Membrane Separator for Wastewater Treatment

By Annel K. Greene, PhD, Professor and Center Director
Clemson University Animal Co-Products Research and Education Center

Clemson University researchers Drs. David A. Ladner and Yi Zheng have been selected to take recent Animal Co-Products Research and Education Center (ACREC)-funded technology to the next step toward commercial testing. They will be working to develop pallet-sized (or smaller) systems to test membrane wastewater separation processes in a rendering plant environment. Their goal is to demonstrate the membrane units are viable for accomplishing wastewater separation to clean water without the need for chemical additives such as polymers, coagulants, and acids. Ladner’s and Zheng’s processes will be designed to operate autonomously with only occasional remote control by the researchers. The two have several years of experience building remotely controlled, autonomous systems and will use their “lab-on-a-pallet” method to conduct experiments and further examine the technology for commercial application.

Ladner and Zheng, both assistant professors in the Clemson University Department of Environmental Engineering and Earth Sciences, initiated their discussions on this project by first visiting rendering plants in Georgia and South Carolina. They examined the needs of the companies and confirmed current state-of-the-art commercial wastewater treatment processes.

Membrane separators are used to treat wastewater as an alternative method to dissolved air flotation (DAF). DAF is effective in removing fats and proteins by utilizing a variety of chemical additives including flocculant polymers that are then introduced into the rendering product stream when DAF sludge is processed through the rendering cooker. Membranes could eliminate the use of these chemicals and create a chemical-free stream of captured fats and proteins from wastewater.

Previous ACREC-funded proof-of-concept work has proven the potential of membranes to accomplish separation and produce clean water. The focus of that previous work was in materials development. Many kinds of porous polymer (plastics) membrane sheets have been invented over the past several decades. More recently, materials scientists and engineers have found certain chemical surface modifications that greatly reduce the propensity for contaminants to adhere to the membranes. These “anti-fouling” materials show promise during well-controlled laboratory experiments. However, the next stage toward moving these membrane technologies to commercial use will be long-term testing in an actual rendering plant using real rendering plant wastewater. Wastewater varies in its concentration and composition from day to day, or even from hour to hour. It is important to evaluate the new membrane materials under these highly variable conditions.

Ladner and Zheng will create a prototype field-deployable semi-autonomous membrane separation unit (SAMSU). They will operate this SAMSU continuously on campus at Clemson University for three months with no maintenance visits during the final month as part of the testing. Afterward, the prototype SAMSU will be deployed to a commercial rendering facility to test its performance over a three-month trial.

Since typical pilot plant scale-up of new technologies normally involves major financial investment, the SAMSU offers economic advantages for moving the technology out of the laboratory. With this unit, various commercially available membrane units can be field tested to determine feasibility for commercial use. Because membrane technologies require frequent backwash steps, the automation and remote monitoring of the SAMSU makes this small pilot unit readily useable for this application. The unit can be operated and monitored remotely even when processing-plant personnel are not available onsite.

The SAMSU to be created under the current project is seen as a stepping stone for future development of autonomous or semi-autonomous unit processes. The next anticipated step will be creation of a membrane bioreactor that uses essentially the same membrane separation process as the first-generation SAMSU but with a biological reaction tank. The biological process will be similar to those used at many rendering plants and to treat domestic wastewater from cities and towns. The key difference is that membrane bioreactors are very effective at retaining active bacterial cultures so they can operate with a higher concentration of bacteria than conventional processes, allowing the tank to be smaller. A second difference is that a conventional system usually requires a separate settling tank for separations; the membrane can be inserted into the biological tank, eliminating the need for the separate settling tank. Overall, a membrane bioreactor has the potential to greatly reduce the footprint for wastewater treatment.

Ladner and Zheng have many years of experience in developing automated systems and with membrane processes. They will create the instrumentation, sensors, control algorithms, and remote communication to develop the SAMSU. They also will have sensors for pressure, conductivity, and pH incorporated into the unit. Once the unit is completed, the researchers and their graduate students will be able to send commands to the unit in order to adjust the system.

Ladner earned his doctorate from the University of Illinois at Urbana-Champaign in civil and environmental engineering, where he was a fellowship recipient from the Environmental Protection Agency. He was a postdoctoral researcher in the School of Sustainable Engineering and the Built Environment at Arizona State University prior to accepting his current appointment at Clemson University.

Zheng earned his doctorate from the University of California (UC)-Davis in biosystems engineering. He worked as a chemical engineer at the Fujian Yong’an Chemical Plant in China, as a postdoctoral researcher in biosystems engineering in the Department of Biological and Agricultural at UC Davis, as a postdoctoral researcher in biosystems engineering in the Department of Food, Agricultural, and Biological Engineering at The Ohio State University, and as a research scientist at Novozymes Inc. in Denmark.

The benefits of this project for the rendering industry will be further study of the use of membrane technologies to reduce oxidation of recyclable wastewater components and reduce or eliminate the need for chemicals in wastewater treatment. The SAMSU platform will enable more rapid market entry for new membrane materials since scale-up testing can be done more efficiently. This membrane technology will likely lead to lower energy input and costs, and can be conducted in a smaller space than current DAF units.

August 2016 RENDER | back