AerialviewofMapleLodge
TreatmentWorks, Water
Hertfordshirehttp://www.howitworksdaily.com HowIt Works 051
DID YOU KNOW? Around 20 million hectares of the world’s land is fertilised with products of wastewater
Followwastewater’sflowasit is
refreshedforreuseSorting out
the sewageIndustrialwaste
Theactivitiestakingplacewithin
factories,shopsandotherindustrial
buildingsproducelargevolumesof
water.Somefactoriesproduce
toxicwaste,whichis notaccepted
in thepublicseweragesystem.Flushingwater
Everydayanaveragepersonin the
UKproduces 150 litresofwaste
water.Throughactivitiessuchas
cooking,washingandflushingthe
toilet,thelitresaddup– andit all
needssomewheretogo.Gritfiltering
Whenwaterreachesthis
tank,itsflowslowsdown.
Thisletsanygritparticles
sinktothebottom.Grit
doesn’thavetobesilica
sand,ascommonly
thought,butcaninclude
concrete,coffee,eggshells
andotherfoodwaste.Screening
Oneofthefirsttreatment
processesis screening.This
removesanymajorpieces
ofdebristhataretoolarge
fortherestofthesystem.
Plasticsandclothsare
amongthoseseparated.Removinggrit
Whenthegritaccumulatesat
thebottomofthetank,it is
scrapedawayoutofthe
systemandtakentolandfill.Primarytreatment
Intothesesizeabletanks,
sewagewaterconstantlyflows.
Enteringa largespacecauses
thewatertoslowtoa still.This
allowsfatstofloattothetopof
thebasinandanyremaining
heavieritemstosink.Biological
stage
Anymatterthat
hasmadeit to
thisstagein the
processis either
dissolvedin the
wateroris
incrediblylight
andfloats.
Microorganisms
suchasbacteria
areusedin this
stagetoactively
breakthisdown.Settlementtank
Asanessentialsection
afterthebiological
processes,thistank
removesthebacteriathat
wasaddedforusein the
previoustreatmenttank.
Todothis,wateris filtered
throughceramicmaterial.Agricultural
use
Abundantin nitrogen
andphosphorus,
condensed‘sludge
cakes’arehappily
receivedbyfarmers,
whousethemtohelp
theirsoilthriveand
restoreanydamaged
land.Thisefficient
processmeansthat
the‘waste’isn’treally
wastedatall.Treating
leftovers
Thoughit wasunwanted
in thewater,leftover
sludgehassome
desirablepropertiesfor
soil.However,forit tobe
reusedit needstobe
treatedtoremove
pathogens.After
bacteriabreaksthese
down,thesludgeenters
a centrifugethattightly
packsthewastefor
transportation.Sourcingenergy
Wasteproductsextractedhavenousein the
water,butcanbeusedasa renewablemethodof
generatingelectricity.Microorganismsbreakdown
thewastematerialstoproducemethane.Thisgas,
alongwithgasreleasedatotherstages,is then
usedforbothheatandelectricityproduction.Environment
preparation
Beforethewatercanbereleased
backintoriversandlakes,finishing
touchesneedtobeputin placeto
makeit suitableforthesurrounding
wildlifeandenvironment.
Sometimesbeneficialnutrientscan
beadded.Othertimesnutrient-
removaltechnologyis required,such
asphosphorusreduction.Toomuch
ofthisenteringlakescanresultin
increasedalgalgrowth,depletingits
oxygensupplyandkillingotherlife.Early methods
Today’s approach to managing and reusing
wastewater seems an efficient one, especially when
compared to past methods. In fact, during the Middle
Ages there didn’t really seem to be many methods in
place at all. Cesspools were often used for sewage – or
households would simply pour their wastewater into
gutters and let the rain dictate its path down the drain.
This demonstrates the importance of today’s
systems, as disposing of wastewater this way resulted
in diseases such as cholera and became a serious
threattopublichealthandhygiene.Followingthis,it
wasdecidedthatwasteshouldbetransportedaway
fromlivingareasandreleasedstraightintolakes.
Withoutanypurificationprocess,thisledtoa growing
water-pollutionproblem.The first toilets were connected
to cesspools, not sewers to
© Alamycarry sewage away© Getty© Illustration by Adrian Mann