Energy-efficient membranes offer suitable option for wastewater reclamation
Water is vital to creating a sustainable economy, but accelerated urbanization and economic growth place stress on regions, countries and cities already experiencing severe water shortages.
The availability of fresh clean water especially is severe in developing countries. UN-Water, a collaboration between various United Nations agencies, estimates that as much as 70% of industrial wastewater is dumped into waterways untreated in developing countries around the world.
As a result, an increasing number of government entities are identifying the true value of treated wastewater to help optimize their water resources. For many, this means implementing cost-effective treatment strategies to recycle and reuse municipal wastewater throughout a community or region.
Communities around the world are finding ways to reuse and recycle treated municipal sewage for irrigation and even drinking water, either directly or indirectly, as a means to address water shortages. By strengthening wastewater treatment strategies, communities are meeting water reuse goals in non-potable and industrial applications, which alleviates pressure on drinking water supplies.
In building an effective water management strategy, communities are relying on technology to strike a balance between treatment effectiveness, cost of treatment and the value of the water. For many communities around the world, submerged ultrafiltration (UF) membranes provide a suitable solution for their needs.
How It Works
UF membrane technology is a low-energy process that submerges the membranes into tanks of feedwater. The hollow fiber membranes serve as a physical barrier to contaminants in the feedwater.
For example, GE’s ZeeWeed 1000 contains thousands of horizontally oriented hollow fibers mounted between two vertical plastic headers. Shrouds enclose the fibers, leaving only the bottom and top open to create a vertical flow upward through the fiber bundles.
The small pore size of the UF strands, typically 0.02 µ, ensure that particulate matter, including Cryptosporidium cysts, Giardia cysts, bacteria, suspended solids or other contaminants of concern, will pass into the treated water stream.
With a compact design and high-filtration capability, hollow-fiber UF membranes offer several benefits, including:
- Lower energy costs;
- Lower life cycle and maintenance costs;
- Smaller footprint and related construction costs; and
- Simplistic system design.
The membrane filtration system can replace the secondary clarifier and sand filters in a traditional activated sludge treatment system.
As concerns over energy efficiency increase, UF technology becomes more appealing, as the systems can process more water using less energy than other traditional systems, especially when coupled with reverse osmosis (RO) filtration. Three countries have adopted UF membranes as part of a water management strategy.
Like in many countries around the world, potable water is a limited resource in Spain. As part of a holistic water management strategy, the Regional Government of Valencia invested in treating wastewater as a source of irrigation water to release potable water for the city’s inhabitants and visitors. The government installed a UF treatment system at its wastewater treatment plant followed by RO permeate blending, producing 33.3 million liters per day (mld) of high-quality irrigation water. Most importantly, this is water that otherwise would have been discharged to the sea.
China has experienced accelerated economic growth and urbanization, creating intense water shortages. For China, the treatment of municipal sewage for beneficial reuse is a viable strategy to meet many of the country’s water initiatives.
During preparations for the 2008 Olympic games in Beijing, China, the country invested to improve infrastructure, including reuse of municipal sewage. Pollution reduction and control measures were improved in the Chaobai River, Qinghe River and Yangshan Channel, where aquatic sports venues for the 2008 Olympic Games were to be located.
During the games, the treated effluent was reused in lagoons, ponds and landscape irrigation in the Olympic village. Following the Olympic games, the Qinghe wastewater reclamation plant, which is one of the largest wastewater plants in China, began selling the water for irrigation or as toilet flush water. At the Qinghe wastewater recovery facility, which utilizes the GE ZeeWeed 1000 membrane, produces 80,000 cu meters per day of UF permeate from secondary effluent. It is estimated that nearly 90% of urban wastewater is collected and treated, with approximately 50% of that being reused.
Since 2010, the Advanced Water Treatment Plant (AWTP) in North Western Sydney produces 50 mld of high-quality water, making it one of the largest water recycling projects in Australia. A key component of the water treatment strategy is the UF RO plant.
The recycled water from the treatment plant replenishes water in the Warragamba Dam reservoir, ensuring a sustainable supply of drinking water for the surrounding community and keeping an important waterway replenished with fresh clean water.
In addition to wastewater treatment, UF membranes are common in industrial applications that require high water purity, such as boiler feedwater, cooling tower blowdown, pharmaceutical, and food and beverage processing.
Over more than 10 years, UF membrane technology has developed into a viable treatment strategy for water reuse programs in Spain, China and Australia. With a vision of high-quality treated wastewater at cost-effective rates for its residents and industry, communities are implementing treatment strategies that include submerged UF membranes to meet water reuse objectives.
Editor's Note: SUEZ, together with Caisse de dépôt et placement du Québec, closed its purchase of GE’s Water & Process Technologies on September 30, 2017. The new business unit is SUEZ Water Technologies & Solutions.