Recycled Glass Cullet as an Alternative Beach Fill Material: Results of Biological and Chemical Analyses

Florida's critically eroded beaches pose a myriad of social and environmental concerns, prompting an effort to explore alternatives to more traditional sand sources. One alternative involves the use of recycled glass cullet as coastal beach fill in erosional “hot spots.” To determine the biological suitability of glass cullet in marine applications, invertebrate survivability and colonization was assessed through a biological assay program. Experimental bioassays were divided into five, three-container series (n = 15), with each series testing 23 kg of proportioned natural sand/glass cullet mixtures. Macro- and microscopic organisms were introduced to each bioassay and analyzed through direct observations. Experimental macrofauna displayed normal active behavior and recorded a mean success rate of 78% ± 3%. Mortality was attributed to predator-prey interactions rather than sediment contamination. Colonization of interstitial microfauna was successful within the cullet mixtures, and active transport between the cullet grains was documented without adverse effects. Abiotic parameters monitored in conjunction with the biological testing showed that temperature, dissolved oxygen, and pH did not differ significantly among each test series. In addition, ammonia, nitrites, nitrates, and organic phosphates all recorded low risk factor levels. Small amounts of hydrogen sulfide precipitate began to form in the absence of wave action, but when wave simulations were introduced, no microbial zonation was detected. These experiments indicate that recycled glass cullet is a biologically benign material that can be used to mitigate development of erosional hot spots in nourished beaches. By doing so, a proactive recycling program can be initiated to protect one of Earth's most valuable resources, the coastline.