On February 18, 1993, water and sediment in the expected zone of influence from the Annacis Island Sewage Treatment Plant (STP) was sampled. Water column samples were collected at the surface and at a depth of four metres. Significant findings of the work were: (1) an outflowing tide was experienced for the entire sampling time, which would result in samples being taken at a time when there were not stagnant water conditions or flow reversals; (2) the most elevated ammonia concentrations were noted with the depth samples 25 and 100 metres downstream from the point of discharge; (3) all the ammonia values were less than the MoE criteria to prevent chronic effects; however, the highest measured concentrations were about one third of this criterion; (4) the MoE water quality criteria for bacteriological indicators were usually not achieved at sites either upstream or downstream from the effluent discharge; (5) for all bacteriological variables and ammonia, the higher concentrations were associated with depth samples; (6) three PAHs (phenanthrene, anthracene, and chrysene) in sediments from a site 200 metres downstream from the outfall exceeded certain MoE water quality objectives; and (7) The solid phase microtox toxicity test showed the greatest toxicity to be associated with the sediments collected 200 metres downstream from the effluent discharge.
Swain, L.G., Walton, D.G.. 1993. A Preliminary Assessment of the Greater Vancouver Sewerage and Drainage District Annacis Island Sewage Treatment Plant Effluent Discharge Impact. BC Ministry of Environment, Lands and Parks
Topic: Solid or Liquid Waste
Keywords: dilution, concentration, effluent
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