A Comprehensive Analysis of Marine Recirculating Aquaculture Effluent Treatment

The development of marine aquaculture is limited by the cost of coastal land and the inherent limitations in the management of saltwater effluent. Greater oversight of nutrient discharge has brought about the need to develop ecologically-sound wastewater treatment systems for marine aquaculture. To promote further development of marine aquaculture, a renewed focus on the capture and storage and a reduction in the cost of treatment of the saline wastewater is required such that facilities may be located further inland.;The Marine Aquaculture Research Center (MARC) was developed for the purpose of promoting marine recirculating aquaculture research and is operated by the Department of Biological and Agricultural Engineering at North Carolina State University. The MARC utilizes recirculating aquaculture systems (RAS) for all ongoing marine aquaculture research inside the facility. All effluent from the ongoing RAS operations is treated in a multi-stage wastewater treatment facility prior to discharge or reuse of the treated effluent. The wastewater treatment system consists of a primary solids removal stage and a dissolved nutrient treatment stage. The primary solids removal stage employs a geotextile bag system using a flocculant-aid to improve solids removal from the waste stream. The dissolved nutrient treatment stage consists of two separate biological treatment systems: a conventional biological filtration system and a constructed treatment wetland system. Each system is separate and was evaluated to determine the treatment performance using marine aquaculture effluent.;Geotextile bag systems using flocculant-aids offer a low cost, low energy, highly efficient means for capturing and dewatering waste solids from a RAS effluent. Two separate geotextile bag systems were evaluated using either freshwater or marine RAS effluents. The results were compiled to provide consistency and determine any potential differences between marine and freshwater systems. Results from the two separate geotextile bag systems were similar and showed excellent nitrogen, chemical oxygen demand (COD), total suspended solids (TSS), and phosphorus removal. The resulting filtrate was high in total Kjeldahl nitrogen (TKN) and soluble reactive phosphorus (SRP).;The conventional biological filtration system is a two-stage reactor system operated in series employing an anoxic fixed bed bioreactor (FBBR) and an aerobic mixed bed bioreactor (MBBR), operated in triplicate. The treatment system effectively converted and removed nitrogen at a suitable rate to support the ongoing operations inside the facility. The study provided both realistic TN removal rates as well as operational COD:TN ranges for maximizing the efficiency and performance of the FBBRs.;The second dissolved nutrient treatment system was a two-stage constructed treatment wetland system employing a combination of subsurface vertical flow (VF) and free water surface (FWS) flow wetland cells, each operated in triplicate. Variation of treatment performance was observed due to seasonal effects. The constructed treatment wetland system successfully treated the wastewater prior to discharge. A portion of the treated effluent was successfully reused in a 1.5 m3 marine RAS growing Hybrid Striped Bass (Morone saxatillis ).;The dissertation presented herein is a series of three separate manuscripts written for the purpose of publication upon the completion of the doctoral degree program. The first manuscript details the work using the geotextile bag systems for the purpose of solids removal and dewatering for RAS. The second manuscript details the denitrification and nitrification processes utilized in the two-stage biological reactor system and the limitation excess organic carbon may impose on the removal of TN. The third manuscript is an evaluation of a constructed treatment wetland system treating the effluent from a marine RAS facility. Each of the studies described in this dissertation provide a unique understanding of the required wastewater treatment processes for marine recirculating aquaculture.