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A blueprint of water use at carwashes

October 11, 2010
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Commercial carwashes come in many forms, with a variety of business and operating models. What most of them have in common, however, is the use of water. This article will suggest a blueprint for approaching the use of water in your carwash facility that will help you generate a cleaner car, save money, and be an environmentally good corporate citizen (also known as being “green”).

Water as a solvent
Water is the universal solvent. It has the capability of dissolving almost everything with which it comes into contact. When water passes through soil it “acquires” metals and salts along the way. Carbonic Acid, which exists in groundwater primarily through decaying vegetation and other organic matter, further enhances water’s ability to make substances soluble after it comes into contact.

In the United States, a vast majority of the country has underlying formations of limestone and over time, groundwater, containing varying degrees of carbonic acid, dissolves the limestone as it passes through it. As a consequence, 85 percent of the groundwater in the U.S. has various concentrations of calcium and magnesium present. These two minerals are considered components of “hard water,” and in addition to these minerals, other minerals, inorganic salts and metals such as iron, manganese and sulfur can also be found. To compound the issue, concentrations vary so that no two water sources are identical.

Pretreatment options
The presence of minerals and inorganic compounds (see sidebar on this page) must be addressed when washing cars. Depending on the concentration and combination of the compounds, these can wreak havoc on the quality and cost of the wash process.

Hard minerals form scale deposits that can plug nozzles, coat hot water heating elements, and reduce the cleaning effectiveness of soaps and detergents. The end result of this is a poorly finished product, increased energy costs, and higher chemical costs. Calcium, even in low concentrations, will plug the membranes in reverse osmosis (RO) equipment, thereby ruining your spot free rinse system. Lastly, staining from iron and the unpleasant odor from sulfur or manganese can produce an experience for your customer that is far less than positive.

Conventional water softeners can address water hardness issues and to some degree iron, too. Although effective, they can be cumbersome to operate and maintain due to ongoing expenses and the mechanical aspects of the system. They require a continuous salt supply, backwash regularly (thereby wasting large amounts of water) and the backwash discharge is becoming more difficult to permit since many municipalities are beginning to completely ban water softener discharge.

Simply put, the Publically Owned Treatment Works (POTW) cannot treat or process the backwash discharge from a conventional water softener, so it ends up passing through the treatment plant as effluent in their discharge. This can have a very negative impact on the environment. In addition, this brine water discharge can not be recycled by your onsite water recycling system either. It has to go to waste.

Recent breakthrough technology provides a very viable alternative treatment regime. Systems that cause the almost instantaneous crystallization of hardness minerals are now available as an alternative to water softeners. Numerous benefits, such as no salt or back washing make this process a very viable and cost effective alternative to conventional water softeners.

In addition, the smaller footprint, no wasted water and virtually zero maintenance make these systems an attractive alternative to conventional water softening.

Water recycling systems
Okay, let’s assume that you’ve pretreated your water. It’s perfect for washing cars, it won’t be plugging up your piping and washing equipment or staining your wash orange and it doesn’t smell like rotten eggs! Great! Now what?

It’s totally logical in today’s environment that you seriously consider installing a water recycling system that will treat your wash water to the degree required to allow you to reuse it. The days of using the water once and simply sending it to drain are rapidly coming to an end. If it isn’t the ever rising cost of water and sewer discharge fees that drive this consideration, it’s common knowledge that many parts of the country are struggling to provide enough water for all the uses we need it for.

Like our current energy crisis, we also have a water shortage issue in many areas of the country too. In addition, being environmentally conscious is becoming a way of life philosophy in this country. Certainly, many of your customers are concerned about water conservation.

To choose the right water recycling system you have to understand the physical and chemical characteristics of the waste stream, just like you have to understand the supply water characteristics previously discussed.

Solids removal
Used carwash water contains suspended solids of varying sizes. They must be removed. Some systems use centrifugal force to remove them. Some systems use bag filters and/or cartridges to remove solids. I prefer an automatic backwashing depth filter, similar to the ones you’ll find in swimming pools. With the right filtration media and proper pumping mechanics these systems operate flawlessly and automatically, potentially for decades.

In addition, reliable filtration media manufacturers and suppliers have their products tested, reviewed and listed under various standards by the National Sanitation Foundation (NSF).

Many of the “listed” media suppliers undergo rigorous testing to ensure that effectiveness and efficiency claims are reliable and substantiated. Ask your supplier how they determine their filter effectiveness. How about a particle count analysis from a certified laboratory? What you’re looking for is at least 20 micron particle size removal.

What’s next?
Okay, we’ve gotten rid of the solids, but what’s next? We still have a lot of stuff in the water that we need to address. First and foremost, you can’t reuse water that smells horribly. Nothing can drive customers away faster then having them gag from the horrible smell as they drive onto your lot.

Many odor control options are marketed but I’ve found that corona discharge ozone generators, properly sized and effectively deployed, are hands-down the most effective methodology for microbiological control. In addition, ozone’s free radical hydroxyl and highly effective oxidizing properties are superior to any comparable process for reducing organic compounds. If your system removes significant suspended solids particles, and successfully controls odor, you’re ready to move on.

The final rinse
If your water supply has high levels of total dissolved solids (TDS) there is only one practical option available if you want to offer a spot-free rinse as an option. It’s called RO. De-ionizing systems work too, but they aren’t very practical for this application. It’s easy to install and maintain an RO system provided that you’ve properly pretreated the supply water.

Some RO systems recover 50 percent of the feed water. This can be wasteful and expensive over time, especially in a high volume wash. Many systems are available that can recover up to 75 percent of the feed water supply. All thing being equal, we’d opt for one of these. You can send RO discharge to reclaim mitigating some of the wastes.

Making economic sense
Optimizing your water usage combined with proper pretreatment and recycling to the highest degree practical almost always makes economic sense. Producing a perfect product (a clean car) should be your highest priority. Properly treating your water makes this objective easier to accomplish, saves you money and also reduces the carwash industry’s overall impact on communities and the nation’s very finite and precious water resources.

It all comes down to you. Spend the time to define what’s in your water, assemble the specialized team of experts to evaluate the data and design the right system for your wash. The right decision will benefit your customers, your bottom line and the environment.

Robert Harvey is the director of engineering and support for Hydro Management Systems. Harvey is a chemical engineer with 29+ years experience with industrial water and wastewater. Harvey designed the AquaMizer® Water Recycling System and the AquaMizer® Water Conditioning Systems for Hydro Management Systems.

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