If you can collect it at the power plants, I'd suggest building a specialised sewage treatment-plant like facility with open basins, use plain seawater as inoculum and make sure that everything is aerated, warm and supplied with nitrogen and phosphorus.

Seawater most likely already contains most of the microbes needed for biodegradation. Just refilling the basins with fresh seawater and using the inoculum of bacteria that form in the basins should do. There will be a problem when freshwater is added though, as marine oil degrading bacteria tend to be sensitive to low osmolarity. Water temperature shouldn't be a problem in Sierra Leone, but in general, the warmer, the better.

Nitrogen and Phosphorus supply are the absolute essentials, but that can be done with relatively low dosages of industrial fertilizer. It's important though to check out how much N & P comes out of the treatment facility. Aeration is really important, too, as aerobes tent to degrade oil faster than anaerobes. Be aware of anaerobic microniches and patchiness in the basins when setting up such a facility.

One really important factor is to monitor whether or not some potentially hazardous components of the oil have long half-lifes and will not be degraded fast enough and thus get flushed out of the treatment facility. Eventually, there must be several stages of treatment.

The whole facility should be pretty low-tech and easy to be set up, dependent upon the legal requirements for the residual values of hydrocarbons in the wastewater. It's important to keep in mind flow rates, retention times of waste water and toxic residues that are hardly degradable. However, I'm not an engineer, so I can't tell what exact specification are needed. Maybe a bioengineer could add some additional info here.

It should be more easy to handle than a sewage treatment plant though, as there shouldn't be any pathogens in it.

Thanks Christoph for this valuable information.

Edward, you might also want to contact these people:

http://osei.us/

Their product, "Oil Spill Eater," appears to be highly effective, and they might have additional tips to help you out.

Thanks Gary!

Hi, Gary,

are there some independent studies on the efficiency of the product and/or do you have own experiences with it? I am just asking because there are a lot of products on the market, but few ever deliver.

One thing that seems to be pretty ineffective is everything based upon freeze-dried or similarly conserved bacteria.

Marine oil spill is an age old issue. For developing countries, bioremediation is the only solution. The marine environment itself harbours oil degrading microbes or else, strains like Pseudomonas putida with salinity tolerance ( inoculum) can be employed by aerial spray. And also N or P containing salts can be employed in the environment to augment or hasten biodegradation of the spill over oil

The unit for biodegradation of oil could be quantitative extracting the left over oil with carbon tetra chloride or measure the disappearance of oil peaks using GC

Hi Edward, there are some products that claim to bind and nutralize the marine oil waste quite successful. I have seen some tests on the trial and also did the afterwards testing on the effectiveness. The results were okay. For that indication I measured the carbon length in the spillage. The more oily particles with long C-chains the more pollution is still there and no degradation propcesses were running. The use of nutralization products is still expensive and probably marginal to use in developing countries or LDC. But that depends on how serious the spillage is. Hope that information gives you some more aspects to think about. Best regards Olaf

The answer all depends upon the details. In particular, concentrations and whether we have a dissolved or floating oil issue.

Agreed, but there must be a simple, cheap and feasible solution that reduces the bulk of the hydrocarbon contamination. You can do that only with a low tech sewage treatment approach. Also, the running costs of the process should be low. Additives could blow the budget.

Edward, are there any legal maximum hydrocarbon concentrations that the effluents are supposed to have? 9 ppm as in Europe? Where is the processed waste water supposed to go? Into the sea or into a river?

Regarding Olaf's answer: Plant-based cellulose absorbents are pretty cheap and could be locally grown. I remember a paper which used Kapok fibres as absorbents and they worked pretty good (Karana et al., 2011).

Waste water will be discharged into an estuary and UNEP's standards should be met.

OK, the UNEP concentrations for hydrocarbons as far as I have found on the web are 50 mg/l for less sensitve estuaries and 15 mg/l for "sensitive" ones (for whatever fits into the category). I think that is realistic, however, it would be easier if the processed waste water would be discharged through a pipe into the sea (about half a mile offshore). That makes it easier for marine microbes to deal with whatever remains from your hydrocarbons.

In any case, having at least a side stream of biological treatment producing waste eating microbes would provide a seed culture for the discharge allowing rapid removal in the actual environment. A small percent of the flow (10-20%) of the 15 mg/l or 50 mg/l physical/chemical treated discharge flow could be biologically treated down to near zero mg/l, with the generated biomass leaving the reactor and seeding the rest of the discharge so the environment could cut the 15mg/l or 50 mg/l down to ND levels, even when local currents and tides flush out a local area and remove most of the bio-degrading bacteria from the local discharge area.

I guess a lot of the answer depends on the effluent flow rate. There are a lot of solutions to this type of issue when low volumes/flows are involved, including natural sorbents, simple batch bioreactors, etc. Those solutions quickly become cost-prohibitive when flows are thousands of liters per minute. So, what kind of flows are you talking about?

One of my associates is presently building a 1200 l/min unit for biologically treating water containing MTBE, TBA and BTEX. For another application, I just roughed out the design for 15,000 l/min. The biological fluidized bed designs scale horizontally so increasing capacity just means more area and larger pumps.