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

Helping provide reliable flood protection in Switzerland.

11/04/2018

Extreme weather is becoming increasingly common throughout the world, making flooding a growing threat. Flood defence measures have traditionally been based on mechanical equipment, but innovative automation technology can now be used to provide greater protection for people and the local environment. AWA – the Office for Water and Waste in the Swiss canton of Berne – is using this latest technology to regulate water levels at the region’s Brienzersee, Thuner and Bielersee lakes, 24 hours a day, 365 days a year.

“Water level regulation must protect people from flooding and prevent damage – ideally in an economically justifiable way,” said Dr Bernhard Wehren, head of maritime regulation at AWA. “Some of our important control operations are particularly time-critical, but until recently, we relied on dataloggers that only sent the different measurements we require every few hours or so. Now, thanks to the new state-of-the-art technology we have implemented, this happens in real time. It is therefore very important that the data communications technology supports this by reliably meeting all the challenges and requirements of our unique mission-critical communications infrastructure.”

Modernising facilities
To help provide the most reliable flood protection, AWA decided to modernise its water regulation facilities for the lakes, encompassing four historic locks, the large Port of Bruggweir and accompanying hydropower plant, and a flood relief tunnel. Due to the increasing demand for the availability of more data, AWA also decided to upgrade all the measurement stations with state-of-the-art technology. The measurement stations play a crucial role in regulating water levels in the lakes.

When developing a plan to modernise the equipment, great attention was paid to both operational safety and system redundancy. There was a need to address the obsolete electrical engineering at Port of Brugg. This would include the conversion of all existing drives and the renewal of the energy supply, a large part of the cabling and the control and monitoring elements for the five weirs. Regulation and control technology also needed attention. Not only was there a need for redundancy in the event of a device failure or a line interruption, but also in case of communication disruptions, such as interruptions to the internet connection.

BKW Energie AG was appointed as the technical service provider and after a thorough review of suitable data communications technology companies, they chose Westermo to provide its robust networking solutions for the project.

Fast communication performance
“Crucial to the selection of Westermo was that their products met our high standards and requirements for the project. This included fast communication performance, multiple routing ports per device, high MTBF periods, extended temperature ranges and very low power consumption,” said Rénald Marmet, project engineer at BKW Energie. “Another factor was the operation and parameterisation of the networking hardware via the WeOS operating system. Also, the extremely efficient and time-saving update capability provided by the WeConfig network management software, which enables the central configuration and management of all Westermo devices.”

The main control network incorporates the AWA control centre in the capital, Berne,and further control centres at the water locks, Thun and Interlaken, each with one SCADA server and redundant controller. The control centres connect to 29 substations (measuring points). Eight SCADA clients access these servers. There is also a SCADA server located in the hydropower plant, providing BKW employees with access. The hydropower plant part is monitored by the BKW control centre in Mühleberg.

Westermo networking technology allows all data to be transferred in real-time between the participating sites. Should an emergency arise, this enables those responsible to take the appropriate measures immediately to ensure the best possible protection against flooding. Also, maintenance and software updates for all the installed Westermo networking devices can be performed easily and quickly with just a few mouse clicks.

In total, Westermo provided thirty of its RFIR-227 Industrial Routing Switches, twenty-seven VDSL Routers, twenty-fiveMRD-4554G Mobile Routers, thirty-five Lynx 210-F2G Managed Ethernet Switches with Routing Capability, thirty-six L110-F2G Industrial Layer -2 Ethernet Switches, and over eighty 100 Mbps and 1 Gbps SFP fibre optic transceivers via multimode and single-mode fibre for distances up to 80km.

Greater network redundancy
The three control centres all have two firewall routers connecting them to the internet providers and enabling them to receive or set up the IPsec and OpenVPN tunnels. There are also two redundant Siemens Simatic S7-400controllers installed in a demilitarized zone (DMZ) and a WinCC SCADA server connected to the local network. The AWA SCADA station has the same design, but without the control functionality.

BKW took care not only to create network redundancy, but also to set up redundant routes to the internet providers. The VDSL routers use the service provider Swisscom, and the MRD-455 4G mobile radio routers are equipped with SIM-cards from Sunrise. The heart of the main network – the three control centres and the AWA control centre- are linked by IPsec-VPN Tunnels and Generic Routing Encapsulation(GRE) and form the automation backbone via Open Shortest Path First(OSPF) technology.

The result of this is that even should there be simultaneous connection failure to an internet provider in one location and the other provider at another station, or the total failure of one provider, communication between all centres, the connected remote stations and the remote access by BKW or AWA is still possible.

For increased safety, the external zones are segmented further. The service technicians can connect to the control centres through an OpenVPN tunnel and have access to all measuring stations on the network.

There are two different types of measuring stations. The high availability station consists of two completely separate networks. Each PLC is installed ‘behind’ a Westermo Lynx 210 device, which acts as a firewall and establishes the connection to the control centre via an OpenVPN tunnel. The redundant internet access is provided either via a VDSL router, which is connected to Swisscom, or a MRD-455 with Sunrise as the provider. A ‘standard’ station has only one PLC with a Lynx 210 acting as a firewall router and building the VPN tunnels in parallel via the two internet routers.

Security requirements
As well as network redundancy, security was also part of the requirements to guarantee high communication availability. The network implemented by BKW and Westermo provides the necessary security in accordance with recommendations found in the BDEW whitepaper and IEC-62443 standard. The outstations not only form their own zone, but other areas are also segmented where necessary. The network for the SCADA servers in the control centres is also decoupled from the backbone using two VRRP routers.

The flood defence system now has one of the most modern data communication systems in Switzerland. Explaining why this is so important to AWA, Dr Bernhard Wehren said: “Protection against flooding must be guaranteed at all times. Depending on the meteorological or hydrological situation, the availability of the required measured values is critical. Because access to the measuring stations in the extensive regions of the canton is generally very time-consuming, network device failures and communication interruption must be kept to a minimum. It is therefore extremely important that all components of our communication systems meet the highest standards, offer extreme reliability and can be upgraded to meet new requirements.”

“We were able to simplify processes, make them secure, redundant and transparent for the engineering department via VPN connections. This contributes significantly to the simple, safe and efficient maintenance of the system,” Rénald Marmet said. “Thanks to the extensive cooperation with Westermo network engineers, we were able to create the ideal solution that meets all requirements and was delivered on time. Westermo’s reliable networking technologies have given AWA and BKW the opportunity to build individual data communication solutions for critical industrial applications, while providing scalable, future-proof applications. The solution also offers all involved a high degree of investment security.”

#Switzerland. @Westermo @bkw #Environment #PAuto

Treating wastewater as a resource.

27/09/2016
A number of British landfill operators are turning wastewater into a resource by utilising OTT monitoring and control systems to manage the irrigation of Willow crops (for renewable energy generation) with pre-treated effluent.

Background
Leachate from landfill sites represents a significant potential environmental liability, extending long into the future after a landfill site has closed. Conventional treatment and disposal options involve biological treatment and consented discharge to either the wastewater treatment network or to the environment. Alternatively, effluent may be collected by tanker for treatment and disposal off-site. However, to improve sustainability and broaden the treatment options, work initiated in the 1990s developed an approach that sought to use effluent as a source of nutrients and water for a Short Rotation Coppice (SRC) crop planted upon the restored landfill.

Willows fed on wastewater!

Willows fed on wastewater!

Following the success of early trials, the Environment Agency published a Regulatory Position Statement in 2008, which said: ‘SRC as part of a landfill leachate treatment process… is a technique (that) can be an environmentally acceptable option if managed appropriately.’

Early systems were operated and managed manually but with the addition of OTT sensors, telemetry and control systems, the process was automated to optimise irrigation and maximise both the disposal of effluent and biomass yield.

Willow SRC has become increasingly popular in environmental restoration work, providing a cost-effective material for stabilisation and reclamation of disturbed landscapes, bioremediation and biomass production.

SRC involves the planting of high yielding varieties of willow at a high density, typically 15,000 plants per hectare. The crop can be expected to last for around 30 years, with harvesting taking place every 3-5 years, and yields varying from 8 to 18 tonnes of dry woodchip per hectare per year. Willow grows quickly and has a particularly high demand for water, so it is ideal for the disposal of large volumes of treated effluent. In addition, the high planting density results in the development of a dense root hair system; effectively creating a biological filter for the treatment of organic compounds and the absorption of nutrients and some heavy metals. Soil fauna help to break down the effluents applied to the crop and soil particles control the availability of nutrients to the willow.

Monitoring and control
In early schemes, irrigation was managed manually on a timed basis with irrigation quantities based on external estimates of evapotranspiration. However, increased levels of monitoring and control are now possible. OTT’s Matthew Ellison explains: “The key objective is to supply the crop with an optimised amount of water, whilst minimising the requirement for staff on site. Too much irrigation would cause run-off and too little would under-utilise the treated effluent and result in poor growth conditions which would affect yield and potentially threaten the crop.

Soil moisture sensors

Soil moisture sensors

“An on-site weather station feeds local weather data to the system which uses crop data to predict evapotranspiration that is used to determine irrigation rates. Soil moisture sensors then check that soil moisture status is correct. Other sensors monitor the performance of the system; checking irrigation feed reservoir level, in-pipe pressure and there are sensors to check flow rates from the drip-feed irrigation. This communication capability is made possible with OTT’s Adcon Telemetry radio network.

“Our latest monitoring and control equipment automates the management of the system for unattended operation and staff are only required by exception. This means that the system is able to operate autonomously, delivering regular data reports, and staff are notified by email or text if alarm conditions occur.”

Emphasising the advantages of controlling the entire network, Matthew adds: “This system facilitates the ability to control and synchronise the main pump, and to open and close the valves at each irrigation zone.”

The latest OTT monitoring and control systems include:

  1. Soil moisture sensors
  2. Irrigation tank level sensors
  3. Irrigation function check sensors
  4. Pipe valves and pressure sensors
  5. Automatic weather station (to calculate local evapotranspiration)
  6. Radio telemetry
  7. ADCON Gateway and PC running addVANTAGE software
  8. Internet connectivity for remote log in

Summary
Looking back over a number of SRC projects, Stephen Farrow one of the instigators of this approach in the UK, and now an Independent Consultant says: “When viewed practically, environmentally and commercially, experience has demonstrated the viability of the overall approach.

“It is also clear that process optimisation with relatively low cost investment in OTT’s monitoring and control equipment has significantly added to the support functionality in terms of both operation and regulatory management.’’

OTT’s Matthew Ellison agrees, adding: “SRC clearly offers a sustainable option for effluent treatment, with highly positive effects on carbon footprint and biodiversity.

“In addition to the environmental benefits, process automation has significantly reduced labour requirements and helped to demonstrate compliance with the site-specific requirements of the Environment Agency.”


It’s the little things that trip you up!

22/01/2016
By Brian Booth, VP of the Water Treatment Innovation Platform, NCH Europe

There’s a lot of chemistry, physics and maths involved in perfecting your water treatment solution. To make sure you successfully treat and protect your system you need to get the equilibrium right, and this relies on balancing all the appropriate equations – even the little things you may not give much thought to. Missing something like half life out of your planning can have serious negative implications for your water treatment, especially when it comes to complying with regulations such as those for Legionella control.

When dosing your water cooling system with biocides it’s imperative that the concentration is correct and that it remains at a continuous concentration for a suitable period of time. While this sounds simple, it’s easy to forget that any bleed water required to compensate for water that may evaporate out of a system, will take a portion of your biocide with it.

Say you put 10 tonnes of make-up water into your system, and every hour 1 tonne runs off as bleed water, this will determine the half life for your system. So for example, let’s imagine the chemical you are using to meet the Government’s Health and Safety Executive (HSE) Legionella control L8 Code of Practice needs to remain at a concentration of 100 parts per million (ppm) for three hours to be successful.

If you just dose 100ppm and walk away, the concentration will gradually fall from the time of dosing and will not remain high enough for long enough as the bleed water will take a portion away with it. This will result in a failure to meet the regulation, making you negligent and leaving you liable.

This is why it’s vital to be aware of half life so that you can increase the dose of your biocide accordingly. Do you know how many hours it would take to reduce a 100ppm dose to 50ppm in your water cooling system?

Although it’s hard to be 100 per cent accurate, you can work out your half life with this simple equation:

 

Half_Life_hours.jpg

If you know your biocide is going to take three hours to be effective, but the half life of your system is one hour you’re going to have to make some adjustments to maintain appropriate concentration. For instance, using our above example of legionella control biocide, to stay at a minimum of 100ppm for long enough you’ll need to dose to 800ppm.

A bit of predictive mathematics goes a long way towards protecting your water system and keeping you compliant. Don’t let a little thing like half life leave you vulnerable to negligence claims – do the maths first!

Half_life_in_water_treatment


Pressure Transducer Delivers water level monitoring in emergency tank shower!

24/11/2014

Applied Measurements were recently contacted by spill control and containment manufacturer Empteezy, to provide a sensor to be used within an emergency tank shower.  The emergency tank shower is ideal for use in locations where a constant water supply and adequate water pressure cannot be guaranteed.

Emergency_showerThe Challenge 
To ensure the emergency tank shower is able to provide a flow of 75.7ltrs per minute of water for 15 minutes, fulfilling the ANSI Z358.1 regulations for emergency tank showers.

The Problem 
Once a gravity fed shower is switched on and the water level within the tank drops, both the water pressure and the flow rate at the shower head decreases.  In order to achieve the flow rate of 75.7ltrs per minute of water for the full 15 minutes, the emergency tank shower needs to contain a minimum of 2000ltrs of water within the tank.

The Solution
Applied Measurements provided Empteezy with a Pi600 series pressure transducer.  The pressure transducer was connected and calibrated to the digital readout scale on the front of the shower, giving an accurate reading of the litres of water remaining in the tank.  When the water level falls below the minimum safety level, a signal is sent to the sounder strobe alarm on the front of the shower.  This signal has a dual function. Firstly, alerting safety personnel that the water level has dropped below the minimum, notifying them to refill the shower to achieve the required flow rate and water pressure. Secondly, that the shower has been operated and an injured employee may need assistance.

Pi600The Pi600 Series of Pressure Transducers
The Pi600 series of pressure sensors are designed for the measurement of gas and liquid pressure across a wide range of general purpose and industrial applications such as hydraulics, medical, research and development, meteorology and food processing.  Constructed from stainless steel with a ceramic diaphragm and viton ‘O’ ring seal as standard, they are designed to be extremely rugged, yet compact in design.

Key Features Include:

  • Ranges 0-50mbar up to 0-700bar
  • Wide Variety of Outputs: mV/ Volts / mA
  • Can be Offered Calibrated in Metres Water Gauge
  • Sealed to IP65 (plug & socket) or IP66/68 (Cable)
  • Accuracy: <±0.25%/FS (0.1% option)
  • Gauge or Absolute Versions
  • Various Pressure Port Options (G1/4” male as standard)
  • Excellent Chemical and Abrasion Resistance
  • Rugged Construction
  • Full Customisation Possible

These pressure transducers come in pressure ranges of 0-50mbar and 0-700bar in absolute or gauge versions, with a wide choice of electrical output signals from its ASIC-based amplifier circuit.  These outputs include, 4-20mA, 0-5Vdc & 0-10Vdc, 1-6Vdc and 10mV/V, as well as a ratiometric 0.5-4.5Vdc signal that requires a 5Vdc supply to suit most data loggers.  The Pi600 series of pressure transducers can also be supplied with any of our wide range of instrumentation to give you a complete calibrated system.

In addition, the series can be completely customised to suit your application including; custom process connections, alternate case and ‘O’ ring material for applications where aggressive media is present, and higher IP ratings for more challenging environments.

The Pi600 series of pressure transducers have proved vital in Empteezy’s emergency tank shower units, enabling engineers to guarantee the water pressure and flow rate of the units.  We are always looking for new and exciting challenges so contact our technical sales team today on +44 (0) 118 981 7339 or info@appmeas.co.uk to discuss your application.