Oil Water Separators 101: Part Two
An oil water separator (OWS) is a flow thru device for removing smaller amounts of oil from larger amounts of water in a moving stream of water.
Why and When to use an OWS?
Usually when you have relatively small amounts of free and un-emulsified oil in your waste-water that is not available to be skimmed off the surface.
Using an Oil Water Separator (OWS) as part of a process for contained water.
Imagine a trench drain in a heavy equipment repair shop where the shop floor is slightly sloped so that any water and/or Oil that is dripped,leaked,dropped or even drained onto the floor runs into this trench drain---and runs into a collection/storage basin where everything ends up.
Now what to do with it? Simple ...have Safety Kleen come get it and haul it off for BIG BUCKS or gently pump this stuff up to a simple small oil water separator sitting on the floor or to the side of the building. The OWS if properly sized will remove all the free UN-emulsified oils and then you can usually put the clean water to drain.
Oily bilge water on a ship--(and there is often LOTS of it)---has to be run thru an approved oily water separator (OWS) before it can be discharged overboard. Usually this OWS has to have an oil content monitor (OCM) on it to verify/control that the oil content of the overboard discharge is below 15 PPM. These specialty marine oily water separators are usually self contained fully operational systems complete with pump and controls and the OCM. These ships can and do often generate thousands of gallons of oily bilge water. It's gotta' go somewhere ? Best to keep it legal with an OWS.
NEXT TIME: #3 OilyNews Blog:
When to use an oil skimmer in conjunction with an oil water separator
Oil Water Separators 101: Back to The Basics
An oil water separator (OWS) is a flow thru device for removing smaller amounts of oil from larger amounts of water in a moving stream of water.
When to use an OWS?
Usually when you have relatively small amounts of free and un-emulsified oil in your waste-water that is not available to be skimmed.
From rain water or surface water that is draining off of an area that has possible existing oil contamination, such as large parking lots, refinery facilities, steel mills or other areas where historically there has already been or has great possibility of future accidental oil getting on the ground.
Intentional oil storage areas like diked in secondary containment area around oil fuel storage tanks (tank farm?) or where equipment is located with oil or fuel leak potential.
The key reason to use the OWS in these situations is because you don't have any or not enough oily water storage capability or containment so you have to remove the oil from the water as it's being moved. The OWS acts as an insurance policy to prevent discharging oil into the environment.
This portable cart mounted system is perfect for anyone with several tanks that need occasional or scheduled maintenance and you want cleaner fuel going to your engines. Wheel it up to your tanks, drop the suction hose down any 2" pipe and use a return hose, turn it on and let it run. It will recirculate / turn your tank over, cleaning the fuel on a gradual dialysis basis, removing dirt and water. After an hour or a day--- move it to the next tank.....same routine. Protects your filters and cleans your fuel and has no moving parts or replacement filter media.
These diesel fuel purifier systems come in four sizes, 20-50 gpm in the wheeled portable version and a 7 gpm system bulkhead or hard mount, complete system. It's risk free because you are not going to bypass your primary filters you're going to protect them for longer life and cleaner fuel. And speaking of filters......
Type ll MSD Black and Gray Water Treatment System
SkimOil has just added a new "solutions oriented" device for treating both black (sewage) as well as gray water prior to discharge. According to SkimOil's spokesman Roscoe McWilliams, "we've been dancing around the marine gray water issue for several years now " starting with the MarineVAP onboard evaporator systems and the Gray Water Filter. Problem is as always, "the greater volumes of gray water" have made evaporation almost a non player. There is simply too much gray water generated on-board most workboats to economically evaporate it, although the axiom still holds true" No Discharge is a good discharge" It just simply costs too much to evaporate it.
SkimOil now has the MSD Tank, type ll Marine Sanitation Devices that can handle either black or gray water or even a combo of the two. Approved for use by all regulating agencies, The MSD Tank is designed specifically for dealing with the "mixed stream" of gray and black water. Efficient compact and/or modular design, matched with high quality components and DEAD tight quality control , the MSD Tank systems can meet all discharge quality standards across the globe. The MSD Tank is the state of the art for handling both sewage and gray water on-board, treating it for legal overboard discharge. Finally The MSD Tank provides economical, safe and approved gray water discharge.
See the video made at the WorkBoat Show https://youtu.be/s0wz_IRSglY
See the new MSD Tank systems at: http://www.skimoil.com/the-msdtank.html
Skimoil has just introduced after field trials, their latest Floating Weir Skimmer (FWS) Coal Ash Pond* Surface Decanter designed for high flow rate decanting of surface water from coal ash ponds, without disturbing the underlying well settled ash. The surface water decanting is usually the first step in coal ash pond management and closure.
Under typical operations this decanted water is monitored for TSS and pH and discharged to public waterways until the water level reaches the interstitial level of 3' above the ash, at which point the dewatering process begins and remaining water has to be sent to a waste-water treatment plant for treatment prior to release, according to the new rules from the Environmental Protection Agency.
After all de-watering is done the ash can then be excavated, transported or isolated in lined disposal ponds or in some cases abandoned/closed underground mines, according to the facility owners permitting.
*Coal ash is the toxic-laden waste by product left behind after coal is burned for energy. Generally, the ash is collected and then transported to large coal sludge “ponds.
We've been writing about different ways to make your oil water separation process easier. Here is #3.
Last time we talked about how, if you use a high shear pump to pump to an oil water separator all bets are off.
Won't work and you'll be creating A MECHANICAL EMULSION THAT WILL NEVER SEPARATE IN YOUR LIFETIME!
Wait a minute, yes there is a way to work around this problem at least partially. A REAL WORKAROUND!
If you can operate your pump on the downstream side of the oil water separator (OWS) you will be pulling or sucking the water thru the separator and not churning it up prior to entering the separation chambers.
Our BRUTE marine oil water separators are set up this way so we can use our high efficiency centrifugal pump on these separators, and not create a separation problem. The cost of doing that is that your pump suction head is reduced, but if you set up a series of back-flow preveneter valves the cost is not too great and considering that you can use standard pumps if your oil water separator is pressurized, all the better and all the easier to do.
Another workaround for this problem is to use a peristaltic pump or what is often called a hose pump. It works the same way your stomach moves food thru your digestive system. “The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wavelike movements that push the contents of the canal forward." You've seen this in action before but maybe did not recognize it. If you've ever stepped on a garden hose that has water sitting in it your body weight on the hose displaces or pushes some of the water out. These “hose pump” use a pair of motor driven cams to squeeze water out of the hose which is held in the pump housing. These are often used to pump very thick stuff like mud, drilling muds, and even concrete. As such the hose is a consumeable since it will eventually wear out due to the constant squeezing and wear inside as material is moved thru it. It's said that a “hose pump” can suck a bowling ball out of the basement -thru a 1” hose. That really sucks...................hmmmmmmm
It's been just a week (last night) since we packed out our booth and equipment from the 2015 Int'l WorkBoat show. What chaos that is, everybody from 1100 booths trying to move out at the same time, while the Freeman crews are rolling up the acres of carpeting and trying to clear the aisles. After the WorkBoat show -it takes about an hour for the transformation from a thing of beauty with tens of millions of dollars worth of high tech equipment….to what looks like a war zone with trash all over the place. The show people have found out it's easier to just let stuff lie where it's dropped until everyone is gone and then the cleanup begins. We waited 5 hours for our crates to show up at our booth, so we had a birds eye view of the whole process. Once the crates were delivered back to our booth---it only took us 15 minutes to crate up half a ton of bilge water evaporators and bilge filter equipment.
During the show we learned once again from the attendees, the parallel to and about an attitude we detected among the boat operators, regarding getting rid of trash and waste water from on-board their vessels or at their shore facilities. Almost everyone we talked to was afraid to or at least VERY hesitant to treat or separate their bilge water and slops. We talked with folks hauling off 40,000 gallons of water a month at over $1 a gallon, rather than treat it for discharge back to the rivers or harbors. And these vessels were equipped with modern oil water separators. These decision to NOT discharge were made at the executive level and are probably based at least partially on the outdated attitude that the equipment is not reliable or cannot be trusted OR that their people couldn't operate it safely enough.
There was a time, even just a few years back when oil water separators were not reliable and or were too finicky to trust. Those days are long gone, simply because the controls and electronics now are drop dead reliable. Case in point: our BRUTE marine oily water separators are equipped with new state of the art oil content monitors, reliable enough to be USCG/ABS/BV approved to meet the latest very stringent IMO/MEPC 107 (49) requirements. Pollution control equipment now can be PLC and even computer driven and controlled and the electronics that accomplish this are at least as advanced as the Iphone you have in your pocket.
Think about how that technology has changed your life. Even our Bilge Water Filters can be so equipped that they can send info to your phone if there are upset conditions with the equipment. Safe overboard discharges can now be assured.
That's real progress that the industry can't afford to ignore. Controls, like our phones have become so advanced and sophisticated that they are becoming indispensable to our every day life and operations. Change is upon us, and we as an industry have to change our old ideas that controls are not trustworthy. Just look what your smart phone can do.
Even your kids can use it more ...than we can ever learn to.
Another tip for making your oil water separation process easier. A few weeks ago we wrote about the first rule of thumb, get the oil out or off the water as soon as possible.
The following post will address emulsions and how they can effect and even fool an oil water separator.
If you eventually want to separate oil from water, WATCH OUT FOR HOW YOU PUMP IT. Example: Often engineering firms and consultants specify use of an oil water separator for treating oily water coming from elevator sumps. Makes sense right ? Well it almost makes sense...kinda'
An oil water separator (OWS) is a flow thru device (USUALLY GRAVITY FLOW) designed for removing free unemulsified oils from a moving stream of water. The OWS is designed based on the differential in the specific gravity between oil and water (Stokes law) to do it's separation. Most oils are lighter than water so they float on the surface of the water.
Most elevator sumps contain and use a submersible sump pump for pumping out any water that can seep or leak in. These are usually centrifugal off the shelf very reliable pumps but the problem can be that they are high shear type pumps that act like a mixmaster and chop the oil particles into micro oil particles which are so small they don't have enough buoyancy to rise thru the water column. Problem is----now you've created a mechanical emulsion that an oil water separator is designed to handle. An emulsion can fool an oil water separator.......avoid whenever possible.
ALL BETS ARE OFF FOR RUNNING IT THROUGH AN OIL WATER SEPARATOR if the oily water has been thru a centrifugal or other high shear pump. There are instances where we can put pumped oily water thru an OWS but we have to take a hard look at all the parameters of this type application and ALWAYS, it's going to take an much bigger separator that will provide for lots more dwell or residence time in the OWS to effect separation. It doesn't matter if the oily water was pumped yesterday or last week or last month, now you've created an emulsion that's a game changer for easy separation. Pumping the oily water gently, as with a positive displacement (PD) pump may let you work with an oversized OWS but it's a tricky formula to work out.
We use a general rule of thumb of 20% that can work some of the time depending on all conditions. That is if the stuff has been gently pumped you can feed it to an OWS at 20% of the OWS's gravity flow rate, but this is not a hard and fast or constant rule. There are some work arounds for the pumping of oily water, but whenever possible DON'T PUMP IT if you want to separate it later. Why deal with a problem you can avoid to begin, with thru good design.
Separating oil from water is easier when it’s done earlier. As simple as that sounds—operationally it’s not always so easy or convenient as it should be to minimize the problems now that certainly will show up a bit later on. In the oil skimmer and oil water separator business we run into all types of recovery problems that can be avoided to begin with if the process is just started sooner than later.
Rule #1 is get the oil off of or out of the water soonest, before it has a chance to age or deteriorate or start collecting debris. The aged oils that we see, especially in outdoor areas often has allowed the lighter fractions to gas off, leaving the heavier oils that don’t flow or act as well on the water surface as they would have when they were first introduced to the water, wherever they are. Sunlight only exacerbates the problem by even further by accelerating this evaporation even further.
Leaving oil on the water surface only adds to the separation problem because that is of course where all the junk or debris collects, giving you oily stuff floating around on the surface, which can then give you a gunky material handling problem as well as an oil removal problem. And it can get worse. Oil is usually highly attracted to metals and plastic and will coat them whenever possible, giving you another surface you need to remove the oil from. See where this is going?
In the days before recorded history (prior to accurate oil content monitors) some in the commercial marine industry had to use very temperamental and finicky oil water separators. These separators were mostly used on the blue water ocean going vessels. Everyone who used a separator hated it and did not trust it, but that was the state of the art. It’s all there was.
But during all this, we tried and tried, but learned that there was not enough heat to recover unless we could get a lot of dwell or residence time in the exhaust gas stream without a total exhaust system redesign, and of course none of the boats and ships were willing or able to make changes like that and add all the heat exchangers that would be necessary to capture that heat. It would require large systems that take up a lot of room.
In 2000, SkimOil™ introduced the electric powered BilgeVAP bilge water evaporator to the inland waterways operators, an electric powered system that works GREAT for evaporating oily bilge water. The BilgeVAP was and is simple and deadly effective — with no emissions and only one moving part. Problem is — it takes a lot of power to evaporate water! 2.6 Kw to evaporate 1 gallon of water. Few boats have that much surplus power. If you’ve got the power to spare, it—s a valid alternative for eliminating oily bilge water or slops at 4-12 gph. Today our BRUTE oil water separators are among the toughest most reliable USCG approved separators made anywhere — but even they cannot deal with gray water or emulsions — like from washing down an engine room with soap.
At SkimOil we specialize in waste minimization equipment and systems for the commercial marine industry. This is what we do all the time, so we can bring highly specialized knowledge and experience to your project—giving you the right technology so you can get it right—the first time. We love oil! Call SkimOil at (314) 579-9755 or e-mail: email@example.com
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