Reducing phosphorus discharge from flow-through aquaculture: III: assessing high-rate filtration media for effluent solids and phosphorus removal

Abstract

Two types of unique high-rate filtration media, reticulate foam media of four porosities and Fuzzy filter® (FF) media (Schreiber Technologies, Trussville, AL, USA), were tested during bench top and field tests for potential application in flow-through (FT) mechanical filtration processes to reduce solid phase phosphorus (P) discharge. Bench top test screening was used to select medias for field testing based on the following criteria: (1) capable of particle size capture down to 100μm; (2) capable of hydraulic loading ≥2037Lpm/m2 [50gpm/ft2]; (3) initial clean bed head loss ≤ ∼152mm. Bench top results showed average particle size capture of 217, 161, 118, 69, and 51μm for the four porosities of reticulated foam tested and the FF media, respectively. Fuzzy filter® media was the only media that was unable to sustain the 2037Lpm/m2 hydraulic loading; therefore FF media was tested at a hydraulic loading of 1605Lpm/m2. The FF media was also the only media that which exhibited any measurable head loss during the 1h bench top tests, i.e. 17cm water. Based on these results the 30ppi reticulated foam was selected for a 16h field test to measure particle size capture, head loss, and the effect on solids and P discharge from commercial FT raceway effluent. The results indicated particle size capture of less than 100μm, a cumulative head loss of 150mm, and a 29% reduction in suspended solids and solid phase phosphorus discharge (11% total phosphorus discharge reduction) from the filtered effluent. The results support that the 30ppi reticulated foam is a suitable media for development in a high-rate filtration process for solids and phosphorus discharge reductions from FT raceway effluent.