Application of theWATERMAN Real-time Coastal Water Quality Management System to Environmental Engineering and Control

Bathing beaches are invaluable marine resources for Hong Kong and the protection of public health is of utmost importance. The Harbour Area Treatment Scheme (HATS) is the sewage collection and treatment scheme that serves the urban areas of Hong Kong on both sides of Victoria Harbour. The sewage receives Chemically Enhanced Primary Treatment (CEPT), and the treated sewage flow (1.4×106 m 3 /d) is discharged through a 1.2km outfall in the western Victoria Harbour. Since March 2010 the additional provision of chlorination to the treated effluent has brought significant water quality improvements to the neighbouring Tsuen Wan beaches. The WATERMAN Real-Time Coastal Water Quality Management System has been applied to formulate a disinfection dosage control strategy. A comprehensive investigation on the relationship between beach water quality, bacterial standard of effluent discharge and environmental conditions has been carried out using the extensively validated WATERMAN 3D hydrodynamic model. Detailed numerical simulations for an entire average wet year demonstrate that the Water Quality Objectives (WQO, E.coli < 180 count/100mL) can be met in the coastal receiving waters for an effluent E.coli standard of 200,000 counts/100mL for HATS Stage 2A (Q = 1.8×106 m 3 /d). The setting of an appropriate discharge standard will help to optimize the chlorine dosage, reduce energy consumption and operation cost whilst preserving the protection of the water quality of beaches, seawater intakes and other sensitive receivers. The WATERMAN system has also been applied for emergency response in pollution accidents and development of operational strategies.