Sewage, a never-ending flow that can feed a nation?
The marvel of modern life is that it is filled with conveniences for things that we never really have to think about or take care of ourselves. They simply arrive or happen and we move on with our day.
Wait, hang on, is that the 3rd time you’ve flushed the toilet today?
Pause for a moment.
Magic isn't it, how it all just goes away when you’re done? One flush and you move on with your day as if it never happened. That right there is one of those modern conveniences I was talking about. For millions around the globe, they do exactly what you’ve just done, three to six times a day and it produces a massive amount of waste material that needs to be managed. Have you ever wondered, where it all goes, what happens to it and how it is used?
Take a moment to think about the sheer scale of the human waste problem created by us adhering to the call of nature each day. More than 7 billion people all relieving themselves three to five times a day, all around the world.
That's a massive amount of waste generated daily that needs to be managed and disposed of. To put it into perspective, let's take one large city as an example, say London in this case.
London collects an estimated 11 billion litres of wastewater every day. As with most older cities, the London sewage system is a legacy system and designed to cope with far less volume than it currently handles. Secondly, it is what is known as a combined system. What this essentially means is all domestic sewage, industrial sewage, and stormwater sewage are combined and all flow into the same sewage system.
One of the major issues with combined systems is that if the volume in the system exceeds the capacity of the wastewater treatment facilities to process the incoming waste material, the incoming wastewater bypasses the treatment facility and is dumped into waterways nearby. This has a huge environmental impact as raw sewage contains high levels of bacteria that absorb oxygen from water which kills off fish and water-dwelling plants. High levels of Ammonia, found in urine are further poisonous to aquatic life. We are not even talking about the thousands of other chemicals, heavy metals, microplastics, and many other contaminants present in wastewater.
In 2020, the BBC reported that the Modgen wastewater treatment in London released 2 billion tons of raw sewage into the Thames over 2 days in October due to incoming wastewater volume exceeding capacity. Failure to dump the sewage would have resulted in the system backing up into people’s homes, the streets, and businesses. It is estimated that 39 million tons of sewage flow into the Thames river each year for this reason.
To solve this ongoing problem they are in the process of constructing one of the largest wastewater infrastructure projects in history, the Thames Tideway. When complete, a 7,2 metre wide tunnel will run for 24km underground across the city taking with it sewage from the heaviest sewage producing areas and transporting it to the treatment facility at Abbey Mills. The ultimate goal of this project is to reduce the annual flow of raw sewage into the Thames by 94%.
This is just one example of one major city in the world. In many cities, the sewage goes directly into water bodies as the cost of building and operating treatment facilities is too expensive for them or the capacity far exceeds the capabilities of the facilities they have. With increasing water scarcity and rising pollution of our waterways becoming an increasing concern, there are renewed efforts to increase the implementation of proper sewer management in many cities around the world.
Like London, as these cities begin to upgrade or build new infrastructure to modernize sewage management and water treatment, a new waste problem develops at the treatment works. While I will not go into in-depth detail about the treatment process in this article, the end goal of the sewage treatment facility is to release water back into waterways that is unpolluted and safe for the environment.
This water is called effluent and the quality of effluent ranges depending on the treatment applied and local statutory requirements. In most cases when it is released, it is between 85% and 99% devoid of pathogens, chemicals, and harmful levels of nutrients as compared to when it first arrived.
The other by-product of sewage treatment is sludge. Sludge is a thick viscous material that is scraped from the bottom of the settling tanks. While there are a few important stages in its treatment, once it has been fully processed, an odorless solid cake, mostly devoid of moisture, results. This sludge cake must now be disposed of by the treatment facilities and daily there are tons of it. With ocean dumping and the burning of sludge banned in many countries, the sludge cake often ends up in landfills.
However, some of it may just have powered the wheat used to make the bread for that delicious sandwich you now find yourself eating whilst reading this article.
Rich in key ingredients including Nitrogen and Phosphorous, it is a super fuel for the growth of plants. In a radio documentary called the “Poop Train”, Radiolab followed the story of the flow of New York’s sewage and at one time its ultimate destination in Lamar, Colorado. While farmers in many states and lawmakers themselves had rejected New Yorks's sludge, some farmers in Lamar decided to give it a try. With a massive amount of free fertilizer on offer, they had nothing to lose and so they started using New York City’s sludge on their farmland.
Small at first, but do you know what happened next?
It supercharged their yield from 40 bushels to 66 bushels for the same area of farmland. The immense success of the biosolids (sludge) on their farmland led to more and more farmers signing up. Soon they were providing biosolids that covered about 10 000 acres a year and the demand far outstripped supply. Eventually, the poop train was stopped to cut costs, and alternative disposal methods were opted for.
Throughout the US, approximately half of the 5 million metric tons of biosolids that are produced each year are treated and converted into fertilizer for use on farmland. Its popularity with farmers is not only due to its effectiveness in increasing yield while improving overall soil health but also due to its commercial viability of it. Many treatment plants dispose of it for free or at a vastly reduced cost which makes it a good alternative to other commercial products available in the market.
Can an increased use of biosolids (sludge) be an effective way to combat pollution of our waterways from the direct dumping of raw sewage?
There is definitely a strong case for the recycling of organic material from human waste for reuse as fertilizer to power the production of more food for our consumption. It sounds like the ultimate circle of life story and one way we could positively impact the environment.
However, it's a touchy and controversial subject for many reasons. Firstly the reality that the food we eat could be powered by the output of that consumption is simply not palatable to most of us. Using human urine and faeces as fertilizer goes against what is deemed fit and proper and for many of us, it makes our stomachs turn at the thought. Ironically we have no problem with recycling animal waste for this purpose.
This reason isn’t really enough to stop the practice or require stricter controls over its use. Rather it just requires better education and enough time to normalize the practice.
The second far more plausible reason for pushing back against its use in commercial farming is the potential threat to our health and the overall environment. Along with the useful nutrients mentioned above, thousands of other chemicals and substances can be found in sludge.
Heavy metals and hazardous chemicals do not simply vanish in the treatment process as some would like you to believe. In fact, on the contrary, modern science has found some real cause for concern. In testing, not only is there the presence of heavy metals but also various pharmaceuticals and other industrial chemicals.
The huge concern is that plants growing on farmland treated with sludge can absorb these substances and through the plants, they can enter the food chain and ultimately impact our health. The uptake of heavy metals, pharmaceuticals, and other chemicals is dependent on the type of crops being grown however, very little monitoring and testing is taking place to determine the actual scale of the potential problem. These heavy metals and chemicals can have a serious impact not only on our health but also on the environment. If they enter our groundwater systems or the plants that are grown using biosolids it could result in serious illness.
The real issue here is that there is no consistent or required testing of sludge to determine what chemicals or substances it contains and the impact and actual uptake by plants grown using this material. Tighter regulation and better management are required in order to protect human beings from any possible negative impact. These regulations also need to stipulate the required standard of sludge for use on farmland. There are also no regulations required for the labeling of food products grown with sludge and so consumers are obliviously unaware while this goes unchecked.
There can be no debate that recycling human waste is an important and required process to ensure a cleaner more sustainable environment long-term. Not only does it result in cleaner waterways but it can also provide a sustainable source of fertilizer for our growing food production requirements. There is however a need for stronger regulation that governs exactly what sewage can be processed and how it is used for biosolids that are intended for agricultural use.
In many cities, there is a need to split the sewage systems in order to separate domestic sewage, industrial sewage, and stormwater sewage. This will enable more effective processing of our sewage waste and help to filter out many harmful substances in the production of biosolids intended for farming. With domestic sewage, education will be required to ensure that people are not flushing harmful items such as pharmaceuticals, non-biodegradable products, and chemicals.
In order to effectively implement these changes and change the status quo, it will require a collective monumental shift in our structures, systems, processes, thinking, and behavior as well as require huge investment.
Reengineering how we as a society think of and dispose of our sewage waste will better enable us to safely dispose of and recycle the sludge for our use in agriculture. There is the potential for a seismic shift in sewage management in the near future proportion of our food could well be powered by sewage.
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This article is brought to you by H2O Securities. H2O securities are committed to solving the global water crisis and taking an active role in the future of water infrastructure finance. To find out more about H20 securities go to https://h2o-securities.com/
