Bio aerosols in building drainage and plumbing systems -cross contamination, monitoring and prevention

1. Bi l i b ildiBio-aerosols in building
drainage and plumbing
tsystems: cross
contamination, monitoring
and prevention.
Dr Michael Gormley
Drainage Research Group
School of the Built Environment
Heriot-Watt University
Edinburgh

2. ContentsContents
 The building drainage system as The building drainage system as
a bioaerosol transmission route
 Transmission study of the
drainage system of a hospitaldrainage system of a hospital
 Monitoring method for minimising Monitoring method for minimising
bioaerosol transmission from the
drainage systemdrainage system

3. Introduction
Bio-aerosols- what are they?y
Bioaerosols are defined as airborne particles, large
molecules or volatile compounds that are living, contain
living organisms or were released from livingliving organisms or were released from living
organisms. The size of a bioaerosol particle may vary
from 100 microns to 0.01 micron. The behaviour of
bioaerosols is governed by the principles of gravitation,
electromagnetism, turbulence and diffusion.

4. Introduction
Relative size of particles
100 microns
10 microns
1 micron
0.01 microns
This is a scale representation of the relative size of pollen, pollen spores,
bacteria and viruses. The scale of this diagram is roughly 8000:1. Each of the
dots on this screen version represent 15 viruses or virions In this diagramdots on this screen version represent 15 viruses, or virions. In this diagram,
approximately 100,000 of these virions fit within the 100 micron circle
representing the pollen. In actuality, many millions of virions could fit within the
cross-section of a pollen.

5. Bio-aerosol generation and
detection
 Bioaerosols, particularly those containing
viruses are particularly difficult to isolate and
identify.
 This task is made even more difficult due to
the unsteady nature of flows in building
d i tdrainage systems.

6. Building drainage system: mechanisms for air
flow and pressure transient generation
direction of air entrainment
flow and pressure transient generation
Discharging
Increased
entrainedDischarging
appliance increases
entrained airflow
and generates
ti t i t
entrained
airflow
negative transients.
Trap seal
depletion
Negative transient
depletion
Increased water
flow.

7. Building drainage system: mechanisms for air
flow and pressure transient generationflow and pressure transient generation
operating
appliance
Positive
transient affectsTrap seal
all traps
Trap seal
deflections
Airflow reduced due
to stack base
surchargesurcharge

8. Pressure transients in system can cause traps to blow
out-
http://www.youtube.com/watch?fea
ture=player detailpage&v=d vNLture player_detailpage&v d_vNL
MCZ9jQ
video
The attached video is anThe attached video is an
extreme example – but it is
real – most common
symptom of smallersymptom of smaller
pressure transients is
bubbling through a trap,
you may have seen this iny y
a toilet bowl.

9. Airflow and pressure transient modelling- AIRNET
and current limitations
 A method of characteristics based numerical
model.
 Finite difference scheme
 Developed and validated over 30 years at
Heriot- Watt University – initiated by, and
ti t b i i d b th k f J hcontinues to be inspired by, the work of John
Swaffield.

10. Building Drainage System modelling
in AIRNET (3)
When
P
Δt = Δx
Δx A′
B′
C‐
C+
(u+c)max
A
R S
BC
  0||4
2



t
uufccuu
For C+
- Line PR
  0
2
||4
1



D
uufccuu RRRRPRP

dx
u c 
when
dt
u c 
  0
2
||4
1
2





D
t
uufccuu SSSSPSP

For C-
- Line PS
Building drainage system
boundary conditions
cu
dt
dx

when

11. AIRNET modelling
Modelling of complex networks such as the O2
Dome
Thi i th fi t l d d i tThis is the first sealed drainage system ever
constructed. It has no penetrations through the
roof. As drainage systems go, it is unique.
The approach designed by M.Gormley and
50 Storey housing block in
Hong Kong
Modelling led to novel
approaches to preventingpp g y y
J.A.Swaffield from Heriot-Watt
approaches to preventing
excessive positive
pressures using P.A.P.A.TM

12. modelling air pressure and flow in large systems
St kSt k
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
Roof line
Stack
terminationRoof line
Stack
termination
Entrained
air
W.c.
W.c.
‘Wet’ stackParallel vent
W.c.
W.c.
‘Wet’ stackParallel vent
W.c.
W.c.
W.c.
W.c.
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
air
Sewer
connection
Wet stackParallel vent
stack with cross
connections Sewer
connection
Wet stackParallel vent
stack with cross
connections
W.c.
Sewer
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
Sewer
‘Wet’ stackParallel vent
stack with cross
connections
W c
W.c.
W c
W.c.
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
connectionconnection
W.c.
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
W.c.
‘ ’
W.c.
W.c.
‘ ’
Combined waste
fluids and waste
in appliance
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
in appliance
water flows

13. St kSt k
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
Roof line
Stack
terminationRoof line
Stack
termination
Potential
contaminated
air ingress if
trap seal lost
W.c.
W.c.
‘Wet’ stackParallel vent
W.c.
W.c.
‘Wet’ stackParallel vent
W.c.
W.c.
W.c.
W.c.
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
p
Sewer
connection
Wet stackParallel vent
stack with cross
connections Sewer
connection
Wet stackParallel vent
stack with cross
connections
W.c.
Sewer
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
Sewer
‘Wet’ stackParallel vent
stack with cross
connections
W c
W.c.
W c
W.c.
W.c.
Roof line
Stack
termination
W.c.
Roof line
Stack
termination
connectionconnection
W.c.
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
W.c.
W.c.
W.c.
W.c.
Airflow may be drawn
from any of the connected
sub – section drainage
Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections Sewer
connection
‘Wet’ stackParallel vent
stack with cross
connections
sub section drainage
systems – total
interconnection.

14. Limitations
• Calculations do not include importantp
bioaerosol fluid dynamics such as;
• Brownian Motion
• Gravitation
• Electrical Forces
• Thermal Gradients & Electromagnetic Radiation
• Turbulent Diffusion
• Inertial Impaction• Inertial Impaction
• Particle Shape
However
• Flow direction and rate can be calculated –
approximations of likely bio-aerosol
transport mechanisms can be made.

15. Modelling flow rate and direction
6
0
2
4
6
om,-downstack,
nd
-8
-6
-4
-2
nedairflow,+intoroo
litres/secon
Modelling
confirms the
establishment of
an air exchange
between the
bathroom and
the vertical
-12
-10
0 5 10 15 20
Time, seconds.
Entrain

16. The building drainage system
Interconnection- all parts of the building are
interconnectedinterconnected
3F
4F
2F
3F
Waste water
from other
hospital
b ildi i GF
1F
buildings i.e.
labs, morgue.
GF
To main
sewer

17. The building drainage system
SARS OutbreakSARS Outbreak
Press Release WHO/70
“droplets originating from virus
26 September 2003:
droplets originating from virus-
rich excreta…re-entered into
residents apartments via sewage
and drainage systems where
there were strong upwards air
flows, inadequate ‘traps’ andflows, inadequate traps and
non-functional water seals.”

18. SARS Outbreak
Transmission routeTransmission route
Bioaerosols carried
to adjacent buildings
by wind current
Bioaerosols transmittedBioaerosols transmitted
to adjacent apartment
Infected person introduces
virus to drainage system
Bioaerosols formed
as waste is flushedas waste is flushed

19. The building drainage system
New threatsNew threats

20. Airborne transmission evidence
Forgotten knowledgeForgotten knowledge
1907: cultured airborne Serratia marcescens (then
termed Bacillus prodigiosus) from drainage
systems and detected airborne transport from one
hospital building to another via the sewer drain.
Sir William Heaton Horrocks
(1859-1941)

21. Horrocks – In good company
The Royal SocietyThe Royal Society
I N tIsaac Newton
Charles Babbage
James Watt

22. Horrocks – Other Successes
C fi d th t th f ‘M lt F ’• Confirmed that the cause of ‘Malta Fever’ was
bacteria passed on through goats milk.
• Developed methods for testing and purifying
drinking water
• Published book on bacteriology of water, one
of the first of its kindof the first of its kind.
Horrocks, William Heaton (1901). An Introduction
to the Bacteriological E amination of Waterto the Bacteriological Examination of Water.
London: J. & A. Churchill.

23. Pathogen transmission study
Hospital buildingHospital building
Environmental
conditions
Norovirus
Outbreak
3F
4F
2F
3F
Bioaerosol
transmission
Waste water
from other
hospital
b ildi i GF
1F
buildings i.e.
labs, morgue.
GF
To main
sewer Wastewater
contamination

24. Pathogen transmission study
Hospital buildingHospital building
Air sampling
Pitot tube measuring
downward airflow
Collection swab• Isolation of bioaerosols using
collection swab (UTM-RT)
Static pressure tube
• Temperature and humidity within
drainage stack (USB data logger)
• Air flow and direction (pitot tube)
Pitot tube measuring
upward airflow
USB temperature & relative
humidity data logger
Wastewater sampling
• Collection of wastewater from
main underground drain

28. Pathogen transmission study
Real Time Polymerase Chain ReactionReal Time Polymerase Chain Reaction
Samples extracted using
NucliSens® easyMAG™ system
Ct ≤ 29 St iti tiCt ≤ 29 Strong positive reaction
(abundant target nucleic acid)
Ct 30-37Positive reaction
(moderate amount of target nucleic acid)
Amplification, detection and analysis
performed in an ABI 7500 RT-PCR system
( g )
Ct 38-40Weak reaction
(minimal amounts of target nucleic acid)

29. Pathogen transmission study
RT-PCR ResultsRT PCR Results
T t d tTest date Norovirus GI Norovirus GII
Sewer Stack 1 Stack 2 Stack 3 Sewer Stack 1 Stack 2 Stack 3
01/03/2011 U U U U U U U U
10/03/2011 U U U U 2 U U U10/03/2011 U U U U 25 U U U
16/03/2011 U U U U 25 U U U
23/03/2011 U U U U 35 U U U
30/03/2011 U U U U 40 U U U30/03/2011 U U U U 40 U U U
05/04/2011* U U U U 37 U U U
26/05/2011 N/A U U U N/A U U U
U Undetected
Ct ≤ 29 Strong positive reaction (abundant target nucleic acid)
Ct 30-37 Positive reaction (moderate amount of target nucleic acid)
Ct 38 40 Weak reaction (minimal amounts of target nucleic acid)Ct 38-40 Weak reaction (minimal amounts of target nucleic acid)
*a swab of the inside surface of Stack 1 taken on this date also returned undetected for all tests

30. Pathogen transmission study
RT-PCR ResultsRT PCR Results
Samples were also tested for Clostridium deficile but was undetected.
This was due to the fact that Cdiff produces spores which are not amenable to
man of the PCR assa s a ailablemany of the PCR assays available.

31. CYCLE NUMBER AMOUNT OF DNA
0 1
1 2
2 4
1400000000
1600000000
2 4
3 8
4 16
5 32
6 64
7 128
400000000
600000000
800000000
1000000000
1200000000
AMOUNTOFDNA
8 256
9 512
10 1,024
11 2,048
12 4,096
13 8 192
0
200000000
0 5 10 15 20 25 30 35
PCR CYCLE NUMBER
A
13 8,192
14 16,384
15 32,768
16 65,536
17 131,072
18 262,144
100000
1000000
10000000
100000000
1000000000
10000000000
TOFDNA
18 262,144
19 524,288
20 1,048,576
21 2,097,152
22 4,194,304
23 8,388,608
1
10
100
1000
10000
0 5 10 15 20 25 30 35
AMOUNT
24 16,777,216
25 33,554,432
26 67,108,864
27 134,217,728
28 268,435,456
29 536 870 912
31
0 5 10 15 20 25 30 35
PCR CYCLE NUMBER
29 536,870,912
30 1,073,741,824
31 1,400,000,000
32 1,500,000,000
33 1,550,000,000
34 1,580,000,000

32. Pathogen transmission study
Temperature and Humidity
98
100
%)
Temperature and Humidity
94
96
Humidity(%
Average humidity = 96.6%
90
92
23/03/11 24/03/11 25/03/11 26/03/11 27/03/11 28/03/11 29/03/11 30/03/11 31/03/11
D tDate
26
28
30
re(oC)
Average temperature = 24.3%
22
24
26
Temperatu
20
23/03/11 24/03/11 25/03/11 26/03/11 27/03/11 28/03/11 29/03/11 30/03/11 31/03/11
Date

33. Pathogen transmission study
Airflow results – this proves that the interconnection hypothesis is
validvalid
30
Airflow Up
20
Airflow Down
0
10
rate (l/s)
‐10
0
0 1 2 3 4 5 6
Airflow r
‐20
‐30
Time (minutes)

34. Additonal Domestic system tests
Drainage System Schematic
Roof Level
(height above collection
drain = 10 m
Floor 3
Open pipe for testing
(WC Removed)
Simulates open trap
Anemometer located
here.
Bath & sink
Floor 2
Kitchen
WC
To main sewer
Floor 1
2 x Bathrooms
Utility room
2 x WCs
Smoke Pellets
To main sewer
inserted here
Collection drain

38. 20
Air Flowrate
14
16
18
Note:
Similar
10
12
ow rate (l/s)
AirFlow
Similar
Airflows
to those
4
6
8
Airfl
AirFlow
recorded
in Amoy
Gardens
0
2
4
0 500 1000 1500 2000 2500 3000 3500 40000 500 1000 1500 2000 2500 3000 3500 4000
Time (secs)

43. The DYTEQTA System
Automated monitoring methodAutomated monitoring method
 Defective fixture trap seals increase
risk of bioaerosol transmission via
the building drainage network
 Dyteqta is a sonar-like method for
establishing the status of each
fixture trap seal in a building
 Based on reflected wave theory
 Using a sinusoidal air pressure
a e ens res the test is nonwave ensures the test is non-
destructive
 System validated by: modelling System validated by: modelling,
laboratory investigations and
extensive site testing

44. Case study BuildingsCase study Buildings

45. The DYTEQTA System
Case studies
1
60
80
Case studies
Time change detection algorithm
0.5
20
40
rgauge)
0
-20
0
20
0.00 0.05 0.10 0.15 0.20 0.25 0.30
Dt>h
re(mmwater
-0.5
60
-40
-20
Pressur
Defect free baseline
-1-80
-60
Time (seconds)
Test pressure response
Dt > h
Is Dt > h over calibration period? NO, trace is reliable.
Is Dt > h during test period? YES, at tD = 0.066 seconds.
Depleted trap location? T12.

46. The DYTEQTA System
Case studiesCase studies
60
D d (AIRNET)
50
n(m)
Dundee (AIRNET)
Dundee (PROBE)
Arrol (AIRNET)
Arrol (PROBE)
30
40
aplocation
Arrol (PROBE)
Glasgow (AIRNET)
Glasgow (PROBE)
20
edictedtra
0
10
Pre
0
0 10 20 30 40 50 60
True trap location (m)

47. The building drainage system
Transmission of bioaerosolsTransmission of bioaerosols
 The building drainage system
interconnects all parts of a buildingg
 Potential cross-transmission route for
bio-aerosols.
 Every building tested had empty
water trap seals.
 Healthcare building drains have a
distinctly ‘hospital smell’ they do noty y
necessarily smell malodorous.
 Norovirus GII isolated from
t t l d f i d iwastewater sampled from main drain
of a hospital building, confirming
contamination during an outbreak.

48. The building drainage system
Transmission of bioaerosolsTransmission of bioaerosols
 Environmental conditions within theEnvironmental conditions within the
drainage system are conducive to
bio-aerosol circulation
 Current work underway to replicate
the Horrocks work reported in the
Royal Society proceedings in 1907Royal Society proceedings in 1907
and extend the investigations on the
identification of specific pathogens in
airflows.
 This work has confirmed that bacteria
such as psuedomonas spp. Can be
carried on airstreams inside a
building drainage system.

49. Th k f li t iThank you for listening