REMOVAL OF BACTERIA FROM DRINKING WATER VIA FILTRATION

Abstract

The present invention relates to a method for producing biocidal, porous particles of a cross-linked polymer, and to the porous particles that can be produced according to the method of the invention. The invention further relates to porous particles of an amino-group-containing polymer (polyamine) having a relatively low swelling factor. The porous particles according to the invention are used to remove biological contaminants from water and to bind metal-containing ions from solutions. The present invention further relates to a filter cartridge which contains the porous cross-linked polymer particles according to the invention.

Claims

1. A method for preparation of biocidal, porous particles from a crosslinked polymer, comprising the following steps: (a) providing an aqueous suspension containing a polyamine, a crosslinker and a porous inorganic substrate in particulate form at a temperature less or equal to 10 C. in a mixer for coating of the inorganic substrates with the polyamine; (b) cross-linking of the organic polymer in the pores of the inorganic substrate and simultaneous removal of water; (c) dissolving the inorganic substrate to obtain the biocidel porous particles of a crosslinked polyamine.

2. The method according to claim 1, wherein the steps (a) and (b) are repeated at least once.

3. A method according to claim 1, wherein the crosslinking is done in a stirred reactor.

4. A method according claim 1, wherein the polyamine is used in the non-desalinated state.

5. A method according to claim 1, wherein the porous inorganic substrate is a material that can dissolve in the aqueous alkaline conditions of pH>10.

6. A method according to claim 1, wherein the polyamine is a polyvinylamine.

7. A method according to claim 1, wherein the crosslinked polyamine according to step (c) is derivatized in its side groups.

8. Biocidal, porous particles from a crosslinked polyamine which are obtainable or prepared according to a method according to claim 1.

9. Biocidal, porous particles according to claim 8, wherein the porous particles have a maximum swelling factor in water of 300% based on 100% dry particles.

10. Biocidal, porous particles according to claim 8, wherein the dry bulk density is in the range of 0.25 g/ml to 0.8 g/ml.

11. Use of biocidal, porous particles according to claim 8 for the removal of biological impurities from water by bringing, for example, the contaminated water into contact with the biocidal porous particles by filtration.

12. The use according to claim 11, wherein the biological impurities are bacteria, germs, yeasts, fungi, or viruses.

13. A filter cartridge containing the biocidal, porous particles according to claim 8.

14. A method of removing biological impurities from water, comprising contacting contaminated with the biocidal porous particles according to claim 8 by filtration.

Description

EXAMPLES

[0055] Analytical Methods

[0056] Determination of the concentration of amino groups of a sorbent with breakthrough measurement with 4-toluenesulphonic acid (titration analysis):

[0057] The dynamic anion exchange capacity is determined with a column of the stationary phase to be tested. At first, for this all exchangeable anions are replaced in the column with trifluoroacetate. Then, the column is purged with an aqueous reagent solution of toluene-4-sulphonic acid until this solution exits in the same concentration at the end of the column (breakthrough). From the concentration of toluene-4-sulphonic acid solution, the flow rate and the area of the opening in the chromatogram, the amount of toluene-4-sulphonic acid bound by the column is calculated. The amount of toluene-4-sulfonic acid thus determined indicates the concentration of the amino groups of the sorbent.

[0058] The dynamic anion exchange capacity for toluene-4-sulfonic acid in water is based on the phase volume and reported in millimoles per liter (mM/1).

Example 1: Preparation of Porous Particles of a Crosslinked Polymer in Accordance with the invention:

[0059] Preparation of Polymer Adsorbate

[0060] 800 g substrate (Grace silica gel SP542-12110) is directly sucked into Ldige VT5. The silica gel is tempered to 10 C. The mixer is operated at a speed of 120 rpm. Then 1133 g of polymer solution PC 16012 (polymer content of 12%) cooled to 10 C. is weighed into a vessel and mixed with 27.5 g EGDGE (ethylene glycol diglycidyl ether). The mixture is added within 2 minutes to the mixer and mixed for 1 hour at 10 C. Subsequently, the polymer adsorbate is dried at 80 C. and 50 mbar (about 2 hrs). Then, the polymer adsorbate was cooled down to 10 C.

[0061] For the second coating, 733 g polymer solution PC 16012 (polymer content of 12%) cooled to 10 C. were weighed into a vessel and mixed with 18 g EGDGE. The polymer solution was filled into the mixing drum within 2 minutes. The polymer adsorbate was mixed for 1 hour at 10 C.

[0062] Subsequently, the temperature in the Ldige was raised again to 65 C. for 1 hour. The polymer adsorbate was mixed with 4 liters of fully desalinate water and the suspension from the Ldige VT was directed into a suction filter. There, the polymer adsorbate was washed with 10 BV of fully desalinated water.

Crosslinking

[0063] 1 liter of sedimented polymer adsorbate is added with 500 liters of fully desalinated water into a 2.5 liter reactor and heated with stirring to 85 C. Subsequently, 125 g epichlorohydrin are added slowly, such that the temperature in the reactor does not exceed 90 C.

[0064] Subsequently, stirring is continued for 20 minutes before 83 g of diaminoethylene are added slowly. After another 20 minutes, a further 125 g of epichlorohydrin are added. Then a further 83 g of diaminoethylene 25 are added. Finally, a further 125 g of epichlorohydrin are added. Then the reaction continues to be stirred for 20 minutes at 85 C. The reaction mixture is then cooled down to 25 C. and 500 mL of 50% NaOH are added and stirring is continued for another hour.

[0065] The template phase is then transferred to a suction filter and washed using the following solvents: [0066] 3 BV 1 M NaOH [0067] 3 BV water [0068] 3 BV 2 M HCl [0069] 3 BV water [0070] 6 BV 1 M NaOH [0071] 6 BV water

[0072] The product is obtained as a moist filter cake.

Example 2: Metal Purification with Simultaneous Removal of Bacteria

[0073] Metal purification attempts according to WO 2017/089523 and WO 2016/030021 were performed with a sorbent according to the state of the art as well as with the above prepared sorbent where the solutions used were contaminated additionally with bacterial strains of Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Staphylococcus. An identical performance is shown for metal purification as for non-contaminated solutions. After purification, however, bacteria could no longer be detected in the purified solution. Biofilm formation failed to materialize as well. However, the conventionally prepared material shows biofilm formation and still large amounts of bacterial strains after filtration. Furthermore, the conventional material loses significantly in capacity probably due to biofilm formation.

[0074] Application Examples (A):

Example A1: Removal of E. coli from drinking water

[0075] Add 7 ml of a solution of E. coli with a bacterial load of OD.sub.600 110.sup.7 CFU/ml with a flow rate of 0.5 ml/min to each of two cartridges (bed volume 7 ml) with bacteriocidal instrAction resin and flush each with 14 ml of water. The eluates are then captured and examined for bacterial load in the following manner:

[0076] The captured fractions are centrifuged for 12 minutes (4500 rpm). The resuspended residue and the surplus are plated on LB Agar. These plates are incubated overnight at 37 C. and the resultant colonies are counted.

[0077] The cartridges are washed overnight at room temperature and at 37 C. and again on the next day with 14 ml (2 BV) of sterile water. The throughput is captured again and is again analyzed for bacteria, as described above. This process is repeated for 4 days. The following table shows the outcome of these investigations:

TABLE-US-00002 TABLE A1 Incubation of E. coli in a 7 ml cartridge filled with BacCap resin at different temperatures. Flow Flow Surplus Wash rate rate wash solution Loaded surplus pellet solution pellet bacteria Residue Bacteria C. (CFU) (CFU) (CFU) (CFU) (CFU) [%] RT 0 0 0 23 1.4 99.9% 37 0 3 0 1 10.sup.7 99.9%

[0078] FIGS. 1 and 2 illustrate the characteristics over a four-day period.

[0079] The 7 ml cartridge, filled with instrAction resin bonds firmly and irreversibly 1.410.sup.7 CFU E. coli over a period of four days regardless of whether or not the cartridge is incubated at room temperature or at 37 C.

Example A2: Removal of Enterococcus faecalis from water

[0080] Add 7 ml of a solution of Enterococcus faecalis with a bacterial load of 3.23.910.sup.8 CFU/ml with a flow rate of 0.5 ml/min to each of two cartridges with bacteriocidal instrAction resin and flush each with 14 ml of water. The eluates are then captured and examined for bacterial load in the following manner:

[0081] The captured fractions are centrifuged for 12 minutes (4500 rpm). The resuspended residue and the surplus are spread onto Blood Agar plates.

[0082] These plates are incubated overnight at 37 C. and the resultant colonies are counted.

[0083] The cartridges are washed overnight at room temperature and at 37 C. and again on the next day with 14 ml (2 BV) of sterile water. The throughput is captured again and is again analyzed for bacteria, as described above. This process is repeated for 4 days. The following table shows the outcome of these investigations:

TABLE-US-00003 TABLE A2 Incubation of E. faecalis in a 7 ml cartridge filled with BacCap resin at different temperatures. Flow Flow Surplus Wash rate rate wash solution Loaded Elution surplus pellet solution pellet bacteria Residue agent C. (CFU) (CFU) (CFU) (CFU) (CFU) [%] E. RT 0 0 0 23 1.4 99.9% faecalis E. 37 0 3 0 1 10.sup.7 99.9% faecalis

[0084] FIGS. 3 and 4 illustrate the characteristics over a four-day period.

[0085] The 7 ml cartridge, filled with instrAction resin bonds firmly and irreversibly 1.410.sup.7 CFU E. faecalis over a period of four days regardless of whether or not the cartridge is incubated at room temperature or at 37 C.

Example A3: Removal of E. coli from Sterile Water and Drinking Water

[0086] Two cartridges are prepared and treated as above, and loaded with E. coli (3510.sup.6 CFU), in one case using sterile water and in the other case using drinking water as a flushing and elution solution. The cartridges are flushed on two consecutive days:

[0087] The following table shows the outcome of this investigation:

TABLE-US-00004 TABLE A3 Removal of E. faecalis from sterile water and drinking water using cartridges filled with BacCap resin. Flow Flow Surplus Wash rate rate wash solution Bacterial Elution resistance pellet solution pellet load Residue agent (CFU) (CFU) (CFU) (CFU) (CFU) [%] Drinking 0 0 0 0 2.9 100% water 106 Sterile 2.9 260 1.3 80 5.5 99.9% water 10.sup.3 10.sup.3 10.sup.6

[0088] E. coli bacteria are retained irrespective of the detergent used (sterile water or tap water).

[0089] FIG. 5 illustrates the outcome over two days for the washing operation with sterile water.

[0090] FIG. 6 illustrates the outcome over two days for the washing operation with tap water.

[0091] The application-related outcomes demonstrate that the quantity of E. coli added to drinking water can be removed safety and completely.

Example A4: Kinetic Investigations of Two InstrAction BacCap T-Resins with Different Particle Sizes in the Batch Process:

[0092] A suspension of 1 ml 110.sup.6 CFU E. coli DH.sub.5alpha in 11 ml of tap water is added to 500 mg of instrAction BacCap resin (batch BV 16037: 100 microns and BV 16092: 425 microns) and is incubated at room temperature on a rotary agitator for 25 hours. At the following intervals, samples are taken and examined with the help of LB Agar plates for colony-forming units: 0, 1, 3, 6, 12 and 25 hours. The outcome of these investigations is shown in FIG. 7:

[0093] Both resins exhibit similar kinetic characteristics in the reduction of bacterial concentration over time, regardless of their particle size.

[0094] This outcome demonstrates that this is a general principle governing the action of instrAction MetCap T resins. The antibacterial action occurs independently of particle size and therefore of the initial silica gel.

[0095] From data, a half-life of approx. 10-15 minutes can be estimated.

Example A5: Comparison with Commercial Resins

[0096] Cation and anion exchangers as well as a blank polystyrene resin are used in the drinking water sector to soften water hardness and to remove pollutants. For this reason, a quartary ammonium anion exchanger and a sulfonated polystyrene cation exchanger and a pure polystyrene are investigated in a comparison with BacCap resins.

[0097] Pure polystyrene proved to be non-wettable with the bacterial suspension and was therefore not examined any further.

[0098] A suspension of 1 ml 110.sup.6 CFU E. coli DH.sub.5alpha in 11 ml of tap water is added to 500 mg of instrAction BacCap resin (batch BV 16092: 425 microns) and an anion exchanger (PRC 15035, 500 microns of sulfonated polystyrene) and an anion exchanger (Lewatit M 800) and incubated at room temperature on a rotary agitator for 25 hours. At the following intervals, samples are taken and examined with the help of LB Agar plates for colony-forming units: 0, 6, 12 and 24 hours.

[0099] The outcome of these investigations is shown in FIG. 8:

[0100] The BacCap material (500 microns) reduces the bacterial concentration within 6 hours by 4 log stages while the simple ion exchanger (sulfonated polystyrene as a cation exchanger and quaternary ammonium to polystyrene as an anion exchanger) shows no signs of a reduction.

[0101] This is in line with the formation of a biofilm known in the literature relating to commercial ion exchangers.

Example A6: Estimation of Capacity

[0102] A suspension of 1 ml 110.sup.6 CFU E. coli DH.sub.5alpha in 11 ml of tap water is added to 50, 100 and 250 mg of instrAction BacCap resin (batch BV 16037: 100 microns) and incubated at room temperature on a rotary agitator for 25 hours. At the following intervals, samples are taken, are plated and then examined for colony-forming units: 0, 6, 12 and 24 hours.

[0103] The data (see FIG. 9) do not exhibit any exhaustion of bacterial removal even when the quantity of resin is reduced drastically. Only a slowing down of the removal of bacteria as a function of the quantity of resin could be observed, dependent on the amount of resin used, when using 50 mg of resin, and this differed from the approaches with 100 and 250 mg of resin. The graph curves for the incubation of 100 mg of resin and 250 mg of resin with a corresponding volume of bacteria are shown directly above one another.