Collaborative research by City, University of London and the Indian Institute of Science is using advanced photonics to detect contamination in India’s watercourses. As Isabella Kaminski reports, this pioneering work could have widespread benefits for India and beyond.

Many parts of the world experience problems with water quality, but few more so than India. Its poor infrastructure, large and fast-growing population and complex cultural relationship with rivers mean that many watercourses are laden with pollution and pathogens. India was a low performer on the University of North Carolina’s Water, Sanitation and Hygiene (WASH) Performance Index 2015, ranked 93 of just over one hundred countries. This is a serious, direct health risk for the people that rely on the country’s water supplies and causes further problems down the line as the health of natural ecosystems decline.

But there could be light on the horizon due to an ambitious collaborative research project employing City’s expertise in advanced photonics technologies and synthetic chemistry.

In 2017, City, University of London’s Professor of Photonics, Professor Azizur Rahman and the Indian Institute of Science’s Professor Sundarrajan Asokan won a combined £500,000 research grant from the India-UK Water Quality Programme to develop a novel system of sensors to detect contaminants in water bodies.

The programme, funded by the UK’s Natural Environment Research Council (NERC) and the Indian Government’s Department of Science & Technology, supports novel research to improve understanding of the sources, transport and fate of pollutants in water and to determine the risks they pose to people and the environment.

Professors Rahman and Asokan’s project, entitled ‘Innovative low-cost optical sensor platforms for water quality monitoring’, will contribute to this by developing optical sensors that detect problems with water more accurately, quickly and cheaply than existing systems by using the emerging technology of ‘guided wave photonics’. It is also supported by the Newton-Bhabha Fund, named after the famous Indian scientist Homi Jehangir Bhabha, who played an important part in developing quantum theory.

Professor Ken Grattan OBE FREng (left) was a co-investigator on the project, which was led by Professor Azizur Rahman (the world’s leading academic in photonics modelling, pictured right) and the Indian Institute of Science’s Professor Sundarrajan Asokan.

The team has an excellent pedigree for the research, which is important because this is a multidisciplinary job requiring a wide variety of skills and expertise. Professor Rahman of City’s School of Mathematics, Computer Science & Engineering is the world’s leading academic in photonics modelling. Since receiving his BSc and MSc degrees in Electrical Engineering with distinction from Bangladesh University of Engineering and Technology during the 1970s, he has published more than 500 papers, received over £10 million in research funds and coordinated numerous funded projects across India and other countries.

His latest work has focused on the development of the next generation of optical sensors using nanotechnology, such as microstructured optical fibres, nanofibres, silicon slot guides and microresonators. Last year he was shortlisted for the prestigious Newton Prize [see boxed text opposite] for work on sensor technology in Malaysia.

Professor Asokan leads the optical sensor research group at the Indian Institute of Science in Bangalore, which has special expertise in nanotechnology, material characterisation and computing and a very active photonics group spread over many departments. He is the founder of Openwater.in, a water treatment company in India spun off his academic department, so he brings direct and relevant industrial experience to the consortium.

They will work alongside co-investigator Professor Kenneth Grattan OBE FREng, George Daniels Professor of Scientific Instrumentation at the Royal Academy of Engineering and Dean of the City Graduate School, who has a significant international reputation in the field of sensors and instrumentation and has published several papers on water quality monitoring.

Together the team has worked with an impressive array of organisations including Serco, Network Rail, Home Office, UK Border Agency, Arup, Fiat, BAE Systems and Amey Consulting. They met in India in May and will work together for at least the next three years. “Work on some parts has already begun,” says Professor Asokan. “It will give us a good opportunity to add the work of two complementary groups and make a very successful project.”

Professor Rahman explains that the first part of the project is basic optical design. That is, designing optical sensors – sensors that convert light rays into electronic signals – that can detect specific substances in water and relay them back to a central control point.

The sensors will use sophisticated specialist coated fibre Bragg grating technologies (a special type of reflector constructed in a short segment of optical fibre that only reflects particular wavelengths of light), as well as exploring the potential for nanofibres and plasmonic evanescent sensing to detect a range of different contaminants, be it physical, chemical or biological. “For each specific thing we are sensing, we need to work with, say, chemists or biologists in that area”, explains Professor Rahman. “But ultimately we want to see how the presence of something we want to detect changes the optical characteristics of our device.”

A young girl drinks from a reservoir in Khichan, India.

These sensors will be attached to optical fibres, the same sort as those used in modern internet connections, because they are cheap, have an extremely high data rate and extremely low loss. “An optical sensor can be ten, twenty miles away and you can send a signal which can come back with minimum loss,” says Professor Rahman.

Professor Rahman explains that he is experienced in the more theoretical work of design and optimisation, while Professors Grattan and Asokan have a more experimental leaning. “I have worked mostly on optical modelling and there are some sensors that are more advanced in theory,” he says. “Say you’re making a big dam and you’re pouring hundreds of tonnes of concrete and you want to find the temperature as it’s settling down. So you can have hundreds of thermal optical sensors measuring the temperature at different places and they’re sending signals. That we have done. I have also worked on a theoretical design of optical sensors for biosensing. We have published many papers on this.”

Professor Grattan, meanwhile, has long worked on developing optical sensors for detecting temperature and physical measurements. For example, he has worked with City’s Department of Civil Engineering to develop sensors that detect deflections in a bridge if it comes under too heavy a load. And he has worked on a project putting hundreds of sensors on a ship’s propeller to detect stress at different locations.

Since the team has already developed good temperature, pressure and humidity sensors, it decided to narrow this project to key targets, including biological pathogens such as E coli and cholera, chemical pollution such as arsenic, mercury and copper, as well as pesticides. “We said let’s focus on what is important for India,” says Professor Rahman. “So arsenic, for example, is a critical issue, particularly in West Bengal. You also have the leather industry which uses chromium so you get chromium contamination and biopathogens like cholera and typhoid across the country. So with arsenic, for example, we would look and say ‘what sort of polymer would react only with that, so the presence of other things should not affect it?’”

An optical fibre humidity and temperature sensor designed for use in a highly acidic sewer environment.
Optical fibre chemical sensors developed in the laboratory at City.

The next step is to develop integrated systems that enable the information from a whole series of sensors to be relayed to a central control point without being confused. The idea is that many sensors will be ‘multiplexed’ or strung along a single optical fibre sending ‘guided wave’ signals back to a central control unit. This could vary from a couple of sensors to potentially hundreds; the team has already used a network of more than 330 optical sensors in single acoustic sensing system.

“I could have ten different sensors – one for chromium, one for arsenic, et cetera – on the same sections of an optical fibre,” says Professor Rahman. “We’re talking millimetres long. Each is sensing a different contaminant, but using guided wave photonics, each of these uses a different wavelength, so the signals don’t interact and you can tell which one is sensing the presence of the target you want to detect.”

Professor Rahman says the sensors will be a significant improvement on existing systems for monitoring water quality, which usually rely on electrical feedback or chemical and biological processing. They will be small, light and fast, relaying reliable information directly to the control panel. Chemical and biological analysis can take hours or days, may require a larger sample and have a potentially larger error rate, while electronic cables can be dangerous to use in some places, such as coal or gas fields. This means problems in water supplies can be spotted much quicker, even in remote villages, providing support when and where it is most acutely needed. It also satisfies growing demand from citizens for real-time information about the water they are drinking.

Once the design work has been done, the sensors will be tested in the lab. The Indian Institute of Science’s Department of Civil Engineering has an advanced hydrology laboratory with a complex network of water supply systems where particular substances can be injected and monitored. The team hopes to be testing its sensors there in a couple of years’ time.

The next step might be to test out the sensors in a real-life situation
but, as Professor Rahman points out, this is tricky; you can’t add arsenic to a public watercourse so you are at the whim of what may or may not be there. One potential location is West Bengal where there is a serious arsenic problem. The arsenic occurs naturally deep in groundwater, but this is increasingly being tapped for agricultural use, so concentrating it in human drinking supplies.

The research team will then work alongside key stakeholders, including the Bangalore Water Supply and Sewerage Board which has agreed to test and evaluate the systems being developed. Bangalore, which is known as India’s Silicon Valley, does not have a particular problem with arsenic but does have serious water problems of its own, including the dumping of waste (including electronic waste) and untreated sewage into watercourses, which most recently has led to some of its famous lakes spectacularly catching fire.

Investment in infrastructure research is very expensive, particularly in the cutting-edge science and engineering that has allowed many of the most exciting developments in photonics to occur. So while some companies have already used real-time remote monitoring systems for measuring water quality, this is the first time such systems will be developed using guided-wave optical approaches. Professor Rahman says that in the future, advanced sensors and techniques could be developed to expand the system to emerging pollutants, such as insecticides, fertilisers, antibiotics and hormonal contraceptives. “We didn’t want to start with 20 things,” says Professor Rahman. “We wanted to show that some of the heavy metals and some biopathogens are possible and then we’ll look at others.”

Reagents used to make functionalised polymers for sensor coatings.

He says that following the project, if someone wanted to develop a sensor for another metalloid or heavy metal, it might have a similar chemistry to arsenic and so it would be quicker to develop a specific sensor for it. New groups of substances, such as insecticides, could also be achieved but would take longer.

Another future development, says Professor Rahman, would be to use silicon waveguides instead of optical ones because they would be even cheaper if the technology is developed on a larger scale. But that is for much further down the line.

While the project has obvious benefits for India, it could be useful in many other places too. “If this can be developed in India it can be developed in many other third-world countries, or even in the UK,” says Professor Rahman. “Although cholera is not common, there are other contaminants. That area could be developed with the knowledge we’ve gained.”

The work also has a positive secondary benefit to the UK. Photonics and biotechnology are hot topics at the moment, having been identified by the European Union as two of the six Key Enabling Technologies that will shape our world in the 21st century and provide major employment opportunities and economic growth. And while photonics is already key to crucial aspects of technological development, such as the internet, lighting, displays and optical communications systems, there is plenty of scope for further development. “If it can be developed for other countries and there is a big market, then UK industry can really get involved,” says Professor Rahman.

Using optical sensors to detect landslides

In 2017, Professor Rahman was shortlisted for the prestigious Newton Prize for his work developing optical rain and pressure sensors to provide an early warning system of potential landslides and ground movements in Malaysia. Malaysia has a regular and serious problem with landslides, which often kill people and devastate homes and communities.

Professor Rahman’s department, together with the Photonics Research Centre at the University of Malaya in Kuala Lumpur, created a lightweight package of sensors that used little battery power but were robust enough for use in the country’s demanding environment. They enabled remote monitoring of rain-soaked soils during the increasingly heavy monsoon seasons that are a precursor to landslides, providing predictions about areas at risk to inform the decisions of policymakers.

The project was financed by the Newton-Ungku Omar Fund (which promotes science, technology and innovation collaborations between Britain and Malaysia) and was partnered with the British Council and the Malaysian Industry-Government Group for High Technology.

The project also organised workshops for academics and industry representatives from all over Malaysia, helping SMEs work in this field.