Landfill gas monitoring network - development of wireless sensor network platforms

A wireless sensor network has been developed for the application of landfill gas monitoring, specifically sensing methane, carbon dioxide and extraction pressure. This collaborative work with the Irish Environmental Protection Agency has been motivated by the need to reduce greenhouse gas emissions as well as aiming to improve landfill gas management and utilisation. This paper describes the preliminary findings of an ongoing trial deployment of multiple sensing platforms on an active landfill facility; data has been acquired for nine months to date. The platforms have operated successfully despite adverse on-site conditions, with validity demonstrated by reasonably strong correlation with independent on-site measurements. The increased temporal and spatial resolution provided by distributed sensor platforms is discussed with regard to improving landfill gas management practice

Environmental gas sensing

Decomposing materials produce CO2 and CH4. This is true for landfill sites and anaerobic lagoons in waste water treatment plants. These are produced alongside other gasses such as H2S (hydrogen sulphide). The EPA are particularly interested in CO2 and CH4 because CO2 asphyxiates and CH4 is highly flammable (5-15% v/v CH4/air). There is a need for a monitoring platform so gas levels stay in safe regions

Screen printed electrochemical sensors for real-time sodium monitoring in sweat

We report on the preparation of disposable potentiometric sensor strips for monitoring sodium in sweat. We also present their integration in a microfluidic chip used to harvest sweat in-situ during exercise. The sensor-chip is integrated with a miniaturized electronic platform able to transmit data wirelessly in real time during a stationary cycling session in a controlled environment

Web-based monitoring of gas emissions from landfill sites using autonomous sensing platforms

Executive Summary Numerous initiatives that are policy driven by national, European and global agencies target the preservation of our environment, human society’s health and our ecology. Ireland’s EPA 2020 Vision outlines a mandate to prepare for the unavoidable impact of climate change, the reduction of greenhouse gas (GHG) emissions, the control of air-emissions standards, the sustainable use of resources and the holding to account of those who flout environmental laws. These strategies are echoed in the Europe 2020: Resource-efficient Europe Flagship Initiative, which also advocates the creation of new opportunities for economic growth and greater innovation. The promotion of research and technical development is central to each of these strategies – specifically the achievement of accurate environmental monitoring technologies that will inform policy-makers and effect change. This is described in the EPA Strategic Plan 2013–2015 as the provision of ‘high quality, targeted and timely environmental data, information and assessment to inform decision making at all levels’. Specific to landfills, the Environmental Protection Agency’s (EPA) Focus on Landfilling in Ireland stipulates the management of landfill gas to eliminate environmental harm and public nuisance, to promote energy generation where possible and to avoid liabilities in site closure and aftercare. It was in this context that the EPA STRIVE programme granted funding for this research project on developing autonomous sensor platforms for the real-time monitoring of gases generated in landfill facilities. Managing landfill gas is one of the crucial operations in a landfill facility, where gases (primarily methane [CH4] and carbon dioxide [CO2] generated from the decomposition of biodegradable waste) are extracted and combusted in a flare or preferably an engine (as biogas fuel). These gases, classified as greenhouse gases (GHGs), also pose localised hazards due to fire risk and asphyxiation, and are indicative of odorous nuisance compounds. Gas-monitoring on site is conducted to (i) ensure against gas migration into the local environment and to (ii) maintain the thorough gas extraction and optimum composition for combustion. This is becoming more relevant because of the numerous landfill closures brought by Europe-wide changes in waste-management policy. Even for landfills no longer actively receiving waste, substantial gas generation remains ongoing for years and even decades. Despite diminished financial resources and reduced manpower, management of this gas must be maintained. Traditionally, monitoring involves taking manual measurements using expensive handheld equipment and requiring laborious travel over difficult and expansive terrain. Consequently, it is conducted relatively infrequently – typically once a month. These issues can be addressed by adopting distributed continuous monitoring systems. These low-cost remotely deployable sensor platforms offer a valuable complementary service to operators and the EPA. They enable easier adherence to their licence criteria, the prevention of expensive remediation measures and the potential boost in revenue from increasing energy production through the use of biogas. Challenges arise in terms of achieving a long-term monitoring performance in a harsh environment while maintaining accuracy, reliability and cost-effectiveness. To meet these challenges, this project developed cost- effective autonomous sensor platforms to allow long- term continuous monitoring of gas composition (methane and carbon dioxide) and extraction pressure. The project’s work represents one of the only developments of autonomous sensor technology in this space; the few other market alternatives tend to be expensive or difficult to implement for remotely deployable continuous monitoring. Beyond the development of a platform technology, the challenge was to apply this technology to the adverse environmental conditions. The project delivered a total of 14 autonomous sensor platforms in deployments involving Irish landfill sites, a Scottish landfill site and a Brazilian wastewater treatment plant. The analysis and interpretation of acquired data, coupled with local meteorological data and on-site operational data, provided the translation from raw environmental data to meaningful conclusions that could inform decision-making. This report presents a number of case studies to illustrate this. Characteristics of site gas dynamics could be identified; for example, it was possible to show if excessive gas concentrations in a perimeter well could be resolved by increasing the flare extraction rate for a particular well. Furthermore, the potential for quantifying methane generation potential at distributed locations within the landfill was identified in addition to diagnosing the effectiveness of the extraction network – hence aiding in field-balancing and landfill gas utilisation. The extensive wealth of data enabled by this platform technology will help better-informed decision-making and improve operational practices in managing gas emissions. In landfills, this signifies alleviating gas migration with perimeter monitoring and enhancing flare/ engine operation by evaluating gas quality at distributed locations within the gas field. While landfilling is becoming outmoded as a waste-management process, the need for continuous monitoring will be relevant for many years to come. Indeed, a number of existing facilities are considering retrofitting engines because of the significant potential for additional landfill gas utilisation being identified by Sustainable Energy Authority Ireland in 2010. Furthermore, the technology’s low-cost and autonomous nature would benefit the hundreds of historical and legacy landfills if any were deemed to be problematic in terms of their environmental impact. Beyond landfills, this work pertains to other applications within the waste sector, as demonstrated by measuring emissions from wastewater treatment plant lagoons. With some further development, this technology could apply to efforts in dealing with climate change (e.g. in evaluating GHG inventories), where applications include managed peatlands (one case study is presented in this report and future efforts could also be targeted at carbon sinks/storage) and agriculture (Ireland’s greatest contributor to GHGs). Further scope could also be pursued in air-quality monitoring, particularly relevant at present with 2013 being dubbed the ‘Year of Air’ by European leaders. Throughout this project, the commercial prospect of this technology was affirmed with positive feedback from landfill operators, environmental regulators and private consultancies. Continual technical developments and refinements in mechanical/electronic design delivered a platform with expanded functionality and reduced price-point, thus becoming more viable for scaled-up deployments and commercial feasibility. Ultimately, this innovative development shows good promise as a high-potential commercial venture, with this work continuing under Enterprise Ireland’s Commercialisation Fund

Sensors for in-situ monitoring of eutrophication in marine environments

Accelerated eutrophication of marine ecosystems as a result of nutrient enrichment is a widespread problem within European marine margins. Eutrophication has several adverse effects on the marine ecosystem such as the formation of harmful algae blooms reduced water clarity and reduced oxygen levels. The reliable quantification of the causative nutrients is challenging due to the matrix within which they are held. Here we propose methods for the identification and optimisation of appropriate detection chemistries for phosphate, ammonia, nitrate and nitrite in marine matrices. The work presented is carried out as part of the COMMON SENSE FP7 European project. COMMON SENSE aims to provide a reliable sensing platform for in-situ measurements on key parameters relating to eutrophication. The nutrient sensor is based on a combination of microfluidic analytical systems, colorimetric reagent chemistry, low-cost LED-based optical detection, and wireless communications

Development of cost effective sensors for the in-situ monitoring of eutrophication

This work is carried out as part of the COMMON SENSE European FP7 project. The COMMON SENSE project aims to provide a reliable sensing platform for in-situ measurements on key marine water quality parameters relating to eutrophication, heavy metal contaminants, marine litter and underwater noise. The COMMON SENSE nutrient sensor is based on a combination of microfluidic analytical systems, colorimetric reagent chemistry, low-cost LED-based optical detection, and wireless communications. The reliable quantification of nutrients in marine environments is challenging due to the low concentration of these solutes in the ocean and the nature of the matrix in which they are held. Initial studies are focussed on validating a method for the sequential determination of nitrite and nitrate in marine environments. Coupled with the traditional well established Griess–Ilosvay reaction for the determination of nitrite, a vanadium chloride (VCl3) solution is used as the reducing agent. The method shows potential as an alternative to the toxic cadmium column for the reduction of NO3- to NO2- in marine water as results indicate that there are no apparent interferences from variances in salinity. The method was tested on a series of samples with varying salinities and sample matrices (costal, estuarine and freshwater), the method is low cost, reproducible and requires low volumes of sample and reagents

Non invasive detection of biological fluids: a new perspective in monitoring pH in saliva and sodium in sweat

The chemical composition of body fluids contains crucial information about the state of health of an individual. While many efforts have been already directed toward real time analysis of blood and urine, there is still a pressing need for new solutions to non-invasively monitor other fluids like saliva and sweat1. Towards this aim, the main technological challenge is the development of devices that are at the same time low-cost, minimally invasive and wearable, so that they could be used for in situ and real-time monitoring of physiological conditions2. For example, continuous recording of sodium levels in sweat could be an informative tool to assist clinicians in prescribing a more personalised treatment of diseases such as Cystic Fibrosis3 and in assessing athletes’ performances4. Similarly, the monitoring of pH levels in saliva provides valuable information for the treatment of pathologies where physiological mouth conditions are compromised, like in Gastroesophageal Reflux Disease (GERD)5. Ion Selective Electrodes (ISEs) are potentiometric sensors designed to detect specific ions in blood and saliva. Using dual-screen printed electrodes as substrates, we were able to reduce their production cost, improve reproducibility, and combine pH5 and sodium ISEs with solid contact reference electrodes. In our design, the sensors will be interfaced to two miniaturized potentiometric platforms (WIXEL for pH and Tyndall Mote for sodium detection) that were wirelessly connected to a base station. For pH measurements, the device will be accommodated into a gum shield. For sodium detection instead, we will use a microfluidic channel to convey sweat to the electrodes. The mote communication platform was adapted so that it could be worn on the upper shoulder through a fiber strip

Low cost autonomous sensing platforms for the direct determination of nutrients in water

There is a growing need for low cost, remote sensing systems which can be deployed in situ in sufficiently large numbers to ensure that data on key water quality parameters is readily available. The challenges facing this ideal of monitoring include the cost of these platforms and the inability to “deploy and forget” due to limited long term stability and maintenance requirements. 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 ammonia and nitrate in water and wastewater are being investigated. Our approach is to combine microfluidics with simplified colorimetric chemical assays; low cost LED/photodiode-based optical detection systems; and wireless communications. In order to drive down the cost of these devices, it is vital to keep the fluidic handling requirement as simple as possible, as multistage methods are expensive to implement as well as being less reliable in long-term deployments. Colorimetric methods for nitrate and ammonia have been modified eliminating several steps previously associated with the methods to facilitate their implementation into an autonomous platform, resulting in a rapid and simple measurement procedure

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