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Business Operations

Wash water management 101

October 11, 2010
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I’m going to list a few terms. You tell me what they mean to the professional carwash operator.


Impact fees.

Water/sewer rate increases.

Mandatory reduction.


They all really mean the same thing: the industry is becoming accountable for water, the prime ingredient in the wash equation. The other components — chemistry and mechanical action — are controllable and manageable, but water is becoming more expensive and, in some locations, scarce.

All about control
Thinking in the past seemed to be the best reclaim system was no reclaim system. “The easiest way to fix a reclaim system is to turn it off.”

Times are changing and while you could still turn the system off, it might be synonymous with the term “out of business.” It might be the government forcing you to close for not reducing or recycling water, or it might be the escalating costs forcing you to make that difficult decision.

So what does it take to produce odor-free, particle-free wash water that the customer thinks is fresh water based on its clarity? It is not a miraculous reclaim machine. It takes a systematic approach and control.

The reclaim unit may be the heart of the system since it is a pumping plant that allows us to defy gravity. The reclaim process is a combination of our physical site (trench, pits, and piping), an understanding of the active chemistry being applied, and the reclaim unit.

Each conveyor site is a little different, but as a whole, it is easiest to institute reclaiming water at a conveyor carwash due to the physical facility and presence of personnel with controlled operating hours. Staff can manage which vehicles enter the wash area, and a larger physical facility gives operators the chance to trap and contain more solids and contaminants in the trench.

What is wash water?
A definition of wash water is all water used in the wash process with the exception of water used for the application of chemistry or final rinsing. In the typical conveyor carwash, this will equate to be approximately 70 percent of the water used in the wash process.

A typical water consumption chart for a single vehicle shows the percentage calculation:

Management of the solids and contaminants left from the wash process is a key to improving wash water quality.

Solids management simply means keeping the dirt as far away as possible from the source you are drawing the wash water from. The tools available to the conveyor operator are a long conveyor trench and reclaim tanks.

Contaminants heavier than water sink, while lighter contaminants float. Properly designed trenches and reclaim tanks use gravity to achieve the clarification process. Solids sink to the bottom of the trench and oils will float and be trapped in the reclaim tanks.

Why does reclaim water smell so bad?
The plain truth is the water in a reclaim tank can smell just like a septic tank because, essentially, it is a septic tank. Nature is at work and the process is biodegrading contaminants. Biodegrading means the contaminants are breaking down naturally through the action of biological agents, especially bacteria. In other words, the contaminants are decaying. Hence, the smell associated with rotting, just like a septic tank.

Bacteria are natural biological agents; give them food, they thrive and multiply. Let the water stand still (like in a wash water reclaim tank) and bacteria will thrive and create odor resulting from the biodegradation process. Spray the water on a car and the odor will go through air conditioning vents and cling to the vehicle surface.

If you take away the food supply, these biological agents cannot thrive and multiply. It’s just status quo for them and they sit, naturally, waiting for the opportunity to consume food.

In the wash process, we use chemistry (i.e. bacteria food) legally certified to be biodegradable. We find ourselves in the Carwash Industry’s Catch 22: there are trenches and gravity tanks to store and clarify water we want to reclaim, but we keep adding wash chemistry (food) into the reclaim tanks.

The questions becomes: “How do I get rid of the smell from the reclaim water?” The answer is: “Get rid of the food and they will starve to death.” It is easier said than done, but the professional operator has tools at his disposal to combat this problem. It boils down to the more arches of reclaim water used in the wash process, the more concentrated the reclaim water becomes with chemistry and contaminants.

The pretreatment tools available today provide alternative solutions to address odor issues that will be encountered with the use of reclaim water in the wash process. These multiple alternatives are necessary due to the dynamic nature of wash water.

What about clarity of the reclaim water?
Clarity of the reclaim water is directly impacted by the contaminant load being carried by the water. The contaminants are composed of a few things, including residual chemistry, anything that is washed from the customer’s vehicle, and anything else that falls into the conveyor trench.

Conversely, the final water clarity is directly impacted by the ability of the reclaim system to remove the contaminant load. Typically, water clarity or color varies from light grey (near clear) to black. Components of the reclaim water can be solids (dirt, clay, brake dust, or lint from friction material), oils (road film, oils from the vehicle or wash equipment, residual chemistry, and matter left from the biodegradation process).

It is the function of the reclaim system to remove as much of this contaminant load to achieve a finished product that will not create damage to the vehicle surfaces, wash equipment, and is visually acceptable to the customer.

Final filtration
The final filtration characteristic of the reclaim unit sees many different forms of devices that process water with varying flow rates and means. These devices are the result of evolution of recovery systems over the years.

Maintenance associated to these filtration devices will vary, but all need some type of maintenance. It is the simple fact the reclaim system is a piece of equipment, not a miraculous black box.

In the end, there is no denying that the world of reclaim in the professional wash environment is evolving to become a necessary tool in the wash process. We have seen an evolution of equipment and application knowledge to better address the use of reclaimed water in the wash environment. Rest assured, if reclaiming water is ever mandated by the government here or in your municipality, the carwash industry has evolved to offer tools and is prepared to make this a reality.

Bob Koo is president of Aqua Chem Inc. He has been in the water treatment industry for 14 years.Koo can be reached at

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