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Tag: water quality
  • 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.
  • Management Strategy for Overwintering Cyanobacteria in Sediments Contributing to Harmful Algal Blooms (HABs)

    Purpose: Cyanobacteria that cause harmful algal blooms (HABs) can overwinter in sediments as resting cells (akinetes or vegetative colonies) and contribute to seasonal bloom resurgences. However, to date there has been limited focus on management tactics specifically targeting the control of cyanobacterial sources from sediments. Targeting resting cells in sediments for preventative management may provide a viable approach to delay onset and mitigate blooms (Calomeni et al. 2022). However, there are limited resources for this novel strategy. Given the growing global impact of HABs, there is a need to develop management strategies focused on sediments as a potential source and contributor to HABs. Therefore, the objective of this report is to provide a management strategy in terms of approaches, information, and case study examples for managing overwintering cyanobacteria in sediments with the goal of mitigating seasonal HAB occurrences.
  • Monitoring Geomorphology to Inform Ecological Outcomes Downstream of Reservoirs Affected by Sediment Release

    Abstract: Increasingly, reservoir managers are seeking techniques that improve sediment management while considering long-term sedimentation and reduced operational flexibility. These techniques, often termed sustainable sediment management, involve passing sediment through reservoirs and into downstream rivers. Conceptually, restoring sediment continuity can benefit ecosystem function by increasing floodplain connectivity, contributing to the heterogeneity of channel geomorphology, and supporting the continuity of nutrient cycling. However, when a change is made to operations, geomorphic changes may need to be monitored to document benefits and mitigate any unexpected effects of the change. This investigation develops a geomorphic monitoring plan for downstream reaches affected by sediment-release operations at reservoirs. The monitoring objectives are aligned with potential geomorphic change caused by changes to sediment supply and the associated effects on river function. A tiered approach is presented to explain the quality of information that can be assessed from increasing levels of data collection. A general conceptual model is described in which geomorphic data may be linked to physical habitat conditions and, therefore, ecological processes. The geomorphic monitoring plan for the Tuttle Creek Reservoir water injection dredging (WID) pilot project is presented as a case study. This technical note establishes a general framework for monitoring the design for sustainable sediment management in different ecological and geomorphic contexts.
  • USACE Freshwater Harmful Algal Bloom Research and Development Initiative

    Abstract: Harmful Algal Blooms (HABs) represent a significant and costly threat to our nation’s economy and natural resources. This report outlines the US Army Corps of Engineers, Engineer Research and Development Center’s (USACE-ERDC’s) approach to deliver scalable technologies for prevention, early detection, and management of HABs to reduce HAB event frequency, severity, and duration.
  • ERDC-PT: A Multidimensional Particle Tracking Model

    Abstract: This report describes the technical engine details of the particle- and species-tracking software ERDC-PT. The development of ERDC-PT leveraged a legacy ERDC tracking model, “PT123,” developed by a civil works basic research project titled “Efficient Resolution of Complex Transport Phenomena Using Eulerian-Lagrangian Techniques” and in part by the System-Wide Water Resources Program. Given hydrodynamic velocities, ERDC-PT can track thousands of massless particles on 2D and 3D unstructured or converted structured meshes through distributed processing. At the time of this report, ERDC-PT supports triangular elements in 2D and tetrahedral elements in 3D. First-, second-, and fourth-order Runge-Kutta time integration methods are included in ERDC-PT to solve the ordinary differential equations describing the motion of particles. An element-by-element tracking algorithm is used for efficient particle tracking over the mesh. ERDC-PT tracks particles along the closed and free surface boundaries by velocity projection and stops tracking when a particle encounters the open boundary. In addition to passive particles, ERDC-PT can transport behavioral species, such as oyster larvae. This report is the first report of the series describing the technical details of the tracking engine. It details the governing equation and numerical approaching associated with ERDC-PT Version 1.0 contents.
  • A Review of Algal Phytoremediation Potential to Sequester Nutrients from Eutrophic Surface Water

    Abstract: Harmful algal blooms (HABs) and coastal hypoxic zones are evidence of cultural nutrient enrichment affecting public health and water supplies, aquatic ecosystem health, and economic well-being in the United States. Recognition of the far-reaching impacts of Midwest agriculture has led to establishing nutrient reduction objectives for surface waters feeding the Gulf of Mexico, Lake Erie, and many smaller water bodies. Municipal nutrient enrichment impacts have been addressed by increasing levels of sewage treatment and waste management through the Clean Water Act era, but HABs rebounded in the 1990s because of non-point source nutrient enrichment. HAB control and treatment includes watershed and waterbody treatments to reduce loading and address outbreaks. Systems to remove nutrients from impaired waters are expensive to build and operate. This review of algal production systems summarizes emerging algal water treatment technologies and considers their potential to effectively sequester nutrients and atmospheric carbon from hundreds of eutrophic reservoirs and DoD wastewater treatment facilities while producing useful biomass feedstock using solar energy. Algal water treatment systems including open ponds, photobioreactors, and algal turf scrubbers® can be used to grow biomass for biofuel, wastewater treatment, and commercial products. This review recommends continuing research on surface water nutrient reduction potential with algal turf scrubber productivity pilot studies, preliminary site design, and biomass utilization investigations.
  • Qualification of Hanna Instruments HI9829 for the Environmental Toolkit for Expeditionary Operations

    Abstract: A new, commercially available, field-portable water sensor was evaluated for efficacy during operation and compatibility with current Environmental Toolkit for Expeditionary Operations (ETEO) software. The ETEO provides sensors to Soldiers to rapidly identify and quantify environmental contamination in soil, air, and water at potential new base sites during initial reconnaissance to ensure safety and minimize unnecessary remediation efforts by the Army. In addition to streamlined environmental baseline survey (EBS) reporting, the ETEO can provide rapid analysis of potential environmental contamination to support various Military applications. The Hanna Instruments HI9829 multiparameter water meter was selected following a survey of commercial off-the-shelf (COTS) technologies and analyzed by researchers from the US Army Engineer Research and Development Center (ERDC) for inclusion in the ETEO design since it can rapidly and accurately measure 14 different properties. Usability tests were conducted with researchers unfamiliar with the technology, and a set of standard operating procedures (SOPs) were developed to operate the device. The software for the tool was successfully integrated into the ETEO system for rapid data analysis. The HI9829 has been demonstrated in various scenarios at ERDC and other locations; including Ft. Leonard Wood, MO, at which several visitors reviewed the operation of the equipment and other ETEO technologies. The Thermo Scientific Gemini, another sensor, which can detect organic constituents in various matrices via Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy was also investigated but eliminated from the ETEO design as it could not adequately detect a Military-relevant compound in an environmental matrix. Regardless, the addition of the HI9829 provides water quality monitoring to the ETEO design and greatly improves its capability to address various applications.
  • Is Mean Discharge Meaningless for Environmental Flow Management?

    PURPOSE: River ecosystems are highly dependent on and responsive to hydrologic variability over multiple time scales (e.g., hours, months, years). Fluctuating river flows present a key challenge to river managers, who must weigh competing demands for freshwater. Environmental flow recommendations and regulations seek to provide management targets balancing socio-economic outcomes with maintenance of ecological integrity. Often, flow management targets are based on average river conditions over temporal windows such as days, months, or years. Here, three case studies of hydrologic variability are presented at each time scale, which demonstrate the potential pitfalls of mean-based environmental flow criteria. Each case study shows that the intent of the environmental flow target is not met when hydrologic variability is considered. While mean discharge is inadequate as a single-minded flow management target, the consequences of mean flow prescriptions can be avoided in environmental flow recommendations. Based on these case studies, a temporal hierarchy of environmental flow thresholds is proposed (e.g., an instantaneous flow target coupled with daily and monthly averages), which would improve the efficacy of these regulations.
  • Identification and Preventative Treatment of Overwintering Cyanobacteria in Sediments: A Literature Review

    Abstract: Freshwaters can experience growths of toxin-producing cyanobacteria or harmful algal blooms (HABs). HAB-producing cyanobacteria can develop akinetes, which are thick-enveloped quiescent cells akin to seeds in vascular plants or quiescent colonies that overwinter in sediment. Overwintering cells produce viable “seed beds” for HAB resurgences and preventative treatments may diminish HAB intensity. The purpose of this literature review was to identify (1) environmental factors triggering germination and growth of overwintering cells, (2) sampling, identification, and enumeration methods, and (3) feasibility of preventative algaecide treatments. Conditions triggering akinete germination (light ≥0.5 µmol m-2s-1, temperature 22-27℃) differ from conditions triggering overwintering Microcystis growth (temperature 15-30℃, nutrients, mixing). Corers or dredges are used to collect surficial (0-2 cm) sediment layers containing overwintering cells. Identification and enumeration via microscopy are aided by dilution, sieving, or density separation of sediment. Grow-out studies simulate environmental conditions triggering cell growth and provide evidence of overwintering cell viability. Lines of evidence supporting algaecide efficacy for preventative treatments include (1) field studies demonstrating scalability and efficacy of algaecides against benthic algae, (2) data suggesting similar sensitivities of overwintering and planktonic Microcystis cells to a peroxide algaecide, and (3) a mesocosm study demonstrating a decrease in HAB severity following preventative treatments. This review informs data needs, monitoring techniques, and potential efficacy of algaecides for preventative treatments of overwintering cells.
  • Development of a Three-Dimensional Vegetative Loss Mechanism for the Geophysical Scale Transport Multi-Block Hydrodynamic Sediment and Water Quality Transport Modeling System (GSMB)

    PURPOSE: The US Army Engineer Research and Development Center’s (ERDC) Environmental Laboratory (EL) and Coastal and Hydraulics Laboratory (CHL) have completed several large scale hydrodynamic, sediment and water quality transport studies. These studies have been successfully executed utilizing the Geophysical Scale Transport Modeling System (GSMB), which is composed of multiple process models (Figure 1). Due to being directly and indirectly linked within the GSMB framework, the US Army Corps of Engineers (USACE) accepted wave, hydrodynamic, sediment, and water quality transport models are both directly and indirectly linked within the GSMB framework.