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Soil Remediation - Biological Hydrocarbon Treatment, Oil & Diesel degrading Bacteria

OilOff  CONCENTRATE for industrial use Guideline

In-situ bioremediation of Petroleum based contamination

 


                                                                                                                                                      

In an ideal situation most of the contaminated soils, sand and substrates could be removed from site for disposal / treatment and replaced with clean materials. Where spills and leakages have been identified and emergency response and containment action been taken, then a method of in-situ bio-remediation can be implemented providing the area is accessible and even if a spillage has seeped under buildings and fixed equipment installations etc bioremediation is the ideal solution for these scenarios as the bacterial cultures are predominately in water so will push through the lighter oils.

In practice this is sometimes the case, contamination may have gone un-noticed or just been ignored over many years and may have even reached the underground water table in severe cases.

In these situations a natural and relatively easy way of dealing with this situation is by utilising the power of natural micro-organisms to degrade the contamination. There are rarely sufficient indigenous bacterial cultures of the right species in the natural environment to cope with heavy contamination from noxious substances when large spillages or constant leakages occur.

By utilising specially selected ‘hydrocarbon- specific’ bacterial cultures which are present in ABR Hydrocarbon (data sheets included) they are able to break down the oil molecules and convert them to a harmless waste product consisting of Carbon Dioxide and Water.

By saturating the visible contaminated area and applying the ABR Hydrocarbon solution at the source of the spillage or leak we are also able to follow the flow-route underground to wherever the hydrocarbon contaminant has run. This is highly significant where there is a high water table or surface drainage nearby.

Regular applications are recommended at the start of any treatment programme and this can gradually be extended to weekly applications depending upon the speed of TPH reduction which can be checked by soil sampling and laboratory analysis. Water is a very important at the start of a treatment programme, the area must be kept wet at all times and not allow to dry out in hot weather.

Temperature is an important factor in determining the speed of TPH reduction. Bacterial degradation occurs more quickly at warmer temperatures.  Late Spring or Early Summer are ideal conditions to commence a treatment programme unless emergency situations prevail. In colder conditions warm water should be used when applying the ABR Hydrocarbon solution to the ground.   

If possible the area should be dug or rotavated to improve aeration. ABR Hydrocarbon also contains anaerobic cultures which can operate in conditions where little or no oxygen is present. It is also possible to add a little Sodium Nitrate when preparing the ABR Hydrocarbon solution in situations where oxygen levels may be very low in the ground.

Contaminated Land – an Industrial Legacy

The UK has an industrial heritage to be proud of but it has left us with a legacy of polluted land. Industrial contamination can cause serious harm to people, property, local water resources and the local ecology.  Contaminated land, and its clean-up, is of increasing concern to an environmentally conscious world. The need for more houses and offices has to be balanced with a commitment to preserve green land – this means that brownfield sites, many of which are contaminated, need to be redeveloped. Bioremediation offers a long-term, cost-effective and sustainable solution to cleaning up contaminated land.

Contaminated Land – Legislation
Reasons to clean up a site

  • The owner of a site, which contaminates or causes damage to neighbouring land/property, eg an oil leak that may migrate off-site, is at risk of civil action by the owner of the neighbouring site, ie being sued for negligence or trespass.
  • An owner of contaminated land may be criminally liable for breaching statutory legislation irrespective of whether he/she caused the contamination.  The forthcoming implementation of section 57 of the environmental protection act will mean that any land causing (or likely to cause) significant harm to humans or the environment could be subject to enforced remediation. 

Cleaning Up

There are a variety of ways in which the contamination can be treated, these fall into three broad categories: containment, separation and destruction. In each case, the level of contamination is monitored before, during and after treatment.

Containment – of the pollutants within a barrier that prevents migration of the harmful chemicals, eg excavation and disposal to landfill, and on-site barrier systems.
Separation – of the contaminants from the soil by a method such as soil washing or steam stripping. The resulting contaminated effluent is then treated biologically or disposed of off site.
Destruction – of the contamination by physical means, eg incineration, chemical means or bioremediation.

What are the bioremediation options?

Bioremediation companies use the natural ability of micro-organisms to degrade a wide range of organic contaminants. The microbes treat the contamination as a food source, and if oxygen is present (aerobic) they break it down to carbon dioxide and water. If oxygen is not present (anaerobic), they break it down to methane, carbon dioxide and hydrogen. Microbes cannot degrade inorganic contaminants, but they can be used to alter the contaminants in such a way that they become less harmful or are easier to remove from
the soil/water.

Bioremediation can be used to treat an increasingly wide range of contaminants and can be carried out ex-situ or in-situ. Ex-situ means excavating the soil or pumping out the groundwater before treatment, whereas in-situ means the soil/groundwater remains in the ground throughout the treatment.

Why choose bioremediation?

Bioremediation is an established technology that can reduce the risks associated with contaminated land and groundwater. There are many examples of successful bioremediation within the UK. Bioremediation can be more cost-effective than other methods and may sometimes be faster.

Bioremediation:

can treat a wide range of contaminants, including petrols, oils, tars, pesticides, dyes, solvents, some explosives and some polychlorinated biphenyls (PCBs)
allows you to re-use the land so none or little of the contaminated soil is sent to landfill – this saves transport and waste disposal costs
is a cost-effective option – it can be cheaper than incineration and soil washing and costs can be comparable with landfill or containment
can allow you to dig up and treat the contaminated land on site (ex-situ) – so reducing disturbance and transport costs
can allow you to treat soil/water in-situ – so you can treat contamination beneath buildings
destroys the contaminants so the site will be clean long-term – this can increase the value of the land.

Sensing contamination.

Biosensors at Work
Biosensors are used to detect the presence of certain substances and are particularly useful for those with toxic biological effects. This makes biosensors ideal for assessing the toxicity of industrial effluent, soil and sludge. The biosensors used in this example contain a strain of bacteria that emit light or ‘bioluminesce’ when they ‘eat’ certain nutrients or food, eg soil and non-toxic effluent. However, when the bacteria come into contact with toxins, the amount of light given out is reduced. Typically, a biosensor consists of a biological and an electrical component. The electrical part measures the reaction of the biological part (ie the amount of bioluminescence) and with calibration relates this to the amount of toxins in the sample.

Ex-situ methods

These are currently more commonly used than in-situ methods because they allow greater control of the process – you can see what is going on, monitor it easily and in cold conditions, cover or heat up the contaminated soil to speed up the process. Ex-situ methods are suitable for localised hot-spots of moderate to high contamination, providing they are easily accessible (0 - 5 m in depth).

Landfarming – the excavated soil is screened to remove large debris and the contaminated soil is placed in a bunded area where it is tilled and nutrients are added.
Composting – the large debris is removed and the contaminated soil is laid out in windrows (long rows) that are regularly turned to increase the oxygen supply to the microbes in the soil.
Biopiles – the contaminated soil or ‘biopile’ is actively aerated and any leachate produced is recirculated over the biopile.
Bioreactors – the contaminated soil is placed in an enclosed system. The treatment times are shorter than with other methods and less readily degradable contaminants can be treated.
Combinations of processes – such as soil washing or groundwater extraction followed by biological treatment of the contaminated effluent. 

In-situ Methods

These are used where appropriate, especially when the contamination is less accessible because of its location (either deep in the ground or beneath buildings), and when the contamination is at low to moderate levels and is probably evenly spread across the site.


Bioventing – the circulation of air through the ground above the water table to increase oxygen levels and stimulate biodegradation.
Air sparging – similar to bioventing, but allows treatment of contamination both above and below the water table.
Injection and recovery systems (‘pump and treat’) – a ‘virtual’ bioreactor is created in the ground. Contaminated groundwater is pumped to the surface, oxygen and nutrients are added and the water is then re-injected back into the ground.
Natural attenuation – the harnessing of natural physical, chemical and biological processes that take place in the ground to limit the spread of the contamination. It generally involves removal of the contaminant source, plus modelling of the contamination movement to prove that it will not have any significant environmental impact

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