Environmental Engineering Reference
In-Depth Information
Primary Treatment (CEPT) which removes about 70% of the organics, 80% of suspended solids, and
50% of bacteria. The treated effluent is discharged through a 1.2 km long submerged outfall diffuser into
the western Victoria Harbor. The treatment works is designed for an average dry weather flow (DWF) of
around 19 m 3 /s (peak flow 40 m 3 /s). The partially-treated effluent is discharged via a 1.1 km long submarine
outfall into the western Victoria Harbor. The effluent is discharged into the tidal stream through 24
"rosette" risers installed along a 3.25 m diameter diffuser pipe, at a mean depth of around 12 m. Each riser
has 8 discharge ports of diameter 0.25 m. The buoyant plumes from the risers are sufficiently separated
and can be considered as independent of each other.
Fig. 8.67 Computational domain for Hong Kong waters model and Stonecutters Island sewage outfall
Ammonia is a principal pollutant in sewage effluent and one of the major pollutants in Hong Kong. At
elevated concentrations, ammonia is toxic to aquatic organisms and its toxicity is mostly related to
unionized ammonia NH 3 . For example, fish exposed to an elevated NH 3 concentration may suffer a loss
of equilibrium, hyperexcitability, coma, and even death. It is, therefore, important to consider the mixing
zone based on NH 3 , as it may pose threats to fisheries resources and marine bio-diversity in the vicinity
of the sewage outfall. In addition, elevated bacterial ( E.coli ) levels at nearby beaches are also a major
concern.
Search WWH ::




Custom Search