Microfluidic analyser for pH in water and wastewater

The Microfluidic Analyser for pH and Chemical Oxygen Demand (MApCOD) project is the latest stage in the development of a microfluidic platform for autonomous monitoring of environmental water quality. pH measures the acidity or basicity of water. Most aquatic animals are adapted to a range of 6.5–8.0 (close to neutral, pH 7.0). Low pH can also allow toxic substances such as ammonia to become more available for uptake by aquatic plants and animals, greatly increasing their effective toxicity. pH is commonly measured in industrial and municipal wastewaters as well as in monitoring of drinking water, of surface waters such as rivers and lakes, and in many industrial processes. In this project pH is measured using a combination of pH indicators, optimised to give a colorimetric response over the pH range 4.0–10.0, which covers the range of pH values commonly encountered in monitoring of surface waters, drinking water and many wastewaters. Dual LEDs and a photodiode are used to measure light absorbance at appropriate wavelengths (430 and 570 nm). The responses of the two pH indicators are complementary, allowing a colorimetric response to be obtained over the pH range of interest

Next generation chemical sensors: detecting nitrate and ammonia in water

Monitoring and protecting the quality of environmental waters is of major concern today. Our ability to effectively monitor the aquatic environment is essential due to the increasing pressure on the environment from pollution, global climate change and the fact that water is an increasingly scarce natural resource. Microfluidic technology has potential as a solution to the increasing demand for environmental monitoring; leading to the development of compact autonomous instruments for in situ continuous monitoring of remote locations over long deployable lifetimes. The objective of this research is to produce autonomous chemical sensing platforms with a price performance index that creates a significant impact on the existing market focusing on a detection platform for nutrients. The goal is to integrate polymer actuators valves into the microfluidic chip, to drive down the overall cost

Next generation autonomous chemical sensors: low cost nutrient detection for water quality monitoring

Microfluidic technology has potential as a solution to the increasing demand for environmental monitoring; through minimization of reagents, standard solutions, and power consumption. These efforts will lead to the development of compact autonomous instruments for in situ continuous monitoring of remote locations over long deployable lifetimes. There is therefore a growing need for low cost, reliable systems which can be deployed in sufficient numbers to ensure that data on key water quality parameters is available at the appropriate geographic and temporal densities to allow stakeholders to make well-informed decisions on the management and protection of our environmental waters

Pressure-Induced Effects on the Structure of the FeSe Superconductor

A polycrystalline sample of FeSe, which adopts the tetragonal PbO-type structure (P4/nmm) at room temperature, has been prepared using solid state reaction. We have investigated pressure-induced structural changes in tetragonal FeSe at varying hydrostatic pressures up to 0.6 GPa in the orthorhombic (T = 50 K) and tetragonal (T = 190 K) phases using high resolution neutron powder diffraction. We report that the structure is quite compressible with a Bulk modulus around 31 GPa to 33 GPa and that the pressure response is anisotropic with a larger compressibility along the c-axis. Key bond angles of the SeFe4 pyramids and FeSe4 tetrahedra are also determined as a function of pressure

Next generation autonomous chemical sensors for environmental monitoring

Microfluidic technology has great potential as a solution to the increasing demand for environmental monitoring, by producing autonomous chemical sensing platforms at a price level that creates a significant impact on the existing market. The development of sensing platforms for ammonium, nitrate and nitrite in water and wastewater using colorimetric techniques are being investigated. Our approach is to combine microfluidic technology with colorimetric chemical assays; low cost LED/photodiode-based optical detection systems; and wireless communications, developing low cost systems which can be deployed for extended periods. The objectives of this project are: (i) to develop and optimise colorimetric detection methods for nitrate, nitrite and ammonia, and (ii) to integrate polymeric actuator valves into the microfluidic chip, significantly driving down the overall cost of the platform for a fully integrated, multi-target ‘matchbox’ analyser ready for field deployment. The colorimetric study of nitrite was performed using the Griess test, and an autonomous nitrite analyser has also been developed. The work described in this paper shows that this forms the basis of a highly sensitive, low cost, simple colorimetric technique that can be integrated into a field deployable platform. A simplified colorimetric technique for nitrate has also been established and optimised using chromotropic acid in the presence of concentrated sulphuric acid. The method shows great relevance as a linear range was achieved from 0-80mg/L NO3-. The kinetics, reproducibility, limit of detection and reagent stability was investigated. A blind test using real samples was performed and results showed excellent agreement to ion chromatography. The chromotropic method for nitrate determination has been demonstrated to be a direct, simple technique. It was also shown that it is possible to reduce the concentration of the sulphuric acid used in the assay, reducing risk factors and component cost while maximising the lifetime of the system. A colorimetric method for the determination of ammonium was also investigated. The reagent cocktail includes a variation on the Berthelot method which employs salicylic acid instead of phenol, thereby eliminating a toxic and unstable reagent component. The intense colour generated is detected at a wavelength of 630nm. Results for the direct determination of nitrite and ammonia achieved also suggest that these may be suitable for integration into a similar field deployable platform to that of a phosphate monitoring platform which was previously developed1. Results from recent deployments of the phosphate platform in situ at Broadmeadow Water Estuary, Co. Dublin, Ireland, and at a constructed wetlands wastewater treatment system at Glaslough, Co. Monaghan, Ireland from May to June 2012 are also presented

A new LED-LED portable CO2 gas sensor based on an interchangeable membrane system for industrial applications

A new system for CO2 measurement (0-100%) by based on a paired emitter-detector diode arrangement as a colorimetric detection system is described. Two different configurations were tested: configuration 1 (an opposite side configuration) where a secondary inner-filter effect accounts for CO2 sensitivity. This configuration involves the absorption of the phosphorescence emitted from a CO2-insensitive luminophore by an acid-base indicator and configuration 2 wherein the membrane containing the luminophore is removed, simplifying the sensing membrane that now only contains the acid-base indicator. In addition, two different instrumental configurations have been studied, using a paired emitter-detector diode system, consisting of two LEDs wherein one is used as the light source (emitter) and the other is used in reverse bias mode as the light detector. The first configuration uses a green LED as emitter and a red LED as detector, whereas in the second case two identical red LEDs are used as emitter and detector. The system was characterised in terms of sensitivity, dynamic response, reproducibility, stability and temperature influence. We found that configuration 2 presented a better CO2 response in terms of sensitivity

The use of exergy analysis to benchmark the resource efficiency of municipal waste water treatment plants in Ireland

Exergy Analysis has been identified in the literature as a powerful tool to benchmark the resource efficiency of thermal systems. The exergy approach provides a rational basis for process optimisation, where, in theory, the processes with the greatest exergy destruction represent the greatest energy efficiency opportunities. Exergy analysis of a Waste Water Treatment Plant (WWTP) has been performed. In addition, two separate reference environments for WWTPs are defined based on plant location. Biological oxygen demand was identified as the most useful parameter when calculating the chemical exergy of organic matter in waste water. The results of this study indicate that organic matter is the principal contributor to chemical exergy values and that exergy analysis is a useful approach to identify inefficient processes within a WWTP

Integrated flow analysis platform for the direct detection of nitrate in water using a simplified chromotropic acid method

This work describes the first use of a direct nitrate analyser using chromotropic acid. A simplified chromotropic acid method eliminating several steps previously associated with this method is employed in the platform. In a sulphuric acid medium, chromotropic acid reacts with nitrate ions and produces a characteristic yellow colour associated with an absorbance band in the visible region (430 nm).The modified method allows for nitrate determination over the linear range 0.9–80 mg/L nitrate with a limit of detection of 0.73 mg/L nitrate. Validation was achieved by analysing water samples from various sources including groundwater, trade effluent and drinking water by the modified method and by ion chromatography. The method was implemented on a flow analysis platform incorporating a paired emitter–detector diode (PEDD) as the optical detector. An excellent correlation coefficient of 0.993 was obtained between the modified method and ion chromatography. The modified chromotropic acid method represents a rapid, simple, low cost technique for the direct determination of nitrate in water