The link between environmental pollution from industrial sources and the rapid spread of antibiotic resistance has been exposed in a new UN report. What can be done to break the cycle?
Well-managed wastewater treatment plants, operated correctly, are probably, singularly, the most important barrier for disease spread there is – better than the best vaccine,” says David Graham, professor of ecosystems engineering at Newcastle University.
Graham is a co-author of a recent United Nations Environmental Programme (UNEP) report, Bracing for superbugs, which evidences the deadly spread of antimicrobial resistance (AMR).
AMR renders frequently used antibiotics ineffective at treating common bacterial infections, such as pneumonia. The World Health Organization considers it to be one of the top 10 global public health threats facing humanity today.
This is for good reason. In 2019, AMR was directly responsible for 1.27 million deaths worldwide, and associated with nearly five million – that’s two million more than coronavirus is estimated to have killed a year later. Left unchecked, fatalities could rise to 10 million annually by 2050, with the highest rates expected in Africa and Asia.
Image credit: Severn Trent Tittesworth Reservoir
To date, the main strategy to preserve working antimicrobials – bearing in mind there have been no new discoveries since the 1980s – has been to reduce their use in both animals and humans. While this is still a vital strategy, the UNEP report says that to halt the spread, chemical and biological end-of-pipe waste and pollution from pharmaceuticals, agriculture and healthcare sectors and municipal water systems must be either prevented altogether or better managed.
“The bottom line is, we want fewer chemicals and fewer resistant genes and bacteria entering the environment because we know once it’s out there, we can’t control it,” explains Graham. “It’s better to solve the problem at the source.”
How AMR spreads
AMR can occur when antibiotic traces, from waste produced at antimicrobial manufacturing sites and hospitals or passed from humans via the sewage system, are discharged into the environment, or when inadequately treated or untreated wastewater is used to irrigate farmland. Once there, these chemical traces start to interact with surrounding bacteria that can eventually modify themselves to develop resistance to those compounds.
Once mutated, these bacteria can then pass onto humans, animals and plants and even share their resistant traits with other bacteria.
To curtail the release of these chemicals and compounds into the environment, current waste management solutions can be re-engineered and retrofitted with new technologies to reduce both energy use and waste volume, says Graham. He worked with L’Oréal to do this at one of its manufacturing sites in Suzhou, China.
Most waste streams are separated into solids and liquids, with the liquids being passed through a form of biological treatment. This often uses an energy-intensive forced air system (known as aerobic) to help good bacteria to consume the carbon and reduce environmental impact. The removed solids are diverted and treated by a different process, often an anaerobic one.
The Suzhou facility tweaked this process. It stopped using a forced air system that was failing to break down preservatives added to increase product shelf-life. Instead, waste containing these compounds, around one-tenth, was siphoned out at source to be treated separately with chemicals. Everything else went through an anaerobic process that produced biogas, which can then be used for energy generation.
“Removing 70% of waste production and creating a valuable asset will leave a much smaller fraction that needs to be treated and released into the environment as effluent,” Graham explains.
Another facility in Addis Ababa, Ethiopia, he says, is using an anaerobic system followed by an aerobic one.
“Sequencing the wastes through different conditions can ecologically select away aerobic then anaerobic microorganisms from the wastewater, including resistant bacteria,” Graham explains.
Similarly, engineering consultancy Arup worked with food giant Del Monte at its pineapple cannery in the Philippines, switching from an aerobic to an anaerobic process with gas recapture, says Dr Bhavik Barochia, a digital consultant at the company and a microbiologist by background.
The switch cut contaminant levels in the water from its pineapple-washing process and enabled use of the gas to reduce the firm’s reliance on the intermittent coal-fire powered grid, says Barochia.
New technologies are also emerging in this space. One such innovation, says Barochia, is that developed by start-up WASE – a modular (single shipping container) microbial electrolysis system that takes a variety of waste and converts it into water, fertiliser and methane gas using an anaerobic digestion system sped-up by different bacteria.
“The process produces less waste and potentially less AMR, depending on which compounds are present,” he says.
Denmark-based Lyras has developed a UV light-based system to kill microbiology in coloured liquids, which UV can’t usually penetrate.
Marketing manager Ruben Andreas Riksted says the technology features a specially designed glass coil to ensure all particles of any colour liquid come into contact with the UV light, which is filtered so that only the bacteria-killing rays get through. Riksted says it can reduce energy use by 60–90% compared with normal pasteurisation processes, which is what the technology was originally designed for.
The spread of AMR through environmental pollution is more acute in the developing world, where waste management is either non-existent, lacking or poorly regulated.
Because of this geographical divide, Graham says he is not always in favour of advocating for expensive novel technologies being put onto waste facilities as it’s not sustainable for regions most at risk. Re-engineering or modifying the process is preferable.
The Antimicrobial Resistance Industry Alliance (AMRIA), which represents one-third of the human health antibiotics industry, is trying to instigate better practices within its sector.
Steve Brooks, an adviser to the alliance, says the scheme will help healthcare procurers buy more responsibly and encourage generic manufacturers to adopt it. “The issue won’t be resolved without action across the global supply chain; we’re trying to provide a path to that,” he says.
Monitoring the community
Experts do not yet agree on the level of resistant bacteria in wastewater streams that can be deemed ‘safe’.
One way to ascertain this this is through wastewater epidemiology. This entails routinely testing waste streams, such as sewers, for biomarkers of resistant bacteria and other molecules. Humans excrete an abundance of biomarkers into the toilet every day, which could provide an indication of population health.
Professor Barbara Kasprzyk-Hordern runs a wastewater epidemiology programme at Bristol University. It has been collecting sewer samples twice a week, for almost three years, to better understand the correlation between antibiotic use and antibiotic resistance.
The research was able to detect seasonal use of antibiotics, which spiked in the winter, but surprisingly this didn’t affect the level of resistance found within the community, which remained largely the same for long periods of time.
“This implies there is not a clear correlation between stopping the use of antibiotics and reducing resistance; it’s not as clear cut as that,” Kasprzyk-Hordern says.
Her team’s research also identified different levels of resistance in different areas, with higher levels found in highly densely populated communities.
“This shows there is something intrinsic to communities that drives resistance and provides us with an incredible overview of the health of a community that can be used as an early warning system,” she says.
However, experts agree there is still a need to link the data produced from wastewater epidemiology with public health decisions.
Barochi, who is working on the Welsh government’s wastewater bio surveillance programme, says that as the technology develops, more remote methods of sensing for bacteria could be carried out. “This data could be sent to a centralised system to create a bigger and better picture of what is happening.”
A Severn Trent service reservoir
Image credit: Severn Trent Service Reservoir
Sewage pollution in the UK
Something in the water
Outcry over routine sewage spills into UK waterways by water companies – last year there were 825 sewage spills per day – has forced the industry to pledge £10bn by 2030 to address the problem.
The exposure of the practice raises questions: why do these spills happen in the first place, and what is the associated risk for the spread of AMR?
Like many European countries, the UK has a ‘combined sewer system’, called so because it combines sewage and non-sewage run-off, such as rain. Countries that built their waste systems later, such as the US, tend to have a separate sewer for community waste and a drain system for storm run-off. This is considered more efficient and economical.
Heavy rain surging through a combined sewer’s biological reactor – where waste is treated and degraded – can wash out the good bacteria, causing it to malfunction and putting the system out of action for weeks. To avoid this, during a storm surge, a combination of rainwater and sewage is allowed to bypass the treatment process and enter public waterways.
Professor David Graham says research he and colleagues have undertaken in similar sewage systems in Spain showed that, when a bypass event happened, there was an increase in disease markers; however, this dissipates, as long as there is not another great storm event soon after. But ultimately, he says, no one really knows if storm overflows are a high risk for spreading AMR.
“What I can say is, where there is no wastewater treatment plant, we see 100 to 100,000 times higher levels of resistance compared to what’s found in UK rivers where there is effective treatment most of the time and occasional stormwater overflows.”
Professor Barbara Kasprzyk-Hordern agrees but warns: “We still have AMR, and we are affected by it.”
This is evident. In 2021, 9.9% of people with confirmed tuberculosis (TB), cases of which have been on the rise in the UK, were identified as having AMR to at least one of the four first-line antibiotics. Resistance in TB patients in the UK has been closely monitored after the number of multidrug-resistant cases shot up from 28 a year to 81 a year between 2000 and 2012.
Furthermore, despite tight regulation, companies involved in manufacturing disinfectants in the UK may release natural by-products in small amounts into the environment that could drive AMR because bacteria can adapt to all sorts of different contaminants, says Bhavik Barochia from Arup.
Potentially toxic and carcinogenic ‘forever’ chemicals, collectively known as PFAS, were recently recorded at 81 of 105 English river sites.
Graham agrees the UK’s wastewater systems should be monitored and manged better, but what is the right solution isn’t clear. “We still have a lot more to learn and do. Could we hydraulically balance the system? Can we put in separate sewer lines that go directly to the treatment plant?” he asks.
One option is to use a flow equaliser system which, when the volume gets too high, diverts the overflow so it can later be passed through the treatment stage at a slower pace, as with the Tideway Tunnel in London.
Wales-based company Power and Water claims to offer another viable solution. CEO Harry Cowan says its chemical-free modular wastewater treatment solution can reduce wastewater overflow by adding up to 50% capacity to a treatment plant. The technology provider is currently working with five out of 11 UK water companies, but Cowan says they are generally “incredibly resistant to innovation” and “discharge into waterways because they’re allowed to”.
Severn Trent, often cited as one of the worst offenders, is conducting an AI trial until 2025 from which it hopes to predict weather conditions, forecast maintenance, and control waste flow to better manage its network.
Water companies are expected to announce detailed plans in the summer about how they intend to use the £10bn investment to address sewage spills.
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