The Boston Harbor Project, and large decreases in loadings of eutrophication-related materials to Boston Harbor

Abstract

Boston Harbor, a bay–estuary in the north-east USA, has recently been the site of one of the largest wastewater infrastructure projects conducted in the USA, the Boston Harbor Project (BHP). The BHP, which was conducted from 1991 to 2000, ended over a century of direct wastewater treatment facility discharges to the harbor. The BHP caused the loadings of total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS) and particulate organic carbon (POC) to the harbor, to decrease by between 80% and 90%. Approximately one-third of the decreases in TSS and POC loadings occurred between 1991 and 1992; the remaining two-thirds, between 1995 and 2000. For TN and TP, the bulk of the decreases occurred between 1997 or 1998, and 2000.

Introduction

Eutrophication or organic enrichment (Nixon, 1995) caused by elevated inputs of reactive organic matter and/or nutrients (principally N and P), has been identified as a threat to coastal aquatic ecosystems worldwide (Scavia and Bricker, 2006, Schindler, 2006, Cloern, 2001). Many of the wastewater infrastructure projects conducted in the USA over the past 50 years have aimed to reduce the loadings of these materials to these systems (Conley et al., 2009).

Many of the early projects focused on the removal of solids and reactive organic matter from the wastewater discharged to these systems (e.g. Albert, 1987, Brosnan and O’Shea, 1996). More recently, the projects have aimed to also remove nutrients, in certain cases P, and in others, N (e.g. Jaworski et al., 2007, Mallin et al., 2005). Certain of the projects have employed ocean outfalls to minimize the eutrophication-effects of the wastewater discharges (e.g. Smith et al., 1981).

Boston Harbor, a bay–estuary in the north-east USA, has recently been the site of one of the largest wastewater infrastructure projects conducted in the USA, the Boston Harbor Project (BHP) (Breen et al., 1994, Brocard et al., 1994). Before the BHP the total loadings of total nitrogen (TN) and total phosphorus (TP) to the harbor were among the highest reported for bays or estuaries in the USA (Dettmann, 2001, Kelly, 1997).

The two wastewater treatment facilities (WWTF’s) that at the time discharged to the harbor, and later became the focus of the BHP, contributed >90% of these elevated loadings (Alber and Chan, 1994). The harbor also showed symptoms of eutrophication that were typical of a highly-enriched, but well flushed bay (Diaz et al., 2008, Maciolek et al., 2006, Taylor, 2006, Giblin et al., 1997); the average hydraulic residence time of the harbor is 5–7 d (Stolzenbach and Adams, 1998).

This paper documents the changes in the loadings of eutrophication-related materials to the harbor over the course of the BHP, to quantify the contribution of the BHP to the changes. The paper addresses only the loadings to the harbor. Diaz et al., 2008, Oviatt et al., 2007, Maciolek et al., 2006, Taylor, 2006, Tucker et al., 2005, Giblin et al., 1997 and others, have documented the changes to the harbor itself.