Controlling taste and odour events for the city of Philadelphia, USA: a case study

Abstract

The overall goal of this case study is to describe the history and present methods that the Philadelphia Water Department (PWD) uses to address its on-going earthy and musty drinking water T&O problems. The Philadelphia Water Department has developed a baseline for its water's aesthetic qualities since the early 1980’s. Philadelphia feels it has sufficient resources to control taste and odour problems. However, when directly asked, only 61–64% of the consumers are satisfied with the taste and odour of Philadelphia's drinking waters. A taste and odour early warning system is being developed for the two drinking water sources, the Delaware and Schuylkill rivers. Secondly, routine T&O panels and chemical analysis of geosmin and MIB are completed. Since the year 2000, 10 ng/L has become an early warning wake-up call for PWD. When higher levels are observed, testing is a priority, the source of the T&O is investigated and consumer complaints are monitored carefully. Present water treatment plants are conventional with chlorine disinfection, coagulation/sedimentation, rapid dual media filtration and final chloramination. The PWD uses powdered activated carbon, river water bypass and hydraulic changes in the distribution system to minimise odour events.