World Resource Institute


Regulatory approaches, also referred to as “command and control” approaches, represent one of the most straightforward approaches to controlling pollution, including nutrients. Environmental regulations can take two general forms: standards and emissions/effluent caps or limits. While standards specify certain technologies, practices, or processes that must be implemented, regulatory caps set a level of acceptable pollution, but do not dictate how this level is to be achieved. The two regulatory approaches are described in more detail below.


Standards prescribe particular technologies, practices, or processes that are meant to achieve a specific outcome. Standards might also impose limits on pollution or activities in order to protect the environment. Examples of regulatory standards include:

  • Environmental quality standards restrict pollution or activities in order to protect the resource or the environment. For example, harvest limits on oysters in the Chesapeake Bay are being used to lessen pressures on the oyster population in the Bay. Oysters provide a valuable ecosystem service by consuming algae and other waterborne nutrients.

  • Product/manufacturing standards establish levels of pollutants that cannot be exceeded in the manufacture of a product or emissions from a product. Product standards might also specify the properties or specifications for product design. For example, U.S. law includes nitrogen oxides (NOx) emission standards for vehicles sold in the United States. Vehicles must be designed in such a way as to not exceed maximum NOx emission thresholds.

  • Process/design standards include installation and design standards as well as operating standards. Installation and design standards set requirements that must be met in the design and construction of various installations. Operating standards determine requirements that must be met during the operation of an installation. In Maryland, the Stormwater Management Act of 2007 provides design standards for developers that require new developments to manage stormwater runoff and use design practices with low environmental impact. Mitigating stormwater runoff helps prevent nutrient losses through runoff.

  • Technology/practice standards include prescriptions for the type of technology that must be used or the practices that must be implemented to achieve the desired environmental outcome. For example, in Maryland, all major treatment plants are required to upgrade to enhanced nitrogen removal treatment technologies. Enhanced nutrient removal is the current state-of-the-art technology for nutrient removal in wastewater treatment plants. It is capable of reducing nitrogen concentrations in wastewater discharge to 3 mg/l and phosphorus concentrations to 0.3 mg/l. In contrast, biological nutrient removal technology can only reduce nitrogen discharges to 8 mg/l and phosphorus discharges to 3 mg/l (Saffouri 2005). (Typology of regulatory standards is adapted from Sands 2003.)

Effluent/Emissions Limits and Caps

Effluent/emissions limits and caps include limits on the amount of allowable pollution discharge that can be emitted to the air or water. Unlike standards, regulatory caps do not prescribe the implementation of specific technologies or practices; rather, they place limits on the amount of pollution (e.g., nutrients) that can be released into the environment. The regulated source is generally given flexibility on how this cap is met.

In some cases, regulatory caps are placed at the watershed level, or at some other aggregate level. In the case of watershed caps, the amount of nitrogen or phosphorus leaving a watershed is capped and individual sources of nutrient pollution within the watershed must ensure that this cap is met. For example, under the U.S. Clean Water Act, states must develop and implement a total maximum daily load (TMDL) for water bodies that are impaired by excess nutrients. The TMDL sets a watershed cap and identifies the nutrient sources and reductions required from each source to comply with the TMDL. For instance, in the Long Island Sound (Connecticut and New York, U.S.) a TMDL was developed for nitrogen that calls for the removal of 24 thousand tons of nitrogen by 2014. The TMDL identified that 80 percent of the nitrogen load was from wastewater treatment plants, with the remainder of the load coming from urban stormwater runoff and atmospheric sources originating outside of the watershed. The implementation of the TMDL resulted in effluent nitrogen limits for all wastewater treatment plants in the basin, effectively requiring a 64 percent reduction in nitrogen discharges from regulated facilities (Connecticut Department of Environmental Protection 2001).