Phosphorus is a nutrient critical for plant and animal life. However, in freshwater, excess phosphorus can impair lakes and rivers.
Phosphorus is applied to agricultural land as fertilizer, found in our food, and eventually finds its way to wastewater treatment facilities. The source of in-stream phosphorus impairment is from both point and non-point sources. Point sources are typically wastewater treatment facilities or other sources that discharge into surface water. Non-point sources are typically stormwater runoff from cities or farmland.
Now, with the EPA enforcing stricter water quality standards for phosphorus discharged from industrial and municipal wastewater treatment plants and other point sources, many municipalities are facing deadlines for compliance.
Often, the first solution that comes to mind is expensive upgrades to or building entirely new wastewater treatment facilities. But, there are other, potentially less expensive ways to comply.
Our experts weigh in on a few alternative ways municipalities, utilities and industries discharging phosphorus can work toward complying with water quality standards. Keep in mind though, regulations change from state to state, and knowing what your state requires is the first step.
If your municipality can’t afford to comply with phosphorus regulations, you can apply for an exception.
Individual point source dischargers can apply for a variance to water quality standards when the cost of compliance is too expensive. An individual economic variance may be granted when a municipality’s sewer use charges are greater than the community can afford. Factors used to evaluate qualifying for a variance include existing debt, bond ratings, unemployment rates, property taxes and more. Economic variance requests have to be submitted with each permit re-application, or if conditions in the community change.
“Some communities just don’t have the resources for brand new facilities or expensive upgrades, so we’re helping them find other ways to comply,” says Katie Jo Jerzak, SEH wastewater engineer.
If your community is in good financial health, with low user charges and doesn’t qualify for a variance, then consider looking to a nearby industry to see if they can use your wastewater.
Finding an industrial partner to take on your wastewater discharge is another method for compliance.
With consumptive use, treated wastewater is used in other applications, instead of discharging it back into lakes, rivers or streams. This approach requires the discharger to partner with an entity that can use the water. “Mining operations or concrete facilities are just two of the entities that may be able to use the wastewater in their applications,” says Jerry Doriott, wastewater engineer. “It’s all about finding the right partner.” With additional treatment, reclaimed wastewater can be used in numerous other applications. Feasibility studies can help determine potential partnerships for wastewater use.
If there aren’t any local businesses that can use your wastewater, consider finding another location to put it.
There are two methods of Alternative Discharge: Discharge Relocation and Land Disposal of Effluent. Each with its own guidelines.
Discharge Relocation – Under this method, a facility discharges into a stream that already meets the target water standards, knowing their discharge won’t degrade it further. Figuring out whether discharge relocation is right for you will require some calculation. “There are dilution calculations to determine if phosphorus levels will remain acceptable,” says Dan Schaefer, wastewater engineer.
Land Disposal of Effluent – With this approach, effluent is discharged into the ground, where it percolates through the soil, into the groundwater. “Phosphorus does not impact groundwater like it does surface water, so the permit requirement is eliminated,” says Schaefer. “It also recharges the groundwater.” There are two methods of land disposal: spray irrigation and rapid infiltration, or seepage cells.
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Partnering with a neighboring municipality is called regionalization.
Regionalization involves pumping the wastewater to another municipality’s facility for treatment. For this approach to work, you need a nearby facility that can take on the additional load. However, when a community uses this method, it can’t directly control how much to charge residents.
Water quality standards can also be met by cooperating with another point source through watershed collaboration.
Watershed collaboration typically involves two primary methods: Water Quality Trading and Adaptive Management. Both methods encourage point sources to collaborate on watershed projects for phosphorus reductions in the watershed. It’s important to note that adaptive management focuses solely on phosphorus reduction in Wisconsin, whereas, water quality trading can involve other pollutants and is used in other states.
According to Karen Cavett, water and wastewater engineer, adaptive management and water quality trading have different permit requirements, making them different from a permitting and timing standpoint.
Trading focuses on offsetting phosphorus from a discharge to comply with a permit limit. This approach requires trade ratios to be used to quantify reductions used to offset a permit limit. For example, if a wastewater treatment plant is unable to reduce phosphorus levels, it may work with an area farmer, establishing best practices to reduce phosphorus levels through things like manure clean up. The result is no net increase of phosphorus in the watershed. Adaptive management focuses on achieving water quality for phosphorus in the surface water.
Because adaptive management focuses on water quality improvements, in-stream monitoring is required, whereas it is not required for trading. Practices used to generate reductions in a trading strategy must be established before the phosphorus limit takes effect. Adaptive management is a watershed project that can be implemented throughout the permit term. The reductions needed for adaptive management are based on the receiving water, not the effluent, and trade ratios are not necessary in this calculation. Adaptive management trades can involve shoreline or stream bank protection, changing fertilizer use in agriculture, soil management, wetland treatments and more.
SEH can help cities determine what method of phosphorus reduction is right for them. Every scenario is different, and there are a number of factors to consider.
The City of Princeton, Minnesota, discharges its treated wastewater into the Rum River, a tributary of the Mississippi. To offset the phosphorus, SEH worked with the City to identify potential nonpoint source trades to put together a Water Quality Trade program. The trade involved restoration and maintenance of the stream banks in five areas of the Rum River. The result was a net decrease of phosphorus going into the river. The permit gives the City credit for the reduction of phosphorus discharged from the wastewater facility.
This is the first trade of its kind for a municipal wastewater treatment facility in Minnesota, using a nonpoint source to make up for pollution from a point source.
If your point source is having difficulty meeting the timeline for water quality, consider having it extended with a multi-discharger variance.
The multi-discharger variance (MDV) provides point source dischargers temporary relief from phosphorus discharge requirements. It allows for an extended timeline to comply with the standard. The discharger agrees to temporary phosphorus limits that get progressively stricter over the course of 15 years. According to Heidi Kennedy, natural resource scientist, the discharger must also contribute funds or implement other projects that go toward reducing phosphorus levels within the watershed.
Katie Jo Jerzak, EIT, is a graduate wastewater engineer in Wisconsin who has worked on municipal and industrial wastewater treatment facilities. She works mainly with small- to medium-sized treatment operations and is involved from the design to the construction phase.Contact Katie
Jerry Doriott, PE, is an engineer with 35 years of experience in wastewater engineering, including municipal and industrial wastewater treatment facilities. He has worked on all phases of wastewater planning, including grant coordination, permitting, design and construction.Contact Jerry
Dan Schaefer, PE, is a wastewater engineer with 11 years of experience, focusing on wastewater treatment plant planning, operations, process optimization, design and construction administration for municipal and industrial clients.Contact Dan
Karen Cavett, PE, is a water and wastewater engineer with 25 years of experience. Karen specializes in the planning and engineering services for water and wastewater facilities, as well as rehabilitation and expansion projects, feasibility studies and agency coordination.Contact Karen
Mark Mickelson, PE, is a water resources engineer with 28 years of experience. Mark has extensive experience managing capital improvement projects as well as stormwater management and municipal engineering projects.Contact Mark
Heidi Kennedy is a natural resource scientist with more than 15 years of experience working with the Wisconsin Department of Natural Resources. Heidi has a lot of experience in water resource policies working with federal, state and local agencies on natural resources issues.Contact Heidi