TABLE OF CONTENTS
1.2. Objectives of the monitoring
3. Odour Patrol Monitoring Result
3.2. Meteorological Conditions
3.3. Odour Patrol Result Discussion
4. Summary of Odour Patrol Result
4.4. Follow-up Action for Exceedance Recorded in January 2022
6.1. Odour Concentration and Odour Emission Rate.
6.2. Odour Measurement Result Discussion
7. Summary of Odour Measurement
7.3. Follow-up Action for Exceedance Recorded in January 2022
LIST OF TABLES
|
Table 2.1 |
Odour Patrol Monitoring Locations |
|
Table 2.2 |
Description of Odour Intensity Levels |
|
Table 3.1 |
Summary of the Odour Patrol Results |
|
Table 3.2 |
Action / Limit Levels of the Odour Patrol |
|
Table 3.3 |
Comparison between Baseline Data and Impact Data of Odour Patrol |
|
Table 4.1 |
Event/Action Plan for Operation Air Quality Monitoring |
|
Table 4.2 |
On-site Observation |
|
Table 5.1 |
Odour Monitoring Locations for Odour Measurement |
|
Table 6.1 |
Summary of Odour Emission Rate |
|
Table 6.2 |
Comparison between Impact Monitoring Data and Data Obtained from EIA and Baseline Monitoring Data |
|
Table 6.3 |
Action / Limit Levels of the Odour Measurement |
|
Table 7.1 |
Information of the Portable H2S Meter |
|
Table 7.2 |
Summary of H2S Readings of Portable Equipment and In-house H2S Sensors |
|
Table 7.3 |
In-house H2S Concentration from Sensors and Odour Concentration from Odour Measurement |
LIST OF APPENDICES
|
Layout of Odour Patrol Monitoring Locations |
|
|
Odour Certificates |
|
|
Field Record and Photo Record |
|
|
Meteorological Information from the Hong Kong Observatory Station |
|
|
Layout of Odour Monitoring Locations for Odour Measurement Odour Measurement Result Total Odour Emission Rate Extracted from EIA Report |
|
|
Investigation Report |
|
|
Calibration Certificate of Portable H2S Meter |
LIST OF GRAPHS
|
Graph 1 |
Overall Correlation between Odour and H2S Concentration |
1.1.1. Bestwise – Sun Fook Kong Joint Venture (the Contractors) appointed 3NV Technology Limited (3NV) to undertake the Odour Monitoring for the Operational Phase of the Harbour Area Treatment Scheme Stage 2A (hereafter referred to as “the Project”).
1.1.2. The Project is reference to Environmental Permit No. EP-322/2008/G issued on 9th May 2014 by the Environmental Protection Department (hereinafter called EPD) to the Drainage Services Department (hereinafter called the DSD) as the Permit Holder and the EM&A Manual for the HATS Stage 2A.
1.1.3. The odour measurement and odour patrol shall be conducted in the first five years upon commissioning of the expanded SCISTW. For the 1st year, odour monitoring shall be conducted every three months. For the 2nd to 5th year, if the monitoring results from the 1st year comply with the requirements stated in Section 2.38 and Section 2.41 of EM&A Manual, the frequency of the monitoring could be reduced to once every 6 months subject to EPD’s approval.
1.2.1. The objective of odour patrol and odour measurement is to compare the result obtained from the operational phase with the baseline data at the designated points in order to determine the impact from the operation.
1.3.1. The purpose of the odour monitoring report for the operational phase is to provide analysis and graphical presentation to determine if there are any changes of odour impacts with respect to the implementation of HATS Stage 2A.
2.1.1. An odour patrollist with at least 3 independent trained personnel / competent persons, will be provided to conduct the odour patrol work at 23 designated odour monitoring locations and at the site boundary of 8 PTW and the SCISTW. The patrollist will be “calibrated” with reference to European Standard Method: BS EN13725 to ensure the patrollist odour sensitivity within 20-80 ppb/V. The Odour Certificates are shown in Appendix B.
2.1.2. The monitoring shall not be conducted on rainy days. Meteorological conditions including ambient temperature, relative humidity, wind speed and wind direction will be recorded with photo showing the sampling locations during each monitoring.
2.1.3. The independent trained personnel / competent persons shall:
- have their individual odour threshold of n-butanol in nitrogen gas in the range of 20 to 80 ppb/v required by the European Standard Method (EN 13725).
- be at least 16 years of age and willing and able to follow instructions.
- be free from any respiratory illnesses.
- be engaged for a sufficient period to build up and monitor/detect at several monitoring location;
- not be allowed to smoke, eat, drink (except water) or use chewing gum or sweets 30 min before and during odour intensity analysis;
- take great care not to cause any interference with their own perception or that of others by lack of personal hygiene or the use of perfumes, deodorants, body lotions or cosmetics;
- not communicate with each other about the results of their choices.
2.2.1. Odour Patrol shall be conducted every three months for the first year of operation for 8 PTWs and expended SCISTW. The first odour monitoring shall be conducted within one month, after the operation of the upgraded PTWs and expended SCISTW. Subsequent odour monitoring shall be conducted at the 4th, 7th and 10th month.
2.3.1. According to section 2.23 of the EM&A Manual, odour patrol monitoring will be conducted at the odour monitoring locations listed in Table 2.1 and at the site boundary of 8 PTWs and SCISTW.
2.3.2. The layout of odour patrol monitoring locations is shown in Appendix A.
Table 2.1 Odour Patrol Monitoring Locations
|
ASR ID in EIA Report |
Monitoring Station ID |
Location |
|
NP3 |
OM_NP1 |
King’s Road Playground & Skating Area |
|
NP4 |
OM_NP2 |
Customs HQ Tower (planned) |
|
NP5 |
OM_NP3 |
K. Wah Centre |
|
WC3 |
OM_WC1 |
Society for the Prevention of Cruelty to Animals |
|
WC4 |
OM_WC2 |
Rest Garden near Wan Chai Interchange |
|
C1 |
OM_C1 |
Sheung Wan Fire Station |
|
C2 |
OM_C2 |
Water Front Divisional Police Station |
|
C3 |
OM_C3 |
Sheung Wan Gala Point |
|
FM2 |
OM_FM1 |
Western Wholesale Food Market |
|
SB1 |
OM_SB1 |
University of Hong Kong Stanley Ho Sports Centre Pitch |
|
SB2 |
OM_SB2 |
Home for the Elderly |
|
SB3 |
OM_SB3 |
Maclehose Medical Rehabilitation Centre |
|
SB4 |
OM_SB4 |
The Duchess of Kent Children’s Hospital |
|
CB1 |
OM_CB1 |
Cyber Centre |
|
CB2 |
OM_CB2 |
Le Meridien Cyberport |
|
WF2 |
OM_WF1 |
Wah Ming House, Wah Fu Estate |
|
AB4 |
OM_AB1 |
Dairy Farm Ice and Cold Storage |
|
ALC3 |
OM_ALC1 |
Shell Ap Lei Chau Depot |
|
SCI1 |
OM_SCI1 |
Government Dockyard Offices |
|
SCI3 |
OM_SCI2 |
COSCO Hit Terminal |
|
SCI4 |
OM_SCI3 |
KMB Depot Office |
|
SCI5 |
OM_SCI4 |
Planned FSD Diving Rescue and Diving Training Centre |
|
SCI6 |
OM_SCI5 |
Club House |
2.4.1. During the patrolling, the meteorological and surrounding information are recorded:
- the prevailing weather condition;
- the wind direction;
- the wind speed;
- location where odour is spotted;
- source of odour;
- perceived intensity of the odour;
- duration of odour; and
- characteristics of the odour detected
- some relevant meteorological data such as daily average temperature, and daily average humidity, on the day of odour patrol should be obtained from the nearest Hong Kong Observatory station for reference.
2.4.2. The perceived intensity is to be divided into 5 levels which are ranked in a descending order as shown in Table 2.2.
Table 2.2 Description of Odour Intensity Levels
|
Odour Level |
Odour Intensity |
Classification Criteria |
|
0 |
Not detected |
No odour perceives or an odour so weak that it cannot be easily characterised or described |
|
1 |
Slight |
Slight identifiable odour, and slight chance to have odour nuisance |
|
2 |
Moderate |
Moderate identifiable odour, and moderate chance to have odour nuisance |
|
3 |
Strong |
Strong identifiable, likely to have odour nuisance |
|
4 |
Extreme |
Extreme severe odour, and unacceptable odour level |
3.1.1. The odour patrol monitoring result on 29th April 2022 is summarized in Table 3.1. The field record and photo record at the ASRs during the patrols are attached in Appendix C.
Table 3.1 Summary of the Odour Patrol Results
|
Monitoring Location |
Odour Patrol Member |
||
|
O-1 |
O-2 |
O-3 |
|
|
Odour Intensity (0 to 4) |
|||
|
OM_NP1 |
0 |
0 |
0 |
|
OM_NP2 |
0 |
0 |
0 |
|
OM_NP3 |
0 |
0 |
0 |
|
North Point PTW Boundary |
0 |
0 |
0 |
|
OM_WC1 |
0 |
0 |
0 |
|
OM_WC2 |
0 |
0 |
0 |
|
Wan Chai East PTW Boundary |
1 |
1 |
1 |
|
OM_C1 |
0 |
0 |
0 |
|
OM_C2 |
0 |
0 |
0 |
|
OM_C3 |
0 |
0 |
0 |
|
Central PTW Boundary |
2 |
1 |
2 |
|
OM_FM1 |
0 |
0 |
0 |
|
OM_SB1 |
0 |
0 |
0 |
|
OM_SB2 |
0 |
0 |
0 |
|
OM_SB3 |
0 |
0 |
0 |
|
OM_SB4 |
0 |
0 |
0 |
|
Sandy Bay PTW Boundary |
0 |
0 |
0 |
|
OM_CB1 |
0 |
0 |
0 |
|
OM_CB2 |
0 |
0 |
0 |
|
Cyberport PTW Boundary |
1 |
1 |
1 |
|
OM_WF1 |
0 |
0 |
0 |
|
Wah Fu PTW Boundary |
1 |
1 |
1 |
|
OM_AB1 |
1 |
1 |
1 |
|
Aberdeen PTW Boundary |
1 |
1 |
1 |
|
OM_ALC1 |
1 |
1 |
1 |
|
Ap Lei Chau PTW Boundary |
1 |
1 |
1 |
|
OM_SCI1 |
0 |
0 |
0 |
|
OM_SCI2 |
0 |
0 |
0 |
|
OM_SCI3 |
2 |
2 |
2 |
|
OM_SCI4 |
1 |
1 |
1 |
|
OM_SCI5 |
0 |
0 |
0 |
|
SCISTW Boundary Location A |
0 |
0 |
0 |
|
SCISTW Boundary Location A1 |
0 |
0 |
0 |
|
SCISTW Boundary Location B |
0 |
0 |
0 |
|
SCISTW Boundary Location C |
2 |
2 |
2 |
|
SCISTW Boundary Location D |
0 |
0 |
0 |
3.2.1. The meteorological conditions (including temperature, wind speed, wind direction, relative humidity) from the nearest Hong Kong Observatory’s Weather Stations for each of the odour patrols were provided for reference in Appendix D.
3.3.1. Generally, the odour intensities detected around the SCISTW and PTWs were found to be ranging from level 0 up to level 2. Level 2 was recorded at three monitoring locations. With reference to the Action / Limit Level as shown in Table 3.2, these three locations met the action level. However, at OM_SCI3 and Location C of SCISTW, garbage odour was recorded, and the nearby refuse transfer station was considered as the potential odour source. Hence, the exceedance at these two monitoring stations is concluded not related to the project. For Central PTW Boundary (near the gate), odour was recorded continuously under downwind near the gate. The odour is concentrated near the gate (entrance of the Central PTW) while the boundary other than the gate is odourless. Two panelists out of three considered the odour intensity was 2 while the left considered as 1. As the results were not unified, to confirm if the odour nuisance from Central PTW is significant or not, odour patrol at this point is proposed to be conducted to confirm the finding and determine if it is an occasional case.
Table 3.2 Action / Limit Levels of the Odour Patrol
|
Parameter |
Action |
Limit |
|
Odour Nuisance |
Odour Intensity of 2 is measured from odour patrol |
Odour Intensity of 3 or above is measured from odour patrol |
3.3.2. By comparing our impact monitoring data with the baseline monitoring data, generally, there are no significant difference between two sets of data. A summary table are shown in Table 3.3.
Table 3.3 Comparison between Baseline Data and Impact Data of Odour Patrol
|
Monitoring Location |
Operational Phase Baseline* |
Operational Phase Impact# |
|
Odour Intensity (0 to 4) |
||
|
OM_NP1 |
0 |
0 |
|
OM_NP2 |
0 |
0 |
|
OM_NP3 |
0 |
0 |
|
North Point PTW Boundary |
0 |
0 |
|
OM_WC1 |
0 |
0 |
|
OM_WC2 |
0 |
0 |
|
Wan Chai East PTW Boundary |
0 |
1 |
|
OM_C1 |
0 |
0 |
|
OM_C2 |
0 |
0 |
|
OM_C3 |
0 |
0 |
|
Central PTW Boundary |
0 |
2 |
|
OM_FM1 |
0 |
0 |
|
OM_SB1 |
0 |
0 |
|
OM_SB2 |
0 |
0 |
|
OM_SB3 |
0 |
0 |
|
OM_SB4 |
0 |
0 |
|
Sandy Bay PTW Boundary |
0 |
0 |
|
OM_CB1 |
0 |
0 |
|
OM_CB2 |
0 |
0 |
|
Cyberport PTW Boundary |
0 |
1 |
|
OM_WF1 |
0 |
0 |
|
Wah Fu PTW Boundary |
0 |
1 |
|
OM_AB1 |
0 |
1 |
|
Aberdeen PTW Boundary |
0 |
1 |
|
OM_ALC1 |
0 |
1 |
|
Ap Lei Chau PTW Boundary |
0 |
1 |
|
OM_SCI1 |
0 |
0 |
|
OM_SCI2 |
0 |
0 |
|
OM_SCI3 |
1 |
2 |
|
OM_SCI4 |
0 |
1 |
|
OM_SCI5 |
0 |
0 |
|
SCISTW Boundary Location A |
1 |
0 |
|
SCISTW Boundary Location A1 |
1 |
0 |
|
SCISTW Boundary Location B |
2 |
0 |
|
SCISTW Boundary Location C |
3 |
2 |
|
SCISTW Boundary Location D |
1 |
0 |
Remark(s):
1. * The Largest Data throughout the baseline period are extracted.
2. # The Largest Data among the three Odour Patrol Member are extracted.
4.1.1. In general, the odour patrol result is similar to the baseline data. There were three action level exceedances recorded but the two exceedances at SCISTW is found to be related to nearby refuse transfer stations while the exceedance from Central PTW is not unified by all three panelists and thus it is hard to confirm if the nuisance is significant or not.
4.2.1. With the odour patrol result, it is recommended to take more attention on Central PTW and additional odour patrol should be conducted at least once to confirm the exceedance is an occasional case.
4.3.1. There were three action level exceedances recorded at Central PTW Boundary (near the gate), OM_SCI3 and SCISTW Boundary Location C.
4.3.2. Table 4.1 shown the Event/Action Plan for Operation Air Quality Monitoring.
Table 4.1 Event/Action Plan for Operation Air Quality Monitoring
|
Event |
Action |
|
|
Person-in-charge of Odour Monitoring |
DSD |
|
|
Action Level |
||
|
Exceedance of action level |
1. Identify source/reason of exceedance; 2. Repeat odour patrol to confirm finding; 3. Repeat odour measurement at exhaust stacks of deodorization system of SCISTW (if exceedance at SCISTW) to confirm finding |
1. Carry out investigation to identify the source/reason of exceedance. 2. Investigation shall be completed within 2 week; 3. Implement more mitigation measures if necessary. |
|
Limit Level |
||
|
Exceedance of Limit level |
1. Identify source / reason of exceedance; 2. Repeat odour patrol to confirm finding; 3. Repeat odour measurement at exhaust stacks of deodorization system of SCISTW (if exceedance at SCISTW) to confirm finding 4. Increase monitoring frequency to monthly; 5. If exceedance stops, cease additional monitoring. |
1. Carry out investigation to identify the source/reason of exceedance. Investigation shall be completed within 2 week; 2. Rectify any unacceptable practice; 3. Formulate remedial actions; 4. Ensure amended working methods and remedial actions properly implemented; 5. If exceedance continues, consider what mitigation measures shall be implemented. |
4.3.3. According to the event and action plan, the reason / source of exceedance should be first identified. The investigation report is attached in Appendix H.
4.4.1. As mentioned by Investigation Report 001 as attached in Odour Monitoring Report for Harbour Area Treatment Scheme Stage 2A (Operational Phase) (January 2022), the results and findings of the regular odour patrol regarding Wan Chai East PTW Boundary, SCISTW Boundary Location B and SCISTW Boundary Location C are shown in Table 4.2.
Table 4.2 Results and findings of the Odour Patrol regarding Wan Chai East PTW Boundary, SCISTW Boundary Location B and SCISTW Boundary Location C conducted on 29th April 2022
|
Monitoring Location |
Odour Patrol Member |
On-Site Observation |
|||
|
O-1 |
O-2 |
O-3 |
Odour Characteristics |
Potential Odour Source |
|
|
Odour Intensity (0 to 4) |
|||||
|
Wan Chai East PTW Boundary |
1 |
1 |
1 |
Sewage |
Sewage Treatment Plant |
|
SCISTW Boundary Location B |
0 |
0 |
0 |
NA |
NA |
|
SCISTW Boundary Location C |
2 |
2 |
2 |
Garbage |
Refuse Station / Refuse Vehicles |
4.4.2. For Wan Chai East PTW Boundary, the odour intensity was 1 for all three panelists. For SCISTW Boundary Location B, the odour intensity was 0 for all three panelists. The odour level was acceptable and thus the exceedance recorded on 28th January 2022 was considered as an occasional case. The operators are reminded to maintain the equipment and plants in good condition and have a close monitoring on the performance of the deodorization units.
4.4.3. For SCISTW Boundary Location C, exceedance was recorded again. As it is in front of West Kowloon Refuse Transfer Station, the potential odour source was the refuse station / refuse vehicles. The odour characteristic was also recorded as garbage which were coincide with the findings recorded in January 2022. The odour nuisance at SCISTW Boundary Location C is considered to be continuously but non-project related.
5.1.1. Air samples will be collected by passive sampling technique at the odour monitoring station. A NalophanTM sampling bag will be placed inside an air-tight sampler and then drawn to vacuum for sampling. Approximately 60 litres of the gas sample is collected into the sampling bag for testing. A diagram of the passive sampling equipment that will be used for the sampling is shown below:
|
|
|
|
Figure 1: Passive Sampler |
Figure 2: A Schematic Diagram of Sampling Device |
5.1.2. Air samples in Nalophane bags shall be kept in cool condition not under direct sunlight exposure during the collection. If any condensate is observed on the inner surface of the sampled bag, the sample shall be discarded.
5.1.3. All samples collected during the sampling day shall be returned to laboratory at the same day. All olfactometry testing shall be conducted and finished within 24 hours after sampling.
5.1.4. The selected laboratory is the local laboratory for the measurement of odour concentration following the European Standard Method BS EN13725:2003 (by dynamic olfactometry). The Reporting Limit for the Olfactometry Analysis is 11 OUE/m3.
- Odour concentration of the sample is determined by Forced-choice Dynamic Olfactometer in accordance to European Standard Method: BS EN13725:2003.
- Testing should be performed by five qualified panellists who have been trained and complied with the requirement of the European Standard Method: BS EN13725:2003 in the range of 20 to 80 ppb/v and a standard deviation of R < 2.3.
- Testing shall be started immediately after sample receipt and all testing to be completed with 24 hours after sampling.
5.1.5. The odour concentration is measured by determining the dilution factor required to reach the detection threshold. The odour concentration at the detection threshold is by definition 1 OUE/m3. The odour concentration is then expressed in terms of multiples of the detection threshold.
|
|
|
Figure 3: Olfactory Laboratory with ScentroidTM SS600 Olfactometer |
5.1.6. During each odour sampling day, one blank sample should be collected for quality control. The sample will be taken by purging pure nitrogen gas into the odour bag directly on site as a blank sample.
5.1.7. All equipment for odour measurement and analysis are maintained and calibrated in according to the requirement of the European Standard Method EN13725.
5.2.1. Odour measurement shall be conducted every three months for the first year of operation for the expanded SCISTW. The first odour measurement shall be conducted within one month after operation of the expanded SCISTW. Subsequent odour measurement shall be conducted at the 4th, 7th and 10th month.
5.3.1. According to section 2.36 of the EM&A Manual, odour measurement will be conducted at 15 exhaust stacks of the deodorization system at SCISTW. The odour measurement locations are listed in Table 5.1. As suggested by the contractor, the location ID is renamed to better identify the deodorization unit which is different from that on the detailed reporting requirement of odour monitoring report.
5.3.2. The layout of odour monitoring locations for odour measurement is shown in Appendix E.
Table 5.1 Odour Monitoring Locations for Odour Measurement
|
Location Point |
|
DOU 1-R(1) |
|
DOU 1-PS(2) |
|
DOU 1B-1 |
|
DOU 1B-2 |
|
DOU 2-PS(3) |
|
DOU 3 |
|
DOU 4-PS(4) |
|
DOU 5-PS(5) |
|
DOU 6 |
|
DOU 6A |
|
DOU 6B |
|
DOU 8-1 |
|
DOU 8-2 |
|
DOU 9-1 |
|
DOU 9-2 |
|
Notes: |
|
(1) Replace DOU 4-2 stated in Detailed Reporting Requirement of Odour Monitoring Report (Renaming to distinguish the source of odour is different from that of DOU4) |
|
(2) Replace DOU 1 stated in Detailed Reporting Requirement of Odour Monitoring Report (A polishing stage (PS) is added after the treatment of DOU 1 to enhance odour treatment performance) |
|
(3) Replace DOU 2 stated in Detailed Reporting Requirement of Odour Monitoring Report (A polishing stage (PS) is added after the treatment of DOU 2 to enhance odour treatment performance) |
|
(4) Replace DOU 4 stated in Detailed Reporting Requirement (A polishing stage (PS) is added after the treatment of DOU 4 to enhance odour treatment performance) |
|
(5) Replace DOU 5 stated in Detailed Reporting Requirement (A polishing stage (PS) is added after the treatment of DOU 5 to enhance odour treatment performance) |
5.4.1. During sampling, following items will be recorded:
- ambient temperature;
- relative humidity;
- wind speed; and
- wind direction
- photo showing the sampling locations relative to existing land features
6.1.1. The odour measurement was conducted on 29th April 2022. The detail of location photo is shown in Appendix E.
6.1.2. The odour emission rate is listed in Table 6.1. The total odour emission rate is calculated to be 2,008 ou/s. Appendix F shown the detail monitoring results for each monitoring location.
Table 6.1 Summary of Odour Emission Rate
|
Location ID |
Odour Emission Rate (ou/s) |
|
DOU 1-R |
<8 |
|
DOU 1-PS |
<40 |
|
DOU 1B-1 |
25 |
|
DOU 1B-2 |
33 |
|
DOU 2-PS |
<35 |
|
DOU 3 |
250 |
|
DOU 4-PS |
51 |
|
DOU 5-PS |
3 |
|
DOU 6 |
67 |
|
DOU 6A |
830 |
|
DOU 6B |
490 |
|
DOU 8-1 |
67 |
|
DOU 8-2 |
79 |
|
DOU 9-1 |
<15 |
|
DOU 9-2 |
<15 |
6.2.1. The total odour emission rate presented in EIA Report Table 3.14 are given in Appendix G, the design total mitigated odour emission rate is 11,506.21 ou/s for Option 2 – Decentralized Design.
6.2.2. Comparison between impact monitoring data and data obtained from EIA is shown in Table 6.2.
Table 6.2 Comparison between Impact Monitoring Data and Data Obtained from EIA
|
Total Odour Emission Rate (ou/s) |
|
|
Operation Phase Impact |
EIA |
|
2,008 |
11,506.21 |
6.2.3. According to Table 2.3 of EM&A Manual, the Action / Limit Level is shown in Table 6.3.
Table 6.3 Action / Limit Levels of the Odour Measurement
|
Parameter |
Action |
Limit |
|
Odour Nuisance |
- When two documented complaints are received; or - Measured total odour emission rate from exhaust stacks of deodorization system at SCSITW ≧0.9 x Total mitigated odour emission rate presented in EIA Report |
- Five or more consecutive genuine documented complaints within a week; or - Measured total odour emission rate from exhaust stacks of deodorization system at SCISTW ≧ Total mitigated odour emission rate presented in EIA Report |
7.1.1. The impact total odour emission rate is smaller than the 90% of total mitigated odour emission rate presented in the EIA report (10355.59 ou/s). The odour measurement is acceptable and no exceedance is recorded.
7.2.1. The operator is reminded to maintain the plants and deodorization units are in good condition and to keep a close monitoring on the in-house H2S sensors to ensure that no odour nuisance is induced by SCSITW.
7.3.1. The odour measurement was conducted on 29th April 2022 and the total odour emission rate was calculated to be 2,008 ou/s. The result was smaller than the 90% of total mitigated odour emission rate presented in the EIA report (10355.59 ou/s). The odour measurement is acceptable and no exceedance is recorded.
7.3.2. As mentioned in Investigation Report 002 attached in Odour Monitoring Report for Harbour Area Treatment Scheme Stage 2A (Operational Phase) (January 2022), it is recommended to counter check the H2S reading of the in-house sensors and portable equipment in the next monitoring.
7.3.3. The on-site H2S measurement of portable equipment was conducted on 29th April 2022. Table 7.1 summarized the model used and the limit of detection. Copy of calibration certificate is attached in Appendix I. The H2S readings is summarized in Table 7.2.
Table 7.1 Information of the Portable H2S Meter
|
Product Name |
Model Number |
Limit of Detection |
|
POLI |
MP400P |
0.1 ppm |
Table 7.2 Summary of H2S Readings of Portable Equipment and In-house H2S Sensors
|
Location ID |
Portable Equipment H2S Reading (ppm) |
In-house H2S Sensors H2S Reading (ppm) |
|
DOU 1-R |
<0.1 |
0.014 |
|
DOU 1-PS |
<0.1 |
N/A |
|
DOU 1B-1 |
<0.1 |
N/A |
|
DOU 1B–2 |
<0.1 |
N/A |
|
DOU 2-PS |
<0.1 |
0.011 |
|
DOU 3 |
<0.1 |
0.15 |
|
DOU 4-PS |
<0.1 |
0.002 |
|
DOU 5-PS |
<0.1 |
0.008 |
|
DOU 6 |
<0.1 |
<0.01 |
|
DOU 6A |
<0.1 |
0.15 |
|
DOU 6B |
<0.1 |
0.12 |
|
DOU 8-1 |
<0.1 |
<0.01 |
|
DOU 8-2 |
<0.1 |
0.06 |
|
DOU 9-1 |
<0.1 |
N/A |
|
DOU 9-2 |
<0.1 |
N/A |
7.3.4. To conclude, the odour emission rate from the odour measurement and the H2S readings from portable equipment shown that the odour emitted from SCISTW is under an acceptable range. Therefore, from the results obtained from 29th April 2022, the performance of deodorization device is considered to be in normal operation. Generally, the H2S readings of portable equipment and in-house H2S sensors were coincided except DOU 6A and DOU 6B. To provide better comparison, the detection limit of portable H2S equipment should be the same with in-house H2S sensors which was 0.001 ppm (1 ppb).
7.3.5. To further understand the gas composition and provide information on investigating the exceedance and difference of odour measurement result between January 2022 and April 2022, the overall correlation between H2S concentrations and odour units of available DOUs was plotted in Graph 1. In-house H2S concentration from sensors and odour concentration from odour measurement for April 2022 was listed in Table 7.3.
Table 7.3 In-house H2S Concentration from Sensors and Odour Concentration from Odour Measurement for April 2022
|
Location ID |
In-house H2S Concentration (ppm) |
Odour Concentration (OU/m3) |
|
DOU 1-R |
0.014 |
<11 |
|
DOU 1-PS |
N/A |
<11 |
|
DOU 1B-1 |
N/A |
12 |
|
DOU 1B-2 |
N/A |
16 |
|
DOU 2-PS |
0.011 |
<11 |
|
DOU 3 |
0.15 |
15 |
|
DOU 4-PS |
0.002 |
92 |
|
DOU 5-PS |
0.008 |
13 |
|
DOU 6 |
<0.01 |
66 |
|
DOU 6A |
0.15 |
79 |
|
DOU 6B |
0.12 |
48 |
|
DOU 8-1 |
<0.01 |
56 |
|
DOU 8-2 |
0.06 |
63 |
|
DOU 9-1 |
N/A |
<11 |
|
DOU 9-2 |
N/A |
<11 |
Graph 1 Overall Correlation between Odour and H2S Concentration
Remark:
1. Data smaller than detection limit would be plotted as zero for graph presentation
7.3.6. According to Graph 1, no correlation can be established generally. With the above-mentioned observation, the reason of exceendance recorded on 28th January 2022 may be due to the fluctuating composition of incoming sewage. Sewage treatment works occasionally experience shock odour load arising from the fluctuating composition of incoming sewage. This may result in short term strong odour emission.
7.3.7. The big difference of the monitoring results between January 2022 and April 2022 may also be due to the variation of influent composition and quality. Therefore, normal disinfection process may not be able to abate the odour. Besides, the activated carbons of some DOUs were replaced as it was found to be moisturized, which would affect the deodorization performance. Slight adjustment to the operation mode of some DOUs including the quantities of chemicals being added, to enhance the deodorization performance. These actions contributed to the difference on monitoring results between January 2022 and April 2022.
7.3.8. To conclude, the exceedance recorded on 28th January 2022 was an occasional case. The operators are reminded to maintain the equipment and plants in good condition and have a close monitoring on the performance of the deodorization units.
