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Pressure washing is an unpleasant task that on many farms is given to the lowest paid, poorly trained operatives. Is it a surprise that the most common reason for failure of many biosecurity programmes is to fail to adequately clean a building or piece of equipment prior to disinfection? This means that the disinfectant has to eliminate more pathogens, and has to do so with grease, biofilms, limescale and organic material in the way.
The need for good cleaning is easily shown by looking at a typical pig finisher building on removal of the pigs. It has a typical bacterial count of 50 million/cm2. Washing it with cold water can reduce it to 20 million/cm2, but by using a hot wash and heavy duty detergent the count is reduced to 100,000/cm2 – a reduction of over 99%! This is before disinfection! The target after disinfection is 500/cm2 or less. So we must clean properly before we disinfect, and remember we haven’t even mentioned other pathogens such as viruses yet.
Use a good cleaning programme
Whether you are cleaning a building, a piece of equipment or a vehicle it is essential to follow a complete programme. By working through this step by step the chances of failure are reduced.
1.
Remove all gross organic debris including dried on debris where possible. Take away from the cleaning site. Vacuum ledges and drain slurry pits where possible.
2.
Remove all moveable equipment and clean in a similar way.
3.
Pre-soak with water, leaving for 6 – 24 hours. This has been shown to reduce the washing time by nearly 50%.
Provided by DuPont Disinfectants - www.ahs.dupont.com
4.
Then apply a farm specific heavy duty detergent by foaming and leave for the recommended period (usually 30 minutes). Normally this is an alkaline product.
Provided by DuPont Disinfectants - www.ahs.dupont.com
5.
Now you are ready to pressure wash. Start at the top of the target and work down to the bottom. Pay attention to areas where dirt accumulates such as cracks and corners and avoid or remove any splash-backs. Visually check that the area is clean and repeat if necessary. Note that it has been shown that the areas around drinkers and feeders are frequently the worst cleaned areas so these need added attention.
Provided by DuPont Disinfectants - www.ahs.dupont.com
6.
Clean moveable equipment in the same way but remove from the contaminated wash area as finished.
7.
Once completely clean allow to dry before disinfection. Where conditions slow this use auxiliary heating. Remember dryness is your ally in killing pathogens.
Do you need hot water and detergents?
Canadian workers measured the time for washing identical pig pens under certain conditions and the results are shown below.
| Wash procedure | Time (minutes) | Time savings % |
| Cold water alone | 68 | 0 |
| Hot water alone | 53 | 23 |
| Pre-soak, cold water | 41 | 39 |
| Pre-soak, cold water, detergent | 36 | 46.5 |
Interestingly using pre-soak, hot water and soap was slightly slower due to problems seeing through the steam. These figures are important, as not only do they represent a time saving, but they mean less water is used and less effluent produced – both of which represent a real cost saving.
Removing other deposits
We have already talked about the role of heavy duty detergents in removing grease and organic debris. However there are circumstances where other deposits can reduce the efficacy of cleaning.
1.
Where build-ups of limescale occur. Here you will need to use an acid detergent. If deposits are really stubborn this may have to be left in contact with the surface for a longer period. If limescale is a special problem detergent rotation programmes are adopted using an acid detergent every third rotation.
2.
Biofilms can build up on surfaces and in water systems. These are polysaccharide matrixes provided by bacteria which adhere to the surface and protect the bacteria and other pathogens from washing and disinfection. It is a common misunderstanding that these can be removed by detergents alone. This is not correct and oxidative disinfectants are needed to achieve this.
The water system
During the cleaning programme it is important to pay attention to the water system. If possible this should be drained and drinkers removed and cleaned. Then refill with a suitable efficient but safe disinfectant. Finally flush through with fresh water. If this is not possible due to a non-drainable system flush the system through with a suitable disinfectant, leave for a period and flush with water.
A word about design
It is much more difficult to achieve a good quality of cleaning if the surface you are trying to clean is particularly pervious to water (for example wood) and has many cracks and hidden areas. It is important for all designers of buildings equipment and vehicles to develop them with an easily cleaned surface and in a way to make cleaning easy. A little thought and money at this time can save a lot later on. At the same time it is important to maintain buildings and equipment so as to reduce problem cleaning areas.
Is It all worth it, and if it is so good do I really need to disinfect?
The benefits of good cleaning combined with good disinfection were shown by the same Canadian workers. They measured the time taken for pigs to grow from 25 – 110kg in pens treated with different protocols and demonstrated that while the use of detergents or disinfectants were of benefit when compared to plain washing, the biggest benefit was from the combination of wash, detergent and disinfectant.
| Washing Method | Disinfectant | Days from 25 – 110kg | Improvement % |
| Plain wash | None | 98,1 | 0 |
| Plain wash | Peroxygen | 95,4 | 2,8 |
| Wash + detergent | None | 95,6 | 2,6 |
| Wash + detergent | Peroxygen | 92,9 | 5,2 |
So the message is clear – you need to adopt a high quality cleaning programme using farm specific heavy duty detergents prior to undertaking disinfection.
