The Evolution of Low-Pressure, Immersed Membrane Technology

Nearly one and a half billion gallons of the world’s water and wastewater treatment capacity is entrusted to ZENON ZeeWeed® immersed, hollow-fiber ultrafiltration (UF) membrane technology. ZeeWeed low pressure polymer membranes are at the center of a global trend to adopt more efficient and more robust water treatment technologies that work to safeguard public health, protect the environment and create sustainable water supplies.

Today, after nearly 25 years of championing the innovation and evolution of low-pressure, immersed membrane technology, ZENON continues to be a leader in this rapidly growing and dynamic market. Hundreds of ZENON water and wastewater treatment plants throughout the world are providing municipalities with clean, safe drinking water and are restoring municipal and industrial wastewater beyond the most stringent effluent standards to make it safe for discharge to sensitive environments, or reuse in irrigation, industrial process water and groundwater recharge.

ZeeWeed membranes are also being increasingly evaluated to perform pretreatment of seawater and ensure consistently high quality feedwater for reverse osmosis desalination systems. With such a diversity of applications, ZENON is clearly demonstrating that robust and reliable ZeeWeed membranes are proven to be capable of efficiently and cost-effectively handling virtually any type, or any size, of water treatment task at municipal, industrial, land development, recreational and military sites.

Rising acceptance

Water and wastewater treatment with immersed UF membranes is now comparable in cost to conventional technology within the developed world. Cost continues to fall as ongoing improvements produce smaller and more efficient membrane systems. Together with simple system architecture and advanced automated control of membrane permeation, cleaning, and monitoring, ZENON plants are among the most operator friendly in the industry. Ranging in treatment capacity from just a few hundred gallons per day to tens of millions of gallons per day, modular ZeeWeed immersed-membrane systems are appearing in rural, urban, and remote areas and are providing positive results for even the most difficult to treat water sources.

ZENON UF membrane fibers resemble long strands of spaghetti, and thousands of such fibers hang loosely in each modular cassette. Unlike pressurized membrane systems that require significant energy to force water through the system and may be more susceptible to fouling, ZeeWeed works by applying a slight suction to the end of the fibers to draw water through microscopic pores. With a nominal size of only 0.04 mm, the membranes prevent suspended solids, path-ogens and viruses from passing through and achieve greater than 4-log removal of pathogens like Giardia and Cryptosporidium. Because ZeeWeed forms a physical barrier to particles, the membranes provide a consistent stream of high quality treated water. Automatically controlled cyclic aeration and intermittent backpulsing ensure that the membrane fibers remain clean and operate at optimum efficiency.

Two types of ZeeWeed membranes form the foundation of the ZENON product line. The ZeeWeed 500 incorporates reinforced hollow-fiber membranes that are robust and can be immersed directly into the high-solids environment of a membrane bioreactor (MBR). Not only does this combination of membrane technology and biological processes result in high effluent quality, it also eliminates the need for clarifiers and granular filter media, which reduces the footprint of a wastewater treatment plant. In most cases, a ZeeWeed MBR plant typically requires only about 1?4 of the space that a conventional wastewater treatment plant would occupy.

The ZeeWeed MBR has a proven record of success that ranges from small pre-engineered packaged systems to one of the world’s largest operating MBR plant in Kaarst, Germany (12 MGD flow). ZENON recently announced an agreement for an even larger plant at the Johns Creek Environmental Campus outside of Atlanta, Ga. Once completed, this MBR plant will have a capacity of 25 MGD. For water treatment applications that do not require reinforced membranes, the ZENON ZeeWeed 1000 provides versatile, cost-effective performance that is ideal for drinking water treatment, seawater pretreatment for RO desalination and tertiary treatment of secondary effluent. The newest version of the ZeeWeed 1000 features a significant 20% increase in the surface area of each module, packing even more energy-efficient performance into a compact plant footprint.

Communities of all sizes are replacing or retrofitting water treatment plants with ZeeWeed 1000 membranes to ensure safe, clean drinking water for their residents, including the Region of Peel in Ontario, Canada which recently selected ZeeWeed 1000 to upgrade its Lakeview Water Treatment Plant. Membranes will add 86 MGD of treatment capacity to this plant that serves a rapidly growing urban area.

Modular components simplify retrofits and expansions

The modular configuration of ZeeWeed membranes makes them inherently adaptable to retrofit existing water treatment plants. In many cases, granular filter media can be simply removed from the tank and replaced with ZeeWeed membranes. Not only can much of the existing infrastructure be reused, but plant capacity is often doubled due to the efficiency of the membranes.

Existing wastewater treatment plants can also be upgraded with a tertiary membrane filtration system or to a ZeeWeed MBR process. The compact size of the membranes often allows plants significantly expand capacity, without increasing the footprint of the plant. This can significantly reduce capital costs and simplify expansion plans if space constraints exist.

Commitment to R&D

Smart upgrades, enhanced performance, ease of operation, and declining costs of ZeeWeed membranes are possible because of ZENON’s commitment to continuously improving its products. Each year, ZENON invests millions of dollars to research and develop better membrane polymers and more efficient configurations of system design. As municipalities and industries continue to specify immersed, low pressure ZeeWeed UF membranes as their preferred choice for water and wastewater treatment, technological improvements will continue to rise and costs will continue to decline. As this trend moves forward, ZENON will achieve the objective on which it was founded—to preserve the global water supply and ensure that membrane technology can provide safe, superior and cost-effective water for the world.