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How MIT Is Mining Sewers For Secrets To A City's Health

A cleverly designed network of robots and sensors will help researchers study the human microbiome.

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Most people don't want to know what's in their feces, much less examine it under a microscope. But for MIT professors Carlo Ratti and Eric Alm, the sludgy contents of urban sewage systems might be the answer to understanding the human microbiome on a mass scale.

It's a "natural aggregator," the professors say, one that can answer the question, "what is in our collective gut?" To find out, they built Underworlds, a platform for analyzing the molecular makeup of sewage. By understanding, for example, the human viruses or antibiotic resistant genes in a population, scientists will gain a clearer picture of public health. And design has played a key role in helping researchers find answers.

The Poop Robot
The first major obstacle to the research: How do you collect samples and analyze them in a hygienic way? You design a sewer robot.

"Initially, our sampling method was very ‘low-tech’: we lowered a 20-foot pole with a bottle taped to the end of it into a manhole and ‘scooped’ out our sample," says Ratti, the director of the MIT Senseable City Lab and the principal investigator of Underworlds. "We then moved to using a large peristaltic pump at street level that would pump sewage up from the manhole. But all these methods were quite messy and hazardous for the researchers."

Tired of acting like human pooper-scoopers, the Underworlds team developed "Luigi," an automated robot that collects sewage samples while beaming information like flow rate, temperature, pH, and oxygen concentration back to the scientists. Luigi is a tubular combination of an infrared receiver, which can be remotely controlled to tell the device to start or stop pumping sewage, and a motor that enables the robot to descend (or ascend) a line into the sewer. The robot's small peristaltic pump pushes the sewage water through the bot, and a filter at its base catches microbes to be analyzed before the rest of the water is flushed out of the device. The robots remain suspended beneath a manhole and do their work while staying at the same height so the scientists can accurately characterize the sewage flowing past them. Ratti estimates that once the project establishes a protocol for installation and collection, cities would permanently deploy between 10 and 20 robots, spread around different neighborhoods, into their sewage system.

A Smart Sewage System
The robots, along with the biochemical analysis of samples and real-time data, make for a "smart" sewage system. It's like Internet of Things, but with a decidedly less glamorous task. The data swimming in sewage could help monitor contagious diseases on a city-wide scale, which could help reduce medical costs and lessen the effect of outbreaks.

When the team sampled on neighborhood for 24 hours, they were able to trace the population's daily routines from meal times (through the amount of bile acids) to pharmaceutical and over-the-counter drugs. They found that Human Papillomavirus (HPV) and Kerkel Cell Polyomavirus were the most abundant viral pathogens—a public health concern, as both have been tied to development of cancer.

Visualizing The Data
The final piece of Underworlds' design strategy is to build beautiful visualizations in order to bring the data from project's dirtier aspects to light and make it accessible for the public. So far, they've published one visualization of the 58,309 viruses found in a single sample of sewage water. As you scroll through the website, the thousands of viruses filled the screen, represented by tiny, oscillating dots that give a sense of magnitude. Keep scrolling, and the dots organize into an interactive treemap of their type—nearly half of the viruses are unknown. The very small percentage that affect humans and animals are then highlighted.

Ratti says he's planning more visualizations as the project continues that are more focused on bringing sewage data together with demographic data to create an image of the microbiome of various neighborhoods and populations.

What's Next
Underworlds is currently undergoing a series of studies to fine tune the system's protocols. Soon, Ratti and Alm, an associate professor of biological engineering at MIT and a co-principal investigator of the project, say they'll start continually collecting samples in Cambridge, Boston, and Kuwait City in order to have points of comparison across distance, weather, and seasons. After pilot programs have been completed in those cities, Ratti and Alm say they'll be able to expand to more cities.

Ratti and Alm believe that the information that could be gleaned from sewage is so valuable that most cities will be mining data from it in the next 10 years.

The project comes at a time when cities are beginning to use sensors to collect data about the health of urban populations and infrastructures. Chicago's Array of Things, which had its first sensors installed last month, is aiming to use its data to study traffic flows, pollution, and weather. The Department of Transportation hosted a "Smart City" challenge and in June awarded $40 million to Cleveland, Ohio, to develop a network of autonomous vehicles and sensors. "Smart Cities Week," a conference for urban planners and government officials to discuss how to use technology in an urban context, just took place last month in Washington, D.C.

"An enormous mass of water moves in and out of our cities every day," says Alm. "Clean water is converted to sewage, leaving an imprint of nearly all human activities in the process. But we don’t yet understand how to infer those activities from sewage."

And if all goes according to plan, Underworlds will take us beneath the manhole, uncovering the (smelly) mysteries of human sewage in order to provide the data to improve public health.

[All Photos: MIT Senseable City Lab and Alm Lab]

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