9420.pdf

possibility for harm at some future time and place even when regulated to non-toxic
levels, ammonia exerts immediate toxicity (Lewis, 1988). Ammonia toxicity to aquatic
species is well documented. It is also widely recognized that ammonia toxicity is a
function of pH, temperature and concentration of degradable organic material in the
effluent (most often reported as BOD). Difficulties encountered in toxicity determination
include dissolved oxygen depletion during the test as a result of high BOD in the effluent,
and synergistic/antagonistic effects of ammonia and pH, temperature and BOD, as
discussed elsewhere (Lewis, 1988; Aquametrix, 1993a; NovaTec and EVS Environment
Consultants, 1994; NovaTec, 1994) and is beyond the scope of this report. Toxicity tests
are normally carried out without pH adjustment unless the pH of the test solution is
outside the range 5.5 to 8.5, and aeration is restricted to a minimal rate of 7.5 mL/minL-’
(Environment Canada, 1990).
Table 3.9 Toxicity of Effluents from Three Fish Processing Plants
Test Type Test Samples Failing Range
Toxicity Test
Acute Rainbow Trout 5of9 37- >100%
! (LC50) !
Acute I Ceriodaphnia Dubia I 8 of 10 I 0.5-> 100%
(LC50)
Chronic Ceriodaphnia Dubia 5of5 5- 60 %
(IC50)
Source: NovaTec and EVS, 1994
3.2.3 BOD Loading Estimate
Based on available BOD data, an attempt was made to estimate an order of magnitude
BOD loading associated with effluents discharged from all fish processing plants in B.C.
in 1993. To establish this estimate, BOD mass loadings (kg BOD/tonne of fish landed)
were calculated using monitoring data obtained from MOELP, the GVRD, the City of
Vancouver, and a previous NovaTec study (NovaTec and EVS, 1994). The data was
examined and determined to be logarithmically distributed. Consequently, the geometric
mean was selected as the most appropriate statistic upon which to estimate contaminant
loading. This estimate excludes the BOD contribution of wastewater from three plants
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