Achieving UN Sustainable Development Goal 6 With Our Tryptophan Sensor

In the words of the UN: "Water is essential not only to health, but also to poverty reduction, food security, peace and human rights, ecosystems and education. Nevertheless, countries face growing challenges linked to water scarcity, water pollution, degraded water-related ecosystems and cooperation over transboundary water basins. Unless current rates of progress increase substantially, Goal 6 targets will not be met by 2030."

What is UN Sustainable Development Goal 6?

UN Sustainable Development Goal 6 (SDG 6 or Global Goal 6) is about “clean water and sanitation for all”. It is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015, with the official wording: “Ensure availability and sustainable management of water and sanitation for all.” The goal has eight targets to be achieved by at least 2030. Progress toward the targets will be measured by using eleven indicators.

The proportion of the global population using safely managed drinking water services increased from 61 per cent in 2000 to 71 per cent in 2017. Despite progress, 2.2 billion people around the world still lacked safely managed drinking water, including 785 million without basic drinking water. This explains the importance of UN Sustainable Development Goal 6. The population using safely managed sanitation services increased from 28 per cent in 2000 to 45 per cent in 2017. However, 4.2 billion people worldwide still lacked safely managed sanitation, including 2 billion who were without basic sanitation. Of these, 673 million people practised open defecation.

How is drinking water typically measured for UN Sustainable Development Goal 6?

Standard approaches to test water supplies have long used bacteriological indicators of faecal contamination, most commonly TTCs. This approach requires working with sterile equipment and testing that can take one or two days to return results, due to the necessity of culturing. The cumbersome nature of these tests limits the frequency of sampling, so contamination can be missed. Even if identified, lags of one or two days before results are returned mean that people may have already been exposed to the faecal contamination.

UN Sustainable Development Goal 6: “Ensure availability and sustainable management of water and sanitation for all”

Drinking water contaminated with faeces is still consumed by 1.8 billion people globally and there is a need for easy-to-use, rapid techniques to screen drinking water. Tryptophan-like fluorescence (TLF). Multiple studies have now shown that faecally contaminated drinking water sources have higher levels of TLF and that TLF is correlated with concentrations of thermotolerant coliforms, including E. coli

How James Sorensen’s New Study Relates to UN Sustainable Development Goal 6

The recent study led by James Sorensen of the British Geological Survey (BGS) using Chelsea Technologies’ Tryptophan sensors show how our technique exploiting the fluorescent properties of microbiological materials in water provides an easy-to-use method that is a more resilient indicator of the risk of faecal contamination to water supplies than thermotolerant coliform bacteria, known as TTCs, which have been the most common standard approach to water testing for decades. This makes UN Sustainable Development Goal 6 immediately more attainable, for in order to improve, you must measure first.

‘In situ fluorescence spectroscopy provides an instantaneous assessment of faecal contamination allowing rapid feedback to consumers to reduce their exposure to faecally contaminated drinking water. For example, in the UK, online fluorescence could minimise widespread boil alerts currently triggered when contaminated water is circulated and, potentially, consumed by thousands of people before there is any indication of contamination using standard approaches.’

Lead author James Sorensen, BGS

‘The ability to test in situ fluorescence as an indicator of faecal contamination risk in a wide range of environments and conditions has greatly improved both the evidence base for this method of water quality monitoring and our understanding of what fluorescence observed in water means.’

Co-author Prof Richard Taylor, UCL Geography

‘This robust, rapid method of monitoring the risk posed by faecal contamination has enormous implications in Uganda, not only for untreated water sources such as wells and springs, as it enables communities to respond rapidly to contamination events, but also for low-cost, continuous monitoring of piped water supplies.’

Co-author Dr Robinah Kulabako, Makerere University

The research, conducted by a collaborative team from the BGS, Makerere University in Uganda and UCL, examined changes in water quality over a 14-month period from 40 sources supplied by groundwater in the rapidly expanding town of Lukaya in southern Uganda. In this paper, Sorensen demonstrates that in-situ fluorescence spectroscopy is a more rapid and resilient indicator of faecal contamination risk in drinking water than faecal indicator organisms.

What is tryptophan-like fluorescence?

Tryptophan is an essential amino acid that fluoresces at an excitation wavelength of 280 nm and an emission wavelength of 350 nm. The term tryptophan-like fluorescence (TLF) is used because there are multiple compounds that can fluoresce at similar wavelengths. TLF occurs in high concentrations in human and animal waste and is a well-known indicator of wastewater in the environment. It is also known that E. coli cells directly emit TLF and also produce compounds, including tryptophan, that fluoresce in the TLF spectrum.

How does a tryptophan sensor detect sewage?

Tryptophan is an essential amino acid produced by all living things, and our multiple tryptophan case studies demonstrate that in situ Tryptophan-like fluorescence monitoring, using the Chelsea Technologies’ tryptophan sensors, can identify sewage pollution events in complex and heavily contaminated river systems, discern different water ‘types’ and pollution, provide information about the activity of the microbial population present, which is influenced by nutrient pollution (ie agricultural runoff), identify low levels of FDOM in rivers with little-no human impact and be used in a range of environments for investigating the fluorescence properties of natural waters, which applies to both environments which are heavily impacted by nutrients and pollution, and those which are low-nutrient in nature with little to no impacts from human-induced pollution.

Results from tryptophan case studies from India, Sweden and the UK
Results from tryptophan case studies from India, Sweden and the UK

UviLux tryptophan sensors

The compact design and low cost of Chelsea Technologies’ tryptophan sensors make them ideal for mass deployments, and low power consumption coupled with a wide choice of data outputs and anti-biofouling options allows for long-term remote deployments. Integration to realtime data display systems for management of assets with alarms means instant readings, no need to take samples back to lab – immediate problem identification as they occur in realtime, saving stock and assets.