Filtering waste vegetable oil
Filtering waste vegetable oil
Waste Vegetable Oil (WVO) contains many different contaminants including food particles, water, Free Fatty Acids (FFAs) and animal fats. Many of these contaminants can be separated before the actual filtration stage in a settling tank. Oil is generally pre-treated in this way for about three weeks. The animal fats and water and much of the food particle contamination will slowly sink to the bottom and the good oil can be extracted from the top of the tank and pumped into the filtration unit. Waste oil needs to be stored and handled carefully as it can attract vermin such as rats, which can carry life threatening diseases.
Note that filtration alone cannot remove Free Fatty Acids or other chemical or biological containments.
Filtration equipment
Home built filtration plants often use 10" filter cartridges, due to their low cost and easy availability. Several are placed in series, with gradually reducing filtration grades. These are often described as 50/10/5/1 or similar, denoting an initial 50 micron filter followed by 10 micro all the way down to 1 micron. Such systems are driven by an electric pump such as the TAM105.
It is useful in such systems to have a pressure gauge on each filter cartridge in order to determine when a filter is starting to block.
 This section contains content relating to commercially available items or equipment.
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This is an example of a industrial filter farm using larger filters (courtesy of Goat Industries).
- Filter Farm 750
The filtration unit itself can be composed of cylindrical cartridges of different micron ratings. The one shown, the Filter Farm 750, has four cartridges plumbed in parallel and served by an air operated pump. These systems are generally low pressure devices and it is important not to exceed the rated pressure of the cartridges, some of which are as low as 0.8 bar. The pressure can be regulated very easily with the type of pump used, ensuring that the cartridges do not become distorted and leaky.
The waste oil can be heated to about 40 degrees C for faster flow through the unit, but again, care should be taken as the cartridges are even more prone to failure when hot. A post filter is used in this design to filter out finer particles and as insurance that the main filters are working properly. The performance of the machine can be monitored by pressure gauges positioned at different points in the plumbing and the speed at which the pump is operating.
