Wastewater: an increasingly valuable commodity

The Illawarra Wastewater Reclamation Plant is one of the largest reuse facilities in Australia, recycling at its peak treatment capacity 320 ML/day.

Down the drain is no place for this valuable resource. Wastewater reuse is the way of the future, writes the business development team at Veolia Water Systems.

The water crisis in Australia has become part of day-to-day reality. Recycling wastewater for industrial and agricultural use is becoming of key importance to Australia, the driest inhabited continent on Earth, as it offers a drought-proof source of water.

Wastewater reuse can reduce manufacturing costs for industry. As an alternative water resource for non-potable applications or potable displacement it can be the most cost-effective source compared to further augmenting potable supplies. Valuable potable water is then kept for drinking purposes.

Existing water resources in Australia are facing increasing pressure, due to a range of both supply-side and demand-side factors. The reduction in rainfall and runoff because of ongoing drought and climate change across broad areas of Australia has led to chronic water shortages. Add to this the increasing population in urban areas – and in particular, the coastal tourist destinations – and demand is overtaking limited supplies of water in these areas.

Legislation and standards in Australia make it compulsory for many states to reach a minimum usage of 20 per cent reuse water by 2012. This constitutes a driving force for both industries and municipalities to seriously investigate water reuse and recycling. In addition, local communities, who are increasingly informed about challenges and technologies available to sort out the water crisis, no longer accept the drought as an excuse.

Also, the increased demand for Class A effluent from wastewater treatment plants corresponds to the idea that discharge into sensitive environments should be carefully monitored and controlled, which also translates into increasing discharge compliance costs.

Water and energy costs are a key driver as potable water prices increase. Just as important as cost, is the security of supply and guarantee of having access to water supplies at a known price.

Environmental factors too play a part, with greater understanding of the need to provide environmental flows, to reduce nutrient discharge to surface waters and to limit abstraction of groundwater where it leads to seawater ingress into aquifers.

The technologies
Wastewater’s role in Australia’s mid- and long-term strategies to find sustainable solutions is crucial. The improvements in technologies for wastewater and drinking water treatment are meeting a range of new and emerging challenges from both microbial and chemical contaminants.

Innovative and advanced technologies for process water, recycling and wastewater treatment solutions represent significant savings in water and wastewater costs.

It is possible to produce high purity water that can be treated to suit any application at a price known in advance through the management of owned recycle schemes and unaffected by water restrictions.

A technology such as membrane bioreactor (MBR) technology, including Veolia Water Systems’ BIOSEP, provides a very efficient treatment in a small footprint facility, producing high quality reuse water (class A) from discharges with high BOD/COD levels.

Reverse osmosis (RO), another membrane process, is used extensively to remove dissolved contaminants from sewage, and salt from seawater or brackish water. It is a very efficient second stage barrier and TDS removal treatment for reuse.

Technologies such as Hydrotech discfilters and the Actiflo clarification process also represent efficient pre-treatment of wastewater for reuse or total treatment for surface water.

It is worth pointing out in the current political climate that such wastewater treatments are cheaper in terms of capital and operating costs than desalination of seawater by reverse osmosis.

The water hierarchy: reduce, reuse and recycle
The common catchphrase in most conservation practices of reduce, reuse, recycle is highly relevant when investigating wastewater reuse opportunities. Each has its place in the scheme of things.

Reducing demand is by far the most cost-effective method in conserving water. Demand-side steps undertaken by municipalities and water authorities have included water restrictions, consumer education and domestic retrofitting programs for low volume showerheads and cisterns.

Stepped pricing of potable water based on consumption also delivers a strong conservation message.

In the industrial sector, reducing demand can be a little more complex. Evaporative cooling is a large component of water consumption by industry but it cannot easily be reduced. In some instances water use efficiency in the cooling circuits can be improved, but large-scale water use reductions are difficult to achieve. Other strategies must be employed.

Reuse, in the domestic sense, includes capturing and storing rainwater and greywater for use in toilet flushing and on gardens. On a broader municipal front, providing a supply of highly treated wastewater and distributing this to new housing developments via a third pipe system will become an increasingly common feature of the urban landscape.

In the processing industries, water discarded by one stage of a manufacturing process may still be quite acceptable for use in another before being discharged from the site. A thorough knowledge of the particular contaminants introduced to the water during its use in the manufacturing environment must be developed and their potential impact on downstream processes known before reuse can be considered.

As evaporative cooling systems are commonly the largest single water sink on an industrial site, displacing potable water with a secondary water source from within the manufacturing process is usually the first consideration for water reuse.

Recycling should only be explored once all demand-side reduce and reuse strategies have been exhausted. Water recycling may involve stormwater harvesting and/or the return of highly treated wastewater to the potable supply either indirectly or directly. Indirect potable return may involve aquifer recharge or supplementing river flows upstream of a drink water supply reservoir.

Although employed in other countries since the 1970s, direct potable return has yet to gain broad acceptance in Australia. Its time must surely come soon.

More information from Karen Shaw, Veolia Water Systems business development manager, on (02) 8572 0496 or karen.shaw@veoliawater.com