Diesel bug treatments


the water. In fact, slight moisture can increase engine power. In company with our sister


magazine Motor Boat and Yachting, we set out to test 12 of these treatments, assessing how effective they are at killing diesel bug and, more importantly, in producing a fuel that can be easily burned without blocking fi lters.


THE TEST It’s impossible to fairly test these additives outside a laboratory. At PBO we receive several letters each year claiming how effective an individual product has proved to be. While encouraging, these letters offer no scientifi c proof because they have not been compared with a control sample that did not receive the treatment. With that in mind, we contacted


Fuel QC, an Essex-based fi rm part of whose business is fuel testing, mostly for clients in the aviation and oil industries. Most of their work is done at their clients’ premises, but for our test they set up in a barn adjacent to their offi ces. We collected together 12 leading


products to take part in the test, of which seven are biocides and the others dispersants. On our behalf, Fuel QC sourced 200lt of fuel with mild contamination which was left to fester for three weeks, after which time it was judged to have a mid-range case of diesel bug consistent with a contaminated boat tank. We then siphoned the fuel into 13 one-litre sterilised glass jars: one for each sample and one for a control sample, which would be left untreated. Each sample was treated with the manufacturer’s recommended dose for an initial ‘curative’ treatment – maintenance doses will be lower.


TESTING FOR BUGS Several methods exist for calculating microbial activity, and one commonly used is to assess the presence of ATP (Adenosine Triphosphate). This is split into two types: free ATP (fATP) and cellular ATP (cATP). cATP is found inside the cells while fATP is free to move around in the host liquid. Until recently tests simply verifi ed


the quantity of ATP present, but newer methods such as those employed by Fuel QC specifi cally assess the presence of cATP. They do this by using an enzyme which causes the cATP in the sample to break down and release light. This light can be measured very accurately with a device called a luminometer, and the result used to calculate the amount of cATP present.


➜ FUEL QC’S cATP TEST, STEP-BY-STEP


1


Draw a sample of contaminated fuel into a syringe from the interface between the fuel and water – this is where the diesel bug will be found.


attached to a syringe. This removes the fuel, leaving the micro- organisms and debris in the fi lter.


2


Filter a sample of the fuel through a 0.75 micron fi lter


free ATP, leaving debris and cellular ATP. The fi lter is then dried with air passed through it from the syringe.


3


Wash the fi lter through with an acetone blend. This removes


4


Pass a lysis agent through the fi lter to break down the cells, and collect the fl uid in an extraction tube.


measured quantity of distilled water from a pipette.


5 Practical Boat Owner 534 May 2011 • www.pbo.co.uk


Dilute the contents of the extraction tube by adding a


6


Transfer a measured amount of fl uid from the extraction tube


to a culture tube and add two drops of the enzyme luciferase.


count of the sample, from which the level of cATP can be calculated to within +/- 5%.


7


Use a luminometer to measure the RLU (Relative Light Unit)


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