Written by Dave Taylor, director of special projects, at the Madison (Wis.) Metropolitan Sewerage District
Wisconsin’s Department of Natural Resources (DNR) recently adopted numeric phosphorus criteria, which could cost utilities billions of dollars in treatment upgrades. However, the state also has become the first to offer a more flexible alternative to compliance: adaptive management. In doing so, DNR hopes to encourage affordable, watershed-based alternatives to traditional brick-and-mortar improvements.
Many states are adopting more stringent water quality criteria for nutrients. These criteria and resulting total maximum daily loads (TMDLs) will affect stormwater discharges from Municipal Separate Storm Sewer Systems (MS4s) and effluent discharges from wastewater treatment plants (WWTP).
Through DNR’s adaptive management program, WWTPs and MS4s can offset their phosphorus discharges by funding nonpoint source control practices. The suite of alternatives employed may include green infrastructure or best management practices and could vary significantly from one watershed to another.
Adaptive management acknowledges the fact that controlling nonpoint source pollution may be the most cost-effective means of improving water quality, as tertiary treatment processes can be prohibitively expensive.
Though similar to water quality trading, DNR states that adaptive management gives municipalities greater flexibility. In the end, water quality improvements should result in a revised water quality based effluent limit for the facility.
DNR’s adaptive management strategy also can build on other initiatives, such as restrictions on phosphorus-containing lawn fertilizers and cleaning agents, as part of an overall strategy to achieve compliance with applicable water quality criteria.
In Wisconsin, the adaptive management option can be used if both point and nonpoint sources contribute to excess phosphorus loading. The sum of nonpoint and MS4 contributions must be at least 50% of the total phosphorus load.
Also, WWTPs and MS4s participating in the adaptive management approach are required to optimize existing controls and meet interim permit limits for phosphorus that generally are viewed as achievable without significant upgrades.
Several wastewater treatment plants and MS4s in Wisconsin are evaluating the adaptive management option now. Successful implementation will require much collaboration among nontraditional partners, offering both opportunities and challenges.