Tag Archives: wastewater

Willow trees could help clean wastewater and produce drugs, fuel in the process

Will we ever find a cost-effective, environmentally friendly way to filter our wastewater? One new study says: willows.

Image credits Karolina Grabowska.

Filtering wastewater through the roots of willow trees could help scrub over 30 million liters per hectare of trees, which is quite a decent amount. While these trees won’t overtake our current water treatment sites just yet, they do show great potential for the job. Willow trees are not just very effective at extracting compounds like nitrogen out of wastewater, the team explains, but they can also tolerate high volumes of it (which is a bit of a prerequisite for a filtration system).

Additionally, the trees can eventually be harvested for their biomass, and used, for example, to make biofuels.

Help from trees

“We’re still learning how these trees can tolerate and treat such high volumes of wastewater, but willows’ complex ‘phyto’-chemical toolkit is giving us exciting clues,” said Eszter Sas, lead author of the study and a PhD student at Université de Montréal.

All in all, roughly six trillion liters of municipal wastewater are partially treated and discharged into the Canadian environment every year. A further 150 billion litres are dumped into the country’s surface waters completely untreated.

Looking for an environmentally friendly solution to the latter bit, the authors estimated how efficient willows, a water-loving tree species, could be at partially-filtering wastewater. They collaborated with a plantation in Quebec to gauge just how much water each tree can process.

They first expected to see the plants react poorly to the wastewater, and as such, see them process lower quantities of water and reduce their rate of growth (their ‘yield’). Willows today are used as a source of raw materials for biofuels and certain chemicals, including some used for pharmaceutical products.

But they report being quite surprised by what they found: a hectare of willow trees could treat around 30 million liters of primary wastewater per year, with yields actually increasing after the trees were exposed to wastewater. The nitrogen it contains is likely a key player in this increase, as nitrogen is not readily available to plants in the wild and forms a natural bottleneck in their growth rate. All in all, the willow trees tripled their biomass production during the study, the team notes. This is a prime source of raw material for renewable lignocellulosic biofuels, also known as second-generation biofuels, which do not compete for raw materials with our food supply networks.

The team also analyzed the biomass to establish what valuable chemicals can be extracted. In addition to salicylic acid (the active component in aspirin), which was present in high quantities, they report that several chemicals with antioxidant, anticancer, anti-inflammatory, and anti-microbial properties were present in high levels. Some of these were induced (not naturally found in willows), while some were naturally occurring, but present at higher levels than expected.

“While most of the induced chemical compounds have not been seen before in willows, some have been observed in salt-tolerant plants such as licorice and mangroves and are known to be potent antioxidants,” said Sas. “Intriguingly, a number of the induced chemicals are entirely uncharacterized and a mystery. It’s amazing how much novel plant chemistry there is still to be discovered, even in willow trees, which have been around for thousands of years.

“It seems likely that we’re still only scratching the surface of these trees’ natural chemical complexity, which could be harnessed to tackle environmental problems.”

Using natural solutions to wastewater treatment, such as filtration by willow trees, would help both reduce operating costs as well as provide a source of bioproducts, as identified by the team in their analysis. In essence, it’s a self-contained, self-operating recycling system that takes in waste and outputs fuel or medicine. Best of all, they should have a low environmental footprint, perhaps even help scrub CO2 out of the atmosphere overall.

“This concept of a biorefinery seems to be fantastic in allowing new environmental technologies to compete economically with the highly established markets of petroleum-based fossil fuels and chemicals while also helping to reduce ongoing human damage to the ecosystem.”

The paper “Biorefinery potential of sustainable municipal wastewater treatment using fast-growing willow” has been published in the journal Science of The Total Environment.

Wastewater analysis can reveal how wealthy, healthy, and well-fed you are

New research from the Queensland Alliance for Environmental Health Sciences in Australia is taking a very unusual approach to understanding the people in different communities: analyzing their sewage.

Image via Pixabay.

The team reports that varying income levels in different communities are linked to different food and drug consumption habits. While that conclusion itself isn’t exactly surprising, the way the team reached it is. This is the first study of its kind to show that these habits result in noticeable differences in the wastewater of individual groups of people.

Data dump

Preivous studies have shown that our drug consumption shows up in wastewater — but this is the first study to track other lifestyle traits using the same approach.

“Although [wastewater-based epidemiology] has primarily been used for measuring drug consumption, our results demonstrate that it can be used to identify sociodemographic patterns or disparities which associate with consumption of specific chemicals or food components,” writes the team, led by Phil Choi, a Ph.D. student at the Queensland Alliance for Environmental Health Sciences in Australia.

Wastewater from wealthier communities, where people had higher educational achievement, showed higher levels of vitamins, citrus, and fiber, the team reports. Wastewater from poorer communities, where people were overall less educated, showed higher levels of prescription pain relievers and antidepressant medications. Wastewater analysis can thus be used to gain insight into the consumption habits of individual communities, the paper concludes.

The study examined samples from 22 water treatment plants from six Australian states over seven consecutive days in 2016. The results were compared to 40 different socioeconomic factors from Australia’s national census (factors such as rent price and education level). Choi’s team then drew correlations between these factors and compounds found in the urine and feces of residents.

One of the strongest correlations the team identified was between socioeconomic status and prescription drug use. Wastewater treatments plants that serve areas associated with lower overall socioeconomic status had higher levels of several prescription drugs in their wastewater. These drugs are:

  • tramadol, an opioid pain reliever;
  • desvenlafaxine, an antidepressant;
  • mirtazapine, an antidepressant;
  • pregabalin, a prescription pain reliever;
  • atenolol, a blood pressure drug.

While people of lower socioeconomic status do report higher drug use than others, the team notes that the study shows their method is useful to analyze overall trends in a community.

Wealthier and healthier

Dietary fiber and citrus consumption were also strongly correlated with socioeconomic status — an indication that the wealthier households had an overall better diet. Wastewater from wealthier areas also had higher levels of proline betaine, a component of citrus flesh. Enterodiol and enterolactone, which are components found in the waste of people who eat plants, were also found in higher concentrations than in the wastewater of other areas, the team reports. These results suggest that people in wealthier communities mix more fresh fruit and vegetables in their diet.

Areas with higher overall rent rates — those over $470 a week — wastewater contained significantly higher levels of vitamins B3, E, and B6. The researchers identified these compounds by looking for their metabolites (what’s left after our bodies process a particular substance) in wastewater. Areas with the lowest rent rates — areas where people of lower socioeconomic status live — showed lower levels of these vitamins in their wastewater.

The study aims to showcase the role that wastewater-based epidemiology can play in efforts to monitor public health and illicit drug use. There is an ongoing debate on the merits of this field of research, the team notes, revolving particularly around the issue of privacy (the method can be used to gather data on people without their consent). For the moment, however, the findings confirm previous results on the relationship between socioeconomic status and health — richer people eat better and have fewer health issues, the team explains.

The paper “Social, demographic, and economic correlates of food and chemical consumption measured by wastewater-based epidemiology” has been published in the journal PNAS.

Scientists develop battery that taps into ‘blue energy’ formed when freshwater meets seawater

Deer Island wastewater treatment plant. Credit: Wikimedia Commons.

In coastal regions where freshwater mixes with seawater, a salt gradient is formed. Scientists at Stanford University have now found a way to tap into the energy of this gradient, which is sometimes called “blue energy”. The authors envision a future where their technology could be used to make waste-water treatment facilities energy independent.

Energy from moving salt

For every cubic meter of freshwater that mixes with seawater, about .65 kilowatt-hours of energy is produced — just about enough to power the average American home for 30 minutes. All around the world, coastal wastewater treatment plants have access to about 18 gigawatts of blue energy, or the equivalent of powering 1,700 U.S. homes for an entire year.

Other groups have previously succeeded in harnessing blue energy but the Stanford group is the first to employ an electrochemical battery rather than pressure or membranes.

“Blue energy is an immense and untapped source of renewable energy,” said study coauthor Kristian Dubrawski, a postdoctoral scholar in civil and environmental engineering at Stanford. “Our battery is a major step toward practically capturing that energy without membranes, moving parts or energy input.”

The group was led by Craig Criddle, a professor of civil and environmental engineering, who has a lifetime of experience developing technologies for wastewater treatment. The battery developed by Criddle and colleagues first releases sodium and chloride ions from the device’s electrodes into a solution, making a current flow between the electrodes. When wastewater effluent and seawater are combined, the electrodes reincorporate sodium and chloride ions, reversing the current flow. According to the researchers, energy is recovered during both freshwater and seawater flushes. There is no initial energy investment required, nor is there any need for charging. In other words, this is a passive energy system that doesn’t require any input of energy.

The power output is relatively low per electrode area, but the authors highlight the fact that their technology’s strong point lies in its simplicity. The blue energy capturing device doesn’t have any moving parts and passively generates energy without the need for any external instruments to control voltage or charge. The electrodes are manufactured from Prussian Blue, a material widely used in medicine, which costs less than a $1 per kilogram, as well as polypyrrole, which costs less than $3 a kilogram.

If the technology is scaled, it should prove robust enough to provide energy for any coastal treatment plant in the world. Any surplus production could then be diverted to other nearby applications, such as desalination plants. A scaled version that could someday be used in a municipal wastewater plant is currently being designed by the Stanford researchers.

“It is a scientifically elegant solution to a complex problem,” Dubrawski said. “It needs to be tested at scale, and it doesn’t address the challenge of tapping blue energy at the global scale – rivers running into the ocean – but it is a good starting point that could spur these advances.”

The findings appeared in the American Chemical Society’s ACS Omega.

Want to assess antibiotic resistance in an area? Test wastewater, researchers say

A study of seven different countries found that clinical antibiotic resistance in a region is reflected by the number of antibiotic resistance genes in wastewater. Wastewater could act as a cradle for antibiotic-resistant bacteria but thankfully, most treatment plants seem to be able to successfully eliminate these germs.

Image credits: Chesapeake Bay Program.

Drug-resistant bacteria are no longer a problem for the future — they’re already here and causing massive damage. In Europe alone, they kill over 33,000 people every year, and things aren’t much better in other parts of the world. This is just the tip of the iceberg, researchers say — the looming danger is so great that the World Health Organization (WHO) has declared drug resistance one of the “biggest threats to global health.”

However, drug resistance can be difficult to assess in a large area. In a new study carried out in seven European countries, researchers studied drug resistance in 12 plants, comparing the results to bacteria found in samples collected from patients in that region. They also compared results to overall antibiotic consumption in the areas.

They found that antibiotic resistance in wastewater bacteria is a good indicator of antibiotic resistance in the general population. They also painted a rough pattern of resistance on the old continent. People in southern countries (Spain, Portugal, Cyprus) and Ireland consume more antibiotics than those in Finland, Norway, and Germany. Consequently, countries in the first group also exhibit higher levels of antibiotic resistance.

1. Antibiotic consumption by country in 2015; 2. Number of E. coli bacteria resistant to antibiotics in clinical specimens; 3. The extent of resistance in the wastewater of the investigated countries. Note the correlation between them. Image credits: Antti Karkman.

However, all countries exhibit at least some level of drug-resistant bacteria. The good news is that wastewater plants were effective at cleaning the water — at least most of the time.

“In this study, 11 of the 12 wastewater treatment plants under investigation mitigated the resistance problem, which seems to indicate that modern plants work well in this regard,” says lead author Marko Virta from the University of Helsinki.

“At the same time, an older plant or otherwise deficient purification process may end up increasing antibiotic resistance in the environment. We need more research findings from countries with high antibiotic consumption and less developed wastewater treatment practices.” It’s not clear what factors ensure that the bacteria is wiped out. Plausible factors are the age and size of the treatment plant, the techniques used, wastewater temperature, the amount of antibiotic residue in the water, and the interaction between the bacteria and various types of protozoa found in the water.

The problem is that this water is typically used in irrigation and ends up in agricultural fields, seeping into soils, plants, and ultimately ending up on our plates. More research is required to see what the best techniques are to thoroughly clean the water of drug-resistant bacteria.

The study has been published in Science Advances. DOI: 10.1126/sciadv.aau9124


Treated wastewater could release antibiotic-resistance genes into the wild



Image credits Iva Balk.

These compounds end up in the water supply, potentially driving the spread of antibiotic resistance.

A team from the University of Southern California Viterbi School of Engineering say that even low concentrations of a single type of antibiotic can lead to the spread of resistance to multiple classes of these drugs in the wild. The team reports that antibiotics present in wastewater plants are a key driver of such resistance in the wild.

Drug dumping

“We’re quickly getting to a scary place that’s called a “post-antibiotic world,” where we can no longer fight infections with antibiotics anymore because microbes have adapted to be resilient against those antibiotics,” said Adam Smith, assistant professor of civil and environmental engineering at USC and lead investigator of the study. “Unfortunately, engineered water treatment systems end up being sort of a hot-bed for antibiotic resistance.”

While most of the antibiotics we ingest get metabolized (broken down) inside our bodies, small amounts find their way into urine and end up in wastewater treatment plants. So far, so good.

The problem starts inside these plants, the team explains. One of the most common ways in which wastewater is treated is through a membrane bioreactor, a process that relies on filtration systems and bacteria to remove and break down waste products. While doing their job, some of these bacteria encounter those trace-levels of antibiotics. They either die upon exposure or adapt to become (more) resistant to the compounds.

Those that do adapt pass their genes off to later generations — or to their neighbors via horizontal gene transfer.

One of the more dire possible scenarios, the team writes, is for these antibiotic-resistant bacteria (or free-floating bits of their DNA) to make it through the filtration membrane, into waterways, eventually reaching the ocean. Treated wastewater is also sometimes recycled for use in irrigation, car washes, firefighting, or to replenish groundwater supplies — so these bacteria could reach human populations directly.

The team believes that the amount of antibiotic-resistant organisms in treatment plants could be reduced through alterations in the treatment processes. For example, the use of anaerobic (oxygen free) processes rather than aerobic processes, or more aggressive filtration, could help limit their development. The team tested a small-scale anaerobic membrane bioreactor and compared the resulting antibiotic-resistant populations to those in treatment plants and their effluents for different types of antibiotics.

They report that these profiles are different in the treatment plants and effluents, and therefore one cannot be used to predict the other. However, they also found that there wasn’t a clear-cut correlation between the antibiotics they introduced into the system and the resulting resistance — they found bacteria with genes allowing for resistance to multiple classes of antibiotics, although only one such compound was tested at a time.

“The multi-drug resistance does seem to be the most alarming impact of this,” Smith said. “Regardless of the influent antibiotics, whether it’s just one or really low concentrations, there’s likely a lot of multi-drug resistance that’s spreading.”

This is probably generated by gene elements called plasmids, which can carry resistance genes for several types of antibiotics at a time. Because of their extremely small size — 1,000 times smaller than bacteria — plasmids can easily make it through filtration systems in the treatment process and reach the environment. Needless to say, that would not be good.

The paper “Evaluating Antibiotic Resistance Gene Correlations with Antibiotic Exposure Conditions in Anaerobic Membrane Bioreactors” has been published in the journal Environmental Science & Technology.

Canadian fish know how to party: getting high on cocaine

Both prescription and illegal drugs such as morphine, cocaine and oxycodone have been found in surface waters in Canadian rivers. New research shows that wastewater discharged from wastewater treatment plants in the Grand River watershed of southern Ontario has the potential to contaminate sources of drinking water with these drugs.

Looking for traces of illegal drugs in water.
Credit: McGill University

The study, published in Environmental Toxicology & Chemistry, shows that while such substances are found in relatively limited quantities, their concentrations remained constant downstream from the source – a water treatment plant discharge.

The water treatment plant removes the bulk of contaminants from wastewater coming from a wide range of sources, be it households or chemical plants, before discharging it into the river. Further down, a drinking water treatment plant then further treats the water prior to consumption.

“Improving our wastewater treatment processes can help clean up our drinking water,” said lead author Prof. Viviane Yargeau, of McGill’s Department of Chemical Engineering. “While previous studies have shown that there are trace elements of various chemicals that remain in our drinking water, what is novel about this research is that we looked at the chemicals that are found in the water course between the wastewater treatment plant and the drinking water treatment plant. And what we found has some disturbing implications for the aquatic environment.”

“These results demonstrated a link between wastewater plant discharges and quality of potable water sources,” he added. “Although drinking water treatment plants remove most of the contaminants found in our drinking water, we believe that if improvements are made to wastewater treatment plants to protect the sources of drinking water, this will prove a more effective way of dealing with the problem in the long run — as this strategy would also protect the aquatic environment and all the plants, insects and fish that are found there.”

The next stage in Prof. Yargeau’s research will be a five-year project to look into how improvements of wastewater treatment and natural processes along rivers impact the presence of contaminants of concern in our drinking water.


World’s water streams affected by pharmaceutical pollution

A new study stresses the overlooked hazards that dumped pharmaceuticals found in wastewater pose to the world’s freshwater streams. So far, the impacts and consequences on water quality and aquatic life are unknown or under researched, and the authors hope their findings might warrant more work in this direction.

Dr. Emma Rosi-Marshall, lead author of the study published in the journal Ecological Applications and a scientist at the Cary Institute of Ecosystem Studies, looked at how  six common pharmaceuticals influenced similar-sized streams in New York, Maryland, and Indiana. These were caffeine, ciprofloxacin, metformin, cimetidine, ranitidine and diphenhydramine. The synthetic compounds that end up in the world’s streams as a result of aging infrastructure, sewage overflows and agricultural runoffs are in much greater number, however, ranging from stimulants and antibiotics to analgesics and antihistamines.

The focus of the study was on biofilms or the slippery coating found on stream rocks, as they’re most easily recognized as. These coatings, made out of algae, fungi, and bacteria all living and working together, are center to supporting aquatic life and greatly influence water quality, as they recycle nutrients and organic materials, while also making up a fundamental food source for invertebrates, which at their own term form the basic food source for other animals, like fish.


The authors’ findings suggest that the effects of waste pharmaceuticals are worrisome and need to be controlled. One of them, for instance, antihistamine has been found to dry out biofilms, while when exposed to diphenhydramine a 99 percent drop in biofilm photosynthesis was experienced. Diphenhydramine also caused a change in the bacterial species present in the biofilms, including an increase in a bacterial group known to degrade toxic compounds and a reduction in a group that digests compounds produced by plants and algae

“We know that diphenhydramine is commonly found in the environment. And its effect on biofilms could have repercussions for animals in stream food webs, like insects and fish. We need additional studies looking at the concentrations that cause ecosystem disruption, and how they react with other stressors, such as excess nutrients,” said  Rosi-Marshall.

Other substances’ influence on water biodiversity and quality were also found to have a measurable effects both alone and in combinations, using pharmaceutical-diffusing substrates. More work is required, however, for a broader picture of how various drugs, both alone and in mixtures, effect the freshwater stream environment. Results so far stress that a more thorough looks is required and considering most water treatment facilities in the world lack the necessary tools to filter out pharmaceuticals, the situation all of a sudden seems a lot more serious than at first glance.