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IntroductionEven though 99% of wastewater is water, it contains pathogens, nutrients, solids,chemicals and other hazardous substances, which is dangerous for both human and

environment. With proper treatment, the water will be environmentally friendly and notdangerous for human. In this case, civil engineering undergraduates of Queenslandniversity of !echnology have been given an opportunity to loo" inside one of themethods that can be used to treat wastewater by #oganholme wastewater treatmentplant $igure &'. !he results from this treatment are( the water is recycled and availableto be reused.

Figure 1 Loganholme Wastewater Treatment Plant (Image courtesy of LoganholmeWastewater Treatment Plant Blackboard Loganholme Site isit !ssessment" 

P!#T !#oganholme wastewater treatment plant treats wastewater from various locations. !hereare wastewaters from residential areas, commercial, industrial and o)ce combined withgroundwater. Wastewater itself is classi*ed to three classi*cations( domestic wastewater,industrial wastewater, and municipal wastewater. +omestic wastewater is usually comefrom residential areas. It contains feces, urine, grey water from "itchen drainage and

others. Industrial wastewater is more dangerous, because sometimes, the wastewaterfrom the industry is not clearly treated, leaving liuid chemical to the environment. #ast,municipal wastewater comes from o)ce, trade, hotels, restaurants and public areas.

 !here are - treatment stages in #oganholme wastewater treatment plant( pretreatment,primary, secondary, and tertiary levels of treatment. !he complete process /ow in thediagram is described in appendi0 1.

Pre$treatment !he *rst treatment process is pretreatment. It basically screen and *lter the wastewater.In this *rst step, the contaminants that usually *ltered are large ones. or e0ample(roc"s, plastics, clothes, etc. !hese large wastes could bloc" pumps, treatment channels,and damage the rest of the euipment parts. !he contaminants that *ltered will be

removed and dumped into the land*ll. 1nother ob2ective in this preliminary step is toavoid the formation of 345 and other no0ious gases. In result, 60ygen is supplied to the

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pipeline to remove the gas. In addition, o0ygen also will ensure the process to remainaerobic.

7asic screening euipment is used by #oganholme wastewater treatment plant. !hey areinlet wor"s, grit tan"s, wastewater screen, and grit conveyance system. !o improve itsscreening step, #oganholme wastewater treatment plant has a new inlet wor"s installed

in the plant. urther information about this will be provided in %art B&

Primary TreatmentIn this treatment stage, grit and silt conduct further screening process to removesuspended solids. 1fter that, the wastewater will /ow into settling tan"s or clari*erswhere sludge is settled and then, scum will form on top of it after several hours. 1fter thisstage, the /oated scum and settled materials are removed and the wastewater willcontinue to the secondary treatment. 8enerally, the primary treatment removes almost4 to : percent of 7iological 60ygen +emand $76+' and around : to ;: percent of thesuspended solids. $16 <orporate +ocument =epository, 4:&'. Eualization of thestrength of wastewater can be obtained through primary treatment process as well.

Secondary TreatmentIn this step, the sewage will be mi0 with bacteria and o0ygen. !he mi0ing process willremove dissolved and suspended biological matter even more. When o0ygen is suppliedto the process, the bacteria will digest the pollutant faster. !he organic solids areconverted into coagulated suspended mass that is heavier and bul"er. 5o in the end, itwill settle to the bottom of the tan". !he wastewater will then continue to /ow to thesedimentation tan", called a secondary clari*er.

5econdary treatment system is classi*ed as *0ed*lm or suspendedgrowth system. In#oganholme wastewater treatment plant, suspended growth system, which includesactivated sludge, is involved. It has four chambers of o0idation ditch and uses aerationspray to supply o0ygen to the water. !he water will come out from the o0idation ditchand go to the > clari*ers. nder ideal condition, denitri*cation occurs which convert

ammonia to nitrate ultimately to nitrogen gas. !he organic matter on a *lter will undergochange of character due to biological o0idation and nitri*cation.

 !he sludge from the clari*ers is transferred to the dewatering process, which is used toremove the remaining water from the sludge. #oganholme wastewater treatment plantuse the belt pres system where the sludge from the o0idation ditch and clari*ers areloaded onto the belt and press together to remove the water. !hen the wastewater will/ow to the tertiary treatment process.

Tertiary Treatment !ertiary treatment process will remove phosphorus and decrease the amount of 76+ aswell as the suspended solids loading. +isinfection comes ne0t after the removal, which isto reduce the microorganism that has the potential to be harmful to human health.

+uring this process, chlorine will be put into the tan" for disinfection. #oganholmewastewater treatment plant has > tan"s, which has the capacity of 94: "g in each tan".+uring chlorination, liuid of chlorine is converted into gas and used as disinfectant ofwastewater later on.

P!#T B

'ew Inlet Works !he new inlet wor"s is the *rst step of the waste treatment process at #oganholme W!!?. !he inlet wor"s structure aims to screen and remove the ma2ority of large waste particlesfrom the wastewater and can handle up to >>:: litres of wastewater per second.

 !he new inlet structure consists of four main components@• ine Aechanical 5creens

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• 8rit Borte0

• 8rit and =ag =emoval

• 6dour <ontrol

Fine echanical Screens

1s the wastewater enters the #oganholme W!!?Cs new inlet wor"s it is diverted to one offour pipes through one of the four *ne mechanical screens. !ypically two of these screensare on at a time to allow for maintenance, mechanical cleaning and less Dwear and tearCto occur on the two screens which are not in use at the time. !he screens at #oganholmeW!!? wor" for 4- hours at a time at appro0imately &;: litres of wastewater per secondeach but is capable of receiving and screening higher /ows when necessary. !he purposeof the screens is to not allow large solids to pass through that could potentially bloc"pumps, pipes or channels further in the treatment process.

)rit orte*ollowing the screening, the screened in/uent wastewater then enters the grit vorte0which purpose is the removal of grit $heavy particles' from the raw sewage. !he girtvorte0 wor"s by having the in/uent raw sewage enter tangentially into the upper

chamber of the vorte0, where mechanical agitators create a vorte0 eect which causesthe grit to collect in the centre of the chamber because of the in/uence of centrifugalforce where they then settle to the bottom of the grit tan" for removal, dewatering andfurther washing. !he wastewater then continues out of the grit tan" free of most grit andlarge solids for the ne0t treatment process.

)rit and #ag #emo+al !here are two bins which collect the solids received during the inlet wor"s process. !heblue bins collect the rag $solids removed by the screens' and the white bins collect thegrit $solids removed by the grit vorte0 tan"'. !hese solids are then transported by truc"osite to land*ll.

,dour -ontrol

+angerous foul gas in removed during the inlet wor"s process through pipes to the odourcontrol facility which uses odour treatment *lters to prevent dangerousFpoisonous gasesli"e hydrogen sulphide escaping into the outside air as well as ensuring that the#oganholme W!!? does not give o a foul odour to the surrounding area.

,*idation Tanks./itches !he o0idation tan"s are a process which biologically treats the raw sewage. !he o0idationtan" is set up in multiple channels and uses long retention times to removebiodegradable organic matter from the wastewater. Aicroorganisms referred to as DbugsCbrea" down the raw sewage in an attempt to purify the water. Aounted aerators providethe microorganisms with o0ygen which assist in microbial growth and achieving optimalwater velocity to ensure that the DbugsC bond to incoming wastewater. Gear to the startof the o0idation tan" process ammonia is added to the liuor to nitrify the wastewater for

the DbugsC to devour the debris as they consume the nitrate. !owards the end of theo0idation tan" process the eHuent is denitri*ed so it is able to be sent on to theclari*ers.

-lari0er !he clari*er uses gravity sedimentation to allow the sludge to settle to the bottom of theclari*er tan", meanwhile the clean water /ows over the edge of the tan"s to /ow on toreceive a dosage of chlorine to ad2ust the waterCs ?3 value before entering the contacttan"s. !he sludge when settled to the bottom of the tan" is collected via pump, screenedagain and returned to be bro"en down further in the o0idation ditches to minimise theproduction of sludge by the W!!?.

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Figure Loganholme Wastewater -lari0ers (Image -ourtesy of )oogle"

P!#T -

Loganholme WWTP Primary Sedimentation Tank -urrentSituation1t the present #oganholme Wastewater !reatment ?lantCs primary sedimentation tan" iscurrently used only as an over/ow tan" as it is not reuired in the sewage treatmentprocess anymore. !he primary reason for the tan" being unused as a sedimentation tan"is that the ma2ority of the large sewage waste particles are *ltered by the - meshscreens and grit vorte0 in the new inlet wor"s, eliminating the need for the primarysedimentation tan".

P!#T /oamFscum development usually occurs in the chlorination tan"s and o0idation ditches. Itis caused by e0cessive growth of *lamentous bacteria. ilamentous bacteria itself hassome characteristics $8ri)ths 5tratton, 4:&:'(

&. !he foaming organisms have a hydrophobic cell surface, meaning that the outercell wall is greasy. It is composed of mycolic acids. !hatCs why they tend to be

water repellent and want to /oat on the surface.4. !he foaming organisms are growing on the fats, oils, and greases as their surface

mimics them. 5o they tend to grow really fast because the condition is verysuitable for them.

 !here are lots of problem concerning this development( *rst, it can increase the weight of the solids carried by the secondary clari*er. 5econdly, the digesters may over/ow andclogging of gas systems including pressure and vacuum relief valves. 1nd possibly,severe foaming conditions may occur in certain conditions.

 !o handle the foaming problems, it is necessary to prevent the biological foams reach thesecondary clari*ers. !herefore, there are two possible devices $8ri)ths 5tratton, 4:&:'to stop the foams by providing an under/ow baHe on the outlet from the bioreactor tothe clari*ers.

 !he *rst one is developed by 1?E. !his device is able to collect, raise and discharge thescum because it is euipped with buc"ets similar to the surface s"immers on primary

sedimentation tan"s. !he second one is developed in 8ermany. It uses a inclined gravitydrainage dec" with a cloth belt to collect, raise and discharge the scum.

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 !he scum can later be dumped into land*ll.

Bibliogra%hy16 <orporate +ocument =epository. $4:&'. Wastewater Treatment . $G. =. +epartment,

?roducer' =etrieved &: &:, 4:&, from Wastewater !reatment and se in1griculture@ http@FFwww.fao.orgFdocrepFt:&eFt:&e:.htm8ri)ths, ?., 5tratton, 3. $4:&:, June 44 to 4-'. Foaming Organisms in Sewage

Treatment - Friend of Foe: Victim of Bad Publicity. =etrieved 6ctober &4, 4:&,from Water Industry 6perators 1ssociation of 1ustralia@http@FFwww.wioa.org.auFconferenceKpapersF&:KldFdocumentsFpetergri)ths.pdf 

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