Treating Wastewater Using Just Carbon

Marina Gutierrez (ESR11)

What do I do in my PhD?

Where there is an infrastructure for wastewater treatment, its performance can be enhanced by adding a specific material. I am that person who looks forward to obtaining clean water by adding activated carbon to a tank. That’s it.

When we talk about our experience of humanity’s impact, we realize it is visual and sensorial. Charts, graphs, and pictures are regularly deployed to give visual form to climate change phenomena: melting ice caps, the effects of rising water levels, areas of deforestation.

However, an omnipresent material as carbon can help us to solve a problem we don’t see at first sight.

Over the last few decades, the occurrence of micropollutants has become a worldwide issue in aquatic environments. There is an extensive use of chemicals from the anthropogenic and natural origin of which the conventional wastewater treatment facilities are not designed to remove. Complex mixtures at low concentrations of these trace substances lead to the creation of advanced treatment processes, which can deal with their removal before discharge into surface waters. In this way, activated carbon is a unique material. Its remarkable adsorption capacity makes it suitable for the separation and purification of chemicals and thus useful for a vast group of industries. In recent years, its use has addressed new scopes, playing an interesting role involving water purification.

Activated carbon is just charcoal with a particular characteristic: the space (porosity) enclosed between its carbon atoms is what makes it active. That is, we have a material partially “empty”. We do have carbon atoms, but they are distributed in a very particular way at the nanoscale level.

Charcoals are as old as history itself. Their use to relieve digestion problems was already known by Hippocrates, and in recent times their use is related to fireworks and barbecues. Their commercial applications have been expanded over the last centuries so far that have achieved new inconceivable uses. Nowadays, charcoal – the bulk material – can be transformed into an innovative one – activated carbon – with promising properties at the nanoscale.

It can be manufactured from hardwoods, coconut shells, fruit stones… which makes it suitable to be produced everywhere. Manufacturers can also create several types of activated carbons, each of them with different properties and specific applications.

So, what can I do with just one material with so many options to explore?

Let’s start with the easiest option. Enhance the current facilities for wastewater treatment!

Its great capacity for sorption could help remove one pickiest type of pollution – the microcontaminants in water. They are present at very minimal concentration; they have small size – just a bunch of atoms, and sometimes they are not easily degradable.

But how? Just by adding it in the tank where you were already treating the water. Through a filtration step, you can retain the activated carbon within the tank. Hence, the effluent water is clean and without micropollutants.

We know it works. Previously, scientists transformed banal charcoal to obtain activated carbon. Now we are looking at how to improve micropollutant removal.

Where do we add the activated carbon? How much should we add to the tanks? How much time do we need to wait to have the desired effect? Should we place the activated carbon attached to a surface? Or should it be free in the tank? Which is the relevance of the filter? Should we recirculate the water?

Questions are infinite! But I hope to have some answers at the end of my PhD.

Image source
https://lifeandsoulmagazine.com/2018/02/03/binchotan-charcoal-a-natural-way-to-purify-tap-water/
References
Burtynsky, E., Baichwal, J., De Pencier, N., Boettger, S., Waters, C., Zalasiewicz, J. A., & Atwood, M. (2018). Anthropocene. Göttingen: Steidl.
Marsh, H., & Reinoso, F. R. (2006). Activated carbon. Elsevier.