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The Curious Case of the Smelly Blob

I don’t like unsolved mysteries. I never have. So, when a service contractor stumped us with a problem in the late 1990s, I just couldn’t shake it.

 

The contractor told us about gelatinous masses building up in a handful of grease separators. The masses smelled terrible, he said, and the separators had surprisingly low water input flows.

 

We tried figure out what the gel was. We ran tests in our lab. We looked online. We consulted wastewater treatment professionals and scientists. We just couldn’t come up with anything.

 

I kept picturing the monster from the 1958 cinematic classic, The Blob. Reluctantly, we filed the data and moved on.

Fast forward to 2011, when we learned of a major donut chain site in Beaverton, Or., where a concrete grease interceptor was literally falling apart after only six years. Beaverton’s Public Works Department manages its sewer collection system. Its collection flows are treated by the regional treatment authority, Clean Water Services. For years, the city had been jetting the collection line downstream of the donut store anytime CCTV assessment showed build-up in the line. There was always build-up in the collection line.

 

We cut a deal with franchisee. Thermaco paid to install a Trapzilla TZ-600 separator on site. The franchisee let us have an independent research firm, Environmental Engineering & Contracting (EEC), conduct a comprehensive before-and-after study of fats, oils and grease (FOG), total suspended solids (TSS), pH levels, and biological oxygen demand (BOD).

 

EEC collected several weeks’ worth of effluent samples from the concrete grease separator and, later, from the Trapzilla separator. The results shocked us. The study showed the site had virtually no grease in the effluent.

 

Why, then, was there so much “grease” in the downstream line? Why was the pH extremely low? Why was the FOG averaging 6674 mg/l downstream of the concrete separator and nearly 2/3 less after the Trapzilla separator was installed? Why did the TSS increase with the installation of the Trapzilla?

 

It was another mystery that needed solving.

 

This time, however, we had more data to work with. We discovered a specific bacterium, Acetobacter Xylinum, was eating the sugar, flour and yeast in the pipes from the donut operation.

 

Acetobacter Xylinum (also referred to as "Komagataeibacter xylinus") love donuts as much as we do. Humans have a multi-stage digestive tract to break down complex foods in a matter of hours. Bacteria, on the other hand, emit enzymes to digest food. A bacterium will also reproduce quickly and release toxins to block competing bacteria from the food source.

 

In Beaverton, Acetobacter Xylinum was producing acetic acid because other bacteria could not withstand pH below 5.0. It also protected its offspring by building dams and domiciles made of cellulose. You read it correctly – cellulose, the same stuff in cotton and wood.

 

I flashed back to the 1990s call with the service contractor and realized that smelly blob he reported had to be cellulose. The terrible odor he described was the result of low pH leading to any sulfur compounds immediately transitioning to sulfide. Another mystery solved!

 

Acetobacter Xylinum likes low-flow conditions where it can concentrate its acidic pH advantage over other bacteria wanting in on its food source. Acetobacter Xylinum especially prefers alcohols, so it loves sites with sugars and yeasts for converting starches into alcohols. (It is also the reason an opened bottle of wine tastes like vinegar after a few days.)

For our chemist readers, note that ethyl alcohol (the alcohol in beer, wine and liquors) is CH2H5OH. Vinegar (acetic acid) is CH2H5OOH. Only one oxygen difference between ethyl alcohol and acetic acid, and Acetobacter Xylinum takes ethyl alcohol and rapidly makes acetic acid to shoo away its competitors.

 

Ok, you say. We understand the low pH and cellulose gunk creation story. What about the significant changes seen in the BOD and TSS between the two different separators?

 

The 1000-gallon concrete grease interceptor had water turnover every 5 to 7 days. The site used about 100 gallons of water per day for kitchen and utensil cleaning operations. The Trapzilla unit’s 95-gallon capacity saw daily water turnover. Carbohydrates in the kitchen drainage were flour, cane sugar and milk sugars. Sugars were immediately available for yeast digestion, while flour took longer for yeast and bacterial digestion.

 

The 7-day water turnover of the larger separator gave plenty of time for the conversion processes and thus the lower pH and higher BOD. (Raw flour does not fully show its full BOD value on a BOD 5-day test.) The longer holding time in the 1000-gallon tank “processed” the raw flour into constituents more amenable to being eaten by the bacterial of the BOD 5-day test.

 

The longer holding period also made more alcohol production from the sugars and flour carbohydrates, resulting in much lower pH values. The same quantity of flour was present for both separators. The smaller separator’s daily water turnover had a higher TSS because these particles were undigested. No/less digestion in the smaller separator explains the higher (more favorable) pH values, the significantly lower BOD (undigested carbohydrates in the BOD 5-day test) and higher TSS (flour particles did not experience seven days of digestion by yeast and subsequently acetobacter xylinum bacteria).

 

Here's a simpler explanation. Low flow, long retention time and lots of sugars/carbohydrates leads to low pH conditions caused by happy Acetobacter Xylinum bacteria. You smell their actions in brewery drains (alcohols, yeasts, carbohydrates and low flows) and coffee shop drains (sugars, very low flows) and other sites having those flow and foods characteristics.

 

Don’t get stumped. When you find stuff that looks like grease, stinks especially badly and the site has little or no F.O.G. in its effluent, it’s no mystery. It’s probably Acetobacter Xylinum.

The Science That Saved Septic Fields

Each state has its own unique environmental challenges and aims. You learn a lot by attending state conferences.

 

I recall a trip to the Florida Department of Health Conference in 1986 or 1987, when the buzz was about a growing set of research on extending lifespans of septic fields for rural food service establishments (restaurants, schools, other premises with commercial kitchens). This work remains vital to rural communities to this day.

 

Damann L. Anderson and his team at the University of Wisconsin in Madison were leaders in this area. In the ‘70s and ‘80s, they focused on the nutrient loading effect on septic field lifespans. Septic field failure occurs when a septic field no longer properly absorbs effluent. Instead, the water ponds at the surface, a public health hazard.

 

To find the cause of this phenomenon, Damann and his team built simple devices called lysimeters. Lysimeters are clear pipes filled with layers of sand and gravel to simulate the soil around a septic field’s in-ground piping structure.

 

They assigned a lysimeter to each home and restaurant in their study. Wastewater dripped into the devices via an automatic dosing system. Details and results of their study are here.

 

Listening to Damann describe his research was definitely my favorite highlight of the Florida Department of Health Conference. A number of attendees had interesting questions. His answers always went into far more depth than what was in the research report.

 

Here’s the gist. Damann explained that every lysimeter receiving restaurant septic tank effluent eventually reached a failure stage. Wastewater stopped flowing through the lysimeter and ponded on the top-most surface of the media. As I recall, he said this happened in as few as 21 days and as many as 59 days. 

 

The lysimeters connected to the homes were another story. Not a single one failed for the household septic tank effluent. Damann and his team reached these conclusions:

 

1. The lysimeter media failed because of the biological mass accumulating and filling the interstices between media particles, clogging the media. (below left image)

2. The biological mass in the lysimeter directly corresponded to the quantity of nutrients in the septic tank wastewater in the lysimeter. More nutrient per ml wastewater corresponds to more biomass created.

3. Restaurant septic tank effluent contains significantly more nutrients than household septic tank effluent.

4. Septic tank system fields for facilities with commercial kitchen operations should be sized to handle a higher concentration of effluent nutrients.

5. Reducing commercial kitchen effluent nutrient loading extends septic field lifespan.

6. Residential results indicated there is an equilibrium effluent nutrient level where a septic field can safely operate without failure. (below right image)

Let’s go back to conclusion #5, “Reducing commercial kitchen effluent nutrient loading extends septic field lifespan.” When I first heard Damann make this point in Florida, it stuck in my mind. It shaped my work on several generations of Big Dipper automatic grease interceptors.

 

I came away with two main thoughts. One, pretreatment is vital to extending the lives of septic fields. And two, although restaurants with septic fields should be especially vigilant about wastewater purity, not all are. Kitchen staffs face distractions every night. Forgetting about grease is pretty easy.

 

So with each launch of a new Big Dipper line come features that make these units as hassle-free for kitchen staffs as possible. They don’t have to remember to schedule pumping service. They have to do little, if any, cleaning. Just turn it on and it automatically skims grease from the water.

 

Wait until you see what we’re planning for 2021. Damann is now vice president at the environmental engineering firm Hazen & Sawyer. But I’m sure he would love to see how his earlier research is still helping you keep your city’s pipes clean and septic fields healthy for many years to come.

Why Legionnaires’ Disease Is Suddenly A Very Real Problem and What You Can Do To Stop It

The Risks Are Legion

 

In September, health officials in a Canadian town just outside Vancouver scrambled to explain a rare cluster of Legionnaires' disease cases in its business district. The problem wasn’t as much a case of why it happened as much as where.

 

They knew the why.

 

Like most cities and towns around the world, New Westminster shut down in the wake of the pandemic. When businesses resumed, water systems that laid dormant for months suddenly had water flowing through them. That was a problem. Stagnant water in the pipes bred Legionnaires’ disease-causing bacteria, which was suddenly spreading everywhere. But which building – or buildings – was it? Inspectors zeroed in on those with cooling towers, air conditioning units and decorative water features.

 

This could happen anywhere. Building that have been closed for a week or more during the pandemic almost certainly have standing water somewhere in its pipes. And that standing water is trouble.

 

“The temperature of the water will reach the ambient temperature of the surrounding area, which is generally in the growth temperature range for Legionella bacteria,” explains Ronald L. George, CPD, president of Plumb-Tech Design & Consulting Services, LLC. “Where nutrients are present, Legionella bacteria and other micro-organisms can grow to significant levels.”

 

Water flow essentially makes the bacteria airborne. Workers in the building can inhale it into their lungs, causing Legionellosis or Legionnaires’ disease. Infected people may develop pneumonia. Symptoms show in 1 to 19 days and include fever, shortness of breath, severe fatigue, abdominal pain and diarrhea. Left unchecked, the disease can even be fatal.

 

The good news is you can stop it. Below, he details how the problem starts and develops and what you can do to help your community avoid being another New Bedminster.

 

How Legionella Bacteria Enters the Building

 

Cold water that enters the building from the water utility won’t be completely free of water-borne bacteria and other pathogens, such as Legionella bacteria. The Safe Drinking Water Act of 1974 (hereinafter, “SDWA”) and the regulations that are promulgated pursuant to the SDWA set minimum water quality levels that a water utility must meet for the water that it delivers to the water meter. 

 

Although a water utility should strive to deliver quality water, water utilities cannot guarantee safe drinking water because there are often water main breaks, construction, fire events and other disruptions of water main flows that cause turbid water, which leads to high bacteria levels in the water in the utility mains.  Currently, the SDWA and its regulations allow water utilities to fall below the minimum level of water quality for three, consecutive 6-month reporting periods, while they try to make corrective actions, before they must notify the public of a water quality issue.  Recently, there have been efforts to revise these reporting requirements.

 

At some point, the in-coming cold water from the water utility will have contaminants, including bacteria and other micro-organisms. These contaminants will enter the building water piping systems. The responsibility for building water safety is the responsibility of the building owner. The water utility has no responsibility for water quality on the building side of the water meter.  For this reason, the building owner should monitor the quality of the water coming into their building.

 

How Legionella Bacteria Grows in the Water Pipe System

After water enters the building from the water utility, any bacteria or micro-organisms that are present can grow and flourish unless controlled.  Under normal operating conditions, methods to control the growth of Legionella bacteria refers to maintenance of (1) elevated temperatures to limit colonization and growth of Legionella across hot-water systems and (2) sufficiently cool temperatures across cold-water systems.  

 

Legionella bacteria can also be controlled with chemical disinfection methods for cold-water systems; however, studies have shown water treatment chemicals dissipate over time, and there are several factors that affect the rate of dissipation, such as pipe material, temperature, and organic contaminants in the water. Chemicals rapidly dissipate in hot water systems, so elevated temperatures across hot water systems are necessary to control Legionella bacteria growth.

 

Warm water leaves a water system especially vulnerable to Legionella colonization and growth. See, Table A - Effects of Temperature on Legionella Bacteria.  

 

Table A – Effects of Temperature on Legionella Bacteria                         By: Ron George, CPD

Temperature                                                                   Result                                                                              

Below 68F                                                                       Legionella survives, but will not reproduce

68 F                                                                                  Legionella will double its population in 8 days

77 F                                                                                  Legionella will double its population in 3 days

68 F to 122 F                                                                  Legionella bacteria growth temperature range3                       

95 F to 115 F                                                                  Ideal Legionella bacteria growth temperature range

Above 122F & Below 131 F                                        Legionella bacteria can survive but will not grow or multiply2

131 F                                                                                Legionella bacteria dies in 5 to 6 hours2

140 F                                                                                Legionella bacteria dies in 32 minutes2

151 F                                                                                Legionella bacteria dies in 2 minutes2

158 F +                                                                            Legionella bacteria dies instantly (Disinfection temperature)2

Notes:

This is based on laboratory tests, field conditions may vary due to differences in water quality, insulating properties of biofilm/scale

Some types of water heaters are not capable of heating to non-growth or disinfection temperatures.

The coolest point in the hot water system (Hot water return pipe) should be a couple of degrees above the highest growth temperature. 

 

Legionella bacteria growth occurs between 68 degrees Fahrenheit and 122 degrees Fahrenheit.  Below 68 degrees F, Legionella bacteria can survive but does not grow; so, for example, if there is cold water supplied to your building with 1 colony forming unit per milliliter of water (cfu/ml) of Legionella bacteria, the bacteria will remain at that level until the water temperature warms up and the Legionella bacteria begins to grow.

 

At 68 degrees F, laboratory tests show that Legionella bacteria doubles every 8 days, and at 77 degrees F, Legionella bacteria doubles every 3 days.  Many people have said that in-coming cold-water temperatures at 77 degrees F are acceptable because, with normal use, any bacteria in the water will be flushed through the system during normal water usage. However, you should be aware that there may be “dead-legs” in piping systems, which are branches of water piping that serve areas of a building that have little usage.  When a branch or fixture has not been used or has not been flushed “clear” within 3 days, bacteria can grow to significant numbers when the water temperature is 68 degrees F or above.  Many infra-red faucets and ultra-low flow faucets allow flows that contribute to ageing water and bacterial growth in the water distribution piping system. 

 

To ensure that the hot water temperature remains above the Legionella bacteria growth range, a minimum temperature of 124 degrees F at the lowest temperature point in the system should be maintained.  To do this, hot water should be stored at temperatures in excess of 135 F - 140 F, or higher, to offset heat loss and maintain a minimum hot water temperature a couple of degrees above the Legionella growth temperature of 122 degrees F at the lowest temperature point in the system. The hot water should be delivered to the distribution system through a temperature actuated mixing valve that conforms to the standards in the model Plumbing Codes (ASSE 1017/CSA B125.3), and this will stabilize the hot water delivery temperature and control the hot water return temperature. 

 

In systems with circulating pumps, a temperature gauge should be located on the hot water return pipe after the circulating pump and just before the tee where the hot water return splits to direct the return hot water to the cold-water connection of the water heater and the cold-water inlet of the mixing valve, if present.  This is the lowest temperature point in a hot water system.

 

During periods of occupancy, the hot water system of the building would, ideally, heat and deliver the water to the fixtures at a sufficiently high temperature to control the growth of Legionella bacteria and other micro-organisms.  However, if the temperature of the hot water system is not a thermal disinfecting temperature (note: many instantaneous heaters cannot achieve and maintain a thermal disinfection temperature) or if the hot water system temperature is turned down to a lower temperature, then bacteria can grow and flourish across the hot-water piping system during periods of significant unoccupancy.

 

During periods where there is little to no water usage in a building that has been significantly unoccupied or not regularly used during the periods of shut-down, the water that sits or “ages” in building water pipes will have chemical treatment levels dissipate down to levels that will not control bacteria growth and the temperature of the water will reach the ambient temperature of the surrounding area, which is generally in the growth temperature range for Legionella bacteria.  Where nutrients are present, Legionella bacteria and other micro-organisms can grow to significant levels.

 

The “bio-film” that is generally present in both the cold and hot water piping systems will serve as a food-source for the bacteria.  All building water pipes that have been in service for a period of time will develop a “bio-film,” where bacteria and other micro-organisms can live without significantly affecting the quality of the water that flows through the building water pipes during regular usage.

 

However, when water sits and ages in the building water pipes, any bacteria in the water can grow to great numbers, using the bio-film as a foundation to grow and as a food-source.  Additionally, bacteria can live within the bio-film. When water flow resumes, the bacteria in the “bio-film” can be dislodged and enter the water stream that is delivered to the fixtures.

 

Challenges For Restaurant Operators

 

The restaurant industry faces some unique challenges with respect to plumbing systems.  For example, low flow rates encouraged by many voluntary water conservation programs are contributing to ageing water, even under normal operating conditions. 

 

For the restaurant industry, when infra-red, metering, or ultra-low-flow faucets are installed, hot water may not reach the lavatory or hand-washing sink by the time the user is done washing their hands.  These low flows do not allow hot water to get to hand washing sinks, and this also creates an opportunity for bacteria to grow in these branches to the hand-washing fixtures. In installations with infra-red, metering, or ultra-low flow faucets, the hot water needs to be circulated down into the plumbing chase and behind the plumbing fixtures, so that hot water is immediately available.

 

Also, there have been recent efforts to reduce the flow rates on pre-wash sprays for kitchen sinks.  Ultra-low-flow pre-wash sprays in kitchens contribute to poor drain line transport of solids and grease (fats, oils, and grease, or F.O.G.) and allows grease to coagulate in pipes before the grease waste reaches the grease interceptor.  These pre-wash sprays use hot water to remove grease and food debris from dishes before loading the dishes into the dishwasher. 

 

At these lower flow rates, the hot water cools off quickly, and grease can coagulate in the drain before it reaches the grease interceptor. If grease coagulation is a problem in piping before a grease interceptor, consider a point-of-use interceptor or grease removal device.

 

Another challenge the restaurant industry faces is with ice machines. Bacteria can grow in the flexible water supply tubing to ice machines.  When ice machines are installed in tight, poorly ventilated spaces, warm or hot air will be discharged into the space behind the ice machine. This warm or hot air heats up the water in the flexible water supply tubing to an ideal temperature for bacteria to grow.  

 

Generally, in the restaurant industry, there are cartridge filter assemblies that remove debris and solids out of the water before it reaches the ice machine, and a charcoal filter to remove the chlorine out of the water, so that the chlorine does not affect the flavor of the beverages. Ice machines are especially susceptible to Legionella bacteria growth because the chlorine in removed from the flexible water supply tubing.  If the building has been sitting significantly unoccupied for long periods of time, the cold-water piping serving the ice machine should be flushed, and the flexible water supply tubing and filters should be replaced.

 

How To Get Rid of Stagnant Water

 

When a building is significantly unoccupied for more than seven days, or a period of time agreed to by a building’s water management team, flushing should be performed immediately prior to re-occupancy. When a building is significantly unoccupied for more than four weeks (28 days), or a period agreed to by the building’s water management program team, flushing and disinfection should be done immediately prior to the building being reoccupied.

 

Make sure there is clean water in the utility main up to the water meter. The building service piping should be flushed before any flushing of the fixtures.  Flushing the utility main and the building service pipe first stops the introduction of debris into the building piping, valves, equipment, and fixtures.  Flushing the hydrant near the building will speed up the process and reduce the amount of water flowing through the meter.

 

Flush fixtures with the water heater turned off. Every fixture in the building should be flushed until the water treatment chemical residuals reach an acceptable level. Flush the fixtures in the following order:

 

  1. Sinks
  2. Showers
  3. Water Closets
  4. Urinals

 

Fixtures with flush valves can become clogged with debris and not flush properly if they are flushed first in time. If flush valves do not perform properly and run on, then shut off the water, remove the flush valve diaphragm, and clean the orifice. When done flushing, remove faucet strainers and showerheads and clean or replace them.  If flushing does not improve water quality, contact the water utility and consider contacting a water treatment professional. 

 

Taking these steps may seem like a hassle, but the alternative is far worse. Just ask the people of New Westminster. Its officials are not only grappling with a health crisis. At the time of this writing, they still had not found the building where the Legionella bacteria originated.

Guide for Ice Cream Parlors, Sweet Shops, Coffee Houses and Bakeries

We've received calls from operators of bakeries, ice cream parlors, sweet shops and coffee houses wondering why their Big Dipper automatic grease traps aren't collecting much grease. It's an easy answer. Your food operations don't produce much, if any, grease.

There are other more important things to be aware of, however. That's why we created this handy guide to help your Big Dipper work hard for your business. 

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Hydrogen Sulfide: The Bad Smell That’s So Much Worse For Your Business

As if business isn’t challenging enough in the current economic climate, an invisible fallout from the pandemic is lurking in the pipes beneath hotels and restaurants. And it really stinks. 

That offensive rotten-egg smell signals the presence of hydrogen sulfide creeping up from the grease interceptor into your business. During the pandemic, we’ve had calls from clients asking about the smell, and their stories are cautionary tales for all of us. 

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New drawings place Trapzilla in vehicle traffic areas

Delivery truckWhat is your plan when a city official, contractor, or engineer says a 1,000-gallon grease interceptor must be installed in your drive-through, parking lot, or another area where vehicles will be driving over it every day? 

Trying to comply with local codes and regulations shouldn’t be difficult. You shouldn’t have to use all your resources to engineer, install, and maintain a grease trap. It should be easier and more affordable. 

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How commercial kitchens can manage grease from rotisserie ovens

rotisserie chickens in ovenRotisserie chicken ovens have been steadily gaining popularity in commercial kitchens since 1985, when Boston Market first introduced them to the restaurant industry. Today, more than 750 million rotisserie chickens are sold every year in grocery stores, club stores and food-service outlets.

While the slow-cooked birds are a smart choice for retailers, the grease they generate can present a challenge for commercial kitchen owners and for municipal water treatment systems.

What options do kitchen operators have to ensure they still comply with municipal pretreatment and plumbing codes?

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How grease interceptors can reduce greenhouse gases


earth from outer spaceCommercial kitchen operators already know the benefits of using grease interceptors to capture used oil and grease -- cleaner sewage systems, reduced costs for wastewater treatment plants and fewer fines from municipalities.

Plus, you can protect your facility's interior plumbing and make a little extra money selling used cooking oil to recyclers.

But did you know that by capturing all that grease you're also helping cut greenhouse gas emissions?

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How a simple kitchen device protects waterways and sewer systems

Food in sinkWhen it comes to disposing of food waste, which works best for commercial kitchens and our waterways – garbage disposals or strainers?

At first glance, a garbage disposal might seem like the easiest choice – just flip a switch and the food is gone. No scraps to throw away. What could be simpler? Plus, you keep waste out of the landfill.

However, food scraps that enter the wastewater treatment system can cause problems with our municipal sewer systems. 

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Why steel grease traps fail

Grease trapGrease interceptors have different weaknesses and points of failure depending on what they’re made of. Those materials affect how durable a particular grease trap is, and often affect how it’s designed. Design choices, in turn, also affect the reliability and durability of a grease trap.

If concrete and fiberglass have problems, it seems as though it might make sense to use something stronger to construct the grease interceptor. Something like steel. But steel grease traps come with their own problems, and often have very short lifespans compared to other options.

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