TWI532688B - Sludge dewatering with dual polymer conditioning - Google Patents

Description

Dewatering sludge with dual polymer conditioning

This is a PCT application filed on Oct. 25, 2011, which is hereby incorporated by reference in its entirety in its entirety in its entirety herein in

The present disclosure relates to compositions and methods for assisting sludge dewatering.

A large amount of sludge is produced in the process of treating activated sludge from sewage and industrial wastewater. Currently, sludge treatment costs account for 25-45% of the operating costs of a typical wastewater treatment plant (“WWTP”). This cost is expected to increase as landfills and incineration costs increase, especially in countries and regions where land space is limited. Typical sludge contains significant amounts of water (70-85% by weight) even after the dewatering process. Such high water content greatly increases the sludge disposal cost, so it is highly desirable to have the sewage treatment plant increase its dewatering efficiency as much as possible.

In the dehydration process, the sludge is usually conditioned with a polyacrylamide-based cationic polymer (flocculant). The conditioned sludge is then dewatered by a physical method such as centrifugation, belt pressure or filtration. The flocculant can cause the colloid and other suspended particles to aggregate, thereby increasing the sedimentation rate and filtration of the sludge.

Therefore, there is a need to improve sludge dewatering. Ideally, improved sludge dewatering will result in a lower cost of sludge disposal.

Flocculation is a key step in sludge dewatering. The present disclosure provides a method of improving flocculation by incorporating a dual polymer conditioning scheme. In addition to the polymeric flocculant, a polymeric coagulant is also applied to the sludge to increase flocculation efficiency. This dual polymer conditioning process allows for the removal of more water from the sludge compared to conventional flocculating conditioning, thereby reducing sludge disposal costs such as sewage treatment plants.

Accordingly, the present disclosure is directed to a method of treating sludge. The sludge contains water. The method comprises: providing the sludge; mixing the polymer flocculant with the sludge to form agglomerated sludge; mixing the cationic flocculant with the coagulated sludge to form a flocculated coagulated sludge; and coagulating from the flocculation At least a portion of the water is removed from the sludge. The polymeric coagulant comprises a copolymer of epichlorohydrin and dimethylamine ("Epi-DMA"), a homopolymer of diallyldimethylammonium chloride ("polyDADMAC"), or a combination of the two .

These and other features and advantages of the present invention will be apparent from the appended claims.

The advantages and advantages of the present disclosure will become more apparent to those of ordinary skill in the <RTIgt;

Detailed Description of the Invention / Preferred Embodiment

The present disclosure may be embodied in a variety of specific examples, but the present disclosure is described by way of a preferred embodiment of the present invention, and the disclosure of the present disclosure is considered to be illustrative of the present disclosure, and is not intended to limit the disclosure In the specific example described.

The title of this section of the specification should be further understood, that is, the "Detailed Description of the Invention" is a requirement of the U.S. Patent Office and is not meant to be construed as limiting the subject matter disclosed herein.

The present disclosure is directed to a method of material composition comprising Epi-DMA or polyDADMAC, or a combination of both, which Epi-DMA can be linear or cross-linked. If crosslinked, the crosslinked Epi-DMA can be selected from the group consisting of amines, primary amines, alkylene diamines of 2 to 6 carbon atoms, polypropylene polyamines, polyethylene polyamines, and combinations thereof. Group of crosslinkers. In certain embodiments, the crosslinking agent is hexamethylenediamine. In certain embodiments, Epi-DMA and/or polyDADMAC can have a molecular weight from 100,000 Daltons to 3 million Daltons. In some embodiments, the molecular weight can range from 500,000 Daltons to 2 million Daltons.

Sludge is a complex gel-like substance that can include mineral particles, microorganisms, and other materials. Those skilled in the art will recognize that the present disclosure pertains to any type of sludge. An example of sludge is waste from wastewater treatment plants ("WWTPs"). Examples of two wastewater treatment plants are urban and industrial. The surface of the sludge particles is usually negatively charged. In conventional sludge conditioning, the sludge is flocculated by a cationic guanamine-based cationic flocculant having a molecular weight in the range of from 5 to 15 gram per mole.

In this innovation, the sludge is first treated with a polymer coagulant of Epi-DMA, polyDADMAC, or a combination of the two. If cross-linked Epi-DMA is selected, the crosslinker can be selected from free amines, primary amines, 2 to 6 carbon atoms. A group of alkylene diamines, polypropylene polyamines, polyethylene polyamines, or combinations thereof. In certain embodiments, the crosslinking agent is hexamethylenediamine. Hexamethylenediamine is also known as hexane-1,6-diamine, 1,6-diaminohexane and 1,6-hexanediamine. In certain embodiments, the polymeric coagulant has a molecular weight ranging from 500,000 to 3 million Daltons. The sludge may be a biological sludge, a primary sludge, or a mixture of biological sludge and primary sludge.

Primary floes are formed when treated with a coagulant. For example, the average particle size of a municipal sludge sample increased from 37 microns to 185 microns after the addition of 100 ppm coagulant. The primary floes are visible to the naked eye and they can be further flocculated by a cationic flocculant prior to dehydration.

The optimum dosage of coagulant and flocculant varies with different sludges and can be determined by a jar test. Due to the reduced surface area and charge requirements of the primary floes, if the same flocculant is used, the optimum dosage of the flocculant in the dual polymer scheme can be reduced by 30%-80% compared to the flocculant alone.

The inventors have found that polymeric coagulants, especially cross-linked Epi-DMA, are particularly effective for treating sludge. While not wishing to be bound by this theory, it is believed that because polymer coagulants have a very high cationic charge density, they bind firmly to the surface of the sludge particles. The smaller molecular weight coagulant is believed to allow the coagulant molecules to penetrate the deeper interior of the sludge gel matrix. While conventional inorganic coagulants such as polyaluminium chloride have shown similar effects, the polymer coagulants disclosed herein appear to cause the sludge particles to aggregate into primary floes. The fully formed flocs formed from these primary floes have a tighter structure and higher floc strength, as a result of A high sludge cake dryness can be achieved when dewatering.

In some embodiments, Epi-DMA is crosslinked by a crosslinking agent. The crosslinking agent may be selected from the group consisting of amines, primary amines, alkylene diamines of 2 to 6 carbon atoms, polypropylene polyamines, polyethylene polyamines, and combinations thereof. In certain embodiments, the crosslinking agent is hexamethylenediamine.

In some embodiments, a polymeric coagulant is first added to the sludge. In certain embodiments, a polymeric coagulant having a concentration greater than 10 ppm by weight but less than 800 ppm can be added. In some embodiments, the total concentration of polymer coagulant in the sludge is greater than 10 ppm by weight, but less than 800 ppm.

In some embodiments, the removal of water from the flocculated sludge is performed by physical means. Examples of physical methods include, but are not limited to, filtration and centrifugation. Those skilled in the art of sludge treatment will readily recognize whether the method is a physical method within the meaning of the term.

In some embodiments, the flocculating agent is a cationic polymer. A particularly suitable flocculating agent is based on polypropylene decylamine. The flocculating agent can be a cationic polymer composed of one or more cationic monomers. Examples of cationic monomers include monoallylamine, diallylamine, vinylamine, dialkylaminoalkyl acrylates and methacrylates and their quaternary or acid salts, including but not Limited to dimethylaminoethyl acrylate methyl chloride quaternary salt ("DMAEA-MCQ"), dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate chlorotoluene quaternary salt, acrylic acid Methylaminoethyl sulfate, dimethylaminoethyl acrylate hydrochloride, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt , dimethylaminoethyl methacrylate chlorotoluene quaternary salt, dimethylaminoethyl methacrylate sulfate, dimethylaminoethyl methacrylate hydrochloride, dialkylaminoalkyl acrylamide Or methacrylamide, and their quaternary or acid salts, such as acrylamidopropyltrimethylammonium chloride, dimethylaminopropylpropenylamine methyl sulfate quaternary salt, dimethyl Aminopropyl acrylamide sulfate, dimethylaminopropyl propylene decylamine hydrochloride, methacrylamide propylamine trimethyl chloride Ammonium, dimethylaminopropyl methacrylamidamine methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide amine sulfate, dimethylaminopropyl methacrylamide hydrochloride Salt, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diallyldiethylammonium chloride and diallyldimethylammonium chloride ("DADMAC"). The alkyl group is usually a C ₁ to C ₄ alkyl group.

In some embodiments, the polymeric coagulant and the sludge are premixed prior to mixing the cationic flocculant.

In some embodiments, the coagulant and/or flocculant is added in admixture. However, there may be other techniques that eliminate the need for the coagulant and/or flocculant to be added under mixing. Such a technique may be a dispensing nozzle such as Nalco PARETO technology from 60563 Vail, Naperville 1601, West Diehl Road, Nalco, Illinois , or other similar technology.

Example

The following examples are given to better understand the present disclosure. The examples are not to be construed as limiting the scope of the disclosure beyond the scope of the language of the claimed invention.

Example 1:

Sludge samples (2.1% total suspended solids ("TSS")) were obtained from municipal wastewater treatment plants. The dewatered sludge cake in the plant has a 16.5% sludge cake solids content. The cationic flocculant is selected from the Nalco Core Shell® flocculant series. The sludge sample and polymer solution were mixed by a jar tester and the capillary attraction time ("CST") of the conditioned sludge was recorded. The polymer concentration with the lowest CST value was determined as the optimum polymer dose. The conditioned sludge is then dewatered in a laboratory filtration unit that simulates industrial pressurized equipment. The resulting sludge cake was dried at 105 ° C until constant weight and the solid content was analyzed. As can be seen from Figure 1, only the flocculant conditioning method has about 16% sludge cake solids, while 133 ppm polymer coagulant (having a hexamethylene group with a molecular weight of about 1.5 million Daltons) The content of diamine crosslinked Epi-DMA) increased to about 19% and was further increased to about 20% when 266 ppm of coagulant was used. The optimum flocculant dosage is reduced from about 120-200 ppm to 30-90 ppm. The total sludge volume reduction at 133 ppm coagulant concentration was about 16%.

Example 2:

Sludge samples (3.7% TSS) were obtained from the refinery wastewater treatment plant. The dewatered sludge cake in the plant has a 15.6% sludge solids content. The draft experiment is similar to Example 1. As can be seen from Figure 2. The coagulant plus flocculant solution has a sludge cake solids content of about 21%, which is 4-6% higher than that of the flocculant alone. The use of the coagulant plus flocculant results in a total sludge reduction of about 20%.

All of the patents mentioned herein are hereby incorporated by reference in their entirety for all of their entireties in their entireties.

In the present disclosure, the word "a" or "an" is understood to include both singular and plural. Conversely, any reference to a plural item, where appropriate, includes the singular.

All ranges and parameters disclosed herein are understood to include the assumption and the inclusion of any and all sub-ranges thereof, and each number between the endpoints. For example, a specified range "1 to 10" should be considered to include (and include) any and all subranges between a minimum value of 1 and a maximum value of 10; that is, all starting from a minimum value of 1 or greater than 1 (eg, 1 to 6.1), and ending at a maximum of 10 or less than 10 (for example, 2.3 to 9.4, 3 to 8, 4 to 7), and finally including each number 1, 2, 3, 4, 5 within the range 6,6,8,9 and 10.

From the foregoing, many modifications and changes can be made without departing from the true spirit and scope of the novel. It should be understood that the specific specific examples or embodiments described are not intended to be construed as limiting. The disclosure is intended to cover all such modifications as fall within the scope of the appended claims.

1 is a graphical illustration of the results of Example 1; and FIG. 2 is a graphical illustration of the results of Example 2.

Claims (20)

A method for treating aqueous sludge, the method comprising: providing the aqueous sludge; a homopolymer selected from the group consisting of a copolymer of epichlorohydrin and dimethylamine, diallyldimethylammonium chloride, and Combining the group of polymer coagulants with the sludge to produce agglomerated sludge; mixing the cationic flocculant with the coagulated sludge to produce flocculated coagulum; from the flocculation and solidification At least a portion of the water is removed from the sludge. The method of claim 1, wherein the polymer coagulant comprises epichlorohydrin and dimethylamine crosslinked by a crosslinking agent. The method of claim 2, wherein the crosslinking agent is selected from the group consisting of amines, primary amines, alkylene diamines of 2 to 6 carbon atoms, polypropylene polyamines, polyethylene polyamines, and combinations thereof. Group of. The method of claim 3, wherein the crosslinking agent comprises a stretched diamine of 2 to 6 carbon atoms. The method of claim 4, wherein the alkylene diamine of 2 to 6 carbon atoms is hexamethylenediamine. The method of claim 1, wherein the polymer coagulant has a molecular weight in the range of from 100,000 Daltons to 3 million Daltons. The method of claim 1, wherein the polymer coagulant is mixed with the sludge at a concentration of more than 10 ppm by weight but less than 800 ppm. For example, the method of claim 1 wherein the removal of water is By physical methods. The method of claim 8, wherein the physical method is selected from the group consisting of filtration, centrifugation, and combinations thereof. The method of claim 1, wherein the polymer coagulant and the sludge are premixed prior to mixing with the cationic flocculant. The method of claim 1, wherein the sludge comprises biological sludge, primary sludge or a mixture of biological and primary sludge. The method of claim 1, wherein the cationic flocculant comprises a cationic polymer based on polyacrylamide. A method for treating aqueous sludge, the method comprising: providing the aqueous sludge; a homopolymer selected from the group consisting of a copolymer of epichlorohydrin and dimethylamine, diallyldimethylammonium chloride, and The polymer coagulant composed of the combination is mixed with the sludge to produce agglomerated sludge; the cationic flocculant is mixed with the coagulated sludge to produce a flocculated sludge; and the flocculated coagulum is removed At least a portion of the water; wherein the polymeric coagulant comprises a group selected from the group consisting of an amine, a primary amine, a dialkylenediamine of 2 to 6 carbon atoms, a polypropylene polyamine, a polyethylene polyamine, and combinations thereof a crosslinker of epichlorohydrin and dimethylamine; wherein the polymeric coagulant has a molecular weight ranging from 100,000 Daltons to 3 million Daltons; and wherein the polymeric flocculant is weighted A concentration greater than 10 ppm but less than 800 ppm is mixed with the sludge. The method of claim 13, wherein the crosslinking agent comprises a stretched diamine of 2 to 6 carbon atoms. The method of claim 14, wherein the alkylene diamine of 2 to 6 carbon atoms is hexamethylenediamine. The method of claim 13, wherein the removing the water is by a physical method. The method of claim 16, wherein the physical method is selected from the group consisting of filtration, centrifugation, and combinations thereof. The method of claim 13, wherein the polymer coagulant and the sludge are premixed prior to mixing with the cationic flocculant. The method of claim 13, wherein the sludge comprises biological sludge, primary sludge or a mixture of biological and primary sludge. The method of claim 13, wherein the cationic flocculant comprises a cationic polymer based on polyacrylamide.