Codiga Resource Recovery Center Process Overview: Water, Energy, Materials, Nutrients, Information
The Codiga Center diverts wastewater from the Stanford sewer line underneath Serra Street. The wastewater is pumped into the facility, where it proceeds through three treatment steps: the Grit Tank, the Microscreen, and Anaerobic Secondary Treatment. Each of these processes generates a continuous stream of water that flows past the test bed area and through the sensor test station. New treatment technologies can be deployed in each of the four test bed bays or into one of the sensor slots and plug and play into the water quality of their choice to test and evaluate their system.
The grit removal tank aims to allow heavy solids, especially sand and gravel, to settle to the bottom. These solids are flushed back to the sewer, where they join other effluent from the facility and travel to the Palo Alto regional water quality control plant for final treatment. The grit tank serves as a pre-treatment step at the Codiga Center, removing large, inorganic materials that could otherwise interfere with or damage downstream processes.
Our primary treatment makes use of a commercially available microscreen system. The system is equipped with an internal rotating screen belt that has small pores which allow water to pass through, but capture finer particles. As the belt rotates, an internal, secure scraper bar frees the screen of solids and sends them toward a dewatering box where they are compressed to remove water. These solids are available for researchers to test new solids management technologies.
At this point in our treatment system, the majority of solids have been removed and we rely on a biological process to remove the remaing dissolved and suspended material from the wastewater. Traditionally, biological wastewater treatment processes have relied on aerobic bacteria that require oxygen. These processes are very reliable, but they can consume large amounts of energy to aerate the water and produce large amounts of bacterial biosolids that must be hauled off site and disposed. The Codiga Center system uses a different system, called the Staged Anaerobic Fluidized bed membrane bioreactor (SAF-MBR), that relies on anaerobic microbes that do not require oxygen. This process eliminates the energy-intensive aeration step, and also converts waste organic material into methane gas that can be used to produce energy or valuable products. The anaerobic system also produces fewer biosolids than aerobic processes, reducing costs for solids management. as the water moves through this system, it is treated in two stages. The first stage is a traditional fluidized reactor with bacteria growing attached to granular activated carbon. The second stage is similar in structure to the first, but in addition makes use of hollow fiber membranes that separate the last remaining solids from the water leaving the system. As the solids remain inside, they begin to hydrolyze, making them more accesible to bacteria. Additionally, the membrane pores are fine enough to keep most pathogens from leaving in the treated wastewater. This treament system was first developed at Inha University in South Korea, in collaboration with Stanford Professor Emeritus Perry McCarty. a 2-year pilot-scale test of the SAF-MBR in South Korea demonstrated the system could reliably treat municipal wastewater to the secondary effluent water quality standards of the United States, even at low temperatures (9 degrees C, 44 degrees F). The codiga center SAF-MBR is the 4th of its kind in the world, and is the largest system to date.
Our test bed area was built with research and product commercialization in mind. There are 4 identical test bed bays with plug-and-play access to water from each stage of our treatment system (Grit Tank, Microscreen, Secondary Anaerobic Treatment). The bays provide space for researchers and companies to test out their technology in a low-risk setting, as all water exiting the Codiga Center is returned to the sewer for transport and treatment at the Palo Alto regional water quality control plant. In addition, each test bed bay comes equipped with access to biogas - allowing opportunities for research into new uses for biogas, including synthesis of high-value biodegradable materials.
Our sensor test station provides a platform for testing new water quality monitoring technologies designed to detect contaminants (E.g. chemicals, viruses, bacteria, toxic metals, etc.) for any of the grades of water available on site. These technologies are critical to improving the feasibility and reliability of water reuse projects. If we can reduce the amount of time and effort it takes to monitor water quality, we can reduce the costs and improve the safety of our treatment systems.