Project Overview
The Peirce Island Wastewater Treatment Facility hosted a ribbon-cutting in July 2021 with EPA and other State and local officials and project contractors participating. As intended, this project significantly increased the level of wastewater treatment provided at the facility, resulting in improved effluent discharged to the Piscataqua River. The upgrade included the installation of new headworks, rotary screw presses for solids dewatering and an advanced secondary biological treatment process which removes organics and nitrogen, as outlined in this Fact Sheet. The $93 million project marks a milestone in the City’s history and with $81.9 million in state funding, is the largest in the history of the NH State Revolving Fund loan programs that support drinking water safety, water quality, and public health through low-cost financial assistance. As detailed in the Awards section, the upgrade project has received several awards for its completion under year-round weather conditions and without interruption to the continued operation of the existing treatment facility.Go to WWTF tour video
Project Map
Project Updates
August 4, 2025 Sep 4, 2025
On August 4, 2025 the City Council authorized bonding for equipment deferred during the original construction, due to cost. The City is also conducting pilot studies on different types of coagulants to reduce the corrosive impact of the chloride used currently, evaluating the performance of sludge presses, evaluating clarifier equipment for the potential for upgrades and reviewing alternate carbon sources to manage cost and to balance nuisance biology obstructing the filters. Replacement of the press and clarifier may cause temporary odors, so notice will be given to advise abutters that this is not being caused by an unforeseen issue. The plan is also to replace the chemicals building to optimize operations and reduce impacts. The costs are included in the Capital Improvement Plan (p. 166) adopted in the FY26 City budget.
Update 5/31/25 May 31, 2025
Open House
Update 7/13/21 Jul 13, 2021
Dedication Ceremony
Update 1/3/20 Jan 3, 2020
Methuen Construction meets December 31 milestone for substantial completion of new treatment process for Peirce Island WWTF
Update 11/22/19 Nov 22, 2019
City provides notification that Methuen Construction will not achieve December 1 milestone.
Update 5/28/19 May 28, 2019
Public tour of the Peirce Island WWTF on Thursday, June 13th.
Update 7/24/18 Jul 24, 2018
Public Tour of the Peirce Island WWTF on Tuesday, July 24th.
Update 4/13/18 Apr 13, 2018
Weekend work to continue periodically at Peirce Island WWTF.
Update 2/2/18 Feb 2, 2018
Weekend work to begin at Peirce Island WWTF.
Update 6/28/17 Jun 28, 2017
Overnight work on Peirce Island tonight, June 28th.
Update 6/1/17 Jun 1, 2017
Upcoming night work on Peirce Island.
Update 5/4/17 May 4, 2017
Sewer System Field Work begins May 8, 2017.
Construction of Four Tree Island Parking will be occurring before outdoor pool season.
Update 4/28/17 Apr 28, 2017
Revised Concrete Haul Route for Peirce Island WWTF Work.
Update 4/17/17 Apr 17, 2017
Peirce Island WWTF Upgrade Quarterly Update to City Council.
Update 2/15/17 Feb 15, 2017
Peirce Island Road Bridge repairs resumed.
Update 2/3/17 Feb 3, 2017
Notification of SSO due to sewer main break.
Update 1/17/2017 Jan 17, 2017
Project Documents
General
- Fact Sheet Jan 1, 2021
Project Video
Peirce WWTF Video Tour
Peirce Island Wastewater Treatment Facility
Project FAQ
Does Peirce Island Wastewater Facility Upgrade Project have a dedicated Website?
Yes. Information about the project, including updates, documents, and project details, is available on a dedicated page here at https://www.portsmouthnh.gov/publicworks/wastewater/peirce-island-wastewater-facility/peirce-island-wastewater-facility-upgrade-project
What improvements were included in the upgrade?
The upgrade included installation of new treatment processes such as:
- New headworks
- A biologically aerated/anoxic filter (BAF) system for secondary treatment and nitrogen removal
- Rotary screw presses for solids dewatering
How does the upgraded facility improve wastewater treatment?
The upgraded facility provides an advanced secondary biological treatment process that removes organics and nitrogen, resulting in improved effluent discharged to the river.
What type of treatment system was installed as part of the project?
The project included installation of a biologically aerated/anoxic filter (BAF) system for secondary treatment and nitrogen removal.
Has the project received any recognition?
Yes. The project has received several awards, including:
- NH DES Plant of the Year
- Water Environment Federation Project Excellence Award
- Associated Builders and Contractors Excellence in Construction Award