Water Reclamation � Faqs Based On Misinformation

Thursday, November 09, 2006

Few equipment packages can, by mere presence or absence, affect the fortunes of a car wash operation more profoundly than a water reclaim system. By its absence, under drought conditions, it could threaten the car wash with closure. By its presence, it could save the car wash a stack of money in impact fees and provide ongoing savings in reduced water and sewer bills. Still, many questions remain about how these systems work and about their efficacy. Reusing wash water, is that a new idea? How does it work? Water reclamation or recycling in vehicle washing is not a new idea. With the ever-increasing cost of water usage and sewer disposal � or threats from politicians to close car washes when drought conditions occur � it is something that should, however, be considered in any new wash or remodel. Reclaim water is the re-use of water that has already been used in the wash and recovered via the drain system. Most drain systems consist of a catch basin to settle out the large solids, followed by a two- or three-compartment underground settling tank to remove oil and grease, floatable materials, and settleable solids. Treated water from this reclaim tank is then discharged to sewer usually through a city-mandated oil/water separator. A properly-designed reclaim system must both remove solids and provide biological/odor control, removal of the solids to prevent plugging and limit erosion in high-pressure-pump equipment, and odor control because if the water stinks, no one will use it.

I will just put in a "junk pump" and turn it off after the city signs off on it.

That will work, won't it? Not many years ago, some municipalities started to require water reclaim systems for vehicle washes. To be issued a permit, you needed to show intent that you were going to recycle water. The regulations were fairly loose, and systems were designed to be inexpensive � and in many cases were installed and never used. There is an old story of an operator who purchased a reclaim system for a new wash he built. He then moved it from site to site as he was building more washes. Finally, an inspector told him he could not sign off on that same sad-looking piece of equipment for the sixth time. It is a great story! The truthfulness may be suspect, but it is indicative of both the wash industry's approach to satisfying a regulation and the equipment manufacturers' willingness to satisfy the demand. Municipalities wised up and started to put performance requirements in the regulations. You had to show that you were reducing your water usage. It became necessary to use these reclaim systems � often with unsatisfactory results. Just getting past the permit stage is not the only problem, some locals are now charging so much for water and sewer that to not have a reclaim system is cost prohibitive. Ah man! All reclaim water stinks, doesn't it? No one wants to live near a sewer plant. The water is foul and if the wind is blowing in, the odors will force you to your knees. But for water to be reused, certain steps have to be taken to clean it up. The first major treatment in wastewater is sedimentation � the removal of a substantial amount of suspended matter. This is done in settling ponds in a municipal system. In a car wash system the settling tanks are usually underground.

In the municipal system, the water can set for days or even weeks to allow the solids heavier than water to settle to the bottom. If your incoming stream of water contains lighter-than-water material, floating trash or hydrocarbon-based oils, these products will float on the surface of the settling pond. In a car wash system, the total amount of water kept in the system is considerably less than what is kept in the sewage system of a city, and naturally will have less time to settle before it is called on to be used again. Suspended solids with a specific gravity (sg) of 1.2 � solids 20 percent heavier than water � will settle in 70-degree water at a rate of 0.8 inches per minute. So if your tank is 60" deep with a water level of 48", 1.2 sg solids introduced at the front of the tank will settle to the bottom of the tank in 60 minutes.

Here's how to plan a tank layout for an in-bay automatic operation, for example. If you intend to use 30 gallons per minute (gpm) from your reclaim, you would multiply the 30 gpm with the 60 minutes (required to allow the solids to settle) for an answer � that is, a minimum �of 1,800 gallons in tank(s) underground. If, however, you are using 90 gpm from the reclaim in a tunnel application, you will need closer to 5,400 gallons of tanking.

In the diagram below, you will notice walls within the tanks themselves. These will help trap the solids below the transfer point between tank sections. With the transfer point below the surface, these walls will also trap the oils at the top � giving you the best possible dirty water to work with.

So all I need is a tank set-up? Well, no! Once you have trapped the large solids and oils underground, it is time to re-use the water. Reclaim water from the settling tank contains solids that have not settled within the tank. These solids are typically small in size (less than 150 microns) and consist of sand, clay, and silt. These solids can increase wear on pumps, piping, and nozzles, and increase the potential of plugging nozzles. To get the water out of the tank, you will need a suction line and a pump station. The very basic systems would just spray this water out to the wash and, because of the solids still in the water, foul tips very quickly. Ideally you will need to have at the very minimum a reclaim system that removes the larger suspended solids. Cyclonic separation, depending on the separator, removes from a typical 70 microns down to 5 microns on the best systems. Now you are reclaiming water.

Wait, what about the smell? Reclaim water is also is a great environment for growing bacteria which can cause plugging and create odor problems. Standing water, specifically standing water with a high dirt and chemical loading, will go septic in less than an hour. Once it has done that, it will stink. If you provide some form of recirculation � so that the water stays moving, at 15-18 gallons per minute for example � you will help keep the odor down. In the diagram you will note the recirculation does not include the first settling tank. You want to allow that tank maximum settling to trap the solids and not stir up the oil on the top of the water.

Okay, so I'm reusing the water, I'm recirculating it � that's it, right? A properly-designed reclaim system must both remove solids and provide biological/odor control. Typically, anaerobic bacteria (bacteria that grow in the absence of oxygen) will grow beneath the settled solids in the reclaim water tank. This type of bacteria produces hydrogen sulfide and methane, which produces an odor similar to rotten eggs. Aeration � the forcing of air into the water � will benefit the operator. The aerated water will add oxygen to the tank water, which will control the anaerobic bacteria growth. A second method of odor control is to periodically add an enzyme that consumes the organic material in the reclaim water, which is used as a food source by the bacteria. Without a food source, the bacteria cannot survive and multiply. The enzyme is fed into the recirculation water using a small feed pump that draws from a small feed tank. The feed tank is periodically filled with concentrated enzyme and city water. The recirculation water with enzyme goes through an aerator in the reclaim tank to provide aeration and better biological/odor control.

The third method utilizes ozone to kill the bacteria. Ozone is a contact killing agent, similar to chlorine used in city water. Ozone (O3) is generated by concentrating the oxygen (O2) in ambient air and passing the concentrated oxygen through a high-voltage electric current to produce ozone. The ozone-laden gas is then educted into the reclaim tank � via the recirculation water stream � to kill the bacteria.

Okay, now I get it, but where do I go to find a reclaim system that will work for me? There is a wide range of systems available � with an equally wide range of capabilities and pricing. Finding a reclaim system is like finding any other piece of equipment in a vehicle wash. Ask yourself these questions: Is the equipment well made? Will the manufacturer/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 distributor(s) to answer these questions will go a long way to ensuring that you get the right system for your application.

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