Do You Really Understand the True Cost of Ownership?

Posted on Mon, Oct 06, 2014 @ 11:44 AM
The price on the proposal is just one indicator of the true cost of ownership when it's time to make a purchasing decision. Before you sign the dotted-line, did you really do the life-cycle costing analysis associated with your Oil Water Separator purchase?

Unsure what LCCA is?

In short, this analysis determines the most cost-effective option among different competing alternatives to purchase, own, operate, maintain and, finally, dispose of Oil Water Separators, when each is equally appropriate to be implemented on technical grounds. Upfront savings are often made up on the backend by higher costs to maintain: higher costs of parts or long leadtimes mean increased outages, inherent designs that require more manpower to maintain due to complexity and power useage and waste are all factors in why your initial savings can end up costing you in the long run. Read more to ensure you've covered all your bases.

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When evaluating various manufacturers’ oil water separator offerings, there are some very important considerations to make in regard to total life-cycle costs of the equipment. Like most industrial wastewater equipment, an oil water separator is not a set-it-and-forget-it system. The initial purchase price of the separator is only the “tip of the iceberg” when it comes to understanding the overall cost during its useful lifespan. Procurement, installation, and maintenance costs are the three main areas that need to be carefully analyzed to help ensure the various manufacturers’ equipment offerings are being fairly compared.

Mercer International provides an informational document which serves as a review of both the initial and long-term costs that should be considered when comparing oil/water separator designs, and explains how investing in a Compliance Master™ oil/water separator saves clients substantial operation and maintenance capital. Like anything else in this world . . .you usually get what you pay for…or less! Mercer takes great pride in being a leader in oil water separation design. Superior design produces superior results. Superior results make the choice for a premium product easily justifiable to the end user once they clearly identify the long-term benefits and cost savings obtained by a more thoughtfully-designed system. The Mercer advantage offers an end user a better solution with higher performance and substantial operational cost savings over the life of the equipment.

Demonstrating this long-term savings, while protecting the end user from environmental citations and fines, is the focus of this document.

whitepaperTrueCoO cover

Click here to read more about the True Cost of Ownership.

Tags: Oil Water Separator, Cost of Ownership

Sample - How To Post

Posted on Tue, May 06, 2014 @ 09:45 AM


Your “how to” blog post should teach the reader how to do something by breaking it down into a series of steps.

Begin your blog post by explaining what problem you are going to solve through your explanation and be sure to include any relevant keywords. Add in a personal story to establish your credibility on this topic. And make sure to end your blog post with a summary of what your reader will gain by following your lead.

Need some inspiration? Check out these "How-To" examples from the HubSpot blog:


Now deliver what you promised in the first section. This is the longest part of the post, so make it easy to read. Use short paragraphs, bullet lists, and bold headings to set different sections apart. 

Some common section headers include:

Step 1: Getting Started

Step 2: Do Your Background Research on…

Step 3: First Steps for…

Step 4: Analyze and Repeat

Step 5: Wrapping Up

You can use bulleted lists, numbered list, or multiple headings. Include as many steps, numbers, or bullets that will allow you to discuss your topic thoroughly.

Here are some pointers to make the best possible body of your blog:
  • Include visuals
  • Include short explanatory phrases in your headers
  • At the end, transition into your conclusion


Now it’s time to say goodbye and wrap up your post. Remind your readers of your key takeaway, reiterate what your readers need to do to get the desired result, and ask a question about how they see the topic to encourage comments and conversation. Don't forget to add a Call-to-Action to turn your blog post into a marketing machine!

Congratulations! What a lovely how-to post you've created. 


Beware Of Vertical Tube Coalescers Inside Oil Water Separators

Posted on Sat, May 05, 2012 @ 04:50 PM

Clogged vertical tube coalescers

Vertical Tube Coalescers (VTC)

This Vertical Tube Coalescer (“VTC”) technology is somewhat of a hybrid between a traditional coalescer and a secondary mesh pack. This design does not utilize “stoke’s law” (or the rise rate of oil) as its primary means to remove oil from the horizontal flow of wastewater. Rather, as the oil droplets drift by the polypropylene diamond-mesh tubes they are attracted to the tubes by adsorption (very much the same principal as the secondary mesh pack).

In theory the VTC coalescer should collect droplets of oil and agglomerate them (by coalescence) into larger droplets. The larger droplets are then to break free from the polypropylene matrix and move their way to the surface along the diamond-shaped coalescer. Solids are to simply fall down and out the vertical tubes.

These tubes are heat welded together and equipped with a handle to insert and remove the media from a tank. The idea is to tightly pack the entire volume of the tank with these bundles, and remove them for cleaning when necessary.

Below: a brief exerpt from a recent keynote presentation where lead design engineer Dave Goding was asked to compare the mainstream coalescing media on the market for use in oil water separators.

 Click me

In Reality

The VTC coalescer’s diamond-mesh pattern that creates a fixed coalescer matrix is too “tight”. The openings for wastewater to flow are between 1/8” to 1/4” – which is way too small for typical industrial wastewater applications. The coalescer gets easily blinded by leaves, plastic(s), and solids that are 1/8” and larger. The fixed, tight matrix does attract oil well. However, at the same time the finer solids drift through the pack, they come into contact with the oil and simply cling to the oil particles—creating an oily sludge deep within the coalescer pack.

In practice, solids do not drift down and out of the pack’s tubes. They simply get caught in the coalescer as solids get caught in any filter. Once plugged up, the packs are almost impossible to clean completely. These packs need replacement more often than most other types of coalescers, and become an ongoing and expensive replacement part.

Fouled vertical tube coalescersclogged oil water separator

This is a disposable model, as there is no way to clean fully into the center of each bundle. Higher flow rates can have upwards of 20 of these tube packs that need to be pulled out and cleaned/replaced on a monthly basis.

Tags: Oil Water Separator, plugging solids, vertical tube coalescers

Why Some Oil/Water Separators Need Secondary Coalescers

Posted on Tue, May 01, 2012 @ 12:35 PM

The Secondary Coalescer is a Warning Signal: 

This treatment option is most often seen in the below ground cylindrical “simple tank” oil/water separator world. These packs are largely used in the storm water, petroleum marketing, and transportation industries. Below ground tank systems do have corrugated plastic plate coalescers, then they are followed up by mesh adsorption packs consisting of polypropylene mono filament fibers. In theory, the coalescer in the oil/water separator is the primary separation device and these mesh packs are supposed to allow the water to flow through while any of the small oil droplets coalesce into larger droplets and rise to the top. In most cases the plate coalescers are designed at too shallow an angle to get efficient oil separation, so the manufacturers add adsorption packs to “improve” removal efficiency and meet effluent standards.

Secondary CoalescerPolishing Coalescer

View Mercer lead designer Dave Goding discuss this type of crutch practice by some oil/water separator manufacturers:

Relying on polishing mesh packs to “make up for” the shortcomings of an irregularly shaped plastic coalescer is not sound treatment. The design philosophy goes much like this: “Since we cannot meet 60 micron removal requirements with our oil/water separator at design at maximum flows, we will simply insert this high surface area mesh in the back and cover ourselves.”

Here is an important question to consider: If this were an effective design method to treat oily wastewater, why wouldn’t every oil water separator manufacturer simply fill the entire tank with this mesh and leave out the primary coalescer?

This is the worst fouling treatment in the marketplace. Originally created for treatment in mist eliminators, and a decent alternative for flock matter, this is by no means an effective alternative. Once these clog very quickly, the flow actually builds pressure back and makes these cartridges sag and rip very easily. They are not industrial duty and therefore present constant replacement costs over the life of the unit.

A Crutch for an Under Performing Coalescer--When insufficient coalescer design was recognized, especially in the below ground cylindrical market, manufacturers had to come up with a way to promise stated removal values. These “polishing” packs readily plug at their entrance points, and actually serve as a flow obstruction within the treatment.

Clogged oil/water separator meshFouled mesh pack

Tags: below ground oil/water separators, mesh packs, polishing coalescers, secondary coalescers

Oil/Water Separator Design:Beware of the Honeycomb

Posted on Sun, Apr 15, 2012 @ 07:30 PM

You get what you pay for, and most times much less. Below is an excerpt from a virtual trade show where lead design engineer Dave Goding discusses the fouling problems that are guaranteed to occur when using honeycomb/egg-carton plastic coalescer designs:



Once inexpensive corrugated plastic media took over as the “standard” in oil/water separator design, it became a race by manufactures to produce separators with low price as their selling feature. Now the oil/water separator industry was selling their equipment on price instead of features & benefits. Once price became the main selling function, many long-standing internal components and sound design standards began to be cheapened or eliminated. By designing down the coalescer, the inlet and outlet baffles, solids handling capacities, etc., manufactures began sacrificing functionality and efficiency. This drastically reduced the end user’s ability to stay in compliance.

Manufactures tightly pack these plastic bundles in separator units, selling promises of higher surface area and (theoretically) better oil removal capabilities.

corrugated coalescers

The “nooks and crannies” within these coalescers are the problem with this design. The various nooks, crannies, ridges and flat spots cause solids to lodge in and on the plates, building up and fouling the packs prematurely. Further, there is no clear path for solids particles to make their way out of the coalescer. The settling solids have nowhere to go and “dead end” within the coalescer causing even more rapid fouling.

clogged oil/water separator

To further complicate the problem with this design, these style coalescers are nearly impossible to clean. Because of their design, high-pressure washers can only penetrate from 6”-12” into the packs before the velocity is dissipated.

The cleaning becomes very labor intensive. Many times the packs cannot be cleaned all the way through, therefore the end user is forced to throw away these packs after a few cleanings and replace them with new ones. In certain more high-solids applications or applications with “sticky” oils and solids, this could entail a full coalescer replacement every time maintenance is performed.

plugged oil/water separator

Tags: Oil Water Separator, plastic corrugated coalescers, oil/water separators

The Emergence of the CPI Oil/Water Separator

Posted on Tue, Apr 10, 2012 @ 07:38 AM

Why Oil/Water Separator Manufactures Went The Way Of Plastic Corrugated Coalescing Media Decades Ago

Once those treating oily wastewater realized they no longer needed to take on the large treatment footprint of installing API oil/water separation pits or tanks, they were greeted by several new companies entering the oil/water separation marketplace. They also were faced with the difficulty of weighing one manufacturer's removal promises against another.

In response to this, the American Petroleum Institute (API) released a new set of sizing criteria in Feb of 1990 that dealt with the emergence of "plate pack style" or "Coalescing" oil water separators. This document, API Publication 421, went about laying out several calculations that would assist end users in determining how much surface area was needed to achieve an acceptable removal rate at a given flow. 

At that time, the growing fad within the Oil/Water separator industry was to make the coalescing plates corrugated to give the bundles more structural integrity (much in the way a corrugated cardboard box is able to maintain its shape). Originally this allowed a once flat 1/4" piece of steel to go to an 1/8" thickness or less and save on material costs. The manufacturing process went through an even more drastic cost reduction when these sinusoidal shaped plates began to be fabricated out of different types of plastic. The reason for the corrugation was basically cost reductions, as manufactures all went to battle against each other claiming higher removal rates at bargain pricing. 


Steel CPI oil/water separatorDownflow CPI oil water separatorplastic CPI oily water separators 

Corrugated Plate Interceptorcpi oil and water separator


The standard practice became to position these progressively slanted/tilted S shaped plates in an upflow or downflow position, so gravity could help in one of the two important aspects of the treatment process--downflow for solids and upflow for oil. The problem with the sinusoidal design, or the CPI (corrugated plate interceptor), was that solids would all concentrate in the  trough areas where they would quickly accumulate. The trade off for producing the required surface areas to keep up with higher removal mandates was a design that fouled very quickly.  

fouled oil/water separators 

The unequal distribution of solids loading combined with oils or solids having to work against a given flow, gave way to a new set of problems that would become commonplace in oil/water separation. The frustration with the new coalescing variety of oil/water separators back then, is still a problem today.  Oil/water separators that present themselves as low cost options have serious design flaws that foul prematurely and compromise efficiency. 


See Why Mercer Uses A Cross Flow Designed Oil/Water Separator With A Flat Plate 

In January of this year lead process designer Dave Goding had the opportunity to review several of the mainstream coalescing technologies during a keynote at Globalspec's water quality and reclamation virtual conference. Below is an excerpt from his portion that covered CPI oil/water separators.

Click me


Tags: Oil Water Separator, API oil/water separators, plastic corrugated coalescers, oil/water separators, cpi oil water separators

Cost: The root cause of oil/water separator fouling

Posted on Fri, Apr 06, 2012 @ 09:00 AM

On Jan 25th, 2012 Mercer International's lead process engineer David Goding was asked to give a comparative review of oil/water separator coalescing media for Globalspec's Water Quality and Water Reclamation virtual conference. Below is an excerpt covering the emergence of the parallel plate pack in traditional API oil/water separators.

 Click me


Somewhere in the mid twentieth century the "plate pack" was designed and constituted what was the first coalescer to be introduced into the oil/water separation process.  Essentially a series of horizontal plates were stacked up one on top of another and placed inside API oil/water separators. This allowed capture of smaller micron sized oil droplets from the separator in the same sized tank (usually a concrete pit). The surface area of these thick ¼” steel plates would catch smaller oil droplets at the top of each plate and allow them to collide or coalesce into bigger droplets. So instead of only being able to remove oil droplets of 150 micron size, the oil and water separator was now able to hit the 100 micron removal range.


Parallel Plate Oil/Water Separator

Industry began to need more efficiency as government regulations ratcheted down the allowable oil concentrations in effluent (See Federal Water Pollution Control Act Amendments of 1972). Seeing how these parallel plate pack inserts were achieving higher removal capabilities, the design no longer required a large tank to achieve the desired removal.  The first packs started with very wide plate gaps, and companies began to tighten up these gaps in the attempt to obtain (claim) higher removal capabilities.


The Problems:


The first problem with this design was that these large parallel packs fouled very quickly. The presence of solids, and the accumulation of them on these parallel plates, led to very short process runs before shut down and cleaning was necessary. 


The second problem was in the material costs required to make such long parallel plates out of steel.  The higher the flow rate, the longer these plates needed to be to theoretically guarantee the desired removal rate. The costs began to climb signifigantly as manufactures began tightening the plate gaps in these horizontal parallel packs. The benefits of the pack were being outweighed by the high costs of construction and the growing maintenance pains of having to clean the oil/water separator very frequently. These problem areas eventually led to manufactures introducing corrugations into their designs to save on material costs, while still maintaining the structural integrity of the packs. This in turn paved the way for the plastic corrugated media that would go on to dominate the oil/water separator market for the next 25 years.


What Mercer has learned:


Maybe "plague" is the better word choice instead of "dominate" for what the end user community has been forced to endure since the first plate pack was introduced. The manufacturing community truly only addressed one of the two problems in the original design, and that was the cost. The introduction of corrugations into the design of coalescers did nothing to go to the root cause of industry's frustration, which was the fouling and clogging created by solids mixing with oils creating sludge.


The Mercer design took root after years of polling end users about what frustrates them most in the oily wastewater treatment process. Overwhelmingly, the problem has been with fouling coalescers that eat up maintenance dollars and compromise allowable effluent levels. 


How Mercer manufactures the highest performance oil/water separator 

comparing coalescers





Tags: API oil/water separators, flat plate coalescers, plastic corrugated coalescers, oil/water separators

API Oil/Water Separators: Simple But Costly

Posted on Mon, Apr 02, 2012 @ 09:05 PM

The Origins

Simple gravity separation is where the marketplace began to deal with the removal of oil from water as well as spill containment.  Many older large holding tanks are commonly referred to as API oil/water separators, referring to the American Petroleum Institute who created the design parameters for certain flow rates. The American Petroleum Institute provides design criteria for oil/water separators. A design method is provided in the API Manual on Disposal of Refinery Wastes, Chapters 5 and 6- Oil-Water Separator Process Design and Construction Details (API publication 1630, 1979).  


API oil/water separators

The API oil/water separator is a simple gravity separation device designed by using Stokes Law to define the rise velocity of oil droplets based on their density and size. The design of the separator is based on the specific gravity difference between the oil and the wastewater because that difference is usually smaller than the specific gravity difference between the suspended solids and water. Based on that design criterion, most of the suspended solids will settle to the bottom of the separator as a sediment layer, the oil will rise to top of the separator, and the wastewater will be the middle layer between the oil on top and the solids on the bottom.

Advantages of the API separator are simplicity of design, low day-to-day maintenance, and resistance to plugging with solids. 


(Below is an excerpt from a presentation Mercer gave at an online Wastewater conference)

Click me



API oil/water separators are designed to remove oil droplets down to 150 micron, which is not nearly enough removal necessary to stay compliant today.  Most API oil/water separators are not going to do any better than 50 parts per million as opposed to most state & federal regulations that today require below 20 ppm.

Most industries have abandoned building these large gravity settling vessels because they are simply too costly to justify. Most are built of concrete and with the high cost of labor and the need to reinforce these tanks with steel, new construction costs rise quickly. Plus API units have an excessively large footprint and are far too much of a real estate burden to consider this as a viable option.

Those who have API oil/water separators acknowledge they are easy to operate and maintain on a day-to-day basis, but when it is time to clean out the tank, the cost to pump out the sludge and clean this large space is just a nightmare. Some units have a chain and scrapper mechanism. This helps move the solids to one side to be pumped out, but the automation piece for these are usually as much as the construction of the pit itself—and require significant maintenance as well.

 The Mercer Advantage



Tags: Oil Water Separator, API oil/water separators

The Important Oil Water Separator Formula

Posted on Thu, Jul 21, 2011 @ 10:24 PM
Of course there are several math equations that are important to utilize when it comes to evaluating the appropriate size or style of oil water separator a certain application calls for. At Mercer we protect and hide the way we calculate and manipulate our Laws and Theories, much like the folks at Coca Cola keep their secret formula under lock and key. However there is one equation we have front and center in any conversation we have about separator design, and it's much less technical than the calculation of Reynolds numbers, equivalent diameter, oil droplet capture capabilities, or minimum rise rates. Far away from the neatly organized engineering and technical desks (where theoretical calculations about performance and functionality are being tested via sharp pencils and calculators ),a Mercer International derived formula is making the complex simple to understand in a "boots on the ground" practical manner.

Oil + Solids + Time = SLUDGE 

It would be so much easier if we could simply calculate a flow rate, run some viscosity and specific gravity numbers on the types of oils present in a certain wastewater, and easily come up with a suitable product.  But the fact remains that real life applications are not at all like the perfect scenarios laid out on the 

The most important consideration is the affect the solids present will have on the functionality of the oil water separator. Calculations made that kick out ideal surface area numbers and rise rates are only the first half of the evaluation process. The amount of solids present is the most important consideration; and even more important is the way a potential oil/water separator design is positioned to handle this solids loading.  Even the smallest amounts of solids can present enormous maintenance problems, reduced efficiencies, and lead to drastically more expensive lifecycle costs.

Mercer International has dubbed its Compliance Master™ Oil Water Separators "High Performance" because of the coalescing separation design improvements that were made to process out the solids (as opposed to simply push them through the pack). The outright removal of the solids is the most important way to ensure the resulting effluent is not just compliant...but compliant for a prolonged period of time.

Just because your less expensive purchase based on the sharpened pencil looks like this:

Plastic Coalescer

Doesn't mean you don't have to consider what you are going to do in 10 days when it looks like this:

clogged oil water separator



Tags: Oil Water Separator, High Performance, Sludge, o+w+s=sludge, maintenance, plugging solids