According to Oxford Advanced Learner's Dictionary, the word "trace" means very small amount. You may ask, "How small is small?" The following questions bring you the answer.

The first question, "What is the major component of water?" The answer is of course water molecules no matter whether you are in the space shuttle Discovery or on the Third Rock from the Sun. There are about 1000 grams of water molecules in one litre of water at room temperature and atmospheric pressure. Next question, "What are the minor components in your drinking water?" The answer is nutrients or minerals which are good to your health. There is about 0.1 gram of these useful matters. For trace amount of chemicals in water, we are talking about 0.000001 gram (microgram) or less of matters in a litre of water. Such amount is so "trace" that no one can see it. How are we going to analyze accurately?

Determination of trace chemicals in water demands an effective quality assurance system, a team of qualified and competent chemical analysts, a diversity of advanced and sophisticated instruments, a group of sensitive testing methods and a driving force for continuous improvement. These five pre-requisites are the essential elements for the operation of the two Development Sections (D(1) and D(2)) in the Water Science Division.

One of the key tasks of the Development Sections is the monitoring of trace chemicals in water. Each Section is led by a Waterworks Chemist who supervises eight Engineering Laboratory Technicians (I & II) and Laboratory Attendant. Section (D1) is mainly responsible for the analysis of trace organic chemicals, while Section (D2) is responsible for the analysis of trace metals and miscellaneous organic chemicals. The two Sections are operating in the Mainland East Laboratory at Sha Tin Treatment Works.

Water Science Division implements an effective laboratory quality assurance system in compliance with the technical and laboratory management criteria meeting the requirements of ISO 17025. Mainland East Laboratory has been an accredited laboratory under The Hong Kong Laboratory Accreditation Scheme (HOKLAS) since 1996. The primary objectives of the Scheme are to identify and recognize competent testing and calibration laboratories in Hong Kong. Laboratory operations and activities are regularly audited internally and externally by HOKLAS. These auditing procedures ensure that our quality assurance system is strictly implemented. After years of development and improvement, the two Development Sections have become one of the competent analytical teams in the global water industry. Since June 1999, the Water Science Division has been capable of analyzing all 94 trace chemicals of health significance stipulated by the World Health Organization. It has further enhanced the assurance as to the high quality of our treated water.

To maintain the quality of our analytical service, staff are required to participate in inter-laboratory proficiency testing organized by institutes of international standing. Water Science Division also regularly invites reputable overseas laboratories in Australia (NATA accredited), New Zealand (IANZ accredited) and U.K. (UKAS accredited) for performance benchmarking exercises. Water samples are analyzed by our staff as well as other participating laboratories for a variety of trace chemicals. Our staff have the opportunity of sharing valuable experiences in water analysis with overseas laboratories. In a few occasions, the participating laboratories expressed their gratitude for our testing results and recommendations which have led to the improvement of their analytical procedures.

At present, there are thirteen sets of modern analytical instruments installed in the Mainland East Laboratory for trace chemical analysis. For optimum system performance, these delicate and expensive "babies" are always housed in an environment with controlled temperature and humidity as required by our stringent quality assurance system. Instruments are calibrated and maintained in tip-top condition by our experienced laboratory technicians. Our technicians are not just chemical analysts, but they also possess sound knowledge and hands-on experience on chemical instrumentation. Chemical technicians are encouraged to troubleshoot analytical instruments prior to seeking repair services. Instrument faults can therefore be identified quickly so that instrument downtime is reduced to minimum. Preventive maintenance and corrective actions are taken timely.

Sensitive testing methods are as equally important as expertise and instrumentation in trace chemical analysis. In the Mainland East Laboratory, team members play mixed roles in testing method development. Chemist conducts literature survey on published testing methods from international organizations or scientific journals. We always remain conscious of our responsibilities towards the environment during method selection. New methods and procedure have been employed for sample preparation in order to minimize the use of organic solvent. The most widely adopted analytical procedures in our laboratory are United States Environmental Protection Agency (USEPA) methodologies. Chemist and laboratory technicians work together closely in designing experiments, carrying out experimental trials, recording observations and analyzing test results. New testing methods must be validated in-house before use by our technicians so as to confirm that the methods are fit for the intended use. Technicians, the high-user of the testing methods, also take part in writing up analytical steps which will become part of the analytical method manuals. Testing methods finalized by Chemist are issued for daily use after the approval from Quality Assurance Unit. Comments and feedback from technicians are often adopted for continuous improvement and streamlining of operating procedures.

In our laboratory, all technicians are trained and qualified for conducting two or more instrumental methods independently. They are also capable of operating at least two different instruments. Gradually, we have built up a strategic pool of technical competence with team members who can back up each other. Staff are always staying alert and are prepared to maintain our quality services in any case of exigency. Furthermore, about 50% of the technicians in the Development Sections are science degree holders. Some technicians also pursue their postgraduate studies using their own time to further broaden and update their knowledge on modern analytical chemistry. Self-development and their perseverance create a sustainable driving force for continuous improvement.

Everyday, huge amount of raw data, analytical results and water quality data are generated in our laboratory. This information is all captured and archived in our database system. User-developed spreadsheet macros are developed and used for data analysis and quality control purposes. Recently, with the assistance of Information Services Unit (ISU) of WSD, we are happy that water quality data are now available on the Internet for public information.