Environment

How to treat watershed water so it is safe to drink

Credit: Unsplash/CC0 Public Domain

Most of us are lucky to have clean, safe, high-quality water when we turn on the tap.

But a Senate inquiry into the presence of PFAS, or “forever chemicals,” has put drinking water safety back in the spotlight.

Independent senator Lydia Thorpe, who is leading the investigation, said elders in the Aboriginal community of Wreck Bay, New South Wales, were concerned about the health effects of PFAS in drinking water and said they had “removed bottled products from aged care packages. We’re buying water,” he said.

So how is water considered safe to drink in Australia? And why does water quality vary by region?

Describe what happens between the watershed and the faucet.

Human intervention in the water cycle

There is no “new” water on Earth. The water we drink is up to 4.5 billion years old and continually recycled through the water cycle. This causes water to move from the ground into the atmosphere through evaporation and back again (for example, through rain).

Humans interfere with this natural cycle by capturing and reusing water from various sources. A lot of things can happen before it reaches your home.

The quality of water when you turn on your tap depends on a variety of factors, including the local geology, what activities are occurring in the watershed, and the various processes used to treat the water.

How do we know what is safe?

The Australian Drinking Water Guidelines define what is considered safe, high-quality drinking water.

The guidelines establish acceptable water quality values ​​for more than 250 physical, chemical, and bacterial contaminants. They take into account not only aesthetics such as water taste and color, but also the potential lifelong health effects of drinking pollutants.

Although the guidelines are not mandatory, they provide a basis for determining whether the quality of water supplied to consumers across Australia is safe to drink. The guidelines are being revised gradually to ensure they reflect the latest scientific evidence.

From catchment area to water supply

Australians’ drinking water primarily comes from natural catchments. Sources include surface water, groundwater, and seawater (through desalination).

Public access to these areas is usually restricted to maintain optimal water quality.

Water filtration and purification occurs naturally as it passes through soil, sediment, rocks, and vegetation in a watershed.

However, water in the catchment is subject to further treatment through standard processes that typically focus on:

Removal of particulates (such as soil and sediment) Filtration (removal of particulates and their contaminants) Disinfection (such as the use of chlorine and chloramines to kill bacteria and viruses) Addition of fluoride to prevent cavities Water and chemical Adjust pH to help balance filtration.

This water is delivered to your taps through a reticulated system, which is a network of underground reservoirs, pipes, pumps, and fittings.

In areas without reticulated systems, drinking water can also be supplied from rainwater tanks. This means that the quality of your drinking water may change.

Sources of contamination can come from roof catchments that feed rainwater tanks and faucets due to lead in plumbing fittings and materials.

So does all water meet these standards?

Some rural and remote areas, especially indigenous communities, rely on low-quality surface and groundwater for drinking water.

Rural and regional waters can exceed recommended guidelines for salinity, microbial contaminants, and trace elements such as lead, manganese, and arsenic.

The federal government and other agencies are trying to address this problem.

Deteriorating local water quality has many effects. These include the impact on increased rates of tooth decay in Indigenous peoples; This happens when obtaining sweet, cold drinks is cheaper and easier to obtain than accessing good quality water.

What about PFAS?

There are also new concerns about the presence of PFAS, or “forever” chemicals, in drinking water.

Recent studies examining the toxicity of PFAS chemicals and their presence in some drinking water catchments in Australia and overseas have led to recent assessments of water source contamination.

A review by the National Health and Medical Research Council (NHMRC) proposed lowering limits for four PFAS chemicals (PFOA, PFOS, PFHxS, and PFBS) in drinking water.

The review used publicly available data and found that most drinking water supplies are currently below the new guideline values ​​proposed for PFAS.

However, PFAS “hotspots” remain where drinking water catchments or other water sources (such as groundwater) are affected by activities where PFAS are used in industrial applications. Additionally, some communities have expressed concern about rising levels of PFAS in their communities and links to cancer clusters.

Although some PFAS are known to be carcinogenic, it is not clear whether PFAS cause cancer. Links are still under discussion.

Importantly, assessments of exposure levels from all sources within the population show that PFAS levels are decreasing, meaning that the risk of exposure is also decreasing over time. .

What about removing PFAS from water?

Most drinking water sources are not associated with industrial contaminants like PFAS. As such, water sources typically do not undergo expensive treatment processes such as reverse osmosis, which can remove most waterborne contaminants, including PFAS. These treatments are energy-intensive and expensive and are not required based on recent water quality assessments by NHMRC.

Pollutants are present everywhere, but it is the dose that creates the toxicity. Very low concentrations of chemicals, including PFAS, are undesirable but may not be harmful, and complete removal is not guaranteed.

Presented by The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.conversation

Citation: How to treat watershed water to make it safe to drink (January 26, 2025) from https://phys.org/news/2025-01-catchment-safe.html 2025 1 Retrieved on March 26th

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