Make Wastewater Drinkable Again

The recycling of wastewater in sewage treatment plants like this one decreases pollution of the environment while increasing production of fertilizers and energy. Photo credit: Ivan Bandura

The recycling of wastewater in sewage treatment plants like this one decreases pollution of the environment while increasing production of fertilizers and energy. Photo credit: Ivan Bandura

Do you like your water to be fresh, crisp and bacteria free? I do too. But having clean drinking water is a privilege that many places around the world still do not have. Part of the reason for that is because the purification process is expensive, complicated, and lengthy, and part of the reason for THAT is because the stuff in water that makes us sick is really hard to get rid of.

Luckily, the technology required to produce clean, safe drinking water is being implemented by more and more corporations around the US. One of these projects, called the Pure Water project, plans to supply one-third of San Diego’s drinking water by 2035. They plan to use advanced water treatment technologies and something called surface water augmentation to redirect wastewater away from treatment facilities that discharge into the ocean and recycle it, making our drinking water cleaner, our oceans less polluted, and drought-prone areas like Southern California less at-risk for water shortages.

Wastewater represents a huge and valuable source of fresh water that we are currently, well, wasting. Photo credit: Shutterstock

Wastewater represents a huge and valuable source of fresh water that we are currently, well, wasting. Photo credit: Shutterstock

Considering this recycling of wastewater is the first initiative of its kind to be implemented in California and is only practiced in a handful of facilities around the world, this is a SOLID step forward on the goal to get accessible, clean water to the people that need it.

A demonstration facility currently exists in San Diego as a sort of “trial run,” and more than 30,000 water quality tests performed there have shown that the technologies used can produce drinking water that conforms to federal and state drinking water standards. Other than the water quality tests, however, there haven’t really been any studies that look in depth at the methods of purification, and how much contamination is removed by each step in the lengthy process.

Before I get into how Pure Water San Diego works, let’s talk about why wastewater presents a problem. Bacteria and pathogens are usually the first culprit in people’s minds when they think of dirty water, but it turns out, these are actually among the easiest to remove. The smallest bacteria are around 0.00003 centimeters long, which (and this may surprise you) are considered relatively large compared to the other inhabitants of the micro world: things like complex molecules and viruses. A small enough filter can catch most (if not all) bacteria, so as water treatment goes, this is the simplest step.

The other things in water that can affect us over the long term are a little more difficult to remove. There is no filter small enough to sift out compounds like heavy metals, chemicals (things like disinfectants and pesticides) and radioactive compounds, so we have to get a little more creative to remove these. The same goes for viruses, which have more of an impact than people think: they may be tiny, but they have a huge effect on the life (and importantly, the bacteria) around us.

Electron microscopy image of a bunch of bacteriophages (in green) attacking and lysing a bacteria (in purple). This is happening all around you, all the time. Image credit: M. Rohde and C. Rohde (Helmholtz Centre for Infection Research, Braunschweig, Germany) and colorized by Dwayne Roach (Institut Pasteur).

Electron microscopy image of a bunch of bacteriophages (in green) attacking and lysing a bacteria (in purple). This is happening all around you, all the time. Image credit: M. Rohde and C. Rohde (Helmholtz Centre for Infection Research, Braunschweig, Germany) and colorized by Dwayne Roach (Institut Pasteur).

Viruses are little packets of genetic information that float around and use the machinery of other organisms to make more of themselves. They can’t replicate alone, and so many scientists don’t consider them to be “alive,” per say, but using other forms of life as a host, they do evolve, grow, and change the life around them. Bacteriophage, or phage for short, are viruses that specifically affect bacteria, and these bacterial viruses are constantly moving genes around in bacteria, giving them new abilities, like antibiotic resistance, or heat tolerance.

Many of the problems we see now with ‘superbugs’ and resistant bacteria exist because of phage, and their incredible ability to modify and move genetic information.

For a little more of an introduction to phage and how they impact the bacteria around them, watch the video below.

To sum it up: even if they don’t directly infect us, phage change the bacteria in and around us, and not always in our favor. Knowing that, it shouldn’t be a surprise that we don’t want them in our water. Unfortunately, phage are really freakin’ hard to remove from water.

But fear not! Pure Water San Diego is here.

The Pure Water project uses several steps in series to purify wastewater (basically, sewage). First, they filter it through several huge filters designed to remove the bacteria and particulates in the water, and add chlorine to stop biological growth. Next, they further disinfect water using ozonation, and pass it through a couple more tiny filters, one made of Biological Activated Carbon (or charcoal, which removes contaminants and viruses), and one made of a thin artificial membrane, which removes nutrients.

Following these filtering steps, the water is put through reverse osmosis, clarifying it further, before it is exposed to UV light, which serves as the final line of defense for forms of life or contamination in the water. What we are left with is ultra-pure water, ready to distribute and drink.

A summary of the many steps required in the Pure Water Project’s wastewater treatment process. The stars represent at what points we sampled, and looked for bacteria and viruses in the water. Credit: Elizabeth Dinsdale

A summary of the many steps required in the Pure Water Project’s wastewater treatment process. The stars represent at what points we sampled, and looked for bacteria and viruses in the water. Credit: Elizabeth Dinsdale

Here’s where we come in. In my lab, led by marine microbial ecologist Elizabeth Dinsdale, PassioInventa author Tiffany (in the Roach lab) and I are currently testing how the bacterial and viral communities in wastewater are affected by each step of this process. To do this, we paired up with graduate students Arnold Wong in the Verbyla lab at SDSU Engineering and Amanda Pham in the Gersberg lab at SDSU’s School of Public Health, as well as our very own Maria Mora of the Dinsdale lab. Our team sampled water after each purification step, pushed the water through this really tiny “Sterivex” filter to collect the bacteria (see this article for more Sterivex fun), and then extract the viruses (which are small enough to pass through the filter) from the remaining water.

From there, we send off the DNA samples for sequencing, and using a tool called metagenomics, we are able to identify all of the bacterial and viral species present in the water samples. It doesn’t tell us how many of these organisms are in the water, but it does tell us who is there, and this is hugely helpful.

The Pure Water treatment plan comes full circle; maximizing the use of recycled water and conserving a critical resource. Credit: Pure Water San Diego

The Pure Water treatment plan comes full circle; maximizing the use of recycled water and conserving a critical resource. Credit: Pure Water San Diego

With this information, we can figure out how pathogenic or dangerous those bacteria and viruses are, and make sure the water treatment process is fully removing the bad stuff. With the sequences from all of the samples, we will get a pretty good idea of what these communities look like through the treatment process, and more importantly, what they look like at the end. If all goes well, we shouldn’t see anything in the pure water.

Studies like this are important because they allow us to implement new technologies and ultimately improve livelihoods, while making sure that our methods are safe. In Southern California, only 8% of the wastewater leaving people’s homes is actually recycled, while the rest is treated and released into the ocean, wasting a precious resource. Pure Water San Diego is a step towards sustainable, reliable water infrastructure, and if successful, will hopefully promote other governments and agencies to follow suit.

With all hope, someday the global scarcity of clean, accessible drinking water will be a thing of the past.

-Jason

Photo credit: Katie Joie

Photo credit: Katie Joie


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