AWWA ACE58277

In Puerto Rico, high levels of disinfection byproducts (DBPs) have been problematic over the years for the Puerto Rico Aqueduct and Sewer Authority (PRASA), especially during and after severe tropical storms and hurricanes. A Pilot Plant Study approach was proposed as part of the Action Plan adopted by Compania de Aguas de Puerto Rico (CAPR-Vivendi) and PRASA to reduce formation of DBPs as well as maintain compliance with current and future filtered water turbidity requirements in the Metropolitan San Juan Water System. The advanced treatment pilot plant located at the Sergio Cuevas Water Filtration Plant was designed to evaluate treatment processes and techniques necessary for meeting multiple drinking water quality objectives. The study completed its 5 phases of investigation in September 2001 which included a comparison between conventional flocculation and ballasted flocculation (ACTIFLO(R)) before the sedimentation step (phases 1 and 2), and a comparison between dual-media filtration, microfiltration and inter-ozonation coupled with inter-ozonation (phases 3, 4 and 5). The information obtained through the last three phases of the study clearly indicated that ozonation coupled with biological activated carbon (BAC) filtration not only helps minimize trihalomethane (THM) and haloacetic acid (HAA) formation potentials but also provides good control of effluent turbidity and manganese levels. This combination (ballasted flocculation + biofiltration) offers a superior finished water quality in terms of minimal organic content and low DBP formation potentials. Its implementation would however require special monitoring of bromate formation as a result of ozonation. Ballasted flocculation combined with microfiltration offers a great barrier against suspended solids. Includes table, figures.