The sewage crisis taking place in Britain is an important inflexion point for many reasons. For those not following these events, many of the rivers in England are severely damaged by sewage return flows.
The significance is that in 1830 the First Industrial Revolution ended in Britain, giving them a comparative advantage in international trade. This caused a massive migration of people following the new jobs in the cities.
In 1831 there was a cholera outbreak in London, followed by two more in the next decade and a half. This became the backdrop to the events in the summer of 1858, when the water of the Thames became so putrid that the parliament could no longer function properly. Known as the Great Stink, it had many ramifications for policy and human health.
The most important outcome was a high-confidence epidemiological study that identified the source of the cholera epidemic as water from a specific well that had been contaminated by sewage. This changed the paradigm in which water was managed, ushering in the era of the engineered sewer and the wastewater treatment plant.
This idea was exported because of trade-driven colonialism, so centralised wastewater treatment plants became associated with modernity in developing economies.
This model was replicated in many colonies, but not in an even manner, because in Calcutta sewage was managed by a large wetland. In 2002 the East Kolkata Wetland became a Ramsar site after close investigation discovered that the microbiota living in the roots of the aquatic plants had mutated to the point where they were capable of processing complex molecules found in modern industrial waste.
This was an important inflexion point in the evolution of our thinking about wastewater management because two alternative paradigms were now competing. The British model was of a centralised system in which all waste is processed through a cascade of reactors, clarifiers and thickeners before being discharged safely back into the river.
In 2024, the effectiveness of this process is being tested in Britain where it is evident that the design has limitations. This shifts attention onto the alternative Indian model, now being called nature-based solutions in which engineered wetlands are increasingly seen as being more efficient and lower cost.
Nature-based solutions
The reasons for the efficiency are important to understand, so let us dig a little deeper. Engineered wetlands stay in place for a long duration so the microbiota can evolve over time. This is important to understand, so let us dwell a little on this single factor. The British wastewater model is an engineered system that has a constant flow through it, so the rate at which the bacteria evolve in response to environmental stimuli is defined by the retention time of the water within the system.
To illustrate this, let us assume that a sluggish bacteria can reproduce every 20 minutes. This means that in an hour there are three generations of bacteria, but in a 24-hour cycle we now have 72 generations. In a year this means that 26,280 generations will occur, but in a decade, we will have 262,800 generations.
From this, we can see that bacteria have the capacity to mutate and adapt to changing environmental conditions faster than humans can. Stated differently, my generation was exposed to the first antibiotics and modern medicines like vaccines. There are only two generations of people — my children and grandchildren — that have evolved in response to the invention of the antibiotic and vaccines that became mainstream for my generation in the middle of the 20th century.
In that same time, more than 1.8 million generations of bacteria have existed. This is for the slow bacteria that replicate every 20 minutes. For faster bacteria that replicate every four minutes, we have 9.1 million generations during a single 70-year human lifetime. They were also exposed to the same antibiotics and vaccines that passed through the bodies of billions of humans in partially metabolised form, but all reported to a wastewater treatment system somewhere.
But here is the kicker, because those effluent streams that went into a so-called “modern” sewage treatment plant, based on the British model originating from the Great Stink of 1858, also carry a range of partially metabolised medication, including antibiotics, antidepressants, birth control prophylactics, anti-inflammatories and anti-coagulant blood thinners.
Read more in Daily Maverick: New efforts to protect us from ‘forever chemicals’ won’t work unless the companies that use and produce them come forward (Part Four)
This becomes relevant when we note that as of 2021, over 177 million organic and inorganic chemicals have been produced and listed on credible databases. Of these, over 350,000 have been registered as chemical compounds — a defined combination of different elements or chemicals — each with its own unique Chemical Abstract Service (CAS) number.
Many have been synthesised to be durable, so they are not easily broken down into safe elements once they have been released to the environment. Microplastics, and what are known as “forever chemicals” (PFAS) found in everyday products, all flow down the drain into wastewater plants.
Untenable chemical flow
Stated simply, this means that the millions of new chemical compounds in everyday use are simply overwhelming the wastewater treatment technology first developed by the British after the Great Stink of 1858. The human ingenuity driving the chemical and pharmaceutical industries is producing more compounds than any traditional wastewater treatment plant can safely deal with, before discharging the “treated” water back into the nearest aquatic ecosystem.
In short, the human species is currently at an inflexion point. Can we mobilise the quantum of ingenuity needed to expand and advance our current capacity to treat wastewater at a rate faster than human ingenuity is developing new “forever chemicals” and complex molecules used in medicines?
In my professional opinion, this question is far more important than the need to limit carbon emissions by transitioning to renewable energy sources.
If we look at the numbers, we are confronted by a serious dilemma. Do we engineer human solutions by ignoring nature, or do we engineer solutions in partnership with nature?
If we choose the former, then wastewater engineers must be smarter than the cumulative ingenuity that created our capacity to invent the 177 million organic and inorganic chemicals that have been listed on credible databases. This is a daunting task indeed, and one in which we are currently falling behind.
Partner with nature
Alternatively, we can embrace Nature-Based Solutions in which we rely on the millions of generations of bacteria that have evolved over the last 70 years in the hope that they have kept pace with the environmental challenges that humans have thrown at them.
The East Kolkata Wetland has shown us that the microbiota found in the roots of the aquatic plants have mutated at a rate fast enough to metabolise many of the toxic molecules human ingenuity has produced. This suggests to me that the smart horse to back in the race against water pollution is probably going to be found in the field of microbiology, biochemistry and aquatic ecology, more than in the field of engineering.
This suggests to me that smart money is best invested in research and development that identifies those mutated bacteria that have survived the chemical cocktail we are discharging into our rivers and oceans daily. It is those bacteria, fungi and archaea that hold the key to human survival, in my professional opinion.
It is strange to think that intelligent life evolved from the swamps of ancient times, but increasingly the future of Homo sapiens (wise man) will be linked to our capacity to embrace engineered wetlands, populated by generations of mutated microbiota that can destroy the cocktail of chemicals we have produced since the mid-20th century.
How much human and financial capital is being invested in finding the answers to the vexing questions posed above? Is it enough? How do we integrate engineering design to embrace nature in a way that is socially acceptable and economically viable?
These are the questions I ponder in the autumn of my professional life. DM