The limiting constraints in this respect are economic and environmental disposal standards.
First alum or ferric salts are added to waste-water. Lime is added when sufficient alkalinity for precipitation of the iron is not present. The waste-water is, then, gently agitated or flocculated to promote inter-particle collisions for agglomeration.
The resultant suspension is, then, allowed to settle in a sedimentation basin. In some cases where oil content is high, floatation is used. This step is followed by filtration through a rapid sand filter or through a multi-media filter.
Beaches several possible approaches have been studied for restoration of oil contaminated beaches. These include:
1. Ploughing under and covering with uncontaminated sand.
2. Physical removal of contaminated material.
3. Detergent cleaning in combination with mechanical tilling.
4. Combination of the above.
In general, any procedure that applies to sand beaches can be extended to gravel or shingle beaches, but with greater difficulty.
Physical removal of the contaminated material, with appropriate earth moving or farm machinery, appears to offer the best solution. When the oil is relatively unweathered and, hence, mobile, addition of absorbing material such as straw, saw dust or clay can greatly assist. Timing of the cleanup operation to correspond with high tides can minimize the effort.
Flowing under is unsatisfactory because wave action ultimately causes resurfacing of the oil.
Rocky Coasts, Sea Walls and Structures Detergents were used extensively in England in combination with high pressure water hosing. Burning oil from sea walls was attempted but the only apparent cleaning was achieved by spelling of the concrete surfaces. Where equipments can be brought into play, steam cleaning with detergents can be effective.