Patent Application
20080257753
This invention relates to a method and apparatus for filtering grey water for recycling purposes, and also to a method of producing a filtering medium and to a filtering medium produced by the method of the invention.
According to a first aspect of the present invention, there is provided a method of filtering grey water for recycling, which comprises passing the grey water to be filtered, through a filter assembly including a support blanket holding a sedimentary material produced by electrolysis of sea water.
A further aspect of the present invention provides a filter assembly including a cylindrical housing, a perforated filter plate and at least one mesh or blanket member supported by the filter plate, which holds a sedimentary material produced by electrolysis of sea water. Preferably the mesh or blanket comprises nylon wadding.
A further aspect of the invention provides a method of producing a filter medium for filtering grey water for recycling, the method comprising subjecting sea water to a process of electrolysis using at least one copper anode, and an iron cathode, whereby a sediment is produced which can be utilised with a suitable support means, to form a filter medium.
In a typical application, a volume of approximately five gallons of sea water is subjected to a potential of 12 volts, which causes a current of 3.5 to 4.5 amps to flow between the electrodes. After about four hours, a sedimentary material is produced, which can be applied to a filter blanket.
A further aspect of the present invention provides a filter medium for filtering grey water comprised of paratacamite, acamite, or botallackite.
A further aspect of the present invention provides a method of filtering grey water for recycling, which comprises passing grey water to be filtered, through a filter assembly including a support mesh or blanket holding paratacamite, acamite or botallackite.
A further aspect of the present invention provides a filter medium for filtering grey water, comprised of (Cu2OH)3Cl.
A further aspect of the present invention provides a filter medium for filtering grey water, comprised of CuCO3 and Cu(OH)2.
A further aspect of the present invention provides a method of producing a filter medium for filtering grey water for recycling, comprising subjecting an aqueous solution containing chloride ions to electrolysis using at least on copper anode.
Some embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in which:
Table 1 sets out the operating conditions for a VG Axiom ICP-MS;
Table 2 sets out the elemental composition of a filter medium, 15 mm domestic copper pipe and seawater electrolyte pre and post electrolysis.
Table 3 sets out a Carbon, Hydrogen and Nitrogen analysis of a filter medium;
Table 4 sets out the main elemental composition of filter medium;
Table 5 sets out a number of surface tension measurements.
Referring firstly to
The upper locating ring 6 is provided with a pair of diametrically opposed, outwardly projecting locating ears 12 which are arranged to form a “bayonet-type” connection with the filter body, by cooperating with suitably formed recesses (not shown) in the inner wall of the filter body.
In order to enable the locating ring to be locked into the body, a pair of inwardly projecting location lugs 14 are arranged at a position which is offset by 90° from the position of the locating ears 12, and each lug 14 is provided with an aperture 16 for inserting one of the legs 18 of an assembly key 20 shown diagrammatically in
The sealing ring 10 preferably has a resilient or spring-like structure, so that the locating ring 6 can be locked down, by means of its locating ears, and the sealing ring 10 will then hold it resiliently in position.
Wads of nylon mesh 22 are also packed into the filter body, above and below the perforated filter plate, so as to provide a support for a filtering medium, as explained in more detail below.
The lower end of the filter body is provided with an outlet pipe illustrated diagrammatically at 24, and an inlet pipe 26 is connected to the upper end through an aperture in a screw cap 28. The cap is located in position by means of fixing bolts 30 which are screwed into external lugs 32 at diametrically opposed positions on the outside of the filter body.
The cap 28 is also provided with a downwardly extending skirt 34 which projects into the upper end of the body of the filter, so as to seal against a sealing ring 36 inside the upper edge of the body.
In use, the nylon mesh wadding is coated with a special filter medium, the preparation of which is explained below, and the filter body is assembled with the perforated filter plate locked into position between the locating rings 6 and 8 using the bayonet type fixing described above. As “grey” water passes through the filter body, the filter medium acts to remove soap and accompanying scum from the water, so that the flow from the outlet is quite clear.
After the sediment has been left for a suitable length of time to coagulate and set, it can be thinly spread over the nylon mesh material, so as to be ready for use in the filter assembly.
As shown in
As shown in
Grey water enters the filter apparatus through the inlet pipe 26, the grey water then passes through the filter plates 4 and the nylon mesh 22 having filter medium supported thereon and exits the apparatus through the outlet pipe 24.
Each filter plate 4 is releasably fitted into the housing 2 allowing replacement of one or more of the filter plates 4 and the nylon mesh 22 having filter medium supported thereon.
An embodiment of a grey water recycling apparatus is illustrated in
It will be understood that there may be provided alternative grey water sources such as a bath or wash basin and more than one source per filter.
A baffle unit 54, is provided in the piping allowing diversion of excess grey water when the capacity of the filter apparatus is exceeded. This prevents grey water backing up into the source when there is an excessive flow to the filter.
In the embodiment illustrated in
Two investigations into the composition of examples of the sediment forming the filter medium have been carried out. Details of the first investigation are set out below.
The sample subjected to chemical composition analysis arose as a solid product from the electrolysis of domestic 15 mm copper (Cu) pipe, using locally collected seawater as the electrolyte, and a steel cathode. The resulting compound(s), hereinafter referred to as the filter medium was blue/green in appearance and saturated with an aqueous liquid. The method employed to produce the filter medium is similar to electrolytic refining. Samples of the copper pipe used as the anode and seawater, both pre and post electrolysis were also provided for analysis.
Inductively Coupled Plasma Mass Spectrometry Analysis
Three sub samples of the filter medium were washed in high purity 18 MΩcm−1 distilled, deionised water (DDW, Elgastat Maxima, Elga Ltd, High Wycombe, UK). Each of these washed sub samples was then dried to a constant mass at 80° C. for 24 hours. Subsequently, approximately 0.2 g of dried product from each sub sample was accurately weighed, dissolved in approximately 20 g of accurately weighed 10% HNO3 (Aristar Grade, BDH, Poole, UK). The metal content of these samples was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The elemental composition of 15 mm domestic Cu pipe was also determined by ICP-MS. For this analysis approximately 1.5 g of Cu pipe was accurately weighed and dissolved in approximately 6 g of concentrated HNO3 (Aristar Grade, BDH) and diluted gravimetrically to approximately 135 g with DDW prior to analysis.
There are a number of potential isobaric interferents, which arise from polyatomic ions formed in the plasma and interface region, for the analytes of interest. In order to overcome these potential sources of error a VG Axoim (Thermo Elemental, Winsford, UK) high resolution ICP-MS was used for all trace analyses. Typical operating conditions are shown in Table 1. A series of multi-element calibration standards containing the elements of interest, shown in Table 1, was prepared from 10,000 μg g−1 Spectrosol plasma standards (all purchased from BDH). Indium was added to all calibration standards and samples as an internal standard to account for instrumental drift.
Seawater Alkalinity Analysis
The alkalinity, a measure of the carbonate concentration, of the pre and post electrolysis seawater samples was measured by a pH titration against sulphuric acid. A 60 ml sample of seawater was acidified by the addition of consecutive 100 μl aliquots of a 0.01 M H2SO4 solution, prepared by diluting concentrated H2SO4 (BDH Aristar Grade) with DDW. The pH of the seawater sample was recorded after the addition of each aliquot of H2SO4. Each seawater sample was analysed in triplicate.
Counter Anion Tests
In order to determine the counter anion a series of tests were performed on sub samples of the dried filter medium. To determine the presence of the carbonate anion (CO32−) approximately 200 mg of the filter medium was placed in a test tube fitted with a gas liberation device. Subsequently, 0.5 ml of 6 molar HCl (Aristar Grade, BDH) was added to the test tube. The resulting gasses were bubbled through a saturated solution of barium hydroxide (Ba(OH)2). A second sub sample, again of approximately 200 mg, was used to test for the presence of the sulphate anion (SO42−) by acidification with 6 M HCl followed by the addition of a few drops of 0.2 M BaCl2 solution. The presence of the hydroxide anion (OH) was tested for by dissolving the filter medium (200 mg) in an ammonia solution (Aristar Grade, BDH).
Carbon, Hydrogen and Nitrogen Analysis
The presence of C, H, and N in the filter medium was determined using a EA1110 CHNS analyser (CE Instruments, Milan, Italy). Three sub samples of approximately 100 mg each were accurately weighed into combustion capsules for analysis. Three separate sub samples of PACS-1 CRM (National Research Council of Canada, Ottawa, Canada) of approximately 100 mg each were also quantified as a check on analytical accuracy.
ICP-MS Analysis
Filter Medium
An initial scan for all of the elements (Except C, H, N, O and Ar) showed significant quantities of sodium (Na), magnesium (Mg), sulphur (S), calcium (Ca), iron (Fe), copper (Cu), silver (Ag), tin (Sn), antimony (Sb), iodine (I), barium (Ba), mercury (Hg), lead (Pb) and uranium (U) in the filter medium. Subsequently, the amounts of these elements in the filter medium were accurately determined, by conventional external calibration, using high resolution ICP-MS. The filter medium was found to be 45.4% copper by mass, with lesser amounts of the other elements present. Table 2 shows the percentage composition of the filter medium for all of the elements of interest.
Domestic Copper Pipe
A sample of domestic 15 mm Cu pipe was digested in concentrated HNO3 and the elemental composition determined by high resolution ICP-MS in the same manner as the filter medium. Table 2 shows the elemental composition of the copper pipe.
Pre and Post Electrolysis Seawater
Samples of the seawater used as the electrolyte during the production of the filter medium were also provided for analysis. The analytes of interest in these samples were measured by high resolution ICP-MS by conventional external calibration. Table 2 shows the results of these analytes, no significant differences in the elemental composition of the pre and post electrolysis samples was detected.
Seawater Alkalinity Analysis
The carbonate and bicarbonate concentrations in the pre and post use seawater electrolyte samples was measured by acidification with H2SO4. A plot of the change in pH/volume of acid added (ΔpH/ΔVm) versus the volume of acid added (Vm) allows the calculation of the carbonate and bicarbonate content from the peak maxima.
Counter Anion Tests
Three separate experiments were performed on the filter medium to determine the counter anion. Firstly, the presence of carbonate was determined by sample acidification and bubbling the liberated gas(es) through saturated barium hydroxide. Acidification of the filter material liberated a colourless, odourless gas followed by a white precipitate, indicating the presence of the carbonate anion (CO32−). Equations 1 and 2 show the reaction scheme. The second test was designed to test for the presence of the sulphate anion, SO42−. No precipitate was observed during this analysis, therefore, the sample does not contain the sulphate anion.
CO32−(aq)+2H+(aq)→+CO2(g)+H2O(l) Equation 1
CO2(g)+Ba2+(aq)+20H(aq)−>BaCO3(s)+H2O(l) Equation 2
Finally, a separate sub sample of the filter medium was dissolved in a concentrated ammonia solution. Upon dissolution the clear ammonia solution changed colour to an intense blue, indicating the presence of copper hydroxide (Cu(OH)2). During this test not all of the filter medium dissolved, approximately 50 mg of the filter medium was recovered, dried and tested for the CO32 anion, which proved positive.
Carbon, Hydrogen and Nitrogen Analysis
The carbon (C), hydrogen (H) and nitrogen (N) content in three sub samples of the filter medium were determined by combustion analysis. C, H, and N, were also determined in NRCC PACS 1 CRM for quality assurance purposes. Table 3 shows the results of these analyses, the sample of the filter medium supplied is composed of 2.85% carbon and 1.1% hydrogen. No nitrogen was detected in the filter medium.
Identification of the Filter Medium
ICP-MS analysis of the filter medium has shown that it comprises 45% by mass of copper, with 1.1% by mass composed of other metallic elements as shown in Table 2. A good correlation was observed between the elemental composition of the 15 mm domestic copper pipe, the electrolysis starting material, and the elements found in the filter medium (Table 2). The composition of the seawater, which was used as the electrolyte in the filter medium manufacturing process, did not change significantly from the pre to the post electrolysis sample with respect to the elements found in the filter medium. However, the carbonate concentration and the pH of the seawater fell during the manufacturing process. This indicated that the filter medium contained the carbonate anion, and possibly the OH— anion, the removal of which from the seawater would cause a fall in the pH.
Subsequently, the identity of the counter anion was confirmed by two separate procedures. Firstly, carbon dioxide (CO2) was liberated when the filter medium dissolved in hydrochloric acid, this indicated the presence of the carbonate anion, CO32−. Secondly, an intense azure blue colour was observed when the filter medium was dissolved in ammonia, this indicated the presence of the hydroxide anion, OH—. Therefore, the sample provided which results from the electrolysis of domestic 15 mm copper pipe with seawater as the electrolyte, is a mixture of copper carbonate (CuCO3) and copper hydroxide (Cu(OH)2). The relative proportions of these two compounds in the sample presented for analysis was approximately 70% Cu(OH)2 and 30% CuCO3, based on the relative proportions of carbon and hydrogen present in the filter medium, as each copper species contains only one of these elements.
It should be noted that the chemical form of the other elements present in the filter medium could not be determined due to their low concentrations. However, it can be surmised that these metals are in a relatively insoluble form, either the carbonate, hydroxide, oxide or sulphate species dependent on the metal. Which metal is in which form will be dependent on the solubility of the individual metal/counter anion species in seawater.
The filter medium has been identified as a mixture of copper hydroxide and copper carbonate, with lesser amounts of other metallic species. The relative proportions of the two copper species was calculated as 70:30 from the experimental results obtained.
The filter medium was manufactured via the electrolysis of domestic 15 mm copper pipe, which was the anode in the electrolytic cell, with seawater as the electrolyte. When tap water is used as the electrolyte little or no anode sludge is formed, i.e. the nature of the electrolyte appears to control the process of anode sludge formation. The pH and alkalinity of seawater is higher than that of tap water and as such has a lower capacity to retain the copper ions than tap water. Hence, the seawater has little spare capacity to retain the copper ions released from the anode under electrolysis when compared with tap water. Therefore, insoluble copper, and other metal ions for which seawater is already saturated, form insoluble compounds with the various anion species present in seawater. Thus, no anode sludge is formed when tap water is employed as the electrolyte as the majority of the sacrificial copper anode remains dissolved in the electrolyte and, as the anion concentration of tap water is significantly lower than that of tap water, insoluble species do not form as readily.
The details of the second analysis are set out below.
The tested sample was a blue paste-like material from the electrolysis of seawater using copper electrodes.
The aim of this testwork was as follows:
Grey-Water Treatment
The sources of grey-water in this investigation were baths, showers and hand-wash basins. Characteristic impurities/problems within this water source are:
Analyses Performed on the Filter Medium
A sample of the blue coloured paste-like material (the filter medium) was provided for analysis. The analyses performed included a particle size determination, elemental analysis using X-ray fluorescence (XRF), mineralogical determination using X-ray diffraction and solubility in acid.
a) Particle Size Analysis
b) Elemental Analysis by XRF
The principle oxide components are shown in Table 4 with the full analysis shown in Appendix B.
c) Mineralogical Analysis by XRD
Determination of the Soap Removal Achieved by a Filter Containing the Filter Medium
A test solution containing 30 cm3 of fairly Liquid™ detergent and 4500 cm3 of tap water (equivalent to 6623 ppm). The majority of this solution was passed through a filter containing the filter medium. Samples of the solution before and after treatment were collected in glass bottles for analysis.
The concentration of the contained detergent in the water sample would affect the surface tension of the sample. The surface tension of both the untreated and treated water samples were compared to standards produced in the laboratory. The pendant drop method was used to measure surface tension using the FTA 2000 instrument. For each solution three measurements were taken immediately on droplet formation and after 2 and 5 minutes relaxation. As expected the surface tension reduced with time as the surfactant molecules migrated to the air-liquid interface.
The calibration graph produced with fairy Liquid™ solutions of varying concentrations is shown in
The measurements made with the two samples provided are given in Table 5.
The tests show that discrimination of concentration using surface tension as an indicator is only possible when the concentration is <200 ppm. Using the calibration graph the concentration of fairy Liquid™ in the solution after filtration is approximately 60 ppm. This is less than 1% of the original concentration, which equates to 99% removal.
GENERAL CONCLUSION
1. The analytical evidence suggests that the major component in the filter medium product is the naturally occurring mineral para-atacamite.
2. Surface tension measurement can be used to estimate the concentration of soap in water in the concentration range 0-200 ppm. It should be possible to determine higher concentrations by dilution.
3. The majority of soap (99%) was removed by a single pass through the filter containing the filter medium.
23Na, 24Mg, 32S, 44Ca, 56Fe, 63Cu, 107Ag, 115In, 120Sn, 121Sb, 127I,
138Ba, 202Hg, 208Pb, 238U
| Number | Date | Country | Kind |
|---|---|---|---|
| 0415869.7 | Jul 2004 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2005/002762 | 7/14/2005 | WO | 00 | 2/19/2008 |
