Ceramic Membranes for Wastewater Filtration – Part 2
The key to a global problem
Energy and water are always interlinked. Energy is needed to produce water (extraction, treatment and transport), and water is needed to produce energy (hydropower, steam to drive turbines and as a coolant in industrial processes). The scarcity of fossil resources and the demand for water will continue to grow due to population growth, energy demand and the effects of climate change.
Under pressure from rising water demand, now is the right time to bring the management of manufacturing plants and water-intensive industries into law and to regulate responsibility for water abstraction and discharge. In the future, enterprises will adopt and develop their own water filtration systems; this may include using modules or local filtration systems instead of discharging wastewater to central treatment systems. Such filtration systems require more suitable membranes. This means that innovations to increase wastewater filtration efficiency are needed and will be studied more closely in the near future.
According to Global Water Intelligence, water scarcity will determine governments’ water reuse policies. In China, agricultural water use fell from 86% in 1980 to 65% in 2005, with a target of 50% by 2050. Population growth, economic factors and water shortages have pushed China to make efforts in water treatment and reuse. China’s target was to increase water reuse from 14% to 25% by 2015. Other examples include Saudi Arabia, which aimed to increase water reuse from 11% to 65% by 2016, and Spain, which aimed to increase it from 11% to 40% by 2015.
Government intervention will become more common as demand for clean water supply rises, increasing pressure to reuse industrial wastewater. For example, the government of São Paulo state, Brazil, has introduced initiatives to protect drinking water for residents by banning the use of drinking water for industrial purposes. This forces enterprises to find solutions to reuse their wastewater or obtain reused water from other sources. Water filtration plants are being proposed and installed to meet São Paulo’s water needs. In Japan, a water reuse strategy was adopted early, and there are now more than 90 membrane filtration water treatment plants.
In the USA, wastewater treated for reuse accounts for about 11%. Although no specific targets have been set, the Natural Resources Defense Council (NRDC) has stated that 10 of the largest US cities are at risk of severe water shortages in the near future.
Several US pilot plants are using ceramic ultrafiltration membranes for industrial water reuse. A ceramic membrane water treatment system was developed by the Parker Water and Sanitation District (PWSD) for one of its water treatment plants, treating water from a wastewater reservoir to supplement the water supply. In this plant, ceramic membranes were preferred because they reduce installation costs and are estimated to have a service life of up to 20 years.
Porous ceramic components
To meet these trends, new ceramic membranes are being developed for use in new types of water filtration systems for industrial water treatment. These systems will be more energy-efficient in cleaning and recirculating liquids than conventional systems using tubular ceramic membranes.
Materials scientists and product development engineers are working with new porous ceramic components with filtration layers of about 25 µm (about ¼ the diameter of a human hair). These filtration systems are used for microfiltration and ultrafiltration applications. After filtration, industrial wastewater can be reused or safely discharged into the environment.
The reliability and durability of high-quality ceramic membranes allow enterprises to reduce maintenance costs and energy use, achieving overall savings.
Ceramic membranes show high thermal resistance and durability in environments with strong cleaning chemicals, and can meet the need to filter aggressive and highly viscous liquids. They also withstand harsh environments in wastewater treatment equipment and do not need to be replaced as often as polymer materials.
In addition, ceramic membranes can be manufactured with low dimensional tolerances and complex geometries, enabling flexible and innovative designs that make filtration modules more energy-efficient. This means enterprises can save energy and costs associated with pumping water through the filtration system.
Sustainable development is becoming increasingly important for enterprises. The environmental benefits of water filtration are well recognised. New-generation ceramic water filtration membranes will help enterprises operate more efficiently, save money and protect water resources.
Figure 2. Ceramic filtration membranes
