Sewage and Water Pollution in London

8/3/2019 Sewage and Water Pollution in London

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Water pollution in London: sources,

impacts and management


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A short history

1950s long stretches of the Thames Tideway hadno aquatic life

Why?

Improved since due to:

Major investment in sewage treatment in the 1960sand 1970s

Fewer industrial inputs

Impacts:

Improved dissolved oxygen levels and allowed fish toreturn to the river. (EUTROPHICATION)


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What is the situation like now?

http://www.guardian.co.uk/environment/video/

2010/dec/02/london-sewers-thames-

water?INTCMP=ILCNETTXT3486

Keep in mind the sources of water pollution, the

issues of management and how the it is

currently being managed.


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Key points from video

Only 1% of samples from river acceptable according to WHO

57 CSOs

39 million tonnes of raw sewage into Thames each year

2.8 billion litres a day of waste water

39 sewage flushes attempt to keep sewers clear of fat bergs

Only 2mm of rain puts sewer system into storm mode

Sewer system built 150 years ago cannot cope increased volumes of waste

EU Waste Water Directive hundreds of millions of pounds in fines

3.6 billion Thames Tunnel will take 96% of sewage during storm event


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Sources of water pollution

1. Surface water from roads / rooftops

2. Pollutants poured down drains

3. Bad plumbing sewage into drainage systemas opposed to sewage system

4. Sewage pollution


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CSO = combined sewage overflow

STW = Sewage Treatment Works


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An average of 39 million tonnes of sewage ayear is discharged into the Thames Tideway(2001 2009 data)

Without any mitigation measures in 10 years itis expected to rise to 70 million tonnes.

How has increased rates of urbanisation

impacted on the amount of sewage?


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From the Environment Agency:

CSOs (Combined Sewage Overflows) and stormdischarges from sewage treatment works resultin untreated sewage being discharged into the

Tideway. We have automatic monitoringstations (8 of them) that alert us when there is adecline in dissolved oxygen (DO) levels. Thisoften requires the deployment ofThamesWaters oxygenation vessels, the ThamesBubbler and the Thames Vitality, to addoxygen to the water.


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EU legislation (political factor)

The Water Framework Directive (WFD) came

into force in December 2000

Requires member states to protect, enhanceand restore, and prevent deterioration of

aquatic ecosystems.

How is London doing?


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64% ofwater bodies

are assessedas moderateecologicalstatus

34% ofwater bodiesassessed ashaving a

poorecologicalstatus

2027 targets to have 8 of 47 water

bodies with good ecological status

Government to be fined hundreds

of millions of pounds if Thames

remains polluted.


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Sources of

pollution

2009 - containmentand control failure,which includes

leaks or spillage ofpollutingsubstancesaccounted for 23%of incidents


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Sewer misconnections

Misconnections can occur when a house is extended, whenpeople make other home improvements or when a newhouse is built. Untreated wastewater from misconnectionscan flow straight into local river or stream instead of goingto the foul sewer and the local wastewater treatmentworks. (Identify reasons for misconnections)

The Environment Agency identifies the public surfacewater outfalls with significant misconnection problemsleading to public complaint. Thames Water Utilities carryout surveys of their drainage system to locatemisconnections and persuade the owners to get theplumbing connected correctly, if the owner refuses thenthe local authorityhave the power to serve Notice underthe Building Act to force the owner to carry out the work.(Draw a flow chart to illustrate the managementprocedure undertaken byThames Water Utilities.)


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Long term solutionsLondons 160 year old sewer system can no longer cope with the level of

sewage. With just 2mm of rain sewers enter storm mode, and sewage isreleased via the overflow system to prevent it backing up to streets /houses.

Additionally, the sewage works can overflow when they fill to capacityafter rainfall. When this happens excess sewage is stored in storm tanks. If

these are full, the remaining sewage is discharged into the Thames.

Three solutions:

1. Improve sewage works

2. The Lee Tunnel

3. The Thames Tunnel

http://www.guardian.co.uk/environment/2011/jan/13/london-super-sewer?intcmp=239

http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/10916.htm (video)


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1. Sewage works upgrades

In summer 2010, we started a 675m project

to modernise and extend London's five major

sewage treatment works to increase the

amount of sewage the sites can treat, greatly

reducing the need for storm discharges to the

river. (Thames Water)


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Mogden Sewage Treatment Works 140 million upgrade Will be able to cope

with 50% moresewage

Improved equipmenttherefore betterquality effluentdischarged

40% of power

requirements to bemet through poopower burningmethane fromsewage

Serves 1.9 million people

Covers 120 acresWork due for completion in 2013


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The Lee Tunnel

635 million will capture discharges from Londons largest CSO at Abbey MillsPumping Station in Stratford.

This accounts for 40% of discharges

Four miles long from Abbey Mills to Beckton

Will prevent 16 million tonnes of sewage mixed with rainwater discharginginto the river Lee each year.

Instead it is transferred to Beckton Sewage Treatment works (being expandedby 60% to cope with increased volumes).

Tunnelling started this month (Jan 2012) and is expected to finish by late2013.


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The Thames Tunnel

Width of three London buses (7.2m wide)

15.5 miles from East to West London

Up to 67m below ground

Will capture sewage from 34 most polluting

sewer overflows (CSOs Combined Sewage

Overflows) 96% of 39 million tonnes Then transferred to Beckton Sewage Works for

Treatment


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Summary

1. The Thames does not meet Water FrameworkDirective (the stick approach!)

2. Sewer system is antiquated

3. Increased capacity in sewers and sewagetreatment is being implemented by ThamesWater

4. Sewer misconnections are also being managedby Thames Water Utilities and Local Councils

5. Thames Water also oxygenates the Thameswhen low oxygen levels are recorded

Documents

Sewage and Water Pollution in London