Non-Buoyant Oxygen Infusion System Project & Measurement

This Project presents the results of a Non-Buoyant Oxygen Infusion System Evaluation and Measurement Project at Lake Arrowhead Community Service District (LACSD) Grass Valley Wastewater Treatment Plant (GVWWTP). The study evaluated the energy impacts of the technology’s biological and electro-chemical effects on nutrient loads to the primary, secondary, tertiary treatment and disinfection processes. The study design builds upon the first emerging technology study on non-buoyant oxygen infusion (ET19SCE1030) conducted at the San Luis Obispo Water Resource Recovery Facility (SLO WRRF), which evaluated the non-buoyant oxygen infusion impacts on conventional activated sludge systems through side-stream treatment.  The results of that study demonstrated both the potential for energy savings and non-energy improvements based on Ammonia-N (Ammonia as nitrogen) removal.  The SLO WRRF study, using a demonstration-scale trailer unit, showed the potential for average Ammonia removal efficiency of 1.62 kWh per pound of Ammonia-N, compared to the baseline removal efficiency of 2.80 kWh per pound of Ammonia-N. As a follow-up to the initial study one of the recommendations was to evaluate the implementation of the technology in other wastewater treatment applications.  Therefore, the focus of this report is to evaluate the plant-wide energy impacts that may result from the addition of non-buoyant oxygen infusion in a trickling filter secondary system at the GVWWTP.  The technology was deployed in three study phases, with a fourth phase added for post-evaluation observation and baseline calibration. Phase I – Willow Creek Phase II – Grass Valley Chlorine Contact Chamber Phase III – Grass Valley Primaries Effluent Phase IV – Post- evaluation Observation and Baseline Calibration In anticipation of SCE’s study engagement beginning in Phase II, energy monitoring equipment was purchased by LACSD with installation assistance from AESC via a direct contract with LACSD. Equipment was installed before the beginning of Phase II. PROJECT GOALS – The project evaluated the use of the non-buoyant oxygen infusion treatment technology to manage electricity demand by oxidizing dissolved sulfide, ammonia, and biochemical oxygen demand (BOD) in a wastewater secondary system – in this case at the trickling filter, and downstream system impacts.  The second goal of the study was to provide real-time energy consumption data to plant staff to maximize energy benefits and optimize performance for this and other future efforts. The last goal of the study was to determine the M&V protocols to capture holistic energy savings in future applications. Two hypotheses were tested: 1) non-buoyant oxygen infusion treatment technology applied on secondary treatment trickling filter(s) reduces Ammonia-N and BOD within the secondary treatment system and 2) non-buoyant oxygen infusion treatment reduces the total energy demand of the secondary treatment trickling filter, tertiary treatment, and disinfection systems. TECHNOLOGY DESCRIPTION -- Non-buoyant oxygen infusion treatment technology purifies ambient air to form pure oxygen which is pressurized and emulsified into a stream of water and discharged at high velocity through capillary tubes submerged in water.  This process creates an ultra-fine diffusion of molecular oxygen in the form of nano-bubbles, which collapse upon being discharged into the water, and is hypothesized to generate radical hydroxyl ions of oxygen. This theoretically results in a non-buoyant fluid saturated with highly charged ion radicals of oxygen which remain suspended in water and achieve significantly higher levels of Standard Oxygen Transfer Efficiency (SOTE) than conventional fine or coarse bubble aeration methods, reducing the need for both mechanical and chemical treatments. PROJECT FINDINGS -- In Phase I, the Non-buoyant Oxygen Infusion Treatment Demonstration Unit (NDU) was placed at the Willow Creek Wastewater Treatment Plant, downstream of the primary clarifier. This initial application evaluation was commissioned by the LACSD directly with DUDEK Engineering. The objective was to improve BOD and Ammonia-N removal at the Willow Creek Wastewater Treatment plant by imparting oxygen to its primary effluent, to reduce energy consumption at the GVWWTP within the secondary treatment, tertiary treatment, and disinfection systems. No energy monitoring was conducted in this phase, as it concluded before SCE’s engagement on the project. The Phase 1 application process included discharging oxygenated water into the test pond through the main primary effluent stream. Based on data provided by DUDEK, results from Phase 1 did not demonstrate a significant removal of Ammonia-N or impact downstream performance in the trickling filter performance in the GVWWTP. However, a reduction in BOD load between the primary clarifier effluent and pond influent was observed.  Tables 1 and 2 below summarize the ammonia and BOD loading and removal profile at the WCWWTP. PROJECT RECOMMENDATIONS -- Based on the findings of this preliminary study at GVWWTP, the technology application in municipal wastewater trickling filter secondary treatment systems did not provide viable results to further recommend in this specific treatment application. The energy data results are indeterminate since the technology did not perform in this application.  On the contrary, results show that installation in trickling filter applications may have adverse treatment impacts, such as reducing their effectiveness at removing BOD and Ammonia-N. On the other hand, Phase I findings from WCWWTP suggest there may be more suitable applications for the technology, as a reduction in BOD load between the primary clarifier effluent and pond influent was observed within the primary treatment system. As noted previously, energy data was not collected for the WCWWTP site during Phase I because it pre-dated SCE’s involvement and therefore focused only on biological and chemical impacts. A reduction in BOD is a promising lead to pursue in further evaluations to more fully evaluate the process and energy impacts on broader wastewater applications including in the primary treatment, activated sludge secondary treatment, solids handling, and tertiary treatment/disinfection systems. At this time, it is recommended to focus additional studies on medium to large municipal wastewater treatment plants that employ activated sludge secondary treatment processes.  Additionally, other considerations for future project implementation should consider utility program support to mitigate market barriers of low product awareness, low customer priority, and capital costs of the technology integration through incentives for early adoption. For the technology to gain market traction and adoption, plant managers and operators will need to be aware of, and open to, advances in treatment approaches that challenge business-as-usual paradigms. The technology manufacturer reports that enhancements to the NDU are underway to improve system pressure, control, and reliability, and will be incorporated progressively as the NDU is tested for other applications at other sites. These enhancements could further expand the process benefits of the system and increase the energy efficiency of the test unit’s components.