On the Lookout

Paying attention to often ignored wastewater sources, such as cooling towers, can help your facility stay in compliance

• By Paul C. Simonetta
• Jun 01, 2007

Many facility environmental managers believe that their wastewater compliance requirements are properly managed when discharges from “production-related operations and equipment” are permitted. However, other discharge sources, such as building- or facility-related utilities that provide support to company operations, may require permitting or be subject to other regulatory requirements. Some examples of wastewater sources that routinely are overlooked include water treatment systems (water softeners), air conditioning/cooling systems, air compressors, sprinkler systems, etc.

While auditing or inspecting facilities, it is common to find company managers, and even some environmental professionals, surprised to learn these sources are regulated. In addition, regulatory agencies, such as the U.S. Environmental Protection Agency (EPA), state environmental agencies, and inspectors appear to be giving these sources closer attention as they develop new regulations and complete facility reviews. Although most of these wastewater sources typically are not significant pollution sources, they can result in exposure to fines and other regulatory action if not properly managed and documented.

The information provided below identifies wastewater discharges from utilities that are often overlooked and the associated materials released from them considered to be potential pollutants. The article also includes a suggested strategy to identify applicable regulations or permits, options available for disposal and recommendations for monitoring these discharges.

Equipment and Associated Discharges
Water Treatment Systems
Water treatment systems or “water softeners” typically are used by companies to remove “hardness” present in the form of metal ions (calcium, magnesium, etc.) from water supplied from wells or a water supply company. The systems remove the metal ions by ion exchange using either a resin media or brine solution. The reason for removing these ions may be to prevent operating equipment, such as boilers or plumbing, from accumulating these metal ions, which can cause problems. In addition, companies may need cleaner water for production purposes. Regardless of the purpose, these systems need to be routinely recharged and/or backflushed generating wastewater with potentially high concentrations of metal ions.

Air Conditioning/ Cooling Systems
Many commercial and industrial air conditioning and cooling systems use water as a media to transfer cooling capacity. Water may be circulated through one or more chillers (equipment containing refrigerants and heat exchangers) to lower its temperature before being introduced into coils for air-conditioning. After having its temperature raised following its intended use, the water then may be circulated through cooling towers to dissipate the accumulated heat. These systems may or may not be closed-loop. Regardless of the type of system, water should not come in direct contact with other equipment fluids such as refrigerants, oils, and lubricants.

However, this water is routinely treated with chemicals (e.g. biocides and scale inhibitors) to minimize bacterial growth or mineral deposits on equipment. A good management practice is to re-circulate and reuse the water until it can no longer be used. Even though the water may be reused for a period of time, eventually it will need to be replaced to accomplish its intended purpose and to prevent damage to operating equipment. Water containing these chemicals may be released from these systems in small volumes daily. For example, cooling towers usually require some routine process in which water, also known as “blowdown,” is released in order to remove solids that become concentrated from minerals in the water. Larger volumes of this water may be released to purge all or portions of these systems during annual or semiannual maintenance activities. As such, wastewater from these systems may contain treatment chemicals as well as metals.

Equipment Condensate
Condensate collected from operating equipment, such as air compressors and air conditioners, usually contains some concentration of oils, lubricants, and/or coolants. Most compressors and air conditioners need oil or other lubricants to function properly. Other fluids, such as coolants, may be used as refrigerants or in heat exchangers to accomplish the purpose of the equipment. These fluids, when present on the surface of equipment from leaks, drips, etc., will mix with condensation from the air. The volume of condensate wastewater generated from equipment is dependent on the size of the equipment and the atmospheric conditions (i.e. moisture content in the air) in the vicinity of the equipment.
Another source of condensate wastewater is from dryers used to treat compressed air. Air dryers are designed to remove moisture naturally present in the air from supplied compressed air. Air produced in compressors that is not dried could damage to operating equipment. The water removed in an air dryer may also be in contact with oil, coolants, and lubricants, depending on the type of systems used to dry the air. Wastewater generated from air dryers is likely to be similar in characteristics to condensate that is collected from equipment surfaces as described above.

Sprinkler Systems Test Water
Sprinkler systems in most buildings require routine testing to ensure proper operation. Water may remain in these systems to keep these systems charged as a normal operating condition. As such, water generated from testing and flushing these systems may contain suspended metals from piping, and microorganisms, such as bacteria, from stagnant water. Although water is not routinely removed from these systems, a significant volume of wastewater may be generated when they are tested or flushed.

Boiler Blowdown
Commercial and industrial boilers are often thought to solely impact the environment as fuel burning sources affecting air quality. However, wastewater generated from boiler systems, commonly referred to as “boiler blowdown,” is routinely released or discharged from these systems to sanitary sewer systems, septic systems, storm drains, or other waterways.

Periodically rinsing out the boilers helps limit the buildup of contaminants that may degrade boiler performance. Two types of pollutants can be present in boiler blowdown: chemicals added to treat the water entering the boiler (e.g. scale and corrosion inhibitors) and solids containing metals that accumulate within the boiler itself. In addition, due to its high temperature, thermal impacts may be a concern when discharging blowdown to surface water systems if the blowdown has not been commingled with other water to lower its temperature. The concern is that the high temperatures of boiler blowdown could harm the surface water systems.

Meeting Regulatory Requirements
Individuals responsible for the discharges described above should consider developing a compliance strategy to ensure these sources are not ignored. The first step involves developing an inventory of potentially regulated sources, including the approximate discharge volume and frequency of discharge. While completing the inventory, the receiving systems (e.g. a sanitary sewer or a storm sewer) should be investigated to identify where the discharge is being directed.

With an inventory completed, the next step is to determine whether regulatory permitting is required. If permits are necessary, they should be obtained and complied with. If permits are not needed, other regulatory obligations, such as monitoring, may be necessary to demonstrate compliance with non-permit-related requirements. For example, when discharges are directed to a municipal sanitary sewer system, also known as a publicly owned treatment works (POTW), prohibitions may be established in a local sewer ordinance against discharges containing certain concentrations of pollutants (e.g. copper greater than 5 parts per million).

Depending on the physical location of the wastewater sources, options for wastewater disposal may include the following: POTWs, surface water systems, groundwater (septic or well injection), or collection for off-site disposal at a treatment plant. Surface water discharges from these sources likely would be regulated as industrial discharge sources and may be subject to National Pollutant Discharge Elimination System (NPDES) permitting. Discharges to on-site septic systems or groundwater also may be regulated and limited. Most of the discharges from the sources mentioned above probably could be discharged to a POTW, where available. However, POTWs are not always available. Or, POTWs may not accept water treated with certain chemicals, such as biocides, that could impact organisms (bacteria) that assist in the proper function of the treatment plant. If unable to discharge to a POTW for any of these reasons or discharges to surface/groundwater are prohibited, discharges may need to be redirected and collected for off-site disposal. Similarly, where complex permitting may be necessary to discharge small volumes of water to surface or groundwater, collection for off-site disposal may also prove to be the most economically feasible option.

After having determined the regulatory requirements and available discharge options, the facility’s environmental manager should develop a monitoring program. Permits for these types of sources typically include at least annual monitoring. When permits are not present and indirect limits have been established, such as local sewer ordinances for POTWs, a monitoring frequency likely will not be present. Although a set frequency requirement may not be included in a local ordinance, it is recommended that sampling be completed at least annually to comply with the specified conditions. In instances where wastewater is collected and shipped for off-site disposal, a waste profile should be developed based on laboratory analysis of the discharge. Unless specified by state or local requirements, the waste profile would probably not need to be updated on a certain frequency unless a change occurred in the discharge.

Summary
A number of wastewater discharge sources related to building utilities are often overlooked. It is recommended that individuals responsible for environmental compliance at facilities with these sources identify applicable regulations and develop programs to ensure compliance. Although these sources are not typically thought to be significant pollution sources, there appears to be increasing scrutiny of these sources by regulatory agencies and inspectors.

This article originally appeared in the 06/01/2007 issue of Environmental Protection.