A preliminary assessment of the potential impacts of seafood processing effluent on the aquatic environment

The purpose of this study was to conduct a preliminary assessment of the potential impacts of Atlantic Canadian seafood processing effluents on the aquatic environment. Specifically, effluent samples from American Lobster, Jonah Crab, Snow Crab, Yellowtail Flatfish and Atlantic Salmon plants were collected and characterized for biochemical oxygen demand (BOD5), chemical oxygen demand (COD), turbidity, total suspended solids (TSS) and ammonia nitrogen (NH3-N). The flatfish and salmon effluents were also characterized for adsorbable organic halides (AOX), soluble BOD 5, and soluble COD. Bench-scale testing with sedimentation (SED) and dissolved air flotation (DAF) using aluminium sulphate (alum) was conducted with each of the effluents to examine contaminant reduction capabilities of these treatment technologies. Bench-scale testing with ultra-filtration (UF) membrane filtration was also conducted with the lobster and Jonah Crab effluents. Samples of the flatfish and salmon effluents were filtered through a 25-mesh screen to evaluate existing guideline requirements for fish processing effluent treatment. Raw effluent acute aquatic toxicity for the flatfish and salmon effluents was assessed using the Acute Lethality Test using Threespine Stickleback or Rainbow Trout and the Toxicity Test using Luminescent Bacteria, commonly known as Microtox(TM). In addition, the effectiveness of DAF in removing acute toxicity from these two effluents was evaluated using the Microtox test.; Effluent BOD5 concentration ranged from 179 to 276 mg/L, COD concentration ranged from 458 to 1717 mg/L, turbidity ranged from 28.8 to 88.3 NTU, TSS concentration ranged from 27.2 to 120.1 mg/L and NH3-N concentration ranged from 1.5 to 12.9 mg/L. AOX concentrations for the flatfish and salmon processing effluents were 3.2 and 0.4 mg/L respectively. Cleanup shift AOX concentrations for the same effluents were 3.5 and 0.5 mg/L respectively. Treatment by SED, DAF and OF was successful in reducing contaminant concentrations with maximum observed percent reductions for BOD5 of 90%, 60% for COD, 99% for turbidity, 95% for TSS, and 50% for NH3-N. Bench-scale 25-mesh screen runs showed poor reduction efficiencies for BOD5, COD, NH3-N, TSS and turbidity. The salmon effluent failed the Acute Lethality Test using Rainbow Trout while the flatfish effluent showed acute toxicity in the Microtox test with a 50% Inhibiting Concentration (IC50) of 38.84%. Subsequent treatment by DAF of the flatfish and salmon effluents increased IC50 values by 20 and 26% respectively.; The findings of this study indicate that all of the processing effluents sampled showed characteristics that could potentially degrade effluent receiving waters. Filtration through a 25-mesh screen appears to provide inadequate removal of contaminants. SED and DAF using alum as well as OF were effective at removing solids but less effective at removing soluble effluent components. Improved performance may be possible with further treatment technology optimization on an effluent specific basis. Acute toxicity was demonstrated in the two raw finfish effluents. Application of DAF treatment was successful in significantly increasing Microtox IC50 values, thereby reducing acute toxicity, but failed to entirely remove acute toxicity.