In the 1800s, Max Aue developed the small community of Leon Springs outside of San Antonio. In 1929, Max’s son, Rudolph, opened a gas station, garage, and grocery store. In 1989, “Bar-B-Q” was added to the Country Store and Rudy’s “Country Store and Bar-B-Q” was founded.
—Rudy’s Country Store and Bar-B-Q Web site
In July 1998 Austin, TX, saw the opening of its first Rudy’s restaurant. Today, Rudy’s has stuck with its old-time formula of serving coleslaw, potato salad, and Texas-style baked beans, as well as giving all customers their choice of meat—dished up on a sheet of butcher paper. (When a customer-specified meat size is met within a tenth of a pound, a raucous cheer goes up from workers behind the counter.) Rudy’s famous barbecue sauce is already in bottles on the tables. To wash it all down are lots of sugary soft drinks (especially tough on wastewater systems), topped off with homemade banana pudding.
With bigger sales comes more water use, which in turn creates more wastewater. As more and more customers enjoyed Rudy’s barbecue, the septic system began to buckle under the mounting burden of processing the wastewater.
The Problem
Trouble with Rudy’s septic system began surfacing about three years after the restaurant opened. When it experienced the first trouble in 2001, it initiated a complete system cleanout as well as starting regular maintenance. Over time, even with this habitual maintenance, the system began having periodic wet spots. These occurrences were addressed on an as-needed basis. The regular maintenance originally included pumping the grease trap once per quarter.
Over the next five years, Rudy’s management team made a herculean effort to keep the septic system operating and in compliance with all appropriate regulatory codes. This required the hiring of a contract service that pumped and hauled sewage and repeatedly cleaned field lines. Initially, the service contractor had needed only to pump the tanks and haul off the excess sewage once every few months. Over time, however, the frequency of this pump-and-haul operation increased; by 2006 the company was pumping and hauling as often as twice a week.
The original design was intended to handle 2,500 gallons per day, but the system did not have the capacity to handle the high-strength wastewater created by a restaurant. In particular, it did not have the capacity to handle the fats, oils, and grease (FOG) typical of restaurant wastewater.
In 2005 it had become readily apparent that the system needed to be replaced. The success of the store had increased high-strength wastewater flows beyond the original design capacity. Because of the FOG clogging the dispersal field, the system was experiencing a marked reduction in performance.
“Having sewage surfacing in the field behind Rudy’s was not only illegal from the onsite prospective, it would also violate their food permit,” says Jeff Snowden, president and owner of Snowden Onsite Septic Inc. (Snowden is also president of the Texas State Onsite Wastewater Association.)
Snowden Onsite Septic Inc. is an Austin-based sales and service company with decades of local experience in the design and service of onsite wastewater systems. Its specialty is the repair and maintenance of septic systems. The company has 30 years of hands-on experience with dozens of different brands and types of treatment and disposal processes.
“When a food inspector visits and finds unsanitary conditions, including septic, they have the power to shut a business down immediately or force the installation of an alternative system,” says Snowden. “In the case of Rudy’s Bar-B-Q, they kept their system in compliance by hauling off enough of the sewage to mitigate this situation as well as going out periodically and cleaning the field in an effort to help matters.”
But it was obvious as time went on that the septic system was functioning progressively worse and would soon stop working altogether. After struggling for five years, Rudy’s management decided enough was enough. The restaurant needed a new, better septic system.
“The decision to install a new system in some ways was a risk aversion strategy,” says Snowden. “If the pump truck fails to show for some reason and sewage escapes, the risk of shutdown is very real. Installing a system and amortizing that cost substantially reduces the risk; this highly profitable restaurant could therefore continue to operate.”
This time the septic system would be different. The problem with the previous system was obvious. Just as fats, oils, and greases can plug human arteries, the fats, oils, and greases that are a natural part of all restaurants had been slowly plugging up the septic system. This time the company knew it needed a system that could better handle heavy restaurant waste for the long term.
Restaurant grease traps are undersized in most onsite systems. The common sizing procedures, such as the Uniform Plumbing Code, recommend grease trap sizes that are inadequate for onsite applications, according to Snowden. On a sewer, the limit on FOG that can be released from the grease trap can be as high as 200 milligrams per liter, but rarely less than a limit of 100 milligrams per liter. In onsite systems, however, the FOG must be in the residential range of around 20 milligrams per liter.
Another complicating issue is that grease traps, as the name implies, are intended to trap grease, but restaurants commonly are no longer using grease in their cooking. Restaurants have moved to using liquid oils in their cooking, and these liquid oils are much more difficult to separate than grease. This requires larger grease tank sizing than normally recommended by the current common sizing procedures.
There is a significant contrast to the difficulty in treating restaurant wastewater versus residential wastewater, which may not be commonly known or considered. Traditional onsite treatment products (of which there is a plethora) are designed to handle residential-strength wastewater parameters, not restaurant-strength wastewater.
The common measure of wastewater strength is biological oxygen demand (BOD). Residential wastewater is around 200 BOD, while restaurant wastewater is more typically 1,000 BOD with some measurements as high as 18,800 BOD. Further, the fats, oils, and greases in residential systems are around 20 milligrams per liter, while restaurant is around 200 milligrams per liter and even as high as 2,000 milligrams per liter. All of the elements had to be taken into consideration in the design, building, installation, and maintenance aspects in creating the right solution.
The Solution
Rudy’s needed a system that would last at least several decades, preferably for as long as it operates the business at this location. Snowden Onsite Septic Inc. guided the restaurant through the process of designing, permitting, and supplying the specialized equipment needed for the job. Snowden specializes in upper-end solutions.
“We earn our money through what’s between our ears, through designs, troubleshooting, and workups of complex systems not everyone may understand,” says Snowden. “These may use more advanced systems, such as the Nibbler, a patented process, or Perc-Rite.
“Perc-Rite is a subsurface drip disposal solution covering an acre and a quarter of ground with drip tubing just below the surface. These contain filters which are automatically flushed and have automatically timed dosings. The objective of these is to bring industrial-strength wastewater down to the level of residential-strength wastewater.”
After completion of the design and being awarded a permit to construct, Grubert Equipment Contractors Inc. of Austin was selected as the contractor for the construction of this first-of-its-kind system. There have been other projects using bits and pieces of this approach, according to Snowden, but the others were a sixth of the size of treatment capacity. The others did not employ a drip field or a system that covers one and a third acres of subsurface drip-field ground space. The others were not installed at an existing restaurant while the restaurant remained open serving customers at full capacity. The drip-field technology was installed directly over the older failed system. The dimensions are approximately 58,000 square feet of drip field, roughly somewhat over 1 acre in size. The others did not install power-assisted vent lines to vent odors not only from the treatment process but also from the store and the portion of the system before the treatment process to a point away from the restaurant and through biofilters.
Biofilters blow sewage odors through treated natural media, and the sulfur-based, rotten-egg odors are reduced or eliminated. Front to back, the system has power-assisted venting through biofilters to cover both ends of the process.
Many Factors
Issues that complicate the design include the difference in wastewater strength parameters based on the type of food fare served, and the method of serving. A buffet will create higher-strength wastewater than individually served meals. The management operation practices of the individual restaurant also cause widely differing wastewater strength and flows. Low-flow fixtures can reduce the hydraulic loading, but often increase the waste strength to the system.
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| This lawn shows no evidence of wastewater treatment below. |
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| The new wastewater treatment system was installed without uncovering and removing the old disposal field at Rudy's. |
The method of dishwashing, hand versus machine, makes a difference, as does the difference between high-temperature rinses and chemical disinfection rinse. The type and amount of sanitizers and other chemicals used in the restaurant can have dramatic negative impacts on the system. The better the sanitizer, because it kills bacteria, the worse it is for the onsite system.
Among the biggest challenges faced by the Onsite/Gruber team were those of designing a system that could be constructed while the restaurant was open and of building it in the remaning wooded area of the site without having to remove the natural tree cover.
In addition to solving the technical issues of handling the volume and strength of the wastewater and its odors during construction was the fact that the restaurant would still be generating wastewater. Incredibly, Snowden had to figure out how to accommodate all of it—without a single spill.
The odors from digging up old septic tanks could not impinge on the patrons of the store—ever. Also, patrons often bring their food outside to a picnic patio, which could not be affected either. The noise and traffic associated with the construction could not encroach on the traffic patterns of the store. A system needed to be installed that did not require uncovering and removing the old grease-laden, failed disposal field. The field had to be bigger, but the available land was covered with numerous desirable trees that must remain. The field, when finished, had to be an asset to the store because it was an area where families played with their children. In summary, there needed to be virtually no evidence to the general public of the existence of a large, aggressive, high-strength treatment and dispersal system.
Essential to Solution
Aqua Test Inc., a leader in high-strength wastewater treatment, based in Black Diamond, WA, handled consulting and advising on this project. Aqua Test has much experience with restaurants, bakeries, delis, and other high-output food establishments. Work is with anything higher than residential wastewater streams, typically approximately 140 milligrams per liter BOD.
“We typically see, in food service, BODs from 1,000 to 1,700,” says Matt Lee, Aqua Test owner. “We size up to BOD5 because it’s well understood by the people we’re working with. There is less understanding about how to size anything off oil and grease. To be able to communicate with lay industries, it’s common practice to use BOD5 numbers for sizing. Supermarkets, delis, bakeries, meat markets, or anything serving food are going to have a higher-strength wastewater well in excess of a residential flow, often in excess of the 1,000-milligrams-per-liter benchmark.”
(The five as a subscript on the BOD relates back to the fact that a five day chemical analytical test was involved—originally used in England where the wastestream was studied downstream on the Thames River five days later to see how the water was affected.)
“Our systems are performance-guaranteed, typically for 20 years,” says Lee. “Aqua Test treatment units come in modular sizes, so instead of being five units marketed, we really offer an infinite number, as customers can add as many units as needed for their individual systems.”
The engineer or designer will approach Aqua Test and describe the flow and waste strengths for particular situations. Aqua Test will then calculate the requirements for meeting the specific waste-stream. In some cases, where the flow is especially great, it might even be suggested that a municipal waste treatment plant would be the least expensive option.
“We have systems at 20,000 to 40,000 gallons of wastewater per day,” says Lee. “We supply the design and sizing of our system, including working with our database of wastewater analysis from a multitude of different styles of restaurants or settings. Once all data is collected and referenced, to make sure the suggested treatment plant has been sized accurately from Aqua Test’s prospective, the organic side is considered. The formula used is: flow times waste strength times conversion factor yields pounds per day. At that point Aqua Test sizes their treatment component, the Nibbler tank (which is retrofitted in concrete tanks), and after passing through that the waste-stream reaches the clarifier, where any suspended solids coming off the system are trapped.”
Any system upsets, such as bulking caused by chemical imbalances, may also be caught at the clarifier position. Pathogens left can be killed off before the final disposal component, which in the case of the Rudy’s site was a drip-irrigation system.
The only section of the system at grade level is the Nibbler, according to Lee. The rest of the system is below the ground in concrete tanks. “The Nibbler tanks must be on grade level in order to be reachable. This is one of the things we take advantage of in the marketing of our tanks: It must be 100% accessible for all the components treating the wastewater, enabling easy servicing so we can encompass to our performance claim.”
The Nibbler contains media in a unique configuration within a patented air-distribution system. These media are actually fitted within cages on legs in the tanks. The legs enable the media to be at a specific height within the tank for proper air distribution and mixing.
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| Proper maintenance keeps onsite systems running long-term. |
The Challenges
Major obstacles, aside from constructing the system, included how to come up with one, which, once it is turned on, must immediately handle restaurant-strength wastewater, not have odors, and then operate virtually hands-off for not only years but decades. Also, during the course of construction, operations had to proceed without anything affecting the income of the restaurant.
“We could not use any of their parking areas, block any access to the restaurant, and we had to stage and schedule our work so that portions of the system remained operational until we were ready to switch them over,” says Snowden. “This meant that everything had to be outlined with the Texas Commission on Environmental Quality and the local Travis County Agent for Transportation and Natural Resources before any work started.
“When you start digging up septic tanks you must be mindful of the odors, including which way the wind is blowing, when the restaurant is busy or not so busy, and really ready to go when it comes time to open up the grease trap—both the most odorous part of the system and closest to the building. It was a constant job, pumping and cleaning, and most of the work had to be completed at night.”
Grubert’s construction equipment consisted of large excavators for the large tank holes, large cranes for placement of large tanks, and track-mounted Bobcats for completing work over the top of the drip-tubing fields. In addition to operators, Grubert supplied its experience in scheduling and coordinating construction activities.
For the tank installations, at least some portion of that work had to be completed at night. Snowden designed a brand-new drip field using the Perc-Rite drip system. One half of it overlays the older field, and half is on ground that was never used before. The field had to be done right, as customers go out on the grass after their meals for activities such as touch football.
“These type of drip fields have been successfully installed under football, soccer, and baseball fields without players being aware of what’s just below their feet,” says Snowden. “The systems are adept at handling the wastewater flowing from septic tanks without further treatment and successfully disposing of it in soil.
“Austin has also been a very ‘tree-friendly’ city for a long while. We worked hard to preserve all the trees on the site, especially the very valuable live oaks on the property. We’ve removed all the grease through the treatment process. What’s in place is drip tubing 9 inches below the ground, native grasses in place all under the canopy of existing oak trees with a few junipers—some quite large—scattered among them.”
After the start of the new system, Snowden observed what the kitchen staff was using when it came to cleaning fluids. He then sat down with the staff and advised them on which chemicals could be harmful to the system and therefore the ground. In the course of further talks with the chemical sales people, he was able to find other ways of accomplishing the cleaning needs, but with less danger to the new system, all the while protecting public health within the store.
The toughest overriding challenge was that the system had to operate successfully for years to come-—and without the odors that are common with treating the high-potency characteristics of restaurant wastewater. The ultimate solution consisted of larger tanks as well as a treatment process that has a demonstrated history of successful performance in treating restaurant wastewater. By reducing it to the limits required by the State of Texas, it can be dispersed in a subsurface system that reuses the treated wastewater to irrigate native grasses and trees.
The Future
Even with all this larger and better equipment, the secret to success in an onsite system for restaurants like Rudy’s is the proper maintenance and upkeep on the system. Gone are the days of burying tanks and forgetting about them, according to Snowden.
“All onsite systems require some sort of ongoing oversight and maintenance, and restaurant systems obviously require much more than even the largest residential system. Regular visits to the site to measure and manage solids accumulation, treatment performance, and regular cleaning of such things as screens and filters are the minimum steps, which should be included in the operation and maintenance of an onsite system. Even the best system will malfunction if not properly maintained, and even the worst system can perform well if maintained properly.
“Rudy’s made a good decision and a sound investment for both the short-term operation as well as their long-term environmental impact and corporate profitability,” says Snowden. “Their investment in a state-of-the art septic treatment solution will save them substantial amounts of money, time, and effort for many years to come. In this case, the sweet smell of business success doesn’t smell at all.”
Henry Vere writes extensively on engineering and scientific subjects.
OW - March/April 2007 |
