Implications of aerated stabilization basin dredging on potential effluent toxicity to fish.
Benthal solids accumulated in aerated stabilization basins (ASBs) must be dredged to regain treatment capacity. While dredging restores treatment performance, it has been associated occasionally with the failure to meet regulatory effluent toxicity limits at the time of dredging. A first study of its kind was undertaken to investigate the implications of ASB dredging on potential effluent toxicity to fish. The study showed that benthal solid slurry removed from the quiescent zone of an ASB with a hydraulic dredge was toxic to rainbow trout with a 96-hour median lethal concentration (LC50) of 2.2%. The high ammonia concentration in the sample was the main cause of fish mortality. Hydrogen sulfide and resin and fatty acids also were present in the dredged material at concentrations that could cause fish mortality. These findings have led to best management practices that can be used to mitigate or eliminate fish toxicity issues during dredging operations.
Mahmood
Talat
T
FPInnovations-Paprican Division, Pointe-Claire, Quebec, Canada. talat.mahmood@fpinnovations.ca
Kovacs
Tibor
T
Gibbons
Sharon
S
Paradis
Jean-Claude
JC
D000641:Ammonia / Q000633:toxicity; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D005227:Fatty Acids / Q000633:toxicity; D006862:Hydrogen Sulfide / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000009:adverse effects*; D017686:Oncorhynchus mykiss; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010209:Paper; D012116:Resins, Plant / Q000633:toxicity; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D014877:Water Pollution, Chemical / Q000331:legislation & jurisprudence / Q000517:prevention & control
D005227:Fatty Acids; D007220:Industrial Waste; D012116:Resins, Plant; D014874:Water Pollutants, Chemical; D000641:Ammonia; D010100:Oxygen; D006862:Hydrogen Sulfide