STO RM\A'\TE R TREATME NT\VITH BENEFITS

7Tlhere has been a strong debate in

I th* lurt lew years regarding thecontroversial issue of using treated sewage

or stormlvater for drinking. The SouthAustralia Government in late 2010 putS1 million into a study of stormwaterrec.vcling r'vith the prospect of using it fordrinking water across the state, and earlierthat year Australian Water AssociationCEO Tom Mollenkopf suggested

Australians needed to become more open-minded about drinking recycled water.

Willoughby Ciq' Council in Sydneyhas just finished an ambitious stormwaterproject, which also involves stormwater

treatment and reuse but interestingly enough

not for drinking as this was not the most

economically viable option. The end result

though, is stil1 saving considerable amounts

of potable wate1, the council claims.

But to start at the beginnipg, for manyyears Willoughby City Council had been

troubled by persistent flooding problems,

especially in the Chatswood CBD. Whenthe loca1 civic centre, The Concourse,was to be redeveloped, the council cameup with the idea of building a significantstormwater retention tank to slow downthe flow of water in the area to minimiseflooding. The project soon turned intothe Chatswood Integrated StormwaterManagement Scheme, when the councildiscovered its potential for solving several

water related issues.

"Once you put that much water intoa tank, it seems ridiculous not to look atopportunities to reuse it," Willoughbydirector of infrastructure services Steven

Head said. "So over a period of time wecame up with this concept of a totalintegrated water treatment process."

Stormwater for air conditioningThe integrated process consists of fourphases: collection, treatment, storage and

reuse. The system collects stormwater ina 16-20 hectares area in the northern partof Chatswood CBD by capturing waterrunning through gutters or down drains.

The water is led through gross pollutant

36 MAY 2012 : wME magazine

*Willoughby City Council had been troubled by persistent flooding problems, especrally in the Chatswood CBD,

traps and then diverted into a 5 megalitrestorage tank for treatment and monitoring.

In case of larger storm events, a weatherwarning system will automatically emptythe tanks in advance to free up capacity.

One of the advantages of the treatmenttrain is the relatively cheap filtrationprocess. By only using activated carbon

filters, a BIRM catalytic fi1ter trappingmetal compounds and a few othertechnologies, the system avoids the morecostly and carbon intensive high-endmembrane filtration technologies.

We see this as being thefirst step in a councilvision to establish a

non-potable water ringthroughout the majorwater users within theChatswood 0BD

- Steven Head, Willoughby Counci

"With the treatment train we're tryingto get water to a point where the qualityis so it can be used at a lower energy costthan potable water," Head said.

\A4rile the recycled stormwater doesn't

have the quality for drinking, it stil1 reduces

the demand for potable water It is currendybeirtg used for irrigation, flushing toilets and,

most remarkably, for the air-conditioningcooling towers at The Concourse.

"To our knowledge it's one of the firs'ttimes stormwater from a healry developedurban catchment is ever used for this

[cooling towers] purpose," Head said.

Since cooling towers are one of the mostsignificant users of water in commercialbuildings, of which the Chatswood CBDhas many, a large volume of water can beconserved over a year, Head claims.

Cash in the ring of waterAt the moment the system only providesThe Concourse facility with recycledstormwater but in time the council hopesto also provide other businesses with lou,-cost treated water.

"We see this as being the first step in a

council vision to establish a non-potablewater ring throughout the major waterusers t'ithin the Chatswood CBD," Headsaid."lt's a system that hasn't been used,

lvel1 virtually any'where in this country atall, but r'r-e think it has great applicabilityacross CBDs."

\44rether the stormwater system will beable to cope rvith big stormwater eventsstil1 remains untested. But according toHead, there har-en't been any reports ofeven slight nuisance from water in the sixmonths the svstem has been operating.

Elen thoush the system won'tcompleteh' eliminate the risk of flooding,it does provrde other benefits fromthe point of r-ieu of sustainability andeconomics. rndrd