Response Of Water Quality To Sewage Abatement In Tolo Harbour

Abstract

Nowadays, with the increase in urban population, the amount of urban waste has also increased significantly, and marine discharge is one of the ways to solve the problem of urban waste. Before 1998, large amounts of waste, up to 2.5 × 105 kg swage (Broom et al., 2003), were entering Tolo Harbor and Channel through sewage pipes and severely affecting the quality of seawater around it. Causing Tolo Harbor becomes a eutrophic water zone. Therefore, among the areas with recorded red tide events in all waters of Hong Kong, Tolo Harbor has the most frequent red tide events (Yin, 2003; Wong et al., 2009). After 1998, due to the cessation of sewage discharge from Hong Kong to Tolo Port, the water quality of Tolo Port gradually improved. An in-depth study was conducted using 21 years of data from monthly long-term water quality monitoring to determine the ecological remediation of Tolo Harbor and Channel and the environmental impacts of waste reduction following the implementation. At the same time, considering the influence of seawater salinity, the study consulted data from the Hong Kong Meteorological Observatory and added rainfall as a factor affecting the water body. The results showed that the amount of phytoplankton in this sea area has declined year by year since the cessation of sewage discharge. So that pollution-fighting measures were achieving their goals. Algal growth in Tolo Harbor and Channel is driven primarily by nutrients rather than freshwater and hydrodynamic erosion. To reduce the effects of algal blooms in freshwater with gradually less erosion, it is best to focus on phosphorus removal during the summer. In other cases, concentration of nutrient removal is not necessarily due to the important role of hydrodynamic mixing.