After extensive testing, the largest
|John Keller and Matthew Schultze|
The Lawrence (Kan.) Wastewater Treatment Plant was recently expanded and improved to meet future growth needs, new regulatory requirements, and facility rehabilitation needs for the design year 2020.
The project expanded the main wastewater treatment
process and included an excess-flow facility to treat peak flows during storm events. The main process is designed to treat 95,000 m3/d (25 mgd); during wet weather events, peak flows in 2020 are predicted to reach 246,000 m3/d (65 mgd) so the excess-flow facility must handle 151,000 m3/d (40 mgd).
.....According to historical plant data, when peak flow is
more than twice the average flow, the amount of waste in the wastewater is significantly lower than usual. Based on pilot work with similar wastewater quality, the project team decided that ballasted flocculation and disinfection would meet excess-flow plant effluent requirements, which were imposed by the Kansas Department of Health and Environment. All effluent must meet the plants National Pollutant Discharge Elimination System (NPDES) permit.
.....The excess-flow facility consists of an ACTIFLO
ballasted flocculation system by Kruger Products
(Cary, N.C.). Kruger was responsible for the process and system design and supplied all the equipment. The system includes two 76,000-m3/d (20-mgd) treatment basins and is currently the largest ballasted flocculation facility for sanitary sewer overflow in the United States.
Ballasted Flocculation System
conventional water treatment technology, a coagulant is used to
destabilize suspended materials entering the process and a flocculation-aiding
polymer is added to aggregate solids into larger masses. The resulting
floc is removed by settling.