Untapped potential – harvesting bioplastics from wastewater

Posted in: Events, Prizes & awards, Seminars & Conferences

With a background in Biotechnology, Viviane Runa is an enthusiast when it comes to improving the sustainability of processes. For her PhD project, Viviane has decided to put her efforts into wastewater treatment, and how the process can yield more than you might think.

In June 2019, she travelled to Edinburgh to attend the 20th UK Young Water Professionals Conference, where she shared her research with students, researchers and professionals who share a thirst for research and a passion for water.

Here Viviane shares the work that earned her a presentation prize for best content and delivery, and how she found the conference.

A large part of my work is about harvesting useful things from unexpected places. As society moves towards a Circular Economy, wastewater is increasingly perceived as a source of valuable compounds rather than just something that requires treatment before being discharged into the environment. Nutrients, minerals and clean water can be recovered from wastewater – as well as bioplastic!

Activated sludge – the mixed community of microbes that carries out the biological treatment of wastewater – is composed of a diverse range of bacteria that remove the organic matter and nutrients from wastewater. Some of the bacteria are able to produce molecules known as polyhydroxyalkanoates (PHA). PHA are naturally produced by these bacteria when environmental conditions make bacterial growth challenging (for example when the concentration of nutrients or oxygen are low), provided there is also a source of carbon available. The bacteria accumulate the carbon source inside themselves as PHA – a storage compound which they will ‘consume’ to survive when facing a harsh environment.

PHA have great potential as an alternative or replacement for some petroleum-based plastics. In addition to being biodegradable and suitable for medical and pharmacological purposes, PHA plastics behave similarly to conventional plastics, for instance in durability or flexibility. PHA are often made out of different types of building blocks, and their arrangement will determine the properties of the final product. By modifying these building blocks, we can fine-tune PHA depending on the applications we want it for. However, despite the advantages over petroleum-based plastics and the potential of fine-tuning it, PHA plastic is still not competitive due to its high production costs.

The possibility of producing PHA plastic from wastewater using activated sludge has been explored in an effort to achieve a cost-effective process. One of the most promising scenarios is making PHA as a by-product of the biological treatment process of wastewater. This strategy takes advantage of the existing process and infrastructures, provides a continuously available source of carbon that bacteria can use for PHA production, and supports the Circular Economy concept. A report titled PHARIO, released in 2017, describes the successful and profitable production of PHA at a pilot scale in a real operating wastewater treatment plant in the Netherlands.

In this research project, I worked to determine the potential of UK wastewater treatment plants to produce PHA under normal operating conditions. In order to achieve this, I collected activated sludge samples from 11 treatment plants in the UK and analysed them to quantify the amount of PHA present. As it turns out, all the samples contained 2 to 13 grams of PHA per 100 grams of dried biomass. I also observed that the amount of PHA was higher in samples coming from treatment plants that had low oxygen concentrations in areas of their process – which makes sense given that bacteria start making and storing PHA when they are in stressful conditions.

So UK wastewater treatment plants are already producing PHA – even though they haven’t been designed for this – and given the right conditions they could produce even more. PHA as an added-value product of wastewater treatment is a great opportunity and something for water utilities to explore in order to promote a sustainable, integrated development.

Attending the 20th UK Young Water Professionals Conference was a great opportunity to engage with people with the same interests, exchange experiences and perspectives on water, and hear how different entities in the water management cycle contribute to the sustainability of the process. This experience left me more motivated to continue my research and eager to participate in the next edition of this conference.

I would like to acknowledge Dr Ana Lanham for the supervision of this research project and the Centre for Sustainable Chemical Technologies for supporting my attendance at the conference.

 

Posted in: Events, Prizes & awards, Seminars & Conferences

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