Bioremediation: the easy way to solve difficult and unwanted cleaning problems

Bioremediation: the easy way to solve difficult and unwanted cleaning problems

Some cleaning problems are difficult and also have environmental consequences. For embedded oils, fats and greases including contaminated land, regular cleaning with detergents or dispersants is difficult and not all that effective.

To clean by regular detergents, you will need to wash the surface, scrub it, then rinse it off sending more grease and emulsions down the drains or into the ground water. The waste is still oily and it then becomes someone else’s problem; as it is classed as hazardous waste it is expensive to process. If in the ground water and sub soil it stays there for years, so that the land which could be productive is useless and contaminated.

The easier way is to use bioremediation. Cultivated strains of bacteria are used to digest oils, fats and greases and they are left to get on with the job without interference. All that is left is carbon dioxide and water. It is the enzymes which the bacteria produce which is the actual chemical process, so as long as there is enough food for the bacteria to digest and the temperature is right then nothing will stop them reproducing and digesting. When the food supply runs out, they die off; when the temperature drops to cold, their activity slows down to almost a stop. Although some strains will work at around freezing point, these are not the usual commercial strains, most of whom optimally work at around 40c.

How does bioremediation work? What do you do with it? Simple really – you just spray or dose the area or surface with an active level of bacteria in a substrate of enzymes and cellulose (food) to establish the colony and then monitor it.

What do you see when you’ve started the bioremediation process? The oils fats and greases begin to dissolve and the surfaces including soils begin to look clean as the levels of contamination drop. Associated smells also go, often rapidly.

What is the downside to bioremediation? Not much. Temperature is obviously crucial and bioremediation within an enclosed space needs close attention since it requires adequate ventilation. Time is the biggest problem. If the temperature and food supply are on the low side then expect it to take days to begin to work. Hence a very rich bacterial mix is usually applied together with starter enzymes, food supply and often surfactants, to get the colonies established at some point. One thing is guaranteed though. You will not see results overnight, but leave it for a week or so and then you will.

The other, not often stated problem is the nature of the bacteria used. Usually these are aerobic bacteria, requiring an oxygen rich atmosphere to work. However, anaerobic bacteria which work in the absence of or limited supply of oxygen may outbreed the aerobic bacteria and at that point the bioremediation fails. You will know this by the distinctive smell of rotten eggs or sewerage. Ventilation is required. In an area where there is sensitive electronic equipment the over production of anaerobic bacteria may cause damage to the equipment.

Often though it is a commercial strain of anaerobic bacteria which proves better at digesting oils and hydrocarbons and care is needed where these are deployed.

Where will you use bioremediation? Settling ponds, rivers, ports and harbour sides, hydrocarbon – contaminated land, in oil water separators and holding tanks, in ballast water tanks, in oily water containment, on surfaces contaminated by years of grease and oils, for example ex-machine shops, grease traps in food preparation areas, sewerage treatment and septic tanks, the list is endless.

Regulation for bioremediation? Obviously you do not just spray a load of foreign strains of bacteria onto sensitive areas. You do an assessment first. There isn’t much in the way of regulatory framework for this procedure but its benefits far outweigh its drawbacks.

Other ways of bioremediation

It’s not only bacteria which can be used for bioremediation. Plants are also used to remove hazardous wastes from soils. Many pollutants such as heavy metals are also toxic to bacteria, but some plants may absorb in their leaves, quite happily, metals such as lead cadmium and uranium, arsenic and zinc from soils and water. This is known as phytoremediation and is an accepted way of remediation. Not all plants can be used, only those with a very high tolerance for the pollutant. Many plants act as calcium sinks – sorrels, beets and rhubarbs for example – but alpine pennycress is known to accumulate very high levels of calcium and zinc which would be toxic to most plants. Bracken is a well –known accumulator of arsenic storing it at 200x it is present in the soil. Sunflowers and hemp are used on sites to absorb uranium. Willow and poplar trees are also good bioaccumulators but will also stabilise soils limiting leaching of pollutants.

The plants themselves may have an effect only as far as the roots will reach. The pollutants may leach into the subsoil and stay there. Therefore at some point the soil may need to be turned and the lower levels sown for shorter rooting plants to continue the extraction process. This is a long term solution over several harvests but is slowly being introduced as a viable solution.

It is relatively inexpensive to establish a phytoremediation system but you do have to think long term. It is aesthetically pleasing but the plants cannot be used as a food crop for animals or humans, nor returned to the soil as compost. Phytomining is the solution whereby the accumulated pollutants – which are very useful metals- are recovered from the biomass.

For help with your bioremediation project contact Futureclean Assured Systems today, although we work with bacteria rather than plants!

For more information as to how Futureclean Assured Systems can help you with your bioremediation proposals, contact us today.

Rafael Cobos