Updated federal D/DBP Rule standards necessitate water treatment plants reduce the concentration of total trihalomethanes and haloacetic acids in their water distribution systems.

The City of Scottsdale selected Malcolm Pirnie to provide engineering services, from preliminary design through construction, for a GAC facility at its 53 MGD Central Arizona Project Water Treatment Plant. The Pirnie team constructed a diversion structure and pump station to permit bypassing the GAC facility in response to water quality conditions; added a contactor-to-waste capability to avoid possible turbidity spikes after backwashing; as well as a contactor-to-waste and backwash water equalization capability to permit recycling flows and provisions for efficient GAC media delivery and replacement.

The GAC facility puts Scottsdale ahead of the regulatory curve, meets D/DBP Rule requirements, substantially eliminates potential seasonal taste and odor issues and reduces O&M costs.