Water June 2004 for pdf - WIOAwioa.org.au/documents/waterworks/waterworks_june_04.pdf · way to...

JUNE 2004

WATERWORKS JUNE 2004 39

Editorial CommitteePeter Mosse, Editor [email protected]

Russell Mack [email protected]

George Wall [email protected]

Direct mail to: WaterWorks Editorc/-Peter Mosse, Gippsland WaterPO Box 348, Traralgon, Vic 3844

Advertising & ProductionHallmark EditionsPO Box 84, Hampton, Vic 3188Level 1, 99 Bay Street, Brighton, Vic 3186Tel (03) 9530 8900 Fax (03) 9530 8911Email: [email protected]

WaterWorks is the publication of the WaterIndustry Operators Association (WIOA). It ispublished twice yearly and distributed with WaterJournal. Neither the WIOA nor the AWA assumeresponsibility for opinions or statements of factsexpressed by contributors or advertisers. All materialin WaterWorks is copyright and should not be repro-duced wholly or in part without the writtenpermission of the Editor.

Contributions WantedWaterWorks welcomes the submission ofarticles relating to any operations areaassociated with the water industry. Articles caninclude brief accounts of one-off experiences orlonger articles describing detailed studies orevents. These can be e mailed to a member ofthe editorial committee or mailed to the aboveaddress in handwritten, typed or printed form.Longer articles may need to be copied to CDand mailed also.

C O M M E N T

This is the sixth edition of WaterWorks.One of our original aims in publishing themagazine was to provide a day-to-dayaccount of operations in the waterindustry, warts and all. As I look back overthe previous issues I am pleased to see thatthis has well and truly been achieved. Themagazine is full of informative and helpfularticles from all areas of the waterindustry. The only thing that concerns meis that the magazine is dominated byarticles from Victoria. As WIOA continuesto move towards providing a truly nationalrepresentation of operators in Australia, ithas always been one of my objectives tosource articles from all parts of Australiaon a regular basis.

To help me achieve this I would like toappoint a subeditor in each State with thespecific task of sourcing ONE article of asuitable standard to publish inWaterWorks each year. Not a big ask byany means! Think about it - six Statesmeans six articles. These would easily fillthe June edition and we already haveaccess to the best papers from the various

Operators conferences which make up themain content of the December edition,with a few extras thrown in.

So is there anyone out there inQueensland, Tasmania, Western Australia,New South Wales, Northern Territoryand South Australia who would beprepared to put their hand up? We needpeople who have contacts and know whatis going on in their State to work with meto find ONE article per year forWaterWorks. Quite often operational staffdon’t realise that they have been doingsomething worth reporting and just need asmall (sometimes a bit larger) push towrite it.

WaterWorks will continue to beproduced regardless of the response to thisrequest but think how much better it willbe with regular contributions from allStates.

Contact me. ([email protected]) or 0428 941 013.

Peter MosseJune 2004

HELP wanted. ONE article a year!!!

CONTENTSComment 39

Did you Hear the One About...??? 41

What the Cleaner Saw! 45

Filter Media Matters 48

Successful Filter Rebuilds - A Practical Guide 53

In Brief 58

Our Cover: Transfield MechanicalTechnician, Duane Kelly, checks theoperation of a high lift pump at theSale Water Treatment Plant. Pumpcondition testing forms an importantpart of any preventive maintenanceprogram.

40 WATERWORKS JUNE 2004

C O M M E N T

President’s MessageWelcome to our first edition of

WaterWorks for 2004. It is fair to say that ourindustry has undergone a great deal of changein the past few years and it seems there iseven more on the way. When we now look atthe high tech treatment plants controlled byPLCs, the more common use of SCADA andGIS networks, the myriad of new Regulationsand Government policies relating to waterand wastewater and the updated managementsystems being implemented, it is easy towonder how we ever did the job in the past.

The reality is that we as operators haveworked with and through these changes allour working lives and have continually metthe challenges they posed head on. The oldadage of “doing more with less” has neverbeen more to the fore than at present but insome cases, the changes have put real pressureon our ability to remain productive. Duringthis time though, we have expanded ourknowledge and skills base enormously and theexpectation from our employers is that thistrend will continue. Operators must nowhave a holistic view and be able to reactappropriately to anything that impacts on

their working environment. This is a far cryfrom times not that long ago when operatorswere task focused.

Obtaining, using and being prepared toshare knowledge and skills is an area wherewe can collectively help ourselves. Operatorfocused conferences are now being stagedannually and in the coming months will beheld in Victoria, Queensland, New SouthWales and South Australia. Make sure thatyou find out about them, look through thepapers to be presented and even better, put inan abstract to tell the industry about whatyou are doing at your workplace. The bestand most interesting papers are nearly alwaysdone by people talking about real lifeexperiences and not about rocket science.

If talking on stage isn’t your cup of tea butyou do get to attend a conference, make surethat you use your time proactively. Listen tothe papers and take some notes, look over allthe trade sites and not just the companiesthat you are familiar with and mostimportantly of all, make sure you meet andnetwork with as many other operators as you

can. This gives you contacts for the futureand could help you to save many dollars fromjust a single phone call. The final tip is towrite a report to your organisation outliningwhat you got out of attending the conference.This may encourage your employer to sendyou, or other staff, next year.

The other thing we’d like to encourage youto do is to join WIOA. There are a multitudeof benefits awaiting you including access toquarterly newsletters, frequent notification ofpositions vacant through advertisements andaccess to our website along with theCorporate Members directory. You will alsoreceive invitations to attend the numerousother activities we organise at various timesthroughout the year. If you look at the cost ofbeing a member and the benefits you receiveit really is excellent value. We think that it isso good that you should encourage all yourwork mates and other water industryacquaintances to join as well.

Until next time - “Happy Operating”

John Harris, WIOA PresidentJune 2004


I’m sure that anyone who has beeninvolved in the operational side of the waterindustry for a reasonable amount of timehas collected plenty of yarns to tell over acouple of beers. More often than not theyinvolve the misfortune or stupidity ofsomeone else as we rarely like to makeourselves the subject of such yarns - it isalways a mate or acquaintance who cops it.In true Aussie spirit, just like a good fishingyarn, most of these stories tend to get betterwith time.

I’ve built up my own collection over theyears with some of them the result of nearmisses which could, but fortunately didn’t,have serious consequences and many othersas a result of more light hearted incidents.In my time I’ve seen utes and truckssubmerged in wastewater lagoons; tractorsand backhoes stuck in precarious situations;countless stories of the mobile phoneseither left on the roof of the car then beingrun over or falling out of a top pocket andinto a sewer pump station wet well; and ofcourse numerous close encounters of thereptilian kind where the serpent gets a footlonger and 3 inches fatter every time thestory is told. You know the ones!

It was with amusement, and indeedamazement, that I recently spent a day inthe car looking over potential conferencevenues in Victoria with a doyen of thewater industry, Mr Ron Bergmeier. Ron isthe owner and a director of AustralianPollution Engineering, a company involvedmainly in the management of biosolids.Ron has developed a reputation in theindustry as a straight shooter but I’ve beenaround him often enough to witnessanother side of his dry and sometimeswicked sense of humour. Some incidentsthat Ron described that day were just toogood to keep quiet and Ron has graciouslyagreed to let me relay some of them here.

Being in the biosolids game, Ron hasnumerous trucks, dredges, centrifuges andother heavy equipment in operation all thetime. One such large machine - a floatingweed cutter and harvester was to be used inPatterson Lakes, a feature lake in aresidential suburb south of Melbourne. Thesemi trailer had been backed down to theedge of the water ready for the weed cutterto be offloaded by a large crane. Theunloading was successful and the cutter was

moved out to the middle of the lake for atrial run. After a while, Ron decided to itwas time to move the now empty truckback up to the main road and hopped in.When he started it up there was a completebrake failure and the truck began rollingbackwards towards the lake. There was noway to stop the runaway truck and it finallycame to rest with the entire trailersubmerged and the cabin about half full ofwater. A very red faced Ron had to makehis way back to shore and call for a heavysalvage truck to come and pull the big rigout. Whilst awaiting the arrival of thesalvage truck, a significant number of localresidents arrived full of helpful advice - allof which Ron was in no mood to receive.When one chap raised his concerns aboutthe oil slick on the water, probably due toleaking diesel, Ron replied “don’t worrymate, we’re going to pump all the water outof the lake so I can get my truck back”.This wasn’t quite the response the residentexpected and he was last seen heading for aphone to call the local council - “we’ll seeabout this”. In the meantime, the salvagetruck arrived and extricated the errantprime mover and trailer to allow the veryexpensive repair job to the motor anddifferential to be completed. A week or solater, Ron returned to the same spot withthe now repaired truck to collect the weedcutter. Lo and behold, around 100 localresidents arrived all with video camera inhand ready for action. Some just couldn’thide their disappointment when the jobwent totally to plan and Ron drove off into

the distance without giving them an encoreperformance.

Another interesting story was actuallyquite serious and could have had disastrousconsequences had events unfoldeddifferently. The crew were working with adredge and centrifuge on wastewaterlagoons near Bankstown in Sydney. Ronwas standing on top of the centrifuge andexperienced the sensation that somethingwas just above or near him. He looked upto the see the wheel of an aeroplane passonly about 5 metres over the top of hishead. It turned out the light plane had anengine failure and the pilot was trying tomake it back to the nearby Bankstownairport. When he realised that he couldn’tget that far, the pilot decided it would bebetter to crash land into the lagoons thaninto someone’s house and tried to land onthe lagoon embankment. The planenarrowly missed the top of the dredge inthe middle of the pond and hit the lagoonembankment ripping both wheels off in theprocess. The plane skidded down the bankand eventually ploughed into the cycloneperimeter fence surrounding the plantwhich acted like a big catch net.Fortunately the pilot escaped any seriousinjury and the dredge operator wasoblivious to the fact that he had nearly beencleaned up by the powerless plane. It wasinteresting for Ron and his crew to watchthe circus arrive including the police, firebrigade, Civil Aviation Authority, theChannel 7 chopper and what seemed to beevery journalist on the eastern seaboard.

B I O S O L I D S M A N A G E M E N T

DID YOU HEAR THE ONE ABOUT...???

George Wall


After about 20 interviews, each one of theman “exclusive”, Ron ended up locking thepoor pilot into his car to keep the rest ofthe journos away. The scene wasinvestigated over and over and the planewas eventually dismantled piece by pieceand taken away over the next week or so.

Obviously there are hazards attached toworking in and around wastewater but notalways the type that readily spring to mind.At a wastewater plant in Port Macquarie,the lagoons were being desludged, andalum was being added to increase the rateof flocc formation. This process graduallyremoved most of the dissolved oxygen fromthe water and after a few days on the jobthe guys came to work one morning to finda number of dead eels floating on top of thepond. Late in the afternoon, one of Ron’smen was walking along the edge of thepond and got whacked in the back of theneck by something heavy. It turned outthat some more eels had floated up duringthe day and a pelican had decided it wasfree feed time. The pelican had picked upthe dead eel but obviously it was too heavyto carry all the way back to its nest. Thepelican had dropped the eel mid flight andthis is what hit Ron’s bloke. From that

point on, an OHS decree was made that allstaff on the site had to wear suitable PPE atall times - a hard hat with the words “eelprotection device” written of the front inblack letters. It turned into a morning ritualfor the guys to go around the pond andcollect all the eels and bury them so thatthey wouldn’t start stinking, but mainly toreduce the ammo available to the local birds

who eagerly sat around the edge of thepond waiting for their next free meal topop up.

Another hazard involving native faunaoccurred at the Darwin wastewater plant.The guys from NT Power and Water whomanage the facility advised Ron that theyhad just removed a big crocodile from theponds. Being the first time that Ron had


worked there he thought they were jokingand he and his blokes wandered around thebanks on foot and puttered around theponds all day in their little tinnie doingsludge surveys and collecting samples. Theyset up a pump to decant the water from thepond overnight and went back to town.They came back the next morning andnoticed marks in the exposed sludge at theedge of the pond. It turned out a croc about2 metres long lived in the pond and whenthe water level was lowered he couldn’t getout. Ron’s blokes found him near one ofthe control structures and one of them decided to do his best SteveIrwin impression and grabbed the croc by the tail. After all theobligatory photos were taken to sate the “disbelievers” in thesouthern States, they called the NRE people to come and get it out.It turns out that there are numerous crocs that call the lagoonshome and any over 3 metres are routinely trapped and taken away.A special line item has now been added to the site specific riskassessment documentation outlining the dangers of crocodiles.

Driving large bulldozers and excavators inside partly dewateredlagoons can sometimes hold surprises. In Auckland NZ, Ron wasworking on air drying solids in the lagoons and in the process wasgiving the Kiwis a demonstration of how to do the job properly sothat they could then take over. Most of the ponds had solid claybases but being a volcanic area, some of the lagoons had areas ofwet gooey clay. Whilst his demo was in full flight, Ron

inadvertently drove the dozer into the wetstuff and it got bogged to the top of thetracks. A bit red faced, he explained this wasall part of the service and tomorrow he’dshow them how to get it out again!!. Itturned out that on this job they “lost” 2excavators when they sank down oldvolcanic gas vents. Luckily the operatorswere able to scramble out the air conditionervent in the top of the cabin before themachine disappeared totally.

In a similar event, when Ron drove thedozer into a lagoon in Darwin it just kept

going down once it reached the floor of the pond. It sankTOTALLY with the radiator cap about 300mm below the sludgelevel. It turned out the lagoon was constructed over an oldmangrove swamp and didn’t have solid clay base.

Travel for someone as busy as Ron can also lead to someinteresting situations. Ron uses a broker to arrange his flights andbasically tells him where he has to be and when and the broker thenarranges the flights. He then faxes the details to Ron and assumes ofcourse that Ron will read the fax. A few times Ron has been caughtup in his work and not bothered to read the faxes assuming that theflight is happening when he wants it. This little trait has causedhim to arrive at the airport anything from a day and a half early to3 days late. Needless to say he pays full fare and the tickets gettransferred regularly.

This all led into a story about Ron taking his family for a triparound Australia (in 2 weeks) to use up his frequent flyer points.They were in Broome having a great time at the beach swimmingand drinking cocktails. They had great delight in laughing at all thepoor people, suitcases in hand in the hot sun, walking along thebeach. In those days there were only 2 commercial flights into andout of Broome each week and a few hours later they found out thatall those people were heading off to the airport to catch the planethat Ron and Co were meant to be on as well. As the team had tobe in Darwin the next day for business and to continue the tour,they had to charter a small plane to take them there. The cost ofthis exercise was $4,000 ($2,000 each way) and the flight was sorough that they were all airsick for most of the journey. It turnedout that the “free” trip around Australia was much more expensivethan originally anticipated.

Ron’s dry sense of humour came to the fore on a trip fromBendigo to Sydney. Ron and two of his staff were sharing the cabinof the prime mover when one of the guys got a blood nose. Beingblokes, hankies or tissues were not often packed and the poor guyended up getting blood everywhere, including all over his face. Thetrio pulled up at a busy truck stop so he could clean himself up.You can imagine the looks the poor guy got when he stepped out ofthe truck with blood everywhere. Not one to let a chance go by,Ron waited until everyone was looking and then yelled at his guy atthe top of voice “give me any more of your s**t and you’ll copanother one”. As you can imagine this freaked out the majority ofthe people there!

There were numerous other stories relayed that day which I’mquite sure the censor would be interested in if I were to elaborateon them in writing. For the protection of the innocent (in mostcases not Ron) they won’t be revealed here!!!

The AuthorGeorge Wall ([email protected]. gov.au) is Secretary ofWIOA and Wastewater Systems Specialist at Goulburn ValleyWater. Ron Bergmeier owns and operates Australian PollutionEngineering.



What secrets are hidden away in thedark watery recesses of your clear waterstorages and tanks? Layers of silt, deadpossums, wasps, rusted and corrodedfittings, or failed baffle curtains?

Because of the continual demand onwater supplies it is often very difficultto assess the inside of tanks, basins andreservoirs. One way of maintaining thesupply of water to consumers andassessing the inside of water storages isto use divers. Divers should meet allnecessary industrial competencies,qualifications and standards and theyshould also be in tune with the potablewater industries increasing pressures tomeet local and international standardsin supplying high quality drinkingwater.

Data collected by the divers via writtenreports, digital photos and narrated videocan supply useful information for themaintenance and planning departments.

Sometimes however the informationretrieved is somewhat unusual andunexpected. The following are someaccounts of unusual findings by the diversfrom inside water storages. Could this bewhat is inside yours???

Open tanks or basins encourage varioustypes of flora to grow prosperously. Ourteam has literally had to chop through 4-meter high forests of weed and have foundoutlets blocked by long plumes ofaccumulated weeds.

Animal life can be a bug bear (pardonthe pun) to operators in the waterindustry. It’s very important to spend timeplugging up all those little holes to preventthe little creepy crawlies from getting afree drink. Not only is it disturbing tohave dead animals in your storage but theychew up disinfectants.

Common animals we have found instorages include birds, spiders, possums,worms, centipedes, wasps and even dogs.All these may be dead or alive! One tankin Adelaide had never had a chlorineresidual until after divers had cleaned it.The floor was cleared of hundreds ofthousands of centipedes.

In central Victoria a storage tank had30% of the floor covered in wasps. Theyhad nested in an upstream tank that wasde-watered for maintenance. When the

tank was re-commissioned the wasps werewashed down to the next tank.

Another tank had what seemed to bethe Victorian breeding grounds for ratherlarge huntsman spiders. These are not thedivers closest friends as they appear evenbigger underwater. On one particular job

the diver entered the tank to carry out histask. Within a minute or so he returned tothe roof with a live huntsman that hadsettled inside his mask during set-up. Hedescribed the appearance of the spider assimilar to the alien creature attackingSigourney Weavor.

W A T E R S T O R A G E S

WHAT THE CLEANER SAW!Peter Norder, Neil Whitelaw, Craig Jones

Crack in concrete Corroded ladder


Holes in floor plate Outlet pipe resting on roof

Sediment Wasps

Weed forest

Weed in outlet


Most water storages have some sort ofinternal fittings. Internal steel fittings are ina harsh environment and difficult tomonitor. We often find rungs of ladderscrumble under our feet, stillage pipes havecorroded away and some tanks appear to beonly standing up because of a coat of paint.

Steel Rio within concrete columns canswell and break away large portions ofconcrete. Large deep cracks are often foundin the floor and walls of old concrete tanks.

Aluminium fittings are often thought tosolve corrosion problems. Poor insulationto other metals can allow the aluminium tocorrode quickly. One particular tank inAdelaide looked like a shearers shed withthe amount of corroded material on thefloor.

Sometimes, old fittings that cannot beremoved from the tank are left to corrodeaway within the tank. In one case anAluminium boat was left in a tower to serveas a platform. The boat is now severelycorroded and is completely unsafe to standin. It can’t be removed as it does not fitthrough the hatch and is 30m aboveground!!!! Wonder what the Aluminiumresidual is? Any bets on greater than 0.2mg/L???

An unusual find in a covered basin insouthern Victoria was a 90meter HDPEoutlet pipe that had fractured at the wallmount and was floating under the cover foran unknown period of time.

And then of course SEDIMENT. Howmuch you say? As much as you couldimagine and then some more. Somestorages have not been cleaned forsometime. One basin measuringapproximately 100m x 100m had up to1.5m of sediment in it. This took 28 daysto clean.

So what is it like to work at cleaningstorages? Some jobs have required divers toendure extreme climatic changes. We havehad to survive the 40+ degree heat of Cobarin central NSW and experienced the uniquesensation of snow falling on us (or lack ofsensation) in Hobart.

The AuthorsPeter Norder ([email protected])is owner and Craig and Neil are diversworking for Nordical Diving Services(0409 380 511). The company is based inGippsland and provides fully qualifiedpotable water dive services to four states ofAustralia.


Corroded stillage pipe Corroding boat

Dead possum Fenceline rubbish

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W A T E R T R E A T M E N T

FILTER MEDIA MATTERSBruce Murray

Filter media specifications and analysissheets include many terms that are notalways clearly defined. This paper attemptsto shed some light on this grey area.

1. Filter MediaFilters used in water treatment consist of

several layers of media: from the variouslayers of coarse, medium and pea gravel atthe bottom, to the coarse to medium layersof sand in the middle and the finer sandand/or filter coal used to carry out the bulkof the filtration, on the top of the filters.

Coarse gravel layers are sometimesreplaced with garnet that is heavier andmay therefore require fewer layers.Activated carbon would replace sand orfilter coal in a granular activated carbon(GAC) or biological activated carbon(BAC) filter. Activated carbon can even beused as both a filter media and organicsadsorbent in some cases.

The coarse gravel and sand layers supportthe main filter media and aid in the evendistribution of air and water. Gravels aregenerally specified to be within a maximumand minimum size range. The top layer(s)of sand and/or filter coal are usuallyspecified to have an effective size (ES) anduniformity coefficient (UC). All of thisinformation is determined through sievingof the media.

In addition, various physical propertiesmay be specified to ensure good quality,durable media.

2. Media SievingTo determine the size characteristics of

any filter media, a weighed quantity of themedia is shaken through a stack of sieves.The sieves are stacked with the coarsestsieve on top down to the finest at thebottom. A pan placed at the bottom of thestack collects any fine media passingthrough all of the sieves. The smallest andlargest sizes can correspond to the limitingsizes specified. The quantity of mediaretained in the pan and in each sieve iscollected and weighed.

2.1. Mesh NumberMany suppliers quote media as a size

range in mesh numbers. Mesh number isthe number of openings per lineal inch in asieve measured from centre to centre of thewires. However the aperture size dependson the wire thickness and thus sieves with

thicker wires have smaller apertures. Thestandard sieves used by the supplier(usuallyUS or British) and the relevant aperture sizeused should be checked with the supplier.

The test method commonly used is theAmerican ASTM - C136. Mesh Numbersand corresponding grain sizes are given forthe example media in Table 1.

2.2. Percent RetainedThe amount of media retained on each

sieve (% retained) can be calculated asfollows: % retained = (Weight of media retained oneach sieve x 100) / (Total weight of mediatested).

2.3. Percent PassingThe cumulative percentage of media

passing any sieve is the sum of all of themedia below that particular sieve and canbe calculated as follows:

Table 1. Example of Media Sieving Results.

Sieve Aperture Size (mm) ASTM Mesh No. Weig ht Retained (g) % Retained % Passing

2 10 1.23 0.4 99.61.7 12 3.54 1.1 98.51.4 14 9.54 3.1 95.4

1.18 16 21.36 6.9 88.51.0 18 116.13 37.6 50.9

0.85 20 120.66 39.1 11.80.71 25 17.19 5.6 6.2PAN 19.26 6.2 0

Total 308.91

Figure 1. Plot of Filter Media Sieve Analysis.Bags of filter media being lifted during afilter rebuild.



% passing = (Sum of % of material retainedon all lower sieves) + (% of material retainedon pan).

An example media is analysed in Table 1.Thus 0.4% of this media is larger than 2

mm in size and 6.2% is finer than 0.71mm. 93.4% of the media is within the sizerange 0.71 to 2 mm.

This data is plotted in Figure 1.

2.4. Effective SizeThe effective size (ES) of a media

represents the sieve size (mm) for which10% of the media passes. This is referred toas d10 and is a measure of almost thesmallest size of the media - only 10% of themedia is smaller than this size. The ES isdetermined from the plot of sieve size(mm) versus the cumulative percentagepassing each sieve size (Figure 1).

In the example above the effective size ofthis media is 0.82 mm.

2.5. Uniformity CoefficientThe uniformity coefficient (UC) is

determined by dividing the size for which60% of the media passes by the size forwhich 10% passes. That is the ratio(d60/d10). The UC is a measure of howuniform in size a particular media is butignores the largest particles in the media.

From the example above, the uniformitycoefficient is 1.27 (1.04 ÷ 0.82).

The lower the UC the more washed anduniform the media. However, the lower theUC the higher the cost of the media. Ahigh quality, well-washed filter mediagenerally has a UC of around 1.3. Mostmedia is specified to have a UC of less than1.5 and preferably less than 1.3. Granularactivated carbon however is usuallyspecified to have a higher UC (less than 1.8

or 2) unless it is being installed within aconventional filter. Higher UCs indicatethat more fines are present in the media.

3. Physical Properties

3.1. Filter CoalFilter coal supplied for dual media filters

should be hard, durable cubic grains, free ofclay, shale and other foreign matter andwith a very low fines content. Filter coal isusually specified to be in accordance withthe US standard AWWA (American Waterand Wastewater Association) B100-01except that the material available inAustralia is bituminous coal (notanthracite).

Fines appear as a powdery black materialthat floats when the media is first coveredwith water. They are largely removedthrough initial backwashing but canremain suspended in the waste wash water

passing through lagoons and leading to thedischarge of black water in thesupernatant.

Apart from effective size and uniformitycoefficient the following parameters areusually specified for filter coal.

The specific gravity (or relative density)relates the density of each grain of media tothat of water (at 4ºC) whereas the bulkdensity is the apparent density of a quantityof the media as it naturally packs (includingair gaps). For example, coal with a specificgravity of 1.5 (Table 2) means that theindividual grains of filter coal are 1.5 timesas dense as water and will thus sink. Atypical filter coal has a bulk density of 0.7t/m3 which simply means that 1 m3 of thesupplied media will weigh 700 kg.

Acid solubility is measured to ensure thatmost of the material is actually coal anddoes not include significant quantities of

Table 2. Filter Coal Requirements.

Parameter Typical Values Test Method

Specific Gravity 1.4 to 1.6 AS 1289.3.5.1Acid Solubility (1:1 HCl) 1 to 5% max AWWA B100-01Hardgrove Grindability Index (HGI) 50 MAX AS 1038 Part 20Bulk Density 0.65 to 0.75 t/m3 AS 3899-91

Table 3. Filter Sand Requirements.

Parameter Value Test Method

Specific gravity 2.6 to 2.7 AS 1141.40Acid Solubility (20 % HCl) 2% MAX AWWA B100-01Friability < 10 % @1500 strokes Degremont FriabilityQuartz Content 98% MINImpurities (fines) (<75 µm) < 0.2 % ASTM C117Bulk Density 1.5 to 1.7 t/m3 AS 1141.4



acid soluble impurities. A caustic solubilitytest can also be carried out in 1% NaOH at88oC. For this test a 2% maximum isrecommended.

The HGI tests the toughness of the coalwhich is important since a soft coal canbreak down during repeated backwashingin a filter. In the HGI test a preparedsample of coal is pulverised in a ball mill.The pulverised coal is sieved and its sizecompared with those of standard coals.There is also a Mohs’ scale of hardness test

but this is not as good a measure ofdurability.

3.2. Filter Sand for Dual or Single MediaFilters

Filter sand used in dual or mono-mediafilters is usually specified to be natural riversand from quarries or dunes that has been

suitably washed, calibrated and evenlyground.

Filter sand should be clean, hard,rounded and consist of durable particles inaccordance with US standard AWWAB100-01. It is usually specified to be of thehighest grade pure quartz (SiO2 > 98%)

Table 4. Coarse Sand and Filter Gravel Requirements.

PARAMETER VALUE TEST METHOD

Specific gravity 2.6 to 2.7 AS 1141.4Acid Solubility (1:1 HCl) Gravel: 1% MAXSand: 2% MAX AWWA B100-96Impurities (fines) (<75 µm) < 0.2 % ASTM C117Bulk Density 1.5 to 1.7 t/m3 AS 1141.4

Table 5. Granular Activated Carbon Requirements.

PARAMETER VALUE TEST METHOD

Iodine number 900-1300 mg/g carbon ASTM D4607-94Moisture content 3 - 8% ASTM D2867-99Abrasion resistance Greater than 70% ANSI/AWWA B604 Section 5.2.6.3 Bulk Density 0.25 to 0.6 t/m3 AS 3899Ash content: 3-15%Water soluble ash content 4% maximum

Bags of filter coal stacked ready for use.


and should be free of all mica, clay, shaleand other foreign matter.

The following physical parameters areusually specified.

Again, the specific gravity relates thedensity of each grain of media to that ofwater and the bulk density is the apparentdensity of a quantity of the media as itnaturally packs. Note that the specificgravity for the sand (2.6 - 2.7) is muchhigher than the specific gravity for the filtercoal (1.4 - 1.6). Thus in a dual media filterthe sand sinks more rapidly than the filtercoal after mixing during air scouring (aloneor with water washing) and thus the layersof media are reformed during the waterwashing phase.

Acid solubility and impurities aremeasured to ensure that most of thematerial is actually sand and does notinclude significant quantities of acidsoluble or other impurities. The quartzcontent is measured to ensure that the sandis of the highest purity. Some otherminerals found in some sands can breakdown in the abrasive environment of afilter backwash.

Friability is also a measure of how easilysand fractures or crumbles. For thefriability test, the sand is placed inside aDegremont apparatus that repeatedlyimpacts the sand. After 1500 impacts it ispreferred that less than 10% of the sandhas broken down, however the test methodstates that 15-20% friability is satisfactoryfor filtration.

3.3. Coarse Sand and Filter GravelThe coarse sand supplied as support

layers for the primary media should besuitably washed, calibrated and evenlyground. It should also be comprised ofclean, hard, rounded and durable grains ofhigh grade pure quartz and should be freeof all mica, clay, shale and other foreignmatter (also refer to AWWA B100-01).

Filter gravel should be clean, hard,rounded stones and tend toward a generallyspherical or even shape. The gravel shouldpossess sufficient strength and hardness toresist degradation during handling and useand should be free of impurities such ascoal, roots or twigs.

The coarse sand and filter gravel shouldcomply with the following requirements:

3.4. Granular Activated CarbonGranular activated carbon (GAC) is

employed in filters to adsorb organiccontaminants such as tastes and odours,algal toxins and pesticides. With ozonationup front, the GAC filter becomes biological(BAC) providing a longer life for the GAC.Coal, wood and coconut-based activated

carbons are most commonly used in theseapplications and each has differentcharacteristics.

GAC should be in accordance withANSI (American National StandardsInstitute) / AWWA Standard B604-96 andcomply with the following requirements.

The particle size distribution should be 5to 15% maximum on the upper sieve(specified maximum size) and 5%maximum through lower sieve (specifiedminimum size).

Effective sizes of GAC are typically 0.6-1.2 mm, with a maximum uniformitycoefficient (UC) generally specified to be1.8 to 2. Lower UC may be specified wherethe GAC is also to double as filter media.

The iodine number gives a measure ofthe adsorptive capacity of activated carbon.The higher the better (see Table 5). Themethylene blue number or molassesnumber can also be used.

Abrasion resistance is measured throughthe Ro-Tap abrasion test. It is a measure ofthe percentage retention of the originalaverage particle size after the media hasbeen subjected to the action of steel balls ina Ro-Tap machine.

Water soluble impurities such asphosphorus, manganese and iron may alsobe present in the carbon and are usuallyspecified to have a maximum concentrationof around 5 mg/kg to minimise leachingafter installation. Because higheraluminium concentrations are found inmany coals and because aluminium isusually less of a problem duringcommissioning, a maximum concentrationof 25 mg/kg is usually specified foraluminium.

In some carbons, significant flotation ofthe carbon may occur in the wetting phase.This material is removed and disposed of.The floatable component of the GACshould be as low as possible (0 to 10%).

Fines are backwashed out, as for filtercoal, over several initial backwashes.

4. Filter Media Selection and DesignTraditionally, filter design was based on

the use of fine grained media to polishclarified water. Over recent decades the roleof the filter and the design of the filtermedia have changed. By increasing thedepth of the filter bed and the size of thefilter media, greater storage space isprovided within the filters and there is lessflow resistance. Higher filtration rates canthus be employed leading to filters with asmaller cross sectional area (footprint). Thehigher potential for turbidity breakthroughof such filters may be controlled by usingfilter aids (polyacrylamides) to improve

adsorption of the floc to the filter media. Asecond layer of finer sand beneath a coarserlayer of filter coal (dual media filter) alsoassists by providing a polishing filter layerbeneath the bulk floc filtering layer.

Finer media that achieves mostly surfacestraining is usually 0.6 to 1 mm ES,whereas larger media that allow greater bedpenetration can be up to 2 mm in ES.Most deep bed coarse media filters arebetween 1.2 and 1.7 mm ES. The depth ofmedia used is preferably 1000 times theeffective size (or more), thus a 1.7 mmfilter coal or sand filter will have aneffective depth of approximately 1.7 m.With dual media filters the lower sand layeris also included in the calculation.

Support layers of sand and gravel usuallystart with a bottom layer of coarse gravel(eg 12 to 20 mm) and work up throughlayers of medium 6 - 12 mm and pea gravel3-6 mm to a coarse sand (1.5 to 3 mm) andthen possibly a medium sand layer(depending on the size ranges of theeffective filter media layer(s) above). Thesize range of each layer of gravel and sandshould overlap with the size range of thelayers both above and below to maximisethe stratification of the bed. The gravel andsand layers require a minimum depth of100 mm but a depth of 150 mm or more ispreferred to minimise disruption of thelayers and for ease of installation. The sizeselection and depth of gravel depend on thefilter underdrain design.

GAC selection depends on organiccontamination types and concentrations.Typical design parameters are based onachieving an empty bed contact time(EBCT) of anywhere between 5 and 25minutes. The EBCT is the contact timethat the water being treated has within theactual activated carbon bed at design flowrate.

The preferred media selection dependson raw water characteristics, targeted waterquality, and water treatment plant (WTP)design and can be evaluated by setting uppilot columns of media or through trials inexisting plants or from experience withsimilar waters in similar WTPs.

The AuthorBruce Murray ([email protected])owns and manages City WaterTechnology (www.citywater.com.au) acompany of specialist water engineers,working in all aspects of water treatmentand operating since 1990.



IntroductionMurphy’s Law seems to make its way

into the business of Water Treatment, andevery now and again, the time will comewhen inadequate operational proceduresand/or structural or other design faults willadversely affect a filter’s performance, to thepoint where it may need to have itsunderdrain system inspected and repaired,and its media replaced or topped up.

This article aims to describe the stepsthat need to be taken in order to ensurethat a filter is rebuilt successfully, withminimal operational disruption, minimalstress, and optimal use of hired plant andlabour resources.

The First Step

1. Filter Monitoring ProgramThe first step in the filter rebuilding

process should have occurred many monthsbefore any actual works were undertaken.In an ideal world, the filter in questionwould have been thoroughly inspected aspart of a routine filter monitoring program,and its state of health will have beenassessed in relation to other filters withinthe organisation. The filter in question willhave been selected for rebuilding based on aseries of organisational priorities. Thesepriorities will include, but not be limitedto: the number of customers supplied bythe water treatment plant, the age of thefilter, the ease of completing a rebuild (e.g.can the unit be taken off line for anextended period of time, and can the site bereadily accessed by heavy plant andequipment), the severity of the problem,and the risk and consequences ofcatastrophic failure. The timing of therebuild will have been chosen carefully toensure that security of water supply is notadversely affected (cooler months) andsufficient resources are available tocomplete the task (e.g. full staffcomplement on deck).

In the real world, sometimes filters failunexpectedly. A filter failure could bedetected as violent explosive regions or deadspots in the filter during air scour orbackwashing. The filter may have blindedoff for some reason (usually inadequateoperating procedures), the media may havecracked away from the walls, or it may beexperiencing constant turbidity

breakthrough. This usually happens at themost inconvenient time (when demand forwater is highest, staffing resources arelowest, and suppliers are difficult to reach(does Christmas/New Year ring a bell foranyone???)). Rebuilding a filter under theseconditions is extremely stressful foreveryone involved, disrupts normaloperations and incurs considerable financialcosts to the organisation.

The principles of filter rebuilds are thesame under both sets of circumstances, butare much easier to manage when carefullyplanned as part of a preventativemaintenance program, rather than asreactive maintenance due to an emergencysituation.

2. Budget ProvisionFilter rebuilds are expensive exercises,

and budgets need to be carefully plannedmore than twelve months in advance toallow the works to proceed in a timely, safeand efficient manner. Ideally, the budgetwill have been prepared as a direct result ofthe findings of previous filter inspections aspart of an ongoing filter monitoringprogram.

Preparing to Start

3. Media assessment, selection andordering

Refer to as-constructed drawings of yourfilters as a starting point to determine yourmedia requirements. If your filter has lostmedia over time, remedial action may be assimple as adding new media to top up whathas been lost.

At treatment plants that have more thanone filter, it is best to try and match thenew media as closely as possible to theoriginal media. This will minimise dramaticperformance discrepancies between newand existing filters once the new filtercomes back on line. However, if youdiscover that the original mediaspecifications are not adequate to producethe desired filtration performance, this maybe an excellent opportunity to reassess thefilter media design in an attempt to getbetter performance out of the filter.

4. Selection of Appropriate MediaGrades

Optimum filtration performance isachieved when all things are correctly

designed, specified, acquired, installed andtuned. Filter media is no different. A lot oftime and effort needs to go intodetermining the optimum depth, type andgrading (particle size and material type) offilter media.

Text books and engineering conventionsusually specify filter media size and rangeby stating an effective size (ES) anduniformity coefficient (UC). The ES is atthe bottom end of the size range for thatmedia. It is the size of the grain inmillimetres, such that 10% by weight of allmedia in the sample are smaller than thatsize (d10). Finer media that achieves mostlysurface straining is 0.6 to 1 mm ES,whereas larger media that allow greater bedpenetration can be up to 2 mm in ES. TheUC is the ratio (d60/d10) where d60 is thegrain size where 60% of the media is finerthan that size. The UC is a measure of howuniform in size a particular media is. A UCof 1 indicates a media of all one size. Mostmedia is specified to have a UC of less than1.5 and preferably less than 1.3.

However, the majority of suppliers quotematerials in ‘Mesh size’ or size range. Whenviewing the typical analysis it is oftendifficult to convert Mesh size back to ESand UC. ES and UC can be determinedfrom a sieve analysis of the media andplotting % passing versus mesh hole size.Mesh number is the number of holes persquare inch in a sieve.

Our experience shows that when carryingout refurbishments of filters, what yourequire is not always what is readilyavailable from suppliers. Older filters tendto be constructed of high quality materialswith very tight tolerances, and neither thematerials nor the tight tolerances arecurrently manufactured on a routine basis.For example, most of the older filters thatwe have refurbished have high qualitycrushed quartz as the support gravel.Crushed river stone is more commonlysupplied today but crushed river stone isless consistent in material type and oftenhas a lot of foreign material in it.

You may have to shop around, pay morefor further processing or as an absolute lastresort, modify the original designspecification. Extreme caution must beexercised if you choose to modify theoriginal design specification, as there are


SUCCESSFUL FILTER REBUILDS - A PRACTICAL GUIDE

Michelle Colwell


very specific design parameters to follow indetermining gravel and sand layers and theydepend on the design of the underdrains.Unorthodox gravel layers can lead tomultiple problems within a filter, and allsorts of other problems can be created if thecomplete design is not carried out carefully.

For more technical information regardingthe selection of appropriate media for yourfilters, refer to Kawamura (1991).

5. Media QuantitiesBe sure to order at least 10% more of

each grade of gravel or sand (or filter coal),and clearly state the units of calculation. Asoperators, we will usually state ourrequirements in m3, but suppliers willquote in tonnes. Given that the differentmedia grades have varying packingdensities, you can be caught short if you donot carefully check your order against thesupplier’s quotation. Ordering extra sand isespecially important, as the majority of thisextra sand will be lost as fines when thefilter is first backwashed and fines skimmedprior to bringing it into service.

6. Media Transport, Packaging and LeadTimes

Most bulk media suppliers will providefilter media in 2t bulky bags. Experienceshows that these bags are cumbersome tomanoeuvre into tight spaces, are difficult toopen (a knife must be used that quicklybecomes blunt) and it is very difficult tocontrol the rate of emptying the bag once ithas been slashed open. Bag fragments alsoend up mixed in with the filter media, andthis should be avoided where possible tomaintain the integrity of the newly laidfilter bed. A much more serviceablearrangement is to request the supplier toprovide the media in 1t chute bottom bags.You will have twice as many empty bags todispose of after the job is complete, but youwill save yourself a lot of time and worry byusing the smaller chute bottom bags.

Also take into consideration the ease ofhandling the bags when they arrive on yoursite. It is much easier to remove bags froman open topped semi trailer with a suitablysized forklift (which may need to be allterrain type) or crane than it is to try andextract bags from an enclosed roof taut linertrailer.

Media may need to be transported toyour site from interstate, and delivered bydrivers who are unfamiliar with the localarea. It is far better to order the media toarrive at least 3 days prior to thecommencement of the filter rebuild job,than it is to try and co-ordinate more thanone activity involving heavy vehicles on siteat any one time. Also take into

consideration site access arrangements.Semi trailers can usually access most sites,but B-double trucks often cannot negotiateresidential streets or narrow unsealed roads,and require large open areas to use asturning circles. Make sure that you clearlyexplain site access limitations to thecompany that will be transporting themedia to avoid unnecessary hiccups ordelays with respect to unloading.

7. Laying out the MediaWhere possible, when unloading the

truck, organise the bags of media to belined up in groups according to the mediagrade and the order that the bags will needto be placed into the filters. Spray paint thelayer number (e.g No 1 for the most coarsegravel layer) onto the outside of the bags influoro paint. Doing this before the craneand dogman arrive, and explaining what thenumbers are for to the crane driver anddogman will save you a whole lot of stressand worry on the day of relaying the media.Doing this also allows you to double checkthat the right bags are on the hook, beforethey are opened, when they are suspendedover the filter cavity.

Dismantling The Filter

8. Confined Space Entry - Permits, RiskAssessments and Emergency Plans

In most cases, filters will be classified asconfined spaces. It is therefore vital thatappropriate Confined Space EntryProcedures be followed, and all associatedprotective and safety equipment is availablefor use. Prior to entering the filter, athorough risk assessment of all the tasksthat will be undertaken as part of the jobmust be carried out and documented, andappropriate steps taken to avoid orminimise any hazards associated with

working in the confined space. Anemergency plan should also be completed.The content of these documents must bemade known and thoroughly understood byall members of the workgroup. A workpermit must also be used to ensure that allnecessary physical, mechanical and electricalisolations have been satisfactorilycompleted.

9. Removing the Existing Filter MediaTo reduce manual handling injuries, and

to speed up the rate of dismantling the oldfilter, the use of a well maintained suctiontruck is recommended. It is important torequest that the suction hoses are cleanedand disinfected prior to your job to avoidcontamination of your filters from residualsewage. It is also important to ensure thatall the equipment in use is in good repair.Sand and gravel are very heavy and abrasive.Poorly maintained equipment will quicklyblock or have holes worn in it that willreduce suction efficiency. Usingsubstandard equipment could add an entireday to your refurbishment job, and cost youmore money than you budgeted for.

Remember too that most contractorsstart charging you from the moment thatthey leave their depot, and stop once theyreturn. To minimise the payment ofpenalty rates, it may work out to be cheaperto hire the truck for two days even thoughyou estimate that the job will take only one.It is much easier to cancel equipment thatyou finish using early than it is to try andextend the use of equipment that is usuallyheavily booked in advance.

10. Disposal of Existing Filter MediaTransporting the waste contents of the

suction truck to an appropriate disposalsite, dumping the media, then returning thetruck to the work site is extremely time


Figure 1. Lowering bags of media into filter cell.


consuming, and is effectively “dead time”with respect to removing the media fromthe filters. Do your cost / benefitcalculations (time versus money). It maywork out quicker and cheaper to hire a largewaste skip and front end loader / miniexcavator and dispose of the skip contentslater than to incur the travel down timeassociated with transporting the waste to anoff site dumping point. Also make sure thatyou have enough people on site to completethe suction exercise without having to stopthe truck. To minimise fatigue, rotate thestaff controlling the suction hose frequently,and ensure labourers have frequentstaggered refreshment breaks to keep theirenergy and fluid levels up.

11. Recycling MediaIn my experience, recycling media by

segregating it for later return to the filters ismore hassle than it is worth, and it bringswith it the uncertainty of whether thereturned media is contaminated, becausethe suction action may have removed non-uniform layers of media. If you wish torecycle media rather than dump it inlandfill, approach local garden suppliersand/or schools and kindergartens. Gardensuppliers tend to like the larger gravels, andschools and kinders may want to top uptheir sandpits. However, if you decide to dothis, you must bear in mind that kindersand schools are unlikely to allow the truckon site during school hours, and this willimpact upon how the dumping is organised.It is also important to ensure that the mediais clean and possibly disinfected prior toremoval from the filters for this application.

12. Exposing Air Scour and/orBackwash Laterals

Vacuuming will become difficult onceyou get down to the level of any air scour orbackwash pipe work. To avoid damagingstructures, you may need to use large piecesof plywood to evenly distribute yourweight. Sometimes it may be necessary tosacrifice a few laterals by removing them(by whatever means possible) to allow alarge enough space for the vacuum hose endto work in. Make sure that you havesufficient spare pipe lengths and pipefittings on site to repair any breakages. Theunderdrains are also a crucial part of thefilter and must be restored exactly as per thedesign (level and with appropriate sizedholes or nozzles at precise spacings). Thesooner you make the repairs, the longer thetime that any glue will have to cure beforethe filter is refilled.

13. Removing all Traces of SandIt is essential that all sand is removed

from the filter cell, so pay particularattention to removing all traces of the sand.

You will need to feel around with your barehands to see if there is any leftover grit lyingon the bottom of the filter. Use a hose toflush the grit to an area where the vacuumcan pick it up.

14. Repairing Air Scour LateralsIt is vital to ensure that there is no sand

trapped inside the air scour laterals. Manyfilter failures can be attributed to this.Unblocking air scour laterals and flushingthem clean is a tedious and boring task, butit must be done properly to ensure that thefilter functions correctly once placed backon line. Once again, refer to drawingswhere possible, and ensure that sufficientspare pipe fittings (barrel unions, O-rings,joiners, glue, correct diameter pipe, endcaps etc) are available to ensure thatcompleting these repairs exactly to thedesign does not impede the progress of thefilter rebuild.

15. Repairing Internal StructuresWhen the filter is bare, it is often a good

opportunity to complete maintenance onunderwater fittings / seals that have notbeen attended to since installation. LooseChemset bolts can be replaced, nuts andbolts can be tightened, and any weldingrepairs can be done. Use a Hot WorkPermit if welding or grinding is required,and ensure that any plastic fittings areshielded from sparks.

16. Checking the Air Scour PatternAfter replacing the air scour laterals, and

BEFORE any new media is added to thefilter, it is important to check that the airscour pattern is even. It is much easier tofacilitate remedial action at this stage, ratherthen when the filter has been rebuilt. Tocheck the air scour pattern, fill the emptyfilter cell with water to a levelapproximately 150mm above the level ofthe air scour laterals. Run the air blower,


Figure 2. Emptying sand out of suction truck.

Figure 3. Exposed air scour laterals.



and observe the pattern. The air should beevenly distributed throughout the cell, andshould appear in all sections of the filter atroughly the same time. There should not beany “wave action” associated with the airscour.

Backwashing should also be checked forsatisfactory performance prior to theinstallation of media.

Rebuilding The Filter

17. Relaying the Gravel in the Filter BedCareful relaying of the filter bed will

ensure a successful rebuild. Careless relayingof the bed by not paying attention to thesmall details will result in a dodgy job andyou will have wasted lots of time, energyand money. Before adding any new media,use a level and paint to mark the walls witheach of the media layers. Make your linesabout 25mm thick if possible. Experienceshows that making the top of the line thetop of the media will make it easier to getthe media layers level (within 15mm).

It is very important that the media is laiduniformly, with no areas of increasedcompression. After levelling the coarsestgravel layer, (a concreting screed is a usefultool, but ensure that the screed length doesnot interfere with internal fixtures in thefilter cell), use plywood boards to stand onto evenly distribute your body weight. Thiswill prevent footprints in subsequent finergravel layers. Walking directly on the gravelwill create areas of localised disturbancewhere gravel layers may accidentallybecome mixed and these spots will also bemore compressed than other areas of thefilter. This may cause problems with theeven distribution of air and / or water oncethe filter comes back on line, so it is betterto take the extra time and care to lay thefilter bed properly.

To avoid disturbing the surface of themedia when adding subsequent medialayers, lay a light piece of plywood onto themedia surface and gently open the chute ofthe media bag to allow a slow controlledrelease of a small amount of media. When asmall pile has formed, gently remove thesheet of plywood, and use the pile tocushion the impact of subsequent additionsof media. You will need hearing protectionwhen adding the gravel layers, and youshould wear respiratory protection at alltimes when adding media to avoid inhalingsilica dust.

Laying the gravel correctly is the mostimportant part of relaying the filter bed,and this must be done with extreme careand attention to detail. This will take quitesome time, and labourers will be reluctantto comply with the level of detail and care

required, but persevere and be prepared tocop a bit of ribbing for being so pedantic. Itwill pay off in the long run.

18. Relaying the Sand in the Filter BedCommence laying the sand as you would

the gravel, but once a significant pile hasdeveloped, you may abandon the plywoodboards and stand directly on the sand. It isOK to stand on a reasonable depth of sandbecause the sand layer will fluidise duringbackwashing and will evenly redistributeitself in the filter. The sand layer need notbe screeded. Rough levelling is all that isrequired.

19. Soaking, Disinfecting and AirScouring the Media

After all the careful work relaying thefilter bed, the last thing you want to do isdisrupt the bed. Therefore, take extremecare when introducing water back into thefilter cell. Slowly and carefully introducethe water into the filter via the backwash

laterals. Where possible, throttle thebackwash pump so that it is operating asslowly as possible. Allow the water to slowlypercolate to the upper surface of the mediaand continue to fill the filter to the levelthat it usually drains down to prior tobackwashing.

As the filter fills, add sodiumhypochlorite solution to disinfect the filter.The sand will initially exhibit a highchlorine demand, so adding roughly half toone 25L carboy of hypo will service mostfilter sizes. A chlorine residual of 1 mg/L isusually targeted and an initial chlorine doseof 5 to 10 mg/l is usually required toachieve this.

To thoroughly mix in the hypo, carefullyair scour the filter. As with the introductionof water, the initial introduction of the airmust be as gentle as possible. Throttle theair blower and run the air into the filter assoftly as possible. Once the air scourpattern has stabilised, the air scour rate can

Figure 4. Relaying the first gravel layer.

Figure 5. Roughly levelling sand layer.


slowly be increased to normal operationallevels, then turn off the air and leave thefilter to soak overnight if possible.

20. Backwashing Away the Sand FinesAfter allowing the filter to soak, repeat

the air scour routine mentioned above. Atthe end of the air scour period, gentlyintroduce backwash water to the filter. Asthe backwash progresses, you may slowlyincrease the backwash rate to normaloperational levels. Backwash the filter for aslong a time a possible to remove as manysand fines as possible. This may require youto drain down your wastewater storageprior to the commencement of thebackwash.

21. Scraping Away any Remaining SandFines

When the backwash is complete, allowthe filter to drain down. Taking intoconsideration any Confined Space Entryrequirements, if safe to do so, enter thefilter and scrape off the top fines layer,usually 15-25mm of sand.

22. Adding Filter CoalAdding filter coal is messy if the coal is

not well washed. Fine black dust will coateverything that it settles on. Make sure thatyou are wearing respiratory protectionwhen adding the coal, and wear darkcoloured protective clothing or disposableoveralls (any light coloured clothing will getwrecked). As with the sand layer, onlyrough levelling is required as the anthracitewill self level during backwashing. Once theanthracite has been added, refill the filterusing the backwash system to the levelwhere the water usually drains down towhen backwashing. Let the anthracite soakfor a few hours.

23. Backwash the Filter AgainBackwash the filter again for as long as

possible to remove any anthracite fines.Once again, this may require you to draindown your wastewater storage prior to thecommencement of the backwash. Surfacescraping of fines may also be required.

Recommissioning the Filter

24. Putting the Filter Back Into ServiceDespite the extended backwashing that

the filter has already undergone, it isunlikely to produce top quality water rightaway as it needs to be “seeded” with floc to“ripen”. Where possible, filter to wasteuntil the filter outlet turbidity returns toacceptable operational levels.

25. Continue to Actively Monitor theFilter’s Health

To ensure that the filter does not needany major maintenance for many years,

make sure that the backwash is regularlyobserved and make notes of any changes tothe backwash or air scour pattern. Makeadjustments to the air scour rate and / ortime, and the backwash rate and / or timeas necessary to ensure that the filter is keptclean. Keep accurate records of thechemical dosing regime, clean bed headloss(headloss at the start of a run afterbackwashing) and headloss accumulationrate and regularly inspect the filter to checkfor mudball formation and any other signsof poor health. Adjust the filter run time ifnecessary. Do everything in your power toprotect the integrity of the filter bed andprevent any harm coming to the filter bed.Even though the filter can now be classifiedas “new” make sure it is included in aregular and rigorous filter inspection and

monitoring program. This will ensure thatit provides reliable service for many years tocome.

AcknowledgementsThe author wishes to thank Bruce

Murray of City Water Technology forcritically reviewing this manuscript.

The AuthorMichelle Colwell ([email protected]) is a Water TreatmentTechnologist at Gippsland Water. She canbe contacted on 0427 353 633.

ReferencesKawamura, S. “Integrated Design of

Water Treatment Facilities,” John Wileyand Sons, New York, 1991.


BRAIN TEASER - WATER1. A streaming current detector is usedto measure:a. How fast water flows

b. The size and number of particles inwater

c. The neutralisation of charge in waterafter the addition of coagulant

d. The ionic strength of the water todetermine the TDS

2. Which of the following tests is usedto determine the total bacterialpopulation in water?a. Total coliforms

b. Heterotrophic plate count

c. Presence absence test

d. Zeta potential

3. True colour in water is due to:a. Suspended matter such as iron andmanganese precipitates

b. Natural organic matter

c. DOC

4. The nephelometric method is used tomeasure:a. Suspended solids

b. Lead and copper

c. Alkalinity

d. Turbidity.

5. The target for filter performance is aturbidity of: a. <0.3 NTU

b. <0.1 NTU

c. < 1.0 NTU

d. <0.5 NTU

6. Particle counters in the waterindustry commonly measure particles inwater in the size range:a. 0 to 5 micronb. 10 to 15 micronc. 2 to 15 micrond. 15 to 20 micron

7. UV absorbance at 254nm iscommonly used as a simple measurefor:a. NOMb. DOCc. SUVAd. NTU

8. Which of the following is not afactor in determining the LangelierSaturation Index?a. pHb. CaCo3

c. Temperatured. Salinity.

9. A common disinfectant isa. Hydrochloric acidb. Fluoridec. Sodium Hydroxided. Sodium Hypochlorite.

10. A chemical storage tank holds25000L when full. Its level at 9am onMonday is 63%. By 9am Friday, itslevel has fallen to 47%. Assuming thatthe rate of chemical consumptionremains the same, what is the earliestday of the following week that youcould request a delivery of 15000L? a. Mondayb. Tuesdayc. Wednesdayd. Friday


Cynthia’s WIOA WrapThe Water Industry Operators Association

(WIOA) held the Annual General Meetingand Victorian weekend seminar at Ballarat inMarch. Around 40 operators and tradiesattended to share ideas, network and visitCentral Highland Water’s Ballarat SouthWastewater Treatment Plant.

One of WIOA’s newest corporatesupporters, CDS Technologies has justcompleted further trials under the VictorianState Government’s Smart Water grantsprogram, demonstrating their ability to minesewage and produce Class A re-use effluentin a timely and cost-competitive manner -0.5ML/D maximum in under 8 minutes @under $60/KL.

A group of keen Tasmanian operatorsarranged a meeting recently with WIOA todiscuss the options available for them toprovide services to operators in their State.Later this month, WIOA will also bemeeting with a number of interested peoplein Brisbane to discuss ways to best serviceoperators in Queensland as well. We’ll keepyou updated on the outcomes of theseimportant initiatives in future editions ofWaterWorks.

The prolonged drought in the WimmeraMallee has seen Grampians Water select ITT

Flygt to supply in a short time frame, twoRO plants to augment water supplies inHopetoun and Rainbow. Commissioningwill commence in June. Any enquiries callEddy Ostarcevic at Grampians Water.

WIOA has recently introduced an awardwhich recognises the outstanding services ofindividuals to the Association. The firstmembers to be inducted as Delegates of theInextricably Obstructed Tap Society(I.D.I.O.T.S) are Ron Bergmeier, RichardGreenhough, Tony Hourigan, Barry Waddelland George Wall. Congratulations to you all.

Operators on the Move• Mt Hotham Resort Management BoardsDick Shaw has left to pursue a new lifestylein Paynesville. He will still be active inWIOA activities and is looking for a job - ifanyone can help please contact WIOA. • Noel Stewart has left Danfoss and joinedHoneywell.• Glenn McKinnis of Grampians Water andDavid Blanch of Melbourne Water retiredearlier this year. We wish Glenn and Davidall the best in their new endeavours.• Glenelg Water staff have moved back intotheir newly renovated offices in the mainroad of Hamilton.

• Nick Bray has left WSL Consultants after10 years and has joined Goulburn ValleyWater as Works Co-ordinator, WaterTreatment based in Seymour.• Sean McKinney joins CDS Technologiesfrom Ondeo Nalco Australia as part of theSouthern Region sales team. After 16 yearsin the air-conditioning industry, Sean’smove is a gutsy one, but consistent with hisinterest in environmental issues relating towater. • Mary-Jane Crosbie previously of SelbyBiolab and Amcor has started her owncompany, Leatherback Environment,specialising in ISO14001 EnvironmentalManagement Systems - contact her [email protected].

Coming Operator Focused EventsJuly 26 - 30, Queensland Operatorsconference at Hervey BaySeptember 1 & 2, WIOA 67th Annualconference in WodongaSeptember 21 & 22, NSW Operatorsconference at Penrith Panthers

Contributions to this column can beemailed to Cynthia Lim at [email protected] or call her on 0409 403 237.

I N B R I E F

Water Quality and Distribution Systems SeminarAnthony Evans, Seminar Chairperson

The WIOA recently staged a seminaraimed specifically at distribution systemoperators dealing with issues relating to theoperation or maintenance of the waterreticulation network. The seminar wasconvened in response to demand fromWIOA Members, as well as by a needidentified through discussions with variouswater system managers. The event was heldin Rockbank, not far from Melbourne, andwas attended by 140 operators. We extendour thanks to Western Water for helpingwith the organisation of the day.

After extensive consultation, a programthat was relevant and targeted specifically atthe distribution system operators wasarranged. The presenters were chosencarefully to ensure that we had skilled andknowledgeable people sharing theirexperiences with us. The presentations werepitched at a hands-on level and importantly,the intent of this seminar was to providesome ideas about what can be done and thewhen, where and how of doing it. Thespeakers included:• Peter Mosse - (Gippsland Water) talkedabout the new environment for drinking

water quality management, ADWG, HACCPand how to monitor systems to improve waterquality and therefore service delivery to thecustomers. He also spoke about solvingproblems using dirty water and odourcomplaint case studies as examples. • Jill Busch - (Gippsland Water) spokeabout the importance of disinfection for theeffective control of pathogens along withsome specific practical examples.• Neil Healey - (Goulburn Valley Water)talked about managing work teams wherethere is a cross over of duties between waterand wastewater functions.• John Hearn - (South West Water) spokeabout the role of the operator in keeping thedistribution system running well and showedus a very important tool - a white bucket tocheck water colour.• Anthony Ohlsen - (Central HighlandsWater) spoke about an odour case study andemphasised how subjective this issue can be.He also gave us an opportunity to experiencesome ‘watery smells’ first hand.• Malcolm Hill & Andrew Forster-Knight- (South East Water) spoke about flushing

mains and showed us a predictive model theyare working on to allow flushing to be bettertargeted for optimum results.• Greg Creek - (EPA Victoria) gave us someinfo on what we should or shouldn’t do withthe water flushed out after cleaning anddistribution system repairs.• Last but not least Melinda Bawden - (WSLConsultants) spoke about sampling and gaveus important information on the do’s anddon’ts of sampling.

Overall the day was a resounding successand the interactive workshop session at theend of the day provided us with a few ideasto investigate and possibly include in futureseminars. The overall view was that weshould run this event again to cater for thoseoperators not able to attend this time. Thereis also a possibility of staging a similar eventin other States so if you are interested,contact the WIOA Secretary Mr GeorgeWall at [email protected] and he’ll get intouch with you.Anthony Evans ([email protected]) is anoperator employed by South West Water inWarrnambool.


ANSWERS TO WATER TREATMENT BRAIN TEASER (from December 2002 WaterWorks)

Q1. Optimum Alum dose rate (ppm/v) = 3.5mLs of 1% jar test solution X 10 = 35 ppm/v

Q2. Current Alum dose rate (ppm/v) = mLs/min X 16.67 = 20 X 16.67 = 30.3 ppm/vL/sec 11

Q3. Alum feed rate (mLs/min) = ppm/v X Plant flow rate (L/s) = 35 X 11 = 23 mLs/min16.67 16.67

Q4. The optimum Alum dose rate would remain the same as in question one regardless of the flow.

Q5. Alum feed rate (mLs/min) = ppm/v X Plant flow rate (L/s) = 35 X 22 = 46 mLs/min16.67 16.67

Q6. Possible options could be the use of polymers or alternative coagulants. If sufficient treated water capacity shut down the plantuntil raw water quality improves. Use alternative raw water supply if available. As you can see above there are many alternative solutions, and they will vary from plant to plant. It also highlights the importance ofhaving strategies in place to respond to changing conditions. This will include maintaining records of how these events were handled in the past eg. Dose rates, changes in plant set up, raw watersupply quality etc.

I N B R I E F

Watery TalesKristine Hunter

Ken Turner’s brilliant article aboutBleaching Customers in December 2002WaterWorks (been there done that - couldreally relate!) has prompted me to pass onsome “tales” of my own that may be ofinterest to operators.

Anyway, I’ve been at East GippslandWater for 3 years now as their Water QualityOfficer. When I started the monitoringprogram was fairly basic but met regulatoryrequirements. Since then I have expandedthe monitoring program much to the dismayof the operators here who claim I havetripled their workload!

Part of my job was to ensure that staff hadadequate training and understanding of thehow, why and when of taking water samples.Some of the classics I have encountered havebeen part of the training sessions. Writing aStandard Operating Procedure/WorksInstruction for taking a water sample, Iincluded the instruction on flaming tapsonly to have to rewrite it after an irate phonecall to include “flame taps after removingplastic tap fittings”(!)

Sampling during total fire ban days alsopresented a problem from the tap flamingpoint of view! I went to the local CFA andexplained what we did but they still insistedthat we would need a permit and a tanker ofwater on standby! Fuming at bureaucraticstubbornness and the lack of common senseexhibited by Government Authorities, I wentout sampling with staff not long afterwardsand watched while someone actually set fireto a tap! Needless to say we don’t sample ontotal fire ban days anymore! I was also forcedto rethink the flaming issue at Dinner Plainwhere it was kindly pointed out to me (in

words of two syllables or less) that there wereno garden taps in the Village and flaming afire hydrant (our sample sites) would not beeasy! Sample sites also had to be relocated asflaming the tap next to the petrol bowser atthe local servo was out! When it came totrying to explain how to take a ‘clean’ sample(ie. you and any appendage do not becomepart of the sample) I was impressed by thelateral thinking of placing a handkerchief(clean of course!) over the tap to filter outany impurities and thus get a ‘clean’ sample.

In 2001 I conducted an audit of all of oursampling sites by sending out a spreadsheetto the operators and asking them to checkthe site against some criteria: easily accessibleby staff, no fence, no dog, on the same sideof the road as the mains, occupied site (ie.water usage) etc etc. I received the checklistback from Omeo with ticks and crosses nextto sites. When I went up there to do somesampling I was surprised at one of the sitesthat met all criteria, especially, as theoperator pointed out, the ‘occupied site’criteria - we were sampling at the localcemetery! The Works Supervisor pointed outthat we had never had any complaints fromthe occupants regarding access or waterquality!

In terms of customer queries regardingwater quality I have had some doozies!! Onegentlemen kept me on the phone for nearlyan hour whilst he expounded on politician’ssuperannuation perks, the lack of support fornormal pensioners, how hard it was to getmail order brides these days (!?!), the usualgripes and grumbles about politicians andsnouts in troughs etc etc only to finally getaround to his water quality query - why were

we spending $30 million on increasing theflow down the Snowy River when it onlyruns out to sea!! Another was how do leadlevels affect ornamental carp - apparently thedam at the bottom of the garden held prizedcarp but also ducks and husband and sonwere fond of duck shooting but the missuswas worried about the lead shot in the water!

Various complaints about substances weadd to consumer’s water that has causedproblems - fluoride stains school trousers asone irate customer was informed by the localchemist, only to find out that we do notfluoridate any of our water supplies in whichcase the problem was still ours because herkids were costing her a fortune at the dentist!Requests for water to be tested for ‘stuff’. I’msure everyone would have similar tales! Oneof the best I’ve had was when I was with theState Water Laboratory (going back a whilenow!!) and I had a query as to what waterquality was suitable for consumption byemus (budding emu farmer!). This wasbeyond my area of expertise so I directedhim to the Healesville Sanctuary (AustralianNative Wildlife Park). When I got homethat night my husband, a zookeeper atHealesville Sanctuary, couldn’t wait to tellme about some nutter that called in wantingto know about water quality for emuconsumption! I just nodded and smiled -about all you can do under mostcircumstances!

The AuthorKristine Hunter ([email protected].

gov.au) is the Water Quality Officer withEast Gippsland Water.

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