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

Zeno Levy,Daniel Meyer,James Bays,Richard Smardon

doi:10.3390/su6052392

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 evaluation of “green” CSO treatment systems that account for their unique operational concerns and benefits with respect to sustainable development.

Highlights

The United States Environmental Protection Agency (USEPA) estimates that the 772 combined sewer systems (CSSs) in the United States (U.S.) discharge approximately 850 billion gallons of untreated storm and sewage effluent into the nation’s waters each year [1]
Water quality-based effluent limits are derived to be protective of state water quality standards, which are based on the class and attainable use of the receiving waterbody
Constructed combined sewer overflow (CSO) treatment wetlands are a form of green infrastructure (GI) that have enormous potential to mitigate pollution in urban watersheds of the United States, and may be more sustainable in the long-term when construction and avoidance costs, operations and maintenance, and ecosystem services are considered

Summary

Introduction

The United States Environmental Protection Agency (USEPA) estimates that the 772 combined sewer systems (CSSs) in the United States (U.S.) discharge approximately 850 billion gallons of untreated storm and sewage effluent into the nation’s waters each year [1]. During wet weather, combined runoff and sewage flows can exceed the conveyance capacity of the CSS and discharge into local waterways from multiple point sources prior to receiving treatment. This discharge is known as combined sewer overflow (CSO). Point discharges of pollutants into waters of the U.S are regulated under Section 402 of the Clean. CSO and POTW outfalls are considered point sources and are regulated under NPDES (40 CFR § 122) [2]. POTWs require NPDES permits to discharge treated effluent to waters of the U.S, and include either technology or water quality-based limits for pollutant loading and compliance monitoring.

Methods

Results

Conclusion