Wastewater Treatment Facilities Best Management Practices During Transition

This document shares best management practices (BMPs) for preventing the spread of invasive Phragmites australis (Phragmites) into the landscape surrounding wastewater treatment facilities (WWTF). The risk of spread will remain during the period in which WWTFs are permitted to continue to use Phragmites until viable alternatives are available. Interviews and site visits highlighted potential areas of risk resulting from WWTF using Phragmites in reed beds. Potential strategies were identified for minimizing those risks. For the facilities that will continue to use Phragmites, it is critical to implement best management practices to prevent the further spread of Phragmites into the landscape via seed or plant fragments.

Preventing Phragmites escape and establishment

1. Understand the potential modes of spread for the WWTF.
2. Identify and implement methods to contain Phragmites and prevent spread from the facility.
3. Establish a procedure to survey the area ( 1-mile radius) surrounding the WWTF.
4. Establish a schedule to survey the area surrounding the WWTF.
5. Determine steps (treatment) to take if potentially escaped Phragmites is found in the landscape.
6. Engage County Agriculture Inspector (CAI) to implement a management plan.
7. Evaluate potential alternative biosolids treatment options.
8. Establish a reasonable timeframe to implement an alternative treatment option.
9. Establish who will be responsible for each action.

See treatment recommendations at the Minnesota Aquatic Invasive Species Research Center website.

Reed Bed Management Practices

Annual reed bed management

The aboveground biomass of Phragmites in reed beds is cut down and disposed of annually. The biomass is typically disposed of by burning. Each facility has its own procedure for cutting and burning the aboveground biomass. Some facilities have attempted to burn standing reeds, but have found that the fire burns very hot, risking damage to infrastructure within the reed beds (PVC pipes or wooden end boards). In lieu of burning the reeds standing in place, operators use different types of equipment to cut the reeds, including brush saws, jari mowers, skid steers with brush cutter, or tracked bobcats with a sickle mower attachment. The cut stems are typically piled in the middle of the reed bed or in a nearby location outside of the reed bed prior to burning. At some facilities, the reeds are manually raked into piles by laborers. Most facilities wait until the ground is frozen for easier access to the beds. That may be anytime from late November until March. The timing must be balanced with the risk of early snow cover impeding the cutting and burning of the reeds. The longer the reeds stand, the drier they are and the more readily they will burn. Unfortunately, the longer the reeds stand, the greater the opportunity for seed to disperse as well.

Areas of risk:

1. Equipment used to cut and stack the reeds will get seeds stuck in it. Although rhizomes are beneath the frozen surface, and the standing stems are dead, seeds are highly likely to be spread during this process. When the equipment is moved off-site for use on another job site, viable seeds may be moved to the new site as well.
2. When the reeds are physically cut or stacked using human labor, the workers may get seeds on their clothing, footwear, or other gear that could potentially be moved to new locations.
3. The longer Phragmites is standing, the greater the chance that seed will disperse.
4. When Phragmites is cut, fragments of the plant, including seed heads may be scattered around the work area.
5. As Phragmites is cut, the disturbance may cause the seed to loosen from the plant and disperse to a greater extent than undisturbed plants.

Solutions to reduce risk:

1. Equipment used to cut and stack the reeds must be cleaned to remove seeds. Clean equipment thoroughly prior to moving equipment to a new site. Review guidance from the Department of Natural Resources Operational Order 113.
2. Wear clothing that seed is less likely to catch on. While still on site, clean outer clothing by brushing it off, shaking it out, or vacuuming to remove seed. Wear waterproof footwear and clean mud and plant parts from footwear prior to leaving the site. Vacuumed material must be handled appropriately to avoid spread.
3. Clean up plant fragments, especially seed heads, by raking, etc.
4. Cut Phragmites as soon as is reasonable in late fall to minimize opportunities for wind dispersal of seed.
5. Manage aboveground biomass on site to avoid transporting viable seed.
6. Apply plant growth regulators to stop seed development. Research into this option is needed.
7. Survey a 1-mile radius around the WWTF and work with CAI to treat any Phragmites populations found using established treatment protocols.

Removal of biosolids from reed beds

When beds have reached capacity for storage of biosolids and/or when transitioning away from Phragmites in reed beds, the beds must be cleaned out and the biosolids will typically be land applied or landfilled. The aboveground biomass may be cut and disposed of (burned) prior to the biosolids/belowground biomass being removed from the bed.

Areas of risk:

1. The equipment (rented, contractor-owned, or municipality-owned) used to remove the biosolids from the beds, transport the biosolids, and spread the biosolids at the land application site all pose a risk of moving Phragmites to other sites.
2. The trucks used to haul biosolids may not be sealed. Biosolids are dried down to varying levels prior to excavation and transport, but in some cases may be liquid enough to leak from some styles of truck beds. These liquids may contain viable seeds.
3. All live parts of the plants (rhizomes, stolons, stems, seeds) are capable of establishing new plants.

Solutions to reduce risk:

1. Clean equipment thoroughly prior to moving equipment to a new site as per guidance such as the Department of Natural Resources Operational Order 113. 
2. Use side-dump trucks instead of end-dump or belly-dump styles of truck to transport wet biosolids to land application or landfill sites.
3. Alternatively, ensure that the biosolids are dry such that no liquid will leak from the biosolids during transport. This requires taking beds offline prior to excavating them. One facility took their beds offline for 6 months prior to excavating and land application.
4. Cover and secure the load to prevent plant parts or biosolids from falling off the truck.
5. Manage all aboveground biomass on site prior to excavating to avoid transporting seed heads containing viable seed. Cut and burn above-ground biomass or treat reeds with herbicide (Imazapyr is preferred, Glyphosate is also acceptable). The optimal window for treatment is from early August through September. Allow at least 2 weeks after herbicide treatment before disturbing the plants.
6. Apply only at sites approved for land application and follow all land application requirements.
7. Monitor a 1-mile radius around land application sites for Phragmites establishment.

Permanent removal of Phragmites from reed beds

When taking steps to transition away from using Phragmites in a WWTF, it will be desirable to apply herbicides to kill the rhizomes. It is not necessary to wait until reed beds are full before eradicating Phragmites. It is possible to eradicate Phragmites using herbicides and continue to fill the beds if desired. Alternatively, it may be desirable to wait to transition away from Phragmites when reed beds have reached capacity and must be excavated anyway. Treatment with herbicides is recommended prior to hauling out the beds. Small fragments of rhizome left in the bed are enough to regenerate a bed of Phragmites within 2 to 3 years.

Areas of risk:

1. Phragmites is not effectively eradicated in the reed beds.
2. Phragmites already established in the landscape may be overlooked.

Solutions to reduce risk:

1. Treat Phragmites with herbicides (Imazapyr preferred, Glyphosate also acceptable) to kill rhizomes prior to excavating reed beds. The MPCA has approved the use of Imazapyr and Glyphosate.
2. Treatment in the window from early August through September is most effective to control Phragmites and will also prevent seed development.
3. For effective kill, leave beds intact for at least 2 weeks after herbicide treatment.
4. All biosolids must be completely removed from the beds to eliminate risk of re-establishment. Corners, areas against walls, and areas around standpipes will need extra attention to ensure complete removal of biosolids.
5. Continue to manage Phragmites as a noxious invasive weed after herbicide treatment; manage appropriately (landfill or land apply). Note that biosolids treated with Imazapyr may affect crops grown on land application sites within 5 months of application. Also refer to the “Permit Conditions Final” document for permit conditions and best management practices for the transportation and land application of biosolids from the beds.
6. Monitor reed beds for any re-establishment of Phragmites. Spot treat resprouts in August-September (some earlier treatment times may work for spot treatment).
7. Monitor a 1-mile radius around land application sites for Phragmites establishment.
8. Continue to monitor the area around the WWTF for 2 years after eradicating Phragmites from reed beds.

These BMPs were developed by Julia Bohnen and Daniel Larkin of the University of Minnesota with input from MN Dept of Natural Resources, MN Dept of Agriculture, and MN Pollution Control Agency personnel, as well as from WWTF staff.