WO2004056500A1

WO2004056500A1 - Treatment composition for hydrocarbon pollutants

Info

Publication number: WO2004056500A1
Application number: PCT/IB2003/006081
Authority: WO
Inventors: Petrus Johannes Crous Wagener
Original assignee: Ferguson, Gary, Wayne
Priority date: 2002-12-23
Filing date: 2003-12-19
Publication date: 2004-07-08
Also published as: AU2003292460A1

Abstract

A method of producing a treatment composition and treatment compositions produced by the method are provided for combating the ill effects of hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge. The treatment composition comprises raw sewage in the form of a sludge that has been depleted of foreign bodies and treated, preferably with lime, to provide a pH of the sludge of between about 9.5 and about 12, with a maximum water content of about 15 percent by weight. The treatment is also selected to render the treatment composition stabilized; hydrophobic and oleophilic; and absorbent in nature. The lime is generally added in an amount of from about 10 to 40 grams per litre of the sewage sludge based on a solids content of the sewage sludge of from about 3 to about 7 percent by weight. A method of combating hydrocarbon pollutants is also provided in which the treatment composition is applied to an affected that, if it is arable soil, the used treatment composition is worked into the soil.

Description

TREATMENT COMPOSITION FOR HYDROCARBON POLLUTANTS

FIELD OF THE INVENTION

This invention relates to a treatment composition for hydrocarbon pollutants and to methods of using such treatment composition.

BACKGROUND TO THE INVENTION

As a general rule, hydrocarbon pollutants most commonly exist in the form of spills, typically, consequent on some form of accident or another. Such spills may occur on either water or land and the land may be either arable or not. The hydrocarbon pollutants are most commonly crude oil or other petrochemical hydrocarbons that spill or leak from oil wells and associated oil transfer equipment, petrochemical processing equipment, and containers or vehicles following on accidents that occur during the transport of petrochemical products. Nevertheless, there is also a significant occurrence of other forms of chemical spill in which the chemical has a hydrocarbon base as well as instances in which there is an accumulation of hydrocarbons, typically in the form of engine oil or the like, in industrial and public areas.

Present procedures for dealing with hydrocarbon spills depend on whether or not the spill occurred on water or on land. In instances in which the spill has occurred on water, apart from employing buoyant barricades in an effort to contain the oil and prevent it from spreading, an absorbent material is often applied to the hydrocarbon in order to absorb it. The absorbent material and hydrocarbons contained in it are then collected and transported to a suitable disposal site where it is left to biodegrade over many years. In instances in which the spill has occurred on land, if the land is arable or movable, earth moving equipment may be used to collect the affected soil that is then similarly transported to a disposal site. In this regard, it is noted that the desirable biodegrading effect of activated sewage sludge has received attention in a number of proposals for dealing with hydrocarbon contaminated material.

In US patent 5,336,290 to Jermstad, there is proposed a process and a product by the process in which activated sewage sludge and hydrocarbon affected soil are mixed to promote bacterial degradation of the hydrocarbon contaminants and the resultant product is one that can be marketed. This proposed process however also involves movement of the soil from one place to another; working it to mix in the activated sewage sludge and thence moving it again to its final destination. It also does not propose any particular general purpose absorbent that can be used on land or water.

US patent 6,187,581 to Sicotte et al mentions the use of re-activated sewage sludge as an additive in a protein based treatment composition for the same purpose.

Numerous different types of the absorbent or adsorbent compositions have been proposed in US patent 5,492,881 to Diamond sets to some of these, at least many of which are based on cellulosic fibres that are relatively costly. In some cases, bioremediation is proposed as at least one alternative to various ways of either recovering or utilizing the heat generating potential of the hydrocarbons by burning the loaded absorbent or adsorbent.

In instances in which the spill is on non-arable land, such as rocky areas that cannot be moved to a disposal site, mechanical, and often manual, cleaning procedures are typically employed that are not entirely satisfactory. It is to be noted that the term raw sewage as used in this specification is intended to mean sewage before the usual chemical or biological treatment thereof has taken place that would have had the effect of breaking down fatty acids and other potential nutrients for microbiological species. Activated sewage sludge such as has been proposed in the prior art mentioned above, on other hand, is to be understood as sewage sludge that has been treated by means of aeration or bio-digesters or the like and as a result of which macro and micro elements and fatty acids that are considered by applicant as essential for soil bio-remediation have been rendered, at least to an appreciable extent, useless.

OBJECT OF THE INVENTION

It is an object of this invention to provide a treatment composition that overcomes, at least to some extent, disadvantages of currently used in, and previously proposed, the compositions and procedures, and that may be more environmentally friendly.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided a treatment composition for combating the ill effects of hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge, the treatment composition being characterized in that it comprises a raw sewage that has been stabilized; rendered hydrophobic and oleophilic; has an alkaline pH; and is in a form in which it is absorbent in nature.

Further features of this aspect of the invention provide for the pH of the treatment composition to be between about 9.5 and about 12; and for the treatment composition to have been stabilized and rendered hydrophobic and oleophilic by treatment with lime. In accordance with a second aspect of the invention there is provided a method of producing a treatment composition for combating the ill effects of hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge, the method being characterised in that it comprises treating raw sewage in the form of a sludge that has been depleted of foreign bodies with lime to provide a pH of the sludge of between about 9.5 and about 12, and reducing the moisture content to a maximum of about 15 percent by weight to provide a solid treatment composition.

Further features of this aspect of the invention provide for the lime to be added in an amount of from about 10 to 40 grams per litre, preferably 20 to 30 grams per litre of the sewage sludge, based on a solids content of the sewage sludge of from about 3 to about 7 percent by weight; for the lime to be intimately mixed with the sewage sludge followed by drying, optionally sun and air drying, to a cake having a moisture content of about 25 to 35 percent by weight followed by sub-dividing the cake into small pieces and then further drying to a moisture content of less than 15 percent by weight and preferably less than about 10%, or even less; and for the final dried treatment composition, to be graded through a mesh having a required mesh size, typically about 3 mm, followed by packaging in sealed bags.

In accordance with a third aspect of the invention there is provided a method of combating hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge the method being characterised in that it comprises contacting a treatment composition as defined above with the hydrocarbon pollutants and affording the treatment composition time to absorb said hydrocarbon pollutants, followed either by removal of the treatment composition and disposal thereof or by working the treatment composition into associated soil as may be appropriate to the substrate on which the hydrocarbon pollutants were present. Further features of this aspect of the invention provide for the treatment composition to be added progressively at a controlled rate that may either be continuous, semi-continuous or batch-wise to the hydrocarbon pollutants until such time as newly added treatment composition fails to change colour to thereby indicate that there is no further hydrocarbon pollutant present to be absorbed by the treatment composition; and for disposal of the used treatment composition to be effected by mixing it with soil, typically by ploughing or otherwise working it into a body of arable soil.

In instances in which the hydrocarbon pollutants are present on a body of water, or un-arable soil, the treatment composition with hydrocarbon pollutants absorbed therein will generally be removed from the formerly polluted site to a disposal site that could either be a disposal dump, or, more preferably, a body of arable soil in which case it is worked into the soil.

In order that the above and other features of the invention may be more fully understood an expanded description and the results of tests conducted will be described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a set of graphs showing biological activity in one form of treatment composition according to the invention; and,

Figure 2 is a set of graphs showing the breakdown of petroleum hydrocarbons that have been absorbed by the same treatment composition over a period of time. DETAILED DESCRIPTION OF THE INVENTION

The treatment composition of this invention, at least in its preferred form, actively absorbs hydrocarbon pollutants through capillary action and, this being so, the absorption is substantially irreversible. The result is that pollution of ground water is avoided and containment of hydrocarbon pollutants for removal or transport is thereby facilitated or, alternatively, in the case that the treatment composition together with absorbed hydrocarbons is to be worked into the soil, the pollutants are held captive within the treatment composition pending biodegradation thereof.

The treatment composition of the invention contains all of the macro and micro elements and fatty acids in the correct proportions to enable microbiological activity to return to contaminated soil. It serves as a "life support system" for these microbiological organisms in the soil (these organisms are found naturally in varying concentrations in the air). When the treatment composition is in the presence of hydrocarbons, oxygen (air), water, light or energy and a medium (soil), the micro-organisms begin to replicate rapidly.

It will be quite apparent that all these elements come together when the treatment composition is applied or ploughed into a site of a hydrocarbon spill. The fatty acids present tend to break down any complex hydrocarbon chains into simpler long chains. As the micro-organisms replicate they secrete an enzyme which in turn breaks down the long hydrocarbon chains thus remediating the soil.

Only untreated raw sewage sludge can be used (after "alien" solids have been physically removed) in the production of the treatment composition of the invention. This raw sewage sludge is typically sourced from primary sedimentation tanks. Raw sewage sludge still contains all the macro and micro elements and fatty acids that will be needed in the bio-remediation process and in its raw state will lend itself to being stabilized and have its structure manipulated by being dosed with lime. Lime dosing not only stabilises the raw sewage by raising the pH but also alters the absorption capacity of the raw sewage by changing what is a hydrophilic (water loving) composition into a oleophilic (oil loving) and hydrophobic (resistant to water) composition.

The treatment composition of the invention therefore has a natural affinity to absorb and hold captive hydrocarbons and compounds in any form of suspension. This is facilitated by its fibrous nature (once milled and sieved as described below) which allows for the absorption of hydrocarbons through active capillary action. Due to the nature of the manipulation of the hydrophilic structure, all the micro and macro elements as well as the fatty acids are intact and dormant and become active as soon as hydrocarbons, water, and air borne micro-organisms are added.

Preferably, raw sewage sludge with a 3 to 7 % (typically 4 to 6%) solids content (this apparently being the optimum from a handling point of view) is treated with lime in an amount of approximately 20 to 30 g per litre of sewage sludge. Lime is added in this amount in order to raise the pH to a level of between 9.5 and 12. This pH range is not only believed to be the optimum pH for soil remediation but it is also apparently the optimum level at which the raw sewage sludge will be stabilized.

The lime is added and mixed continuously during the course of the reaction time. The reaction time is typically between 4 and 8 hours but can be as long as 2 days. The more thoroughly the lime is mixed in the better. This process sterilizes the product but does not destroy the macro and microelements or the fatty acids. It does however alter the structure of the product thus changing its absorption capabilities. The product is then pumped onto drying beds where it is sun and air dried. If ambient weather dictates that this it is not feasible to dry the product in this manner then it can be artificially dried by whatever means is available provided that the temperature of the product should preferably be kept below 50 degrees C during the drying procedure. The moisture content is reduced by 70% - 80% during this drying stage and the product forms a cake having a moisture content of from about 25 to about 35 percent by weight.

The product is then subdivided into smaller pieces, typically by crushing or milling, and then dried further in a similar manner to a moisture content of 10% or less. At this point the product treatment composition is dormant and can be stored for long periods of time.

The dried product is sieved, prior to packaging, through a mesh having a mesh size that may be selected according to the intended use of the treatment composition. For best results from a soil remediation point of view the product should be finely subdivided as the finer the product, the more effectively it can be distributed and mixed into the soil. Typically a mesh size of 3mm is considered to be suitable. However, a mesh size of larger than 3mm is considered to be more effective for a product for specific oil on water applications.

It has been found that a typical treatment composition produced as described above has a pH of 12.0; a nitrogen content of 1 ,9%; a potassium content of 0,5%; a calcium content of 21 ,2%; a magnesium content of 0,6%; a sodium content of 0,1 %; a chlorine content of 0,02%; a sulphur content of 0,32%; a copper content of 130,0 mg per kg; an iron content of 4500 mg per kg; a manganese content of 367 mg per kg; a zinc content of 387 mg per kg; a boron content of 50 mg per kg, and a molybdenum content of 2,2 mg per kg. As indicated above the treatment composition is hydrophobic; oleophilic; and floats on water. In use, the treatment composition produced as described above may be applied to hydrocarbon pollutants in any of the ways already indicated. The rate of application may be determined empirically although tests conducted to date indicate that, in the case of a petrochemical spill on water, soil and hard surfaces, approximately 30 kg of treatment composition is required per 100 litres of spilled petrochemical composition whereas in the case of acid chemical spills, approximately 50 kg of treatment composition is required per 100 litres of spill, depending on the concentration and composition of the acids. The reason for the greater amount is undoubtedly the neutralizing effect that also takes place.

In any event, the amount of hydrocarbon pollutants is often not known and the treatment composition can be added progressively, either continuously or batchwise, until such time as treatment composition remains on top of the hydrocarbon pollutant without changing colour. A colour change indicates effective absorption of hydrocarbon whereas a lack of change in colour indicates that no further pollutant remains to be absorbed.

Contact of the treatment composition with a hydrocarbon pollutant must be accompanied by the presence of water and air as well as microbiological species present in the air. The treatment composition has a fibrous character providing absorption characteristics and as a result, depends upon capillary action for adsorbing the hydrocarbon pollutant. The nature of this absorption is such that it is irreversible under normal conditions and the pollutants become firmly associated with the treatment composition.

After a period of time, typically about two weeks, microbial action commences and humic acids present in the treatment composition hydrolyse the hydrocarbons through carboxylase enzymatic reactions to form long chain organic acids. The bacteria act on these organic acids to form acetic acid that in turn is responsible for the production of carbon dioxide and water under aerobic conditions, and methane and water under anaerobic conditions. In this manner the pollutant is converted to harmless products. It will be understood that the nutrients present in the treatment composition fuel the biological activity.

Figure 1 is a graph illustrating the build up and decline of biological activity over a nine week period in respect of three different tests that were conducted at different ratios of treatment composition to motor oil. The ratios were one part treatment composition to three parts oil; one part treatment composition to two parts of oil; and one part of treatment composition to one part of oil. As indicated in Figure 1 , in all cases, a maximum biological activity was achieved at about seven weeks and biological activity was only first noticed at about one week. The three different ratios behaved similarly but at different actual maximum activities.

Figure 2 illustrates the decrease in total petroleum hydrocarbons present in the treatment compositions in the above tests. It will be noted that the hydrocarbon content apparently increased within the first two weeks and then started decreasing until the fourth week when it began reducing rapidly and was still reducing relatively rapidly at nine weeks having reached less than 25% of the original oil content.

It is considered to be a particularly advantageous feature of the invention that treatment compositions according to the invention containing absorbed hydrocarbons can be recovered from a body of water; spread onto an area of arable soil and worked into the soil with benefits to the soil in due course.

The invention therefore provides an extremely effective yet inexpensive treatment composition for the aforesaid purpose.

Claims

CLAIMS:

1. A treatment composition for combating the ill effects of hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge, the treatment composition being characterized in that it comprises a raw sewage that has been stabilized; rendered hydrophobic and oleophilic; has an alkaline pH; and is in a form in which it is absorbent in nature.

2. A treatment composition as claimed in claim 1 in which the pH of the treatment composition is between about 9.5 and about 12.

3. A treatment composition as claimed in either one of claims 1 or 2 in which the treatment composition has been stabilized and rendered hydrophobic and oleophilic by treatment with lime.

4. A method of producing a treatment composition for combating the ill effects of hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge, the method being characterized in that it comprises treating raw sewage in the form of a sludge that has been depleted of foreign bodies with lime to provide a pH of the sludge of between about 9.5 and about 12, and reducing the moisture content to a maximum of about 15 percent by weight to provide a solid treatment composition.

5. A method as claimed in claim 4 in which the lime is added in an amount of from about 10 to 40 grams per litre of the sewage sludge based on a solids content of the sewage sludge of from about 3 to about 7 percent by weight.

6. A method as claimed in claim 5 in which the lime is added in an amount of about 20 to 30 grams per litre of sewage sludge.

7. A method as claimed in any one of claims 4 to 6 in which the lime is intimately mixed with the sewage sludge followed by drying to a cake having a moisture content of about 25 to 35 percent by weight followed by sub-dividing the cake into small pieces and then further drying it to a moisture content of less than 15 percent by weight.

8. A method as claimed in any one of claims 4 to 7 in which the cake is further dried to a moisture content of less than 10 percent by weight.

9. A method as claimed in any one of claims 4 to 8 in which the final dried treatment composition is graded through a mesh having a required mesh followed by packaging in sealed bags.

10. A treatment composition produced according to a method of any one of claims 4 to 9.

11. A method of combating hydrocarbon pollutants by microbial action on the hydrocarbon pollutants of microbes associated with sewage sludge the method being characterised in that it comprises contacting a treatment composition as claimed in any one of claims 1 to 3 or 10 with the hydrocarbon pollutants and affording the treatment composition time to absorb said hydrocarbon pollutants, followed either by removal of the treatment composition and disposal thereof or by working the treatment composition into associated soil as may be appropriate to the substrate on which the hydrocarbon pollutants were present.

12. A method as claimed in claim 11 in which the treatment composition is added to the hydrocarbon pollutants progressively at a controlled rate that may be continuous, semi-continuous or batch-wise until such time as newly added treatment composition fails to change colour to thereby indicate that there is no further hydrocarbon pollutant present to be absorbed by the treatment composition.

13. A method as claimed in either one of claims 11 or 12 in which the treatment composition is, subsequent to absorbing hydrocarbon pollutant therein, disposed of by working it into a body of arable soil.

14. A method as claimed in any one of claims 11 to 12 in which the hydrocarbon pollutants are treated on a body of water, or un-arable soil, and the treatment composition with hydrocarbon pollutants absorbed therein are removed from the formerly polluted site to a disposal site selected from a disposal dump and a body of arable soil in which case it is worked into the soil.