Date of Award
Finding a new, clean, and sustainable energy source to replace fossil fuels is one of society’s most daunting challenges. Algae biomass is a promising renewable resource for biofuel production due to its efficient conversion of solar energy into chemical energy. Algal turf scrubbers (ATS™) systems mimic natural streams, flowing wastewater over hard substrates designed to encourage attached algae growth. This study focuses on the use of replicated ATS™ systems, because they are low maintenance, are effective for removing nutrient pollutants, model natural stream ecosystems, and can produce large volumes of harvestable algal feedstock for biofuel production. A challenge that occurs in ATS™ systems are grazers. Chironomid larvae graze on the algae, dislodging large portions of the algal turf reducing the efficiency of the system. Currently, pesticides are being used to control the midge larvae populations. Limited research is published in the area of non-chemical means of midge fly control. Dewatering is the non-toxic alternative proposed in this study. Three questions were discussed in this experiment. First, is dewatering the algae an effective method of midge larvae control? It was predicted that dewatering the algae would reduce the midges in the system. Second, does dewatering alter the algal biomass of the system? It was predicted that dewatering the algae would increase the algal biomass due to reduced grazing pressures from the midges. And lastly, was there a shift in the algal taxa community composition due to dewatering? It was predicted that the algal community would shift from predominately green algae to diatoms. The methods were based upon the Methods in Stream Ecology (Hauer and Lamberti 2006), and the EPA Inorganic Chemistry Unit Chlorophyll Spectrophotometric Protocol 150.1 (1991). Dewatering the algae effectively killed the midge larvae in the system as there was a 26% reduction between drying and control treatments. However, the algal biomass was negatively impacted as there was an 18% decrease, reflecting that although dewatering is an effective method of midge control, it reduces the productivity of the algae in the ATS™ system. There was not a significant shift in the algal taxa as shown by the proportions of chlorophyll b and c in the system.
Husted, Emily, "Effects of Short-Term Dewatering on Grazer Abundance and Algal Biomass in a Wastewater Treatment Algal Turf Scrubber" (2013). Theses and Dissertations. 124.