If your industrial processes generate wastewater, then you need to know how to properly dispose of that wastewater. Process wastewater of any kind cannot simply be discharged into the sewer or outside where it can leave your property without first obtaining the proper permits. The most common options of disposing process wastewater include:
- Applying for a state or local wastewater permit to authorize the discharge of the wastewater to a Publicly Owned Treatment Works (POTW)
- Collecting the wastewater and shipping it off site for disposal (e.g., chemical waste management companies)
- Reusing the wastewater
- Collecting and evaporating the wastewater in evaporators or ponds
- Applying for a National Pollutant Discharge Elimination System (NPDES) discharge permit to authorize the discharge of wastewater into waters of the United States
Note: Only non-hazardous waste is discussed here. Additional requirements apply to facilities that generate hazardous waste.
Discharging to a POTW
Discharging wastewater to a POTW is most feasible for facilities that discharge large quantities of wastewater on a daily basis and cannot comply with the discharge limits of an NPDES permit. The POTW must be located close enough to your facility to be able to connect to their existing wastewater system or reasonably construct additional piping to connect to their existing wastewater system. To obtain authorization to discharge to a POTW, you must apply for a state or local wastewater permit. Once a permit is issued, you are required to regularly monitor the wastewater discharge and report your results to the governing authority. The steps to obtain a permit is as follows:
- Contact the city or county POTW and request to connect to their wastewater system. The POTW may request additional data including water demand, wastewater discharge quantities, and wastewater characteristics. This could be in the form of a questionnaire, a permit application, or other method depending on the POTW. If your facility is considered a significant industrial user, then the POTW may also require you to submit a permit application to the state.
- Facility’s classified as significant industrial users require pretreatment permits in order to discharge wastewater to a POTW. Pretreatment permits may be issued by the POTW directly or by the state, depending on the POTW. Your facility is considered a significant industrial user if you:
- Are an industrial user subject to the Categorical Pretreatment Standards in 40 CFR Subchapter N;
- Discharge an average of 25,000 gallons per day or more of process wastewater to the POTW;
- Contribute a process waste stream which makes up 5% or more of the POTW capacity; or
- Are designated by the control authority based on reasonable potential for adversely affecting the POTW’s operation or for violating a pretreatment standard.
- At this point, the POTW will evaluate the data to determine whether their existing infrastructure has enough capacity to serve your facility or if your facility’s wastewater characteristics meet their pollutant limits. If the POTW has enough capacity to serve your facility, and your facility’s wastewater characteristics are within their pollutant limits, then they may issue a wastewater permit, a letter of concurrence, or another form of agreement depending on the POTW. If your facility is considered a significant industrial user, the POTW may require a wastewater permit to be issued by the state.
- If the POTW determines that they do not have the capacity to serve your facility, then the POTW may require you to pay for upgrades to their existing infrastructure to meet your facility’s wastewater demands. If your facility’s wastewater characteristics exceed the POTW’s pollutant limits, then they may require you to pretreat your wastewater to acceptable levels before discharging to their system.
- In some cases, the POTW may just not be able to accept your facility’s wastewater discharge because of certain limitations (e.g., no capacity for expansions or upgrades; issues with high pollutant levels in their wastewater treatment plant; prohibited pollutants in your wastewater discharge; etc.). In these cases, you can try contacting a different POTW nearby and request to discharge your facility’s wastewater into their treatment system. If no POTW will accept your facility’s wastewater discharge, then you should evaluate the other disposal options previously discussed.
Collecting and Shipping Wastewater Off Site
Facilities have the option to collect their wastewater in containers (e.g., drums, totes, tanks, etc.) and have them transported to a facility that is permitted to treat wastewater. This is the simplest option that does not require any expensive installations, monitoring, or permitting, however, it is only feasible if you generate relatively small quantities of wastewater. Typical rates for wastewater collection are $0.30/gal–$0.40/gal but can be higher. This cost can quickly add up if you generate large quantities of wastewater on a daily basis.
Reusing Wastewater
Some facilities may find that their processes allow them to reuse their wastewater. This application is limited as most industrial processes require clean uncontaminated water. An example of wastewater reuse can be seen in facilities engaged in the wetting of logs. In this operation, logs are sprayed with water to keep them from drying out, and the spray water is collected and recirculated to be sprayed on the logs again. As long as this wastewater is not discharged from your facility, no monitoring or permitting is required.
Collecting and Evaporating Wastewater
Collecting and evaporating your facility’s wastewater is another option that does not require monitoring or permitting. This process can be accomplished either through natural evaporation in a pond or by using evaporators.
If you choose to evaporate the wastewater naturally in a pond, you must ensure that the pond is properly designed to have enough volume to contain the wastewater and precipitation without overflowing. The pond’s surface area should be maximized to allow for more evaporation than the inflow of water. Typical challenges to using an evaporation pond include having limited space on your property to accommodate a large pond and being in an area with high precipitation.
Evaporators use heat to evaporate wastewater, typically from burning natural gas or using steam from a boiler. This option requires lower capital costs compared to using an evaporation pond, however, there are ongoing energy costs. Facilities that already have an existing wood-waste boiler (e.g., burns sawdust, wood shavings, etc.) can use it to supply steam to the evaporators which can help reduce energy costs.
Applying for an NPDES Discharge Permit
Facilities can apply for a state NPDES discharge permit that allows them to discharge their wastewater from a point source (e.g., pipe, ditch, channel, etc.) off their property and eventually leads to waters of the United States (e.g., rivers, streams, lakes, etc.). Once an NPDES permit is issued by the state, you are required to regularly monitor the wastewater discharge and report your results to the state. Depending on the characteristics of the wastewater, it can be difficult to comply with the discharge limits specified in the NPDES permit. Pretreatment can be implemented to reduce the pollutant levels, but this can be costly depending on the pollutant and amount of reduction required.
Conversion Technology Inc. (CTI) has decades of experience in wastewater permitting and compliance with state and local agencies. If you believe your facility requires a wastewater or NPDES discharge permit or would like assistance evaluating wastewater disposal options, CTI would be happy to assist in the process. For more information, please contact us at (770) 263-6330 or cti@conversiontechnology.com.