Investigations and improvement of operational and maintenance problems in Hong Kong municipal wastewater treatment plants

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Investigations and improvement of operational and maintenance problems in Hong Kong municipal wastewater treatment plants


Author: Hong, Chi-man
Title: Investigations and improvement of operational and maintenance problems in Hong Kong municipal wastewater treatment plants
Year: 2000
Subject: Sewage disposal plants -- China -- Hong Kong -- Management
Sewage disposal plants -- China -- Hong Kong -- Maintenance and repair
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Civil and Structural Engineering
Pages: 88, [97] leaves : ill. (some col.) ; 30 cm
Language: English
Abstract: This dissertation aims to investigate the common operational and maintenance problems in Hong Kong municipal sewage treatment plants and establish the required upgrading and improvement measures. This project started with site investigations which include visiting various large and medium sizes municipal sewage treatment works in Hong Kong, and review of recent technical papers and reports on pilot tests and testing and commissioning results. Having identified the operational problems in various areas, further discussions with operational staff were performed in order to find out the causes of these operational problems and then the solutions. This dissertation gives broad idea of the common operational problems appeared in municipal sewage treatment works rather than detailed information of a specific study. The major operational problems identified are: (i) Odor problem occurs in the preliminary treatment and sludge treatment facilities. The 'open to air' design allows serious emission of odor gases. (ii) Sludge bulking and foaming occurs in Tai Po and Sha Tin Sewage treatment works. It normally happens in the presence of readily biodegradable substrate, low F:M ratio and seasonal changes. (iii) Most of the municipal secondary sewage treatment plants encounter with difficulties in process control as the conventional design of activated sludge process requires manual control of process parameters and labor intensive operation of plant. (iv) The moving parts of submersed mechanical equipment is subject to excessive wear and tear and serious corrosion, and thus frequently breaks down. (v) As the results of labor intensive and land intensive design, the plant management also encounters with a lot of problems in respect of managing different major construction and upgrading projects running in parallel, and staff training. All of them would affect the performance of sewage treatment plants by deteriorating the effluent quality, increasing operation and maintenance costs and causing adverse effects on the public. Upgrading works would only minimize their effects but could not remove the causes. When these facilities are approaching to their end of design life, operational and maintenance problems will become much more serious and their effects on the plant performance will become apparent. The solutions to these operational problems include: (i) employing zero emission design of plant layout; (ii) addition of selector to aeration basin for control of sludge bulking and foaming; (iii) using on-line monitoring instruments and intelligent software to facilitate process control; (iv) as far as possible avoiding use of submersed electrical and mechanical equipment; and, (v) providing proper training to operational staff and better project management of on-going contracts. With the rapid advancement of technologies, the modern sewage treatment plant has become much more compact, simple, flexible, efficient and environmentally friendly. Hence, the construction of new plants and extension of existing plants are not necessary following the old designs even though they are proven success in some aspects. Compact and modular system equipped with intelligent process control (e.g. Seghers Unitank system) providing adaptation to changes in influent characteristics and hydraulic load can be a better option for the design of new plants and the extension stage of existing plant. Also, housing all treatment units within building provided with deodorizing system would be a much more environmentally friendly design.

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