Gee Design Package Plant: The Perfect Partner for Wastewater Nanofiltration Projects
1 July 2010, News release from Gee & Company
The application of nanofiltration techniques, utilising synthetic membrane technology for the purification of drinking water, is a growing business.
More and more frequently too, specially-designed Gee Packaged Plant modules are being chosen to form an integral part of these schemes.
Periodic disinfection of the filtration membranes, using sodium hypochlorite as the chlorine source, is an essential part of the maintenance regime in a nanofiltration plant, and so Gee & Co. is supplying fully-packaged, bespoke chemical storage and dosing systems built around 0.75 cubic metre capacity PVC GRP chemical storage tanks.
The systems are mounted on a rectangular bund of thermoplastic GRP-wrapped construction which also houses the storage tank complete with hand mixer.
The entire mechanical and electrical design was carried out in house by Gee and Company. The polypropylene dosing skid houses two duty standby peristaltic chemical dosing pumps, which are fitted with lockable isolators and emergency stops, with a clear PVC lift-off screen for operator inspection.
All of the cabling is taken to individual junction boxes for control, power and analogue outputs. The unit also incorporates a separately bunded area for the storage of the 25 litre sodium hypochlorite carboys, and a drum pump with which to transfer their contents.
Gee has worked closely with WTW operators to meet a clear market need for cost-effective, reliable and sustainable solutions. Filtration techniques have developed significantly during the last few years and nanofiltration is increasingly being employed due to its efficacy in the removal of natural organic matter (NOM) from drinking water supplies.
NOM can be common in the bodies of soft environmental water found in colder, more northerly climates, such as the lochs and rivers from which much of Scotland's drinking water is sourced.
Composed mainly of humic substances (degraded bio-molecules found in soil and water, lake sediments, peats and shales), NOM can pose problems not just in the overall appearance of potable water, but also in terms of the risk of these substances being halogenated into trihalomethanes through reaction with chlorine and other halogens used in the water purification process.
Nanofiltration plants can process a range of water flows, and the treatment systems employed reflect this. At smaller plants, those that only process up to approximately 150 cubic metres per day, tubular membranes are used, while elsewhere spiral membranes are needed to handle the larger water flows.
The choice of nanofiltration method employed is largely influenced by the whole-life cost of the plant. In general, the use of tubular membranes in water purification is prohibitively expensive for larger water processing plants due to the high cost of the filtration membrane per square metre, hence the use of the more cost-effective spiral membranes.
At works utilising tubular nanofiltration stacks the raw (environmentally sourced) water is first passed through inline strainers. Following this filtration the permeate is disinfected with a hypochlorite (bleaching agent) dosed by a Gee Design Package Plant system, whilst the membrane stacks themselves are separately treated with a hypochlorite disinfectant prior to reuse.
The final step is for the pH in the filtered water to be increased by passing the solution through a limestone neutralite filter to remove any unpleasant taste, and to reduce the corrosive effect on water carrying pipes. At this point the water is ready to be channelled to the clean water tank and then to public supply.
At larger Water Treatment Works the system is somewhat different. Raw water is passed through pressurised sand filters prior to entering the spiral nanofiltration membrane.
Again, following this stage, the filtration membrane is disinfected prior to reuse, whilst the permeate passes to a Gee Design Package Plant for hypochlorite-based disinfection. The purified water is then conditioned by being passed through a neutralite filter before being directed into public supply.
In applications such as these, Gee package plant systems offer a range of benefits in use, including a reduction in the quantity of chemicals utilised. Their small footprint makes them compact and energy efficient, and much quicker to install than traditional plant.
Gee worked to develop two Package Plant dosing systems specifically for these applications. As the manufacturer of all of the components, as well as being the system designer and integrator, Gee brings exceptional expertise in packaged plant systems to the table.
By creating a custom design for each type of nanofiltration system - one for tubular and one for spiral systems - the package plant units can be moved into production very quickly, with delivery to site often taking only 10-12 weeks, thanks to the greatly reduced on-site civil work entailed.
When compared with the 30-40 weeks it can take to design, engineer and install traditional dosing plant solutions the cost benefits are clear. All units are manufactured and fully tested, hydraulically and electrically, at Gee's Birmingham factory and then collected and installed on site by the end user's engineers.
If required however, Gee package plant units can be delivered to a customer's site on low loaders. In which case the off-loading, positioning and installation are managed by Gee's trained engineers who supervise all of the final connections leaving the plant "ready to run". As a result, site installation time, and therefore cost, are greatly reduced.
For further information please email Gee & Company