Charles Schaefer is a senior engineer for CDM Smith, and is the Director of CDM Smith's Research and Testing Laboratory in Bellevue, WA. His areas of research include pore-scale diffusion and mass transfer processes, in situ bioremediation, treatment of emerging contaminants, and electrochemical treatment of drinking water. Charles has served as a Principal Investigator on several SERDP and ESTCP research grants, many of which have focused on chlorinated solvents in bedrock systems. He has authored over 45 peer-reviewed papers and is a member of ITRC. In addition to research, Charles also serves as a technical consultant on several federal and commercial projects for CDM Smith, many of which are addressing emerging contaminants. Charles earned his bachelor's, master's, doctorate degrees in chemical and biochemical engineering from Rutgers University in New Brunswick, NJ, and has over 15 years of consulting experience.
PRACTITIONER WORKSHOP PANELIST
PRACTITIONER WORKSHOP #1: Advances in Treatment of PFAS-Impacted Environmental Media
Electrochemical Treatment for Graywater Reuse: Controlling Disinfection Byproducts
This study, supported by the Environmental Security Technology Demonstration Program (ESTCP), focuses on electrochemical treatment of shower-derived graywater source for potable water reuse. Use of a commercially available electrochemical cell was evaluated in a series of bench-scale studies for treatment of the graywater with respect to COD removal, disinfection byproduct formation, and overall energy demand. Multiple electrodes were evaluated, and both undivided and divided (with sequential anodic-cathodic treatment) electrochemical cell configurations were assessed using a range of applied current densities.
Results showed that the use of mixed metal oxide anodes with a stainless steel cathode were effective for COD removal, but both disinfection byproduct formation (including trihalomethanes, haloacetic acids, and perchlorate) and active chlorine generation were substantial, making the water inappropriate for potable reuse. Use of a divided electrochemical cell, with sequential anodic-cathodic treatment yielded substantially improved results. While initial testing using a stainless steel cathode were ineffective due to rapid corrosion/fouling of the cathode, subsequent testing using a boron-doped diamond cathode proved effective. Formation of chlorinated disinfection byproducts, including trihalomethanes, haloacetic acids, and perchlorate) was inhibited on the anodic side due to the low pH (2.5) conditions. Most notable, no perchlorate formation was detected. The low pH conditions also facilitated the removal of chlorine gas, which mitigated the elevated active chlorine levels in the treated water. Furthermore, COD removal was observed on both the anodic and cathodic side, presumably via generation of hydroxyl radicals and hydrogen peroxide, respectively. In addition, the disinfection byproducts formed on the anodic side (e.g., THMs) were subsequently reduced at the cathode. The energy demand for graywater treatment in the divided cell (approximately 30 kW-h/m3 for an order of magnitude decrease in COD) configuration was approximately have that of the undivided electrochemical cell.
Overall, bench scale results show promise. Current efforts are focusing on the potential for hydrogen capture as a means of energy reuse, calculation of current efficiencies, and on design of a pilot scale system at the Presidio in Monterey.