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.”

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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.


Remotely operated pneumatic water pumping system keeps Guernsey dry!

11/10/2014

Festo’s CPX platform – complete automation solution

Much like the mainland Britain, Guernsey has been ravaged by the forces of nature this year. But thanks to a remotely controlled, pneumatically operated pumping station that was completed last year, one area of the island has escaped damage from the resulting floods.

On February 3rd this year (2014) Guernsey faced one of its wettest and windiest days in recent memory. Heavy rain fell throughout much of the day and by the evening Guernsey Airport had recorded 32.5mm – more than an inch – of rainfall, flooding many of the island’s major roads, making several impassable and causing widespread disruptions.

Both local radio stations were forced off air as the FM transmitter was flooded, with TV signals being unavailable for part of the night. According to Guernsey Police more than 60 roads were flooded – which outpaced the number of closed signs available. Sandbags also ran short as authorities scrambled to contain the worst of the weather.

Guernsey_water

But thanks to improvements at the Marais Stream pumping station one area of the island emerged virtually unscathed from the onslaught. The pumping station, situated off les Banques not far from the capital of Guernsey, St Peter Port, is part of a network of facilities that form Guernsey Water’s infrastructure for the catchment, storage and transfer of raw water for the production of the island’s drinking water.

“Without a doubt we would have suffered big issues this winter with the heavy rainfall if we hadn’t undertaken the work there,” Andy Benstead, Water Production Manager, at Guernsey Water says. “I can guarantee that there would have been problems if we hadn’t upgraded it.

“We don’t actually have rivers in Guernsey they are all classified as streams; the Marais Stream has a fair catchment area and it includes a bank and an insurance company, and without this work they would have been flooded.”

 The work at the pumping station was an upgrade; the whole infrastructure was changed apart from an old tank that remained. “There were two reasons for the upgrade, part age and part because the area had suffered from a flooding problem,” Benstead adds. “The equipment is much bigger, more reliable, easier to control and we can now pump up to 1000 litres a second.”

Marais Stream pumping station was originally built in 1938 and required an upgrade to allow an increased volume of water to be collected and delivered to the nearby water treatment works with less going to waste.

Geomarine, a local civil engineering contractor, was contracted by Guernsey Water to carry out these improvement works as part of on-going works on the island’s infrastructure. Before the project was started all that was on site was a holding tank and pump house.

Marais Stream collects the run-off water from the local area and this is fed via the three inlet penstocks   through fine screens that remove debris that would damage the pumps in the pumping station. The water is then pumped either into the treatment works or, in the case of heavy rainfall such as earlier this year, can be diverted and discharged straight into the sea.

The entire system is run by Festo’s CPX remotely operated control system

The entire system is run by Festo’s CPX remotely operated control system

The pumping station is the first on the Island which could be considered ‘multifunctional’, as it incorporates three vital elements. Firstly, raw water (rainfall) is caught and transferred into Longue Hougue reservoir for conversion into drinking water. Secondly, stream water is used to maintain the cleanliness of the screens at the new Belle Greve Wastewater Treatment Centre. Finally, the new pumping station enables excess water to be pumped out to sea, which might otherwise overload the capacity of the Barker’s Quarry Reservoir and lead to localised flooding.

“Festo supplied three pneumatically operated penstocks, driven by linear actuators, to isolate the flow; these were located in the incoming channel,” Tony Gillard, Business Development Manager at Festo explains. “DNC cylinders with rod clamps are used to control the raising and lowering of the penstocks. These distribute the incoming water into the storage basins. From the storage basins, the water is distributed to various parts of the site by butterfly valves operated by pneumatic quarter-turn actuators.”

The entire system is run by Festo’s CPX remotely operated control system. The site itself is unmanned and is controlled via the SCADA system from the Guernsey Water Offices based five miles away. “The CPX platform is a complete automation solution that integrates a wide choice of pneumatic and electrical, analogue and digital I/O,” Gillard explains. “CPX systems configured for specific requirements are delivered pre-built, tested and ready for installation, enabling system integrators to meet tight deadlines and budgets. For additional flexibility, the CPX platform can operate as either a self-contained industrial PLC, or as a local unit on a Fieldbus or Industrial Ethernet-based distributed system. In addition, a wide choice of I/O and connector modules makes interfacing to process sensors and actuators easy.

“Remote operation is becoming more common; with pneumatic control you have the functionality to remotely operate the system,” Gillard adds.

Unusually for the water treatment sector is the selection of pneumatically controlled valves rather than electric. “On Great Britain it is more usual to have electric actuators but the advantages of pneumatics are beginning to sway the market,” Gillard says. “In most other applications, such as petro chemical and industrial applications, pneumatics are the preferred solution, but for some reason in water treatment and sewage plants electric actuation is still predominant for now.”

Pneumatic automation presents an extremely reliable alternative to electrical automation systems and reduces the costs of investment, installation and operation compared with conventional electrical installations.”

Guernsey Water has gone down the path of changing electric actuators to pneumatic and is reaping the benefits. Pneumatic control delivers energy saving, ease of installation, safety and reliability, because of less moving parts, as well as being faster to operate and easier to control.