Greywater treatment and technology
As the international community grapples with the problem of diminishing water supplies, greywater reuse has emerged as a promising long-term water recycling option that limits demand for fresh water.
Technologies exist to treat domestic greywater chemically, biologically and physically, rendering it safe for applications such as irrigation and toilet flushing.
Regulating the new greywater environment is proving a challenge the world over, but a new Australian protocol that measures the capabilities of greywater treatment technologies against a uniform set of criteria is set to lead the way.
Greywater treatment technologies have proved most popular in regions where water is scarce or the population dense.
In Tokyo, Japan, greywater recycling is mandatory for buildings with an area greater than 30,000m² or with a potential non-potable demand of more than 100m³ per day.
In Cyprus, the use of greywater for garden irrigation and toilet flushing has been subsidised to the tune of AU$2,878 per dwelling.
In the United States there are no national guidelines for the regulation of water use and plumbing. Instead, individual States are responsible for governance.
California was the first State to permit the reuse of greywater, and the three-tiered system employed in Arizona is widely regarded as one of the most progressive.
Under Arizona regulations, systems producing less than 1,515L a day must meet a list of best management practices and are covered by a general permit.
Systems processing from 11,355L a day require their own permit, and those generating more than that are subject to case-by-case assessment.
Greywater recycling is not widespread in the United Kingdom, and specific legislation regulating greywater use does not yet exist.
As treatment and reuse technologies are still in their infancy, many countries suffer from a lack of consistent regulation, making life difficult for manufacturers and consumers.
The situation in Australia, the driest inhabited continent, illustrates these difficulties well.
The southern regions of Australia receive limited rainfall, and the potential that greywater offers to supplement dwindling supplies of fresh water is being investigated.
However, there is no Australian Standard to which greywater treatment technologies are tested and regulated; States and territories each have their own legislation for greywater collection, treatment and use.
For example, in New South Wales, greywater treatment technologies require approval from the relevant local government authority for installation and operation.
In Western Australia, it is an offence to begin construction without approval, and a system cannot be used until it passes a local government inspection.
In Victoria, consumers must contact their local council and lodge an application.
And in Canberra, residents do not need council permission; instead they are required to have a plumbing inspection after the installation is complete.
The requirements for the technologies themselves vary considerably, from stringent viral and bacterial testing to limited regulation for the direct use of untreated greywater at a domestic level.
The legislation covering greywater reuse also differs from State to State. In Queensland it is covered by the Plumbing Act, in NSW by the Local Government Act, and in Victoria by the Environment Protection Act.
It is becoming a bureaucratic nightmare for manufacturers and consumers.
The Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia’s national science agency, has set out to simplify the process by developing a protocol that it hopes will become an approved Standard for greywater testing technologies.
“We’re trying to develop a practical, robust, repeatable testing method for greywater treatment technologies to meet
Australian guidelines for recycled water,” CSIRO water technologies development chemist Melissa Toifl says.
“Technology manufacturers are frustrated because every time they try to market their product in a different State they have to go through the whole approval procedure again.
“We’re hoping this protocol will eventually form a national Standard that everyone works to, in order to make it easier for technology manufacturers and consumers to adopt the technology.”
The project, partly supported by the Smart Water Fund, is a joint initiative of Melbourne’s water businesses and the Victorian Government, and the CSIRO Water for a Healthy Country Flagship. It began with the development of ‘synthetic’ greywater.
“We needed something that was consistent so the background for testing wasn’t altered and all variables were controlled,” Melissa says.
“It was also important that it mimicked real greywater.
“The synthetic greywater that was developed contains basic everyday products that people use in the bathroom and laundry – soap, toothpaste, washing powder and other personal care products.”
This formulation allows for controlled testing of greywater treatment technologies and provides a baseline for performance comparison.
Several greywater treatment technologies were obtained, from which the protocol was developed. Testing began with a traces study that outlined exactly how each technology works. Chemical analysis then established the basic working order.
“We do the chemical testing to ensure the technology removes the normal chemicals that are present in greywater –nitrogen, phosphorus, suspended solids, etc,” Melissa says.
“Once its performance in this area is satisfactory we assume it is working correctly.
“The greywater testing technologies are then subjected to a series of challenge-based tests. In a normal situation it would get a certain number of micro-organisms – including bacteria and viruses – coming through steadily day by day.
“What we do is hit the system with a really high dose of micro-organisms and pathogens and see if it can remove those – and that’s basically what the protocol entails.”
In essence, the protocol will measure whether a greywater treatment technology, in a challenged situation, can meet Australian guidelines for recycled water.
“The protocol won’t bring water to that standard; it will test whether it is at that standard.”
But will it encourage manufacturers to produce better-quality technologies?
“That is a tricky one. Theoretically all technologies would be aiming to provide a high quality of water. However, the greywater testing protocol or a national Standard may find that some systems aren’t able to cope with shock doses of micro-organisms – which might mean a tiered system will result.”
The protocol is the first of its kind in Australia, and Melissa expects it will lead the way for a national approach to testing and regulating greywater treatment technologies.
In September, CSIRO was invited to present its findings at the International Water Association World Water Congress in Vienna, Austria.
“There has been significant interest nationally and internationally in applying the outcomes of this project, so presenting the research to an international audience was invaluable,” Melissa says.
“We hope it may even become an internationally recognised and used protocol.”