Author(s): K. M. Ho; H. Gerges; Stanley Lau; David Pickles; Zorro Yuen
Linked Author(s):
Keywords: Chemically enhanced primary treatment (CEPT); Primary sedimentation tanks; Primary clarifiers; Maximum treatment capacity; Computational fluid dynamic (CFD); Hydraulic model; Energy dissipating and flocculating baffles; Validation test
Abstract: The Stonecutters Island Sewage Treatment Works (SCISTW) – Stage 1, located in Hong Kong and presently the world’s largest chemically enhanced primary treatment (CEPT) STW, is being upgraded from the existing design capacity of 1. 7 million m3/day to 2. 45 million m3/day, with a maximum hydraulic peak factor of 1. 7. The SCISTW, is currently receiving preliminary treated effluent from urban Kowloon, Kwai Chung, Tsing Yi, Tseung Kwan O and North-Eastern Hong Kong Island via two (2) deep tunnel systems including some under harbor sections from the SCI Main Pumping Station (SCIMPS) and the Northwest Kowloon Pumping Station (NWKPS). It will also treat additional sewage collected from the North and South-West shores of Hong Kong Island conveyed from the new pumping station (Stage 2 Main Pumping Station) via the newly constructed deep tunnel system. As part of the major capacity expansion, the Drainage Services Department (DSD) initiated a number of studies on upgrading the existing primary sedimentation tanks (PSTs) to achieve maximum treatment capacity in an attempt to reduce the number of new PSTs required to be constructed. The optimization studies involved performing a series of detailed on-site data collections for the exisitng CEPTs as well as a review of the chemical coagulation and flocculation performance with a range of ferric chloride and polymer additions. Upgrading works options were simulated with computational fluid dynamic (CFD) PST process hydraulic model for evaluation of the improved process hydraulic capacities and performance of PSTs, and the best configuration was selected. The selected upgrade works were a series of interconnected energy disipating and floccuating inlet baffles of the PSTs which had an increased capacity as high as 20% . The use of CFD PST Modelling was proven to be a time- and cost-effective tool in the upgrading of the PST for maximized capacity and performance.
Year: 2013