Any of you who have managed to slog through any one of the more than 40 articles I have written in the last 15-16 years already know that at some point I am going to tell you about the three types of water used in vehicle washing. You can skip down past the next three paragraphs. For the few of you reading my prose for the first time, you are why I include these three paragraphs to help you understand the importance of water in the vehicle washing process.
TYPES OF WATER
These are the 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 characteristics of poor quality tap water include 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 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. 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, however, 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
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 reclaim water is for practical reasons about the highest usage recommended.
Chemistry in car washing can be a complex assortment of products, with long complicated names. Dodecylbenzene Sulfonic Acid is one example. Dodecylbenzene
Sulfonic Acid, or DDBSA, is an anionic surfactant. Anionic means it is a negatively charged ion. A surface active agent, shortened to surfactant, is a substance, such as a detergent, that can reduce the surface tension of a liquid and thus allow it to foam or penetrate solids; a wetting agent. Being negatively charged, it will usually not want to stick to the vehicle surface.
It is a very common product used in multiple cleaning solutions both at the consumer level and for our purposes of washing vehicles. For vehicle washing it is used with both acid and alkaline products. For cleaning wheels, a low-pH, acidic product is mixed with the DDBSA, this helps descale and clean the wheel surfaces. After the acid breaks the wheel crud loose the surfactant gathers that dirt up and keeps it from redepositing on the surface. A high-pH product, alkaline, in a vehicle detergent will break up organic soils, fats, oils, and proteins. In this application the DDBSA serves the same purpose with regard to gathering up that unwanted material and carrying it away.
At the other end of the wash, waxes are applied as the clean car is being finished. Quaternary Ammonium Compounds, or Quats are a positively charged surfactant applied with a sealer, silicone, or mineral seal oils, MSO, for example. Because the quats are positively charged, this helps bind the sealing agents to the vehicle. I could continue to stumble my way through the chemistry used in vehicle washing but I think these two examples will serve my purpose here. If you need additional chemical training please discuss with your chemistry supplier.
THE RECLAIM CONNECTION
How or what does any of this have to do with reclaiming my wash water? Well I’m glad you asked. If your wash equipment and chemistry on the cleaning end of the wash are doing their job, all the dirt, cleaning agents, and negative surfactants are in the reclaim water. At the finish end, ideally the sealers and the positive surfactants would all be on the vehicle. Alas that is not the case. To make sure enough wax gets to stay on the vehicle, excess waxes are applied. This results in some of the wax and positive surfactants ending up in the reclaim water. This is not an immediate cause for alarm. Everything has a balance, including the water in the reclaim tanks. If this balance gets too far to one end, for instance if there are enough of the waxes and positive surfactants mixing with the negative surfactants, the dirt that is trapped in the negative surfactants will create long-chain polymers. If this gets severe enough, it can result in the system being unable to draw water through the strainer basket, and the reclaim will shut down.
Reclaim tank setup.
There are multiple other ways wash chemistry can negatively impact your reclaim system. If you use too much acid in the front end of the wash, for example, and your pH gets too low, you can get a horrible rotten egg smell or, at the extreme end, it could smell like a tire fire. It doesn’t have to be as acidic as to cause the bad odor, but if it is acidic enough you can promote biological growth and end up with a bio slime clogging your reclaim strainer with the same net result: the reclaim system shuts down. Too much alkaline cleaners can raise the pH to above the 9, which is what most sewer authorities consider the highest safe level to discharge. This may also impact your ability to get a clean car.
Over time, reclaim tanking will fill up with dirt and will need to be pumped out (see graphic above). Before it fills up with dirt, there will probably be too much chemistry in the water, and you would end up with an out of balance condition like the ones listed above. There are places where they pump out your tanks and then put the water back. If you are using a reclaim system, you really want them to haul off that pumped out water too.
My thanks to Wikipedia and www.dictionary.com for the definitions and correct spelling on some of the ingredients in common use in car wash chemistry.
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 29th year in the water treatment business. He can be reached via e-mail at email@example.com if you have questions about this article. He will also be at most of the regional car wash shows this year as well as presenting at The Car Wash Show in Nashville, TN.