. Literature published in February of 2001 indicates iron media as a method of odor control, yet there is no discussion of bio-solids s odor. Water Environment and Technology, Vol. 13, No. 2, pp. 38-44. This invention identifies sulfide(s) as both an odor component and as a component to inhibit nitrification, thereby limiting nitrification. Previous work in U.S. Patent 6,136,193 identifies thiobacillus and thiobacillus denitrificanus as biological cultures that will remove sulfide(s) from sulfide laden aqueous systems. While this patent does recommend the use of thiobacillus with other biological cultures, this patent has no discussion of methods to treat thermophiles and has no method of dewatering thermophiles.

Concentrations of sulfide(s) as low as 5 ppm are known to inhibit nitrification and to begin killing nitrosonomas. Concentrations of sulfide(s) as low as 3 ppm are inhibitory to nitrosonomas. As referenced in U.S. Patent No. 5,705,072, the inhibitory and lethal aspects of sulfide(s) to nitrosonomas can be controlled by either oxidation of the sulfide(s) to sulfate or with the addition of at least one of thiobacillus and/or thiobacillus denitrificanus. However, this patent does not provide for dewatering of TDS. Further, there is no oxygen or available electron donor in the ATD; therefore, a method is needed to control sulfide(s) and ammonia in the TDS from ATD. Nitrifiers cannot live in an anaerobic environment. Every pound of ammonia converted to nitrates by nitrification, requires approximately four pounds of oxygen. In addition, thiobacillus and thiobacillus denitrificanus are messophiles; therefore, both the ATAD and the ATD operate at temperatures above the operating range of thiobacillus, thiobacillus denitrificanus, nitrosonomas and nitrobactor.

Ammonia Nitrification

For treating the ammonia content of wastewaters, certain aerobic messophillic autotrophic microorganisms can oxidize ammonia to nitrite, which can be further microbially oxidized to nitrate. Said reaction sequence is known as Nitrification. Nitrification reduces the total ammonia-nitrogen content of the wastewater. Ammonia is removed from the wastewater by bacterial oxidation of ammonia to nitrate (N0₃), using bacteria that metabolize nitrogen. Nitrification is carried out by a limited number of bacterial species and under restricted conditions including a narrow range of pH and temperature and dissolved oxygen levels, along with reduced Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) levels. Atmospheric oxygen is used as the oxidizing agent; however, pure oxygen can be used. Nitrifying bacteria grow slowly and nitrogen oxidation is energy poor in relation to carbon oxidation. In addition, nitrification is inhibited by the presence of a large number of compounds, including organic ammonium compounds, sulfide(s) and the nitrite ion (N0₂). Furthermore, nitrifying bacteria subsist only under aerobic conditions and require inorganic carbon (CO3^", such as from CaO or CaOH, or HCO₃ ^', such as from NaHC0₃) for growth. The sequence of intermediates is:

NH₄OH + 20₂ "itrosonoma_{S> N}0₂ ^2" + 0₂ ^nitrobactor> NO^3'

Approximately 4 pounds of oxygen and approximately 6 pounds of carbonate and/or bicarbonate are required for every pound of ammonia.

It may be worthwhile to note that the term "ammonia" is used in the art to describe "ammonia as a contaminant in industrial wastewater". "Ammonia" refers, in this art, to the NH ⁺ ion that exists in aqueous solution and that is acted on microbially, with the following equilibrium existing in the aqueous solution:

NH₄ ⁺ + OH^' — ► NH₃ + H₂0

As the total ammonia concentration approaches 150 ppm and the pH approaches 8.0, this reaction is driven to the right. At ammonia concentrations approximately above 350 ppm and the pH approximately above 8.0, ammonia gas (NH₃) toxicity exists in the water. In addition to being toxic, ammonia gas is volatile, having a significant vapor pressure.

The Rancidity Process

The most practical recycle application of DS, whether MDS or TDS, is land application as a fertilizer. Further, most governmental agencies are requiring a Class "A" product for land application of DS. Upon application as a fertilizer, the DS, MDS or

ADS, will decompose into fertilizer naturally. Bio-Solids are a natural organic fertilizer.

However, prior to land application, DS can decompose by the rancidity process.

The rancidity process is the natural degradation process for protein products. The rancidity process proceeds by the creation of sulfuric acid from sulfur in the lipoic acids. As the pH drops by the creation of sulfuric acid, the acidic pH further breaks apart amino acids and lipoic acids; this further creates sulfuric acid from the lipoic acids while releasing ammonia from the amino acids. While it appears sensible to oxidize the sulfide odors of the DS or to control the rancidity process with an oxidizer, typical oxidation methods are not practical. Typical oxidizers such as caustic, potash, soda ash and lime, etc. are not self-buffering. These chemicals will increase the pH over 10 having the capability to increase the pH over 12. As the pH increases above 10, oxidation of the lipoic acids and of the amino acids releases sulfide(s) and ammonia. Due to this process, the addition of typical oxidizers will only accelerate the degradation of lipoic acids and amino acids. This degradation process can be controlled by an additional Haase patent, which utilizes the addition of at least one of magnesium oxide and/or magnesium hydroxide. These magnesium products are self-buffering at a pH between 9 and 10; therefore, this process can also be used to control sulfide(s) in DS while not accelerating the degradation of lipoic acids or amino acids within the DS. The Haase Patent 6,066,349 is incorporated herein as a reference. However, the Haase patent does not include a process for the control of ammonia odors, or of TDS dewatering. To control Vectors in our environment, the US EPA and many state agencies are requiring the production of Class "A" bio-solids for land application of bio-solids. In combination with this legislative and regulatory trend, solid waste is becoming an issue to municipalities as landfill sites become more difficult to locate and permit. Since biosolids are a natural and wholly organic fertilizer, a process to economically produce Class "A" DS without an appreciable objectionable odor is needed. Further, a process that helps to insure that DS do not become attractive to Vectors would be beneficial to the environment, as well as to human and animal health.

Summary of the Invention

An embodiment of the invention is to devise effective, efficient and economically feasible methods, processes and apparatus for producing Class "A" digested solids per the US EPA 503 Regulations.

Another embodiment of the invention is to devise effective, efficient and economically feasible methods, processes and apparatus for removing sulfide odors in digested solids and in sludge. Another embodiment of the invention is to devise effective, efficient and economically feasible methods, process and apparatus for removing ammonia odors in digested solids and in sludge.

Another embodiment of the invention is to devise effective, efficient and economically feasible thermophillic digestion methods, process and apparatus wherein sulfide and ammonia odors can be controlled.

Another embodiment of this invention is to provide methods, processes and apparatus to prepare digested solids for land application recycling such that the bio-solids have minimal objectionable odor. Another embodiment of this invention is to provide methods, processes and apparatus to prepare digested bio-solids wherein objectionable odor is controlled from the rancidity process.

Another embodiment of this invention is to provide methods, processes and apparatus to prepare digested solids for recycling wherein the digested solids contain a disinfectant to reduce the risk of recontamination of the bio-solids.

Another embodiment of this invention is to devise an effective, efficient and economically feasible methods, processes and apparatus to produce recyclable Class "A" digested solids per the US EPA 503 Regulations such that the bio-solids have minimal objectionable odor and have a disinfectant to reduce the risk of contamination of the bio- solids with pathogens.

Another embodiment of this invention is to develop a bio-solids product, which has minimal objectionable odor.

Another embodiment of this invention is to develop a thermophillic bio-solids product, which has minimal objectionable odor and is Class "A" per the US EPA 503 Regulations.

The Use and Mechanism of Thiobacillus and/or Thiobacillus Denitrificanus

The present invention utilizes thiobacillus and/or thiobacillus denitrificanus

(referred to hereafter as "CV-S" cultures) that are designed for removing, while using, sulfur compounds as sources of energy. The CV-S cultures comprise a unique combination of thiobacillus and/or thiobacillus denitrificanus that are raised on sulfιde(s).

An inoculation and augmentation program utilizes the "S' cultures to permit nitrification. In a most preferred embodiment, the CV-S cultures comprise 100% of the inoculation. In a preferred embodiment the "S" cultures are blended with heterotrophs. The CV-S cultures can be added in a blend combination of about 1 % to about 100% "S". The CV-S cultures are introduced into MAD via an enricher reactor or directly to the MAD. As a preferred version, the enricher reactor reduces the required augmentation.

The CV-S cultures are best delivered as a refrigerated concentrated liquid. The CV-S cultures can be dry blended with heterotrophic cultures. The CV-S cultures have the ability to grow under reduced oxygen conditions and at lower that neutral pH ranges. However, the CV-S cultures do not generate pH levels that are as low as the pH levels generated by sulfate-reducing bacteria (SRB). Despite being an obligate aerobe, the CV- S cultures are able to flourish at interfaces of anaerobic environments where CV-S cultures obtain energy by absorbing and detoxifying hydrogen sulfide (H S) and sulfur dioxide (S0₂) (sulfide(s)). Sulfide(s) are combined with low levels of available oxygen to generate neutral products (sulfur and water), along with metabolic energy for the CV-S cultures. A major advantage of the CV-S cultures is that the resulting sulfur is not further oxidized to sulfuric acid.

TDS Dewatering

This method, in addition to being capable of dewatering different types of SS, can also dewater mixtures of different types of sludges. For example, results of tests have shown that the method can be applied to dewater a mixture of aqueous biological solids with aqueous primary solids.

Chemical means of dewatering may be applied in one of five methods, all of which are a significant operational improvement and yield increased operational savings over dewatering methods utilizing traditional polyacrylamides, especially when used with TDS. The primary component in the five solids dewatering methods is most preferably at least one of: an aluminum salt, an iron salt and/or a polyquaternary amine, or any combination thereof. The polyquaternary amine is most preferably of the di-allyl dimethyl ammonium chloride (DADMAC) moiety or from the epichlorohydrin di-methyl amine (Epi-DMA) moiety or of Mannich moiety preparation. By the first and most preferred dewatering method, the primary component is added, along with a cationic polyacrylamide to the TDS. By the second dewatering method, the primary component is added to an amount which creates a slight cationic overcharge prior to adding an anionic polyacrylamide to the TDS. By the third sludge dewatering method, a quaternized polyacrylamide, having the polyquaternary amine as part of its polymer chain, is produced by co-polymerization of acryl amide with monomers of polyquaternary amine moiety and is added individually to the TDS. The monomers of quaternization for this method are preferably those of quaternization for the polyquaternary amines in the primary component: allylic chloride and/or epichlorohydrin in concert with Dimethyl amine or Mannich. By the fourth dewatering method, the quaternized polyacrylamide from the third sludge dewatering method is added in concert with a cationic polyacrylamide or prior to an anionic polyacrylamide to the TDS. By the fifth dewatering method, the quaternized polyacrylamide from the third sludge dewatering method is added in concert with the primary component along with preferably a cationic polyacrylamide or prior to an anionic polyacrylamide to the TDS.

Application of Magnesium Oxide and/or Magnesium Hydroxide

The present invention provides magnesium oxide (MgO), magnesium hydroxide (Mg (OH)₂) or both being applied as a preservative for TDS or DS. Magnesium oxide hydrolyzes to magnesium hydroxide upon contact with water. The method of application of the preservative for neutralizing acids (including amino acids) during degradation reactions of TDS and DS is also presented.

The preservative significantly improves the shelf life of TDS or DS while controlling sulfide odors. The preservative of the present invention effectively and efficiently buffers TDS and/or DS from acid degradation reactions. Presently and in the past, pH stabilizers have existed and have been used in many forms. Various pH stabilizers have been used for different purposes; among those are sodium hydroxide, potassium hydroxide, calcium oxide, calcium hydroxide and sodium bicarbonate. Most pH stabilizers, among pH stabilizers that have been reviewed, are not self-buffering. Sodium hydroxide has a very strong ability to neutralize acids, but is not self-buffering. Addition of sodium hydroxide results in a logarithmic increase in the hydroxide ion concentration. In the case of recycled proteins, stabilization of acid degradation reactions within 12 hours requires an amount of sodium hydroxide that will oxidize the proteins, thereby increasing degradation reactions. Unfortunately, pH stabilizers that have been determined to be self-buffering do not have a very strong ability to neutralize acids. Although sodium carbonate and sodium bicarbonate are self-buffering at a certain pH level, they are limited in ability to neutralize acids.

The uniqueness of magnesium oxide and/or magnesium hydroxide as high and low pH buffer lends to a unique solution for rancidity reactions. Upon coming into contact with water, MgO immediately hydrolyzes to form aqueous Mg(OH)₂, Mg⁺² and two OH^". However, in contrast to sodium and potassium, magnesium oxide forms two (versus one) hydroxyl groups (Mg (OH)₂ vs. NaOH and KOH) in an aqueous environment. Therefore, on a molar basis, magnesium oxide is two times more efficient to neutralize acids than is sodium hydroxide or potassium hydroxide. Sodium hydroxide and potassium hydroxide have the ability to neutralize acids and increase the pH. However, sodium hydroxide and potassium hydroxide are so strong that they oxidize proteins, as well as fats, during a short-term increase of the pH before a rapid decrease in pH, which occurs due to subsequent acidification of the proteins. High concentrations of sodium hydroxide will have a pH at or near 14. Hydroxide ion concentrations available above 10 will oxidize most organic materials, especially proteins and fats. As a point of reference, many biocides are strong oxidizers. Due to the limited solubility of magnesium in water, magnesium oxide is many times more effective neutralizing acidity than calcium oxide or calcium hydroxide. Magnesium oxide is much more effective neutralizing acidity than sodium bicarbonate as well.

Finally, magnesium oxide and magnesium hydroxide are known disinfectants. It is a common practice for hospitals to utilize these chemicals to disinfect hospital waste products, including human body parts. Such a disinfection capability is important to TDS and to MDS. Once a Class "A" DS is created, Vectors could recontaminate the product. Application of magnesium oxide and/or magnesium hydroxide, or both can provide a preventative disinfectant to the ADS.

Bio-Solids Recycling

The most preferred use of the recycled bio-solids is as a fertilizer. Used as a fertilizer, the TDS is an organic fertilizer providing nutrients to plant life by natural processes while reducing pathogens and/or Vectors in the environment. By reducing pathogens and/or Vectors in our environment, the final TDS product is safer to land apply than is recycled manure. The TDS in this invention will not acidify the soil or render the soil alkaline. In comparison, the use of inorganic fertilizers can easily acidify the soil.

Further, treatment of bio-solids with oxidizers, chemical treatment, leaves the bio-solids alkaline unless the bio-solids are pH adjusted with an acid. While the chemical process itself is expensive, further pH adjustment with an acid increases the costs even further.

The decomposition of organic matter, bacteria, into the basic substances utilized for plant life is the nutrient process that occurs in nature. Therefore, recycling the final

TDS product as a fertilizer is a natural recycling process. By controlling pathogens,

Vectors and odor of the final ADS product, a natural fertilizer can be made that is beneficial to the environment, and which can be used in many applications.

Brief Description of the Drawings

A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiments are considered in conjunction with the following drawings, in which:

Figure 1 illustrates the preferred embodiments of this invention in block diagram form for ATD without MAD recycle.

Figure 2 illustrates the preferred embodiments of this invention in block diagram form for ATD with MAD recycle.

Figure 3 illustrates the preferred embodiments of this invention in block diagram form for ATAD without MAD recycle.

Figure 4 illustrates the preferred embodiments of this invention in block diagram form for ATAD with MAD recycle. Figures 1 through 4 are to be considered as generally descriptive and not restrictive of the embodiments of this invention.

Detailed Description of the Preferred Embodiments

The present invention is described in connection with one or more preferred embodiments. However, it should be understood that the invention is not limited to those embodiments. In contrast, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the specification and of the appended claims.

The present invention provides improved methods, processes and apparatus of producing Class "A" digested bio-solids (ADS), as defined by the US EPA 503 regulations, along with methods, processes and apparatus to produce MDS, TDS and ADS, which have minimal objectionable odor. The present invention provides ATD methods, processes and apparatus, ATAD methods processes and apparatus, and MAD methods, processes and apparatus that control objectionable ammonia and sulfide odors. The most preferred methods, processes and apparatus to obtain ADS are with Thermophillic Digestion (TD). In TD, aqueous SS from secondary, biological, treatment and/or aqueous SS from primary treatment is sent to digestion. While TD can be either anaerobic or aerobic, it is most preferred that the TD temperature and residence time be such to obtain Class "A" treatment per the US EPA 503 regulations. While some treatment facilities are able to maintain pathogen destruction performance without thermophillic treatment, treatment of SS without TD is not preferred. Compared to ATD, the ATAD process requires the least amount of equipment. In either case ATAD or ATD, it is preferred that plug flow performance be obtained. It is most preferred that in both the ATD and in the ATAD process that the plug flow aspects of the 503 regulations be obtained. To obtain plug flow performance additional vessel(s) are normally required. If ATD is used, it is preferred that the acidification portion of digestion be prior to a separate vessel which is to be used for the gas production process. While the acidification process can be messophillic, it is preferred that both vessels be thermophillic. It is most preferred that the gas phase vessel be thermophillic. By separation of acidification and gasification, better control can be made of the pH within each process, thereby providing the ability to optimize each process. It is most preferred that acidification is prior to gasification. It is preferred that the energy available in the hydrocarbon gas produced from the gas phase process of ATD be used to heat ATD. It is most preferred that the hydrocarbon gas be fired to heat a boiler to maintain thermophillic temperatures per the 503 regulations in ATD. If post digestion ADS drying includes hot air or evaporative air-drying, it is most preferred to use at least a portion of the energy available from the hydrocarbon gas of ATD gasification in evaporative air-drying of the TDS. It is most preferred to operate TD between 130 °F and 150 °F; it is preferred to operate TD between 120 °F and 160 °F. It is most preferred that the residence time and temperature combination in TD obtain the required fecal and coliform counts in the 503 regulations.

To control ammonia, TD is to be accompanied with Messophillic Aerobic Digestion (MAD). It is important to note that MAD can be any messophillic biological system which is capable of supporting nitrification. While MAD does not necessarily have to perform digestion, it is preferred that the MAD performs a final digestion. The purpose of the MAD is to biologically scrub ammonia and sulfide(s) generated in ATD and/or ATAD. MAD is to utilize a biological nitrifying population. It is preferred that the nitrifying population contains nitrosonomas; it is most preferred that the nitrifying population contains nitrosonomas and nitrobactor. Nitrification can occur with heterotrophs; however, this is not preferred. It is most preferred that MAD be sized such that the nitrifying population is self-sustaining from the ammonia generated in thermophillic digestion. In order to support nitrification, it is most preferred that MAD has a mean biological residence time, or a sludge age, of greater than 10 days; it is preferred that MAD has a mean biological residence time, or sludge age, of greater than 5 days. It is not practical for any messophillic treatment to have a mean biological residence time, or sludge age, of greater than approximately 60 or 90 days, as in that amount of time the equipment expense is exorbitant and nature will have its own ability to seed nitrifiers and thiobacillus. It is most preferred that the rate of addition to MAD from TD or recirculation from MAD back to TD be controlled by the ammonia concentration in TD or in MAD, or both. It is most preferred that the ammonia concentration be controlled in MAD such that ammonia toxicity is not a biological operating challenge in MAD or in TD. To control nitrates and nitrites, it is most preferred that MAD feed back into an ATD for facultative denitrification and/or that an additional facultative digester be utilized for denitrification. In the gasification ATD or in a facultative digester, a denitrifying population can be maintained converting nitrites and/or nitrates to nitrogen gas. It is preferred, if denitrification is required, that denitrification be performed in either a facultative digester or in ATD with a facultative population which are capable of using nitrites and nitrates as an electron donor source.

The vapors from TD are preferably to be contained so that the process does not have an objectionable odor. It is preferred for an ATD or an ATAD to pass the TD vapors through a scrubber removing objectionable sulfide and ammonia odors. It is most preferred to pass the vapors through MAD, where the sulfide and ammonia conversion process is in place. However, if a scrubber is used, it is preferred that thiobacillus and/or thiobacillus denitrificanus be used in the scrubber to remove sulfide(s) from the gas stream. If a scrubber is used it is most preferred that at least one of: magnesium oxide, magnesium hydroxide, thiobacillus and thiobacillus denitrificanus, or any combination thereof be used in the scrubber aqueous stream with a nitrifying population. The addition of magnesium oxide, magnesium hydroxide, thiobacillus or thiobacillus denitrificanus will depend on the sulfide(s) to be removed in the TDS. It is most preferred that the concentration of thiobacillus or thiobacillus denitrificanus be near a 1 :1 ratio with the sulfide(s) to be removed. It is preferred that the ratio of thiobacillus and/or thiobacillus denitrificanus to sulfide(s) be in a range of 1 :100 to 100:1. If magnesium chemistry is used, it is preferred that the ratio of magnesium oxide and/or magnesium hydroxide to sulfide(s) be near a ratio of 1 : 1. It is preferred that the ratio of magnesium oxide and/or magnesium hydroxide to sulfide(s) be in a range of 1 : 100 to 100:1. However, of high importance to the use of magnesium oxide and magnesium hydroxide (magnesium oxide forms magnesium hydroxide upon contact with water) is solubility. It is most preferred that the amount of magnesium hydroxide in the scrubber be less than the solubility limit of magnesium hydroxide to prevent scrubber fouling. The solubility limit of magnesium hydroxide in water is approximately 2 percent, depending upon temperature, pressure and water contaminants.

Should ammonia odors be objectionable in the exhaust flume of the boiler(s) to heat ATD, either the MAD needs recycle to ATD and/or a scrubber is required. If recycle is in place and ammonia odors are objectionable in the exhaust flume of the boiler(s), then MAD needs adjustment. Should sulfide odors be objectionable in the exhaust flume of the boiler(s), it is most preferred that the exhaust flume of the boilers be sent to MAD via the air blowers for MAD, otherwise it is preferred that the exhaust flume of the boilers be sent to a scrubber.

It is most preferred that oxygen is available in MAD, or other messophillic unit, for Nitrification; Nitrification requires a 4:1 ratio of 0₂:NH OH. To monitor, it is most preferred that the dissolved oxygen be greater than 1.5 ppm; it is preferred that the dissolved oxygen be greater than 0.5 ppm. While the nitrification population may obtain enough carbonate for nitrification from the TDS, if a carbonate source is required, it is preferred that CaO, CaOH and/or NaHC0₃ provide carbonate and alkalinity for nitrification. It is preferred that CaO, CaOH and/or NaHC0₃ be used with MgO and/or Mg(OH)₂ to control pH and provide a carbonate source for the nitrifiers. To monitor, it is most preferred that the M-Alkalinity be greater than 100 mg/L; it is preferred that the M- Alkalinity be greater than 50 mg/L. It is most preferred that the pH be less than 8.0 and greater than 7.0. It is preferred that the pH be less than 10.0 and greater than 6.5. It is most preferred that the total ammonia nitrogen concentration be less than 150 ppm. It is preferred that the total ammonia nitrogen concentration be less than 350 ppm. To facilitate nitrification, the sulfide concentration must be controlled in MAD, or other messophillic unit. Control of sulfide(s) for nitrification and for sulfide odors in the TDS, MDS or in the DS is preferred. It is most preferred to control sulfide(s) with a population of thiobacillus and/or thiobacillus denitrificanus. It is preferred to oxidize sulfide(s) to sulfate by treating the TDS or MDS with at least one of magnesium oxide, magnesium hydroxide, air and oxygen, or any combination thereof. It is an embodiment to oxidize sulfide(s) to sulfate with extended aeration; however, this is not preferred as increased equipment investment would be required. It is most preferred that sulfιde(s) be controlled to less than 3 ppm and preferred that sulfide(s) be controlled to less than 5 ppm. It is preferred to use at least one of thiobacillus, thiobacillus denitrificanus, magnesium oxide and/or magnesium hydroxide, or any combination thereof to control sulfide(s).

To manage operating temperatures and energy, it is preferred that a heat exchanger be placed in the exit line from TD cooling TDS for MAD while heating SS for TD and/or in the exit line from TD cooling TDS for MAD while heating DS from MAD for TD and/or any combination thereof. The operating temperature of TD is preferred to be approximately 140 +/- 10 °F, yet can be between 120 and 160 °F. The operating temperature of the MAD is preferred to be approximately 85 +/- 15 °F, yet can be between 40 and 105 °F. The operating temperature of the SS will depend upon the surrounding environment and is anticipated to be normally approximately 70 +/- 30 °F. It is very common for digesters over time to become contaminated with poor biological substrate solids from primary separation. These materials are most commonly grease and hair. While solids, including grease and hair, should pass through a heat exchanger; SS may cause heat transfer inefficiencies or flow obstructions in the heat exchanger, otherwise known as heat exchanger fouling. To control heat exchanger fouling, it may be necessary to provide: solvent injection, biological augmentation injection, oxidizer injection or surfactant injection upstream of the heat exchanger. Should an oxidizer be used, it is preferred to utilize an acid downstream of the heat exchanger to adjust the pH to approximately that of the digesters. Should an oxidizer be used, it is most preferred that pH adjustment be performed with carbonic acid. It is most preferred that biological injection is used since the biological augmentation would be beneficial to TD and MD, as well as to heat exchanger fouling. TDS can leave digestion from TD; but it is preferred that TDS leave digestion from MAD to minimize odors in the TDS. It is most preferred that the ammonia nitrogen content of the TDS be less than 150 ppm and preferred that the ammonia nitrogen concentration be less than 350 ppm. Should there be any ammonia odor in the TDS or MDS, the MAD process should be adjusted for more complete nitrification. From time to time nitrifiers may need to be added to MAD. Should there be any sulfide odor in the TDS or MDS, sulfide odor can be controlled by application of at least one of: increased aeration, increased oxygen, thiobacillus, thiobacillus denitrificanus, magnesium oxide and/or magnesium hydroxide, or any combination thereof to at least one of: the MAD, MDS and TDS from TD, or any combination thereof. It is common in many areas to land apply by spraying the liquid TDS or MDS product. From digestion, the percent solids in the TDS or MDS are normally approximately 4 +/- 3 percent. Should dewatering be required, a belt press or a centrifuge is preferred, although there are other methods available to mechanically and chemically increase the percent solids to approximately 25 +/- 8 percent. It is most preferred that the chemical portion of dewatering be accomplished with a cationic polyacrylamide in combination with at least one of: an iron salt, an aluminum salt and/or a polyquaternary amine, or any combination thereof. It is preferred that dewatering be accomplished with an anionic polyacrylamide after prior treatment with at least one of: an iron salt, an aluminum salt and/or a polyquaternary amine, or any combination thereof. If a polyquaternary amine is used, it is most preferred that the molecular weight be high, measured as a viscosity of greater than 1000 cps at 20 percent activity. If a polyquaternary amine is used, it is preferred that the quaternization moiety be DADMAC, Epi-DMA and/or Mannich, or any combination thereof. For dewatering, it is preferred to minimize the chemical dosage. While it is preferred to have a cationic or anionic polyacrylamide dosage of less than 100 ppm/percent solids, dosages as high as 500 ppm/percent solids are possible. In the case of iron or aluminum salt addition, while it is preferred to have an iron or aluminum dosage of less than 100 ppm/percent solids, dosages as high as 500 ppm/percent solids are possible. In the case of polyquaternary amines, it is preferred to have the polyquaternary amine dosage less than 100 ppm/percent solids, dosages as high as 500 ppm/percent solids are possible. It is most preferred to optimize a dewatering combination of at least one of: iron salt, aluminum salt, polyquaternary amine and quaternized polyacrylamide with either a cationic polyacrylamide or an anionic polyacrylamide. Such optimization normally leads to atotal chemical dosage of approximately less than 250 ppm/percent solids.

Some facilities utilize a natural gas heated hot air fluidized bed to dewater the liquid DS from digestion to solids concentrations of approximately 90 +/- 5 percent. While these processes are employed for DS, these processes are not preferred due to their energy cost of operation.

Should the TDS or MDS have a recycling or land application that requires storage or bagging, further dewatering will be required to control spontaneous combustion. For TDS or MDS having a solid content of approximately greater than 30 percent and preferably greater than approximately 85 percent, a hot air-drying or evaporative air- drying operation is preferred.

Once the final TDS or MDS product is prepared for recycle, an odor check should be made. If an ammonia odor (concentration) is above specification, MAD needs operational adjustment. If sulfidic odor is present, then either MAD needs adjustment and/or the final product require an application of at least one of: thiobacillus, thiobacillus denitrificanus, magnesium oxide and/or magnesium hydroxide, or any combination thereof. It is most preferred that the final DS product has a residual concentration of at least one of: magnesium oxide and/or magnesium hydroxide to control at least one of: sulfide odors, pathogen contamination and rancidity. It is most preferred if the final ADS product be bagged or stored that a residual concentration of at least one of magnesium oxide and/or magnesium hydroxide be maintained; these compounds are also fire retardants. It is preferred to utilize the TDS as a lawn fertilizer. In many applications, it may be preferred to apply the final TDS or MDS product as a liquid. In those applications, the final product is a Newtonian liquid up to approximately 12 percent solids. At these concentrations, the product is stable from spontaneous combustion. To dry the product, it is preferred to dewater per the chemical/polymer/mechanical means reviewed earlier within this specification. These chemical/polymer/mechanical means will create TDS or MDS having a solids content of approximately 25 +/- 8 percent. While a solids content of 25 +/- 8 percent is potentially combustible with spontaneous combustion, this product is stable for short periods of transportation and/or storage prior to land application. For extended storage times and/or bagging of the TDS or MDS, it is most preferred to dry TDS or MDS to approximately 85 percent minimum solids.

The percent ratio of Nitrogen-Phosphorous-Potassium in bacteria is approximately a 6-6-0. Since the Nitrogen-Phosphorus-Potassium percentage ratio in the TDS and DS will be approximately a 6-6-0, it may be desirable in some applications to blend the final product with chemical fertilizers. This blending can significantly increase the content of at least one of nitrogen, phosphate, iron and/or potassium, or any combination thereof. It is preferred to blend the final ADS product with, add the final ADS product to the soil with or to use the final ADS product as a fertilizer blended with at least one of: a nitrogen salt, a nitrogen compound, urea, an organic-nitrogen compound, a phosphate salt, a phosphate compound, an organic-phosphate compound, an iron salt, an iron compound, a potassium salt, a potassium compound, a potassium/phosphate compound and an ammonia/phosphate compound, or any combination thereof.

EXAMPLE 1

On 8/02/01, a sample was obtained from final DS cake product of the belt dewatering press in Beaumont, Texas. Cake solid from the belt press dewatering operation is normally near 30 percent. Beaumont operates a messophillic anaerobic digester. The cake solids were utilized in bench scale testing to ascertain whether thiobacillus or magnesium oxide were viable additives to control sulfide odors from DS. Each sample was prepared, mixed and allowed to sit for 24 hours. After 24 hours, observations were made on the sulfide content of the sludge. Since sulfide(s) have an odor threshold of 2 ppb, an individual smell or olfactory test is deemed to be sufficient. Results of this test are tabulated on the next page.

Odor Control Testing of DS

NO. SAMPLE ODOR/RESULT

1 Control Heavy sulfide odor/no result

2 1% MgO Slight sulfide and bran/fair

3 5% MgO Bran/very good

4 0.5% Bio "S-L" Sour/marginal

5 1% MgO + 0.25% Bio "S-L" Musty/fair

EXAMPLE 2

Based upon completion and revision of several tests, it is determined that blends of thiobacillus cultures with nitrifiers are capable of allowing nitrification to occur. During the tests, the goal of the treatment of the wastewater was the achievement of nitrification, by applying co-cultures of the thiobacillus bacteria with various heterotrophs.

"S" cultures blended in concentrations of 25% or more with various heterotrophs form co-cultures which are capable of minimizing sulfide content and to allow nitrification to occur, without application of any nitrifiers. BOD removal and nitrification is the operating challenge of a 45-acre pond having 3 MGD of wastewater flow per day in DeQueen, AR. At the onset, the level of sulfide(s) in the wastewater was high enough that nitrification halted. The level of sulfates in the sludge of the bottom of the pond was over 10,000 ppm. Dissolved oxygen had reduced to non-detectable levels in various parts of the pond. Five tons of sodium nitrate and one hundred pounds (100 pounds) of co-cultures of thiobacillus with various heterotrophs were added to the wastewater. The sodium nitrate was added to initiate anoxic conditions for the thiobacillus. The co-cultures comprised a 20 percent concentration of thiobacillus. Within five days, the ammonia level dropped from 30ppm to 4 ppm. No nitrifiers were used or required in the process. Nitrification was performed by nitrifiers that were originally present in the pond.

EXAMPLE 3 A bench test was performed utilizing an electric variable speed beaker stir system, commonly referred to as ajar test. 2000 ppm of CV 3750 (20% active) was added to 500 ml of sludge from a thermophillic digestion. The percentage of solids in the sludge was about 4.4 percent. The beaker was allowed to stir at 120 rpm for 30 seconds. At 30 seconds, the rpm was reduced to 90 and 1500 ppm of CV 5120 in a 0.25 percent solution was added to the beaker. After 15 seconds, the stir speed was slowed to 30 rpm and mixed for another 30 seconds. Large, heavy floe (e.g. with a diameter of at least 4mm) was formed with a somewhat cloudy supernatant.

EXAMPLE 4

Ajar test was performed utilizing an electric variable speed beaker stir system. 3000 ppm of CV 3650 (20% active) was added to 500 ml of sludge from a thermophillic digestion. The percentage of solids in the sludge was about 4.4 percent. The beaker was allowed to stir at 120 rpm for 30 seconds. At 30 seconds, the rpm was reduced to 90 and 250 ppm of CV 6140 in a 0.25 percent solution was added to the beaker. After 15 seconds, the stir speed was slowed to 30 rpm and mixed for another 30 seconds. Large heavy floe (e.g. with a diameter of at least about 4mm) was formed with a very clear supernatant.

EXAMPLE 5

A jar test was performed utilizing an electric variable speed beaker stir system. 1400 ppm of CV 3230 (Epi-DMA with a medium molecular weight e.g. over 300,000 and 50% active) was added to 500 ml of sludge from a thermophillic digestion. The percentage of solids in the sludge was about 4.4 percent. The beaker was allowed to stir at 120 rpm for 30 seconds. At 30 seconds, the rpm was reduced to 90 and 260 ppm of CV 6140 in a 0.25 percent solution was added to the beaker. After 15 seconds, the stir speed was slows to 30 rpm and mixed for another 30 seconds. Large, heavy floe (e.g. with a diameter of at least about 4mm) was formed with a very clear supernatant.

EXAMPLE 6

A jar test was performed utilizing an electric variable speed beaker stir system. 850 ppm of CV 5380 (polyacrylamide with a DADMAC cationic co-monomer) were added to about 500ml of sludge from a thermophillic digestion. The percentage of solids in the sludge was about 4.4 percent. The beaker was allowed to stir at 90 rpm for 15 seconds. At 15 seconds, the rpm was reduced to 30 and mixed for another 30 seconds. Small floe (e.g. with a diameter under about 3mm) was formed with a very clear supernatant.

EXAMPLE 7

Ajar test was performed utilizing a glass jar to mix polymer with the sludge. 350 ppm of CV 5380 (polyacrylamide with a DADMAC cationic co-monomer) along with 450 ppm of ClearValue CV 5120 (traditional polyacrylamide with a medium charge density) were added to about 100 ml of sludge from a thermophillic digestion. The percentage of solids in the sludge was about 4.7 percent. The jar was gently shaken for approximately 30 seconds. At 30 seconds, the results were observed. Large, strong floe (e.g. with a diameter of at least about 4 mm) was formed with a very clear supernatant. Example 7 was repeated with a varying cationic charge densities for the traditional polyacrylamide polymers. The best results were obtained with CV 5120.

EXAMPLE 8

A plant test was performed on Sept. 10, 1996 at the municipal wastewater treatment facility for the City of College Station, Texas. This facility has a thermophillic digestion as designed by Kruger, Inc. The average temperature of the digester is usually near 149° F (65° C). Dewatering is accomplished on a Sharpels Polymixer 75000 centrifuge. Polymer inversion is accomplished on a Polymixer 500, which is designed for dry polymer. Normal plant operation requires 1500 to 2000 ppm of Nalco 9909 obtaining variable sludge cake dryness, a final centrate that is usually much over 200ppm of total suspended solids (TSS) and a plant throughput of 10 to 15 gpm of sludge,

The centrifuge was started up on CV 5380 having a polymer concentration of 800 ppm and a plant throughput of 30gpm. The sludge produced was low on cake solids obtaining an average near 12 percent. The centrate was 100 to 200 TSS with nearly all of the total suspended solid from small floe (e.g. of a diameter of less than 1mm) that survived the centrifuge. Even though this was an operational improvement, the floe produced was weak for the type of treatment incurred within the centrifuge. EXAMPLE 9

A plant test was performed on Sept. 10, 1996 at the municipal wastewater treatment facility for the City of College Station, Texas. This facility has a thermophillic digestion as designed by Kruger, Inc. The average temperature of the digester is usually near 149° F (65° C). Dewatering is accomplished on a Sharpels Polymixer 75000 centrifuge. Polymer inversion is accomplished on a Polymixer 500, which is designed for a dry polymer. Normal plant operation requires 1500 to 2000 ppm of Nalco 9909 obtaining variable sludge cake dryness, a final centrate that is usually much over 200ppm of total suspended solids (TSS) and a plant throughput of 10 to 15 gpm of sludge,

The centrifuge was started up on CV 5380 and Nalco 9909 with the CV 5380 having a polymer concentration of 400 ppm and the Nalco 9909 having a concentration of 450 ppm. The centrifuge was run between 45 and 55 gpm of sludge throughput. The produced sludge was over 18 percent cake solids. The centrate was less than 50 TSS.

EXAMPLE 10

A plant test was performed on Feb. 18, 1998 at the municipal wastewater treatment facility for the City of Texarkana, Tex. This facility operates a traditional anaerobic digestion process. However, during the last six months of 1997, the digestion temperature was slowly increased until 120° F. was obtained; the fecal count dropped to zero on the digested sludge.

Dewatering is accomplished on a two-meter Ashbrook belt filter process. The belt presses were started up on CV5240H and CV3650 at varying concentrations. The most economical dewatered sludge was made with a 60:40 blend of CV 5140H with CV 3650, respectively. This operation reduced plant operating cost by approximately 20%, obtaining in excess 24% sludge cake solids. Other polyacrylamides are unable to even obtain 18 % cake solids at any dosage.

EXAMPLE 1 1 A jar test was performed utilizing a 1 -gallon plastic container. Sludge was obtained front he thermophillic process at College Station, Tex. In this test, aluminum sulfate, ferric chloride, and blends of aluminum sulfate and ferric chloride were evaluated with CV 3650 in combination with CV 5135D.

TDS Dewatering Test with Iron/Aluminum and Cationic Polyacrylamides

48% Aluminum Supernatant Floe 3650 Sulfate 40 % FeCl CV 5135D Performance Performance

10,000 150 Clear Strong/tight

7,500 350 Cloudy Loose

8,500 250 Clear Loose

12,500 150 Clear Loose

500 3,000 200 Clear-yellow Strong/tight

250 4,000 225 Clear-yellow Strong/tight

600 1 ,500 175 Clear-yellow Strong/tight

10,000 150 Clear Poor-water

7,500 350 Clear Loose

500 4,000 400 Clear Loose

400 4,000 600 Clear Loose

EXAMPLE 12

Ajar test was performed with sludge from the thermophillic digestion process at Gulf Coast Waste Disposal Authority in Baytown, Tex. In this test, 30ppm to 50 ppm of CV 3650 in combination with either C V 51 10, CV 5120, CV 5140, CV 5160, or CB5180 at a concentration of 55 ppm to 100 ppm formed a good strong floe with a clear supernatant. Any and all polyacrylamides tried alone required in excess of 350 ppm to dewater.

EXAMPLE 13

Four five-gallon buckets were filled with float from an air flotation recovery unit at a chicken part production facility. Each bucket contained 30 lbs. of chicken and chicken parts containing fats and proteins.

Temperature of operation was approximately 90 °F. Measurements are started upon addition of magnesium oxide. The first set of measurements, which are listed as " CONTROL" data, is made without use of magnesium oxide. The pH values of this protein test are on the next page.

As can be seen, when the MgO preservative is used with animal and animal part containing fats and proteins, a relatively longer term of stability in pH conditions of animal and animal part exists. Without the use of preservative, acidic conditions immediately started. When the MgO preservative is used, stability exists at neutral pH conditions of animal and animal parts. (Please refer to data from use of 2000 ppm of preservative.)

Protein Stability Testing with Magnesiurr i Oxide

Amount of Magnesium Oxide (MgO)

TIME CONTROL 1500ppm 2000ppm 2500ppm

(pH) (pH) (PHO (PH)

9:30 a.m. 7.4 9.3 9.3 9.3

12:30 p.m. 6.7 9.4 9.3 8.0

3:30 p.m. 5.9 7.8 7.6 7.1

6:30 p.m. 5.6 6.5 7.4 7.0

9:30 p.m. 5.5 6.7 7.2 6.6

12:30 a.m. 5.5 6.5 6.6 5.6

3:30 a.m. 5.4 6.4 6.6 6.4

6:30 a.m. 5.3 6.7 6.7 6.6

9:30a.m. 5.3 6.4 6.7 6.6

Certain objects are set forth above and made apparent from the foregoing description. However, since certain changes may be made in the above description without departing from the scope of the invention, it is intended that all matters contained in the foregoing description shall be interpreted as illustrative only of the principles of the invention and not in a limiting sense. With respect to the above description, it is to be realized that any descriptions, drawings and examples deemed readily apparent and obvious to one skilled in the art and all equivalent relationships to those described in the specification are intended to be encompassed by the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall in between.

Claims

WHAT IS CLAIMED:

1. A method of aqueous solids treatment comprising: thermophillic digestion; and messophillic digestion; wherein the aqueous solids are transferred between thermophillic and messophillic digestion; and wherein the concentration of at least one of ammonia and/or sulfide(s) is reduced during messophillic digestion.

2. The method of claim 1, wherein the thermophillic digested solids are Class

"A" per the US EPA 503 regulations.

3. The method of claim 1 , wherein at least one of: the ammonia concentration is less than 350 mg/L, and the sulfide concentration is less than 5 mg/L.

4. The method of claim 1 , wherein at least one of thiobacillus, thiobacillus denitrificanus, magnesium oxide and/or magnesium hydroxide, or any combination thereof is in the messophillic digester.

5. The method of claim 1 , wherein at least one of thiobacillus, thiobacillus denitrificanus, magnesium oxide and/or magnesium hydroxide, or any combination thereof is added to the aqueous solids.

6. The method of claim 1 , wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

7. The method of claim 6, wherein magnesium oxide and/or magnesium hydroxide is added.

8. The method of claim 1 , wherein nitrifiers is added to the messophillic digester.

9. The method of claim 1 , wherein thermophillic digestion is at least one of: aerobic thermophillic digestion and anaerobic thermophillic digestion, or any combination thereof; and the concentration of ammonia and/or sulfide(s) is reduced in the vapors from messophillic or thermophillic digestion by sending the vapors of thermophillic digestion through messophillic digestion.

10. The method of claim 1 , wherein thermophillic digestion is at least one of: aerobic thermophillic digestion and anaerobic thermophillic digestion, or any combination thereof; and the concentration of ammonia and/or sulfide(s) is reduced in the vapors from messophillic or thermophillic digestion by sending the vapors to a gas scrubber; and wherein at least one of: magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers, or any combination thereof is in the scrubber.

1 1. The method of claim 10, wherein at least one of: magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers, or any combination thereof is added to the scrubber.

12. The method of claim 1 , wherein at least one heat exchanger exists in the piping between at least one of: thermophillic digestion, messophillic digestion and the aqueous solids stream to the digesters, or any combination thereof to transfer heat energy between at least two of: thermophillic digestion, messophillic digestion and the aqueous solids to the digesters.

13. The method of claim 1, wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide with at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

14. The method of claim 1 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of an anionic polyacrylamide after the addition of at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

15. The method of claim 1 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization.

16. The method of claim 1 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization subsequent to the addition of a cationic or an anionic polyacrylamide.

17. The method of claim 1 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization in combination with the addition of at least one of: a polyquaternary amine, an iron salt, an aluminum salt and a cationic polyacrylamide, or any combination thereof.

18. The method of claims 13, 14, 15, 16 or 17, wherein the quaternization moiety is at least one of: DADMAC, Epi-DMA and Mannich, or any combination thereof.

19. The method of claims 13, 14, 15, 16 or 17, wherein the solids from said dewatering device flow to an evaporative or an evaporative/mechanical dewatering device.

20. The method of claims 13, 14, 15, 16, 17 or 19, wherein water from thermophillic digestion, messophillic digestion or dewatering is sent to messophillic treatment, wherein ammonia and/or sulfide(s) is reduced.

21. The methods of claim 20, wherein at least one of: magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers are used in the messophillic treatment.

22. The methods of claims 20 or 21 , wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

23. The methods of claim 22, wherein magnesium oxide and/or magnesium hydroxide is added.

24. A method of reducing sulfide(s) within aqueous solids; wherein the aqueous separated solids contain at least one of: thiobacillus, thiobacillus denitrificanus, magnesium oxide and magnesium hydroxide, or any combination thereof.

25. The method of claim 24, wherein said solids are digested bio-solids.

26. The method of claims 24 or 25, wherein said solids contain thermophiles or said solids have been at thermophillic temperatures.

27. The method of claim 24, wherein the sulfide(s) concentration is less than 5 mg/L.

28. The method of claim 24, wherein nitrifiers are present.

29. The method of claim 28, wherein nitrifiers are added.

30. The method of claims 28 or 29, wherein nitrification is performed to a concentration of less than 350 mg/L ammonia.

31. The method of claims 28 or 29, wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

32. The method of claim 31 , wherein magnesium oxide and/or magnesium hydroxide is added.

33. A method of aqueous solids treatment comprising: messophillic digestion; wherein the concentration of sulfιde(s) in the aqueous solids is reduced in said messophillic digestion with at least one of: thiobacillus, thiobacillus denitrificanus, magnesium oxide and magnesium hydroxide, or any combination thereof.

34. The method of claim 33, wherein nitrification is performed.

35. The method of claim 34, wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

36. The method of claim 35, wherein magnesium oxide and/or magnesium hydroxide is added.

37. The method of claims 31 , 32 or 33, wherein nitrifiers are added.

38. The method of claims 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 24, 25, 26, 27, 28, 29, 30, 31 , 32, 33, 34, 35, 36 or 37 wherein said solids is used as a fertilizer.

39. The methods of claim 38, wherein said solids is added to the soil with, blended with or used as a fertilizer with at least one of: a nitrogen salt, a nitrogen compound, urea, an organic-nitrogen compound, a phosphate salt, a phosphate compound, an organic-phosphate compound, an iron salt, an iron compound, a potassium salt, a potassium compound, a potassium/phosphate compound and an ammonia/phosphate compound, or any combination thereof.

40. A new bio-solids product comprising: water, thermophiles, and nintrifiers, wherein the concentration of ammonia in the bio-solids is less than approximately 350 mg/L and the concentration of sulfide(s) is less than 5 mg/L.

41. The bio-solids of claim 40, comprising at least one of: CaO, CaOH, carbonate, bicarbonate, magnesium oxide magnesium hydroxide, thiobacillus and thiobacillus denitrificanus, or any combination thereof.

42. The bio-solids of claim 40, comprising a cationic polyacrylamide with at least one of: an iron salt, an aluminum salt and a polyquaternary amine, or any combination thereof.

43. The bio-solids of claim 40, comprising an anionic polyacrylamide with at least one of: an iron salt, an aluminum salt and a polyquaternary amine, or any combination thereof.

44. The bio-solids of claim 40, comprising a quaternized polyacrylamide.

45. The bio-solids of claims 40, 41, 42, 43 and 44, comprising at least one of: a nitrogen salt, a nitrogen compound, urea, an organic-nitrogen compound, a phosphate salt, a phosphate compound, an organic-phosphate compound, an iron salt, an iron compound, a potassium salt, a potassium compound, a potassium/phosphate compound and an ammonia/phosphate compound, or any combination thereof.

46. A process for digesting aqueous solids defining a process flow path in which the aqueous solids to be treated travels through a number of units including at least a thermophillic digestion unit followed by a messophillic unit, the process comprising:

(A) positioning the messophillic structure, suitable for the colonizing of nitrifiers, wherein the nitrifiers remove ammonia from the aqueous portion of the aqueous solids.

47. The process of claim 46, wherein at least one of: the concentration of sulfide(s) is less than 5 mg/L, and the concentration of ammonia is less than 350 mg/L.

48. The process of claim 47, wherein the sulfide(s) are oxidized to sulfate with the addition of at least one of: air, oxygen, magnesium oxide and magnesium hydroxide, or any combination thereof.

49. The process of claims 46, 47 or 48, wherein nitrifiers are at least a portion of the nitrifying population.

50. The process of claim 46, wherein the thermophillic digested solids are

Class "A" per the US EPA 503 regulations.

51. The process of claim 46, wherein at least one of: thiobacillus, thiobacillus denitrificanus, magnesium oxide, magnesium hydroxide and nitrifiers, or any combination thereof is added to the aqueous solids.

52. The process of claim 46, wherein carbonate and/or bicarbonate is added.

53. The process of claim 46, wherein CaO and/or CaOH is added.

54. The process of claims 52 or 53, wherein magnesium oxide and/or magnesium hydroxide is added.

55. The process of claim 46, wherein the concentration of ammonia and/or sulfide(s) is reduced in the vapors from messophillic or thermophillic unit by sending the vapors of thermophillic digestion or messophillic digestion through a messophillic unit.

56. The process of claim 46, wherein the concentration of ammonia and/or sulfide(s) is reduced in the vapors from the messophillic or from the thermophillic unit by sending the vapors to a gas scrubber; and wherein at least one of: thiobacillus, thiobacillus denitrificanus, magnesium oxide, magnesium hydroxide and nitrifiers, or any combination thereof is in the scrubber.

57. The process of claim 46, wherein at least one heat exchanger exists in the piping between at least one of: the thermophillic unit, the messophillic unit and the aqueous solids stream to the digesters, or any combination thereof to transfer heat energy between at least two of: the thermophillic unit, the messophillic unit and the aqueous solids to the digesters.

58. The process of claim 46, wherein the aqueous solids are sent to a dewatering device, wherein the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide with at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

59. The process of claim 46, wherein the solids are sent to a dewatering device, wherein the percent solids are increased in the aqueous solids by the addition of an anionic polyacrylamide after the addition of at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

60. The process of claim 46, wherein the solids are sent to a dewatering device, wherein the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization.

61. The process of claim 46, wherein the solids are sent to a dewatering device, wherein the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization subsequent to the addition of a cationic or an anionic polyacrylamide.

62. The process of claim 46, wherein the solids are sent to a dewatering device, wherein the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization in combination with the addition of at least one of: a polyquaternary amine, an iron salt, an aluminum salt and a cationic polyacrylamide, or any combination thereof.

63. The process of claims 58, 59, 60, 61 or 62, wherein the quaternization moiety is at least one of: DADMAC, Epi-DMA and Mannich, or any combination thereof.

64. The process of claims 58, 59, 60, 61 , or 62 wherein the solids of said dewatering device flow to an evaporative or an evaporative/mechanical dewatering device.

65. The process of claims 58, 59, 60, 61 or 62, wherein the water from messophillic digestion, thermophillic digestion or dewatering is sent to a messophillic unit, wherein ammonia and/or sulfιde(s) is reduced.

66. The processes of claim 65, wherein at least one of: magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers, or any combination thereof is used in the messophillic unit.

67. The process of claims 65 or 66, wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

68. The processes of claim 67, wherein magnesium oxide and/or magnesium hydroxide is added.

69. The processes of claims 46, 47, 48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58,

59, 60, 61 , 62, 63 or 67, wherein the solids is used as a fertilizer.

70. The processes of claim 69, wherein the solids is added to the soil with, blended with or used as a fertilizer with at least one of: a nitrogen salt, a nitrogen compound, urea, an organic-nitrogen compound, a phosphate salt, a phosphate compound, an organic-phosphate compound, an iron salt, an iron compound, a potassium salt, a potassium compound, a potassium/phosphate compound and an ammonia/phosphate compound, or any combination thereof.

71. A apparatus for aqueous solids treatment comprising: one or more treatment units defining a process flow path in which aqueous solids travels including at least a thermophillic digestion unit, and a messophillic unit residing within the process flow path at a point in the process flow path after thermophillic digestion, wherein at least one of: nitrification and removal of sulfide(s) occur in the messophillic unit.

72. The apparatus of claim 71, wherein the thermophillic digested solids are Class "A" per the US EPA 503 regulations.

73. The apparatus of claim 71 , wherein at least one of: the ammonia concentration is less than 350 mg/L, and the sulfide concentration is less than 5 mg/L.

74. The apparatus of claim 71, wherein at least one of thiobacillus, thiobacillus denitrificanus, magnesium oxide and magnesium hydroxide, or any combination thereof is in the messophillic unit.

75. The apparatus of claim 71, wherein at least one of thiobacillus, thiobacillus denitrificanus, magnesium oxide and magnesium hydroxide, or any combination thereof is added to the aqueous solids.

76. The apparatus of claim 71 , wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

77. The apparatus of claim 76, wherein magnesium oxide and/or magnesium hydroxide is added.

78. The apparatus of claim 71 , wherein nitrifiers are added to the messophillic unit.

79. The apparatus of claim 71, wherein thermophillic digestion is at least one of: aerobic thermophillic digestion and anaerobic thermophillic digestion, or any combination thereof; and the concentration of ammonia and/or sulfide(s) is reduced in the vapors from messophillic or thermophillic digestion by sending the vapors through said messophillic unit.

80. The apparatus of claim 71 , wherein thermophillic digestion is at least one of: aerobic thermophillic digestion and anaerobic thermophillic digestion, or any combination thereof; and the concentration of ammonia and/or sulfide(s) is reduced in the vapors from messophillic or thermophillic digestion by sending the vapors to a gas scrubber; and wherein at least one of magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers, or any combination thereof is in the scrubber.

81. The apparatus of claim 71 , wherein at least one heat exchanger exists in the piping between at least one of: thermophillic digestion, messophillic digestion and the aqueous solids stream to the digesters, or any combination thereof to transfer heat energy between at least two of: thermophillic digestion, messophillic digestion and the aqueous solids to the digesters, or any combination thereof.

82. The apparatus of claim 71 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide with at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

83. The apparatus of claim 71 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of an anionic polyacrylamide after the addition of at least one of: a polyquaternary amine, an iron salt and an aluminum salt, or any combination thereof.

84. The apparatus of claim 71, wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization.

85. The apparatus of claim 1 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization subsequent to the addition of a cationic or an anionic polyacrylamide.

86. The apparatus of claim 71 , wherein the solids are sent to a dewatering device and the percent solids are increased in the aqueous solids by the addition of a cationic polyacrylamide having quaternization in combination with the addition of at least one of: a polyquaternary amine, an iron salt, an aluminum salt and a cationic polyacrylamide, or any combination thereof.

87. The apparatus of claims 82, 83, 84, 85 or 86, wherein the quaternization moiety is at least one of: DADMAC, Epi-DMA and Mannich, or any combination thereof.

88. The apparatus of claims 82, 83, 84, 85 or 86, wherein the solids from said dewatering device flow to an evaporative or an evaporative/mechanical dewatering device.

89. The apparatus of claims 82, 83, 84, 85, 86 or 88, wherein the water from dewatering is sent to messophillic treatment, wherein ammonia and/or sulfιde(s) is reduced.

90. The apparatus of claim 89, wherein at least one of: magnesium oxide, magnesium hydroxide, thiobacillus, thiobacillus denitrificanus and nitrifiers, or any combination thereof is used in the messophillic treatment.

91. The apparatus of claims 89 or 90, wherein at least one of: CaO, CaOH, carbonate and bicarbonate, or any combination thereof is added.

92. The apparatus of claim 91 , wherein magnesium oxide and/or magnesium hydroxide is added.

93. The apparatus of claims 72, 73, 74, 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87 or 88, wherein the solids is: used as a fertilizer, added to the soil with, blended with or used as a fertilizer with at least one of: a nitrogen salt, a nitrogen compound, urea, an organic-nitrogen compound, a phosphate salt, a phosphate compound, an organic-phosphate compound, an iron salt, an iron compound, a potassium salt, a potassium compound, a potassium/phosphate compound and an ammonia/phosphate compound, or any combination thereof.