Lanier Filter Plant Project Wins Engineering Excellence Award

Improvements Help Gwinnett County Recycle up to 16 Million Gallons per Day of Clarified Backwash Water

Gwinnett County’s recently completed Backwash Equalization Tanks project at the Lanier Filter Plant allows the County to recycle clarified filter backwash water, significantly decreasing the County’s withdrawal from Lake Lanier, its source of water supply. Hazen and Sawyer performed study, design, and construction services for the construction of two backwash equalization tanks, a filtrate equalization tank, and recycle pump stations. The project was recently awarded a 2010 State Award in Engineering Excellence by the American Council of Engineering Companies, Georgia Chapter.

Due to poor settling associated with the backwash clarification system, Gwinnett County historically discharged its clarified filter backwash water to Richland Creek under the plant’s NPDES permit. Hazen and Sawyer used investigative bench-scale experiments and computer water quality blending models to evaluate the settling issues with the backwash clarification system.

Hazen and Sawyer discovered that the batch solids dewatering process was impairing the settling performance of the backwash clarification system, by sending slugs of solids-laden wastewater through the system, raising pH, and causing settling problems. The firm then determined that the most cost- effective means of improving the backwash clarification system was to construct equalization tanks for both the filtrate from the solids dewatering process and the filter backwash water. Filtrate equalization provides several advantages – it allows the filtrate to receive pH adjustment and be fed at a lower, fixed rate into the backwash clarification system, enhancing the settling process. Equalizing the backwash water helps the high-rate clarifiers operate under steady state conditions for optional performance. Previously, pumps cycling caused hydraulic surges through the clarification system, resulting in poor settled water quality.

These newly constructed improvements enable Gwinnett County to recycle up to 16 million gallons per day of clarified backwash water to the head of the plant during peak operations, resulting in reducing water withdrawal from Lake Lanier by the same amount. This project demonstrates the County’s commitment to its environmental sustainability initiative of “living, working, growing green.”

Engineering Excellence is an annual design competition provided by the Georgia Engineering Alliance and held in conjunction with Engineers Week. Engineering Excellence recognizes engineering achievements demonstrating the highest degree of merit and ingenuity. Entries are rated on the basis of uniqueness and originality; future value to the engineering profession; social, economic and sustainable development considerations; complexity; and successful fulfillment of client/owner’s needs, including schedule and budget.

Since our founding in 1951, Hazen and Sawyer has focused on two things: providing safe drinking water and controlling water pollution. Our range of services encompasses the planning, design, and construction management of water and wastewater-related projects – from clean water treatment, storage, and distribution to wastewater and stormwater collection, treatment, and reuse.

Hear about new publications with our email newsletter

We will never share your details with anyone else.