Water Quality Biosensor

Water Quality Biosensors

With the growing concern over water scarcity and pollution, the ability to continuously monitor and analyze the composition of water becomes vital. Water is an essential element in the production of food, and tracking usage could help mitigate the risks of pollution in bodies of water and ensure that water is safe to consume. Further, water quality degradation can pose severe threats to public health, agricultural and industrial production, as well as ecological functions and biodiversity.

Instead of relying on traditional sensors, emerging research has shown that monitoring water quality could be achieved by natural microbes and enzymes. These biosensors could be engineered to produce a chemical reaction, emit light, or even sound when exposed to a toxin. Additionally, they could be used to monitor community drinking water, check water quality in water treatment discharge as well as monitor hard-to-detect pharmaceuticals and bioactive organic compounds.

We Now Consider Five Emerging Water Quality Biosensors:

• Graphene Nanosensor

  Researchers at Iowa State University have developed a graphene sensor that can detect contaminants as small as 0.6 nanometers in length, and thus identify organophosphates such as pesticides at levels significantly under US Environmental Protection Agency (EPA) recommendations. According to the project leader Dr. Jonathan Claussen, this is an inexpensive way to detect pathogens and other contaminants in not just water, but also soil and even in Livestock Monitoring.

• Bacterial Sensing

  Researchers have used CRISPR/Cas9 techniques to engineer bacteria to glow in certain pigments when they contact certain chemicals. Color-coded unharmful bacteria could therefore be engineered to react to pollution events in water, food, or other products. As a biological alternative, it is much faster, cheaper and ecological than traditional chemical tests. Contaminated water or food could be immediately spotted in any part of the chain, and be disposed of or cleaned accordingly. Microfluidic systems could maintain a constant, contained population of sensor bacteria able to be implemented inside factories, warehouses, and water systems. Overall, this device represents a novel low-cost system for long-term detection of bacteria in a water supply and other applications.

• Paper-based Biosensors

  Cellulose, paper-based biosensors can be used for the detection of a range of analytes, including proteins, pathogens, and chemical contaminants such as pathogens, pharmaceuticals, and heavy metals. These microfluidic paper-based analytical devices (μPADs) can be made from paper such as cellulose chromatography paper. Cellulose is a hydrophilic polymer, which makes paper substrate permeable to aqueous liquids. A chemically patterned microfluidic paper-based analytical device (C-µPAD) is developed to create fluidic networks by forming hydrophobic barriers using chemical vapor deposition (CVD) of trichlorosilane (TCS) on a chromatography paper. By controlling temperature, pattern size, and CVD duration, optimal conditions were determined by characterizing hydrophobicity, spreading patterns, and flow behavior on various sized fluidic patterns. An alternative method involves impregnating paper with a powdered growth medium to create a 3D petri dish. After adding a drop of water to the platform surface, colored spots appear in the presence of harmful contaminants, allowing multiple bioassays to be conducted simultaneously. Some tests even offer a second phase by taking a picture of the sample with a mobile application that automatically counts the number of present bacterial colonies and providing deeper insights into the results. As the results are given in real-time, a laboratory is not required to perform further tests, thus helping communities lacking proper infrastructure and resources to have access to testing and evaluation methods.

• Cell-based Biosensors

  Cell-based biosensors use living cells to recognize elements or contaminants with high sensitivity, selectivity, and rapid response. Researchers from University of Tübingen have developed cell-based biosensors that can detect two types of pharmaceutical substances, beta-blockers and non-steroidal anti-inflammatory drugs (NSAIDs) in water. These substances are difficult to remove and are known to cause health problems in fish and reptiles. The cell-based biosensors can detect the binding of such substances to their target molecules (receptors) in treated wastewater in real-time. After the biosensor cell lines are exposed to drugs in water samples, a fluorescence signal appears within seconds, detecting the effect of chemicals in the cell in real-time. Cell biosensors can be applied to detect herbicides using non-engineered algae (such as Chlorella) to assess any variation in chlorophyll fluorescence. This technology can also detect Chemical Oxygen Demand (COD) in wastewater by measuring changes in bioluminescence response.

• Microbial Fuel Cell (MFC) Biosensor

  Since the 1990s, Biochemical Oxygen Demand (BOD) biosensors have been the most popular sensing device for water and wastewater quality sensing. However, this analysis requires five days to complete. The development of Microbial Fuel Cells, devices that directly convert chemical energy contained in energy matter into electrical currents via the metabolic processes of microorganisms, has shown promising potential for water quality monitoring. Recently, an off-the-grid autonomous biosensor was developed for water quality monitoring to test chemical and biological oxygen demand and was the first report of a self-powered, autonomous device, developed for online water quality monitoring. The self-powered floating sensor was developed from microbial fuel cells and was able to switch on visual and sound cues when exposed to urine.

  Researchers at the University of Bath have fabricated the first paper microbial fuel cell (pMFC) by screen-printing carbon electrodes onto a single sheet of paper. This technique is low-cost, simple, and effective, and differs from paper-based biosensors in that it does not require a potentiostat or therefore an AC power supply, and is thus lightweight and highly portable. The research showed pMFC to be effective as a shock sensor for formaldehyde in water.

Future Perspectives

Concerns over sustainability have been raised, since spreading biosensors in bodies of water could have unknown effects on ecosystems. To solve this, scientists propose a two-step approach. First, by using less precise methods to detect if the water shows signs of contamination, then, on an as-needed basis, deploy biosensors to more accurately pinpoint the type or source of contamination. Specific aquatic species such as fish sensitively respond to the presence of a variety of contaminants and could be monitored as a pre-screening step.

Water quality biosensors could save lives, both human and aquatic, by providing early warning signals regarding pollutants. Likely to have applications in areas such as aquaponics, hydroponics, and aquaculture, water quality biosensors will become a critical system asset in food production in aqueous environments. Monitoring can influence decision-making based on real-time data so that producers can benefit from a more precise route to market. One of the challenges for commercial deployment of this technology is making it more robust, with affordable sensor technologies and understanding the effects of biosensors on ecosystems.

Apart from efforts to implement an integrated bulk analysis system, initiatives for the use of different types of sensors are already commercial on a personal level. Increased development can lower the cost, opening up use on a larger scale, especially in areas lacking basic sanitation.