(278i) Algae-Derived Activated Carbon Materials for Phosphorus Removal from Surface Waters

Algae are important contributors to marine life, the food web, and dissolved oxygen levels in surface waters. However, high nutrient levels (e.g., nitrogen and phosphorus) and warm temperatures in surface waters can enhance the overgrowth of certain algae types, forming foam- or scum-like masses known as Harmful Algae Blooms (HABs). When pushed to shore by wind, wave action, tides, and currents, HABs release toxins such as cyanotoxins, brevetoxins, and hydrogen sulfide, causing a wide range of health issues in people, animals, and the ecosystem. Apart from the environmental issues and adverse health impacts, HABs also cause economic pain related to the associated healthcare costs, the required clean-up activities, and losses in tourism revenues. Consequently, further research is needed to mitigate the adverse environmental, societal, and economic impacts associated with HABs. This study investigated an industrial ecology approach for mitigating HABs. Industrial ecology is a developing framework that attempts to reduce the environmental impacts of human activities via emulating the interconnections and interactions of natural ecosystems. Nature is a closed-loop system where all waste produced is used as substrates for other organisms or processes. The overarching objective was to convert nuisance algae collected from impaired surface water bodies into designer adsorbent materials for the removal of aqueous-phase phosphate. Cyanobacteria was collected from Lake Okeechobee, processed using fast, energy-efficient microwave heating (i.e., synthesis duration of less than 10 minutes), and converted to activated carbon adsorbent material. The surface of the adsorbents was modified using different compounds, namely lanthanum chloride and zinc chloride, to improve phosphate removal. The adsorbents, with and without modification, were evaluated for phosphate uptake to identify promising materials for further assessment. Multiple materials which were all modified with lanthanum chloride achieved near-complete phosphorus removal efficiency (99%+) over a wide range of concentrations (5, 10, and 20 mg/L) at low adsorbent dosages (below 1 g/L) and short contact times (90%+ removal in less than 30 minutes). In summary, cyanobacteria biomass was upgraded to adsorbent materials designed for effective aqueous-phase phosphate removal. The project findings showed the potential of the proposed approach to battle HABs through nutrient removal, particularly adsorption of aqueous phosphorus from surface waters. Once implemented at large scale, the project results are expected to improve our socio-economic and environmental well-being, contributing to all sustainability pillars: society, environment, and economy. The outcomes not only enhance air and water quality and public health in communities across Florida, but also help develop a thriving recreation/tourism industry.