/نظرية عمل وحدة فصل الزيوت عن مياه الصرف الصناعى

Procedure for the Design and Sizing of an Oil/Water Separator
by

GENERAL.DR
BAHAA BADR

TECHNOLAB EL-BAHAA GROUP

(API, Enhanced Gravity "Coalescing") for the Separation of Oil from Water

This procedure can also be used for the design and sizing of a "Liquid Phase" Separator (for the separation of any "Immiscible" liquids of different specific gravities)

Table of Contents

1. Oil Water Separator Theory of Operation

2. Public Works Technical Bulletin 200-1-05 5 December 1997

oil/water separator selection, installation, and maintenance: lessons learned

3. Test for Determination of Susceptibility of Separation

4. General Considerations

5. Oil Water Separator Decision - Flow Diagram

Determining if your process require an oil water separator or separation system

6. Oil Water Separator Design - Flow Diagram

Basic process in the design of an oil water separator or separation system

7. The Impact of Micron Removal Efficiency on Oil Water Separator Design

8. Oil Water Separator "Oil Droplet" Sizes, Definitions and Meanings

9. Sizing the Separator or Separation System

Inputting the Accumulated Data to the Hydro-Flo Oil Water Separator Sizing Spreadsheets to accurately size an oil water separator or separation system for your application

10. Comparing and Evaluating Oil Water Separators and Separation Systems from Different Suppliers

11. Designing Coalescing Oil/Water Separators for Use at Army Washracks

Reviewing and filling out the Hydro-Flo Technologies "Application Questionnaire" will also help you gather pertinent information required for the proper design and application of oil water separators and separation systems.

Oil/Water Separator Theory of Operation

Basic concepts and theories of oil water separation

If you are unfamiliar with basic oil water separator design principles, a review of the "Oil Water Separator Theory of Operation" might prove helpful.

Oil/water separator selection, installation, and maintenance:


a. Purchasers of oil/water separators are often ignorant of the device's capabilities and constraints.

They do not know which types of separators will provide the desired results for a particular application and rely on manufacturer's literature or sales representatives for unit evaluation.

However, vendor literature normally does not address important characteristics such as
highly variable flow rates and variations in suspended solids and oil concentrations.

Rather, performance is advertised according to ideal conditions of consistent flow and oil concentrations, and no other contaminants present.

There are no industry standards that manufacturers must meet.

Test for Determination of Susceptibility of Separation

of Oil From Water in a Gravity Type Oil Water Separator
SPECIAL NOTE:

In the Hydro-Flo "Test for Determination of Susceptibility of Separation of Oil From Water in a Gravity Type Oil Water Separator" we have expanded on the API bench test to give you a reasonable procedure for calculating the removal efficiency required to meet your target effluent quality.

General Considerations
Oil water separators are typically considered very simple devices. However, several factors that could potentially affect safety, efficiency, and proper management must be given careful consideration prior to the installation or modification of any oil water separator or separation system:


1. Flow Rate

In general, separators are sized by the flow rate verses the separation chamber's effective surface area (or projected surface area in the case of a "coalescing" or parallel plate type separator).

Therefore, the effectiveness of any oil water separator is affected by the flow rate. The slower the flow, the better the results.

2. Design Capacity

An oil water separator has upper limits to the amounts of oil and sludge that can effectively accumulate while it is in operation.

If too much oil accumulates in the receiving and middle chambers, it may flow into the wastewater outlet chamber and end up being discharged to the environment.


Proper oil water separator design will allow for the removal and storage of accumulated oil and sludge from the separator to ensure that the accumulated products do not effect the operation of the separator.

3. Emulsifying Agents

Detergents and soaps designed to remove oily grime from equipment, vehicles, or other components can adversely affect the operation of a gravity oil water separator.

These types of surfactants, or "emulsifying" agents, are specifically formulated to increase the dispersal of oil into water, which is why they are such good cleaners.

When these soapy wastewaters enter an oil water separator, it takes significantly longer for the oil to separate, if it can, from the water. Excessive use of detergents can render an oil water separator inefficient by completely emulsifying oils into the wastewater stream and allowing them to pass through the system.

Low-emulsifying soaps are available that allow oil separation to occur more quickly after the soapy water enters the oil water separator.

4. Maintenance Practices

The ability of oil water separators to function properly depends upon the timely performance of required service and maintenance.

Oil/water separators must be monitored and maintained by competent personnel who understand how the systems operate.

Oil/water separators should be given the same close attention given to any other important piece of equipment.

The operators, users, and maintainers of the oil/water separator must clarify who will be responsible for monitoring, inspecting, maintaining, and servicing the system.

Frequent inspections should be made of the system and all associated piping, valves, etc. to prevent operational and mechanical failures or inefficiencies.

Sludge and oil need to be periodically removed from the oil/water separator to keep it operating properly.

Additionally, leaks from oil/water separators can result in environmental pollution, which can trigger costly investigative studies and cleanups.


Rigorous implementation of an OWS inspection and maintenance plan can prevent

discharges from the oil/water separator that may contaminate the environment.

5. Suitability of Oil Water Separation System to Process

An oil/water separator designed and installed to meet a past process requirement may no longer be suitable when process requirements change, and/or the original maintenance plan is no longer followed.

An oil/water separator that is put to a use for which it was not originally designed may be damaged or may not function properly, and could become an environmental liability.

For example, an oil/water separator designed to receive the wastewater discharge from a small engine wash rack will not be able to properly treat larger wastewater volumes from washing the exterior of locomotives.

Process changes can also result in changes to the physical/chemical makeup of the wastewater being treated by an oil/water separator.

Finally, process changes may also necessitate the modification of storm water and wastewater drainage systems.

Such systems should remain separate from each other because excessive drainage of storm water to an oil/water separator could significantly impair its operation and efficiency.

6. Contaminants Contained in the Wastewater Stream

Metallic particles in the wastewater will settle into the sludge at the bottom of the oil/water separator.

Solvents or fuel compounds may also be entrained in the oil/water separators' sludge.

This sludge could require management under the Resource Conservation and Recovery Act (RCRA) as a hazardous waste if it exhibits certain toxicity characteristics.

Therefore, it is important to prohibit the discharge of certain types of potential contaminants into an oil/water separator, and to regularly analyze sludge samples to determine toxicity prior to disposal.

To reduce the accumulation of sludge, floors should be dry-swept before washing.

General improvements in spill/drip control and containment of hazardous materials and oils will also reduce the amount of contamination in oil/water separator discharges.