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Purple bacteria may be the key to sustainable waste management

ByNatalie Nosenko

Dec 6, 2018
Credit: miraLove via Pixabay

When we speak about waste management, we mainly mean recycling waste such as paper or plastic and glass. In fact, many other things can be recycled, including wastewater. Current treatment is mainly about processing wastewater with the purpose of returning it into the environment and disposing of produced sewage sludge. The latter becomes biosolids and is recycled to land, which reduces the need forartificial fertilizer and improves soilstructure.

Wastewater treatment plants contribute to climate change by emitting carbon dioxide, methane and nitrous oxide during biological treatment of the water. Carbon dioxide is also emitted during the production of the energy required for the plant’s operation. Therefore in recent years the issue of wastewater treatment sustainability was focused on minimizing energy production emissions and those of the plant itself. In other words, the goal is to make the plants energy neutral.

Biological treatment of wastewater means that it is treated with bacteria, both aerobic (with oxygen) and anaerobic (without oxygen). More specifically, purple phototrophic bacteria are used in wastewater treatment.

These belong to the biggest and most diverse group of bacteria that use infrared light as an energy source for their metabolism.

As a collateral product they release carbon dioxide and methane. However, the main feature of their metabolism is its versatility.

They can perform a range of metabolic reactions, some which have hydrogen as a product.

Latest research carried out at the University Rey Juan Carlos in Madrid found that it is possible to tune the metabolism of the bacteria to decrease carbon dioxide emissions and increase hydrogen production.

Hydrogen is a secondary source of energy,commonlyreferredtoasan energy carrier.

As an energy of the future, hydrogen has a number ofadvantages,firstofwhichisthatitisconsidered not to be polluting.

There are no gas emissions associated with hydrogen, and as a result use of this gas does not contribute to the climate change.

According to researchers at the University Rey Juan Carlosin Madrid, “for a medium sizedwastewater treatment plant, the direct transformation of organic contamination into hydrogen could yield energy for 43-107 houses.”

However, the majority of this energy would go towards the direct needs of the plant.

Even though this technology is only at the stage of design and patenting, there are already water companies that are interested.

The technology can potentially help to turn wastewater treatment plants into biorefineries and produce additional energy without greenhouse gases.

Learning how to use photosynthesis to transform organic contamination into hydrogen is another step towards zero-carbon emissions.


Image credit: miraLove via Pixabay

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