Decantation (settling)

Decantation (settling)

Type of treatment: Pretreatment

Description:

Separation of a liquid phase (oil or oily water) from another phase (liquid and/ or solid) either on the field during response operations or after the response operations in specialized installations (refinery, deballasting stations, etc.).


Waste:

Liquid (may contain limited volumes of semi-solids and solid)


Situation/Possibilities in the country:

Equipment easy to implement in any country (requires tanks for settling and storage, and pumps able to pump water and oil).


Interest:
Allow separating oil and water from an oil and water mix (may also allow recovering sediment depending on equipment).
During response operations, it can be accepted that the separated water is discharged in the environment thus reducing the need for storage capabilities (on the working sites and on the spill response vessels recovering oil offshore).

Entry criteria:
Any oil, water and solid particle mix may be decanted to a certain degree.
Oil and water cannot be recovered directly from emulsified oil. The de-emulsification is necessary prior to decantation.

Operational constraints:

Requires personnel, a suitable site and storage capabilities for the recovered oil, water and solids (and/ or the possibility to discharge the recovered water in the environment).


Impacts:
- First decantation on the field during the response operations: the decantation has limited impact. It is often accepted that the recovered water is discharged in the environment (during the spill response operations).
- During waste treatment in specialized plants (once emergency response operations is completed): minimal if equipment is suitable, correctly operated and there are no oil leaks.

Legal constraints:

Refer to those applying to the discharge of water in the environment. Higher concentrations of oil in water (in the discharged water) are acceptable during spill response operations.


Efficiency:
Typical maximum flow rate depends on the pumps and decantation equipment.
- First decantation on the field during the response operations: decantation time depends on the oily water recovered (typical time is one hour). Pumps with typical flow rates of 10 to 50m3/ hr are used.
- During waste treatment in specialized plants: few cubic metres to 10’s of cubic metres per hour.

Cost:

CAPEX, mobilisation cost:
• First decantation on the field during the response operations: costs of rental/ purchase for storage tanks (10 m3 or more) and volumetric pumps (10 to 50 m3/ hr flowrate)
• None if existing installation

OPEX: varies depending on the type of installation; however costs are limited (around 50 euros/ per m3 of waste to decant).
 

published on 2019/12/10 14:45:51 GMT+0 — last modified 2019-12-10T14:45:51+00:00