Industrial wastewater varies dependent on the factory in question and what the water is being used to clean or lubricate during the manufacturing process. Some facilities wash machine parts to remove oil, resulting in an oily wastewater. Other manufacturers commingle water of various uses. For example, dirt and oil from mop water, metal fines and dissolved metals from tumbler wastewater, and etching overflow that alters the water’s pH.
A water treatment engineer charged with solving a wastewater problem starts with two main considerations. Contaminates are the first variable; the second is the quantity of wastewater being generated, which is dependent on the overall size of the factory, the nature of the product being manufactured and how the water is being applied. The first step any manufacturer should take is to consider if there are any ways to reduce the amount of water used. In some cases, this can be achieved simply by sweeping a floor before washing, which would remove much of the waste when dry and reduce the amount of time needed to wash the floor. A good example is using an air hose on soil buildup prior to washing down a backhoe prior to repair. Since the Clean Water Act of 1972, many technologies and products have been invented to help clean polluted water, so manufacturers now have a wide variety of tools at their disposal. However, just because it is technically possible to filter water so it can meet sewer discharge standards, that may not be the best choice for the manufacturer.
A wastewater evaporator is a good option when a facility is handling 5 to 50 gallons per hour, which is the capacity of most wastewater evaporator models, while manufacturers offer some larger models. Therefore, as a general rule, if your facility is producing a large volume of wastewater, an evaporator will not work as your sole wastewater strategy; however, it may be part of a solution. For example, if you have a waste stream of 350 gph of emulsified oil, you could install an Ultrafiltration unit to filter 90% of the water and generate a concentrate of 35 gph, which could be sent to a 35 gph capacity wastewater evaporator. Most wastewater evaporators could then evaporate 90% of that water and leave all the contaminants in the last 10% for a waste hauler. Some evaporators offer a RunDryTM technology that can boil off all the water and leave only the pollutants for disposal.
It is important to remember that even though the volume variable is within range, evaporation may not be the right choice. If there is only one easily filterable contaminant, it may make more sense to filter the water for discharge than evaporating it. For example, if free oil is the only contaminant, it would be less expensive to install a pump and an oil-water separator than it would to install an evaporator. However, if a factory generates 5 to 50 gallons of wastewater per hour with more than one contaminant, a wastewater evaporator would be warranted. In that scenario, many manufacturers pay a waste hauler to take the water away, but the price for hauling will vary based on the facility’s location and the contaminants involved, but it is likely to be between $1.00 to $2.00 per gallon. A small electric wastewater evaporator usually operates at $0.25 per gallon, and the slightly larger gas units run at $0.08 per gallon.
If you are in charge of operating costs at your facility, take a few minutes to examine the content and contamination levels of your wastewater. You may be unnecessarily paying for a wastehauler to take away your water because that is the way it has always been done. Consider evaporating as an alternative. One business owner who recently installed an evaporator told me that every time he sees the steam exhaust he thinks of it as green because of all the money it is saving him!
David N. Lyman, president of RunDry EvaporatorsTM, is a mechanical engineer with 40 years of industrial experience.