Featured in IQ: 2011 Volume 3 Issue 2
Hurricane Katrina sent ripples far beyond the Gulf Coast, ultimately affecting construction material prices throughout the nation. At the time, the City of Claremore, Okla. planned to build a new regional wastewater treatment plant, but skyrocketing costs required officials to consider other options. After Garver analyzed 17 alternatives, officials approved a plan to incorporate a completely new treatment process at the existing site. This conversion has increased the future treatment capacity within the facility's footprint and integrated advanced technologies to produce higher quality effluent.
Garver's design included upgrades to every single process at the plant, converting it from a fixed-film trickling filter system to an advanced activated sludge treatment process with biological nutrient removal (BNR) capabilities.
Garver partnered with the Oklahoma Department of Environmental Quality to obtain targeted design variances. These variances translated into reduced capital expenditures by retrofitting existing concrete structures for new treatment processes.
The upgrades included a new headworks to remove floating debris and grit before water enters the plant, converting trickling filters to roughing filters to increase organic and hydraulic loadings, an advanced activated sludge process, and clarifier upgrades.
Additional improvements included a complete overhaul of the existing solids handling processes, including new aerobic digestion, gravity thickening of primary sludge, new gravity belt thickening and new belt-filter press dewatering.
Together, the new treatment process is helping the Claremore plant produce effluent well below permit levels for biochemical oxygen demand (BOD), total suspended solids (TSS) and ammonia (NH3).
As the heartbeat of the plant, the new activated sludge basins perform a majority of the biological oxygen demand (BOD) and ammonia removal required by the facility's discharge permit. The process is also designed to accommodate biological nutrient removal (BNR) should future discharge permits require more stringent nutrient limits. This marks a change in the plant's treatment processes from a fixed-film process to a complete mix biological process. The improved system uses fine bubble diffused air, which provides a higher oxygen transfer while also meeting mixing requirements. The rate of aeration is streamlined to optimize the biological process through automated dissolved oxygen control.
The new blower building incorporates energy-efficient blowers and motors and uses stainless steel piping. Three multistage centrifugal blowers deliver air to the activated sludge basins (left), and three positive displacement blowers provide air to the aerobic digesters. The system includes automated controls for operator ease.
The new headworks fine screening and vortex grit removal processes remove floating debris and grit from the water. The new redundant fine screens replace the plant's influent channel and manual screening mechanisms, and each screen discharges waste material to a common compactor and conveyor. In addition, two vortex degritters deliver settled grit to a hopper for removal.