Evaluation of a Membrane Biological Reactor for Water Reclamation in a Land-Based Marine Recirculating Aquaculture Facility

Abstract

A recirculating aquaculture system can minimize water use, allowing fish production in regions where water is scarce and also placing the waterborne wastes into a concentrated and relatively small volume effluent. Operating a recirculating aquaculture system at high salinities for culture of marine species, then recovering the saltwater contained in the backwash effluent could allow for its reuse within the fish culture system and also reduce salt discharge to the environment. Membrane biological reactors (MBRs) combine activated sludge type treatment with membrane filtration. Therefore, in addition to removing biodegradable organics, suspended solids, and nutrients such as nitrogen and phosphorus, MBRs retain high concentrations of microorganisms and, when operated with membrane pore sizes < 1 micron, exclude microorganisms from their discharge. In this research, results indicated excellent removal efficiency (%) of TSS (99.65 ± 0.1 - 99.98 ± 0.01) and TVS (99.96 ± 0.01 - 99.99 ± 0.0) at all salinity levels. Similarly, a 3-4 Log₁₀ removal of total Heterotrophs and total Coliform was seen at all treatment conditions. Total nitrogen removal efficiency (%) ranged from 91.8 ± 2.9 - 95.5 ± 0.6 at the treatment levels and was consistent, provided a sufficient acclimation period to each new condition was given. Conversely, Total phosphorus removal efficiencies (%) at 0ppt, 8ppt, 16ppt and 32ppt salinity were 96.1 ± 1.0, 72.7 ± 3.5, 70.4 ± 2.3, and 65.2 ± 5.4, respectively, indicating reduced phosphorus removal at higher salinities.