Auto Laundry News - March 2013

Water Reclaim — How to Pick a System for Your Car Wash

By Charles Borchard

Before we get to pick a water reclamation system, let’s review some of the water basics. For vehicle washing, water is the primary means of rinsing the dirt, road grime, salt, and snow off the surface of the vehicle during the wash process. All soaps use water as the delivery medium from the chemical station out to the vehicle to assist in breaking up those contaminants. The higher the quality of water you use, the higher the quality wash you will deliver.

WATER TYPES

There are three types of water used in vehicle washing:

1. Fresh water. 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 so as to maximize its value.

2. Spot-free water. This is water that either naturally or by processing has a TDS count below 20 parts per million (PPM). The overwhelming majority of spot-free systems in current use are reverse-osmosis based. 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. 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. This 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. Having one may assist in avoiding expensive impact fees. While it is possible to recycle all water used in a “closed-loop system,” it is always better for wash quality to have some fresh water in every cycle — 90 percent is, for practical reasons, about the highest usage recommended.

TANKS

All reclamation or recycling systems use a tank arrangement to capture the water after it is used. These are often called clarifier tanks or oil/water separator tanks. The suspended solids are allowed to 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 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 a 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. Left is a diagram of a typical tank layout.

SELECTION PARAMETERS

There are a few different parameters for selecting a water reclamation system for your wash. These parameters are the same no matter which type, style, or brand of wash you are using. Each type of wash has different answers. The following Q and A is organized by format:

IN-BAY AUTOMATIC — FRICTION

1. How many total gallons will you need to wash each vehicle?
This will depend: some sites will have multiple wash options and each will use different amounts of water. For this exercise, the top wash package is the one you want to use to do your calculations, so for this one the answer is 50 gallons.

2. How are you planning to use the recycled water?
This example has a low-pressure undercarriage rinse, foam-friction side-wrap components, and either a top brush (also foam friction) or a cloth mitter. All of which can be used with recycled water

3. How many of the total gallons needed can be recycled water, and how many needs to be fresh water?
Total water usage is 50 gallons. For wash quality, some of the wash functions need to be either fresh or spot-free water — six gallons fresh water for the drying-agent-rinse pass, six gallons for the spot-free final-rinse pass, two gallons fresh water to mix with the concentrated soap, which leaves 36 gallons that can be recycled water.

4. How long is the wash cycle?
This will depend: just as in the answer to question #1, you want to use the top wash package. What you are doing here is determining what the maximum gallons-per-minute (gpm) demand is going to be. So, in this example, you have a low-pressure undercarriage rinse, using about four gallons per vehicle with an average run time of 30 seconds — therefore, eight gpm. Two 45-second side-wrap and top-brush or mitter curtain passes use a total of 28 gallons per vehicle, 14 gallons per pass. Since in this application you won’t have the undercarriage running at the same time as the wash pass, your 14 gallons used in 45 seconds is the peak demand, which is 18.66 gpm.

With the answers to these four questions, we have determined that the reclaim clarifier tanks need to be 1,500 gallons total, with preferably three or four compartments, and that the water recycling system needs to be able to deliver up to 20 gpm of 70-micron quality water on demand. The reclaim clarifiers should always be 1,500 gallons and three or four compartments minimum like in the figure on page 22. The low-pressure nature of the wash system allows the use of lower-quality recycled water, though, as we covered in the basics, the higher the quality of water you use the better the quality of wash you will deliver. A 70-micron system is the low end and may or may not have a recirculation function or add on odor control like ozone injection.

IN-BAY AUTOMATIC — TOUCHLESS

1. How many total gallons will you need to wash each vehicle?
As with the friction in-bay automatic, we’ll use the top wash package for this exercise, so the answer is 75 gallons.

2. How are you planning to use the recycled water?
This example has a high-pressure undercarriage rinse, and two high-pressure passes, all of which can be used with recycled water.

3. How many of the total gallons needed can be recycled water, and how many needs to be fresh water?
Total water usage is 75 gallons. As for the friction in-bay automatic, some of the wash functions need to be either fresh or spot-free water to assure wash quality: six gallons fresh water for the drying-agent rinse pass, six gallons for the spot-free final-rinse pass, four gallons fresh water to mix with the two-step high- and low-pH concentrated soap, which leaves 59 gallons that can be recycled water.

4. How long is the wash cycle?
The high-pressure pump is rated for 36 gpm, but the undercarriage arch and the wheel spinners are only tipped for 16 gpm so you are using about eight gallons per vehicle at an average run time of 30 seconds. The same 36-gpm pump through the gantry or inverted L manifold, which is tipped for 28 gpm: two 55-second high-pressure rinses at 25.5 gallons per pass. Since in this application you won’t have the undercarriage running at the same time as the wash pass, your 25.5 gallons used in 55 seconds is the peak demand, which is 28 gpm.

The water recycling system for this example needs to be able to deliver up to 30 gpm of 5-micron-quality water on demand. With high-pressure pumps boosting to 600 to 1,200 psi, the tolerances within these pumps are pretty fine so most manufacturers of these pumps require 5-micron-quality recycled water. With the maximum flow demand of 30 gpm and 50 minutes settling time in this example, we are right up against the minimum for the 1,500-gallon reclaim clarifiers. When you pressurize water to the 600 to 1,200 psi range, the atomization of the water magnifies the odor. In this application, a 5-micron system must therefore, at a minimum, have a recirculation function. In addition, an odor-control system like ozone injection is highly recommended.

EXTERIOR TUNNEL

1. How many total gallons will you need to wash each vehicle?
In the previous two examples, this information was readily available. The wash equipment manufacturers had already done the math. For the exterior tunnel, the manufacturer should be able to tell you how much water per minute each piece of wash equipment will use. The cars-per-hour conveyor speed will tell us how long each piece will be on. Totaling all the equipment, we come to a 180 gpm demand. We are running 120 cars per hour, so each device is on an average 30 seconds. As with the other two examples, we’ll go for the top package in this case — 95 gallons per vehicle.

2. How are you planning to use the recycled water?
High-pressure undercarriage rinse, high side washers, low side washers, two mitters (one front-to-back, one side-to-side), high-pressure wheel washers, side blasters, and top blaster.

3. How many of the total gallons needed can be recycled water, and how many needs to be fresh water?
This site has four rinse arches. Though everyone gets the six gallons of spot-free rinse, you would only get two of the other three rinses, depending on the package, for an additional 12 gallons of fresh water. There are 14 soap applications total, using eight gallons of fresh water per vehicle to mix with the concentrate. Therefore, total fresh/spot-free demand is 26 gallons per vehicle, leaving 69 gallons that can be recycled water.

4. How long is the wash cycle?
This one is the easiest: 69 gallons of recycled wash water delivered per vehicle in 30 seconds of run time means we need a peak delivery capability of 138 gpm, because, unlike the other two types, everything could be on at once here.

The water recycling system for this example needs to be able to deliver up to 160 GPM of 5-micron-quality water on demand. With as many high-pressure pumps as this example has, you would require 5-micron-quality of recycled water. With the maximum flow demand of 190 gpm, allowing for both the recycled and fresh water, and 50 minutes settling time in this example, you could use up to 9,000 gallons of clarifiers. In most cases, you would not need to use more than 6,000 gallons for this application, as you rarely run flat out full time, and the solids will settle. Wash applications that wash cars with a heavy dirt loading may want to consider larger tanking. This example requires recirculation and ozone.

Charles Borchard is the vice president of operations for New Wave Industries, the manufacturer of PurClean Spot-free Rinse Systems and PurWater Water Recovery Systems. This is his 23rd year in the water treatment business. He can be reached via e-mail at cborchard@purclean.com if you have questions about this article.

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