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By Julian Sandino, CH2M HILL Vice President and Technology Fellow, IWA Fellow

Dr. Sandino will be presenting on this topic at the IWA World Water Congress on Wed., Sept. 22 from 14:15 – 15:45 as part of the “Science and Application of Water Treatment” segment in Room 11. Click here to view a list of all of CH2M HILL conference activities.

The handling and disposal of wastewater sludge is an increasingly costly portion of the operation of a wastewater treatment plant, and it is developing into an even greater future challenge given the trend of decreasing availability and increasing costs of ultimate disposal options. Recently several technologies and process innovations have been proposed to reduce or eliminate the waste activated sludge fraction resulting from treatment, or to render it more amenable to anaerobic digestion, a common sludge stabilization step, in order to maximize biogas production and the corresponding potential for energy cogeneration.

The Water Environment Research Foundation project 05-CTS-3 Evaluation of Processes to Reduce Activated Sludge Solids Generation and Disposal, which I have been working on for the past three years,  established a comprehensive evaluation methodology for waste activated sludge reduction processes based on the in-depth consideration of a select number of technologies considered to be representative of the many options currently available in the marketplace. One of these technologies is MicroSludge®.

MicroSludge® is a waste activated sludge pre-treatment process that uses caustic pre-treatment to weaken cell membranes, followed by a high-pressure homogenizer, or “cell disrupter,” to provide a sudden pressure drop to burst the cells in thickened waste activated sludge. Previous tests have shown that MicroSludge® significantly reduced the odor of thickened waste activated sludge following mesophilic anaerobic digestion, lowered reactivation potential, resulted in large volatile fatty acids concentrations following acid phase digestion, and greatly decreased the presence of filamentous bacteria in thickened waste activated sludge.

The Des Moines, Iowa Metropolitan Wastewater Reclamation Authority’s Wastewater Reclamation Facility services approximately 400,000 population equivalent and generates about 5,500 dry tons of waste activated sludge annually.  MicroSludge® was installed to evaluate its effect on biogas production and on the quantity of digested sludge residuals for disposal.  In addition to the full scale testing, pilot digesters were also operated at Des Moines to enable side-by-side comparison of the effect of MicroSludge® under stable loading conditions on co-digestion of thickened waste activated sludge with primary sludge and for thickened waste activated sludge digestion alone in response to digester hydraulic retention time.

I will share the early results of the study, which includes reduction in observed total particulate solids due to increased biological conversion to biogas, during my IWA presentation on Wednesday, September 22 at 14:40 in room 11.

Dr. Sandino is a Vice President, Wastewater Treatment Fellow and Assistant Director of Technology at CH2M HILL, with over 20 years of experience leading and assisting multidisciplinary teams in over 100 sanitary infrastructure and environmental projects throughout the world. He was recently nominated to be a member of the newly created IWA Fellows Program.  This program seeks to recognize extraordinary individuals within the community of water professionals and to enlist their commitment and skills in advancing the knowledge and practice of water management through IWA.