Managing NOx gas emissions from combustion.

26/09/2019
Pollution can only be managed effectively if it is monitored effectively.

James Clements

As political pressure increases to limit the emissions of the oxides of nitrogen, James Clements, Managing Director of the Signal Group, explains how the latest advances in monitoring technology can help.

Nitrogen and oxygen are the two main components of atmospheric air, but they do not react at ambient temperature. However, in the heat of combustion, such as in a vehicle engine or within an industrial furnace or process, the gases react to form nitrogen oxide (NO) and nitrogen dioxide (NO2). This is an important consideration for the manufacturers of combustion equipment because emissions of these gases (collectively known as NOx) have serious health and environmental effects, and are therefore tightly regulated.

Nitrogen dioxide gas is a major pollutant in ambient air, responsible for large numbers of premature deaths, particularly in urban areas where vehicular emissions accumulate. NO2 also contributes to global warming and in some circumstances can cause acid rain. A wide range of regulations therefore exist to limit NOx emissions from combustion sources ranging from domestic wood burners to cars, and from industrial furnaces and generators to power stations. The developers of engines and furnaces therefore focus attention on the NOx emissions of their designs, and the operators of this equipment are generally required to undertake emissions monitoring to demonstrate regulatory compliance.

The role of monitoring in NOx reduction
NOx emissions can be reduced by:

  • reducing peak combustion temperature
  • reducing residence time at the peak temperature
  • chemical reduction of NOx during the combustion process
  • reducing nitrogen in the combustion process

These primary NOx reduction methods frequently involve extra cost or lower combustion efficiency, so NOx measurements are essential for the optimisation of engine/boiler efficiency. Secondary NOx reduction measures are possible by either chemical reduction or sorption/neutralisation. Naturally, the effects of these measures also require accurate emissions monitoring and control.

Choosing a NOx analyser
In practice, the main methods employed for the measurement of NOx are infrared, chemiluminescence and electrochemical. However, emissions monitoring standards are mostly performance based, so users need to select analysers that are able to demonstrate the required performance specification.

Rack Analyser

Infrared analysers measure the absorption of an emitted infrared light source through a gas sample. In Signal’s PULSAR range, Gas Filter Correlation technology enables the measurement of just the gas or gases of interest, with negligible interference from other gases and water vapour. Alternatively, FTIR enables the simultaneous speciation of many different species, including NO and NO2, but it is costly and in common with other infrared methods, is significantly less sensitive than CLD.

Electrochemical sensors are low cost and generally offer lower levels of performance. Gas diffuses into the sensor where it is oxidised or reduced, which results in a current that is limited by diffusion, so the output from these sensors is proportional to the gas concentration. However, users should take into consideration potential cross-sensitivities, as well as rigorous calibration requirements and limited sensor longevity.

The chemiluminescence detector (CLD) method of measuring NO is based on the use of a controlled amount of Ozone (O3) coming into contact with the sample containing NO inside a light sealed chamber. This chamber has a photomultiplier fitted so that it measures the photons given off by the reaction that takes place between NO and O3.

NO is oxidised by the O3 to become NO2 and photons are released as a part of the reaction. This chemiluminescence only occurs with NO, so in order to measure NO2 it is necessary to first convert it to NO. The NO2 value is added to the NO reading and this is equates to the NOx value.

Most of the oxides of nitrogen coming directly from combustion processes are NO, but much of it is further oxidised to NO2 as the NO mixes with air (which is 20.9% Oxygen). For regulatory monitoring, NO2 is generally the required measurement parameter, but for combustion research and development NOx is the common measurand. Consequently, chemiluminescence is the preferred measurement method for development engineers at manufacturer laboratories working on new technologies to reduce NOx emissions in the combustion of fossil fuels. For regulatory compliance monitoring, NDIR (Non-Dispersive Infrared) is more commonly employed.

Typical applications for CLD analysers therefore include the development and manufacture of gas turbines, large stationary diesel engines, large combustion plant process boilers, domestic gas water heaters and gas-fired factory space heaters, as well as combustion research, catalyst efficiency, NOx reduction, bus engine retrofits, truck NOx selective catalytic reduction development and any other manufacturing process which burns fossil fuels.

These applications require better accuracy than regulatory compliance because savings in the choice of analyser are negligible in comparison with the market benefits of developing engines and furnaces with superior efficiency and better, cleaner emissions.

Signal Group always offers non-heated, non-vacuum CLD analysers for combined cycle gas turbine (CCGT) power stations because these stations emit lower than average NOx levels. NDIR analysers typically have a range of 100ppm whereas CLD analysers are much more sensitive, with a lower range of 10ppm. Combustion processes operating with de-NOX equipment will need this superior level of sensitivity.

There is a high proportion of NO2 in the emissions of CCGT plants because they run with high levels of air in the combustion process, so it is necessary to convert NO2 to NO prior to analysis. Most CLD analysers are supplied with converters, but NDIR analysers are not so these are normally installed separately when NDIR is used.

In the USA, permitted levels for NOx are low, and many plants employ de-NOx equipment, so CLD analysers are often preferred. In Europe, the permitted levels are coming down, but there are fewer CCGT Large Plant operators, and in other markets such as India and China, permitted NOx emissions are significantly higher and NDIR is therefore more commonly employed.

In England, the Environment Agency requires continuous emissions monitors (CEMS) to have a range no more than 2.5 times the permitted NOx level, so as a manufacturer of both CLD and NDIR analysers, this can be a determining factor for Signal Group when deciding which analysers to recommend. The UK has a large number of CCGT power plants in operation and Signal Group has a high number of installed CEMS at these sites, but very few new plants have been built in recent years.

New NOx analysis technology
Signal Group recently announced the launch of the QUASAR Series IV gas analysers which employ CLD for the continuous measurement of NOx, Nitric Oxide, Nitrogen Dioxide or Ammonia in applications such as engine emissions, combustion studies, process monitoring, CEMS and gas production.

Chemiluminescence Analyser

The QUASAR instruments exploit the advantages of heated vacuum chemiluminescence, offering higher sensitivity with minimal quenching effects, and a heated reaction chamber that facilitates the processing of hot, wet sample gases without condensation. Signal’s vacuum technology improves the signal to noise ratio, and a fast response time makes it ideal for real-time reporting applications. However, a non-vacuum version is available for trace NOx measurements such as RDE (Real-world Driving Emissions) on-board vehicle testing, for which a 24VDC version is available.

A key feature of these latest instruments is the communications flexibility – all of the new Series IV instruments are compatible with 3G, 4G, GPRS, Bluetooth, Wifi and satellite communications; each instrument has its own IP address and runs on Windows software. This provides users with simple, secure access to their analyzers at any time, from almost anywhere.

In summary, it is clear that the choice of analyser is dictated by the application, so it is important to discuss this with appropriate suppliers/manufacturers. However, with the latest instruments, Signal’s customers can look forward to monitoring systems that are much more flexible and easier to operate. This will improve NOx reduction measures, and thereby help to protect both human health and the environment.


Gas sensing in the purification process of drinking water.

28/08/2019

The processing of clean and safe drinking water is an international issue. Estimates suggest that, if no further improvements are made to the availability of safe water sources, over 135 million people will die from potentially preventable diseases by 2020.1

Even within Britain, water purification and treatment is big business, with £2.1 billion (€2.37b 28/8/2019) being invested by utilities in England and Wales between 2013 and 2014.2 Water purification consists of removing undesirable chemicals, bacteria, solids and gases from water, so that it is safe to drink and use. The standard of purified water varies depending on the intended purpose of the water, for example, water used for fine chemical synthesis may need to be ‘cleaner’ i.e. have fewer chemicals present, than is tolerable for drinking water, the most common use of purified water.

Purification Process
The process of water purification involves many different steps. The first step, once the water has been piped to the purification plant, is filtering to remove any large debris and solids. There also needs to be an assessment of how dirty the water is to design the purification strategy. Some pretreatment may also occur using carbon dioxide to change pH levels and clean up the wastewater to some extent. Here, gas monitors are used to ensure the correct gas levels are being added to the water and unsafe levels of the gas do not build up.

The following steps include chemical treatment, an filtration to remove dissolved ionic compounds.3 Then, disinfection can occur to kill any remaining bacteria or viruses, with additional chemicals being added to provide longer lasting protection.4 At all stages, the water quality must be constantly monitored. This is to ensure that any pollutants have been adequately removed and the water is safe for its intended purpose.

In-line gas monitors are often used as part of the water treatment process as a way of monitoring total organic carbon (TOC) content. Carbon content in water can arise from a variety of sources, including bacteria, plastics or sediments that have not been successfully removed by the filtration process.5 TOC is a useful proxy for water cleanliness as it covers contamination from a variety of different sources.

To use non-dispersive infrared (NDIR) gas monitors to analyze the TOC content of water, a few extra chemical reactions and vaporization need to be performed to cause the release of CO2 gas. The resulting concentration of gas can then be used as a proxy of TOC levels.6 This then provides a metric than can be used to determine whether additional purification is required or that the water is safe for use.

Need for Gas Monitors
NDIR gas sensors can be used as both a safety device in the water purification process as carbon dioxide, methane, and carbon monoxide are some of the key gases produced during the treatment process. 5 The other key use is for analysis of TOC content as a way of checking for water purity.7 NDIR sensors are particularly well suited for TOC analysis as carbon dioxide absorbs infrared light very strongly. This means that even very low carbon dioxide concentrations can be detected easily, making it a highly sensitive measurement approach.6 Other hydrocarbon gases can also easily be detected in this way, making NDIR sensors a highly flexible, adaptable approach to monitoring TOC and dissolved gas content in water.

Sensor Solutions
The need for constant gas monitoring to guide and refine the purification process during wastewater treatment means water purification plants need permanent, easy to install sensors that are capable of continual online monitoring. One of the most effective ways of doing this is having OEM sensors that can be integrated into existing water testing equipment to also provide information on water purity.

These reasons are why Edinburgh Sensors range of nondispersive infrared (NDIR) gas sensors are the perfect solution for water purification plants. NDIR sensors are highly robust with excellent sensitivity and accuracy across a range of gas concentrations. Two of the sensors they offer, the Gascard NG8 and the Guardian NG9 are suitable for detecting carbon monoxide, carbon dioxide or other hydrocarbon gases. If just carbon dioxide is of interest, then Edinburgh Sensors offers are more extensive range of monitors, including the Gascheck10 and the IRgaskiT.11

The advantage of NDIR detection for these gases are the device initial warm-up times are less than 1 minute, in the case of the Guardian NG. It is also capable of 0 – 100 % measurements such gases with a response time of less than 30 seconds from the sample inlet. The readout is ± 2 % accurate and all these sensors maintain this accuracy over even challenging environmental conditions of 0 – 95 % humidity, with self-compensating readout.

The Guardian NG comes with its own readout and menu display for ease of use and simply requires a reference gas and power supply to get running. For water purification purposes, the Gascard is particularly popular as the card-based device is easy to integrate into existing water testing equipment so testing of gases can occur while checking purity. .
Edinburgh Sensors also offers custom gas sensing solutions and their full technical support throughout the sales, installation and maintenance process.

References
1. Gleick, P. H. (2002). Dirty Water: Estimated Deaths from Water-Related Diseases 2000-2020 Pacific. Pacific Institute Researc Report, 1–12.

2. Water and Treated Water (2019), https://www.gov.uk/government/publications/water-and-treated-water/water-and-treated-water

3. Pangarkar, B. L., Deshmukh, S. K., Sapkal, V. S., & Sapkal, R. S. (2016). Review of membrane distillation process for water purification. Desalination and Water Treatment, 57(7), 2959–2981. https://doi.org/10.1080/19443994.2014.985728

4. Hijnen, W. A. M., Beerendonk, E. F., & Medema, G. J. (2006). Inactivation credit of UV radiation for viruses, bacteria and protozoan (oo)cysts in water: A review. Water Research, 40(1), 3–22. https://doi.org/10.1016/j.watres.2005.10.030

5. McCarty, P. L., & Smith, D. P. (1986). Anaerobic wastewater treatment. Environmental Science and Technology, 20(12), 1200–1206. https://doi.org/10.1021/es00154a002

6. Scott, J. P., & Ollis, D. F. (1995). Integration of chemical and biological oxidation processes for water treatment: Review and recommendations. Environmental Progress, 14(2), 88–103. https://doi.org/10.1002/ep.670140212

7. Florescu, D., Iordache, A. M., Costinel, D., Horj, E., Ionete, R. E., & Culea, M. (2013). Validation procedure for assessing the total organic carbon in water samples. Romanian Reports of Physics, 58(1–2), 211–219.

8. Gascard NG, (2019), https://edinburghsensors.com/products/oem/gascard-ng/

9. Guardian NG (2019) https://edinburghsensors.com/products/gas-monitors/guardian-ng/

10. Gascheck (2019), https://edinburghsensors.com/products/oem/gascheck/

11. IRgaskiT (2019), https://edinburghsensors.com/products/oem-co2-sensor/irgaskit/

12. Boxed GasCard (2019) https://edinburghsensors.com/products/oem/boxed-gascard/

 

#Pauto @Edinst

No messing about on river conservation!

06/12/2018

Scientists from the University of Portsmouth have been investigating nutrient concentrations in the Upper River Itchen, in Hampshire (GB), on behalf of Salmon & Trout Conservation (S&TC) to better understand where phosphorus is coming from and how it is impacting river ecology.

The work has been ongoing for over three years and Lauren Mattingley, Science Officer for S&TC says: “Continuous monitoring of phosphorus has improved our understanding of nutrient dynamics in the Itchen. So far, the results from this monitoring have influenced the lowering of discharge limits from watercress companies and trout breeding farms.

“The behaviour of phosphorus in our rivers is relatively poorly understood, and this is often reflected in water quality standards that, in our opinion, lack the scientific evidence to adequately protect the ecology of the UK’s diverse water resources. Research like that which we have commissioned on the Itchen is essential to set informed phosphorus permits to protect our water life.”

Background
The Itchen is a world famous chalk stream; renowned for its fly fishing and clear water. Designated a ‘Special Area of Conservation’ (SAC) the river supports populations of water-crowfoot, Southern damselfly, Bullhead, Brook lamprey, White-clawed crayfish and otters. The upper river does not suffer from wastewater treatment plant discharges, but does support two watercress farms, which have been the focus of initiatives to reduce phosphate concentrations.

S&TC is the only British charity campaigning for wild fish and their habitats. The organisation’s goal is for British waters to support abundant and sustainable populations of wild fish and all other water-dependent wildlife. Within its ‘Living Rivers’ campaign S&TC is seeking to tackle two of the major causes of poor water quality – fine sediment and phosphorus. The Itchen is therefore being treated as a pilot river for their water quality monitoring initiatives.

Phosphorus in fresh water is a major concern globally; mainly because of its role in the formation of algal blooms and eutrophication, which have a harmful effect on water quality and habitats. Under certain conditions, raised phosphate concentrations contribute to the proliferation of nuisance phytoplankton as well as epiphytic and benthic algae. Diffuse sources of phosphate include storm water and agricultural run-off from land, and point sources include septic tanks and wastewater discharges from industry and sewage treatment works. While soluble reactive phosphorus (SRP) is the main concern, because of its availability for aquatic organism growth, other forms of phosphate such as particulate phosphate can contribute to nutrient enrichment.

Efforts to improve the quality of water bodies in Britain have been underway for many years. The EU’s Water Framework Directive (WFD) required Britain to achieve ‘good status’ of all water bodies (including rivers, streams, lakes, estuaries, coastal waters and groundwater) by 2015, but in 2012 only 36% of water bodies were classified as ‘good’ or better.

In 2013 the UK Technical Advisory Group (UKTAG) published recommendations to revise the standards for phosphorus in rivers, because the standards set in 2009 were not sufficiently stringent – in 75% of rivers with clear ecological impacts of nutrient enrichment, the existing standards produced phosphorus classifications of good or even high status! DEFRA (British Government Department looking after environmental matters), therefore, revised the phosphorus standards to lower concentrations. However, the SRP concentration limits vary widely according to the location and alkalinity of the river.

Recognising a gap in the understanding of the relationship between phosphorus and aquatic ecology, S&TC has a unique agreement with the Environment Agency (EA) in Hampshire in which key environmental targets have been established for the Rivers Test and Itchen to help drive ecological improvements. The agreed targets are set around the number of key water insects that should be expected in a 3-minute kick-sweep sample. The targets are for the middle and lower reaches of the catchment to support at least 10 separate mayfly species and 500 freshwater shrimps (Gammarus) – all of which are susceptible to different forms of pollution so their presence provides an effective measure of the environmental health of the river.

S&TC has also conducted research investigating the effects of fine sediment and SRP on the hatching of the blue winged olive, Serratella ignita (Ephemerellidae: Ephemeroptera) a crucial component of the aquatic food chain. The results found that a cocktail of SRP and fine sediment at concentrations exceeding those found in many UK rivers (25 mg/L fine sediment and 0.07 mg/L phosphate) caused 80% of the eggs in the experiment to die. This work was unique because it showed environmental damage caused by phosphorus beyond eutrophication.

River Itchen sampling and analysis
Five automatic water samplers have been strategically located on the river each collecting daily samples. This generates 120 samples per 24 day cycle, which are collected and transferred to the laboratory in Portsmouth. The samples are split into three for the analysis of Total Phosphate, Soluble Reactive Phosphate (SRP) and Total Dissolved Phosphate (TDP). To cope with such a high volume of work, the laboratory in the University of Portsmouth’s School of Earth & Environmental Sciences employs a QuAAtro 5-channel segmented flow autoanalyzer, from SEAL Analytical.

“The QuAAtro has been in heavy use for over 9 years,” says Senior Scientific Officer Dr Adil Bakir. “It has been employed on a number of academic and commercial research projects, and is also used for teaching purposes. As a 5-channel instrument, we are able to study phosphate, nitrate, nitrite, ammonia and silicate, but our work on the River Itchen is focused on the different forms of phosphate.”

The University of Portsmouth’s Environmental Chemistry Analytical Laboratory provides analytical and consultancy services for businesses, universities and other organisations. Dr Bakir says: “Using the QuaAAttro we are able to analyse diverse matrices including river water, sea water and wastewater, and with automatic dilution and high levels of sensitivity, we are able to measure a wide range of concentrations.”

Creating effective discharge consents
The analytical work undertaken by the laboratory at the University of Portsmouth has greatly improved the understanding of the ecology of the River Itchen and thereby informed the development of appropriate discharge consents for the two watercress farms. Effective 1st January 2016, new discharge permits were issued by the Environment Agency that set limits on phosphate discharges to the River Itchen system. For the Vitacress Pinglestone Farm these limits are set at 0.064 mg/L and are measured as an annual mean increase compared to the inlet sample.

S&TC now works closely with Vitacress, monitoring immediately downstream of the discharge so that the effects of the new discharge limit can be effectively assessed.

Looking forward, Lauren says: “The lessons that we have learned on the Itchen are transferrable, and do not just apply to chalk streams. All rivers have their issues and inputs, so proper diagnosis and understanding of how these inputs shape the biology is essential to the successful restoration of degraded systems.

“In an ideal world phosphorus targets would be bespoke, on a river by river basis, and determined by tailored research and proper monitoring.

“River ecology is impacted by a wide variety of factors and whilst nutrients represent a serious risk, it is important for us to understand all of the threats, and the relationships between them. In summary, without high-resolution monitoring, river standards and river restoration efforts will be blind to their consequences.”

#SealAnalytical #Environmental @SalmonTroutCons @_Enviro_News


High frequency monitoring needed to protect UK rivers!

29/06/2018
Nigel Grimsley from OTT Hydrometry describes relatively new technologies that have overcome traditional barriers to the continuous monitoring of phosphate and nitrate.

The science behind nutrient pollution in rivers is still poorly understood despite the fact that nitrate and phosphate concentrations in Britain’s rivers are mostly unacceptable, although an element of uncertainty exists about what an acceptable level actually is. Key to improving our understanding of the sources and impacts of nutrient pollution is high-resolution monitoring across a broad spectrum of river types.

Background

Green Box Hydro Cycle

Phosphates and nitrates occur naturally in the environment, and are essential nutrients that support the growth of aquatic organisms. However, water resources are under constant pressure from both point and diffuse sources of nutrients. Under certain conditions, such as warm, sunny weather and slow moving water, elevated nutrient concentrations can promote the growth of nuisance phytoplankton causing algal blooms (eurtrophication). These blooms can dramatically affect aquatic ecology in a number of ways. High densities of algal biomass within the water column, or, in extreme cases, blankets of algae on the water surface, prevent light from reaching submerged plants. Also, some algae, and the bacteria that feed on decaying algae, produce toxins. In combination, these two effects can lower dissolved oxygen levels and potentially kill fish and other organisms. In consequence, aquatic ecology is damaged and the water becomes unsuitable for human recreation and more expensive to treat for drinking purposes.

In its State of the Environment report, February 2018, the British Environment Agency said: “Unacceptable levels of phosphorus in over half of English rivers, usually due to sewage effluent and pollution from farm land, chokes wildlife as algal blooms use up their oxygen. Groundwater quality is currently deteriorating. This vital source of drinking water is often heavily polluted with nitrates, mainly from agriculture.”

Good ecological status
The EU Water Framework Directive (WFD) requires Britain to achieve ‘good status’ of all water bodies (including rivers, streams, lakes, estuaries, coastal waters and groundwater) by 2015. However, only 36% of water bodies were classified as ‘good’ or better in 2012. Nutrient water quality standards are set by the Department for Environment, Food & Rural Affairs (DEFRA), so for example, phosphorus water quality standards have been set, and vary according to the alkalinity and height above mean sea level of the river. Interestingly, the standards were initially set in 2009, but in 75% of rivers with clear ecological impacts of nutrient enrichment, the existing standards produced phosphorus classifications of good or even high status, so the phosphorus standards were lowered.

Highlighting the need for better understanding of the relationships between nutrients and ecological status, Dr Mike Bowes from the Centre for Ecology & Hydrology has published research, with others, in which the effects of varying soluble reactive phosphate (SRP) concentrations on periphyton growth rate (mixture of algae and microbes that typically cover submerged surfaces) where determined in 9 different rivers from around Britain. In all of these experiments, significantly increasing SRP concentrations in the river water for sustained periods (usually c. 9 days) did not increase periphyton growth rate or biomass. This indicates that in most rivers, phosphorus concentrations are in excess, and therefore the process of eutrophication (typified by excessive algal blooms and loss of macrophytes – aquatic plants) is not necessarily caused by intermittent increases in SRP.

Clearly, more research is necessary to more fully understand the effects of nutrient enrichment, and the causes of algal blooms.

Upstream challenge
Headwater streams represent more than 70% of the streams and rivers in Britain, however, because of their number, location and the lack of regulatory requirement for continuous monitoring, headwater streams are rarely monitored for nutrient status. Traditional monitoring of upland streams has relied on either manual sampling or the collection of samples from automatic samplers. Nevertheless, research has shown that upland streams are less impaired by nutrient pollution than lowland rivers, but because of their size and limited dilution capacity they are more susceptible to nutrient impairment.

References
• Bowes, M. J., Gozzard, E., Johnson, A. C., Scarlett, P. M., Roberts, C., Read, D. S., et al. (2012a). Spatial and temporal changes in chlorophyll-a concentrations in the River Thames basin, UK: are phosphorus concentrations beginning to limit phytoplankton biomass? Sci. Total Environ. 426, 45–55. doi: 10.1016/j.scitotenv. 2012.02.056
• Bowes, M. J., Ings, N. L., McCall, S. J., Warwick, A., Barrett, C., Wickham, H. D., et al. (2012b). Nutrient and light limitation of periphyton in the River Thames: implications for catchment management. Sci. Total Environ. 434, 201–212. doi: 10.1016/j.scitotenv.2011.09.082
• Dodds, W. K., Smith, V. H., and Lohman, K. (2002). Nitrogen and phosphorus relationships to benthic algal biomass in temperate streams. Can. J. Fish. Aquat Sci. 59, 865–874. doi: 10.1139/f02-063
• McCall, S. J., Bowes, M. J., Warnaars, T. A., Hale, M. S., Smith, J. T., Warwick, A., et al. (2014). Impacts of phosphorus and nitrogen enrichment on periphyton accrual in the River Rede, Northumberland, UK. Inland Waters 4, 121–132. doi: 10.5268/IW-4.2.692
• McCall, S. J., Hale, M. S., Smith, J. T., Read, D. S., and Bowes, M. J. (2017). Impacts of phosphorus concentration and light intensity on river periphyton biomass and community structure. Hydrobiologia 792, 315–330. doi: 10.1007/s10750-016-3067-1

Monitoring technology
Sampling for laboratory analysis can be a costly and time-consuming activity, particularly at upland streams in remote locations with difficult access. In addition, spot sampling reveals nutrient levels at a specific moment in time, and therefore risks missing concentration spikes. Continuous monitoring is therefore generally preferred, but in the past this has been difficult to achieve with the technology available because of its requirement for frequent re-calibration and mains power.

High resolution SRP monitoring has been made possible in almost any location with the launch by OTT Hydromet of the the ‘HydroCycle PO4’ which is a battery-powered wet chemistry analyser for the continuous analysis of SRP. Typically, the HydroCycle PO4 is deployed into the river for monitoring purposes, but recent work by the Environment Agency has deployed it in a flow-through chamber for measuring extracted water.

The HydroCycle PO4 methodology is based on US EPA standard methods, employing pre-mixed, colour coded cartridges for simple reagent replacement in the field. Weighing less than 8kg fully loaded with reagents, it is quick and easy to deploy, even in remote locations. The instrument has an internal data logger with 1 GB capacity, and in combination with telemetry, it provides operators with near real-time access to monitoring data for SRP.

The quality of the instrument’s data is underpinned by QA/QC processing in conjunction with an on-board NIST standard, delivering scientifically defensible results. Engineered to take measurements at high oxygen saturation, and with a large surface area filter for enhanced performance during sediment events, the instrument employs advanced fluidics, that are resistant to the bubbles that can plague wet chemistry sensors.

Environment Agency application
The National Laboratory Service Instrumentation team (NLSI) provides support to all high resolution water quality monitoring activities undertaken across the Agency, underpinning the EA’s statutory responsibilities such as the WFD, the Urban Waste Water Directive and Statutory Surface Water Monitoring Programmes. It also makes a significant contribution to partnership projects such as Demonstration Test Catchments and Catchments Sensitive Farming. Technical Lead Matt Loewenthal says: “We provide the Agency and commercial clients with monitoring systems and associated equipment to meet their precise needs. This includes, of course, nutrient monitoring, which is a major interest for everyone involved with water resources.”

Matt’s team has developed water quality monitoring systems that deliver high resolution remote monitoring with equipment that is quick and easy to deploy. There are two main options. The ‘green box’ is a fully instrumented cabinet that can be installed adjacent to a water resource, drawing water and passing it though a flow-through container with sensors for parameters such as Temperature Dissolved Oxygen, Ammonium, Turbidity, Conductivity pH and Chlorophyll a. Each system is fitted with telemetry so that real-time data is made instantly available to users on the cloud.

Conscious of the need to better understand the role of P in rivers, Matt’s team has integrated a HydroCycle PO4 into its monitoring systems as a development project.
Matt says: “It’s currently the only system that can be integrated with all of our remote monitoring systems. Because it’s portable, and runs on 12 volts, it has been relatively easy to integrate into our modular monitoring and telemetry systems.

“The HydroCycle PO4 measures SRP so if we need to monitor other forms of P, we will use an auto sampler or deploy a mains-powered monitor. However, monitoring SRP is important because this is the form of P that is most readily available to algae and plants.”

Explaining the advantages of high resolution P monitoring, Matt refers to a deployment on the River Dore. “The data shows background levels of 300 µg P/l, rising to 600 µg P/l following heavy rain, indicating high levels of P in run-off.”

Nitrate
Similar to phosphates, excessive nitrate levels can have a significant impact on water quality. In addition, nitrates are highly mobile and can contaminate groundwater, with serious consequences for wells and drinking water treatment. Nitrate concentrations are therefore of major interest to the EA, but traditional monitoring technology has proved inadequate for long-term monitoring because of a frequent recalibration requirement. To address this need, which exists globally, OTT Hydromet developed the SUNA V2, which is an optical nitrate sensor, providing high levels of accuracy and precision in both freshwater and seawater.

The NLSI has evaluated the SUNA V2 in well water and Matt says: “It performed well – we took grab samples for laboratory analysis and the SUNA data matched the lab data perfectly. We are therefore excited about the opportunity this presents to measure nitrate continuously, because this will inform our understanding of nitrate pollution and its sources, as well as the relationship between groundwater and surface water.”

Summary
The new capability for high-resolution monitoring of nutrients such as phosphorus will enable improved understanding of its effects on ecological status, and in turn will inform decisions on what acceptable P concentrations will be for individual rivers. This is vitally important because the cost of removing P from wastewater can be high, so the requirements and discharge limits that are placed on industrial and wastewater companies need to be science based and supported by reliable data. Similarly, nitrate pollution from fertilizer runoff, industrial activities and wastewater discharge, has been difficult to monitor effectively in the past because of the technology limitations. So, as improved monitoring equipment is developed, it will be possible to better understand the sources and effects, and thereby implement effective prevention and mitigation strategies.

@OTTHydrometry @EnvAgency @CEHScienceNews #Water #Environment

Researchers investigate ultra-low Mediterranean nutrient levels.

25/04/2018

Researchers at Haifa University’s Marine Biological Station in Israel are exploiting the ultra-low detection limits of advanced laboratory equipment to measure extremely low nutrient concentrations in marine water.

H.Nativ – Morris Kahn Marine Research Station

The University’s Prof. M. D. Krom says: “We work in the Eastern Mediterranean which has the lowest regional concentration of dissolved nutrients anywhere in the global ocean. We therefore utilize an automated segmented flow analyzer from SEAL Analytical, which has been specially adapted to accommodate ultra-low measurements.”

The SEAL AutoAnalyzer 3 (AA3) is a 4 channel system, measuring Phosphate with a long flow cell which has a detection limit of 2 nM. Ammonia is measured using a JASCO fluorometer with a similar ultra-low detection limit, and Silicate, which has a higher concentration, is measured using SEAL’s high resolution colorimetric technology.

The measurement data are being used to determine the season nutrient cycling in the system, which will then be used to help understand the nature of the food web and the effects of global environmental and climate change.

Low nutrient levels in the Mediterranean
The eastern Mediterranean Sea (EMS) has an almost unique water circulation. The surface waters (0-200m) flow into the Mediterranean through the Straits of Gibraltar and from there into the EMS at the Straits of Sicily. As the water flows towards the east it becomes increasingly saline and hence denser. When it reaches the coast of Turkey in winter it also cools and then flows back out of the Mediterranean under the surface waters to Sicily, and then eventually through the Straits of Gibraltar to the North Atlantic. This outflowing layer exists between 200m and 500m depth.

Phytoplankton grow in the surface waters (0-200m) because that is the only layer with sufficient light. This layer receives nutrients from the adjacent land, from rivers and wastewater discharges, and also from aerosols in the atmosphere. These nutrients are utilized by the plankton as they photosynthesize. When the plants die (or are eaten) their remains drop into the lower layer and are jetted out of the EMS. Because the water flows are so fast (it takes just 8 years for the entire surface layers of the EMS to be replaced), these nutrient rich intermediate waters rapidly expel nutrients from the basin. The result is very low nutrient concentrations and very low numbers of phytoplankton – some of the lowest values anywhere in the world. Prof. Krom says: “The maximum levels of nutrients measured in the EMS are 250 nM phosphate, 6 uM nitrate and 6-12 uM silicate. Ammonia is often in the low nanomolar range. By contrast, in the North Atlantic, values are 1000 nM phosphate, 16 uM nitrate and 20 uM silicate, and the levels in the North Pacific are even higher.”

The value of data
The low levels of plankton caused by low nutrient levels, result in a low biomass of fish. Nevertheless, coastal areas generally support more fish than offshore, so the research will seek to quantify and understand the nutrient cycle in the coastal regions, which is poorly understood at present. “We plan to develop understandings which will inform stakeholders such as government. For example, there is a discussion about the potential for fish farms off the Israeli coast, so our work will enable science-based decisions regarding the quantity of fish that the system can support.”

To-date, three data sets have been taken from the EMS, and the first publishable paper is in the process of being prepared.

Choosing the right analyzer
Prof. Krom says that his first ‘real’ job was working for the (then) Water Research Centre at Medmenham in Britain, where he was involved in the development of chemical applications for the Technicon AA-II autoanalyzers, which included going on secondment to Technicon for several months. SEAL Analytical now own and manufacture the AutoAnalyzer brand of Continuous Segmented Flow Analyzers, so his career has been connected with autoanalyzers for decades. For example his is Professor (Emeritus) at the University of Leeds (GB), where, again, he worked with SEAL autanalyzers. An AA3 instrument was employed at Leeds in a project to investigate the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans.

Explaining the reasoning behind the purchase of a new AA3 at Haifa University, Prof. Krom says: “During a research cruise, it is necessary to analyse samples within a day to avoid changes in concentration due to preservation procedures.

“Typically we analyse 50-80 samples per day, so it is useful to useful to be able to analyze large numbers of samples automatically. However, the main reasons for choosing the SEAL AA3 were the precision, accuracy and low limits of detection that it provides.”

Commenting on this application for SEAL’s analyzers, company President Stuart Smith says: “Many of our customers analyze nutrient levels in freshwater and marine water samples, where high levels of nutrients are a concern because of increasing levels of algal blooms and eutrophication. However, Prof. Krom’s work is very interesting because, in contrast, he is looking at extremely low levels, so it is very gratifying that our instruments are able to operate at both ends of the nutrient concentration spectrum.

Bibliography
• Powley, H.R., Krom, M.D., and Van Cappellen, P. (2017) Understanding the unique biogeochemistry of the Mediterranean Sea: Insights from a coupled phosphorus and nitrogen model. Global Biogeochemical Cycles, 11; 1010-1031. DOI 10.1002/2017GB005648.

• Stockdale, A. Krom, M. D., Mortimer, R.J.G., Benning, L.G., Carslaw, K.S., Herbert, R.J., Shi, Z., Myriokefalitakis, S., Kanakidou, M., and Nenes, A., (2016) Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans. PNAS vol. 113 no. 51

#SealAnal #Marine @_Enviro_News

Train derailment prompts contaminated land investigation.

11/01/2018

A train derailment in Mississippi resulted in ground contamination by large quantities of hazardous chemicals, and environmental investigators have deployed sophisticated on-site analytical technology to determine the extent of the problem and to help formulate an effective remediation strategy. Here Jim Cornish from Gasmet Technologies discusses this investigation.

Jim Cornish

On March 30th 2015 a long freight train, transporting a variety of goods including lumber and chemicals, wound its way through the state of Mississippi (USA). At around 5pm, part of the train failed to negotiate a curved portion of the track in a rural area near Minter City, resulting in the derailment of nine railcars, one of which leaked chemicals onto agricultural farmland and woodlands. Emergency response and initial remediation activities were undertaken, but the remainder of this article will describe an environmental investigation that was subsequently conducted by Hazclean Environmental Consultants using a portable multiparameter FTIR gas analyzer from Gasmet Technologies.

Background
Over 17,000 gallons of Resin Oil Heavies were released from the railcar, and the main constituent of this material is dicyclopentadiene (DCPD). However, in addition to DCPD, Resin Oil Heavies also contains a cocktail of other hydrocarbons including ethylbenzene, indene, naphthalene, alpha-methyl styrene, styrene, vinyl toluene, 1, 2, 3-trimenthylbenzene, 1, 2, 4-trimethylbenzene, 1, 3, 5-trimethylbenzene and xylenes.

DCPD is highly flammable and harmful if swallowed and by inhalation. Its camphor-like odor may induce headaches and symptoms of nausea, and as a liquid or vapor, DCPD can be irritating to the eyes, skin, nose, throat or respiratory system. DCPD is not listed as a carcinogen, however DCPD products may contain benzene, which is listed as a human carcinogen. DCPD is not inherently biodegradable, and is toxic to aquatic organisms with the potential to bioaccumulate.

It is a colorless, waxy, flammable solid or liquid, used in many products, ranging from high quality optical lenses through to flame retardants for plastics and hot melt adhesives. As a chemical intermediate it is used in insecticides, as a hardener and dryer in linseed and soybean oil, and in the production of elastomers, metallocenes, resins, varnishes, and paints. DCPD-containing products are also used in the production of hydrocarbon resins and unsaturated polyester resins.

Emergency Response
Emergency response phase activities were performed from March 31 through May 2, 2015. Response objectives and goals were formally documented by utilizing Incident Action Plans for each operational period. Activities between April 11 and April 28, 2015 were summarized in weekly reports and submitted to the Mississippi Department of Environmental Quality (MDEQ) and the Environmental Protection Agency (EPA).

Approximately 10,189 gallons of the leaked product was recovered, leaving 5,458 gallons to contaminate the farmland surface and subsurface soil, surface waters, groundwater and ambient air. The site contamination problem was exacerbated due to heavy rainfall and associated stormwater runoff which caused the unrecovered product to migrate from the spill site.

Taking account of the high rainfalls levels that followed the event, it was calculated that contaminated stormwater runoff from the immediate project site (10 acres with 8.7 inches of rainfall) was 2,362,485 gallons less that retained by emergency retention berms. Approximately 207,000 gallons of contaminated stormwater were collected during the emergency response, in addition to approximately 7,870 tons of impacted material which were excavated for disposal. Following removal of the gross impacted material, the site was transferred into Operation and Maintenance status, conducted in accordance with a plan approved by MDEQ.

Ongoing site contamination
Groundwater and soil samples were collected and analyzed in 2015 and 2016, producing analytical data which confirmed that widespread soil and groundwater contamination still existed at the site. Further remediation was undertaken, but the landowners were extremely concerned about the fate of residual chemicals and contracted Hazclean Environmental Consultants to conduct a further investigation.

“The affected land is used for agricultural purposes, producing crops such as soybeans and corn,” says Hazclean President, E. Corbin McGriff, Ph.D., P.E. “Consequently, there were fears that agricultural productivity would be adversely affected and that chemicals of concern might enter the food chain.
“This situation was exacerbated by the fact that the landowners could still smell the contamination and initial investigation with PID gas detectors indicated the presence of volatile organic compounds (VOCs).”

Hazclean’s Joseph Drapala, CIH, managed and conducted much of the site investigation work. He says: “While PID gas detectors are useful indicators of organic gases, they do not offer the opportunity to quantify or speciate different compounds, so we spoke with Jeremy Sheppard, the local representative of Gasmet Technologies, a manufacturer of portable FTIR (Fourier Transform Infrared) gas analyzers.

Soil Vapor Analysis with FTIR

“Jeremy explained the capabilities of a portable, battery-powered version of the Gasmet FTIR gas analyzer, the DX4040, which is able to analyze up to 25 gases simultaneously, producing both qualitative and quantitative measurements. Gasmet was therefore contacted to determine whether this instrument would be suitable for the Mississippi train spill application.

“In response, Gasmet confirmed that the DX4040 would be capable of measuring the target species and offered to create a specific calibration so that these compounds could be analyzed simultaneously on-site.”

Site investigation with FTIR analysis
A sampling zone was defined to capture potential contamination, and measurements were taken for surface and subsurface soil, groundwater, and surface and subsurface air for a range of VOCs.

Vapor Well

The area-wide plan resulted in the installation of four permanent monitoring wells for groundwater sampling, twenty vapor monitoring wells, and twenty test borings for field screening. The test borings indicated the presence of VOCs which were further characterized by sampling specific soil sections extracted from the parent core.

In addition to the almost instantaneous, simultaneous measurement of the target compounds, the Gasmet DX4040 stores sample spectra, so that post-measurement analyses can be undertaken on a PC running Gasmet’s Calcmet™ Pro software, providing analytical capability from a library of 250 compounds. “The Gasmet DX4040 was manufacturer-calibrated for dicyclopentadiene, benzene, ethylbenzene, naphthalene, styrene, toluene, 1,2,3-trimenthylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and m, o, and p and total xylenes at a detection range of 0.01 ppm to 100 ppm in air,” Joseph reports, adding: “The ability to compare recorded spectra with the Calcmet Pro library is a major advantage because it enables the measurement of unknown compounds.”

The operating procedures for the DX4040 indicate a simple, convenient requirement for daily calibration with zero gas prior to each monitoring activity. However, in addition to the use of nitrogen as the zero gas, Joseph also employed specialty gas (DCPD) certified for 1 ppm and 5 ppm as a calibration check and a response (akin to bump testing) gas.

Site screening
The test borings provided soil samples that were vapor-tested on-site as part of the screening process. Vapor from the extracted soil samples was analyzed by placing the soil samples in vessels at ambient temperature and connecting the DX4040 in a closed loop from the vessel, so that air samples could be continually pumped from the vessel to the analyzer and returned to the vessel. This screening activity helped to determine the location for vapor wells.

All soil samples were screened with the DX4040 and those with the highest reading from each boring were sent for laboratory analysis.

Vapor wells were fitted with slotted PVC liners and capped. Before monitoring, the cap was replaced with a cap containing two ports to enable the DX4040 to be connected in a similar closed-loop monitoring system to that which was employed for the soil samples.

Conclusions
As a result of this investigation it was possible for Hazclean to determine that the release of DCPD in the vapor state, as measured in the vapor monitor wells, is a result of surface and subsurface contamination in the soil and groundwater, and that this contamination will remain in the future.

Vapor analysis data provided by the DX4040 identified DCPD, benzene, styrene and xylene previously adsorbed on soil and/or wetted surfaces undergoing diffusion and evaporation. The adsorption, diffusion and evaporation of DCPD et al. released and spread across the farmland is a mechanism to explain the vapor concentrations found in vapor monitor wells as well as the ambient malodor problem.

The long term release of DCPD and other VOCs will continue to occur in the impact area unless a larger remediation project is conducted to remove soil and groundwater contamination. Furthermore, Hazclean recommends that, as a result of the effectiveness of the Gasmet DX4040 in this investigation, the same technology should be employed in any subsequent screening activities, using the same Gasmet calibration configuration.

Summarizing, Joseph Drapala says: “The Gasmet DX4040 was an essential tool in this investigation. Screening activities should have the ability to detect and identify the target compounds, as well as any secondary compounds that may have already been present on-site or could have been produced as a result of chemical interactions.
“As an FTIR gas analyzer, the DX4040 meets these requirements, providing enormous analytical capability through Gasmet’s Calcmet software. However, the instrument is also small, lightweight and battery powered which makes it ideal for field investigations.”


Measuring CO2 to optimise bulk storage of food.

24/07/2017

Meeting the food requirements of a growing global population is becoming increasingly difficult. Despite the need for additional food, it is estimated that 50-60% of grain is lost after harvesting, at a cost of about $1 trillion per year. (See note 1 below)

One of the major reasons for lost grain is spoilage due to mould or insect infestation during storage.2 To provide a constant supply of grain year-round, after grains are harvested they are often kept in long term storage. Maintaining the quality of stored grain is crucial, both to ensure the quality of the final food products, and to prevent economic losses for farmers.

Edinburgh Sensors GascardNG Sensor

Insects and moulds can grow in stored grain, and their ability to flourish depends on the temperature and moisture of the stored grain. Moulds are the most common cause of grain spoilage and can cause changes in the appearance and quality of stored grains. Some moulds can release toxic chemicals called mycotoxins which can suppress the immune system, reduce nutrient absorption, cause cancer, and even be lethal in high doses. It is therefore crucially important to prevent the presence of mycotoxins in food products.2

Monitoring Stored Grain
Farmers are advised to check their stored grain weekly for signs of spoilage.3 Traditionally, grains are checked visually and by odour. Grain sampling can allow earlier detection of insects and moulds, but these methods can be tedious and time-consuming. Rapid, simple methods are needed for early detection of spoilage and to prevent grain losses.2

When moulds and insects grow, and respire, they produce CO2, moisture and heat. Temperature sensors detect increases in temperature caused by mould growth or insect infestation, therefore indicating the presence of grain spoilage. However, they are not able to detect temperature increases caused by infestation unless the infestation is within a few meters of the sensors. CO2 sensors can detect the CO2 produced by moulds and insects during respiration. As the CO2 gas moves with air currents, CO2 sensors can detect infestations that are located further away from the sensor than temperature sensors. CO2 measurements are therefore an important part of the toolkit needed to monitor stored grain quality.2

Using CO2 Measurements to Detect Spoilage
CO2 monitoring can be used for early detection of spoilage in stored grains, and to monitor the quality of stored grains. Safe grain storage usually results in CO2 concentrations below 600 ppm, while concentrations of 600-1500 ppm indicate the onset of mould growth. CO2 concentrations above 1500 ppm indicate severe infestations and could represent the presence of mycotoxins.4

CO2 measurements can be taken easily, quickly and can detect infestations 3-5 weeks earlier than temperature monitoring. Once spoilage is detected, the manager of the storage facility can address the problem by aerating, turning, or selling the grain. Furthermore, CO2 measurements can aid in deciding which storage structure should be unloaded first.2

Research published by Purdue University and Kansas State University have confirmed that high CO2 levels detected by stationary and portable devices are associated with high levels of spoilage and the presence of mycotoxins.4,5 Furthermore, they compared the ability of temperature sensors and CO2 sensors in a storage unit filled with grain to detect the presence of a simulated ‘hot spot’ created using a water drip to encourage mould growth.

The CO2 concentration in the headspace of the storage unit showed a strong correlation with the temperature at the core of the hot spot, and the CO2 sensors were, therefore, able to detect biological activity. The temperature sensors were not able to detect the mould growth, despite being placed within 0.3-1 m of the hotspot.6

To enable efficient monitoring of grain spoilage accurate, reliable and simple to use CO2 detectors are required. Gascard NG Gas Detector from Edinburgh Sensors provide accurate CO2 measurements along with atmospheric data, enabling grain storage managers to make decisions with confidence.

The Gascard NG Gas Detector uses a proprietary dual wavelength infrared sensor to enable the long term, reliable measurement of CO2 over a wide range of concentrations and in temperatures ranging from 0-45 °C. Measurements are unaffected by humidity (0-95% relative humidity) and the onboard pressure and temperature sensors provide real-time environmental compensation, resulting in the most accurate CO2 concentration readings.

Conclusion
Easy, fast, and accurate CO2 concentration monitoring during grain storage can provide early detection of grain spoilage, resulting in reduced grain losses, higher quality stored grain, and lower mycotoxin levels. CO2 monitoring could save millions of dollars annually in the grain production industry.4


References

  1. Kumar D, Kalita P, Reducing Postharvest Losses during Storage of Grain Crops to Strengthen Food Security in Developing Countries. Foods 6(1):8, 2017.
  2. http://www.world-grain.com/Departments/Grain-Operations/2016/7/Monitoring-CO2-in-stored-grain.aspx?cck=1 Accessed May 25th, 2017.
  3. HGCA Grain storage guide for cereals and oilseeds, third edition, available from: https://cereals.ahdb.org.uk/media/490264/g52-grain-storage-guide-3rd-edition.pdf Accessed May 25th, 2017.
  4. Maier DE, Channaiah LH, Martinez-Kawas, A, Lawrence JS, Chaves EV, Coradi PC, Fromme GA, Monitoring carbon dioxide concentration for early detection of spoilage in stored grain. Proceedings of the 10th International Working Conference on Stored Product Protection, 425, 2010.
  5. Maier DE, Hulasare R, Qian B, Armstrong P, Monitoring carbon dioxide levels for early detection of spoilage and pests in stored grain. Proceedings of the 9th International Working Conference on Stored Product Protection PS10-6160, 2006.
  6. Ileleji KE, Maier DE, Bhat C, Woloshuk CP, Detection of a Developing Hot Spot in Stored Corn with a CO2 Sensor. Applied Engineering in Agriculture 22(2):275-289, 2006.