Oily Water Separation 4

[chiefeng]

The engineers on our vessels are having trouble with adequately maintaining the 15ppm via the coalescer type OWS, although it is only 3 years old. I have sailed for 30 years and had the same problems. Has anyone had any experience with ULTRAFILTRATION onboard ships? If so, any contacts please?

 

[romke]

Ultrafiltration will not necessarily solve your problem. To separate water and oil there a few things to bear in mind. First choose the correct separating equipment - which means that you have to tailor the equipment to the specific density of the oil/water mixture as closely as possible - and that density is temperature related. Therefore also the temperature of the mixture is important: a higher temperature will generally assist in separation since the specific densities of oil and water will be somewhat wider apart at elevated temperatures.

A second point of consideration is the types of additives used in the oil. If the oil uses lots of ashcontaining dispersants (as usually is the case for heavy-duty engine oils for trucks and other wheeled equipment) it is very difficult to separate water and oil. Therefore in engine oils for vessels usually another type of ashless dispersant is used that is better suited for separation of water and oil on the basis of centrifugal forces.

Ultrafiltration is something quite different. If you have water in the oil (and therefore a certain amount of emulsion) ultrafiltration will ususally not help because the fine pores in the filter will readily be clogged by the emulsion.

In hydraulics, where ultrafiltration is used quite often, usually non-detergent types of hydraulic oil are employed that readily shed water. Just traces of engine oil will usually destroy the water shedding properties, and so will small amount of Ca-based additives.

 

[unger]

I own a company which repairs oil water separators and sewage plants for marine vessels.

Your biggest problem is not the oil in the water its the bacteria growing there.

Do me a favor and test the water using this simple test.

Take a sample from the bilge (prefer the middle water level) and put it in a 1/2 gallon glass container, fill 3.4 way.
Now take 1/4 cup liquid bleach and add to the container and stir. Allow to set for 12 hours. you will notice the water has cleared and the sediment on the bottom is white. The sediment is not oil, but is bacteria which thrives in oily bilges, this bacteria clings to the oil molecule and eats it. To get the bilge water so that the bilge separator can operate properly will require you to remove this bacteria.

My email - marineresources@msn.com
Web Site -

http://www.aukllc.com

 

[MP21]

Chief,
Another problem may be your OCM. Most OCM's use a light scattering process to measure Oil Content, any discoloration of the water can be mistaken for oil. There is a product that measures the oil content with ultrasound and turbidity. It's the FOCAS 1500 see the web below.

http://www.hermont.com/Pollution.htm?CD=23

I have only heard good things about these meters, they have a high tolerance to vibration as well.

 

[Lis]

Hi there Chief,

There's been a lot of discussion on this topic in the last year under an older thread that I started when I was researching new separation methods (under 'Oily Water Separation') where a lot of people came forward with useful info and contact details.

Ultrafiltration seems to be a very successful method of separating, but there are other methods. I have also noticed a lot of problems with coalescers on the ships I've been on. The reason they dont work too well now is actually down to emulsification of the oil in the bilge water, making it impossible to fully separate by gravity (coalescer principle)...so this is the area you probably need to tackle. There's a few ways of cracking emulsions and you need to find the best way for your ship and circumstances.

If you would like a copy of the findings of the research then let me know and I can send you that and a whole HEAP of info that I gathered during the project.

In the mean time, are you dosing the bilge water with anything prior to separation? We found chlorine particularly effective (tackling the bacteria problem already mentioned), and this was actually recommended by the representative from the company making the OCMs we use on our ships...might be worth a go - we added it through a dosing pump straight into the pipe, before the monitor sampling point, and also added buckets of the stuff to the filters before the sep occasionally when we were having problems: just open the filters and chuck a load in. Alternatively, I suggest looking up companies that produce chemicals to crack emulsions and try adding that to your bilge water in the tanks before it goes through the sep.

Let me know if you would like further info.

Regards,

Lisa.

 

[Lis]

By the way...the other thread I mentioned is about half way down page 2 in this section.

 

[netherhay]

The company I work for, Cobham Fluid Systems Ltd., manufacture ceramic membrane bilge water separators certified <5ppm for marine use (presently undergoing sea trials with UK RN and specified for new build Type 45 destroyer).

http://www.cobhamfluidsystems.com

Ref. Lis' posting:

Trouble with chemical addition to prevent/kill microbiological growth is that you then have the chemical residue that is discharged overboard. The addition of chlorine normally requires subsequent sulphonation to neutralise the chlorine, itself a very effective poison (ref. drinking water treatment plants).

 

[oxilume]

Chief,

I have developed a new system for treating oily bilge water and ballast water.

The University of New Orleans, and Virgina Tech may be verifying the technology within the next three months. You can get a brief description of the technology on my website:

http://www.oxilume.com

Go to &quot;Carbon Arc UV Light&quot; page.

We will begin a demo at a large automobile manufacture for treating metal working fluid. Likewise, the system will be tested at the World's largest MTBE (gasoline additive) plant.

I am a former Chief Engineer and MPA and I am very familar with your problem.

Todd
toddforet@usa.net