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Separation Efficiency | |
| Oily water separator 'performance’ can be measured in a variety of ways. Typical examples of separator ‘performance’ measures may include (see right): | - Flow rate capacity
- Ability to operate without service or maintenance
- Reliability
- Operator training and attention required
- Oil separation efficiency
- Suspended Solids separation efficiency
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| Usually it is specific client requirements that determine which of these, and other measures, are most important. A primary criterion is oily water separation ability. This is often the main criterion in determining final discharge water quality. Under a given standard set of conditions the effectiveness of the treatment equipment is judged in terms of efficiency of oil removal, under specified conditions. Separation efficiency can be expressed as follows: | Eff% = 100 x ( Cin - Cout/ Cin) Cin = feed inlet concentration (mg/l)
Cout = discharge outlet concentration (mg/l) |
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| Oil separation efficiency can be objectively accessed by examining the separator oil droplet size Vs separation efficiency curves. For higher quality separators these curves should be readily available from manufactures. Manufactures should also be able to confirm performance to these curves by independent tests. The purpose of oily water separators is to obtain clean water. However claims of a separator being able to achieve, say less than 10 mg/l discharge are meaningless and deceptive without recourse to oil droplet size performance curves.
The more efficient a separator is at removing smaller oil droplets the more powerful it is. Typical Ultraspin performance curves show it is able to remove more than 90% of 20-micron oil droplets. Many plate pack manufactures recommend that these separators not be used if oil droplets are less than 60 micron. Some manufacturers claim high performance but make this claim under very favourable conditions such as very light easy to separate oil. Some manufacturers are not able to produce qualified supporting technical information to match performance claims. | The picture above shows typical performance curves for four separators (Click on image to see a larger picture) : - Ultraspin OS20 separator (one pass and with recycle)
Typical High Quality Plate Pack (7 mm plate spacing Typical Budget Plate Pack (12 mm)Typical simple gravity settling tankMore powerful separators have a number of advantages including:- Obtain better quality discharge water
- Meet or exceed Local and National Trade Waste discharge standards
- Meet or exceed future discharge standards
- Deal with accidental spills
- Tolerate higher strength non-“quick-break “detergents and cleaners
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