Publication Date
2026
College
College of Natural Resources & Sciences
Department
Geology
Document Type
Poster
Description
In Humboldt County, California, the Humboldt Bay Municipal Water District (HBMWD) draws source water from the Mad River aquifer via Ranney Collectors, where natural filtration produces high-quality water that is disinfected prior to distribution to the cities of Arcata, McKinleyville, Eureka, Blue Lake and Manila. As a result, there is no conventional surface water treatment plant in the area for environmental engineering and water science students at Cal Poly Humboldt to visit and learn from. To address this lack of visibility, we developed a bench-scale demonstration water treatment plant for Dr. Yacob Tesfayohanes’ drinking water treatment course.This project scales down a conventional treatment train into a transparent system that allows students to observe each process step from start to finish. Conventional drinking water treatment facilities follow a standard sequence: coagulation and rapid mixing, flocculation, sedimentation, filtration, and disinfection. Our system replicates this process, beginning with a coagulation chamber, where a small impeller rapidly mixes the flow while a peristaltic pump doses aluminum sulfate (alum) to destabilize suspended particles and promote aggregation. An interchangeable weir/baffle insert is incorporated between the coagulation and flocculation units, enabling students to adjust flow conditions and observe resulting changes in mixing behavior and treatment efficiency. The water then enters a three-chamber flocculation basin, where baffle walls and decreasing mixing velocities encourage the formation of larger, settleable flocs. These flocs move into a sedimentation tank, where velocities approach zero to allow for particle settling. Following sedimentation, water passes through a gravity-driven dual-media granular filter composed of anthracite coal, fine sand, and graded gravel, with an underdrain system that supports automated backwashing. The system is designed with a modular layout, allowing for easy disassembly, maintenance, and cleaning between uses. Whereas municipal treatment plants process millions of gallons per day (gpd), this model operates at a flow rate of 0.1-0.5 gallons per minute (gpm). The design emphasizes turbidity removal as a visible and measurable indicator of treatment performance. System construction is currently underway, and future testing will evaluate turbidity removal and overall treatment performance. Real-time monitoring of pH and turbidity is integrated through sensors that display data on a screen for student observation. Key fluid mechanics principles including flow control, head loss, and hydraulic efficiency, are incorporated into the design, bridging theoretical concepts with hands-on learning. This model serves as both an educational tool and a research platform, increasing visibility of drinking water treatment processes and enhancing student understanding of systems that are not locally accessible.