GB2298645A

GB2298645A - Degrading waste hydrocarbons using bacteria

Info

Publication number: GB2298645A
Application number: GB9504637A
Authority: GB
Inventors: David Evans
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-08
Filing date: 1995-03-08
Publication date: 1996-09-11
Anticipated expiration: 2015-03-08
Also published as: WO1996027645A1; AU4887396A; GB2298645B; GB9504637D0

Description

Oil Degradation Apparatus This invention relates to an apparatus for degrading contaminating blooms of hydrocarbon based material and chemical spill, and more particularly to an apparatus for use in degradation of these materials in interceptors or similar oily catchment areas.

It is already well known that interceptors are used in industry and garage forecourts to capture spilled oil and retain it in an aqueous phase thus preventing the oil from entering the normal drainage systems. Thus large amounts of oil or chemicals are prevented from being discharged into the environment.

Prior art interceptors are designed so that the size of the interceptor is a function of the volume of effluent water to be handled and the ease of separation of the emulsion. When correctly sized, interceptors offer a period of time during which the emulsified oil may separate from the water phase and rise to the surface. The oil can then subsequently be removed in a number of known ways such as vacuum tank suction, oil rope mop machine, skimmers or absorbents. However, these techniques can prove cumbersome and the removed oil has still to be disposed of carefully.

In addition the efficiency of the oil catchment interceptors decreases with use as the hydrocarbon material coagulates and attaches itself to the inner surfaces of the interceptor. As a consequence of this the interceptor must be periodically cleaned to meet emission regulations laid down by such bodies as the National Rivers Authority (NRA).

Attempts have been made in the past to increase the efficiency of interceptors by the introduction of removable absorbent media within the interceptor cavity. However, this has been found to be only a short term solution as the absorbent media is soon saturated with oil thus becoming ineffective and thus present new problems regarding their disposal.

Recent maritime incidents have shown the vulnerability of coastal fish farms to spilled oil. Normal protective procedures in such circumstances involves the surrounding of the fish cages with surface barrier means such as a boom.

This may serve either as a solid deflection barrier or to absorb any oil with which it comes into contact. However if the duration of the spill is prolonged or if, due to such influences as weather conditions, the spill is of a greater volume than can be deflected or absorbed by the boom then potentially disastrous consequences may result.

Oil selective bacteria have also been used in the degradation of oil spills and are supplied ready for use in a liquid or powder form. However, it is virtually impossible to use these media in the presence of continuous effluent flow conditions as found in industrial interceptors.

There are many proposals amongst the prior art including information in patent literature available for reducing oil pollution in water but most of these patents provide for only one application of the composition, not a composition which itself is self perpetuating in the presence of oil and for this reason such proposals have a very limited effective life span.

GB 1542154 describes a composition to be applied to contaminated water and which floats on the surface of the water and subsequently breaks down the oil. The composition is not reusable after it has broken down the oil and therefore would be totally unsuitable in interceptors as it would only break down the oil on the surface and the oil on the sides and the bottom of the tanks would be left untouched. Furthermore the composition would have to be added continuously thus making the whole operation inefficient, laborious and expensive.

FR 2682972 describes a barrage containment system which works by absorbent/bacterial action but it is not a continuous system where the bacteria colonise and re-produce themselves continually.

HU T57260 describes encapsulation of bacteria within a sponge however compressed air must be passed through the sponges to allow adequate bacterial growth unlike the present invention to be described below which utilises ambient atmosphere on demand.

Likewise DE 2850624 describes a fixing system which requires a special composting tank with forced aeration until the material within it is decayed. It is therefore not possible to use this kind of system in an interceptor which at times has a continuous passage of water through it.

DE 2803814 describes a bacterial absorption powder to be added to traditional granular absorbents and would therefore be unsuitable for use in interceptors..

US 3883397 describes a system of coating the nutrient so as to allow slow diffusion into the water phase. Again this is not an in situ reusable absorbent propagating bacterial migration unlike the present invention.

W091/01945 describes a system using biodegradable sponges which will float on the surface of the water for approximately two days unlike the present invention which is not biodegradable and will float indefinitely on the surface of the water.

EP 0479476 provides a spillage absorption material which is used for absorbing liquid spills and has no degradation activity whatsoever.

The aim of the present invention is to provide an apparatus for use in an interceptor which obviates or mitigates the aforementioned disadvantages.

According to one aspect of the present invention there is provided an apparatus comprising a flexible walled containment means with exterior, releasable fixing means, a quantity of absorbent medium contained within the containment means, the absorbent medium inherently having, or being pre-treated to confer properties facilitating growth of bacteria and further tending to be oleophilic and hydrophobic, the said containment means further containing an amount of bacteria capable of degrading or digesting organic materials, especially hydrocarbon based material.

A preferred medium is dried peat, which is capable of swelling within the containment means, and may swell up to ten times in volume to fill the containment means and provide a swollen matrix upon which the bacteria may grow and further provide maximum surface area for contact with the oil.

A further preferred medium is polypropylene.

Advantageously the bacteria are oil specific bacteria.

The containment means may be stretchable as well as flexible to enable it to conform to surfaces to which it is to be applied. However semi-rigid containment means though less desirable are not to be excluded.

According to another aspect of the present invention there is provided an apparatus comprising a flexible walled containment means with exterior, releasable fixing means, a quantity of absorbent medium contained within the containment means, the absorbent medium inherently having or being pre-treated to confer oleophilic and hydrophobic properties, the said containment means further containing holding means, the holding means containing an amount of medium conducive to growth of bacteria and an amount of bacteria capable of degrading or digesting organic materials, especially hydrocarbon based material.

Preferably the holding means may be made of polypropylene fibre.

Advantageously the holding means may be in the form of a sachet. Alternatively the holding means may be in the form of a small bag.

According to a yet further aspect of the invention, there is provided a method of disposing of oil-contaminated water comprising, optionally filtering the oil-contaminated water, contacting the oil-contaminated water with oildegrading bacteria supported upon a growth facilitating medium, which medium is oleophilic and confined within a flexible walled housing.

The present invention will now be described below by way of illustration with reference to one specific embodiment.

An apparatus is provided having a container in the form of a sealed, substantially rectangular-shaped bag, the outer lining of which is formed of a flexible, oleophilic, water repelling material. Furthermore, the bag is of suitable dimensions to allow it when full to fit snugly into the interceptor in which said bag is to be deployed. The bag has releasable fixing means which may be in the form of eyelets which allows the bag to be releasably tethered to an appropriate fixing point.

Within the sealed bag is contained an internal substantially homogeneous mixture, the mixture containing for example, an absorbent such as dried, fibrous peat.

Furthermore the peat is pre-treated for example by use of a proprietary silicone agent or prior immersion in an aqueous saline solution to increase its ability to absorb any oil present but to minimise its uptake of water.

Within the container held in the absorbent medium is holding means in the form of a sachet or bag made from a suitable material such as polypropylene cloth fibre. Within the sachets are selectively blended oil specific bacteria, accelerator and suitable nutrient medium for said bacteria.

The arrangement being that the bacteria utilise the medium within the sachet or bag and begin to colonise.

In a further embodiment several bags can be linked by ropes or the like to form a boom in order to provide a surface barrier to absorb any oil with which it comes into contact.

Furthermore the bags can be redesigned as conventional oil absorbing booms but with the essential difference being that they become bioremediating oil absorbent booms capable of re-use and cost effective disposal and will float and continue functioning indefinitely.

In use the bag is suspended on the surface of the effluent (normally comprising a mixture or emulsion of oil and water) in the interceptor and the pre-treated peat immediately starts to absorb the oil. As the peat absorbs the oil it swells up to approximately ten times its original size thus filling out the pillow shaped bag. At this stage the outer lining starts to discolour which observation serves as a visual indicator of function but is not essential to that function. At the same time, the small amount of water contained within the oil emulsion is selectively blended oil specific bacteria, accelerator and suitable nutrient for said bacteria. The arrangement being that the bacteria utilise the medium within the sachet and begin to colonise absorbed by the peat.This oil emulsion is therefore absorbed into the absorbent medium and then further absorbed by the sachets which subsequently activates the bacterial culture thus initiating its growth within the sachet. In the presence of the hydrocarbons which form the oil, the now colonised bacteria present in the internal mixture commence degradation of the organic components in the oil such as benzene, toluene and xylene to produce harmless by-products such as carbon dioxide and water.

Signs of bacterial activity take a short time to develop, depending on the temperature, aeration and quantity of hydrocarbons present in the interceptor. Usually "strings" or "plates" of biomass will be seen on the outer surface of the bag or in the adjacent water within a few days.

Once bacterial colonisation has commenced within the sachet, migration of the bacterial colony through the absorbent medium occurs followed subsequently by migration from the container to other oil rich areas within the interceptor thusbioremediating oil absorbed into the container and subsequently bioremediating oil contained within the interceptor.

Once established in an interceptor or pond which receives regular influxes of hydrocarbons, significant biomass can usually be seen and will attach itself to the sides and bottom of the interceptor tank. Small plates of biomass may be carried out of the interceptor tank in the final effluent where the bacteria cease to become active in the absence of hydrocarbons, or they may clean up residual hydrocarbons originally carried over in the outfall.

Biological action is self limiting in so far as when ambient temperatures are high, aeration is good (ie flow through the system) and hydrocarbons are present, bubbles of carbon dioxide will be visible as the oil is removed from the tank.

The bags should not be placed in interceptors with a high proportion of trapped oil already in place (ie more than 50% oil coverage of the chamber surface). In such situations, the internal mixture saturates with oil and the bacteria colony will not activate and establish itself.

Ideally, the bags should be placed in the interceptor immediately following normal clean out of the tanks so that the bacteria may deal with the usual expected influx of hydrocarbons rather than an accumulation of earlier material. Once the bacteria have colonised and are established they can treat relatively large influent hydrocarbons as they take place.

When influent streams contain significant quantities of disinfectants or bactericidal materials, bacterial colonies may be destroyed and will not re-establish until a new bag has been replaced after removal of the source of the biocide.

In this way the bag functions as a traditional in place absorbent but due to the presence of the oil specific bacteria and the initial nutrient medium, the bacteria are able to grow up colonies which then become self perpetuating because the bacteria then utilise the oil as their growth medium. The bag will absorb oil up to the point of saturation and once colonisation of the bacteria has begun and degradation has occurred the peat will continue to reabsorb oil thus recommencing the oil degradation process allowing a continuous cycle to occur.

The oil specific bacteria can also migrate from the bags to seek out the oil rich solids which generally fall to the bottom of the interceptor tank.

If the bag becomes damaged and requires replacement, disposal is by storage in an oil resistant container until the retained oil has been degraded. Thereafter the damaged bag becomes oil free which results in any remaining bacteria dying and therefore the bag subsequently becomes safe for disposal. Subject to the prevailing waste disposal area legislation the bags can then be disposed of as dry-waste so avoiding the need for costly incineration.

Advantages of the present invention include the fact that water miscible polar solvents released from the separated oil are minimised by the degradation process within the bag.

The use of the bag assists in overcoming the problem of interceptor undersizing during surge water conditions, the bag assisting in maintaining continued low amounts of separated oil within the interceptor. This in turn reduces the frequency and cost of collecting separated oil from the interceptor.

Furthermore the present invention provides a self perpetuating adsorption/treatment process for the continuous disposal of separated oil in interceptors and in difficult access areas.

It should also be noted that because the polypropylene is treated to repel water the bag can remain at the air/water interface for an indefinite period. Furthermore because the bag contains polypropylene and oil specific bacteria it becomes a reusable absorbent once bacterial colonisation has taken place. Whilst at the air/water interface the bag remains as an incubator propagating bacterial colony migration to other oil rich areas.

The bag in this invention is self contained to allow colonisation of the bacteria without the need for anything other than the oil and water mixture of the contaminated water.

A test under supervised conditions of the invention in use is reported in the table below.

TABLE 1

ANALYSIS INFLUENT SAMPLE EFFLUENT SAMPLE pH 6.9 7.0 COD 5198 146.8 BOD +741 55.9 SUSPENDED SOLIDS 992 14 OIL 1334 mgl-1 10 mgl-l

Claims

Claims

1. An apparatus for degrading hydrocarbons having a flexible walled containment means with exterior, releasable fixing means, a quantity of absorbent medium contained within the containment means, the absorbent medium inherently having, or being pre-treated to confer properties facilitating growth of bacteria and further tending to be oleophilic and hydrophobic, the said containment means further containing an amount of bacteria capable of degrading or digesting organic materials, especially hydrocarbon based material.

2. An apparatus for degrading hydrocarbons having a flexible walled containment means with exterior, releasable fixing means, a quantity of absorbent medium contained within the containment means, the absorbent medium inherently having, or being pretreated to confer oleophilic and hydrophobic properties, the said containment means further containing holding means, the holding means containing an amount of medium conducive to growth of bacteria and an amount of bacteria capable of degrading or digesting organic materials, especially hydrocarbon based material.

3. An apparatus for degrading hydrocarbons according to claim 1 or claim 2 wherein the absorbent medium is peat.

4. An apparatus for degrading hydrocarbons according to claim 1 or claim 2 wherein the absorbent medium is polypropylene.

5. An apparatus for degrading hydrocarbons according to any preceding claim wherein the bacteria are oil specific bacteria.

6. An apparatus for degrading hydrocarbons according to any one of the preceding claims wherein the containment means is stretchable as well as flexible to enable it to conform closely to surfaces to which it is applied.

7. An apparatus for degrading hydrocarbons according to any one of claims 1 to 5 wherein the containment means is semi-rigid.

8. An apparatus for degrading hydrocarbons according to any one of the preceding claims wherein the containment means is biodegradable.

9. An apparatus for degrading hydrocarbons according to any one of the preceding claims wherein the growth medium contains an accelerator.

11. An apparatus according to any one of the preceding claims wherein the bacteria are oil specific bacteria.

12. An apparatus for degrading hydrocarbons according to claim 2 wherein the holding means is in the form of bags.

13. An apparatus for degrading hydrocarbons according to claim 2 wherein the holding means is in the form of sachets.

14. An apparatus for degrading hydrocarbons according to claim 2 wherein the holding means is made from polypropylene fibre.

15. An interceptor comprising an apparatus for degrading hydrocarbons according to any one of the preceding claims.

16. An apparatus for degrading hydrocarbons according to claims 1 or 2 wherein the containment means are designed to form oil absorbing booms.

17. An apparatus for degrading hydrocarbons according to claim 16 wherein the oil absorbing booms float and continue functioning in the degradation of hydrocarbons indefinitely.