**This article was written by Charles Borchard and published in the March issue of Auto Laundry News. You can view it on their website here.**
With everything in life that you undertake there is a desired perfect outcome and abysmal failure of that outcome. There is an infinite number of degrees of successes and failures between those two extremes. The desired perfect outcome when we set out to wash a vehicle should be a clean, shiny, dry vehicle that not only looks newer but seems to run better than it did when you took it into your wash. The opposite end of that is a vehicle that burned to the ground while in your wash. As stated above, you have an infinite number of possibilities in between.
While I have a loud and uninformed opinion about nearly everything, I will stick to what I do know on this topic. Since I’m just the water guy, of all the things that contribute to the success or failure of the wash process, I am only qualified to comment on the water. For the things I know:
These are the three types of water used in vehicle washing:
1. Fresh water, i.e., tap water, either from a municipal water supply or private well, ranges in quality from great to terrible. Some of the symptoms of poor-quality tap water are high total dissolved solids (TDS) and either too high or too low of a pH reading. Simple tests conducted at the site by your car wash equipment representative will help with determining the quality of the fresh water. Water is an increasingly expensive commodity, and fresh-water use in a vehicle wash application should be carefully considered and applied as to maximize its value.
2. Spot-free water is water that either naturally or by processing has a total TDS count below20 parts per million (PPM). The overwhelming majority of spot-free systems in current use are reverse osmosis. RO systems have an impact on water conservation, as most equipment will require two gallons of fresh or tap water to make one gallon of product. However, there are ways to reuse this extra gallon of “reject” water. Talk to your car wash equipment representative about how to reuse that reject water.
3. Reclaim water is water that has been used in the wash process, then cleaned and reused. Many municipalities now require some form of reclamation or recycle system prior to permitting and having one may assist in avoiding expensive impact fees. Can’t I recycle all of it in a “closed loop?” For wash quality it is always better to have some fresh water in every cycle — 90 percent reclaimed water is for practical reasons about the highest usage recommended.
Let us discuss these three types of water in order:
1. Fresh Water
For the water guys, fresh water typically requires the least amount of equipment or work. However, if your site does not have adequate volume or pressure on your freshwater line you may require a holding tank and pump system to boost that water to make it usable for your application. Consult your car wash equipment representative about a booster system.
2. Spot-free Water
Most car wash equipment manufacturers have made provisions for spot-free rinse to be incorporated into their wash process and either offer or recommend this when building or updating a wash facility. A reverse osmosis system is a simple addition to any wash location and will increase customer satisfaction and create customer loyalty.
Many car wash equipment manufacturers now include a reverse osmosis system as standard equipment in their car wash packages — offering spot-free rinsing has become an integral part of the wash process. Regardless of the car-wash-equipment brand you select, there is a spot-free system for you, it is recommended to consult with your equipment distributor when selecting the proper spot-free system for your application. If you don’t have a distributor, your wash manufacturer will be able to assist you in the selection of the appropriate spot-free system.
How It Works
On the technical side, all RO systems work in much the same way. Tap water is introduced into a pump, which increases the pressure to 180-250 psi and forces water through the membrane(s). It is recommended to pre-treat tap water before it goes into the RO system. Some water conditions will require additional pre-treatment, so consult the equipment supplier. For the basics, a simple, activated charcoal filter tank works for the purpose of removing chlorine from your feed water. A pre-filter needs to be changed at least once per month; some water conditions may require more frequent changes. The most common size membrane used in car wash applications is 4”x 40”, which requires five gallons across the surface of the membrane for every gallon of product or permeate water produced. In years past, most operators would just send the four gallons of “bad” or concentrate water down the drain.
Today, water costs are expensive, and some locations are limited to how much water they can send to the sewer. Most, but not all, RO system manufacturers re-circulate a portion of that concentrate water back into the inlet stream. Out of the five gallons you start with, one gallon of product water goes into the RO storage tank, one gallon of concentrate or reject water goes to the drain, and three gallons are re-circulated. RO systems are typically sold by the amount of water they produce in a 24-hourperiod. This is usually at an optimum performance with 77° Fahrenheit feed water. Capturing and using the concentrate or reject water a second time in the wash is a good reclamation start.
Your equipment manufacturer will be able to tell you how much spot-free water you will need per wash and with some educated guessing you should be able to determine the size unit you will require. If your calculations are on the close side, upsize your storage tank or select the next unit size up.
3. Reclaim Water
All reclamation or recycling systems use a tank system to capture the water after it is used. These are often called clarifier tanks or oil water separator tanks. The suspended solids can settle in these tanks, thereby clarifying the water. If the tank system is properly sized not only will the solids settle to the bottom, the oils and lighter-than-water contaminants will rise to the top and become trapped out of the reuse stream. Suspended and dissolved solids in water are measured in microns. How big is a micron? The smallest particle that can be seen by the human eye is approximately 40 microns; the diameter of a human hair is 50 to 75 microns. Suspended solids 150 microns and larger, with a specific gravity (sg) of 1.2 will settle in 70° F still water at a rate of 0.8 inches per minute. Oil with an sg of .88 will rise at a slightly slower rate: 0.68 inches per minute. Specific gravity is the measurement of weight of material relative to water, water having a specific gravity of 1. Gold having an sg of 19.29 —nearly 20 times heavier than water — would settle very quickly. Colder water would slow these settling and raising processes. A diagram of a typical tank layout is shown at left.
After the tanking system, reclamation recycle systems split into two types; the first we will call a “batch system.” A batch system draws water from the end of the settling tanks and processes the water. This could be as simple as a cyclonic separator to as complex as systems that are essentially micro sewage treatment plants that treat the water with multiple filtering elements and/or media and store the water in additional tanks for future use in the wash process. These systems usually require multiple pumps. Once the water is processed and stored it can go septic very quickly, causing unpleasant odors when it is used unless it is being treated on an ongoing basis. This treatment is usually accomplished by a recirculation pump with some form of a biological, chemical, or ozone injection.
Biological systems are used quite often in municipal wastewater treatment and produce clean water, but it can be difficult to keep in balance, often requiring constant monitoring by water treatment engineers. In vehicle washing it is possible to get out of balance by introducing too much fresh water into the system. This can happen simply by hosing down the wash bay with fresh water. Chemical treatment with a disinfectant such as chlorine is also a fairly common practice in wastewater treatment; it also requires proper monitoring. If the dosing gets too high, chlorine, which is a powerful oxidizer, can cause premature corrosion and possibly failure of the wash equipment.
Ozone injection is another treatment used in wastewater treatment; it was first used in France in 1906. Ozone must be generated on site. The most common ozone generators use a high voltage arc and an oxygen concentrator. Ambient air is 21 percent oxygen, 78 percent nitrogen, and 1 percent inert substances. Pure oxygen is O2, meaning two oxygen atoms together. Oxygen concentrators take ambient air, compress it, dry and filter out the nitrogen and inert substances, and deliver to the ozone generator 70 percent to 90 percent pure O2. With this high level of oxygen being pushed through a glass tube, a high-voltage arc, like a spark plug, ignites and splits some of the O2 molecules, the free oxygen then attaches itself to other O2 molecules forming ozone: O3, meaning three oxygen atoms strung together. This ozone along with the O2 is then injected or drawn into the water stream and circulated into the tanking system.
Ozone is an extremely unstable molecule. When it strikes a biological or hydrocarbon contaminant in water it oxidizes that contaminant by shedding that spare oxygen atom. While ozone has an extremely high capability to oxidize, higher even than chlorine, the main advantage for the use of ozone is the short duration of its life; it will dissipate in 20 minutes as opposed to chlorine, which could have a harmful residual for several days. So if the introduction of ozone is controlled so as to contain it for its 20-minute life, it is a viable choice. Now that the water has been processed and stored, and is being treated on an ongoing basis, yet another pump is required when it is necessary to deliver water to the wash.
Batch systems require proper sizing to allow enough time for the processing of the water to be accomplished before the wash demand calls for the clean water, if the system is undersized you will be using water that is not as clean as it should be to make up the deficit.
We will call the second type of system “on demand.” With the same clarifier settling tank system, the on-demand system processes the water to the acceptable level of solids with some or all of the following: cyclonic separation, backwashing filters, media tanks, or disposable filters. This is accomplished as the wash demands water; it does not require additional holding tanks. At the very minimum, a reclaim system must remove the larger suspended solids. Cyclonic separation, depending on the separator, removes solids from a typical 70 microns down to 5 microns on the best systems. Media filtration, automatic back washing filters, and disposable bag filters are all in use on some demand systems as well. The better on-demand systems will also have the recycling capability to maintain odor control, using the same biological, chemical, or ozone-injection techniques. In most cases this requires a separate pump. Remember that this, in most cases, increases the size of the equipment package and the price as well.
MAKING A CHOICE
Equipment choices obviously offer a wide range of capabilities. There is also a wide range in pricing. Finding a reclaim system is like choosing every other piece of equipment in a vehicle wash. Ask yourself these questions: Is the equipment well made, will the manufacturer and distributor stand behind it and be able to fix it if it breaks, how much space will it require in the already crowded equipment room? Working with your equipment suppliers, and their distributors to answer these questions will go a long way to ensuring that you get the right system for your application.
There are many more questions and issues to consider regarding water usage in a car wash than the few that were touched on here. Your equipment supplier should have a good basic understanding of the use of water and can help guide you in your selections of equipment to make your wash a success.
When I started in the water treatment business in 1989 as a technician, servicing pressure washers and exchanging deionization tanks, I had no idea that this would become my life’s work. There have been a lot of changes: from the small regionally based four-person manufacturing, sales, and service business in a 2,000-square-foot warehouse that I joined then to the nearly 40 people in an acre-sized facility with national and international sales that I am a part of now. Fun fact: our combined annual sales for the first six years I was here is now what we ship in an average quarter.
The massive growth and expansion started in the mid 1990s with the addition of super salesman Gary Hirsh. Gary, who like me joined as an employee, really got us off the ground and ultimately became the majority owner, and president of the company. I was privileged to be Gary’s minority partner and provided hands-on leadership and support. When we sold out in early 2016, I was asked by the new owners to stay on in a general-manager capacity, which I have enjoyed for the last four years. My retirement date being 12/31/2020, this is likely the last article I will write for Auto Laundry News. Until that date, if you have any questions about this or any other article of mine you had read, please contact me at firstname.lastname@example.org.
Charles Borchard is the general manager for New Wave Industries, the manufacturer of PurClean Spot-free Rinse Systems and PurWater Water Recovery Systems and is in his 30th year in the water treatment business. He can be reached via e-mail at email@example.com if you have questions about this article.