The Skunk in Your Trunk...
Tackling Odor Problems in the Wash Bay
By Kerry G. Smith

The biological approach to odor control also helps to decontaminate waste water.

With water shortages becoming more common nationwide, more car wash operators
are turning to wastewater reclaim systems. This trend is growing dramatically. Operators are forced to deal with pit odor in the wash bay through scheduled cleaning and pumping. Adding a reclaim system brings a whole new dimension to odor control. Reclaim systems developed for car washing equipment generally do not adequately control odors. Decomposition of organic matter by naturally occurring bacteria and/or chemical reactions will release odoriferous gases, which can be very offensive in nature. Many of these bacteria and the gases they produce pose health risks.

Car wash customers are not likely to continue spending money for a car wash just to find that an unwanted passenger has boarded their vehicle and unwittingly is being taken home. We call this passenger "The Skunk in Your Trunk." Let us help you sort out the many approaches used in addressing this problem and guide you to a solution that is just right for you.

OZONE AND OTHER CORROSIVES

Some car wash owners use ozone gas (O3) produced by ozone generators and/or UV light tubes. It's introduced into wastewater to kill naturally occurring bacteria by direct contact. Ozone will attack organic matter first and the remaining ozone will then attack the bacteria. Highly corrosive in nature, it degrades organics and bacteria found inthe wastewater by oxidizing them. If enough ozone is present, heavy metals will also be oxidized, thus reducing contaminant levels when discharging treated water to sanitary sewers.

In reclaim systems, ozone alone generally is not effective enough to eliminate odor problems. This is due to its short half-life of only 25 minutes. This means you must create enough ozone to treat the entire system and bring it in contact with all of the wastewater every 25 minutes. Many reclaim systems require very large water storage tanks, sometimes containing as much as 18,000 gallons. Here's an example: In a smaller 5,000-gallon system, wastewater must be passed through the UV system or an ozone injection system at a rate of 200 gpm to bring all of the water in contact with the O3 to achieve an effective kill. Moving the wastewater this quickly through a 10 to 50 gpm wastewater treatment (reclaim) system will negate its ability to settle out solids or coalesce oils and will effectively defeat the system. Another method for introducing ozone uses air (gas) injectors located in the sump pits (like an air stone in a fish tank). These tend to stir up the water and sludge defeating the settling capability of the pits. Maintenance is higher because the injectors tend to clog quickly.

Most operators end up supplementing ozone with other oxidizers such as chlorine and hydrogen peroxide that have a much longer residual (kill time) effect. These are added to the system in a liquid form. As with ozone, these chemicals are very corrosive and do damage to every metallic object they come in contact with in wash bays, car washing equipment, and customers' vehicles. This is evidenced by the corrosion found on all metallic parts in car washes using these products.

The safety risks of ozone are not yet fully understood by our medical community, but it makes sense to me that if ozone will kill bacteria -a living cell - it will also do damage to human cells. Hot tubs have used ozone for years but have special carbon filters installed in the reaction tanks (where the ozone is injected) that remove the O3 gas before it reaches the atmosphere. This protects the occupant of the tub. Installing carbon filters to remove the ozone prior to use of the recycled water in a car wash would create maintenance problems few operators would be willing to deal with.

THE BIOLOGICAL APPROACH

Biodigester products are available in dry (shown) and liquid formulas.

Biodigester microorganisms can eliminate industrial wastewater odors by out-competing the
naturally occurring "bad" bacteria. Sometimes they are mistakenly referred to as enzymes, a protein that breaks down organics but does not consume them. These are not complete biodigester products, and will not do the job. Enzymes used alone will emulsify oils causing them to pass through an oil/water separator and into the sanitary sewer. The sewer department monitors grease and oils routinely and will surcharge those who exceed their discharge limitations.

Having said that, naturally occurring bacteria already in the system produce enzymes - but often not in the correct combination of strains and numbers required. Enzymes prepare organics and hydrocarbons for consumption by the bacteria. This is called "Step Degradation," a process where long chain hydrocarbons are broken down into fats, then simple sugars, and finally are consumed by the bacteria.
The best biodigester products are a combination of targeted bacteria, lab-grade purified enzymes with micro and macronutrients. Bacteria and enzymes should be targeted to the food sources available to them in a wastewater treatment system. By out-competing the naturally occurring bacteria for the food sources, odor-causing bacteria die off and thus the objectionable smell is eliminated. Purified enzymes are important. Without purification, the manufacturer has no idea how many of the proper types are present or whether in the correct quantities.

A simple pump-and-timer device takes care of automatic dosing of the liquid formula.

If properly selected, biodigester bacteria are so prolific that their numbers double every 15 to 20 minutes. For instance, if you start out with one cell, in fifteen minutes you have two and so on. In 8 hours you will have 17 million, and in twenty-four hours you will have a 1 with one hundred and twenty six zeros behind it. They simply outnumber the naturally occurring bacteria present in the system and take control. Due to the life cycles of bacteria, biodigester products start to lose effectiveness in 10 to 14 days and additional product must be added periodically to reinforce the colony with fresh bacteria and enzymes.

BACTERIAL SELECTION

There are over 15,000 known bacterial strains. Look for a product that has bacteria and enzymes that are selected for their ability to aggressively break down the targeted materials. In this case, organic matter and long chain hydrocarbons like oil, grease, and fuels. Only facultative strains of bacteria should be used, ones that can operate in aerobic (with oxygen) or anaerobic (oxygen depleted) situations. These types of bacteria are more effective in an aerobic state and will work five to seven times faster with air.

Take into consideration other factors like resistance to high and low pH, chemical shock, and temperature ranges that the washing equipment will operate at. The product should tolerate a pH of 5.5 to 9.5 without dying off, but the closer to neutral pH of 7, the better it will work. The product should be resistant to disinfectants like chlorine up to 150 ppm and remain active in temperature ranges of 50 to 140 degrees F.

DRY AND LIQUID FORMULAS

Biodigester products can be found in two forms, liquid and dry. Liquids are easier to automatically dose into your system but usually have a very short shelf life. Look for a liquid product that has a guaranteed shelf life of one year with a cell count of 500 billion cells per gallon. Dry products are more concentrated
but require manual dosing. Look for a minimum cell count of 2.5-trillion cells per pound and a shelf life of at least 2 years. Products with lower cell counts may not be effective and are certainly not a good value. Also make certain that they include active enzymes.

PRODUCT SAFETY

The biodigester product you choose should be guaranteed pathogen-free and every batch should be checked for purity. Stay away from Genetically Engineered products; choose only those that use all naturally occurring strains of bacteria. The product should also be approved by the Food and Drug Administration (FDA) and listed on the Generally Regarded as Safe (GRAS) listing.

GETTING STARTED

Once you have found the product that suits your needs, kill the entire system with chlorine bleach from the supermarket at a rate of one gallon per 500 gallons of water in the system. Wait two to three days for the chlorine to dissipate before dosing. Use a dry formula for seed dosing (initial propagation) following the rates suggested by the manufacturer. You simply mix the product into warm (not hot) water and evenly introduce it into all water holding tanks within the system.

Liquid can then be automatically dosed into the treatment system. Dosing systems commonly available are a simple pump and timer apparatus that allow you to determine how often and how much product you add into the system. When setting up your dosing system, try to set even dosages at even time intervals. More often, the less you use, the better.

ADDITIONAL BENEFITS

Ozone, chlorine, and hydrogen peroxide do nothing to aid the wastewater treatment system. Biodigesters break down and consume contaminants such as organic matter, oils, grease, and other hydrocarbons like dissolved solvents and heavy and light fuels. This is in addition to the odor reduction.
Biodigesters will propagate in the sump's bottom solids (sludge), reducing them by up to 50 percent, liberating oils and grease, and digesting them. In most cases, using biodigesters makes the sludge removal process non-hazardous, thereby reducing waste hauling fees. Biodigesters will take up residence throughout the entire system, constantly eating it clean. Media filter changes are reduced, coalescing plates are kept clean, and pipes and valves don't plug up. The result is a significant reduction of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Suspended Solids (TSS). The byproducts produced from this biological transformation are absolutely harmless and "stink" free. Only carbon dioxide and water remain.

With an understanding of how to effectively combat that stench in the wash bay and a little investigation, nobody needs to have a "Skunk in Their Trunk."

Kerry G. Smith is national sales manager of Hydro Engineering Inc. in Salt Lake City, UT. You can reach Kerry via e-mail at ksmith@hydroblaster.com.