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Cleaning the grease trap has to be the most disgusting job
in the restaurant business. The noxious stench “will
gag a maggot,” as Robert Rubin puts it, departing momentarily
from the clinical terminology of a professor emeritus and
wastewater expert from North Carolina State University, who
is now a senior environmental specialist with McKim and Creed
in Wilmington, NC.
Cleaning the trap or outdoor grease interceptor is not only
a revolting job, it’s labor-intensive, offering perhaps
twice the excuse not to do it. As Oklahoma Department of Environmental
Quality (DEQ) solutions specialist Dianne Wilkins points out,
in a hectic kitchen “employees always take shortcuts
… they have to keep moving quickly. It’s easy for
them to wash everything down the wrong drain and disposal.”
As a result, grease is sent to the wrong place, beyond the
reach of any system for collecting fats, oils, and grease
(FOG).
Given these realities, it’s simply too easy to let the
trap fester. Wilkins notes, “We have seen grease traps
that were never cleaned.” Such basic ignorance regarding
grease trap operation is not at all unusual. Although the
manual may dictate, “Clean trap daily,” notes Brian
T. Rabe, CPSS, of Cascade Earth Sciences in Albany, OR, “nobody
every really does.” The result, increasingly, is a big
problem.
As reported previously (Onsite Water Treatment, Sept. 2005),
improperly discharged restaurant effluent tends to spew by
the ton into the nation’s sewer lines, there to congeal
and coagulate. The EPA estimates that perhaps 75% of US sewer
systems are impaired by accumulated FOG. Cumulatively, sewer
backups, spills, and overflows over recent years number in
the untold thousands, with high-strength waste from food service
establishments (FSEs) being a prime culprit. In response,
for several years the EPA has been pressuring community wastewater
system operators to clean up and clamp down on FOG emitters
by applying various sanctions.
Nevertheless, the current regulatory and administrative situation
remains rather chaotic. As Rubin explains, most states and
municipalities “have now recognized the problem and have
responded with various measures.” For example, there’s
something of a boom in surcharge fees for high-strength sewage
discharge, amounting to hundreds of dollars monthly per offending
ratepayer. Add to this assorted controls, such as more frequent
inspections and more mandatory pumping.
Still, Rubin adds, “I would go on to say that very few
places have truly effective enforcement,” due to a host
of technical, regulatory, and administrative hurdles, and
unresolved procedural questions. In sum, he says, “You’ve
got a regulatory mess … an ordinance mess … an enforcement
mess. And you’ve got a lot of people claiming, ‘I
can handle this stuff’ with some magic potion. And you’ve
got a couple of people out there who really have effective
FOG treatment programs and a management system.”
Moreover, as several pre-treatment experts explain, anti-FOG
prescriptive measures for a given site are not really simple
or obvious to define. On the contrary, specific conditions
vary considerably at different sites, dictating custom-designed
solutions. Even when appropriate intervention strategies can
be determined, there’s the problem of ensuring they’re
carried out (and, indeed, modified thereafter as conditions
warrant) and cost-effectively enforced. On the latter score,
before technologies can be applied, there probably need to
be ordinances and standards in place, Rubin suggests.
Naturally, these should be based on research—which somebody
has to oversee and pay for. Several treatment experts point
out that the installation of any measure to automate the maintenance
process and/or compensate for human failings should be, in
theory, a plus. In reality, though, if vendor follow-through
is weak, or if the kitchen crew isn’t on the ball, a
restaurant will likely see little real improvement.
Finally, once a FOG strategy is in place, a community still
faces the question of where to dispose of the putrescent tonnage—i.e.,
should pumpers be paid to haul it to a landfill, treatment
plant, or even an incinerator? In many jurisdictions even
this issue is undecided, notes Rubin. He adds that, in sum,
“Its a big, complex can of worms.... And you show me
any restaurant, any food-service establishment, any high-strength
waste-generating facility, that voluntarily wants to get into
a program to manage this stuff.”
Customizing Remedies
That said, positive solutions can be applied cost-effectively,
with a reasonable assurance of some success, according to
a consensus of pre-treatment specialists and vendors offering
input for this report. The following discussion explores interior
grease traps in particular; outdoor grease interceptors are
a different animal, deserving of their own management strategy.
Nevertheless, many tens of thousands of FSEs rely on grease
traps that could use improvement in maintenance.
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| The Big Dipper. |
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| Grease is pumped to a tank for
biological breakdown. |
Traps are predominantly likely to be “conventional,
small, manually emptied” ones, suggests Bill Batten,
who does marketing for an automatic trap-cleaning system called
the Big Dipper, made by Thermaco. He estimates that about
40,000 traps and interceptors are sold annually in the US,
of which the market for automated, aerated or other “non-standard”
systems is remarkably small—“probably less than
2,000 units yearly.” The trap maintenance challenge has
given rise to a dozen or more technologies and methods: Assorted
fixed or movable filters; mechanized removal devices (like
the Big Dipper), and various means of accelerating natural
grease decomposition in place, using bacteria and/or aeration.
Selection of the correct additive and using it properly can
yield potentially spectacular improvement in reducing both
BOD (“biological oxygen demand,” i.e. food waste)
and FOG.
Encouraging Data
This conclusion has been reported in several scientific studies
and conference proceedings over the years, most of which are
available at the National Small Flows Clearinghouse (NSFC).
(Search the bibliographic database for “restaurants.”)
Two examples of useful white papers include “Aeration
Pretreatment for Commercial Restaurants” (Hoage and Johnson
1997), which reported “dramatic removal of heavy FOG
levels to easily managed concentrations” by using a microbubble
vacuum aerator; and a conference, held at Auburn University
in 1995, which examined “Restaurant Pretreatment Choices:
Automatic Grease/Oils Removal Systems, Application, Operation,
and Sizing Considerations.” A few other NSFC studies
indicate that restaurants having onsite septic units—if
appropriate FOG-control measures are applied, such as aerators—can
add years of life for the drainage field. Similar improvements
are realizable for sewer-connected eateries. More recently,
major FOG research has been underway in Orange County, CA,
and Cary, NC; respective findings should yield valuable guidance,
and publication is expected beginning next year.
Apart from academic studies, commercial lab testing of restaurant
FOG and BOD constituents—and development of appropriate
control strategies based on an extensive performance database—is
reportedly available from Aqua Test Inc. of Kent, WA.
Filters, Bugs, and Bubblers
As Rubin outlines the technologies, automation measures consist
of two basic types, the first being a “fixed-media treatment
process,” such as a sand filter or any other kind of
filtration medium. The second is a “suspended-media treatment
process,” in which air is bubbled “essentially through
wastewater,” and the microorganisms that consume and
digest the fats, oils, and greases “are retained in suspension
due to the buoyancy of the air bubbles.”
Filtration devices are present in almost all FOG and BOD
regimens, starting with the pre-rinse sink strainer for organic
solids, which are manually removed. For FOG control, more
advanced two-stage filters can be applied, allowing FOG to
be trapped in a permeable material; saturated filters are
then easily removed and discarded like daily coffee grounds;
neglect, however, leads to problems. Traversing a filter membrane
requires pressure from a pump or lift station—meaning
another element to maintain and monitor judiciously. This
dimension can be labor intensive, notes Lisa M. White, environmental
supervisor for Texarkana, AR. Due to exceptional circumstances
in her area, she once permitted three mall restaurants that
were far removed from exterior building walls (where interceptors
are normally buried) to install an Agricultural Products Inc.
ECH2O grease trap filtration system, as an alternative. “The
units work,” she reports, and produce an effluent of
less than 100 mg/L, “but only if they are maintained,”
i.e., cleaned once daily or more. If neglected, they clog.
This, she says, is “bad news.” She recommended the
restaurants install a filter double the size that the manufacturer
had specified—a judgment later confirmed by the high
waste volume that ensued. Manufacturers may not fully understand
kitchen operations, she suggests.
Rabe notes that he custom-designs numerous recirculating
sand and/or gravel filters, as do other wastewater engineers
he knows. A popular product in this category is Orenco’s
AdvanTex system, based on circulating textile filters (which
work essentially like other filters except with a different
medium). “It’s just a very compact version of a
recirculating, fixed-film, packed-bed media filter,”
he explains. Such filters introduce the dirty water into a
porous media design “so it can react with the microorganisms
in the presence of air,” he says, “and in that case,
we’re moving water through the air.”
FOG/BOD Reduction: Dinner for Two
In contrast, another aeration system, known as the Nibbler,
directs air through the water, but the net effect is essentially
the same. Its inventor, Bill Stuth of Aqua Test, notes that
the AdvanTex isn’t primarily for FOG control, but makes
a good complement to the Nibbler, because “it will take
the BOD of, say, 200 ppm down to just 10 ppm.” However,
he adds, it “has trouble” with FOGs above 30. So,
the Nibbler first reduces the FOGs, allowing the AdvanTex
to go to work clearing the effluent even further. This is
particularly desirable if high-strength wastewater needs to
be cleaned up thoroughly before heading into an onsite septic
drainfield. The Orenco product, he says, “is a good polishing
unit.” A restaurant might easily produce BOD water as
high as 2,000 ppm or more, he says, in which case, multiple
AdvanTex filters would be indicated.
Stuth stresses sizing of the FOG and BOD solution as a critical
facet. A system should be designed around anticipated daily
poundage, he says. In fact, this isn’t appreciated well
enough, and can serve as a kind of litmus test on vendor competence.
If a wastewater consultant comes along who doesn’t’
understand this, Stuth suggests, “then they’re probably
in trouble before they start.”
FOG constituent elements, Stuth adds, must be further analyzed
as to the specific fats and oils, and so too the water (i.e.
its temperature and additives, if any), along with tank flow
volumes. All are determinative and interactive; laboratory
analysis may be called for. He observes, “Everyone wants
a simple answer to a complex question—and there isn’t
one.”
Aerobic Treatment Units (ATUs)
As suggested, the real key to effective FOG-cutting (as opposed
to physical removal) comes by enhancing the natural aerobic
bacterial decomposition. All-important here is the role of
oxygen, which nourishes the microbes that gobble the grease
into constituent carbon dioxide and water. However, because
FOG is thick and gooey, oxygen doesn’t penetrate it,
and, in fact, very high oxygenation is needed to accomplish
rapid decomposition.
The solution? Add air, by churning the fetid, FOG’ed
water, e.g., with a propeller, air pump, or air injector.
Product literature from the Aero-Life grease trap amplifies
on this: “By putting a continuous flow of fresh oxygen
into the trap, conditions change dramatically. Natural aerobic
organisms begin to thrive. The metabolic breakdown of organic
materials proceeds very rapidly. As anaerobic activity ceases,
foul odors and acidic conditions are reduced, and pH is normalized…Blockages
and back-ups resulting from full traps are avoided. Customers
and staff are happier. Foul smells are reduced. ” And
wastewater treatment downstream is made easier.
An Aero-Life testimonial from an Applebee’s restaurant
reported these benefits after installing the product, along
with an annual savings on maintenance of $5,660.
Again, though, grease traps contain both floating FOG and
settled BOD debris; aerobically activated traps aren’t
typically designed to handle both (which explains, again,
that Nibbler-AdvanTex combination strategy previously described).
Given the empirical evidence of benefits, aeration systems
still aren’t that common (yet). One well-traveled pre-treatment
inspector, Neal Klimek, who said he’s seen more than
a thousand traps in five states, recalled finding only one
equipped with a basic “propeller” aerator—and
it seemed to make no difference in the trap’s operation.
Still other devices for augmenting the air-and-microbial
interaction involve using pipes, grids, and rotating disks;
grease-eating bugs are either affixed to a medium, such as
plastic or ceramic, or are suspended in the wastewater liquid.
The previously mentioned stainless steel Big Dipper, manufactured
by Thermacode, is categorized as a rotating biological contactor,
the microorganisms reside on a coated disk, which rotates
in the grease trap so that the bugs’ environment alternates
between grease (i.e., its food supply) and air. “This
is essentially an automatic grease trap cleaner,” as
Rabe describes it, and installing one may counteract some
deficiencies in kitchen staff diligence, especially where
a grease trap is under-sized. The Big Dipper begins to work
after hours (being operated by a time clock) first warming
and liquefying the FOG, so it adheres to the wheel, which
lifts it into a container, which can then be easily removed
for recycling. Stuth adds that, in a food service establishment
with relatively light FOG output, “the Dipper may sometimes
be adequate to bring the BOD and FOG down to safe levels—even
for a septic drainfield—but these would still be higher
than in residential septic, which is typical of most drainfield
designs.”
Stuth’s Nibbler invention is another aerator enabling
microbes to binge on a greasy banquet. “It’s like
a miniature treatment sewer plant,” he says, fitting
inside the trap, being custom-sized and positioned for each
grease device. “The Nibbler removes FOG by a factor of
about 90%,” Stuth says. “Once the fat leaves the
grease trap and gets to Nibbler, it’s not going into
the drainfield. We create an environment of natural microorganisms
that will thrive on FOG.”
One of Stuth’s distributors, Eugene Bassett of New Mexico,
installed a Nibbler for a pump tank next to a McDonald’s,
where, he says, “I’ve clocked waste strengths as
high as 900 to 1,100 [ppm], due to oils and grease.”
More typically, the BOD ranges from 500 ppm to 900 ppm, and
FOG comes to between 50 ppm and 70 ppm. After consulting with
Stuth, Bassett installed an 18-pod Nibbler measuring 28 inches
square, atop legs, and driven by a 3-horsepower blower. After
aeration, the BOD drops to 250 ppm to 300 ppm. “It has
worked really well for me,” he says.
The state of Washington, which has approved the Nibbler for
assorted sewage treatment tasks, has calculated the Nibbler’s
capacity more precisely as .81 pounds of BOD/pod/day
Similar to Stuth’s invention, the “Fast’ brand
is intended for lighter duty. It eats fats, oil, and grease
up to, say, 50 ppm, Stuth reports, but isn’t adequate
at 150 or 250 ppm. “If you’re not going to use the
Nibbler, then you have to use the Fast system,” he advises,
noting that it is adequate for light to moderate restaurant
FOG loads, especially those composed primarily of animal fat.
Another, later-generation aerator has emerged, trade-named
the Piranha. This, Rubin explains, “essentially combines
a biologically active medium” to which has been added
“a suspended media process.” The Piranha “jump-starts
the system because they’re adding microorganisms,”
he says, as opposed to the Nibbler, which activates the microorganism
more naturally. “Bill [Stuth]’s process might take
two weeks to start, but the Piranha might start in a week,”
he says. However, he notes that Stuth continues to make improvements
on his flagship Nibbler. Moreover, whether the microbes on
one or another device are relatively more or less aggressive,
he observes, “is not going to make a whole lot of difference.”
Still another system of this genre is the White Knight; microorganisms
must be added to it continuously, Rubin notes, in order to
maintain its warranty.
A newer variation has emerged from a company called Bio-Microbics,
which applies a honeycomb-shaped aerator—theoretically
improving the oxygenation. Rubin recommends visiting respective
manufacturers’ Web sites to gain more in-depth technical
discussion.
Enzymes, Bacteria, and Other Agents
So much for the air—a key catalyst to FOG-cutting. What
about bugs? These are the real active ingredient, but their
intervention into grease has been somewhat controversial,
and the results very spotty.
For one thing, microbes are often lumped together (both literally
and for marketing purposes) with enzymes and surfactants;
and these yield sometimes exotic mixes of multiple ingredients,
the exact contents of which are proprietary and difficult
to assess scientifically.
Klimek has worked for several states and cities in the Southeast
and Southwest; he now works for the city of Rio Rancho near
Albuquerque, NM. Though Klimek has encountered only one aeration
device in a grease trap, he estimates having seen nearly 400
that use microbial additives. Here, he says, the typical approach
is for the restaurant to put a “5-gallon bucket of bacteria”
under the sink and dispense it into the trap and/or drains
using a peristaltic pump on a timer system. The more scientifically
minded vendors apply multiple bacteria in custom-blended mixes,
depending on the eatery type, i.e., a KFC, McDonald’s
or an ice cream parlor. “There’s starch bacteria;
sugar bacteria; and ones for fats, oils, and greases,”
he says. FOG isn’t the only problem in view, as filthy
drains also breed insects and rodents. The bacterial formula,
he says, “needs to be fine-tuned for a greasy burger
joint, oriental cuisine, or whatever.”
Applying bugs successfully is, Klimek says, extremely tricky
and prone to failure. Proper conditions are essential. Narrowly
defined pH, detention time, temperature, and bacteria type
are critical. Of the hundreds of applications he’s seen,
Klimek estimates success in only about 40%. Batting averages
haven’t really been improving, either.
The most decisive factor in determining success, says Klimek,
seems to be the vendor’s competence. Moreover, products
themselves appear to differ significantly. Bugs of some vendors
can be applied in a powder (often with enzymes and surfactants
mixed in). In that state it takes a day or more to come to
life. For example, McDonald’s franchisees employ a drain
mix called “McFree,” but Klimek suggests that the
long lag preceding its activation, or other similar power
additives, probably impairs effectiveness.
Curiously, if the FOG-eating bugs succeed, another potential
problem arises for the restaurant, because the effluent is
no longer considered FOG. Hence, the grease recyclers “will
not touch that vessel because it’s not grease anymore,”
he says. Likewise, “septic haulers won’t touch it
either, because if they put their contaminated septic hose
in that septic tank, it contaminates the tank so it can no
longer be used for recycling,” Klimek says. “So
there’s a dilemma there: Who’s going to clean that
tank out legally?”
Moreover, adds Klimek, a number of municipalities now ban
the use of enzymes, bacteria, and other agents that allow
grease to emulsify and pass downstream. Another pre-treatment
coordinator and consultant, Patricia Tripodi, president of
Compliance Consulting Inc. in North Attleboro, MA, notes that
even if additives are allowed, the sewer regulations still
require regular pumping or other interceptor maintenance logs
anyway, so, she asks, “What has the application really
gained? …We try to a educate restaurant owner,”
she says, “that if you want to use these additives, it’s
your choice. It’s extra cost to your restaurant. But
you still have to maintain this trap. You still have to physically
clean this trap,” and hence, additives are far from a
cure-all “and aren’t even always advantageous.”
Gourmet Bugs Chewing the Fat
In defense of the microbial additive industry, Brian Lewis
of IET-Aquaresearch Ltd. reports that the company’s Bacta-Pur
product “converts 100% of fats, oils, and grease into
water, carbon dioxide, and soluble biomass” using EPA-approved
bacteria. Moreover, Bacta-Pur contains no enzymes, chemical
additives, surfactants, or emulsifiers, he says, and is pure
bacteria—thereby enabling it to be legally used in jurisdictions
that have banned other ingredients.
Unique to the Bacta-Pur methodology, Lewis continues, is
the fact that the bugs are injected into the grease trap (or
connecting pipes) in a continuous stream based on 6-minute
intervals. Most importantly, they arrive to the task not only
fully activated but in an induced “famished” state.
This intensifies their effectiveness dramatically. “Nobody
else, to my knowledge, is able to do that,” he says.
As a result, in the typical two-chambered grease trap, noticeable
improvement will be apparent within seven days in the first
tank; within two weeks, it will be “virtually clean”
and FOG-free. In the second chamber, improvement will be noticeable
in three weeks, and the compartment thoroughly FOG-free by
the end of one month. A no-risk trial offer is available,
followed by a service contract.
More than 1,000 restaurants, Lewis says, are now “Bactivated,”
as it were, but Lewis anticipates an immediate upsurge to
double that, due to the extremely low cost of the dosages
and the fact of the now rapidly proliferating sewer surcharge
imposed on high-strength waste. “We love it,” he
says, “when municipalities pass those kinds of regulations.”
Bacta-Pur provides benefits to the entire plumbing system,
he notes, “basically stopping backflow problems,”
or clogging and odors, and should therefore be used even if
a local regulation requires other maintenance.
Lewis concedes that the industry does carry some baggage
due to early failures, but drawbacks have now been overcome.
He agrees with Klimek that the bugs’ living conditions
(i.e., temperature, acidity, nutrient affinity, etc.) must
be closely calibrated. However, this is easily done in his
product by an automated, sensitive Bactivator application
device.
Product Selection: The Support Factor
On a final note, when evaluating the relative merits of products,
there’s the usual caveat to be made regarding manufacturers’
claims. Rubin advises (as do several others): “Ask for
scientifically validated, third-party proof.” To date,
relatively few products appear to have secured such independent
verification—Bio-Microbics being one, he notes. Also,
investigate the likely after-sale care; several pretreatment
managers reported a dearth of skills and knowledge among front-line
septic pumping staff in particular, and in wastewater services
generally. “What I would look at,” Rubin advises,
“is, first, who services a unit in my area? You can have
the best treatment device out there, but if nobody in your
area services it, it [isn’t] going to do any good. These
devices do work—when properly managed.”
As for cost-recovery, it’s already been noted that,
thanks to expensive sewer surcharges and high pumping fees,
it’s becoming easier to justify an onsite equipment investment.
It’s not unusual, as Rabe points out, for a restaurant
to calculate the initial cost of an ordinary grease containment
system but completely overlook the hundreds of dollars it’ll
spend every month needed for assorted upkeep. A restaurant
that can find and invest a few thousand dollars in a good
filtering system, he suggests, “may recoup that in less
than a year. They’ve basically paid for it by lowering
their operating costs down the road—and that’s a
big part of what should be considered in these systems.”
DAVID ENGLE, a writer based in La Mesa,
CA, specializes in construction-related topics.
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- November/December 2005
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