The wrong mix01 February 2006

Since The Control of Pollution (Oil Storage) Regulations 2001 came into effect, much debate has ensued regarding oil storage, and the challenges of avoiding water contamination in particular. But what are the real ins and outs of oil storage? Firstly, let us examine the Regulations. These apply to all commercial, industrial and institutional installations where more than 200 litres of oil are stored above ground (in one or more containers) as well as larger domestic installations. All types of oil are covered by these regulations, including petrol, diesel, vegetable, synthetic and mineral oil. The exception is waste oil, which is covered by the Waste Management Licensing Regulations. Storage tanks have to be bunded, plus there are also specific requirements for fitting additional equipment - especially where diesel is being used in vehicles and plants.

According to the Environment Agency (EA), in 2003 there were 4,656 incidents (down from 5,684 in 2001) of substantiated oil and fuel water pollution affecting the environment. The reduction is due to the implementation of the Oil Storage Regulations. The four significant causes of oil and fuel incidents are tank failure, tank overfilling, pipe failure and vehicle fuel tank failures. According to the EA, cleaning up spilt oil and fuel actually costs UK businesses between £15m and £56m per year, but more importantly, these incidents could have been avoided if best practice was followed.

On the other hand, there are no rules or regulations available on maintaining the actual fuel inside a storage unit. Dirty fuel can be a costly nuisance, ranging from equipment downtime to cleaning up any contamination in a tank and the environment.

The main problem with fuel contamination is dirt, water and consequently bacteria or 'diesel bug'. Actual dirt is not really a problem as this tends to be removed by filters set up within most equipment and just comes down to proper in-house maintenance procedures.

Water fuels problems
Water, on the other hand, can lead to a number of problems, from degradation of fuel quality and subsequent engine and pump performance, to microbial/bacterial contamination, corrosion (filter plugging), and damage of the entire storage system. This applies to both underground and above ground storage systems, and to nearly any fuel - diesel, heating oil, and more recently biofuels such as biodiesel and bioethanol.

In terms of the bacteria, water, warmth, and darkness are all the perfect ingredients for bacterial growth. These organisms grow at the interface between the fuel and the water, where they multiply at a phenomenal rate (they can apparently double in number in as little as four hours). This leads to fuel degradation and the bottom of the tank becomes filled with a green or black slimy substance namely sludge, water, acids and other byproducts of their metabolism.

Ultimately, this can affect the entire storage system, whether the tanks are steel or plastic, tank linings, seals and hoses, pump components, filters and valves, including overfill prevention devices. In the worst case, product leaks can cause environmental damage, leading to costly clean-up operations.

To deal with water contamination, the old adage works best here, in that prevention is better than cure. Preventing water contamination is all about good housekeeping practices, for example:

- Monitoring and checking for water, either with automatic tank gauging systems as long as the sensors are maintained, or manually with water-finding paste.

- Inspecting the system for any damaged or loose fittings, as well as product and spill containment buckets.

- Using water-sensitive fuel filters and watching for slowed-down fuelling.

With the number of ways in which water can infiltrate systems, it is almost impossible to exclude water entirely from hydrocarbon fuels. According to a recent survey of independent fuel distribution companies, there are various methods available to deal with water. The first of these is known as 'dewatering'. The recommendation is to regularly remove the water by employing a specialist company, and then use a waste management company to dispose of the oil. However, this is time consuming (to pump the fuel out) and expensive. Secondly comes the topic of biocides. It is not always possible to remove all the water, so another recommended option is treating storage tanks with antimicrobial pesticide (biocide) on a regular basis. Biocides are used as a prophylactic guard against an infestation. They can be added to fresh fuel, and the poison prevents the growth of any microbes. Alternatively if there is already an infestation, adding the biocides kills the growth, which then settles to the bottom of the tank.

Biocides use toxic poison to kill the microbes, which end up on the tank bottom creating corrosion and filter plugging. They do not remove the water that has settled at the bottom of the tank. Therefore, the biomass decays in the water layer forming organic acids, which then deteriorate the fuel, which in turn corrodes the tank, lines, and injectors. Moreover, the bacteria develop a resistance to biocides.

And many biocides must be metered into the fuel carefully, as they will turn to a thick sludge if overdosed. Additionally they are harmful to the users, and the aquatic environment when spilled. Once dosed, the fuel is dangerous. Biocides contain toxic chemicals that have been banned in many areas. They cannot be used in on-road diesel fuel for the reasons above.
The third option in dealing with water is through the use of enzyme products. Additives are available that are made up of enzymes, a mixture of complex sugar molecules, which are 'packaged' into a hydrocarbon fluid of short carbon chain length, such as kerosene. The manufacturers state that the enzymes work in conjunction with two components - the sulphur and the metallic ions - that are present within standard fuels. These are the two components that refiners and governments worldwide are reducing in fuel, as they are harmful to the environment! It is well known that enzyme function is interrupted (the enzyme is denatured) by changes in polarity, pH, heat, and ultra violet (UV) light. These are factors that can destroy enzymes, or inhibit or weaken their effects in fuel.

Additionally, the manufacturers of these products recommend that, prior to treatment with their additive, the water has to be pumped out. Also that enzymes are heat sensitive and so should not be subjected to higher temperatures, as this may destroy the enzymes, contributing to the build-up of solids in the filters. Unfortunately, most modern engines operate at extremely high temperatures and pressures.

A further option in the treatment of water in fuel is through the use of magnets. Several companies have developed magnetic devices that create an optimum magnetic flux field directly responsible for destruction of the cell membrane in microbes. By routing the fuel next to a strong, permanent magnet, or series of magnets, cell reproduction can generally be halted and the existing microbes killed.

There are several issues here, including the fact that magnets do not eliminate the water-fuel interface where the microbes are formed at excessive rates. Secondly, it is clear that the fuel must be circulated through these units and over the magnetic field to be effective. So any equipment sitting unused for long periods would need to be started up regularly in order to pass all the fuel through the magnets and other filters.

According to the one manufacturer the debris stays randomly suspended in the fuel and, due to their submicron size, will easily pass through engine components and burn with the fuel. Given that engine components (for example fuel injectors) are designed specifically with submicron tolerances, it is difficult to see how effective this mechanism is.
One final alternative is to use absorbent beads. These work on the basis that the silica gel type molecules absorb the water contamination. They tend to get saturated after a period of time and become ineffective as they return the water back to the fuel. At the end of their life, the saturated tubes have to be disposed of through a waste management company (which is expensive).

The solution?
The solution may well be to use an additive that completely 'removes' any free water from the fuel - thereby eliminating the formation of an interface between the water and fuel layers, leaving no opportunity for microbial growth.
One such additive is known as AV100. As the water is 'absorbed' into the fuel, it ends up being burned off/used up thus preventing it from causing any damage. This additive provides an inexpensive environmentally-friendly solution to water contamination and its consequent disposal issues. By simply adding it to the fuel with gentle agitation, the AV100 treatment binds the water and the fuel together in such a way that the water becomes part of the fuel, essentially 'diluting' the fuel so it becomes fuel + water + additive. This eliminates the need for biocides (or other treatments) and reduces expensive clean up, maintenance and downtime.

In the motor industry, technology based on water injection and fuel and water mixtures has been around in various forms over the last 50 years. The objective behind this technology is that it improves atomisation of the fuel/air charge on injection, facilitates improved combustion and lowers peak combustion temperatures.

The additive technology works on similar principles thus enabling any fuel it is treating to burn more efficiently - it has been shown to improve boiler efficiency with a 2% water contamination in the fuel, at the same time reducing greenhouse emissions CO2, NOx and black smoke.

The idea here is to deal with the water removal, but with a slight twist. Recommended wisdom says de-water; this technology does this and offers some environmentally friendly benefits as well.

Any readers with comments or questions on this article should email paula@paulazard.com

SOE

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