Lalulita’s Weblog

Laura Almodóvar Acevedo¹, Elba Díaz¹, Alexis Valentín¹, Dr. Arturo Massol¹

1. Biology Department, University of Puerto Rico, Mayagüez Campus

The role of activated sludge in the removal of heavy metals in wastewater treatment plants of geographically distant units is yet to be fully understood. Heavy metals are key components of wastes and their composition and concentration varies from one location to another thus impacting the microbial community composition of the sludge. In this study we measured during six consecutives months the removal efficiency of copper, lead, chromium and cadmium in two water treatment plants in Puerto Rico (Mayagüez and Adjuntas). Samples were collected from the affluent and effluent pipelines, activated sludge from the recirculation unit, the aerobic chamber and the anaerobic unit. Sludge samples were analyzed using general acid digestion with HNO₃ and HCl. Metals were extracted with HNO₃ in the water samples_. Samples were analyzed using atomic absorption spectroscopy. Preliminary results show that both wastewater treatment plants removed metals. Removal of cadmium was observed in both plants. Mayagüez showed significant removal in October through December and showed removal levels of 52%-100%. Adjuntas showed cadmium removal every month except in November and January with 59% to 100%. Significant removal of copper was only observed in Adjuntas. The removal efficiency ranged from 30%-67%. The removal of these metals indicates a significant contribution of the microbial biomass in the wastewater treatment process. Future plans include comparing removal in both plants, a study of the temporal variation and sludge samples analysis. Understanding the responsible microbial groups could help with modeling and optimization of wastewater metal removal in this important biotechnological application.