Abstract
Demand of marine aquaculture has risen worldwide with human population growth and need for reliance on a steady protein supply. Direct discharges from on-land marine aquaculture systems are exceptionally high in nitrogen and phosphorous, which have negative impacts to downstream waters leading to eutrophication. Bioremediation methods using biodegradable plastic applications were explored through this thesis; a closed marine recirculating aquarium system (RAS) and using two different biodegradable plastic media in a bioreactor system and a marine aquaculture effluent from pinfish (Lagodon rhomboides) and wetlands using a vertical-flow (VFTW) and floating treatment (FTW) construction. The objectives explored were to; apply ecological engineering techniques for the treatment of nutrient rich marine aquaculture effluent, determine the nitrogen and phosphorous removal rates from these systems, and to determine the impact of biodegradable plastics on microbial community composition. In the marine RAS study, the TN removal efficiency was 92.1-98.5% with the use of biodegradable plastic, polycaprolactone (PCL) and polyhydroxyalkanoate (PHA), and an ASN medium and 61.5-62% TN removal efficiency with pinfish effluent. TN removal efficiency was shown to be greater with biodegradable plastic than a nonbiodegradable plastic control for both conditions. Alternatively, use of a biodegradable plastic (PCL) as an external carbon input to a treatment wetland showed minimal increases in TN retention in a FTW system with greater efficiency effects shown between wetland construction, the VFTW system showed an increased TN, 87-91%, and TP, 74-81%, nutrient retention compared to the FTW system. The use of biodegradable plastic for treatment of high nutrient marine aquaculture effluent was shown to be effective and this technology can be used on a larger scale application for sustainable wastewater treatment practices.
