The Running Springs Water District (RSWD), which serves the communities of Running Springs, Arrowbear, and County Service Area 79 in the San Bernardino Mountains, currently operates a 1.0 MGD membrane bio-reactor (MBR). The facility, as it stands today, hardly resembles the original MBR plant first commissioned back in 2003. With a constant focus on improving plant performance while reducing operating costs, numerous plant improvements have been made since the initial concept was developed over 15 years ago. Each of these improvements impacted the overall process and drove some level of optimization; probably none more so than those related to the installation of new membrane equipment. The original RSWD packaged wastewater treatment plant (WWTP) was later upgraded to a conventional activated sludge (CAS) plant in the 1980s as the area population grew. In 1999 the RSWD was advised by the United States Forest Service (USFS) that it needed to comply with new phosphorous discharge requirements that would require significant facility modifications. After an extensive evaluation, MBR technology was selected to upgrade the RSWD plant and meet impending new discharge requirements. Other key drivers behind the selection of MBR were phasing and space. Years later after the plant was commissioned, priorities shifted to solids management, increased capacity and energy efficiency. Plant improvements have included new fine screens, the addition of turbo blowers, and the installation of new membrane equipment. In fact, RSWD has taken advantage of several innovations in membrane technology over the past 15 years on two separate occasions as part of planned maintenance and to address higher flows. With the most recent upgrade, The RSWD increased treatment capacity by over 70% and reduced air demand from 1,200 SCFM to 500 SCFM (cutting energy bills in half). The upgrade also changed how the plant is operated and required an optimization process that is ongoing. For example, because the new membrane air scour diffusers are medium bubble, as opposed to coarse bubble, the demand for supplemental oxygen changed. Following the installation of the new equipment it took some time to realize that mechanical mixing would be required to make up for lower aeration (mixing energy). RSWD discovered that the change in equipment and process conditions necessitated the need to adjust mixed liquor suspended solids (MLSS) concentrations in order to optimize the process. While the new ultrafiltration (UF) membranes required more frequent maintenance cleans, overall chemical consumption was reduced as more diluted chemical solutions can be used. Dropping in new membrane equipment was only the start of the most recent Running Springs WRP upgrade. Once the equipment was installed a comprehensive, iterative plan was developed to quantitatively optimize the process. Elements of the plan could prove useful in upgrading other plants, saving both time and money. Plant and system optimization can take on many forms and involve any aspect of an MBR. The following case study on Running Springs shows an example of an MBR system that has maintained a strong commitment to plant optimization and how every aspect of the plant is taken into consideration.
This presentation is available to AMTA Members only.
- Mike Snodgrass / Dennis Livingston
- Ovivo USA, LLC
- AMTA/AWWA Membrane Technology Conference, Long Beach, CA
- AMTA/AWWA Membrane Technology Conference
- Membrane, MBR, Reuse