Oil and gas production handbook An introduction to oil and gas production

particles bound to the oil/water emulsion. 
 

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The environmental regulations in most countries are quite strict. For 
example, in the Northeast Atlantic, the OSPAR convention limits oil in water 
discharged to sea to 40 mg/liter (ppm).  
 
Figure 6. Produced water treatment 
 
It also places limits on other forms of contaminants. This still means that the 
equivalent of up to one barrel of oil per day in contaminants from the above 
production is discharged into the sea, but in this form, microscopic oil drops 
are broken down quickly by natural bacteria. 
 
Various pieces of equipment are used. This illustration shows a typical water 
treatment system. Water from the separators and coalescers first goes to a