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  • pH Pivoting for Algae Coagulation: Bench-Scale Experimentation

    Abstract: Harmful algal blooms (HABs) threaten recreational waters and public supplies across the US, causing detrimental economic and environmental effects to communities. HABs can be mitigated with dissolved air flotation (DAF) treatment, which requires addition of pH-sensitive charged chemicals to neutralize algae, allowing them to attach to microbubbles and float to the surface. During HAB events and photosynthesis, algae raise the pH to levels that are not ideal for DAF. Traditionally, pH is reduced with a strong acid; however, this adds operational cost and permanently adjusts the water’s pH. This study assessed an approach that might allow for infusing CO₂ from diesel-powered electricity generators into the water prior to DAF treatment. It was hypothesized that formation of carbonic acid could temporarily reduce the pH. Results showed that 2.5%–5.0% CO₂ mixed within compressed air can achieve pH levels between 6–7 in algal water with an initial pH of 9–11 and alkalinity of 150 mg/L as CaCO₃. Further, dosing CO₂ before chemical addition yielded a 31% improvement in water clarification. Returning the pH back to natural levels was not achieved using ambient air microbubbles; however, coarse bubble air spargers should be tested to provide more volumetric capacity for CO₂ absorption.

  • Pilot-Scale Optimization: Research on Algae Flotation Techniques (RAFT)

    Abstract: The impacts of harmful algal blooms (HABs) on US national waterways continue to cause significant economic and environmental damage. Researchers at the US Army Engineer Research and Development Center (ERDC) successfully demonstrated the Research on Algae Flotation Techniques (RAFT) project at pilot scale. This study was designed to show that the surface concentrations of algal biomass can be effectively increased with near linear scalability utilizing the natural methods by which some algae entrap air within excreted mucilage for flotation. The surface concentration of cyanobacteria measured as phycocyanin pigment increased by six-fold after RAFT flocculation treatment. Further optimization of chemical delivery systems, mixing, and dissolved air exposure will be required before full scale readiness.

  • Rapid Algae Flotation Techniques

    Abstract: Some harmful algae produce mucilage or extracellular polymeric substances useful for flotation. This study evaluated natural polysaccharides to determine effects on algal flotation with DAF. Food-grade gums (xanthan gum, guar gum, gum arabic, gellan gum, and diutan gum) were tested with cyanobacteria cultures singly and in combination with commercial flocculants (including Tramfloc 222 and Tramfloc 300). Gum arabic alone had no effect when evaluated at concentrations between 10 mg/L and 5,000 mg/L. However, the combination of gum arabic and Tramfloc 300 yielded higher algal flocculation than Tramfloc 300 alone. The combination of xanthan gum (anionic) and guar gum (cationic) did not perform at the level of the combined xanthan gum and Tramfloc 222 in either flocculation or flotation of algae. Tramfloc 222 and xanthan gum; however, yielded effective flocculation seemingly resistant to changes in interfering factors such as turbulence, pH, and temperature. Furthermore, the combination of xanthan gum and Tramfloc 222 provided the most effective flotation and flocculation independent of pH effects. The results suggest that anionic polysaccharides can be used to increase the efficacy of cationic coagulants such as Tramfloc 222.

  • USACE announces public comment on proposed alum treatment system for C-43 West Basin Storage Reservoir pursuant to Section 408

    The U.S. Army Corps of Engineers (USACE) Jacksonville District announces a 30-day public comment period for the Draft Environmental Assessment (EA) and Proposed Finding of No Significant Impact (FONSI) for the approval of construction of an aluminum sulfate (alum) treatment system during the construction of the authorized C-43 West Basin Storage Reservoir (WBSR) in Hendry County, Florida. The Corps is evaluating the request from the South Florida Water Management District (SFWMD) to modify the C-43 WBSR Federal Civil Works project pursuant to 33 U.S.C. 408. Comments are due June 5, 2023.

  • Lake Okeechobee releases planned for Sediment Study on August 23

    The U.S. Army Corps of Engineers (USACE) Jacksonville District plans to execute a minor deviation Tuesday, August 23 that will release water from Lake Okeechobee as part of an ongoing sediment study by the South Florida Water Management District (SFWMD) and the U.S. Geological Survey (USGS).

  • Chitosan as a Coagulant and Precipitant of Algae Present in Backwater

    PURPOSE: : The purpose of this technical note (TN) is to highlight the current state of knowledge of algal flocculation by chitosan and identify data gaps existing between specific algal characteristics and chitosan binding efficiency. Published relationships and correlations between the quality of backwaters and the prevalence of algae, a baseline for flocculation efficiency of microalgae, and ideal treatment instances for algal removal by way of chitosan flocculation and precipitation will be identified.

  • Pomme de Terre Lake shares public health update concerning harmful algae blooms

    HERMATIGE, Mo. - The U.S. Army Corps of Engineers at Pomme de Terre Lake is responding to a toxic blue-green algae bloom with site-specific sampling and posting public health advisory signs around the lake as recommended by state health agencies. On May 31, potentially toxic blue-green algae blooms were observed from Lindley Creek Arm mile marker L8 to the dam. Laboratory results from sample(s) from Lindley Creek Arm mile L5.5 area indicate the dense algae bloom consisted of 98% blue-green algae with algal toxin (microcystin) concentration below the Missouri Department of Natural Resources Public Health Warning Criteria for recreation contact but could be considered dangerous for pets. Considering these results, USACE is closing Nemo Park beach and general caution signs will be posted at access point and boat ramps for public awareness.

  • Blue Marsh Lake updates Harmful Algae Bloom Status

    The U.S. Army Corps of Engineers’ (USACE) Philadelphia District is updating the harmful algal bloom status at Blue Marsh Lake from a Warning Status down to a Harmful Algal Bloom Advisory Status. The update in status does not eliminate the risks associated with harmful algae.

  • Public health information concerning harmful algae in Kansas City District Lake

    The Kansas City District, U.S. Army Corps of Engineers is actively responding to a potentially toxic blue-green algae bloom at Pomme de Terre Lake.

  • Corps announces approval of a planned deviation from Lake O Regulation Schedule to reduce risk from Harmful Algal Blooms

    The U.S. Army Corps of Engineers Jacksonville District, announces the approval of a planned deviation from the water control plan for Lake Okeechobee and the Everglades Agricultural Area, also known as the Lake Okeechobee Regulation Schedule (LORS 2008), in order to reduce risk from Harmful Algal Blooms.