Enhanced Metals Removal using an MBR

In the development of a new treatment facility for a community in northwestern Indiana, very stringent ammonia-N and metals effluent discharge limits have been issued to address Great Lakes Initiative discharge standards. The Membrane Bioreactor (MBR) was identified as a process that has the potential to achieve those limits at a reasonable cost. Little to no data exists on the performance of MBRs with respect to its ability to remove metals to these very low concentrations (specifically, 2.5 μg/L for copper and 1.3 ng/L for mercury), and therefore, it was not possible to evaluate those characteristics of the technology based on published literature. Faced with this situation, a modeling and piloting study was undertaken to evaluate the process performance and design criteria for a full-scale facility. The study was composed of three phases. The first phase involved computer modeling of the process with the objective of characterizing the proposed MBR system for removal of CBOD5, ammonia-N, phosphorus, and total nitrogen. The second phase involved bench-scale testing for the MBR process with the objective of evaluating its effectiveness with respect to metals removal. The third phase of the study involved on-site pilot scale testing of the proposed system with the objective of establishing operational characteristics likely to be demonstrated in a full scale MBR facility and verifying the results from the benchscale testing. The results of the study demonstrated that the MBR technology applied in the piloting study had superior metals removal ability over conventional treatment. Additionally, the results culminated in the conclusion that a full scale MBR wastewater treatment facility coupled with carbon adsorption for enhanced copper could meet all of the effluent limits as included in the NPDES permit.