PATON, Graeme, Iain (41 Elmfield Avenue, Aberdeen, Aberdeenshire AB24 3NU, GB)
CASSIDY, Leigh (276 George Street, Aberdeen, Aberdeenshire AB25 1HL, GB)
KILLHAM, Kenneth, Stuart (Knowehead House, MonymuskInverurie, Aberdeenshire AB51 7SQ, GB)
PATON, Graeme, Iain (41 Elmfield Avenue, Aberdeen, Aberdeenshire AB24 3NU, GB)
CASSIDY, Leigh (276 George Street, Aberdeen, Aberdeenshire AB25 1HL, GB)
CLAIMS
1. A method of remediating contaminated water which method comprises treating the water with draff.
2. A method according to claim 1 wherein the water is contaminated with chlorinated hydrocarbons, dissolved and free product phase hydrocarbons, metals, BTEX, chromium, uranium, perchlorate, and/or RDX.
3. A method according to claim 1 or 2 wherein the draff comprises a solid waste product of the fermentation process of maize, wheat, rice, barley, sorghum, millet, oats, rye, triticale, or buckwheat.
4. A method according to any preceding claim wherein the draff comprises a solid waste product of the fermentation process of barley.
5. A method according to any preceding claim wherein the draff comprises a solid waste product of the fermentation process of barley during whisky manufacture.
5. A method according to any preceding claim which comprises groundwater remediation through enhanced natural attenuation.
6. A method according to any preceding claim wherein the water is groundwater contaminated with chlorinated hydrocarbons and the method comprises groundwater remediation through reductive dechlorination of the chlorinated hydrocarbons .
7. A method according to claim 6 wherein the reductive dechlorination proceeds via biotic pathways and/or abiotic pathways .
8. A method according to claim 7 wherein the reductive dechlorination proceeds via a combination of biotic and abiotic pathways.
9. A method according to any preceding claim in which the water is groundwater which is treated in in situ.
10. A method according to claim 9 wherein the in situ treatment comprises the use of a treatment wall, a permeable reactive barrier, or a borehole using a borehole deployable delivery system.
11. A method according to any one of claims 1 to 9 in which the water is groundwater which is treated ex-situ.
12. A method according to claim 11 wherein the ex situ treatment comprises the use of a bioreactor, a fluidised bed reactor or a sediment tank.
13. A method according to any preceding claim wherein the water is treated passively.
14. A method according to any one of claims 1 to 12 wherein the water is treated actively.
15. A method according to any preceding claim wherein the draff is used alone as an active material.
16. A method according to any preceding claim wherein the draff is bulked with non-active materials.
17. Apparatus for use in a method of remediating contaminated water which method comprises treating the water with draff, the apparatus comprising a container containing draff and means for allowing water to contact the dra'ff on passing through the container.
18. Apparatus according to claim 17 wherein the container comprises an elongate canister.
19. Apparatus according to claims 17 or 18 wherein the container is made from a material which is substantially inert and non-corroding in the intended environment of use.
20. Apparatus according to any one of claims 17 to 19 wherein the container is made from stainless steel.
21. Apparatus according to any one of claims 17 to 20 wherein the container comprises a mesh, the mesh size being sufficiently small so as to substantially prevent egress of draff from -the container whilst allowing water to pass through the mesh and the draff within the container.
22. Apparatus according to any one of claims 17 to 21 which comprises a plurality of containers linked together in a chain.
23. Apparatus according to any one of claims 17 to 22 for deployment down a borehole.
24. A method of remediating contaminated water substantially as hereinbefore described.
25. Apparatus for remediating contaminated water substantially as hereinbefore described with reference to Figures 5a and 5b. |
A METHOD OF REMEDIATING CONTAMINATED WATER AND APPARATUS
FOR THE SAME
[001] The present invention relates to a method of remediating contaminated water, for example groundwater, surface water and waste water, for example groundwater contaminated with dissolved and free product phase hydrocarbons, metals, e.g. chromium and other transition metals, uranium, soluble components of petroleum hydrocarbons (BTEX), perchlorates, and hexahydro-1, 3, 5- trinitro-1, 3, 5-triazine (RDX), and in particular chlorinated hydrocarbons, and also to apparatus for the same.
[002] Chlorinated hydrocarbons are common pollutants within water systems. They are known to be resistant to remediation and degradation and are known to be toxic, possibly carcinogenic and mutagenic, to both humans and wildlife. For example, tetrachloroethene/perchloroethene
(PCE) and trichloroethene (TCE) are listed by the United States Environmental Protection Agency (USEPA) as being amongst the most commonly detected groundwater contaminants at sites covered by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (more commonly known as "Superfund" sites).
[003] Known techniques for the assessment, monitoring and remediation of sites with water contaminated with chlorinated aliphatic hydrocarbons (CAH) are acknowledged as problematic, due to the physicochemical properties displayed by CAH. CAH cause the formation of dense non-aqueous phase layers (DNAPL) making site characterisation and remediation difficult. Advances in
technology in the art have made determination of the mass and location of source material easier, and recent contaminant -visualisation models have enabled further insights into plume behaviour. However, restoration of water systems (for example aquifers) to maximum contaminant levels (MCLs) has largely remained impossible.
[004] Traditional reductive water remediation treatments have included the use of simple electron donor compounds such as lactose, alcohols, milk fat, Hydrogen Release Compound (HRC ) , or complex electron donors such as molasses, corn syrup, zero valent iron (ZVI), organic mulch, yeast extract, edible oils, and Biogeochemical Reductive Dechlorination (BIRD) . However, such treatments are expensive (HRC) , require repeated applications (sodium lactate, whey) , require complex storage techniques (whey) , or have reduced permeability / water flux (ZVI, some mulches) .
[005] The present invention seeks to provide a method of remediating contaminated water, for example groundwater, surface water and waste water, which method can be used in situ and ex situ, and is effective, sustainable and cheap.
[006] Thus, according to the present invention there is provided a method of remediating contaminated water which method comprises treating the water with draff.
[007] The method of the present invention preferably removes or reduces water contaminants including, but not limited to, chlorinated hydrocarbons, dissolved and free product phase hydrocarbons, metals, BTEX, chromium, uranium, perchlorate, and RDX.
[008] Draff is a solid waste product ' of the fermentation of cereals, such as from the fermentation of barley during whisky or beer- production. For example, during whisky production the barley is firstly soaked to induce germination of the grain, which is then halted by heating
("malting") , following which the grain is ground and heated in a mash tun with water ("mashing") . After mashing, the liquids (the "wort") are taken for distillation to produce the whisky, whereas the solids (the "draff") are removed as a waste product, traditionally used as animal feed.
[009] Whilst a preferred draff for use in the present invention comprises a solid .waste product of the fermentation process of barley, and in particular a solid waste product from whisky manufacture, the term "draff" as used herein encompasses all solid waste products of the fermentation process of any cereal, for example maize, wheat, rice, barley, sorghum, millet, oats, rye, triticale, and buckwheat.
[0010] As a waste product from fermentation processes of cereals draff is thus cheap and readily available. Draff may be refrigerated, for example for up to four months, without significant inhibition of performance, and may be frozen.
[0011] The biological/physical/chemical make-up of draff is a complex mixture of different constituents, the content of which will vary between different cereals and fermentation processes. An example of the content of whisky draff is shown in Table 1:
[0012] Whilst not being bound by theory, draff is believed to be useful for water remediation through a combination of factors resulting from its chemical, biochemical and
physical make-up. Thus, it is thought that draff maintains favourable redox conditions, provides electron donor compounds, a carbon source for the bacterial community, and catalytic compounds, and enforces a positive feedback cycle utilising biotic, abiotic and synergistic pathways. The chemical properties of draff are believed to maintain the reductive environment, malt and yeast provide sugars and trace nutrients and also facilitate the breakdown of cellulose within grain husks, alcohol, oil and protein are believed to act as surfactants altering the interfacial tension at the contaminant-water interface, and draff also provides fermentative organisms.
[0013] An embodiment of the method of the present invention comprises water remediation through enhanced natural attenuation. Some water systems display desirable properties which may enhance natural processes leading to enhanced attenuation rates.
[0014] Another embodiment of the method of the present invention comprises water remediation through reductive dechlorination of chlorinated hydrocarbons. Reductive dechlorination can proceed via biotic pathways (for example, fermentation or respiration) or abiotic pathways
(for example, hydrogenolysis or nucleophilic substitution) . A preferred embodiment of the method of the present invention comprises a synergism between biotic and abiotic pathways for reductive dechlorination.
[0015] In the method of the present invention, draff may be used to treat water in-situ, for example in treatment walls, permeable reactive barriers (PRB) , or within a borehole using a borehole deployable delivery system.
Alternatively, the draff may be used to treat water ex- situ, for example in bioreactors, fluidised bed reactors or sediment tanks. The water ' may be treated passively, for example by initiating and/or augmenting natural and sustainable decontamination and attenuation mechanisms. For example, draff may be placed into the ground for groundwater to pass through, e.g. by drilling a borehole and dropping a borehole deployable delivery system, such as a canister or chain of linked canisters containing draff, down the borehole. Alternatively, a trench may be dug into which the draff is placed. Water may alternatively be treated actively, for example by capturing or funneling groundwater to be treated into a treatment zone containing the draff. The draff may be used alone or bulked with non- active materials such as sand or woodchips . For example, in a trench or a borehole deployable delivery system the draff may be sandwiched between layers of sand, woodchips or other non-active material.
[0016] According to the present invention there is also provided apparatus for use in a method of remediating contaminated water which method comprises treating the water with draff, the apparatus comprising a container containing draff and means for. allowing water to contact the draff on passing through the container.
[0017] The container may comprise an elongate canister, and may be made from a material which is substantially inert and non-corroding in the intended environment of use, such as stainless steel.
[0018] The container may comprise a mesh, the mesh size being sufficiently small so as to substantially prevent
egress of draff from the container whilst allowing groundwater to pass through the mesh and the draff within the container.
[0019] The apparatus may comprise a plurality of containers linked together in a chain.
[0020] The apparatus may be for use down a borehole, i.e. it may be borehole deployable.
[0021] The present invention will now be described in detail with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a treatment series of a flow through system for testing the water remediating effects of draff;
Figure 2 is a schematic representation - of a flow through system comprising four treatment series as shown in Figure 2;
Figure 3 shows the results of remediation of artificial groundwater contaminated with TCE in a reservoir using draff;
Figure 4 shows the results of remediation of artificial groundwater with TCE injected directly into the treatment series using draff;
Figure 5 shows the results of remediation of artificial groundwater contaminated with six different contaminants in a reservoir using draff; and
Figures 6a and 6b show a borehole deployable delivery system suitable for use in the method of the present invention, and a borehole deployable delivery system in use respectively.
Example 1
[0022] A treatment series for a flow through system was designed as shown schematically in Figure 1. A 20 litre reservoir 10 containing autoclaved distilled water was connected by PTFE tubing to a peristaltic pump 12 linked to three stainless steel columns 14a, 14b and 14c connected in series. The columns 14a, 14b and 14c comprised stainless steel cores having a diameter of 76 mm and a height of 300 mm and a stainless steel lid. Inlet ports 16a, 16b and 16c and outlet ports 18a, 18b and 18c were positioned 20 mm from the top and bottom of each column 14a, 14b and 14c and fitted with fine steel mesh (not shown in Figure 1) to prevent blockage by particles. A further pump 20 was positioned between outlet port 18b and inlet port 16c. Three treatment series (designated as series A, B . and C) were run simultaneously in each experiment, together with a control (no treatment, designated as series Z), as shown schematically in Figure 2.
[0023] The first and third columns (14a and 14c respectively) in each series A, B, C and Z contained only acid washed sand. The second columns 14b of columns A, B and C contained whisky draff (obtained from Strathisla distillery, Keith, Moray, Scotland) located at a mid column position (arrow X in Figure 1) forming 5 % v/v of the column 14b interior (67.5 g of draff). Column 14b of series Z contained no draff.
[0024] The treatment series A, B, C and Z were used to treat artificial groundwater having a TCE concentration of 100 ml/litre, prepared by injecting neat TCE into reservoir 10. The artificial groundwater was pumped through treatment series A, B, C and Z at a rate of 0.74 ml/min for 24 hours to give a 24 hour residence time.
[0025] 10 ml samples of artificial groundwater were extracted at selected sample points, these being (i) before the water entered the columns 14a, (ii) between the outlets 18a and the inlets 16b, (iii) between the outlets 18b and pump 20, and (iv) after the outlets 18c.
[0026] The TCE concentrations of the samples taken are shown in Figure 3. Analysis of the water taken at sample points (i) showed the same chemical composition as the water in the reservoir. Analysis of the water taken at sample points (ii) showed that approximately 20-25 % of the TCE had been sorbed by the columns 14a in each of series A, B, C and Z. Analysis of the water taken at sample points (iii) showed significant (P < 0.05) reductions in TCE concentrations (less than 5 % of initial concentrations) for series A, B and C (i.e. those series in which column 14b contained draff) but series Z showed no further reduction in TCE level compared to the sample taken at sample point (ii) . Analysis of the water taken at sample points (iv) showed TCE concentrations below the limits of detection (LOD) for series A, B and C (i.e. those series in which column 14b contained draff) but series Z showed no further reduction in TCE level compared to the sample taken at sample point (ii) .
Example 2
[0027] Treatment series A, B, C and Z were set up as described for Example 1 above and shown in Figure 2. An experiment was performed as described in Example 1 but with the reservoir 10 containing no contaminants, only distilled water. Instead, TCE was introduced directly by injection at inlets 16b and sample analysis was conducted only from points (iii) and (iv) described above. Delivery of TCE in this way aimed to represent "source" TCE, for example from direct spillages or storage leaks.
[0028] The TCE concentrations of the samples taken are shown in Figure 4. The concentrations designated 100 % are effluents from series Z, i.e. which had no draff treatment and merely passed through three sand filled columns. The final effluent had a TCE concentration of 1460 mg/litre, and the amount of TCE removed by draff treatment in series A, B and C is presented as a percentage of this value.
[0029] Figure 4 shows that the average loss of TCE after passing through draff treatment columns 14b of series A, B and C was 78 %, and that the average loss of TCE after passing through columns 14c of series A, B and C was 90 %. [0030]
Example 3
[0031] Treatment series A, B, C and Z were set up as described for Example 1 above. An experiment was performed as described in Example 1 but with the reservoir 10 containing six different CAH contaminants, each at a concentration of 100 mg/litre (PCE, TCE, dichloroethene
(DCE) carbon tetrachloride (CT), chloroform (CF) and trichloroethane (TCA) . Artificial groundwater samples were
taken at points (i) , (iii) and (iv) as described in Example 1.
[0032] The CAH concentrations of the samples taken are shown in Figure 5 (the results being shown for PCE, TCE, DCE, TCA, CT and CF respectively from left to right for each sample set). The results show that all six contaminants were present in significantly (P < . 0.05) decreased concentrations in series A, B and C compared to series Z. The greatest decreases in concentration were with CT and TCA, where decreases of greater than 90 % were recorded at all sample points. TCE concentration decreases were 70 - 80 %, and DCE concentration decreases were greater than 80 %. The contaminants least affected by draff treatment were PCE and CF, but even these contaminants had decreased in concentration at sample point (iv) by 78 % and 82 % respectively.
[0033] As is described above, the present invention provides apparatus for use in a method of remediating contaminated water which method comprises treating the water with draff, .the apparatus comprising a container containing draff and means for allowing water to contact the draff on passing through the container.
[0034] Figures 6a and 6b show a borehole deployable delivery system suitable for use in the method of the present invention, and a borehole deployable delivery system in use respectively.
[0035] Referring to Figure 6a, a borehole deployable delivery system suitable for use in the method of the present invention is shown. In the embodiment shown in
Figure 6a, the system comprises an elongate canister 100 containing draff. The draff may be used either alone or together with non-active materials, such as sand or woodchips . For example, the draff may be sandwiched between or otherwise embedded within sand or woodchips within the canister 100. The canister 100 is preferably made from a material which is substantially inert and non-corroding in the intended environment of use, such as stainless steel. The canister 100 comprises a mesh 110, the mesh size being sufficiently small so as to substantially prevent egress of draff from the cannister 100 whilst allowing water to pass through the mesh 110 and the draff within the canister 100. The canister 100 may be used alone, or a plurality of canisters 100 may be linked together in a chain by way of a linker 120 at each end of the canister 100. Whilst there is no theoretical limit to the dimensions of the canister 100, for practical purposes a length of from 10 to 20 cm, for example approximately 15 cm, a diameter of from 1 to 5 cm, for example approximately 3 cm, and a mesh size of from 0.25 to 0.75 mm, for example approximately 0.5 mm, are suitable .
[0036] The canister 100 is suitable for deployment down a borehole for passive remediation of groundwater. Figure 6b shows a chain 140 of canisters 100 linked together via linkers 120 positioned with a borehole 150. The arrows A indicate the direction of flow of the groundwater.
[0037] It will be understood that the illustrated embodiment described herein shows an application of the invention in one form only for the purposes of illustration. In practice the invention may be applied to many different configurations the detailed embodiments
being straightforward to those skilled in the art to implement .