Fields Point Wastewater Treatment Plant – Rhode Island

Secondary Clarifier Retrofit Improves Performance in High-Flow Municipal System

Industry: Municipal Water & Wastewater Treatment
Location: Providence, Rhode Island
Facility Type: Combined Sewer Wastewater Treatment Plant
Provided by: ClearStream Engineering

Facility Overview

The Fields Point Wastewater Treatment Plant (WWTP) serves the City of Providence and surrounding communities, treating approximately 45.5 million gallons per day (MGD) during dry weather conditions. As a combined sewer system, the facility also treats stormwater during rain events, with secondary treatment flows reaching up to 77 MGD and primary treatment and disinfection handling flows as high as 123 MGD.

The total hydraulic capacity of the Fields Point WWTP is 200 MGD. During extreme storm events, influent flows exceeding this capacity are discharged directly to the Providence River, making efficient treatment and system reliability critical during both dry and wet weather conditions.

The Fields Point Wastewater Treatment Plant

Challenge

As the plant aged, a major retrofit and upgrade of key treatment units became necessary. Following a competitive bidding process, ClearStream Engineering was awarded the project, which initially specified a suction header design for the secondary clarifiers.

During a pre-engineering site meeting, ClearStream engineers worked closely with plant operations staff to better understand day-to-day operating conditions. It was determined that the facility typically operates with a very low sludge blanket depth in the secondary clarifiers. Under these conditions, a suction header design can lead to excessive water withdrawal unless the sludge blanket fully covers the header—making it poorly suited for this application.

Engineering Solution

After reviewing multiple clarifier collection system options, ClearStream recommended modifying the design to a suction pipe secondary clarifier configuration. Unlike suction headers, individually adjustable suction pipes allow operators to compensate for lower sludge volumes, particularly near the outer diameter of large clarifier tanks.

This approach enables improved solids removal, thicker sludge concentration, and more stable clarifier performance under varying flow conditions. ClearStream revised both its technical proposal and pricing to provide a solution that better aligned with the plant’s operational realities and long-term performance goals.

Results

The revised clarifier design delivered improved sludge handling, enhanced operational flexibility, and increased process reliability for one of Rhode Island’s most critical municipal wastewater facilities. The retrofit supports consistent secondary treatment performance across a wide range of influent flows while extending the service life of the upgraded infrastructure.

ClearStream Suction Pipe Clarifier - Fields Point WWTP, Rhode Island