14 billion litres of untreated wastewater is created each day in developing countries, but we don’t know where it all goes



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Jacqueline Thomas, University of Sydney

To limit the spread of disease and reduce environmental pollution, human waste (excreta) needs to be safely contained and effectively treated. Yet 4.2 billion people, more than half of the world’s population, lack access to safe sanitation.

In developing countries, each person produces, on average, six litres of toilet wastewater each day. Based on the number of people who don’t have access to safe sanitation, that equates to nearly 14 billion litres of untreated faecally contaminated wastewater created each day. That’s the same as 5,600 Olympic-sized swimming pools.

This untreated wastewater directly contributes to increased diarrhoeal diseases, such as cholera, typhoid fever and rotavirus. Diseases such as these are responsible for 297,000 deaths per year of children under five years old, or 800 children every day.

The highest rates of diarrhoea-attributable child deaths are experienced by the poorest communities in countries including Afghanistan, India, and the Democratic Republic of Congo.

Given the global scale of this problem, it’s surprising sanitation practitioners still don’t know where exactly all the human excreta flows or leaches to, due to absent or unreliable data.

Poor sanitation to worsen under climate change

Inadequate sanitation is not only a human health issue, it’s also bad for the environment. An estimated 80% of wastewater from developed and developing countries flows untreated into environments around the world.

If an excess of nutrients (such as nitrogen and phosphorous) are released into the environment from untreated wastewater, it can foul natural ecosystems and disrupt aquatic life.




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This is especially the case for coral reefs. Many of the worlds most diverse coral reefs are located in tropical developing countries.

And overwhelmingly, developing countries have very limited human excreta management, leading to large quantities of raw wastewater being released directly onto coral reefs. In countries with high populations such as Indonesia and the Philippines, this is particularly evident.

A coral reef underwater, with clown fish swimming by.
Sewage discharges in proximity to sensitive coral reefs, particularly in the tropics.
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The damage raw wastewater inflicts on corals is severe. Raw wastewater carries solids, endocrine disrupters (chemicals that interfere with hormones), inorganic nutrients, heavy metals and pathogens directly to corals. This stunts coral growth, causes more coral diseases and reduces their reproduction rates.

The challenges of climate change will exacerbate our sanitation crisis, as increased rain and flooding will inundate sanitation systems and cause them to overflow. Pacific Island nations are particularly vulnerable, because of the compounding impacts of rising sea levels and more frequent, extreme tropical cyclones.

Meanwhile, increased drought and severe water scarcity in other parts of the world will render some sanitation systems, such as sewer systems, inoperable. One example is the mismanagement of government-operated water supplies in Harare, Zimbabwe leading to the failure of the sewerage system and placing millions at risk of waterborne diseases.

Even in more developed countries like Australia, increased frequency of extreme weather events and disasters, including bushfires, will damage some sanitation infrastructure beyond repair.

Global targets to improve sanitation

Improving clean water and sanitation have clear global targets. Goal 6 of the United Nation’s sustainable development goals is to, by 2030, achieve adequate and equitable sanitation for all and to halve the proportion of untreated wastewater.

A man emptying a pit latrine in urban Tanzania
A man emptyies a pit latrine in urban Tanzania.
Jacqueline Thomas, Author provided

Achieving this target will be difficult, given there is an absence of reliable data on the exact numbers of sanitation systems that are safely managed or not, particularly in developing countries.

Individual studies in countries such as Tanzania provide small amounts of information on whether some sanitation systems are safely managed. But these studies are not yet at the size needed to extrapolate to national scales.




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So what’s behind this lack of data?

A big reason behind the missing data is the large range of sanitation systems and their complex classifications.

For example, in developing countries, most people are serviced by on-site sanitation such as septic tanks (a concrete tank) or pit latrines (hole dug into the ground). But a lack of adherence to construction standards in nearly all developing countries, means most septic tanks are not built to standard and do not safely contain or treat faecal sludge.

A hole in the ground, lined with two bricks, and a blue bucket beside it
A typical pit latrine in rural Tanzania.
Jacqueline Thomas, Author provided

A common example seen with septic tank construction is there are a lot of incentives to build “non-standard” septic tanks that are much cheaper. From my current research in rural Fiji, I’ve seen reduced tank sizes and the use of alternative materials (old plastic water tanks) to save space and money in material costs.

These don’t allow for adequate containment or treatment. Instead, excreta can leach freely into the surrounding environment.

A white pipe juts out of a blue plastic tank and into the ground.
A ‘non-standard’ septic tank, which uses plastic, in Fiji.
Jacqueline Thomas, Author provided

A standard septic tank is designed to be desludged periodically, where the settled solids at the bottom of the tanks are removed by large vacuum trucks and disposed of safely. So, having a non-standard septic tank is further incentivised as the lack of sealed chambers reduces the accumulation of sludge, delaying costly emptying fees.

Another key challenge with data collection is how to determine if the sanitation infrastructure if functioning correctly. Even if the original design was built to a quality standard, in many circumstances there are significant deficiencies in operational and maintenance activities that lead to the system not working properly.




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What’s more, terminology is a constant point of confusion. Households — when surveyed for UN’s Sustainable Development Goal data collection on sanitation — will say they do have a septic tank. But in reality, they’re unaware they have a non-standard septic tank functioning as a leach-pit, and not safely treating or containing their excreta.

Fixing the problem

Achieving the Sustainable Development Goal 6 requires nationally representative data sets. The following important questions must be answered, at national scales in developing countries:

  • for every toilet, where does the excreta go? Is it safely contained, treated on site, or transported for treatment?

  • if the excreta is not contained or treated properly after it leaves the toilet, then how far does it travel through the ground or waterways?

  • when excreta is removed from the pit or septic tank of a full on-site latrine, where is it taken? Is it dumped in the environment or safely treated?

  • are sewer systems intact and connected to functioning wastewater treatment plants that releases effluent (treated waste) of a safe quality?

Presently, the sanitation data collection tools the UN uses for its Sustainable Development Goals don’t answer in full these critical questions. More robust surveys and sampling programs need to be designed, along with resource allocation for government sanitation departments for a more thorough data collection strategy.

And importantly, we need a co-ordinated investment in sustainable sanitation solutions from all stakeholders, especially governments, international organisations and the private sector. This is essential to both protect the health of our own species and all other living things.




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The Conversation


Jacqueline Thomas, Lecturer in Environmental and Humanitarian Engineering, University of Sydney

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

Not just hot air: turning Sydney’s wastewater into green gas could be a climate boon



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Bernadette McCabe, University of Southern Queensland

Biomethane technology is no longer on the backburner in Australia after an announcement this week that gas from Sydney’s Malabar wastewater plant will be used to power up to 24,000 homes.

Biomethane, also known as renewable natural gas, is produced when bacteria break down organic material such as human waste.

The demonstration project is the first of its kind in Australia. But many may soon follow: New South Wales’ gas pipelines are reportedly close to more than 30,000 terajoules (TJs) of potential biogas, enough to supply 1.4 million homes.

Critics say the project will do little to dent Australia’s greenhouse emissions. But if deployed at scale, gas captured from wastewater can help decarbonise our gas grid and bolster energy supplies. The trial represents the chance to demonstrate an internationally proven technology on Australian soil.

pipeline at beach
The project would turn Sydney’s sewage into a renewable gas.
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What’s the project all about?

Biomethane is a clean form of biogas. Biogas is about 60% methane and 40% carbon dioxide (CO₂) and other contaminants. Turning biogas into biomethane requires technology that scrubs out the contaminants – a process called upgrading.

The resulting biomethane is 98% methane. While methane produces CO₂ when burned at the point of use, biomethane is considered “zero emissions” – it does not add to greenhouse gas emissions. This is because:

  • it captures methane produced from anaerobic digestion, in which microorganisms break down organic material. This methane would otherwise have been released to the atmosphere

  • it is used in place of fossil fuels, displacing those CO₂ emissions.

Biomethane can also produce negative emissions if the CO₂ produced from upgrading it is used in other processes, such as industry and manufacturing.

Biomethane is indistinguishable from natural gas, so can be used in existing gas infrastructure.




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The Malabar project, in southeast Sydney, is a joint venture between gas infrastructure giant Jemena and utility company Sydney Water. The A$13.8 million trial is partly funded by the federal government’s Australian Renewable Energy Agency (ARENA).

Sydney Water, which runs the Malabar wastewater plant, will install gas-purifying equipment at the site. Biogas produced from sewage sludge will be cleaned and upgraded – removing contaminants such as CO₂ – then injected into Jemena’s gas pipelines.

Sydney Water will initially supply 95TJ of biomethane a year from early 2022, equivalent to the gas demand of about 13,300 homes. Production is expected to scale up to 200TJ a year.

Two women look over the Malabar plant
The project involves cleaning and upgrading biogas from the Malabar Wastewater Treatment Plant.
Sydney Water

Biomethane: the benefits and challenges for Australia

A report by the International Energy Agency earlier this year said biogas and biomethane could cover 20% of global natural gas demand while reducing greenhouse emissions.

As well as creating zero-emissions energy from wastewater, biomethane can be produced from waste created by agriculture and food production, and from methane released at landfill sites.

The industry is a potential economic opportunity for regional areas, and would generate skilled jobs in planning, engineering, operating and maintenance of biogas and biomethane plants.

Methane emitted from organic waste at facilities such as Malabar is 28 times more potent than CO₂. So using it to replace fossil-fuel natural gas is a win for the environment.




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It’s also a win for Jemena, and all energy users. Many of Jemena’s gas customers, such as the City of Sydney, want to decarbonise their existing energy supplies. Some say they will stop using gas if renewable alternatives are not found. Jemena calculates losing these customers would lose it A$2.1 million each year by 2050, and ultimately, lead to higher costs for remaining customers.

The challenge for Australia will be the large scale roll out of biomethane. Historically, this phase has been a costly exercise for renewable technologies entering the market.

A woman cooking with gas
Biomethane will be injected into the existing gas network and delivered to homes.
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The global picture

Worldwide, the top biomethane-producers include Germany, the United Kingdom, Sweden, France and the United States.

The international market for biomethane is growing. Global clean energy policies, such as the European Green Deal, will help create extra demand for biomethane. The largest opportunities lie in the Asia-Pacific region, where natural gas consumption and imports have grown rapidly in recent years.

Australia is lagging behind the rest of the world on biomethane use. But more broadly, it does have a biogas sector, comprising than 240 plants associated with landfill gas power units and wastewater treatment.

In Australia, biogas is already used to produce electricity and heat. The step to grid injection is sensible, given the logistics of injecting biomethane into existing gas infrastructure works well overseas. But the industry needs government support.

Last year, a landmark report into biogas opportunities for Australia put potential production at 103 terawatt hours. This is equivalent to almost 9% of Australia’s total energy consumption, and comparable to current biogas production in Germany.

The distribution of reported operational biogas upgrading units in the IEA Bioenergy Task 37-member countries.

Current use of biogas in Australia.

A clean way to a gas-led recovery

While the scale of the Malabar project will only reduce emissions in a small way initially, the trial will bring renewable gas into the Australia’s renewable energy family. Industry group Bioenergy Australia is now working to ensure gas standards and specifications are understood, to safeguard its smooth and safe introduction into the energy mix.

The Morrison government has been spruiking a gas-led recovery from the COVID-19 recession, which it says would make energy more affordable for families and businesses and support jobs. Using greenhouse gases produced by wastewater in Australia’s biggest city is an important – and green – first step.




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The Conversation


Bernadette McCabe, Professor and Principal Scientist, University of Southern Queensland

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