5. Measurement of Site Emissions - Amazon Web Servicesec2-54-247-115-33.eu-west-1.compute.amazonaws.com/tw/... · 2015-06-24 · 5. Measurement of Site Emissions 5.1 Septicity Measurements

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h:\projects\em-260\27000 projects\27687 aq thames water mogden\1 client\reports\final report r008i.doc © Entec UK Limited November 2010

5. Measurement of Site Emissions

5.1 Septicity Measurements

5.1.1 Wastewater samples were taken from across the site noting the pH, conductivity and temperature, thus allowing the calculation of rH value that can be used to indicate the septicity of the samples. Using the Degremont Scale for septicity, shown as Table 5.1, all of the samples were considered to fall within the ‘normal raw water’ category.

Table 5.1 Septicity Values15

Calculated rH Value Characteristics

<0 Reducing area with H2S release

0-10 Area of optimal anaerobic digestion

10-13 Anaerobic conditions - Foul water

13-15 Anaerobic conditions - Septic water

15-23 Normal Raw Water

23-27 Anoxic conditions

>27 Aerobic conditions

Table 5.2 Septicity of Wastewater Samples

pH ORP (mV) Temp (c)

eH rH

West PST (Rectangular)

5.94 -52 20.7 148 16.98

West PST (Cricular) 6.65 -9 20.7 191 19.89

West FST 6.55 -43 20.7 157 18.51

West ASP 7.2 -169 20.9 31 15.47

Storm Hopper 7.38 -105 21.6 95 18.04

Storm Channel 7.41 -131 20.7 69 17.20

East Side FST 7.5 -22 21.1 178 21.14

East Side ASP 7.45 -9 21.4 191 21.49

15 Scale from the Degremont Handbook, Sixth Edition, Volume 1

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5.2 Odour Sampling

5.2.1 Tables 5.3 to 5.12 contain the results from the odour and hydrogen sulphide sampling undertaken across the process sources and the odour control units throughout the study.

Odour Sampling Conducted between 3-5 August

Table 5.3 Odour Concentrations and Calculated Odour Emission Rates

Odour Concentration (ouE m-3) Source Stage

Sample 1 Sample 2 Sample 3 Geometric mean

Odour Emission

Rate (ouE s-1)

East Side OCU (Main) Inlet 5,248 3,897 3,742 4,246 -

Intermediate 2,417 2,158 2,230 2,266 -

Outlet 261 506 609 432 12,538

West Side OCU Inlet 66,850 11,621 8,538 18,789 -

Intermediate 421 424 440 428 -

Outlet 1,975 2,168 791 1,502 2,107

Sludge Transfer OCU Inlet 15,280 46,810 85,540 39,404 -

Intermediate 8,030 4,880 14,270 8,239 -

Outlet 5,875 6,740 9,258 7,157 3,873

Sludge thickener Inlet 901,900 589,400 728,513 728,901 -

Intermediate 21,140 12,920 18,350 17,113 -

Outlet 8,173 50,510 31,760 23,850 29,482

Sludge Import (filling) Inlet 1,201,200 617,617 1,554,553 1,048,689 -

Outlet 21,860 20,550 21,280 21,223 4,142

Sludge Import (normal) Inlet 240,582 580,346 353,197 366,710 -

Outlet 7,727 8,575 9,439 8,552 1,669

Sludge Pumping Station Inlet 24,390 37,220 56,030 37,051 -

Outlet 7,508 8,877 6,739 7,658 3,995

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Table 5.4 Hydrogen Sulphide Concentrations and Calculated Odour Emission Rates

H2S Concentration (ppm) Source Stage

Sample 1 Sample 2 Sample 3 Arithmetic Mean

H2S Emission

Rate (µg s-1)

East Side OCU (Main) Inlet H/L H/L H/L H/L -

Intermediate 0.006 0.002 0.009 0.006 -

Outlet 0.000 0.000 0.000 0.000 0.00

West Side OCU Inlet 0.025 0.014 0.009 0.016 -

Intermediate 0.000 0.000 0.000 0.000 -

Outlet 0.002 0.002 0.000 0.001 2.84

Sludge Transfer OCU Inlet 0.025 0.037 0.031 0.031 -

Intermediate 0.020 0.016 0.015 0.017 -

Outlet 0.001 0.000 0.000 0.000 0.27

Sludge thickener Inlet 1.2 1.3 1.3 1.3 -

Intermediate 0.006 0.005 0.004 0.005 -

Outlet 0.001 0.001 0.000 0.007 1.27

Sludge Import (filling) Inlet 33.0 27.0 27.0 29.0 -

Outlet 0.025 0.043 0.048 0.039 11.45

Sludge Import (normal) Inlet 13.0 15.0 17.0 15.0 -

Outlet 0.023 0.025 0.017 0.022 6.42

Sludge Pumping Station Inlet 0.070 0.082 0.012 0.055 -

Outlet 0.014 0.011 0.015 0.013 10.56

H/L H2S concentration exceeding 50 ppm.

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Odour Sampling Conducted between 9-11 August

Table 5.5 Odour Results 9-11 August

Odour Concentration (ouE m-3)

Odour Source Sample

1 Sample

2 Sample

3 Geometric

Mean

Odour Emission Rate

(ouE m-2 s-1)

Benchmark Odour

Emission Rate (ouE m-2 s-1)


545 615 633 596 3.8 5.22

West PST (Cricular) 4,340 9,082 9,129 7,113 45.7 5.22

West FST 440 163 241 259 1.7 1.11

West ASP 966 1,027 1,453 1,130 7.3 1.84

Storm Hopper 430 633 387 472 3.0 2.53*

Storm Channel 902 771 1,458 1,005 6.4 2.53*

East Side FST 2,078 171 272 459 2.9 1.11

East Side ASP 26,880 12,790 21,040 19,340 124.1 1.84

Digester Gas 844,560 1,386,799 1,102,998 1,089,113 - -

Table 5.6 Hydrogen Sulphide Results 9-11 August

Hydrogen Sulphide (ppm) Odour Source

Sample 1 Sample 2 Sample 3 Mean

H2S Emission Rate (µg m-2 s-1)


0.830 0.430 0.750 0.670 6.9

West PST (Circular) 1.180 1.700 2.700 1.860 19.1

West FST 0.004 0.002 0.000 0.002 0.0

West ASP 0.120 0.063 0.108 0.097 1.0

Storm Hopper 0.006 0.006 0.007 0.006 0.1

Storm Channel 0.006 0.003 0.005 0.005 0.0

East Side FST 0.001 0.000 0.000 0.000 0.0

East Side ASP 0.145 0.145 0.150 0.147 1.5

Digester Gas 0.6 0.6 0.6 0.6 -

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Odour Sampling Conducted on 2 September

Table 5.7 Odour Concentrations and Calculated Emission Rates


Odour Source

Sample 1 Sample 2 Sample 3 Geometric Mean

Odour Emission

Rate (ouE m-2 s-1)

Benchmark odour

Emission Rate

(ouE m-2 s-1)

West PST Circular 878 686 604 714 4.6 5.22

East ASP 18380 14300 12420 14,834 95.2 1.84

East ASP Middle 707 1159 1067 956 6.1 1.84

East ASP near river 158 111 119 128 0.8 1.84

Table 5.8 Hydrogen Sulphide Concentrations and Calculated Emission Rates

Hydrogen Sulphide (ppm) Odour Source



West PST (Circular) 0.010 0.010 0.011 0.010 0.11

East ASP 0.109 0.160 0.170 0.146 1.5

East ASP Middle 0.015 0.014 0.013 0.014 0.14

East ASP near river 0.001 0.000 0.001 0.001 0.01

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Odour Sampling Conducted on 16 September

Table 5.9 Odour Concentrations and Calculated Emission Rates


Odour Source

Sample 1 Sample 2 Sample 3 Geometric Mean

Odour Emission

Rate (ouE m-2 s-1)

Benchmark odour

Emission Rate

(ouE m-2 s-1)

Storm 4 612 766 868 741 4.8 2.53

ASP East 11,605 11,160 9,172 10,591 105.6 1.84

ASP West 3,167 1,352 1,808 1,978 23.2 1.84

PST West (Circular 302 137 176 194 1.2 5.22

Table 5.10 Hydrogen Sulphide Concentrations and Calculated Emission Rates

Hydrogen Sulphide Concentration (ppm) Odour Source


H2S Emission Rate

(µg m-2 s-1)

West PST Circular 1.300 1.300 1.200 1.267 13.0

East ASP 0.280 0.370 0.380 0.343 5.5

East ASP Middle 0.050 0.038 0.042 0.043 0.8

East ASP near river 0.016 0.013 0.011 0.013 0.1

Odour Sampling - 14 October - ASP Spot Sampling

5.2.2 Figure 5.1 details the locations of the sampling points used during the ASP spot sampling exercise on the 14 October. Samples 1-9 were taken from Battery A whilst samples 10-18 were taken from the same locations on Battery B.

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Figure 5.1 ASP Sampling Locations

Table 5.11 ASP Sampling Results - Odour

Sample Location Odour Concentration (ouE m-3)

Odour Emission Rate (ouE m-2 s-1)

Battery A

1 10,000 132.1

2 7,320 63.6

3 2,870 31.4

4 131 1.4

5 257 1.6

6 145 1.0

7 339 2.7

8 188 0.6

9 127 0.8

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Sample Location Odour Concentration (ouE m-3)

Odour Emission Rate (ouE m-2 s-1)

Battery B

10 18,060 75.0

11 34,410 142.9

12 21,380 88.8

13 438 1.8

14 204 0.8

15 101 0.4

16 196 0.8

17 107 0.4

18 317 1.3

Table 5.12 ASP Sampling Results - Hydrogen Sulphide

Sample Location (Battery A) H2S Concentration (ppm)


Battery A

1 0.160 3.38

2 0.490 6.81

3 0.140 2.45

4 0.002 0.03

5 0.003 0.03

6 0.002 0.02

7 0.002 0.03

8 0.003 0.01

9 0.002 0.02

Battery B

10 0.260 1.73

11 0.465 3.09

12 0.275 1.83

13 0.005 0.03

14 0.000 0.00

15 0.004 0.02

16 0.004 0.03

17 0.005 0.03

18 0.002 0.01

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5.3 Summary of Odour Control Unit performance

5.3.1 The maintenance of the odour control units on site are undertaken by an independent contractor, Odour Services International Limited (OSIL). OSIL are responsible for maintaining the performance of the odour control units, with duties including the maintenance of media in biofilters, the operation of the wet chemical scrubber and bio scrubber, and ensuring that the carbon polishing units are not exhausted.

5.3.2 The sampling of the odour control units across the site resulted in the conclusion that the OCUs are, on the whole, providing an effective reduction of the more offensive odour sources across the site, including the preliminary treatment, the primary treatment and sludge areas.

Table 5.13 Summary of Odour Control Unit performance

Source Percentage Removal Outlet Concentration

East Side OCU 90 432

West Side OCU 92 1,502

Sludge Transfer OCU 82 7,157

Sludge Thickener OCU 97 23,580

Sludge PS 98 7,658

Sludge Import (static) 98 8,551

Sludge Import (filling) 98 21,223

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6. Dispersion Modelling of Baseline Emissions

6.1 Model Input Data

6.1.1 The sampling data from section 5.2 has been used as the base data for the dispersion modelling exercise. From Figure 6.1, it can be seen that the dominant sources, in terms of ouE s-1 is the east ASP. This is primarily due to the elevated odour emission rate from the first leg of the ASP.

6.1.2 The total emission rate from the site is 1,469,416 ouE s-1. Of which, the east ASP represents 65% of the total emissions.

Figure 6.1 Comparison of Odour Emission Rates

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12,538 2,10625,754 30,348

58,218

956,432

13,295

55,302

3,873 4,142 3,995 11,56029,482

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6.2 Model Predictions

6.2.1 The dispersion modelling for both of the new generation models for the current baseline predict an exceedence of the 5 ouE m-3 as the 98th percentile of hourly averages criteria in the area surrounding the Mogden Sewage Treatment Works.

6.2.2 The contour plots for both the UK-ADMS and the USEPA AERMOD dispersion models (Figure 6.2) predict that despite the predominant south westerly wind the greater area of the contour lies to the south east, extending to the River Thames and Eel Pie Island. This is as a result of a greater percentage of lower wind speeds from the North West. The ISCST3 dispersion model generally predicted higher ground level concentrations that either of the new generation dispersion models, often by a factor of two.

6.2.3 The predictions from the two dispersion models correlate well together, thus increasing the confidence in the predictions.

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Figure 6.2 Predicted Baseline for Mogden - Worst Case Meteorological Year 200716

16 © Crown Copyright. All rights reserved 2010. Licence Number 0100031673

ADMS (Red) AERMOD (Green) ISC (Blue)

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6.1 Differences in Comparison to the Planning Application Model

6.1.1 From the review of the planning application submitted on behalf of Thames Water for the expansion of the scheme, it was noted that the reported extent of the area that would receive an odour concentration exceeding 5 ouE m-3 as the 98th percentile of hourly averages (Figure 6.3) was less than the baseline predicted by this assessment.

• From a review of the methodologies the following would appear to explain some of the differences.

• Difference in meteorological data. In this assessment, AMEC Entec has used five years of data (2005-2009) with the worst case year being presented in the results. The OdourNet study used three years of data (1996-98). It is unclear if the presented results were the 98th percentile of the 96-98 period or the worst case meteorological year.

• OdourNet have used a time weighted emission profile, this assumed that process sources would be reduced by 80% during the winter months.

• OdourNet had undertaken hedonic tone analysis of the ASP emission, on the basis of these results showing that the odour from this area was less offensive reduced the emission rate to 50%. The OdourNet survey had not previously identified the area of elevated emission rates as reported by Entec.

• Due to being less offensive, OdourNet did not include the emissions from the final settlement tanks.

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Figure 6.3 Baseline Model from the 2009 Planning Application

Broken blue line = predicted 5ouE m-3 as the 98th percentile of hourly averages.

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6.2 Contribution of Sources

Receptor: Summerwood Road

6.2.1 The odour concentration as the 98th percentile of hourly averages was predicted to be 60 ouE m-3. The prime contributor to odour at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the east side ASP remains the prime contributor to odour at this location.

6.2.2 The H2S concentration as the 98th percentile of hourly averages was predicted to be 5.4 ppb. The prime contributor to H2S at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the prime contributor to H2S at this location are the rectangular primary settlement tanks.

Figure 6.4 Location of Summerwood Road17


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Figure 6.5 Speciation of Odour Sources Contributions at Summerwood Road at 98th, 99th and 99.9th percentiles

Source Contributions to Odour during the Hour Corresponding to 98th Percentile Odour Concentration

Source Contributions to H2S during the Hour Corresponding to 98th Percentile H2S Concentration



Source Contributions to Odour during the Hour Corresponding to 99.9th Percentile Odour Concentration

Source Contributions to H2S during the Hour Corresponding to 99.9th Percentile H2S Concentration

West ASP West PST Rectangle

West PST Circular West FST

Digesters East ASP

East FST Storm Tanks/Channels

Sludge Pumping OCU East OCU

West OCU Sludge Transfer OCU

Sludge Imports OCU Sludge Thickening OCU

Engine

42


Receptor: Haliburton Road


6.2.4 The H2S concentration as the 98th percentile of hourly averages was predicted to be 1.4 ppb. The prime contributor to H2S at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the prime contributors to H2S at this location are the rectangular primary settlement tanks and storm tanks respectively.

Figure 6.6 Location of Haliburton Road18


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Figure 6.7 Speciation of Odour Sources Contributions at Haliburton Road at 98th, 99th and 99.9th percentiles



Source Contributions to Odour during the Hour

Corresponding to 99th Percentile Odour Concentration






Digesters East ASP





Engine

44


Receptor: Worple Avenue


6.2.6 The H2S concentration as the 98th percentile of hourly averages was predicted to be 3.4 ppb. The prime contributor to H2S at this location is predicted to be the storm tanks. At the 99th and 99.9th percentile the prime contributors to H2S at this location are the PSTs and rectangular primary settlement tanks respectively.

Figure 6.8 Location of Worple Avenue19


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Figure 6.9 Speciation of Odour Sources Contributions at Worple Avenue at 98th, 99th and 99.9th percentiles





Source Contributions to Odour during the Hour

Corresponding to 99.9th Percentile Odour Concentration




Digesters East ASP





Engine

46


Receptor: Windermere House


6.2.8 The H2S concentration as the 98th percentile of hourly averages was predicted to be 5.4 ppb. The prime contributor to H2S at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the prime contributors to H2S at this location are the east side ASP and rectangular primary settlement tanks respectively.

Figure 6.10 Location of Windermere House 20


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Figure 6.11 Speciation of Odour Sources Contributions at Windermere House at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

48


Receptor: Arnold Crescent

6.2.9 The odour concentration as the 98th percentile of hourly averages was predicted to be 12 ouE m-3. The prime contributor to odour at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the ASP remains the prime contributor to odour at this location.

6.2.10 The H2S concentration as the 98th percentile of hourly averages was predicted to be 2.3 ppb. The prime contributor to H2S at this location is predicted to be the west side ASP. At the 99th and 99.9th percentile the prime contributors to H2S at this location are the PSTs and rectangular primary settlement tanks respectively.

Figure 6.12 Location of Arnold Crescent21


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Figure 6.13 Speciation of Odour Sources Contributions at Arnold Crescent at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

50


Receptor: Elmer Gardens

6.2.11 The odour concentration as the 98th percentile of hourly averages was predicted to be 6.8 ouE m-3. The prime contributor to odour at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the east side ASP remains the prime contributor to odour at this location.

6.2.12 The H2S concentration as the 98th percentile of hourly averages was predicted to be 1.6 ppb. The prime contributor to H2S at this location is predicted to be the storm tanks. At the 99th and 99.9th percentile the prime contributor to H2S at this location are the rectangular primary settlement tanks.

Figure 6.14 Location of Elmer Gardens22


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Figure 6.15 Speciation of Odour Sources Contributions at Elmer Gardens at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

52


Receptor: Weavers Close

6.2.13 The odour concentration as the 98th percentile of hourly averages was predicted to be 31 ouE m-3. The prime contributor to odour at this location is predicted to be the west side ASP. At the 99th and 99.9th percentile the east side ASP is the prime contributor to odour at this location.

6.2.14 The H2S concentration as the 98th percentile of hourly averages was predicted to be 2.8 ppb. The prime contributor to H2S at this location is predicted to be the west side ASP. At the 99th and 99.9th percentile the prime contributor to H2S at this location are the rectangular primary settlement tanks.

Figure 6.16 Location of Weavers Close23


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Figure 6.17 Speciation of Odour Sources Contributions at Weavers Close at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

54


Receptor: Worton Road


6.2.16 The H2S concentration as the 98th percentile of hourly averages was predicted to be 2.8 ppb. The prime contributor to H2S at this location is predicted to be the rectangular primary settlement tanks. At the 99th and 99.9th percentile the prime contributor to H2S at this location are still the rectangular primary settlement tanks.

Figure 6.18 Location of Worton Road24


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Figure 6.19 Speciation of Odour Sources Contributions at Worton Road at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

56


Receptor: Mogden Lane

6.2.17 The odour concentration as the 98th percentile of hourly averages was predicted to be 170 ouE m-3. The prime contributor to odour at this location is predicted to be the east side ASP. At the 99th and 99.9th percentile the east side ASP remains as the prime contributor to odour at this location.

6.2.18 The H2S concentration as the 98th percentile of hourly averages was predicted to be 10 ppb µg m-3. The prime contributor to H2S at this location is predicted to be the PSTs. At the 99th and 99.9th percentile the prime contributor to H2S at this location are the rectangular primary settlement tanks.

Figure 6.20 Location of Mogden Lane25


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Figure 6.21 Speciation of Odour Sources Contributions at Mogden Lane at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

58


Receptor: Whitton Dene

6.2.19 The odour concentration as the 98th percentile of hourly averages was predicted to be 7 ouE m-3. The prime contributor to odour at this location is predicted to be the west side ASP. At the 99th and 99.9th percentile the west side ASP is the prime contributor to odour at this location.

6.2.20 The H2S concentration as the 98th percentile of hourly averages was predicted to be 0.9 ppb. The prime contributor to H2S at this location is predicted to be the rectangular primary settlement tanks. At the 99th and 99.9th percentile the prime contributor to H2S at this location remain as the rectangular primary settlement tanks.

Figure 6.22 Location of Whitton Dene26


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Figure 6.23 Speciation of Odour Sources Contributions at Whitton Dene at 98th, 99th and 99.9th percentiles









Digesters East ASP





Engine

60


6.3 Summary of Baseline Scenario

The dispersion modelling of the baseline scenario has predicted an area of approximately 7.1km2 exceeding the 5 ouE m-3 as the 98th percentile contour.

The assessment predicts that for the selected receptor locations, the predicted odour concentration is in excess of the 5 ouE m-3 as the 98th percentile of hourly averages odour criterion. Table 6.1 summarises the odour concentration at each receptor.

The assessment has shown that the primary contributor to odour at all receptor locations is the East Side ASP as the 98th, 99th and 99.9th percentile of hourly averages. The exception to this is that the West Side ASP is the dominant source as the 98th percentile at the Weavers Close receptor.

Table 6.1 Predicted Odour Concentrations - Baseline Scenario

Receptor Predicted concentration (ouE m-3 as the 98th percentile of hourly averages)

Summerwood Road 60

Haliburton Road 21

Worple Avenue 75

Windermere House 94

Arnold Cresent 12

Elmer Gardens 7

Weavers Close 31

Worton Road 23

Mogden Lane 170

Whitton Dene 7

Documents

5. Measurement of Site Emissions - Amazon Web Servicesec2-54-247-115-33.eu-west-1.compute.amazonaws.com/tw/... · 2015-06-24 · 5. Measurement of Site Emissions 5.1 Septicity Measurements