Ocean Odyssey Research Project IS 93

Sunday, January 22, 2006

In-Situ Suggestion

It appears, based on the general outline, that this group intends on building a system that is capable of cleaning up, or remediating, petroleum that has washed up on the shore after an oil spill at sea. As I understand it, this system is not for cleaning up oil that is still floating on the water nor is it for cleaning up contamination at the sea floor. Instead this system is intended to clean up petroleum contaminated sand, gravel and mud, on beaches and in wetlands.

When oil is spilled onto the ground, it will immediately begin to flow down into the ground material. If the petroleum comes into contact with groundwater (water contained in the soil or bedrock), it will also contaminate this water. Since groundwater can be a significant source of drinking water, it is important that contamination of this valuable resource be reduced or eliminated.

Lets' divide on-shore petroleum contamination into two general phases: above ground and below ground. The contamination that is above ground will generally be pooled and can easily be clean up using a vacuuming device. I would suggest that your system might contain a vaccum that is capable of removing pooled petroleum. Above ground petroleum contamination can also be adhered to rocks. In general, this is the least dangerous phase of the contamination and will eventually be cleaned up by natural forces including sunlight (photo-remediation), oxidation and biodegradation (bacteria will actually digest the oil). Allowing natural forces to remediate an oil spill is called "natural attenuation" and is currently the most popular way to treat an oil spill. Mother nature is very good at cleaning herself up and she doesn't charge any money for her services.

The below-ground contamination is the most difficult to clean-up. Although natural attenuation does work underground, it typically takes much longer because there is no sunlight underground and oxygen is limited. Oxygen is critical for natural attenuation because the bacteria that digest oil are aerobic becteria, meaning that they require both a food source AND oxygen (O2) to live. Since natural attenuation of subsurface petroleum contamination is so slow, the toxic chemicals found in petroleum have a much lonegr time to do damage to the environment. This damage will include contamination of groundwater and long term harm to organisms, such as clams and mussels, that live below ground. Simply digging up the contamination is not genrally the best solution. Once the contaminated soil has been excavated, it must then be transported and disposed of. This is simply moving the problem from one place to another. The problem still exists. In addition, digging up the soil will destroy the below-ground ecosystms.

A popular way of treating subsurface petroleum contamination is (contamination of soil, mud, rock and groundwater) is by treating the materials in-place. This is commonly refered to as "in-situ" remediation. In-situ remediation can be accomplished in many ways. One way to do it is by enhancing the natural degradation of the petroleum contamination by bacteria which digest the petroleum compounds. This is called "in-situ, bio-remediation".

Most soils already contain bacteria that can digest the various toxic compunds contained in petroleum products. One way to accomplich in-situ bio-remediation is to enhance the activity of these naturally occuring bacteria by addition of nutrients and oxygen. Water is also necessary, so, if the soils are dry, addition of water to the contaminated material will also be necessary. Another way to do this is by adding special bacetria that has been developed specifically to digest petroleum compounds. There are many companies that sell these special types of bacteria. In addition, instead of adding oxygen (O2) to the contaminated soil, ozone (O3) can be added instead. Ozone is much more reactive than is oxygen and, therefore, enhances the activity of the aerobic bacteria much more quickly.

I would suggest that, instead of building a vehichle that can remove petroleum contaminated soil and rock, the vehichle should be a delivery system for specialized petroleum digesting bacteria and ozone. The vehichle might also contain a vaccum for removing petroleum that has pooled at the surface, but these types of vehichles already exist and are nothing special.

This vehicle would contain a tank to hold the bacteria/water/nutrient solution. The tank should probably have a capacity of 500 liters. The vehichle could also have an air compressor and an ozone generator. The compressor forces air into the ozone generator, which converts O2 to O3. The ozone is then forced, by the compressor, through several injectors located at the bottom of the vehichle. These injectors could be 1 to 2 meters long and would be like giant, stainless steel syringes that would be forced into the ground by a hydraulic device, taking power from the on-board power plant. Some of these injectors would be used to inject the bacteria/nutrient/water solution into the ground. The other injectors would be used to force the ozone into the ground. The vehichle would traverse the contaminated area, in a grid-like pattern, to ensure uniform and adequate coverage. The vehichle would stop, at pre-determined intervals along the grid, to inject the bacteria mixture and ozone. Applications could be repeated, accordingly, until the contamination has been reduced to acceptable concentrations.

It is imporatant to note that pure ozone is a deadly gas. Inhalation of pure ozone by humans will result in serious injury and/or death. This system must be equipped with on-board ozone sensors that will automatically shut down the system if ozone is detected on the outside of the vehichle. Also, to be doubly safe, the vehichle should probably be remote controlled, so that there is not chance of operator exposure to pure ozone.

2 Comments:

  • Thanks Peter. I know our team will benefit from your suggestions!

    By Blogger Fred Wright, at 8:33 AM  

  • Thank you for the advice it is greatly appreciated. Now I think that we will make the machine have two functions; the first being to clean up contamination above the ground and the second to clean up contamination below the ground. Also, now that we know all of the technical terms used when talking about an oil spill we can go slightly more in-depth. Along with that we will have more certainty when talking about our topic. Again, thank you very much, the information was very beneficial.

    By Blogger Robert, at 12:05 PM  

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