Author: Prasanthi Hagare
Source: The Conversation
Date: 30 May, 2012
Our conventional water supply system that continually captures and delivers water is under great strain because of an increase in population, rapid urbanisation, and drastic changes in climate and rainfall. When the reliance on a continuous supply of water directly to our taps is in jeopardy, we then start to realise that we cannot take the supply of water for granted.
The question that has risen recently is whether Australians are ready to accept drinking recycled water. Before we answer the question, let us look at what is it we are drinking currently.
What are we drinking now?
The majority of Australians are drinking rain water that falls on the land, is collected in dams, transported to reservoirs, is then treated to remove solids and kill pathogens, and is finally distributed to the wider community via networks of pipes (also called reticulated supply). Water fit for drinking is called “potable” water, and the quality of water supplied is governed by Australian Drinking Water Guidelines, that are in line with WHO’s drinking water quality guidelines.
Australia relies on rainfall for most of its water supply. Issues arise when there is a prolonged drought, or, as in Western Australia, when the rainfall seems to steadily decrease – thus reducing the amount of water collected in dams. Solutions such as recycling wastewater for industrial purposes while continuing to use rainwater for potable purpose are useful. In Sydney, during the recent drought season, the then-State Government chose to respond to the “crisis” by building a desalination plant.
Recycled water for non-potable use
Most urban areas in Australia are reticulated, and receive water directly to the point of use. Likewise, most urban areas are sewered, with wastewater from houses, commercial units, restaurants and industry being directly discharged into sewers. Often, a proportion of stormwater also finds its way into sewers. This wastewater, often called sewage (as opposed to “domestic wastewater” which is from households) is transported to sewage treatment plants (STP) where it is treated to different levels of water quality depending on the location of the STP and the point of discharge. The treated wastewater is often referred to as effluent.
Technology to use recycled water for non-potable use such as in industry, and also for domestic outdoors activities, such as gardening is well-established in Australia. Water considered for recycling is sourced from STPs that have a full treatment scheme to remove most pollutants, and the scheme includes disinfection.
Indirect potable reuse
Indirect reuse of recycled water for potable purposes already happens in some parts of Australia. For example, Penrith discharges treated wastewater into the Nepean River, while this water is then used by North Richmond water treatment plant to treat and deliver it to the community in the Hawkesbury region.
In Australia, as most cities and rural towns are sewered, there is an option available to treat wastewater to a quality that is accepted for non-potable reuse. This already happens in Rouse Hill in northwest Sydney where treated water is recycled back to households through a dual-reticulated system.
Sewage can contain substances such as heavy metals, organochlorines (such as pesticides and pharmaceuticals), viruses, and protozoa. The recent 2011 Australian Drinking Water Quality guidelines do take into account the presence of the above substances, as the augmentation of water supply by municipal wastewater (effluent) is recognised as an option, and have set limits on these substances.