Protecting our water

18 September 2019

In recognition of World Water Monitoring Day, 18th September, we look a two developments in the area of water purification that are helping to provide safe water quickly and inexpensively.

Muriel Cozier

Water is a resource very easily taken for granted, particularly in the world’s developed nations. As a reminder of how important clean and drinkable water is, along with functioning waterways, today’s World Water Monitoring Day (18th September) is encouraging local communities around the world to test and maintain their water supplies to ensure it is safe for drinking, swimming, fishing and farming. Today we look at two avenues of research to protect our water. 

Photocatalysis route to purified water

Waterborne diseases and epidemics caused by pathogens such as fungi, viruses and bacteria are a major threat to human health, particularly in developing countries where 80% of illnesses are estimated to be caused by waterborne pathogens. One means of treating water, that is receiving growing attention, is photocatalysis based on two-dimensional nanomaterials. A review in SCI’s Journal of Chemical Technology and Biotechnology looks at five categories of 2D nanomaterials: graphene, graphitic carbon nitride, 2D metal oxides and metallates, metal oxyhalides and transition metal dichalcogenides, which are used for the photocatalytic inactivation of pathogens.

These 2D nanomaterials have several advantages over the more widely applied methods of chlorination and ozonation where the active oxidizing agents, chlorine and ozone, either cause harmful disinfection by-products or are invalid to specific biohazards that are naturally resistant to commonly used water treatment chemicals. In addition, UV irradiation, a physical disinfection technology, is not suitable for certain kinds of microbes and has the added issue of high energy consumption.

Research is focusing on more efficient use of sunlight, with this avenue of pathogen removal showing great promise with advantages over the traditional methods including savings in energy, enhanced stability, and broad capability against a wide range of microbial pathogens.

Improving sensitivity for Pb2+detection

Owing to its widespread use, easy accumulation and difficult biodegradation, lead has been identified as one of the top ten chemicals of major public health concern by the World Health Organization. Additionally, the Centers for Disease Control and Prevention indicate that there is no established safe level of lead exposure.

Detection of lead in water can be carried out using several methods which require expensive equipment, professional operation and complicated sample pretreatment. The challenge is, therefore to create a simple and direct method for detection of lead.

The use of Deoxyribozymes (DNAzymes) has been found to be an excellent route to detect lead. DNAzymes are a variety of unique DNA sequences selected through repeated in vitro screening that exhibit high enzymatic and catalytic activities for specific substrates. With unprecedented advantages such as excellent performance, calorimetric biosensors based on DNAzymes provide a convenient and selective way to detect lead ion.

However, improving sensitivity is the challenge which has been improved with the use of synthetic beads modified with enzyme strand DNAzyme. Under optimized reaction conditions, the magnetic nano-DNAzyme had a quantitative detection range from 102 to 108pmol L-1. Prior to this, levels were only nmol L-1.  In addition, it was highly selective for Pb2+ over other metal ions with an assay time of less than one hour. Importantly the magnetic nano-DNAzyme platform was demonstrated to work well in direct Pb2+ detection in real water samples.

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