Development of Reusable Colorimetric Sensors for the Assessment of Sea Water Quality

Detecting water quality in our oceans has attracted much recent interest. Sensing the multitude of bacteria, chemicals and plastics, increasingly found polluting sea water, is important to both marine and human life. One of the main problems with ocean pollution is that it is mostly invisible.

The development of reusable colorimetric indicators to sense types of water pollution, has multiple end uses. This would act as a health and safety tool. The sensor may highlight the detrimental impact of water pollution.

A set of sensors would demonstrate how widespread various forms of marine pollution are globally, not just in the UK where some forms of ocean water testing are a legal requirement. The expected end use would be to attach the sensors to a wetsuit, monitoring the quality of the water. The sensor could be affiliated with organisations such as Surfers Against Sewage, linking with their 'Safer Seas Service' (Surfers Against Sewage, 2019) or utilised by sustainable surfing brands.

'Coastal areas and communities are some of the most vulnerable regions worldwide' (Scott & Rogers, 2018). Studying water quality in the Gulf of Maine, they found that surfers are an important stakeholder in ocean water quality. Their research found that 96% of the surfers included in the study were interested in the water quality at their local surf spot. This paper highlights the requirement for an improved method of communicating the dangers of poor water quality to surfers. Scott and Rogers (2017) also suggest that utilising the surfer community may be the best way to raise awareness of ocean pollution.

Milindanuth and Pisitsak demonstrated the advantages of a solid-state colorimetric sensor; 'including ease of handling, operational simplicity, and low cost, and provide qualitative and quantitative information without the use of expensive instruments' (Milindanuth & Pisitsak, 2018). Nanofibres are suitable for sensor applications on account of their ability to be highly porous with a large area-to-volume ratio. There are challenges in the production of nanofibres and the potential use of 'toxic organic solvents' (Milindanuth & Pisitsak, 2018). Piriya et al., (2017) identified colorimetric sensors based on their high sensitivity and selective response. Current research based on colorimetry 'is all about the miniaturization of size, cost, in-situ and without any additional instruments', (Piriya, et al., 2017). This highlights the relevance of this research in the current climate. Piriya et al., (2017) also discuss the importance of nanotechnology in current sensor technology.

AIMS
Development of a reusable strip of colorimetric sensors for the assessment of several ocean water quality indicators;
Identification of which water quality indicators are most suitable for the application;
Production of novel reusable water quality sensor technologies based on nanofibers and hydrogels;
Creation of reusable prototype strips of water quality sensors that change colour with exposure to a range of pollutants;
Comparison of the performance of the novel colorimetric sensors with conventional methods.

METHODOLOGY
Identify and classify current water quality testing methods.
Investigate and identify the most common types of ocean water pollution to be detected.
Apply reported colorimetric sensors for the detection of relevant pollutants.
Identify the most appropriate substrate, colorants and testing environments.
Prepare Simulated Sea Water (SSW) for repeatability testing.
Measure the colorimetric response to pollutants and the sensitivity of nanofibre- and hydrogel- based sensors.
Compare the response of the novel sensors to traditional methods of water quality assessment.

The project is related to the following EPSRC themes; Engineering, Physical Sciences, Global Uncertainties and Manufacturing the Future. In particular the research areas of Sensors and Instrumentation and Water Engineering.