Staying in compliance and ensuring the proper management of wastewater discharges from industrial facilities can be challenging. The possible impediments that a facility can face are dependent on several factors such as the location of the facility, existing infrastructure, and the facility’s financial forecast. One of the most important first steps to maintaining wastewater compliance involves properly identifying the different wastewater streams at a facility. Wastewater discharges generally fall into one of two categories, Domestic and Industrial. Domestic wastewater discharges come from bathrooms, kitchens, and hand-washing stations and can be characterized as wastewater from personal usage. Industrial wastewater discharges come from industrial and commercial sources and may contain pollutants at levels that could impact water quality and/or interfere with Publicly Owned Treatment Works (POTW). Industrial discharges are usually generated from different types of industrial processes and are typically segregated from domestic discharges as described above.
Regardless of how “clean” a wastewater discharge seems, if it was generated from an industrial process, it is considered industrial wastewater and should be handled as such. An in-depth facility inspection and interviews with employees familiar with the facility’s industrial processes should be conducted in order to identify potential sources of industrial wastewater discharges from the facility. Once the industrial discharges have been identified, industrial wastewater can be managed using one of the following options:
- Recycle and Reuse
- Discharge to Publicly Owned Treatment Works (POTW)
- Discharge to the Waters of the State
- Land Application
There are also more uncommon methods for the management of wastewater such as underground injection. More rarely used methods will not be addressed in this article.
Recycle and Reuse:
If there is any practical way for a facility to recycle and reuse the wastewater in another industrial process without negatively impacting the quality of products or equipment, it should do so. Not only does this reduce environmental liability, but it also happens to be the least expensive option and requires no permitting considerations. This method eliminates the necessity of maintaining compliance with strict regulatory limits that can be required through permitting. One example of this method can be found in the lumber industry. Lumber facilities typically dry wood in large industrial kilns that generate kiln condensate. This kiln condensate cannot be discharged directly to the environment and must be managed in another way. Commonly, lumber facilities will pump the kiln condensate to a wet decking operation onsite. Wet decking operations involve the consistent wetting of logs to slow deterioration. Any discharge from wet decking is then collected in a retention pond. The lumber facility would only need to ensure that the wet deck retention pond never overflows.
Discharge to Publicly Owned Treatment Works (POTW):
For facilities that have an existing sewer connection or facilities that can feasibly tap into a sewer line, discharge to a POTW could be a relatively simple and inexpensive solution. This would be the preferable choice for facilities that cannot recycle or reuse their industrial wastewater. The facility will need to ensure that their wastewater discharge meets the city or county POTW’s pollutant discharge limits. These limits are in place to ensure that operational issues are prevented at wastewater treatment facilities. In some cases, meeting these limits will require the facility to obtain a permit and/or pretreat the wastewater prior to discharge. Additionally, facilities that are not connected to a sewer system can transport the wastewater to a POTW although the cost to transport wastewater can be prohibitively expensive. The facility transporting wastewater will be held to the same pollutant discharge limits as the facility discharging directly to the sewer.
Discharge to Waters of the State:
“Waters of the United States” are defined as territorial seas and waters which are currently used, historically used, or may be susceptible to use in interstate or foreign commerce. These waters also include tributaries, lakes, ponds, impoundments, and adjacent wetlands (40 CFR Part 328).
Any point source that discharges or intends to discharge to Waters of the State must obtain a National Pollutant Discharge Elimination System (NPDES) permit. A “point source” is defined as any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, concentrated animal feeding operation, or well.
In order to obtain a NPDES permit the facility will need to submit a permit application. The application will be reviewed by the state, and the state will develop effluent limits based on the details listed in the application. These limits are oftentimes lower than those of a POTW. A draft permit will then be issued on public notice for a minimum of 30 days, and a public hearing will be held if there is significant public interest. After this public comment period and response to comments, the permit will be issued. Upon receipt of the permit, the facility will have to meet the following conditions:
- Submittal of a Permit Reapplication every 5 years or more frequently if designated in the permit
- Maintaining Wastewater Operator Certifications
- Management of a Pretreatment Program to meet effluent limits
- Conducting Monthly Sampling of the Wastewater Discharge
- Submittal of Monitoring Reports to prove effluent limits of the Permit are being met due to stricter pollutant discharge limits and the additional permitting requirements, facilities often apply for an NPDES Permit when reuse of wastewater and discharge to a POTW are not feasible.
Evaporation occurs in the following ways:
- Natural Evaporation
- Thermal Evaporation
- Mechanical Evaporation
Natural evaporation is the process where a liquid (typically water, but wastewater in the context of this article) vaporizes at surface level as it changes to the gas phase. Depending on natural evaporation from pond storage for example, is not practical because it requires an extremely large surface area to evaporate a relatively small quantity of wastewater.
Thermal Evaporation is the same process as defined above with the exception that heat is applied to the process to increase the evaporative rate of the wastewater. One example of this would be the use of natural gas evaporators in order to evaporate the kiln condensate resulting from the drying of lumber. This process is typically very expensive as it requires the purchase and maintenance of evaporative equipment and a source of fuel to operate the equipment.
Mechanical Evaporation uses the capabilities of natural evaporation and increases the evaporative rate by pumping the wastewater through atomizers. This atomization process creates droplets which more readily vaporize. This option requires a facility to have a dedicated pond to store wastewater and to purchase mechanical evaporation equipment. When compared with the other options, this option is relatively inexpensive.
Land Application System:
Land Application means the spraying of wastewater on the land surface. Any facility that land applies or intends to land apply wastewater via a Land Application System (LAS) must obtain an LAS Permit from the state. An LAS requires a large acreage of land (depending on the amount of wastewater generation rate). An LAS also requires relatively expensive pretreatment, monthly sampling, and submittal of discharge monitoring reports to satisfy the permit conditions. Of all of the available permitting options, an LAS Permit is typically the least attractive as it carries some of the highest of amount of sampling constituents, requirements, and frequencies.
Preferential Priority of Disposal Methods:
The following is the recommended method for disposal of wastewater by order of preferential priority based on cost and associated regulatory burden:
- Recycle and Reuse
- Discharge to POTW
- Mechanical Evaporation
- Land Application System
Conversion Technology Inc. (CTI) has decades of experience in the management of wastewater from several different industries. CTI is available to use this expertise to conduct a wastewater determination at your facility, evaluate management options, and assist your facility through the permitting process if necessary.