Method for pretreatment of wastewater with nanocomposites and bridging polymers
10273169 ยท 2019-04-30
Assignee
Inventors
Cpc classification
C02F1/008
CHEMISTRY; METALLURGY
C02F2103/26
CHEMISTRY; METALLURGY
C02F2103/32
CHEMISTRY; METALLURGY
C02F2103/322
CHEMISTRY; METALLURGY
C02F2103/325
CHEMISTRY; METALLURGY
C02F2103/007
CHEMISTRY; METALLURGY
C02F1/288
CHEMISTRY; METALLURGY
C02F2103/22
CHEMISTRY; METALLURGY
International classification
Abstract
A method for pretreatment of wastewater or recreational water with substantial reduction of total suspended solids and turbidity in a very short time is provided comprising treatment with nanocomposites and a bridging agent.
Claims
1. A method for pretreatment of wastewater for reduction of total suspended solids (TSS) and turbidity, wherein the wastewater is from olive oil mills, wineries, piggeries, cowsheds, slaughterhouses, fruit and vegetable processing industries, soy or coffee bean industries, bromine industries, dairy effluents, or saline effluents, and includes charged colloidal particles suspended therein, said method consisting of treating the wastewater with: (a) a nanocomposite and (b) a bridging agent, the nanocomposite (a) consisting of: (ai) anchoring particles based on zeolites, diatomaceous earth, powdered activated carbon or aluminium or magnesium silicate clay minerals selected from the group consisting of sepiolite, palygorskite, smectite, montmorillonite, vermiculite, hectorite, laponite, bentonite, or saponite, and (aii) one or more polymers, at least one of said polymers being a cationic polyelectrolyte polymer selected from the group consisting of: poly(diallyl dimethylammonium) chloride (poly-DADMAC), cationic polyacrylamide, poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (PDEE), poly[bis(2-chloroethyl) ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] quaternized (PQ2), poly [(3-methyl-1-vinylimidazolium chloride)-co-(1-vinylpyrrolidone)] (PMVV), chitosan, poly [(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)], quaternized hydroxyethylcellulose ethoxylate, and guar gum, or an anionic polyelectrolyte polymer selected from the group consisting of: a poly(methyl vinyl ether-alt-maleic anhydride) copolymer (PMVE) and a poly(acrylamide-co-acrylic acid) copolymer (PAM); and the bridging agent (b) is selected from the group consisting of: (bi) a cationic polyelectrolyte polymer selected from the group consisting of: polyquaternium 2 (PQ2), polyquaternium 15 (PQ15), polyquaternium 45 (PQ45), and polyquaternium 47 (PQ47); (bii) an anionic polyelectrolyte polymer selected from the group consisting of poly(acrylamide-co-acrylic acid), acrylamide/sodium acryloyldimethyltaurate copolymer, and acrylamide/sodium acryloyldimethyltaurate/acrylic acid terpolymer; or (biii) a nanocomposite consisting of anchoring particles as defined above in (ai) and a cationic polyelectrolyte polymer as defined above in (bi) or an anionic polyelectrolyte polymer as defined above in (bii), whereby said polyelectrolyte polymer (aii) of the nanocomposite (a) neutralizes the charged colloidal particles suspended in said wastewater while anchoring them to the anchoring particles (ai) of the nanocomposite to form small flocks of about 50 to 100 m in size and said bridging agent (b) completes the neutralization and bridges the small flocks to form large aggregates of about 200 to 2000 m in size, thus enhancing their precipitation and achieving a reduction of TSS and turbidity of two orders of magnitude in a time range of less than 5 minutes.
2. The method according to claim 1, wherein the anchoring particles are based on clay minerals selected from the group consisting of sepiolite, palygorskite, smectite, montmorillonite, vermiculite, hectorite, laponite, bentonite, and saponite.
3. The method according to claim 2, wherein the clay mineral is sepiolite or bentonite.
4. The method according to claim 1, wherein the nanocomposite consists of anchoring particles and one, two or three polymers, at least one of which is a cationic or anionic polyelectrolyte polymer.
5. The method according to claim 4, wherein the nanocomposite consists of anchoring particles and one polymer, which is a cationic or an anionic polyelectrolyte polymer.
6. The method according to claim 5, wherein the cationic polyelectrolyte polymer is poly-DADMAC, PDEE, PQ2 or PMVV chitosan.
7. The method according to claim 1, wherein said nanocomposite is selected from the group consisting of poly-DADMAC-sepiolite, poly-DADMAC-bentonite, chitosan-sepiolite, PDEE-sepiolite, PQ2-sepiolite, PMVV-sepiolite, PMVE-sepiolite, and PAM-sepiolite.
8. The method according to claim 1, wherein the bridging agent is a cationic polyelectrolyte polymer selected from the group consisting of polyquaternium 15 (PQ15), polyquaternium 45 (PQ45), and polyquaternium 47 (PQ47).
9. The method according to claim 1, wherein the bridging agent is a nanocomposite consisting of anchoring particles and a cationic or an anionic polyelectrolyte polymer.
10. The method according to claim 9, wherein the bridging agent is the nanocomposite PQ15-sepiolite, PQ45-sepiolite, or PQ47-sepiolite.
11. The method according to claim 1, wherein the wastewater contains negatively charged colloidal particles, the nanocomposite consisting of anchoring particles and at least one cationic polyelectrolyte polymer is added thereto in an amount that causes partial neutralization of the negatively charged colloidal particles and a cationic polyelectrolyte polymer bridging agent is added either together with, or after, the addition of the nanocomposite, to complete the neutralization of the partially neutralized negatively charged colloidal particles while bridging the small flocks formed into large aggregates.
12. The method according to claim 11, wherein partial neutralization of the negatively charged colloidal particles by the nanocomposite with a cationic polyelectrolyte polymer is achieved by adding about 40% to about 90% of the charge needed to neutralize the negatively charged colloidal particles and the cationic polyelectrolyte polymer bridging agent completes the neutralization of the partially neutralized negatively charged colloidal particles while bridging the small flocks formed into large aggregates.
13. The method according to claim 1, wherein the wastewater contains negatively charged colloidal particles, the nanocomposite consisting of anchoring particles and at least one cationic polyelectrolyte polymer is added thereto with a total charge that is higher by about 10% than the charge of the negatively charged colloidal particles suspended in the wastewater, causing formation of positively charged small flocks, which are neutralized and caused to form large aggregates by later addition of an anionic polyelectrolyte polymer bridging agent.
14. The method according to claim 1, wherein the wastewater contains positively charged colloidal particles, the nanocomposite consisting of anchoring particles and at least one an anionic polyelectrolyte polymer is added thereto in an amount that causes partial neutralization of the positively charged colloidal particles and an anionic polyelectrolyte polymer bridging agent is added either together with, or after, the addition of the nanocomposite, to complete the neutralization of the partially neutralized positively charged colloidal particles while bridging the small flocks formed into large aggregates.
15. The method according to claim 1, wherein the wastewater contains positively charged colloidal particles, the nanocomposite consisting of anchoring particles and at least one an anionic polyelectrolyte polymer is added thereto with a total charge that is about 10% higher than the charge of the positively charged colloidal particles suspended in the wastewater causing formation of negatively charged small flocks, which are neutralized and caused to form large aggregates by later addition of a cationic polyelectrolyte polymer bridging agent.
16. The method according to claim 1, wherein the wastewater is from olive oil mills, cowsheds, bromine industries, or saline effluents.
Description
BRIEF DESCRIPTION OF THE FIGURES
(1) The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee.
(2) In the figures and their description below, the following abbreviations are used.
(3) Abbreviations: AM-co-DMAEA, PQ15; BR, PQ15; NC, poly-DADMAC-sepiolite nanocomposite; NCB, nanocomposite suspension based on 30 mg poly-DADMAC per g sepiolite; NC9, nanocomposite suspension based on 40 mg poly-DADMAC per g sepiolite; NC10, nanocomposite suspension based on 60 mg poly-DADMAC per g sepiolite; NC12, nanocomposite suspension based on 100 mg poly-DADMAC per g sepiolite; NC13, nanocomposite suspension based on 120 mg poly-DADMAC per g sepiolite; NC14, nanocomposite suspension based on 160 mg poly-DADMAC per g sepiolite; NC15, nanocomposite suspension based on 200 mg poly-DADMAC per g sepiolite; NC16, nanocomposite suspension based on 240 mg poly-DADMAC per g sepiolite; NC17, nanocomposite suspension based on 320 mg poly-DADMAC per g sepiolite; NC18, nanocomposite suspension based on 400 mg poly-DADMAC per g sepiolite; NC19, NC suspension based on 500 mg poly-DADMAC per g sepiolite; NC21, NC suspension based on 800 mg poly-DADMAC per g sepiolite; NC24, NC suspension based on 1800 mg poly-DADMAC per g sepiolite; NC26, NC suspension based on 2200 mg poly-DADMAC per g sepiolite; NV, poly-DADMAC-bentonite nanocomposite; NH, chitosan-sepiolite nanocomposite; NH6, nanocomposite suspension based on 20 mg chitosan per g sepiolite; NH7, nanocomposite suspension based on 24 mg chitosan per g sepiolite; NH8, nanocomposite suspension based on 30 mg chitosan per g sepiolite; NH9, nanocomposite suspension based on 40 mg chitosan per g sepiolite; NH10, nanocomposite suspension based on 60 mg chitosan per g sepiolite; NH12, nanocomposite suspension based on 100 mg chitosan per g sepiolite; NH13, nanocomposite suspension based on 120 mg chitosan per g sepiolite; NH14, nanocomposite suspension based on 160 mg chitosan per g sepiolite; NH15, nanocomposite suspension based on 200 mg chitosan per g sepiolite; NH18, nanocomposite suspension based on 400 mg chitosan per g sepiolite; NH19, NH suspension based on 500 mg chitosan per g sepiolite; NH21, NH suspension based on 800 mg chitosan per g sepiolite; NZ, AM-co-DMAEA-sepiolite nanocomposite; NZ22, NZ suspension based on 1000 mg AM-co-DMAEA per g sepiolite; OMW, olive oil mill wastewater; PAM, poly(acrylamide-co-acrylic acid) copolymer; PCD, particle charge detector; PD, poly-DADMAC; PD-S9, NC; PDADMAC, poly-DADMAC; PDEE, poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine); PMVE, poly(methylvinyl ether-alt-maleic anhydride) copolymer; PMVV, poly[(3-methyl-1-vinylimidazolium chloride)-co-(1-vinylpyrrolidone)]; poly-DADMAC, polyallyl dimethylammonium chloride; PQ, polyquaternium; PQ2, poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)-propyl]urea] quaternized; PQ15, acrylamide-dimethylaminoethyl acrylate methyl chloride copolymer; PQ45, methacrylamide, methacrylamido propyl trimonium and methacryloylethyl trimethyl ammonium chloride copolymer; PQ47, terpolymer of acrylic acid, methacrylamidopropyl trimethylammonium chloride, and methyl acrylate; S9, sepiolite; Z, PQ15.
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DETAILED DESCRIPTION OF THE INVENTION
(25) The present invention is drawn to the use of a combination of a bridging agent and a nanocomposite comprising anchoring particles and one or more polymers, at least one of the polymers being a polyelectrolyte polymer, for efficient and fast reduction of total suspended solids (TSS) and turbidity in highly loaded organic wastewaters such as olive oil mill, wineries, piggeries, cowsheds, dairy effluents, soy or coffee bean industry, etc, in a very short time.
(26) In one aspect, the present invention relates to a method for pretreatment of wastewater or recreational water with high organic load for fast reduction of total suspended solids (TSS) and turbidity, comprising treatment of said wastewater or recreational water with a nanocomposite and a bridging agent, wherein said nanocomposite consists of anchoring particles and one or more polymers, at least one of said polymers being a polyelectrolyte polymer, and said bridging agent is a polyelectrolyte polymer with low charge density or a nanocomposite consisting of anchoring particles and a polyelectrolyte polymer with low charge density, whereby said polyelectrolyte polymer neutralizes charged colloidal particles suspended in said wastewater or recreational water while anchoring them to the anchoring particles to form small flocks and said bridging agent bridges the small flocks to form large aggregates, thus enhancing their precipitation and achieving a substantial reduction of TSS and turbidity in a very short time.
(27) As used herein, the substantial reduction of TSS is meant to be of at least two orders of magnitude and the very short time is meant to be within the range of seconds to tens of minutes, preferably 0.5 to 10 min, more preferably less than 5 minutes. The method thus achieves a very rapid and efficient pretreatment of the wastewater or recreational water. The terms wastewater or recreational water and effluent will be used herein interchangeably to refer to the water being pretreated.
(28) A very important feature of the method is the formation of large aggregates. Very small colloidal particles suspended in an effluent have very low sedimentation rates and tend to clog filtering devices. Large aggregates sediment and precipitate enabling their separation from the clear liquid. According to the present method, the addition of the nanocomposites generate small flocks of about 50 to 100 m size and the addition of the bridging agent bridges the small flocks to generate large aggregates of about 200 to 2000 m size.
(29) The nanocomposites for use in the method of present invention are composed of anchoring particles and one or more polymers, at least one of which is a polyelectrolyte polymer. The anchoring particles should have the following properties: (i) a size/diameter of less than 0.5 m in at least one dimension, resulting in a large specific surface area; (ii) the ability to adsorb cationic or anionic polymers in strong interactions; (iii) the bulk density of the particles should be larger than the density of the effluents. According to the invention, the anchoring particles may be based on zeolites, diatomaceous earth, powdered activated carbon or aluminium or magnesium silicate clay minerals. In certain embodiments, the anchoring particles are based on clay minerals selected from sepiolite, palygorskite, smectite, montmorillonite, vermiculite, hectorite, laponite, bentonite, or saponite. In certain embodiments, the clay mineral is sepiolite or bentonite. In certain embodiments, the needle-like clay mineral sepiolite is used as the anchoring particle. Its general structure consists of alternating blocks and tunnels that grow in the direction of the fiber (
(30) In certain embodiments, the nanocomposite consists of the anchoring particles and one, two or three polymers, at least one of which is a polyelectrolyte polymer. In certain embodiments, the nanocomposite consists of anchoring particles and one polymer, which is a polyelectrolyte polymer. In certain embodiments, the polyelectrolyte polymer is a polycationic polymer. In certain other embodiments, the polyelectrolyte polymer is a polyanionic polymer. When the nanocomposite comprises more than one polymer, the additional polymer(s) may be a non-ionic polymer such as, but not limited to, polyethylene glycol, cellulose ether, polyvinyl alcohol, polyvinylpyrrolidone, and copolymers containing aromatic units as styrene, for example, styrene-acrylic acid copolymers.
(31) Any polycationic or polyanionic polymer used in effluent treatment may be considered for use in the present invention. Colloidal stability of the effluents is governed by the size of the particles, their density and their charge. Most organic effluents, such as olive oil mill, wineries, piggeries, cowsheds, slaughterhouses, fruit and vegetable processing industry, or soy or coffee bean industry, recreational water such as a coastal beach or a lake, river or pond, contain colloidal particles with a negative charge, and the polyelectrolyte polymer should have positive charges to neutralize the negative charge of the colloidal particles. In addition, the polyelectrolyte polymer should preferably have medium to long chains with the charges dispersed along/throughout such as to allow the bridging of the neutralized colloidal particles between them while anchoring to the anchoring particles. The polyelectrolyte polymer should also be relatively soluble in water to allow its efficient distribution in the effluents.
(32) Thus, according to certain embodiments the polyelectrolyte polymer is a water-soluble polycationic polymer, with medium to long chain (500-5000 monomers) and charges dispersed along/throughout the polymer.
(33) In certain embodiments, the polycationic polymer is selected from: poly(diallyl dimethylammonium) chloride (poly-DADMAC), cationic polyacrylamide, poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (PDEE), poly[bis(2-chloroethyl) ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] quaternized (PQ2), poly [(3-methyl-1-vinylimidazolium chloride)-co-(1-vinylpyrrolidone)] (PMVV), chitosan, poly [(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)], quaternized hydroxyethylcellulose ethoxylate, and guar gum. In certain embodiments, the polycationic polymer is poly-DADMAC, PDEE, PQ2 or PMVV chitosan. In certain embodiments, the polyanionic polymer is a poly(methyl vinyl ether-alt-maleic anhydride) copolymer (PMVE) or a poly(acrylamide-co-acrylic acid) copolymer (PAM).
(34) In certain embodiments the nanocomposite for use in the method of the invention consists of anchoring particles based on sepiolite or bentonite and a polycationic or polyanionic polymer. In certain embodiments, the nanocomposite is selected from poly-DADMAC-sepiolite, poly-DADMAC-bentonite, chitosan-sepiolite, PDEE-sepiolite, PQ2-sepiolite, PMVV-sepiolite, PMVE-sepiolite, or PAM-sepiolite. Examples of ranges of quantitative ratios between the mineral clay and the polyelectrolyte include: (i) poly-DADMAC-sepiolitefrom 3 to 3000 mg/g, 30 to 2400 mg/g, 80 to 1800 mg/g, or 500 to 1000 mg/g poly-DADMAC to sepiolite; (ii) poly-DADMAC-bentonitefrom 3 to 500 mg/g, 30 to 490 mg/g, or 130 to 165 mg/g poly-DADMAC to bentonite; (iii) chitosan-sepiolitefrom 3 to 1200 mg/g, 120 to 1000 mg/g, or 500 to 800 mg/g chitosan to sepiolite; (iv) PMVE-sepiolitefrom 20 to 500 mg/g, 40 to 320 mg/g, or 60 to 100 mg/g PMVE copolymer to sepiolite; and (v) PAM-sepiolitefrom 20 to 500 mg/g, 100 to 400 mg/g, or 200 to 300 mg/g PAM copolymer to sepiolite.
(35) The nanocomposites used in the present invention are identified herein in the Examples and Figures by their abbreviations (see Abbreviations, Brief Description of the Figures), sometimes followed by numerals, which are not quantitative but do indicate qualitatively the amount of the polyelectrolyte polymer in the nanocomposite: the higher the number, the higher the amount of polymer. For example, NC14 contains 160 mg poly-DADMAC per g sepiolite, NC19 contains 500 mg poly-DADMAC per g sepiolite, NC21 contains 800 mg poly-DADMAC per g sepiolite, and NC26 contains 2200 mg poly-DADMAC per g sepiolite.
(36) Some of the nanocomposites have been previously disclosed by the inventor (Rytwo, 2012; Rytwo et al., 2011, 2012, 2013: Rytwo, WO 2012/176190). The nanocomposites PDEE-sepiolite, PQ2-sepiolite, PMVV-sepiolite, PMVE-sepiolite, or PAM-sepiolite are new.
(37) For use as flocculants in wastewater treatment, the right polyelectrolyte should have a low to medium, preferably low, charge density. According to certain embodiments, the bridging agent for use in the present invention is a polyelectrolyte with low charge density, with relatively long branches and relatively separated charges. In certain embodiments, the bridging agent is a polycationic polymer selected from polyquaternium 2 (PQ2) (a polyquaternium with low to medium charge density that is suitable for use both as cationic polymer bound to sepiolite and as the bridging agent), polyquaternium 15 (PQ15), polyquaternium 45 (PQ45), or polyquaternium 47 (PQ47). In certain embodiments, the bridging agent is PQ15. In certain other embodiments, the bridging agent is a polyanionic polymer with low charge density such as poly(acrylamide-co-acrylic acid), acrylamide/sodium acryloyldimethyltaurate copolymer, or acrylamide/sodium acryloyldimethyltaurate/acrylic acid terpolymer.
(38) In certain embodiments, the bridging agent is a nanocomposite consisting of anchoring particles and a low charge density polycationic or polyanionic polymer. In certain embodiments, the anchoring particles are based on sepiolite and the polycationic polymer is PQ15, PQ45 or PQ47, i.e., the nanocomposite is PQ15-sepiolite, PQ45-sepiolite, or PQ47-sepiolite. These nanocomposites are new.
(39) A severe problem in water treatment is the colloidal stability due to rejection between particles with identical charge. Pretreatment of industrial effluents such as olive mill or cowshed dairy wastewater includes therefore the addition of coagulants aimed at neutralizing the colloids and reducing their rejection. The coagulant to be used should have a charge opposite to the effluent's charge: when the effluent is negatively charged, a cationic coagulant should be used; when the effluent is positively charged, an anionic coagulant should be used. In the present invention, the coagulant is the combination of the nanocomposite with the bridging agent.
(40) In accordance with the present invention, complete neutralization of the colloidal effluent can be achieved by selecting the nanocomposite and calculating the dose needed to neutralize a given volume of the effluent by using the method of the invention for determining the type and dosage of a coagulant suitable for pretreatment of a colloidal effluent with high organic load as described hereinafter. In this case, the bridging agent's function will be to bridge the small flocks to large aggregates.
(41) In certain embodiments, complete neutralization is not achieved only by the addition of the nanocomposites and total neutralization of the colloidal particles suspended in the effluent may be achieved in two different ways as schematically shown in
(42) In one embodiment, the effluent is negatively charged, the nanocomposite consisting of anchoring particles and at least one polycationic polymer is added thereto in an amount that causes partial neutralization of the negatively charged colloidal particles and a polycationic bridging agent is added either together with (depicted in
(43) In another embodiment, effluent is negatively charged, the nanocomposite consisting of anchoring particles and at least one polycationic polymer is added thereto with a total charge that is slightly higher, e.g. 110% of the charge of the colloidal particles suspended in the effluent causing formation of slightly positively charged small flocks (inversion of the effluent's charge), which are neutralized and caused to form large and firm aggregates by later addition (30 sec to 2 min) of a polyanionic bridging agent (schematically shown in
(44) In certain embodiments, the effluent is positively charged, the nanocomposite consisting of anchoring particles and at least one polyanionic polymer is added thereto in an amount that causes partial neutralization of the positively charged colloidal particles and a polyanionic bridging agent is added either together with, or after, the addition of the nanocomposite, to complete the neutralization of the particles while bridging the small flocks formed to form large aggregates.
(45) In certain other embodiments, the effluent is positively charged, the nanocomposite consisting of anchoring particles and at least one polyanionic polymer is added thereto with a total charge that is slightly higher, e.g. 110% of the charge of the colloidal particles suspended in the wastewater or recreational water causing formation of slightly negatively charged small flocks (inversion of charge), which are neutralized and caused to form large aggregates by later addition of a polycationic bridging agent.
(46) As mentioned above, in order to overcome the severe problem of colloidal stability due to rejection between particles with identical charge, pretreatment of industrial effluents such as olive mill or cowshed dairy wastewater includes the addition of coagulants aimed at neutralizing the colloids and reducing their rejection. However, the amount and type of coagulant are usually determined by trial-and-error jar tests due to the a lack of an efficient method to evaluate the effluents' charge. The present invention provides a method for the direct evaluation of the efficiency of various types and doses of coagulants. The procedure aims to simply equalize the charges of the colloidal effluents and that of the added coagulant.
(47) An important feature of the method of the invention is that it can be used in continuous processes. For this purpose, a vessel containing a nanocomposite suspension and another containing the bridging agent are installed in a system for pretreatment of wastewater and the suspensions are pumped into the effluent in the calculated dosages as necessary. In the sedimentation tank, the precipitate is removed and the clarified effluent is transferred to a supernatant vessel for further treatment (
(48) Thus, in a second aspect, the present invention relates to a method for determining the type and dosage of a coagulant suitable for pretreatment of a colloidal effluent with high organic load, said method comprising the steps: (i) measuring the concentration of charges in said effluent; (ii) selecting a coagulant of charge opposite to the charge of said effluent and measuring the concentration of charges in said coagulant; and (iii) dosing the volume of coagulant needed to neutralize a given volume of the effluent according to the concentration of charges values determined in (i) and (ii).
(49) An electrokinetic technique based on a streaming current detector (SCD), applied in a PCD instrument, is devised to measure the amount of electrokinetic surface charge directly by combining an electrokinetic SCD probe with titration of a charge-compensating polyelectrolyte. The technique is relatively simple and requires no additional model assumptions. The principle of charge measurement is based on the generation of a streaming potential which is induced by the oscillating movement of a plunger in a polytetrafluoroethylene (PTFE) cell, while gold electrodes placed in the cell record the electrokinetic signal. The surface charge is then quantified by titration with charge compensating polyelectrolytes. Addition of the titration solution is performed across the point of zero charge, i.e., the point at which the electrokinetic surface charge measured by the SCD is zero (Dultz and Rytwo, 2005).
(50) In certain embodiments, measurement of the concentration of charges in the method of the invention for determining the type and dosage of a coagulant is performed by polyelectrolyte titration with a particle charge detector (PCD). Thus, in the method above, measurement of charges and calculations are performed as follows:
(51) in step (i), C.sub.e, the concentration of charges in the effluent in mol.sub.eL.sup.1 is measured by performing polyelectrolyte titration with a particle charge detector (PCD);
(52) in step (ii), the suitable coagulant of charge opposite to the effluent's charge is subjected to PCD measurement yielding C.sub.c, the concentration of charges in the coagulant in mol.sub.cL.sup.1; and
(53) in step (iii), the volume of coagulant (Vc) needed to neutralize a given volume of effluent (Ve) is calculated by the ratios: V.sub.c/V.sub.e=|C.sub.e/C.sub.c|.
(54) Implementation of the method above is described in the Examples hereinafter.
(55) In this method, the selection of the coagulant is correlated to the type of charge of the effluent. Thus, when the effluent is negatively charged, a positively charged coagulant is selected, and when the effluent is positively charged, a negatively charged coagulant is selected. In addition, there is also a correlation between the concentration of charge value of the effluent and the charge degree of the selected coagulant. For illustration only, without being bound to these limitations, it can be established that: (a) when the concentration of the negative charge value of the effluent is within the range 0 to 0.5 mmole L.sup.1, the coagulant is a low positively charged coagulant; (b) when the concentration of the negative charge value of the effluent is within the range from 1 to 3 mmole L.sup.1, the coagulant is a medium positively charged coagulant; (c) when the concentration of the negative charge value of the effluent is within the range from 5 to 9 mmole L.sup.1, the coagulant is a highly positively charged coagulant; and (d) when the concentration of the positive charge value of the effluent is within the range from 0.1 to 3 mmole L.sup.1, the coagulant is a low or medium negatively charged coagulant.
(56) The coagulant selected by this method can be any coagulant used in pretreatment of effluents, both inorganic coagulants such as aluminum sulfate, aluminum chloride, sodium aluminate, ferric sulfate, ferric chloride, ferric chloride sulfate, hydrated lime and magnesium carbonate, and organic coagulants such as natural or synthetic polymers. The coagulant may also be a nanocomposite as described herein comprised of anchoring particles and one or more polymers, at least one of said polymers being a polyelectrolyte polymer.
(57) The methods of the invention can be applied for pretreatment of a variety of wastewater effluents such as, without being limited to, effluents from olive oil mill, wineries, piggeries, cowsheds, slaughterhouses, fruit and vegetable processing industry, soy or coffee bean industry, bromine industry, dairy effluents, or saline effluents from desalination plants, and for pretreatment of recreational water such as a coastal beach or a lake, river or pond or other water sources containing algae or other particulate material that should be removed, separated or aggregated.
(58) The invention will now be illustrated by the following non-limiting Examples.
EXAMPLES
(59) Materials
(60) Olive mill wastewater (OMW) was kindly supplied by Ein Kamonin Olive Mill (Lower Galilee, Israel). Winery effluents were obtained from Galil Mountain Winery (Yiron, Upper Galilee, Israel). Sepiolite S9 (<200 mesh) was obtained from Tolsa S.A. (Madrid, Spain), with 99% pure mineral content. Poly(diallyldimethylammonium) chloride (poly-DADMAC) medium and high molecular weight 200,000 to 350,000 and 400,000 to 500,000, respectively, and chitosan (medium molecular weight, 75-85% deacetylated) were purchased from Sigma-Aldrich (Israel). Polyquaternium 15, Zetag 8848FS, Zetag 8185, ZETAG 4145 were purchased from BASF, Germany. All materials were used without further treatment or purification.
(61) Methods
(62) (a) Analytical MeasurementsElectrokinetic Charge Measurements
(63) Electrokinetic charge of the nanocomposite suspensions and the effluents before and after treatment with the nanocomposites (alone or with a bridging agent) were measured by means of a particle charge detector (PCD; Mtek PCD 03) with an automatic titration unit (Mtek titrator T2) using charge-compensating polyelectrolytes as described by Rytwo et al. (2011). Electrokinetic effects occur whenever there is a distortion of counter ions due to movements of charged particles relative to the surrounding solution, and they are widely used to characterize the charge distribution around colloidal particles in an aqueous solution. Results were normalized to mol.sub.c/g (micromoles of charges per gram) of nanocomposite or to mmol.sub.c/L of effluent, accordingly. All experiments were performed in triplicate.
(64) (b) Analytical MeasurementsHarmonic mean Sedimentation Velocity
(65) The nanocomposites were tested for their influence on the sedimentation rate of olive oil mill wastewater (OMW). Sedimentation velocities were measured by means of a LUMiSizer (6110) instrument. The instrument records the NIR (near infrared) light transmission during centrifugation over the total length of a cell containing the suspension. It automatically determines the time dependence position of the interface panicle-free fluid/suspension or sediment by a special algorithm. The transmission profile enables characterizing the smallest deviations in size of dispersed particles and quantifying the degree of polydispersity at high-volume concentrations. The harmonic mean sedimentation velocity in the first 60 seconds of the process was chosen as a useful parameter to compare between treatments. High sedimentation velocities were measured when fast precipitation was observed. The reason to focus on the first 60 s is because in the efficient treatments, complete clarification was observed after that period of time. Such experiments allow evaluating the efficiency of the wastewater treatment by a very fast and accurate procedure. Profiles were taken every 5 s for 10 min at a relative centrifugal force of 4.98 g (200 rpm). All experiments were performed three times.
(66) (c) Preparation of Nanocomposites Comprising Sepiolite S9 and Poly-DADMAC (NC Nanocomposites)
(67) NC nanocomposites were prepared from sepiolite and poly-DADMAC at loads ranging between 3 and 2400 mg polymer/g clay. Concentrated batches containing 100 g clay/kg (10%) suspension were prepared. To produce the NC nanocomposites, a solution containing the requested amount of polymer was prepared according to the desired amount of polymer per g of clay. As an example, the procedure for the preparation of a 10% stock suspension of 50 g nanocomposite with 100 mg poly-DADMAC/g sepiolite S9 was as follows. The concentrated polymer (poly-DADMAC, usually 40% w/w) was dissolved in a suitable amount of warm water to obtain a final volume of 500 ml containing 5 g of the polymer. The solution was placed in a sonication bath to obtain a homogeneous solution. Upon complete dissolution, the polymer solution was poured into a container with 50 g of sepiolite and agitated vigorously for 2 hours. Preparation was complete when clay aggregates were no longer observed, and the viscosity of the suspension was relatively low. Increased viscosity indicates that the polymer is not well dissolved or that the process is not yet complete, since a 10% suspension of most clay minerals in water (without polymer) yields a paste that cannot be efficiently used.
(68) (d) Preparation of Nanocomposites Comprising Sepiolite S9 and Chitosan (NH Nanocomposites)
(69) NH nanocomposites were prepared as described in Example 1, but at loads ranging between 3 and 1200 mg polymer/g clay. Concentrated batches containing 50 g clay/kg (5%) suspension were prepared.
(70) (e) Preparation of Nanocomposites Comprising Volclay Sodium Bentonite and Poly-DADMAC (NV Nanocomposites)
(71) NV nanocomposites were prepared as described in Example 1, but at loads ranging between 3 and 500 mg polymer/g clay. Concentrated batches containing 20 g clay/kg (2%) suspension were prepared.
Example 1
Treatment of Olive Oil Mill Wastewater with a Calculated Dosage of Nanocomposite/bridging Agent Suspension
(72) OMW pretreated in an anaerobic digester was tested in order to determine the dosage of coagulant. The outflow was very rich in colloidal material (total suspended solids (TSS)=1600 mg L.sup.1, turbidity=973 NTU). Coagulation was performed with increasing doses of a 2.5% suspension of NC21Z, a coagulant based on nanocomposites comprised of 0.8 g polyDADMAC (PD) per g sepiolite clay with addition of 10 g/L of polyquaternium 15 (PQ15) bridging agent.
(73) The effluent and coagulant/bridging agent charges were measured by means of a PCD (Mtek PCD 03) with an automatic titration unit (Mtek titrator T2) using charge-compensating polyelectrolytes as described in Method (a) above. Results were normalized to mol.sub.c/g (micromoles of charges per gram) of nanocomposite or to mmol.sub.c/L of effluent, accordingly. TSS concentration was determined by filtering 1-5 ml of the sample trough a 47-mm glass fiber membrane (Sartorius Stedim Biotech GmbH) with a pore diameter of 0.45 m, and drying at 105 C. for 1 h. Turbidity was measured with a LaMotte 2020i turbidimeter. All experiments were performed in triplicate.
(74) The results are shown in Table 1 and
(75) TABLE-US-00001 TABLE 1 Charge, TSS and turbidity of OMW (initial charge of 1900 mol L.sup.1) treated with increasing amounts of NC21Z 2.5% nanocomposites and PQ15 with an initial charge of +89000 mol L.sup.1). Final Volume of Effluent NC21Z Evaluated concen- NC21Z turbidity Measured evaluated remaining tration suspension after effluent added charge of of NC21Z added treatment charge charge OMW [ppm] ml L.sup.1 NTU mol.sub.c L.sup.1 0 0 973 1900 0 1900 100 4 305 1400 356 1544 200 8 146 1000 712 1188 300 12 88 650 1068 832 500 20 28 180 1780 120 750 30 120 450 2670 770 1000 40 278 1300 3560 1660
(76)
Example 2
Treatment of an Effluent Containing Algae with a Calculated Dosage of Nanocomposite/bridging Agent Suspension
(77) A sample of an effluent containing algae was tested for clarification. The charge of the untreated effluent was 900 mol.sub.c L.sup.. Applying coagulant NC21Z 2.5% suspension at different doses ranging from 0 to 400 L coagulant suspension per 50 mL of algae effluents (equivalent to 0-1400 mol.sub.c L.sup.1) it was found that efficient clarification was obtained at an added volume of 50 L coagulant (equivalent to +890 mol.sub.c L.sup.1). At lower or higher added amounts, less efficient effect was obtained. The results in
Example 3
Treatment of Olive Oil Mill Wastewater with Calculated Dosages of Various Nanocomposites/bridging Agent Suspensions
(78) The feasibility of method described in Example 1 was tested in highly charged raw OMW (initial charge of 5400 mol.sub.c L.sup.1) treated with 5% suspensions of three different nanocomposites: (i) NH21 (low charge based on 800 mg chitosan per g sepiolite), (ii) NC19 (medium charge based on 500 mg poly-DADMAC per g sepiolite) and (iii) NC26 (high charge based on 2200 mg poly-DADMAC per g sepiolite) to which 10 g/L of PQ15 emulsion was added, thus forming the coagulants NH21Z, NC19Z, and NC26Z, respectively.
(79) TABLE-US-00002 TABLE 2 Charges and calculated doses of coagoflocculant required to neutralize highly charged OMW Needed volume of Charge coagoflocculant (mmol L.sup.1) (ml L.sup.1) raw OMW 5.2 Low-charge coagoflocculant 63.5 81.9 (NH21Z) Medium-charge coagoflocculant 124 41.6 (NC19Z) High-charge coagoflocculant 589 8.8 (NC26Z)
(80) It can be seen from
Example 4
Treatment of OMW Effluents with a Nanocomposite, a Bridging Agent, or a Nanocomposite/bridging Agent Combination
(81) OMW was treated with: (i) nanocomposite NC26 (NC), (ii) bridging agent PQ15 (BR), or (iii) a combination of both (NC/BR), by adding: (i) 0.4 ml L.sup.1 of the 5% NC suspension; (ii) 2 ml L.sup.1 of the 2% BR) suspension; (iii) 0.4 ml L.sup.1 of the 5% NC suspension and 0.8, 1.2, 1.6, 2.0 or 2.8 ml L.sup.1 of the 2% BR suspension. The particle size of the flocks obtained after each treatment was measured with a Mastersizer laser diffraction particle sizing instrument.
(82) The combination of the nanocomposites with the bridging agent increased also the velocity of the process, i.e., the formation of aggregated flocks. Olive oil mill wastewater (5 ml L.sup.1) was treated with various combinations of NC/BR in which the amount of the polymer per g clay varied in the NC with 2% BR suspension (NC100+BR, NC160Z+BR, NC320+BR, NC400+BR, NC600+BR and NC1000+BR) or without adding the BR suspension (NC100, NC160, NC320, NC400, NC600 and NC1000) and light transmission was measured 1 minute after addition of the coagulant at a relative acceleration force of 5 g. As shown in
Example 5
Treatment of Cowshed Effluents with a Nanocomposite, a Bridging Agent, or a Nanocomposite/bridging Agent Combination
(83) Cowshed effluents were treated with NC26 (NC), PQ15 (BR) or a combination of both (NC+BR). It can be clearly observed from
Example 6
Comparison of Various Treatments of Effluents on Flocks Stability
(84) 6.1 Cowshed Effluents
(85) In order to compare the efficiency of the treatment according to the present invention and of regular treatments, and also to evaluate costs, three possible options were tested on cowshed effluents: (i) NCNanocomposites/bridging agent (NC21Z, based on 2.5% sepiolite suspension, 800 mg commercial poly-DADMAC per g clay, and 1% w/w commercial Zetag 8848FS as a bridging agent); (ii) ALsolution of 40% aluminum sulfate (+108,000 mol.sub.c L.sup.1); (iii) PDsolution of 10% commercial poly-DADMAC (+620,000 mol.sub.c L.sup.1) (Magnafloc LT 35 (40% solution) diluted 1:4.
(86) The first experiment aimed to obtain the optimal dose for each treatment. Three different coagulants and flocculants were added at doses equivalent to 25, 550, 100, 125 and 200% of those required to neutralize the colloids in 10 ml effluents. Measurements were performed with a LUMiSizer dispersion analyzer, at 200 RPM (equivalent to 5 g centrifugal acceleration). In order to measure the efficiency of the clarification, light transmission through the upper 70% of the test tube was measured after 30 and 150 s (equivalent to 2.5 and 7.5 min at normal gravity). Raw cowshed effluents (CW) were treated with NC21Z coagulant (NC), aluminum sulfate (AL) or commercial polyDADMAC (PD). It can be seen from
(87) According to the results, the following optimal treatments were chosen for the next experiment: nanocomposites/bridging agent (NC) at 16 mL/L, alum (AL) at 2.0 ml/L and commercial PD (PD) at 0.6 mL/L Table 3 shows the evaluated cost of the three chosen treatments. All cost evaluations were performed based on the retail cost in Israel of the raw materials for each treatment. It can be seen that all costs are of the same order of magnitude: the alum treatment is the cheapest whereas the proposed nanocomposites/bridging agent (NC) treatment is cheaper than commercial PD application at the efficient doses.
(88) In another experiment, the chosen doses were added to the cowshed effluents in 50 ml test tubes. After mixing the coagulant with the effluents, and waiting for ten minutes to allow spontaneous sedimentation, turbidity of the cleared effluents was measured.
(89) TABLE-US-00003 TABLE 3 Comparative results for the clarification of cowshed effluents, before and after filtration through a 212 m screen before filtration after 212 m filtration price turbidity turbidity TSS VSS COD /m.sup.3 (NTU) (NTU) (mg/L) (mg/L) (mg/L) raw not filtered 2200 4480 5463 raw filtered 1510 2900 1620 1520 NC21Z 2.5%, 16 ml/L 1.36 11 10 73 33 60 Alum 40%, 2 ml/L 1.00 19 1480 3630 1840 1790 PD 10%, 2.4 ml/L 1.73 44 807 3230 1880 1160
(90) The experiment described above demonstrates that only the use of nanocomposites/bridging agent yields the formation of large and stable enough flocks that allows separation by simple filtration with a large pores screen. Considering that the cost of the treatment is similar, the advantage of nanocomposites/bridging agent is obvious.
(91) Similar results were obtained with various effluents as summarized in Table 4. In all cases a suitable amount of coagulant was added and after 2-10 min effluents were filtered through a 200 micron screen.
(92) TABLE-US-00004 TABLE 4 Summary of effluents tested with combinations of nanocomposites and bridging polymers Percent Number of removed samples Before treatment TSS COD Effluent tested TSS (mg/l) COD (mg/l) (%) (%) Winery >200 1000-2500 3000-20000 93-99 10-30 Olive mill >200 6000-50000 15000-70000 90-98 25-60 Algae 10 500-5000 ND 97-99 ND Dairy 5 1000-4000 1000-12000 95-99 20-60 Cowshed 12 2000-20000 3000-15000 96-99 65-95 ND = not detected
6.2 Olive Oil Mill Wastewater
(93) A cost evaluation on cowshed effluents is presented in Table 3 above. OMW is a considerably more difficult to treat effluent. OMW was treated with 2.5% NC26 suspension, NC26Z (NC26 nanocomposite with 10 g/L of PQ15 (commercial inverse emulsion), an alum solution, and commercial PD (FL45) (data not shown). In all cases the dose chosen was the dose that yielded the best effect after 15 minutes (whereas for NC26Z the effect was obtained almost immediately). It can be seen from Table 5 that even at retail prices the use of this method is cost effective when compared with other, considerably less effective, treatments.
(94) TABLE-US-00005 TABLE 5 Cost evaluation for the treatment of OMW price /m.sup.3 NC26 5%, 5 ml/L 4.28 NC26Z 5%, 5 ml/L 4.83 Alum 40%, 46 ml/L 23.00 FL45- PD 40%, 2 ml/L 5.76
Example 7
Fast Sedimentation Obtained by Using a Combination of Nanocomposites in Excess and an Oppositively Charged Bridging Agent
(95) OMW effluents after bioreactor COD reduction with TSS=3220 mg/L, turbidity >600 NTU and an initial charge (measured with a PCD)=1130 mmol.sub.c/L were treated by adding nanocomposites in slight excess followed by addition of a bridging agent with an opposite charge from the nanocomposite. Based on the charge of the nanocomposites according to the method of the invention, efficient charge neutralization should be obtained using, for example, 54 L of a 5% suspension of nanocomposite NC19 with a charge of +215000 mmole.sub.c/L per 10 mL of OMW effluents.
(96) The experiment was performed as follows: to raw OMW effluent (10 mL) a 5% NC19 suspension (60 L) was added. The test tube was stirred in a vortex for 10 s, followed by addition of a 10% analytical PAM (p) solution (0-30 L), which at neutral and basic pHs (>5.5) is slightly negatively charged. It can be clearly observed from
(97)
(98) It can be seen from
Example 8
Clarification of OMW Effluents and Flocks Stability Using Nanocomposites and Either a Positively or Negatively Charged Bridging Agent
(99) The present example shows an additional aspect of the improved performance obtained according to the present invention. OMW effluents having a charge of 1130 mmole.sub.c/L were tested for the stability of flocks and possible filtration after treatment with a 5% nanocomposite suspension based on NH21 with a charge of 157000 mmole.sub.c/L. For neutralization of 10 ml of OMW effluents, 74 L of NH21 are needed. Raw OMW effluent (blank) and three treated OMW samples (10 ml) were compared: neutralization with 75 L NH21 (NH), NH/PQ (60 L NH21 suspension (underdose) and 100 L of 1% positively charged PQ15), and NH/PAM (90 L (overdose) of NH21 suspension with subsequent addition of the negatively charged PAM (15 L of a 10% PAM suspension)).
(100) It can be seen from
(101) Another advantage of using nanocomposites with a bridging agent can be observed after filtering the treated samples (10 min after) through a 70 mesh (212 m) screen. As can be seen from
(102) TABLE-US-00006 TABLE 6 Comparative results for the clarification of OMW effluents, before and after filtration through a 212 m screen clarified total TSS (mg/L) effluents TSS (mg/L) after 212 m before filtration filtration blank 2720 2100 NH21 5% 75 L 50 1330 NH21 5% 60 L + PQ15 55 75 NH21 5% 90 L + PAM 60 85
Example 9
Clarification of Piggery Effluents Using Nanocomposites or a Combination of a Nanocomposite and a Bridging Agent
(103) The efficiency of nanocomposites for the TSS removal was tested on piggery effluents (from Lahav Piggery, Israel) from two different sources: (a) effluents sampled from the sedimentation pond, and (b) effluents sampled from the fattening area. As a preliminary measurement in order to evaluate the amount and type of a nanocomposite needed to perform an efficient treatment, charge measurements were performed as described in Method (a) above. The doses needed for neutralization of piggery effluents with a NC24 2.5% nanocomposite suspension based on 2.5% S9 sepiolite and 1800 mg PD per gram clay are summarized in Table 7. A commercial formulation consisting of an inversed emulsion of PQ15 at 0.25% concentration was used as a bridging polymer (BP).
(104) TABLE-US-00007 TABLE 7 Calculated needed doses of NC24 nanocomposite for the clarification of piggery effluents Piggery Neutralization effluents Average charge Std dev dose of NC24 2.5% source (mol.sub.c L.sup.1) (%) (mL L.sup.1) Sediment pond 4987 2.65% 14.5 Fattening area 2527 3.56% 7.3
(105) Table 8 shows results for treatment of piggery effluents from two sampling sites with NC24 nanocomposite (Examples 9.3-9.4, and 9.13), with bridging agent PQ15 alone (Examples 9.2 and 9.7), or with various combinations of NC24 and PQ15 (Examples 9.5, 9.8-9.12). In Examples 9.3 and 9.13 the exact dose of the NC24 nanocomposite was added for the neutralization of the effluents, and the samples were allowed to sediment for about 30 min. Measurements were performed from the supernatant (S*). In Examples 9.7-9.12 the influence of the dose of NC24 nanocomposite was tested at the same BP dose. The samples were screened through a 200 m filter, except for the samples of Examples 9.3, 9.11 and 9.13 which were allowed to sediment for 30 min and TSS and COD were measured in the supernatant.
(106) TABLE-US-00008 TABLE 8 Results for treatment of piggery effluents from two sampling sites NC24 BP TSS COD dose dose Filter percent percent Site (ml/L) (ml/L) (m) ppm removed ppm removed Example 9.1 sediment raw 1890 5103 Example 9.2 0 50 200 1540 18.5% 4333 15.1% Example 9.3 4 S* 117 93.8% 1810 64.5% Example 9.4 4 50 478 74.7% 1889 63.0% Example 9.5 0 50 200 400 78.8% 1709 66.5% Example 9.6 fattening none 1261 5128 Example 9.7 0 40 200 950 24.7% 4329 15.6% Example 9.8 1.5 40 200 257 79.6% 3488 32.0% Example 9.9 3 40 200 243 80.7% 2907 43.3% Example 9.10 4.4 40 200 287 77.2% 2885 43.7% Example 9.11 5 40 S* 107 91.5% 3316 35.3% Example 9.12 6 40 200 450 64.3% 2714 47.1% Example 9.13 7 S* 95 92.5% nd S* = supernatant
(107) In conclusion: (i) TSS removal is slightly worst (80-90%) than with other effluents (>95%, Table 4 above). However, when no filtration was applied, TSS values were considerably lower (100 ppm), indicating that sedimentation of the flocks might be the most effective procedure for clarification of those effluents. (ii) COD removal is similar to the observed in cowshed (40-70%). Samples from sediment site yielded better COD removal. (iii) Bridging agent alone did not yield significant reduction in TSS and COD. (iv) Addition of the suitable amount of NC24 nanocomposite alone followed by filtration through a 50 m filter (Example 9.4) did not deliver the same efficiency as the sedimentation (Example 9.3), indicating existence of either smaller or less stable flocks. (v) In cases where the bridging agent was used, high nanocomposite doses (80%) were worse than a suitable range (20-60% of the needed for full neutralization). With no bridging polymer100% neutralization with sedimentation or fine filtering delivered very good results.
Example 10
Use of Nanocomposites for the Removal of Suspended Material in Saline Effluents, Feed Water and Brine from Desalination Facilities
(108) Use of desalination processes is expected to increase constantly. Colloidal material in the feed of desalination facilities is caused mainly by clay minerals covered by organic materials and surfactants, thus pretreatment influences cost efficiency of desalination. The brine contains also remaining coagulants, antiscalants, and all the colloidal material removed from the feed water and accumulated in the filters.
(109) Saline wastewater from industries as pickles or canned vegetables, fish and meat, is usually characterized by low pH (3.5-6), high salt content (mainly NaCl 2500-14000 mg/L) and high concentrations of dissolved and suspended solids, composed mostly of organic matter.
(110) In the present example the ability of nanocomposites to reduce suspended solids in high salt concentration water was tested, in order to check the feasibility of the use of such coagulants for the pretreatment of saline industrial effluents, desalination pretreatment, and desalination brine suspended material removal before rejecting the brine back to the sea.
(111) Polluted saline effluents were synthetically prepared by mixing Mediterranean Sea water with 10% (by weight) cowshed effluents. The final effluents were measured for turbidity (>800 NTU) and TSS (600 mg/L).
(112) The procedure described in the method of the invention for determining the type and dosage of coagulant cannot be applied in such high salt concentration liquids due to the very low absolute value of electrokinetic potential caused by the very high ionic strength. Thus, direct clarification trial and error experiments were performed using the LUMisizer dispersion analyzer.
(113) The experiments were performed using (i) nanocomposite suspensions based on 5% sepiolite clay and amounts of polyDADMAC ranging between 0.02-0.5 g polymer per g clay (denoted as NC6 up to NC19); or (ii) nanocomposites based on 5% sepiolite clay and amounts of the cationic biopolymer chitosan ranging between 0.02-0.4 g polymer per g clay (denoted as NH6 up to NH18). In both cases, a constant dose of 10 mL coagulant suspension per L effluents was used.
(114)
(115)
(116) In order to perform an optimization of the dose, NH18 (5% sepiolite with 0.4 g chitosan per g clay) was applied at doses ranging from 5 to 35 ml suspension per L effluent.
(117) The results demonstrate the ability of nanocomposites to clarify saline effluents even at a level of 30-35 g/L dissolved salts. It is interesting to note that nanocomposites that were very effective in fresh water (sepiolite+poly-DADMAC) did not deliver any clarification in saline effluents. We assume that the inefficiency of the NC particles is caused by the high Cl.sup. concentration influencing differently the charge of the quarternary ammonium groups that are in a different configuration in both polymers (polyDADMAC and chitosan).
Example 11
Treatment of Bromine Industries Effluents
(118) The efficiency of the method of the present invention in pretreatment of saline bromine industries effluents was tested. Twenty five samples of bromine industries effluents, from 5 consecutive days (24-28/6/2014) at 5 sampling hours each (8:00, 12:00, 16:00, 18:00, and 22:00) were received (source in Israel) and treated. All samples contained very high salts content (0.5-2% Na, 0.5-1.5% Cl and 0.3-1.0% Br, etc.).
(119) Most sample bottles received contained clear effluents with a sediment at the bottom. A few samples contained partly turbid effluents with sediment at the bottom. Part of them contained very large and strong flocks that did not break when agitating the bottles. Initial turbidity of all effluents after agitation was very high (>1500 NTU), and turbidity remained stable for at least 3 h. Due to the high salinity the zeta potential of the effluent is close to zero, thus reducing considerably the sensitivity of the charge-measurement technique to determine doses. Thus, efficient treatments were evaluated by performing a preliminary measurement with the LUMisizer instrument.
(120) The treatments were performed as follows: (1) A low dose of (2 ml/L) NC26 5% (50 g/L sepiolite combined with 2.2 g polyDADMAC per g clay) was added to an effluent to surely obtain positively charged colloids, followed immediately by a dose of 20 ml/L of a commercial poly-acrylamide co acrylic acid anionic compound (ZETAG 4145 by BASF) 0.2% solution added as a bridging polymer/agent (BP). Flocks were formed immediately (5-10 s), occupying 10-30% of the volume. Initially, due to the agitation technique and introduction of air into the flocks most of the flocks floated. However, after a few hours they sank. Separation was performed with a 200 microns screen. (2) A dose of 20 ml/L NH24P 2.5% (25 g/L sepiolite combined with 1.8 g chitosan per g clay) was added to effluents and formed large and nice flocks without the need of addition of a bridging polymer. Flocks were formed slightly slower than in (1) above but still were formed very fast (15-30 s), occupying 20-50% of the volume. As above, initially most of the flocks floated, but after a few hours they sank. Separation was performed with a 100 microns screen. The smaller holes screen was chosen due to the fact that no bridging polymer was used and small flocks were formed. (3) Both tests above were compared with one dose of 2.8 ml/L of alum 50% solution (the regular treatment), followed by the same dose of BP solution mentioned above (20 ml/L). Flocks were formed similar to above (15-30 s), occupying 20-50% of the volume. All flocks were sedimented in a few minutes. Samples were also filtered with a 200 microns screen, for comparison with treatments (1) and (2).
(121) In Table 9 below the parameters are reported in classes of:
(122) Turbidity: None: >5 NTU; very low: 5-10 NTU; low: 10-20 NTU; medium-low: 20-30 NTU; medium: 30-50 NTU; medium-high: 50-75 NTU; high: 75-150 NTU; and very high: >150 NTU.
(123) Sludge Volume Index (SVI) after Filtering: None: no noticeable sludge; low: <5% of the total volume; medium: 5-10% of the total volume.
(124) Results and Conclusions:
(125) ALUM+BP: (a) The regular treatment of alum+BP formed flocks fast with high density that sank, occupying 30-50% of the volume, and leaving in all tested cases a clear supernatant, but a thick sludge. (b) Filtering of the treated effluents was in about 75% of the samples partially ineffective since the formed flocks were broken partially when passing the filter, and in some cases 10% of the filtered volume was occupied by flocks. In about 20% of the samples the turbidity increased considerably due to the disintegration of a part of the flocks while filtering. After waiting for 1-2 h, the floccs sank, and the sample was clarified, but the SVI was relatively high, imposing for high TSS.
(126) Chitosan Based Nanocomposites (NH24P) without Addition of BP: (a) in this treatment the flocks were formed fast without adding BP. Flocks floated at the beginning and after a few hours they sank. This effect can be controlled by a slower mixing (introducing less air to the flocks). (b) Filtering of the treated effluents in almost all the samples was partially ineffective: the formed flocks broke partially passing the filter, whereas in most cases less than 5% of the filtered volume was occupied by flocks. In some (1 or 2) of the samples the turbidity was increased, but only to values below 50 NTU.
(127) Regular (polyDADMAC) Based Nanocomposites (NC26) Followed by an Addition of a Bridging Polymer (BP): (a) In this treatment the flocks were formed very fast. Floccs floated at the beginning and after a few hours sank. The floating effect can be controlled by a slower mixing (introducing less air to the flocks). (b) Filtering of the effluents in almost all the samples was very effective: almost no flocks passed. Only in three cases traces of flocks passed through the filter. In some of the samples (1 or 2) turbidity increased, but only to values below 50 NTU.
(128) In summary, a treatment with a combination of nanocomposites and a bridging agent (NC+BP) ensured efficient reduction in turbidity and sludge content in a wide range of saline effluents from bromine industry. Other treatments as (alum+BP) or chitosan based nanocomposites without a bridging polymer exhibited a very efficient treatment in some cases, but failed in others.
(129) TABLE-US-00009 TABLE 9 Bromine effluents treated with NH24P, NC26 + BP, and Alum + BP SVI-sludge volume Turbidity (class) percentage (class) Sample NH24P NC26 + BP Alum + BP NH24P NC26 + BP Alum + BP day hour filtered filtered filtered filtered filtered filtered 24 08:00 low no very high medium no low 12:00 very low no medium medium no no 16:00 no medium high no low no 18:00 no medium- low low low low low 22:00 no medium- medium- low no low low low 25 08:00 no no medium- low no medium low 12:00 no very low low low no low 16:00 no no low low no low 18:00 very low very low low medium no medium 22:00 no very low very low medium no low 26 08:00 no no very high low no medium 12:00 very low no medium medium no medium 16:00 no no medium- medium no low low 18:00 very low no medium- medium no no low 22:00 very low no low medium no no 27 08:00 no no low no low low 12:00 no no medium- low no low low 16:00 low no medium- medium no no low 18:00 very low no medium- medium no no high 22:00 very low no medium- no low low high 28 08:00 no no medium medium no low 12:00 medium no medium medium no low 16:00 medium- no medium- medium no low low low 18:00 very low no medium- medium no no low 22:00 no no medium- medium low low low
Example 12
Application of a Combination of a Nanocomposite and a Bridging Agent in a Continuous System
(130) This example shows that the method for pretreatment of wastewater according to the present invention can be performed in a continuous system.
(131) The idea of the sedimenter (12) is to allow the denser flocks to remain at the bottom of a vessel, while the clear supernatant flows to another vessel. The whole process is continuous and was tested with piggery, cowshed and winery effluents. Doses were determined with the evaluation techniques described in Example 6 above (Rytwo et al., 2014), while the control of the doses was performed by the injection rate of pumps (9) and (11) in relation to flow rate of pump (6).
(132) For piggery effluents, the main effluents pump (6) worked at 135 ml min.sup.1. The nanocomposite used was a relatively dilute suspension of NC24 (containing 0.5% sepiolite and 1.8 g poly-DADMAC per g clay) and was injected at a rate of 4 ml min.sup.1. The bridging polymer used consisted of a commercial inversed emulsion of PQ15 at 0.25% concentration, and was injected at 8 ml min.sup.1.
(133) For cowshed effluents the experiment was performed similarly with slightly different characteristics: the main effluents pump (6) worked at 90 ml min.sup.1. The nanocomposite used was the same as in the piggery effluents experiment, and was injected at a rate of 3 ml min.sup.1. The bridging polymer used consisted of a commercial solid polyacrylamide-quarternary ammonium co-polymer at 0.05% concentration, and was injected at 5 ml min.sup.1.
(134) The concentrated winery effluents had very high TSS and COD but relatively low charge. Thus, the experiment was performed as follows: the main effluents pump (6) worked at 90 ml min.sup.1. The nanocomposite used was a dilute suspension of NC17 (containing 0.5% sepiolite clay and 0.32 g poly-DADMAC per g clay) and was injected at a rate of 4.5 ml min.sup.1. The bridging agent used was the same as in the cowshed effluents, i.e. a commercial solid polyacrylamide-quarternary ammonium co-polymer at 0.05% concentration, and was injected at 5 ml min.sup.1.
(135) Table 10 below summarizes the results obtained for all samples mentioned above before (raw) and after treatment with a combination of a nanocomposite and a bridging agent in a continuous system (supernatant). As can be seen, very good (more than 95%) TSS removal was observed for all cases. COD removal for piggery and cowshed effluents were also impressive in this case, even though we should emphasize that the main advantage of our invention is TSS removal and COD reduction is only a by-side effect, depending strongly on the ratio between particulates and dissolved organic pollutants in the effluents.
(136) TABLE-US-00010 TABLE 10 Results for treatment of piggery, cowshed and winery effluents with a combination of a nanocomposite and a bridging polymer in a continuous system TSS COD percent percent Effluent Sample ppm removed ppm removed 1 Piggery raw 2833 4760 2 supernatant 165 94.2% 1210 74.6% 3 Cowshed raw 4070 6890 4 supernatant 65 98.4% 900 86.9% 5 Winery raw 15550 12000 6 supernatant 485 96.9% 8030 28.0%
Example 13
New Nanocomposites Consisting of Anchoring Particles and High/medium or Low Charge Density Cationic Polyelectrolyte
(137) In order to emphasize the possibility of preparing additional nanocomposites, comparing them with a bridging agent, and even using two nanocomposites together (one as coagulant and the other as bridging agent), a series of polymer-sepiolite sepiolite combinations was prepared. All new nanocomposites were tested for the clarification of raw cowshed effluents (Kfar Blum Cowshed (IL) collected during July 2014). In all examples the bridging polymer/agent (BP) used was a 0.5 g L.sup.1 suspension of a commercial solid copolymer of acrylamide and quaternized cationic monomer (Zetag 8185, BASF, Germany). The following parameters were measured on the clarified effluents: (a) turbidity 30 m and 3 h after application; (b) COD; (c) total N; and (d) chlorine concentration.
(138) Charge of the effluents and of the nanocomposites suspensions was also measured in order to evaluate the amounts of coagoflocculant needed to achieve an efficient clarification according to the procedure described in Example 1.
(139) 13.1 Raw Effluents and the Use of a Bridging Polymer/agent (BP) Only
(140) In order to test the efficacy of a bridging agent alone on the clarification of raw cowshed effluents, the same doses of 20 ml BP suspension were added. As can be seen from Table 11 below, the addition of BP did not influence the COD or total N values. Due to the relatively low charge of the bridging agent, volumes needed for neutralization are very large, making such neutralization not possible. Thus, even though a considerable reduction in turbidity was observed, values are still very high. A contribution of Cl and P by the bridging polymer was observed. Such contribution is indeed very interesting, since the Cl coming from BP seem to be bound to the flocks made by the added nanocomposites (see the results below).
(141) TABLE-US-00011 TABLE 11 Cowshed effluents treated with 20 ml BP only. Parameter Units Raw BP 0.05% Charge mole.sub.c L.sup.1 2.9 9.8 Concentration needed for ml L.sup.1 296 neutralization Cl mg L.sup.1 2740 3330 Added nanocomposite ml L.sup.1 Added BP ml L.sup.1 20 COD mg L.sup.1 5809 205 5755 503 Total N mg L.sup.1 164 5 160 7 Turbidity NTU 3100 71 1695 21
13.2 Pretreatment of Raw Cowshed Effluents with Poly-DADMAC (NC) or Chitosan (NH) Based Nanocomposites
(142) In previous examples we presented the use of nanocomposites based on poly-DADMAC or chitosan bound to sepiolite clay. In order to compare with the new proposed nanocomposites, we prepared suspension based on those combinations. The nanocomposites were applied to the cowshed effluents with or without the bridging agent. The measured parameters are presented in Table 12 below.
(143) TABLE-US-00012 TABLE 12 Cowshed effluents treated with NC24 or NH19 Parameter Units Raw NC24 1.8 g/g NH19 2.5% 0.5 g/g Polymer PD Chitosan Charge mole.sub.c L.sup.1 2.9 136 53 Concentration ml L.sup.1 21.3 54.7 needed for neutralization without without BP with BP BP with BP Added nano- ml/L 21 17 55 50 composite Added BP ml/L 20 20 Cl mg L.sup.1 2740 3280.0 1990.0 1960.0 2650 COD mg L.sup.1 5809 205 2526 382 2045 114 5694 313 4969 375 % 56.5% 64.8% 2.0% 14.5% removed Total N mg L.sup.1 164 5 141 2 122 3 140 3 139 4 % 14.0% 25.4% 14.5% 14.5% removed Turbidity NTU 3100 71 52 6 54 2 401 15 40 2 after 30 m % 98.2% 98.2% 87.4% 98.7% removed Turbidity NTU 12 1 18 1 48 3 10 3 after 3 h % 99.6% 99.4% 98.5% 99.7% removed
(144) As can be seen from Table 12, addition of NC24 or NH19 nanocomposites removed turbidity almost completely after 3 h. For NC24 the removal was faster and already after 30 m complete clarification was observed.
(145) With respect to the chitosan nanocomposites (NH19) it can be seen from Table 12 that they were not effective in removing COD, whereas NC24 removed about 56% when added alone and the removal of COD was improved even more when NC24+BP. A similar behavior of improved removal with BP was observed for total N with NC24, whereas in NH19 no influence of BP can be seen.
(146) A somehow puzzling difference between nanocomposites was observed for Cl: whereas NC24 alone increased its concentration, an addition of BP reduced chlorine to values lower than in the raw effluents. We assume that CF ions bind to the flocks, and BP enhances such a binding. NH nanocomposites behave differently: it seems that the chitosan itself binds Cl.sup. ions, whereas an addition of BP handicaps such a binding.
(147) 13.3 Pretreatment of Cowshed Effluent with New Nanocomposites with or without a Bridging Agent (BP)
(148) As a next step, nanocomposites suspensions with 1% clay and with a load of 1 g polymer per g clay were prepared for more than 10 cationic and anionic polymers. Charges for the different nanocomposites were measured and ranged from 70 to +110 mole.sub.c L.sup.1. Due to the need to neutralize the negative charge of cowshed effluents, only three new nanocomposites with the highest positive charge were chosen. Thus, nanocomposites were prepared from poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (PDEE); poly[bis(2-chloroethyl) ether-alt-1,3-bis[3-(dimethylamino)-propyl]urea] quaternized (PQ2); or poly[(3-methyl-1-vinylimidazolium chloride)-co-(1-vinylpyrrolidone)], (PMVV).
(149) For easier and more fluid suspensions nanocomposites were prepared as 1% sepiolite suspensions with polymer:clay ratios of 2:1, 1.5:1 and 1:1. The nanocomposite suspensions with approximately similar charge were tested for cowshed effluents clarification. Results are presented Table 13 below.
(150) TABLE-US-00013 TABLE 13 Cowshed effluents treated with nanocomposites based on PMVV, PDEE or PQ2 polymers and 1% sepiolite, herein identified as LQ25, PM23 and P2-25, respectively Parameter Units Raw LQ25 1% 2 g/g PM23 1% 1.5 g/g P2-25 1% 2 g/g Polymer PMVV PDEE PQ2 Charge mole.sub.c L.sup.1 2.9 99.5 120.5 129.5 Concentration ml L.sup.1 29.1 24.1 22.4 needed for neutralization without without without BP with BP BP with BP BP with BP Added nano- ml/L 30 24 25 21 23 18 composite Added BP ml/L 20 20 20 Cl mg L.sup.1 2740 3220 1130 2950 1060 3340 2110 COD mg L.sup.1 5809 205 2528 418 2552 315 2282 101 2393 293 3384 366 3387 43 % 56.49% 56.08% 60.72% 58.81% 41.75% 41.70% removed Total N mg L.sup.1 164 5 129 2 122 1 126 2 123 4 166 5 150 3 % 21.34% 25.36% 23.14% 24.77% 1.58% 8.37% removed Turbidity NTU 3100 71 53 1 57 2 61 6 56 4 52 6 57 2 after 30 m % 97.60% 97.55% 98.05% 98.21% 98.32% 98.16% removed Turbidity NTU 5 1 14 1 26 1 16 3 14 1 12 1 after 3 h % 99.85% 99.58% 99.15% 99.50% 99.54% 99.62% removed
(151) In general the following observations can be made in view of the results presented in Table 13:
(152) (a) As for clarification, all treatments were very effective after 3 h: remaining turbidity in all cases was less than 1%. As for the results after 30 m, the efficacy was also impressive. As mentioned above for NC24 and NH19 it should be emphasized that BP samples (i.e. nanocomposites with bridging agent (BP) clarified the effluent in seconds, and the thickness layer obtained was smaller.
(153) (b) In contrast to the results with NC and NH nanocomposites (Example 13.2 above), addition of BP to LQ25, PM23 or P2-25 nanocomposites did not improve a COD removal. There was a slight difference in the performance of the three nanocomposites, when used alone. PM23 nanocomposites when used without addition of BP exhibited the best COD removal (about 60%). PQ2 exhibited the poorest performance (about 40%), but still was considerably better than NH19.
(154) (c) A similar pattern was observed for removal of total N: as not as in NC, addition of BP did not improve nitrogen removal. The removal by PDEE and PMVV based nanocomposites (PM23 and LQ25, respectively) was similar to the values obtained by NC+BP, whereas PQ2 based nanocomposites (P2-25) apparently did not remove nitrogen at all.
(155) (d) As for Cl removalthe pattern for all three nanocomposites was similar to the observed for NC: an addition of BP lowered the Cl concentration. In PDEE and PMVV based nanocomposites the reduction was even more significant leaving only about 35% of the initial Cl concentration.
(156) To summarize the performance of the new nanocomposites, all three polymers offer very good clarification, and the addition of the bridging agent speeded up the process and increased the Cl removal. PDEE and PMVV based nanocomposites showed very effective COD and total N removal.
(157) 13.4 Pretreatment of Cowshed Effluent with Nanocomposites Consisting of Anchoring Particles and Low Charge Density Cationic Polyelectrolyte
(158) In the present example two additional aspects were tested (a) the use of a polyelectrolyte polymer with low charge density for the preparation of nanocomposites, i.e., nanocomposites consisting of anchoring particles and polyelectrolyte polymer with low charge density, and (b) a combination of two nanocomposites, in which the nanocomposites of (a) are added as a bridging agent.
(159) For the purpose of these experiment nanocomposites (denoted as NZ22) were prepared using sepiolite and 1 g of an acrylamide/dimethylaminoethylacrylate methyl chloride copolymer (AM-co-DMAEA), which can be also used as a bridging agent by itself. The result was a 1% nanocomposite suspension with a relative low charge. Table 14 shows results of cowshed effluents treated with 1% NZ22 only, and with a combination of NC24 and NZ22 in which NZ22 acts as a bridging agent.
(160) TABLE-US-00014 TABLE 14 Cowshed effluents treated with NZ22 or with NC24 + NZ22 Parameter Units Raw NZ22 Polymer AM-co-DMAEA Charge mole.sub.c L.sup.1 2.9 33.6 Concentration ml L.sup.1 86.3 needed for neutralization alone added as a bridging agent after NC24 Added ml/L 90 20 NZ22 1% Added ml/L 20 NC24 1% Cl mg L.sup.1 2740 3470.0 2350 COD mg L.sup.1 5809 205 2570 165 2402 71 % removed 55.75% 58.65% Total N mg L.sup.1 164 5 126 3 122 4 % removed 22.94% 25.18% Turbidity NTU 3100 71 61 2 86 15 after 30 m % removed 98.00% 97.20% Turbidity NTU 41 2 42 3 after 3 h % removed 98.70% 98.70%
(161) As can be seen from Table 14, in all aspects, the combination of NC24 with NZ22 behaved similarly to NC24 with BP (Table 12). One of the disadvantages of using NZ22 alone was the large amount of suspension needed due to the relatively low charge of NZ22. It should be mentioned that the polymer/clay ratio in this case cannot be increased since the viscosity of the suspension makes it already difficult to use. Thus, NZ22 alone will require large doses of coagulant making the treatment relatively expensive.
(162) Combination of NC24+NZ22 appears to be a good treatment, even though clarification obtained was slightly lower than other treatments presented herein.
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