Malcolm Pirnie - The Largest Post-Filter GAC System in the World

Drinking Water Process & Planning

SOLUTIONS FOR:

Projects

The Largest Post-Filter GAC System in the World

Client:	Greater Cincinnati Water Works
Project:	Richard Miller Water Treatment Plant
Location:	Cincinnati, OH

Issue

The Greater Cincinnati Water Works' 175 mgd Richard Miller Water Treatment Plant draws water from the Ohio river and serves more than 800,000 residents in Cincinnati and suburban Hamilton County. The river is subject to contamination from a variety of sources, including synthetic organic chemicals, pesticides and agricultural chemicals, as well as accidental spills. Although these substances do not exceed current federal standards, the Water Works wanted to reduce the risk of long-term exposure to these chemicals through drinking water and to reduce the vulnerability of the water supply in the event of a major chemical spill.

Solution

After an extensive five-year research and pilot program to test the feasibility of granular activated carbon (GAC) treatment, the Water Works held a design competition, inviting Malcolm Pirnie and two other nationally prominent engineering firms to submit conceptual designs. Malcolm Pirnie's design successfully met the difficult challenge of converting the pilot-scale data and experience into a full-scale design, and we were selected to design the new facility. Key features of the GAC project include:

Carbon Adsorption. Conventionally treated and filtered water from the existing plant passes through 12 GAC contactors, each containing 11.4 ft (600,000 pounds) of carbon, for a contact time of 20 minutes. An innovative stainless steel underdrain system, designed for maximum efficiency and ease of maintenance, collects the treated water and also distributes backwash water. GAC treatment is followed by disinfection and addition of corrosion control chemicals. Two underground water clearwells hold 41 MG of finished water.
Carbon Regeneration. The key to the project's economic feasibility is an on-site carbon regeneration system. Two 40,000 lbs/day multiple-hearth furnaces remove adsorbed organic substances from the spent carbon, preparing it for reuse. A state-of-the-art pollution control system with afterburners and wet scrubbers destroys organics in the flue gases.
Control System. A new control center designed for computer-assisted, operator-controlled operation incorporates the functions of the entire plant. The system features graphical displays of process and operating data.

Benefits

The $60 million GAC facility put the City of Cincinnati in a better position to meet more stringent federal regulations emerging under the Safe Drinking Water Act Amendments of 1986. The added public health protection comes at a very affordable price: the average family's water bill increased by only six cents per day, or about $22.00 per year.

The American Academy of Environmental Engineers (AAEE) recognized this project with its Grand Award.