A Point Source of a Different Color: Identifying a Gap in United States Regulatory Policy for “Green” CSO Treatment Using Constructed Wetlands

Abstract

Up to 850 billion gallons of untreated combined sewer overflow (CSO) is discharged into waters of the United States each year. Recent changes in CSO management policy support green infrastructure (GI) technologies as "front of the pipe" approaches to discharge mitigation by detention/reduction of urban stormwater runoff. Constructed wetlands for CSO treatment have been considered among suites of GI solutions. However, these wetlands differ fundamentally from other GI technologies in that they are "end of the pipe" treatment systems that discharge from a point source, and are therefore regulated in the U.S. under the National Pollution Discharge Elimination System (NPDES). We use a comparative regulatory analysis to examine the U.S. policy framework for CSO treatment wetlands. We find in all cases that permitting authorities have used best professional judgment to determine effluent limits and compliance monitoring requirements, referencing technology and water quality-based standards originally developed for traditional "grey" treatment systems. A qualitative comparison with Europe shows less stringent regulatory requirements, perhaps due to institutionalized design parameters. We recommend that permitting authorities develop technical guidance documents for OPEN ACCESS Sustainability 2014, 6 2393 evaluation of "green" CSO treatment systems that account for their unique operational concerns and benefits with respect to sustainable development.

Challenges of mainstreaming green infrastructure in built environment professions

“…Numerous studies have found that GI is actually cheaper than traditional grey infrastructure (Levy et al 2014;Li et al 2017;Tayouga and Gagn e 2016;Wild, Henneberry, and Gill 2017). A study by Yang et al (2015) measured the performance goal of retaining 100% of stormwater on-site and found savings of $40 million USD in stormwater infrastructure using GI strategies in Daybreak, Utah.…”

“…Although GI may be cheaper, regulations may offset this economic advantage, particularly when the design parameters have not been institutionalized. In a cost-benefit analysis, Levy et al (2014) found that although constructed wetlands are the most economical solution to stormwater management in the United States, regulations that mandate water quality goals may hinder this economic advantage. Constructed wetlands, the authors explain, are a GI technology at the "end of the pipe" (p. 6) and therefore considered a point source for discharge; and this condition puts constructed wetlands under the US National Pollution Discharge Elimination Systems regulations.…”

“…In contrast, in Europe, regulations for constructed wetlands are less stringent and monitoring is minimal because of institutionalized design parameters (Levy et al 2014). Constructed wetlands have been operating for a long time in Europe (since the 1990s, mostly in Germany, Denmark, and Belgium); therefore, the design parameters and the resulting treatment efficiencies have been proven, or institutionalized.…”

Constructed Wetlands for Treatment of Combined Sewer Overflow in the US: A Review of Design Challenges and Application Status

“…The secondary services have been frequently cited to support inclusion of CWs in long-term CSO control plans [13,14]. Nevertheless, the value of secondary ecosystem services such as aesthetic quality and wildlife habitat in urban communities has not been quantified yet [5,25].…”

“…This CSO wetland treatment system is permitted as two outfalls (#501 and #502) of the Akron Municipal Wastewater Treatment Plant by NPDES Permit IN0025232 [8]. The CSO discharges from two CSO points undergo grit and floatable removal in swirl separators, which then flow through two serpentine earthen FWS wetlands [5]. There are rock filtration structures at the inlet and outlet of the wetlands to help remove debris [18].…”