_{Appendix 3.1      Hydrogen Sulphide Survey}

_{1                 Introduction}

 

_{A gaseous hydrogen sulphide (H2S) survey was conducted for the Tai Po STW.  Odour generating facilities of the plant were identified and ambient H2S level around the plant was also identified in this survey.  H2S measurement was conducted at five typical working days between 20th January and 8th February 2003.  This Appendix presents the monitoring methodology and results of the survey .}

_{2            Survey Methodology}

_{2.1             Ambient Monitoring Locations}

 

_{Ambient H2S survey was conducted at six receivers (S1-S6) around the Tai Po STW plant.  Location of ambient survey is shown in Figure A3.1.}

 

_{Table A3.1a  Ambient Monitoring Station}

 

Location	Description	Monitoring Height (m)
S1	Interpac Containers Ltd	1.5m, 4m
S2	Talcon Industrial Ltd	1.5m, 4m
S3	Watson’s Water Centre	1.5m, 4m
S4	Tai Po Shuen Wan golf practice range	1.5m
S5	Tai Po Waterfront park	1.5m
S6	Government staff quarters	1.5m, 4m

 

_{2.2             Measurement Methodology}

 

_{H2S concentrations were measured at five typical working days between 20th January and 8th February 2003 for each monitoring location.  Sampling was conducted at every three hours for a duration of 24 hour on each monitoring day (i.e. 8 samples per day per location).}

 

_{Gaseous samples were collected at 1.5m and/or 4 m above ground.  Air sample was drawn into a teflon air bag under action of sampling pump at a rate of about 1 litre/min.  The air bag samples were sent to the laboratory for analysis within 12 hours.  The H2S sampling and analysis was conducted in accordance with the ISC 3rd edition 701 Determination of Hydrogen Sulphide Content of the Atmosphere in “Method of Air Sampling and Analysis”.  The detection limit of the method was 1 ppb H2S in air.}

 

_{Patrol of H2S of Tai Po Industrial estate was also conducted.  A portable H2S analyser, type Jerome 631-H2S, was employed for the patrol.}

 

_{Hourly meteorological data including wind speed, wind direction and ambient temperature were also collected during the monitoring period.} 

 

_{2.3             Data Validation}

 

_{The following data would be rejected to ensure the validity of the data collected.}

 

_{·            sample collected during raining period;}

_{·            the facilities was under maintenance or operated under abnormal condition; and}

_{·            condensate formed inside the teflon air bag.}

 

_{3                 Survey Results}

 

_{Ambient H2S survey was conducted and the results are summarised in Table A3.1b. Detailed results of ambient H2S survey are in shown in Table A3.1c.  During the monitoring period, wind speed up to 6 m/s was recorded, with the temperature ranged between 11oC and 24oC.}

 

 

_{Table A3.1b Summary of H2S Survey at ASRs}

 

Location	Description	H2S Concentration (ppb) (1)
		Max	Min	Mean
S1	Interpac Containers Ltd	126 / 88	1 / 1	24 / 20
S2	Talcon Industrial Ltd	52 / 51	0 / 1	11 / 11
S3	Watson’s Water Centre	92 / 99	1 / 1	11 / 10
S4	Tai Po Shuen Wan Golf Range	12 / -	0 / -	4 / -
S5	Tai Po Waterfront Park	57 / -	1 / -	9 / -
S6	Government staff quarters	113 / 42	2 / 2	15 / 12

_{(1)                        Concentration at 1.5m/4m.}

 

_{A patrol of the H2S was conducted for the Tai Po Industrial area.  It is identified that the wastewater and sludge treatment tanks of Tai Po STW were the major H2S source of the area.}