Pm. Chapman et al., A TRIAD STUDY OF SEDIMENT QUALITY ASSOCIATED WITH A MAJOR, RELATIVELYUNTREATED MARINE SEWAGE DISCHARGE, Marine pollution bulletin, 32(1), 1996, pp. 47-64
Sediment chemistry, toxicity and benthic community structure were used
individually and together (i.e. the sediment quality triad) to assess
the effects of screened but otherwise untreated sewage from a major c
ity, discharged to the marine environment via an offshore, deep water
outfall. Only two chemicals related to the outfall, mercury (probably
primarily from hospitals and dental offices) and 1,4-dichlorobenzene (
probably primarily from urinal deodorizers) were found in the sediment
s at concentrations of possible concern, up to 100 m away from the out
fall terminus. Sediment toxicity tests indicated that survival was not
a major problem, even at the outfall terminus; however, growth and de
velopment were reduced up to 100 m away from the outfall terminus, Ben
thic community structure followed the Pearson-Rosenberg model for orga
nic enrichment, with stations 100 m away from the outfall terminus typ
ical of moderately polluted conditions, Such minimal, highly localized
impacts to the receiving environment are not unexpected, since the re
ceiving environment is well flushed and mixed, and the city is not hig
hly industrialized. The results of this study raise questions concerni
ng generic decisions about sewage treatment where site- and situation-
specific conditions do not indicate a major problem, and source contro
l is a reasonable option.