Water / Wastewater extracted and analysed in real-time.
Continuous monitoring also offers an up-to-date snapshot of process conditions as they exist. With manual testing methods, the results are only valid for the time when the test was conducted – the operator would not be able to evaluate current process conditions. Access to real-time information allows immediate action to be taken if any issues occur.
Combined txr & sensor pic - ROUGH need to be maintained between 1.5ppm to 2ppm.
As aeration accounts for around 66 percent of energy use in wastewater treatment, failing to ensure tight control of dissolved oxygen greatly increases the risk of operators incurring excessive energy costs.
Continuously measuring dissolved oxygen levels with a CWA system allows variable speed drives to be used to provide the right level of aeration in the process and thus optimize energy use.
Continuous monitoring meets the challenges
Accurate, rapid assessment of the levels of these pollutants and parameters is vital if they are to be controlled to specifi ed limits economically.
When evaluating pollutants, or dosing chemicals, a device offering continuous measurement offers several advantages over manual methods. With these, time lost between extraction of the sample and the subsequent testing often affects the value of the result. With online CWA systems, samples are automatically
This was the basis of a system designed by ABB for Southern Water. Although intended for use on a potable water treatment works, the principles are the same. The system replaced an obsolete automatic coagulant dosing system that was reaching the end of its operational life. The customer also wanted improved control and instrumentation to cut OPEX by reducing dosing needs and maintenance effort.
ABB developed a continuous measurement and control system combining high and low-range UV organics (DOC) surrogate colour, turbidity and pH analysers with an RVG200 controller / recorder.
The system calculates the optimum amount of coagulant that will allow effective removal of particulates through sedimentation and fi ltration. Using real-time data from the analysers, the RVG200 uses a fully-confi gurable algorithm to adjust coagulant and account for seasonal fl uctuations in raw water or physical changes to the process.
This produces values for the actual required dose (mg/l) and dose rate (ml/min), used to control coagulant dosing pumps, ensuring that the correct amount of coagulant is always administered.
The feedback control modifi es the coagulant dose by maintaining colour for the clarifi ed water within a set target band. This improved on the previous system that used only feed-forward control, with no feedback input.
5
Sensor-Cleaning-304
The use of a fully confi gurable algorithm means the system can be easily adjusted to handle any variations in upstream conditions, with any changes being able to be easily carried out using the RVG200 controller and with the use of an Ethernet connection, it enables the convenience of remote condition monitoring.
After a year of operation, Southern Water has seen 12 percent reduction in coagulant consumption, maintenance tasks decreased by more than half, and reliable control in line with raw water quality changes.
With the right instruments for the right job and an appropriate control system, Continuous Water Analysis can go a long way to meeting the requirements of the regulators while also keeping the cost of wastewater management under control.
Author Contact Details Julian Edwards, ABB Ltd • Howard Road, Eaton Socon, Saint Neots, Cambridgeshire, PE18 8EU, UK • Tel: +44 1480 475 321 • Email:
enquiries.mp.uk@
gb.abb.com • Web:
www.abb.com/measurement
Camera for monitoring of water and wastewater
Geolux impressed visitors at the recent IFAT trade fair with their versatile HydroCam, a camera they have developed for the water industry to visually monitor remote hydrological locations. The HydroCam enables end-users to physically see level fl uctuations to anticipate fl ooding as well as any interferences or
obstructions affecting the site. Its zoom lens allows a more detailed examination of pollutants, sediment build-up, ice – it is also an ideal device for visual, site monitoring at wastewater treatment plants and reduces the time and expense of sending staff to inspect the site in person. The camera can be set to take regular photographs of the site facilitating a rapid response in the event of any problems at the site and allowing the operator to keep a record of the area being monitored.
The HydroCam features an IR refl ector to enable use after dark and a switchable day/ night fi lter and can operate at temperatures ranging from -20 °C to 60 °C.
58032pr@reply-direct.com
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