In Monday’s post I mentioned how much I loved London when I visited – but London wasn’t always such an appealing place. During the Industrial Revolution, it was filthy and polluted. The stench was appalling, and an episode of particularly foul smells from the Thames River in 1858 was known as the “Great Stink.” Life expectancy in England’s urban areas was markedly lower than in the countryside.

This filthy environment was the site of a public health breakthrough. During the 1854 cholera epidemic in London, the physician John Snow mapped the cholera cases from an outbreak in the Soho district and realized that those falling ill got their water from the same pump on Broad Street. At the time, the prevailing theory held that cholera spread through the air, rather than water, so Snow’s assertion of the pump’s role in the cholera epidemic wasn’t immediately embraced. He finally convinced community leaders to remove the pump’s handle to prevent further exposure. This story is widely told in introductory public health classes when explaining how to study diseases in populations (and it was an obvious choice when we were wondering what to name a public health blog).

It was later reported that the well feeding the Broad Street Pump was adjacent to a cesspit in which the diapers of baby suffering from cholera were washed. John Snow didn’t identify the mechanism of the disease exactly, but he hit upon the main problem: a contaminated water supply. Today, we know that drinking water contaminated with the feces of an infected person will spread cholera and other diarrheal diseases. But this knowledge hasn’t stopped diarrheal illnesses from claiming 1.5 million lives each year.

“Flying Toilets” in the Kibera Slum
In many parts of the world, sanitation facilities are inadequate or nonexistent. One of the oft-cited examples of inadequate sanitation comes from the Kibera slum in Nairobi, where some slum dwellers without adequate toilet access defecate in plastic bags and throw them outside. The bags then become a health hazard, especially in the rainy season.

Many slums do have shared latrines or pay toilets, but rarely in sufficient numbers – in Kibera, the BBC reports that the average is one toilet per 2,000 residents. Some facilities require payment, which can fund their upkeep but discourage residents from using them. Others deteriorate and become unusable. Not having a toilet in one’s home can be dangerous as well as inconvenient; women, in particular, risk being assaulted as they walk down unlit alleys to visit toilets at night.

A new product called the Peepoo may help alleviate the flying toilet problem; it’s a biodegradable bag coated with a chemical that reportedly turns feces into fertilizer. If the bags’ contents can be made valuable, entrepreneurs might be willing to collect them. But there will still need to be a system for getting human waste – even in a transformed state – out of the crowded slum and into gardens.

Spreading Sanitation
The Millennium Development Goals are a useful metric for seeing how the world’s doing on things like clean water and education. The sanitation target focuses on halving the proportion of the global population without access to improved sanitation facilities. (I should note that inadequate sanitation is a problem in rural as well as urban areas, but it can be a more visible – and smellable – problem in cities.)

An “improved” sanitation facility is defined as “adequate excreta disposal facilities (private or shared, but not public) that can effectively prevent human, animal, and insect contact with excreta.” Toilets connected to public sewer systems or septic systems qualify, as do many latrines. Latrines that use an open pit or require manual removal of excreta don’t qualify, nor do public latrines, because they are rarely maintained adequately and may not be accessible at all times.

In 1990, only 54% of the world’s population used improved sanitation facilities; the MDG target aims to bring that number up to 77% by 2015. In 2008, however, that number had only reached 61%. The increase represents 1.3 billion people who gained access to improved sanitation facilities between 1990 and 2008, but the World Health Organization/UNICEF Joint Monitoring Program estimates that we’ll still end up missing the target by one billion people.

As a commenter on Monday’s post pointed out, just installing sanitation facilities in areas that previously lacked them isn’t necessarily sufficient. People who grew up defecating in open areas or into plastic bags may not see a good reason to start using new facilities instead, and there are stories of newly built latrines being turned into storage sheds. Having learned from less-than-successful experiences, aid organizations are now supporting “demand-driven” water and sanitation services, in which governments and donors focus on creating demand rather than supplying hardware. See this post for more on creating demand for sanitation facilities.

Cities and Sewage
Here in the US, many people don’t think about what happens to their feces after they flush. In our densely populated areas, toilets are connected to a sewage system that brings waste to a sewage treatment plant, where harmful organisms and other contaminants are removed. (Wikepedia has an in-depth description and a nice diagram of how this happens if you want details.) The end result is solid sewage sludge – which can be landfilled, incinerated, or treated for use as fertilizer – and liquid effluent, which is discharged into a waterway.

Many of the US’s older cities have inadequate sewage systems, though, which can end up discharging untreated sewage directly into streets or surface waters when there’s a broken pipe or equipment failure or when a big storm dumps large amounts of water into the system in a short time. In some cases, the sewage can even end up in people’s basements or lawns. These related problems are known as Sanitary Sewer Overflows (that’s when an equipment failure leads to a discharge) and Combined Sewer Overflows (which arise because stormwater and sewage feed into the same pipes, and a heavy rainfall can overwhelm the system’s capacity). Cities are aware of these problems and are working to replace problematic systems, but such infrastructure work is resource-intensive, and residents aren’t always thrilled about paying to fix problems they weren’t aware of in the first place.

We’re also seeing concerns arise about chemical substances that sewage treatment plants weren’t designed to treat but that are becoming more common in our sewage, like pharmaceutical residues and nanoparticles. Substances that are designed to kill bacteria might affect the beneficial bacteria used in wastewater treatment plants. And if these substances survive the treatment process, they’ll either end up in the sewage sludge or discharged effluent, which means they could be applied to a field or end up in a waterway that supplies drinking water.

So, even in a country where we take our sanitation system for granted, old and new challenges still exist. The task of keeping us safe from our shit will remain one of our most important undertakings.

Comments

  1. Who does not know that ‘eating’ and ‘sheeting’ as well rest and cloths with opportunities to work and earn a wage for comfort and luxury for us and their children are basic human rights.In rural Bangladesh the Migrant Workers from the Middle East [22 lac Bangladeshi workers in Kingdom of Saudi Arab] did change many lives with better sanitation but in a country where 3 Crores people are unemployed and those who are employed are on very fragile economic status to withstand natural calamities if does fall upon them like Sidr in 2008 ,could we ask the Inhabitants of Slums in Old Dhaka nad new parts like Uttara as to their obligation to maintaining the minimum safety in Public Health? we better start doing something to improve what we have ,otherwise the “have nots’ are coming to “take over” in a way of that kind that none of us will benefit from.Muhammad Zamiluddin Khan’92,HSPH, a. k. a. Mr. Zamil Khan

  2. #2 Jennie
    December 8, 2010

    And, to compound the problem, if we need cities to produce more of their food we will need to deal with goat/rabbit/chicken poo too.

    Perhaps the bio-gas contraptions I heard a lot about last year would help make poo a more useful and less problematic. You put the poo in a black holder (black to warm in the sun and promote breakdown,) the poo breaks down releasing methane? and that is captured for use as fuel.

    I think I remember them being expensive initially. But, I haven’t heard much about them since.

  3. #3 Sharon Astyk
    December 9, 2010

    The other problems facing sewage treatment models in some places are the difficulty of supporting their water needs in the longer term in the dryest places. Even the lowest flush toilets use a lot of fresh drinking water – they can be grey-water adapted in most households, and that would be a good strategy, but it doesn’t deal well with the high water costs of the flush toilet. I’ve seen some interesting proposals in desert cities for a return to something along the lines of earth closets with compostable “plastic” drawers, collection, and muncipal high temperature composting of human wastes – there are pilot programs in Mongolia and Mexico that I’m aware of, and I suspect these models may need to be taken seriously as the water burden of the sewage model becomes heavier in dry places.

    Animal manures are far better composted than treated in sewage systems.

    Sharon

  4. #4 darwinsdog
    December 9, 2010

    Animal manures are far better composted than treated in sewage systems.

    Including manure from the human animal. In my compost heaps the combination of human & other animal manures, kitchen garbage and plant materials gets so hot that you can’t leave your hand in the steam that comes out the vent for more than a few seconds. This heat kills weed seeds & potential pathogens. Flush toilets waste water and valuable fertilizer.

  5. #5 Sharon Astyk
    December 9, 2010

    I generally agree with you DD, and we do humanure composting as well, but I live in a rural area. Humanure composting on an urban scale is a larger project – it is something that cities should have a plan for doing when/if sewage systems are disrupted for extended periods – the current strategies for backups and breakdowns involve putting plastic encased, methane producing garbage bags full of human feces in the waste cycle – but I do think the logistical problems of space, distance from water systems, etc.. get much greater in urban areas.

    At a minimum in areas that aren’t going to do full-scale humanure composting, urine, which is largely sterile and unlikely to carry pathogens (unless you have tularemia, which case you’ve got bigger problems than not being able to fertilize your garden with your pee) is easily segregated and added to compost piles or diluted 1-7 and used on garden plants. The very minute risk of doing so is eliminated by not doing it within 7 days of harvest.

    Sharon

  6. #6 Karsten
    December 13, 2010

    It’s great that sanitation gets discussed and it is possible to create urban systems that assure full reuse in a safe way. Sustainable Sanitation Design is planning this for urban slums asa business to assure health and food security.

    http://www.facebook.com/home.php?#!/pages/Sustainable-Sanitation-Design/94883771645

    Best regards,
    Karsten

  7. #7 Craigo
    December 13, 2010

    It is my understanding that the evolution of large cities was a result of advancements in civil engineering through provision of sanitation, clean water and roads to enable faster delivery of food, fuel and trade.

    For low tech solutions, the Blair Toilet was developed in Zimbabwe for low cost rural sanitation http://en.wikipedia.org/wiki/Blair_toilet and low tech hand pumps were developed for potable water supply. Other developments include separating urine and fecal material in the pedestal for later composting with ash from wood fires. World Vision was very active in providing rural community water supplies.

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