Oily water

All waste water except for deballasting water is collected in a single network and undergoes complete physicochemical and biological treatment (see Fig. 61). 

It amounts to an average flow rate of around 500 m -h. After treatment, 50% is discharged and around 50% recycled as make up to cooling towers. 

Primary oil separation is carried out in two in-line API-type oil separator stages. The separators are very large and are equipped for skimming off surface oil alone. Bottom sludge is removed periodically (once every three years for a compartment). 

The trickling filter is made up of random plastic materials and has an original feature. It is fitted with a sampling basket that runs down to the bottom and is weighed once a month. In this way the fouling of the bed is measured and a decision can be made as to when it should be washed alkaline washing one or twice a year). 

Total salinity of treated water is lower than 2 gT thereby allowing it to be recycled to cooling. 

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When water is produced along with oil, the separation of water from oil invariably leaves some water in the oil. The current oil-in-water emission limit into the sea is commonly 40 ppm. Oily water disposal occurs on processing platforms, some drilling platforms, and at oil terminals. The quality of water disposed from terminals remains an area of scrutiny, especially since the terminals are often near to local habitation and leisure resorts. If the engineer can find a means of reducing the produced water at source (e.g. water shut-off or reinjection of produced water into reservoirs) then the surface handling problem is much reduced. 

Another type of gravity separator used for small amounts of oily water, the oil interceptor, is widely used both offshore and onshore. These devices work by encouraging oil particles to coalesce on the surface of plates. Once bigger oil droplets are formed they tend to float to the surface of the water faster and can be skimmed off. A corrugated plate interceptor (CPI) is shown below and demonstrates the principle involved. However there are many varieties available. Plate interceptors can typically reduce oil content to 50-150 ppm. 

In a gas flotation unit, air is bubbled through oily water to capture oil particles which then rise with the bubble to form a scum at the surface of the flotation unit. The scum can be removed by rotating paddles. Chemicals are often added to destabilise the inlet stream and enhance performance. 

In this diagram the key features are A - Diffusion baffle this serves four roles. First to dissipate the velocity head, thereby improving the overall hydraulic characteristics of the separator. Next, to direct incoming flow downward and outward maximizing the use of the separator volume. Third, to reduce flow turbulence and to distribute the flow evenly over the separator s cross-sectional area. Finally, to isolate inlet turbulence from the rest of the separator. B- Internal chambers In the sediment chamber, heavy solids settle out, and concentrated slugs of oil rise to the surface. As the oily water passes through the parallel corrugated... 

The area below the stack and windbreaker is paved with concrete, surrounded by a 200 mm curb, and graded to a central drain point from which a drain line is routed to a manhole in a vented section of the oily water sewer. The water inlet should be sealed and the manhole should be located at least 15 m from the windbreaker. 

The 300 mm water seal is maintained by the location of the overflows which discharge to the oily water sewer through the primary seal loop. The water... 

The oily water, as oolleoted duvioB Ihe process of distillation, is milky. Specimen B represents Ihis water as separated from tho od and mixed with Specimen A... 

NOTE Where the fuel tank contains oily water emulsions, sludge, and particulates, the effectiveness of any fuel treatment is directly related to the ability of the additive to penetrate and attack the sludge or emulsion mass. Simply feeding the treatment to the tank does not work. Typically, some form of power-injection equipment is employed to inject the chemical under 100 to 200 psig pressure. Agitation of the entire tank contents also is required and can often be carried out using the same equipment. 

There are several drainage mechanisms are employed at petroleum and related facilities - surface runoff or grading, spill containment (diking), gravity sewers (oily water and sanitary) and pressurized sewer mains, and lift station collection sumps. 

Common practice and a general guide is to prevent combustible vapors from transmitting from one process area to another process area, generally 15.2 meters (50 ft.) or more away. Usually unsealed receptacles, such as drain funnels, tundishes, drain boxes, are routed to the nearest local sealed catch basin and then into the oily water sewer main. The unsealed receptacles are only allowed in the same process area equipment where if vapors where released from an adjacent unsealed receptacle it would be "immaterial" due to the proximity to where the liquid is being drained and would normally emit vapors. 

In some cases a closed drainage system can be used which drains process components directly into the oily water sewer. This has the advantage of avoiding releases of vapors in any instance, but assurance must be obtained that back pressure from one drainage location will not backfeed liquids into another drain point when two valves are open simultaneously or other drainage valves can contain any backpressure on them from other drainage sources. 

A process oily water sewer system is a convenient location to direct oily wastes. The oily water system normally collects into a sump. If several lines connect into a common header, care should be taken to prevent backflow into another outlet source. In such cases use of an air gap, i.e., drainage in to a collection ftinnel has be advantageous. 

Oily water gravity and pressure sewer systems Ship, rail or truck loading facilities Storage Tanks for flammable liquids... 

Oily water sewer (OWS), vents and drain funnels. 

Open drain ports should be avoided and separate sewage and an oily water drain system should be provided. 

No gas detector should be located where it would be constantly affected by ambient conditions such as surface drainage runoff, sand, ice, or snow accumulation. Special consideration should be given near open sewer grates and oily water drain funnels were frequent alarms may appear due to vapor emissions. 

Where drainage provisions are provided to the battery room, the fluid should first collect into a neutralizing tank before entering the oily water sewer system (OWS). 

In addition to a system for disposing of rain, fire, and wash-down water, many process units require special dedicated sewer systems (i.e., chemical and oily water sewers) for routine nonemergency drainage of process waste due to environmental, waste disposal, cross-contamination, or reactivity reasons. Chemical, process, or oily water sewers are usually not appropriate in capacity or purpose for use in drainage of large uncontrolled process spills, rain water, or fire water. 

Chemical, process, or oily water sewers are typically designed to receive drainage directly from tanks, vessels, pumps, equipment, and piping. Their... 

Process, chemical, or oily water sewer system branch and lateral lines should enter main lines through vapor-sealed and vented manholes. Branches and laterals in clean or storm water drainage systems may enter main lines without vapor seals if liquid-sealed catch basins are used on the inlets to these branches and laterals. 

The surface pressure exerted by the film is as we have noted according to Traube and Langmuir defined by F = (T O oily waters... 

Triethanolamine (N(C2H40H)3) is an oily, water-soluble liquid with a fishy odor and is produced by the reaction between ammonia and ethylene oxide ... 

Many salt water dis(x sal (SWD) well projects operate satisfactorily in spite of oily water. The well simply has sufficient jjermeahilily to accept the waste water volume requirements. 

Pretreatment. Minimizing the degree of oil contamination in produced water starts with the crude oil emulsion treating system. It is possible to economically operate an emulsion treating system to produce a low bs w. (basic sediment and water) oil at the expense of exceptionally oily water. 

Of course this would be foolhardy if nearly oil-fee water is required for downstream operations. Therefore, the cost of oily water cleanup must be considered simultaneously with the cost to meet required bs w limits for the crude oil. 

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