By Andrea White, PE
The United States and many parts of the world are facing historic drought conditions. In fact, Politico reports, “more than 80 percent of the continental U.S. is experiencing unusually dry conditions or full-on drought, which is the largest proportion since the National Oceanic and Atmospheric Administration began tracking 20 years ago.”
Increased water conservation, along with two and a half years of increasing consumption of items like hand soap and disinfectants due to the pandemic, have created significant challenges for water resource recovery facilities (WRRFs) to efficiently meet regulatory requirements. Hand soap and disinfecting products are part of a larger group of personal and household care items that contain large amounts of surfactants, and when these items―including laundry detergent, dish soap, and surface cleaners―find their way down our drains, they make it more difficult to treat wastewater.
Surfactants in combination with fats, oils, and grease (FOG) inhibit clarification and the activated sludge process, reduce oxygen transfer efficiency, cause odors and process upsets, reduce biomass kinetics, inhibit solids separation and sludge dewaterability, and pass through facilities depleting dissolved oxygen levels in receiving water. This makes it critically important to find ways to remove these materials from wastewater.
For the past several years, the Goleta Sanitation District (GSD) WRRF in Goleta, CA, has been experiencing operational challenges related to high levels of surfactants in their raw wastewater. It was able to identify the problem and remove point sources from industrial users, but found the surfactant load from residential and commercial customers was still affecting treatment efficiency and ease of operation. Earlier this year, GSD sought an innovative, chemical-free way to pretreat raw wastewater to remove surfactants and FOG using a patented nanobubble technology.
Nanobubbles―70-120 nanometers in diameter and 2,500 times smaller than a grain of salt―have oxidative and electrochemical properties that work together to remove contaminants like FOG and surfactants. These gas-filled nanoparticles lack the buoyancy to float to the surface and pop like larger bubbles, staying suspended in liquid solutions for longer. Nanobubbles follow random motion and are stabilized by impurities in water, giving them ample contact time and dispersion to interact with and degrade contaminants.
At the GSD WRRF, a nanobubble generator was installed to provide nanobubble pretreatment at the headworks post-screening and grit removal and before primary clarification. Nanobubble pretreatment yielded an estimated operating cost savings of $127,000 per year.
Specifically, nanobubble pretreatment resulted in:
- Significant reduction in odors, foam, and septicity across the primary clarifiers and equalization basin.
- A 10% increase in primary clarifier solids removal.
- Improved process stability and elimination of process upsets.
- Higher oxygen transfer efficiency from fine bubble diffusers resulting in 43% less power draw from the aeration blowers.
- Secondary treatment process intensification leading to the recovery of more than 20% capacity in existing infrastructure.
- Significant increase in ammonia removal rates (nitrification).
- Improved settleability in secondary clarifiers.
- A 44% reduction in chlorine consumption at the chlorine contact basin.
GSD’s focus was on finding a safe and reliable solution to address the operational challenges it was facing due to increasing surfactant load. Through extensive research and careful vetting, GSD found a solution using a patented nanobubble technology. By resolving operational challenges, GSD will save $127,000 per year in operating cost while recovering 20% treatment capacity.
The results GSD achieved reinforce its commitment to innovation and research and not being afraid to pioneer new solutions. By utilizing this chemical-free, nanobubble technology, GSD has paved the way and set an example for WRRFs around the world that are facing similar challenges.
About the author
Andrea White, PE (CA), is Director of Global Water Process Engineering at Moleaer. In this role, she leads the Application Engineering team at Moleaer, where her research focuses on developing the science of nanobubbles and their application within the water-environment-food nexus.
About the company
Moleaer™ is the global leader in nanobubble technology with a mission to do more using less water. By deploying the power of nanobubbles, the company enhances and improves the performance and productivity of many of the world’s most critical industrial processes.
Moleaer has deployed more than 1,500 nanobubble generator installations in more than 30 countries. To learn more, visit www.Moleaer.com