sewer infiltration monitoring

Sewer Infiltration Monitoring

David Walters BEng CEng MCIWEM

Principal Research EngineerInnovation

SWIG Sensing in Water 201524th September 2015

Sewer Infiltration MonitoringBackground

Widespread seasonal problem for many water companies

‘Unaccounted for Water’ typically caused by groundwaterentering the sewer through aged / defective pipework

Can result in internal & external flooding and pollution

Increased energy costs and wear at Sewage Pumping Stations

Increased vehicle / tanker movements(24/7 in some catchments)

Unhappy customers & stakeholders MP’s, LA’s, EA etc.

Sewer Infiltration MonitoringBackground

Thames Water experienced wide scale infiltration eventsduring the winter of 2012/13 and 2013/14

Ongoing commitment to undertake investigations andinvestment in catchments at greatest risk

Investigations include flow monitoring, catchment &groundwater modelling, PS analysis etc.

Existing site investigation techniques – lift & look surveys,CCTV surveys, impermeable area surveys, stoppering etc.

Innovation considered alternative investigation techniques,both linked to temperature monitoring

Sewer Infiltration MonitoringDTS

Distributed Temperature Sensing (DTS)

Fibre-optic cable installed in a sewer with laser light pulsedalong the length

Temperature measurement recorded at 2m intervals everyminute.

Temperature differences identify inflows to sewer

Service provided Royal HaskoningDHV with site contractor

manhole manhole

sewer pipe

laser/computerinstrument

fiber-opticcable

container

external power supply

manhole manhole

sewer pipe

laser/computerinstrument

fiber-opticcable battery pack

Sewer Infiltration MonitoringDTS Investigations

Hambleden1674m cable

Monitoring Started 8th October 2014

Monitoring Ended 11th November 2014

Cuxham1151m cable

Monitoring Started 16th December 2014

Monitoring Ended 16th February 2015

Sewer Infiltration MonitoringDTS – Hambleden Cable Installation

Sewer Infiltration MonitoringDTS Example of Results

Sewer Infiltration MonitoringDTS – Pump run times

Sewer Infiltration MonitoringDTS Results

Trial demonstrated the potential of the system andprovided lots of data

Timing of deployment critical to capture infiltrationevent

Deployment required just prior to an eventBut, this is the unknown..

Technique also required jetting & CCTV

Some operational problems – ragging

Costly

Sewer Infiltration MonitoringTemperature Loggers

Temperature measurement is used to optimise sewagetreatment processes

Considered option to identify infiltration into seweragenetworks?

Reduced temperature could indicate infiltration

Low cost equipment – around £100 per loggerSealed units – wireless data reader

Trial undertaken within a catchment with previoushistory of infiltration: Fencott & Murcott

Trial started September 2013

SLI51-KIT - USB-5Temperature Data Loggers


Comparable recordings from each logger

10

12

14

16

18

20

22

05/02/2015 07/02/2015 09/02/2015 11/02/2015

Deg

rees

C

Date

Temperature Logger Comparison Test

1

2

3

4

5

1

4

3

2

5



Very good diurnal pattern recorded


Merton


All sites - seasonal pattern over nearly 2 years


Infiltration Event Captured 2013 – 2014


Event with rainfall

1

4

3

2

5



Pump run times


Other catchments – Ramsdell

Sewer Infiltration MonitoringSummary

Temperature loggers have provided good results todate

Durable hardware – survived in the sewers

Potential to use in the network to target sources ofinfiltration or unaccounted for water

Cost effective tool for long term measurement ofcatchment performance

No confined space access needed

Trial ongoing and rolled out to further catchments

sewer infiltration monitoring

Documents