Copper and Zinc Reduction at a WWTP by Enhancing Biological Treatment

A municipal wastewater plant in Virginia, recently implemented a copper and zinc reduction program consisting of:Dissolved oxygen (DO) management by variable frequency drive (VFD) installationAlkalinity management by changing the form of chemical supplemental alkalinitySolids retention time (SRT) management by centrifuge installationAfter the plant implemented these measures, it was observed that biological treatment and effluent metals concentrations were improved. The primary mechanism that led to improved metals removal is believed to be the binding of metals to floc polymers. In this study, the floc matrix was ameliorated by enhanced floc bridging (by reducing the M/D ratio) and increased EPS production (increasing the active biomass fraction as a result of SRT reduction). The biological uptake of metals within the cell is believed to have been a secondary mechanism that may have contributed to improved metals removal.