259
hybrid systems as they can be retained by the membrane and can significantly
reduce the reaction efficiency. Thus, raw water pretreatment is usually required to
reduce the turbidity. Nanomaterials can also be immobilized on various platforms
such as resins and membranes to avoid further separation. However, current immobilization techniques usually result in significant loss of treatment efficiency.
Research is needed to develop simple, low-cost methods to immobilize nanomaterials without significantly impacting its performance. For magnetic nanoparticles/
nanocomposites, low-field magnetic separation is a possible energy-efficient option.
Little is known about the release of nanomaterials from nanotechnology-enabled
devices. However, the potential release is expected to be largely dependent on the
immobilization technique and the separation process employed. If no downstream
separation is applied, nanomaterials coated on treatment system surfaces are more
likely to be released in a relatively fast and complete manner, while nanomaterials
embedded in a solid matrix will have minimum release until they are disposed of.
For nanomaterials that release metal ions, their dissolution needs to be carefully
controlled (e.g., by coating or optimizing size and shape). The detection of nanomaterial release is a major technical hurdle for risk assessment and remains challenging. Details regarding detection techniques are beyond the scope of this chapter, and
readers are referred to several recent reviews on this topic [72, 303]. Few techniques
can detect nanomaterials in complex aqueous matrices and they are usually sophisticated, expensive, and with many limitations. Fast, sensitive, and selective nanomaterial analytical techniques are in great need.
Barriers and Research Needs
Although nanotechnology-enabled water/wastewater treatment processes have
shown great promise in laboratory studies, their readiness for commercialization
varies widely. Some are already on the market, while others require significant
research before they can be considered for full-scale applications. Their future
development and commercialization face a variety of challenges including technical
hurdles, cost-effectiveness, and potential environmental and human risk. There are
two major research needs for full-scale applications of nanotechnology in water/
wastewater treatment. First, the performance of various nanotechnologies in treating real natural and wastewaters needs to be tested. Future studies need to be done
under more realistic conditions to assess the applicability and efficiency of different
nanotechnologies as well as to validate nanomaterial-enabled sensing technologies.
Secondly, the long-term efficacy of these nanotechnologies is largely unknown as
most lab studies were conducted for relatively short period of time. Research
addressing the long-term performance of water and wastewater treatment nanotechnologies is in great need. As a result, side-by-side comparison of nanotechnologyenabled systems and existing technologies is challenging.
Despite the superior performance, the adoption of innovative technologies strongly
depends on the cost-effectiveness and the potential risk involved. The current cost of
nanomaterials is prohibitively high with few exceptions such as nano- TiO 2 , nanoscale
Current and Potential Applications for Water and Wastewater Treatment
hybrid systems as they can be retained by the membrane and can significantly
reduce the reaction efficiency. Thus, raw water pretreatment is usually required to
reduce the turbidity. Nanomaterials can also be immobilized on various platforms
such as resins and membranes to avoid further separation. However, current immobilization techniques usually result in significant loss of treatment efficiency.
Research is needed to develop simple, low-cost methods to immobilize nanomaterials without significantly impacting its performance. For magnetic nanoparticles/
nanocomposites, low-field magnetic separation is a possible energy-efficient option.
Little is known about the release of nanomaterials from nanotechnology-enabled
devices. However, the potential release is expected to be largely dependent on the
immobilization technique and the separation process employed. If no downstream
separation is applied, nanomaterials coated on treatment system surfaces are more
likely to be released in a relatively fast and complete manner, while nanomaterials
embedded in a solid matrix will have minimum release until they are disposed of.
For nanomaterials that release metal ions, their dissolution needs to be carefully
controlled (e.g., by coating or optimizing size and shape). The detection of nanomaterial release is a major technical hurdle for risk assessment and remains challenging. Details regarding detection techniques are beyond the scope of this chapter, and
readers are referred to several recent reviews on this topic [72, 303]. Few techniques
can detect nanomaterials in complex aqueous matrices and they are usually sophisticated, expensive, and with many limitations. Fast, sensitive, and selective nanomaterial analytical techniques are in great need.
Barriers and Research Needs
Although nanotechnology-enabled water/wastewater treatment processes have
shown great promise in laboratory studies, their readiness for commercialization
varies widely. Some are already on the market, while others require significant
research before they can be considered for full-scale applications. Their future
development and commercialization face a variety of challenges including technical
hurdles, cost-effectiveness, and potential environmental and human risk. There are
two major research needs for full-scale applications of nanotechnology in water/
wastewater treatment. First, the performance of various nanotechnologies in treating real natural and wastewaters needs to be tested. Future studies need to be done
under more realistic conditions to assess the applicability and efficiency of different
nanotechnologies as well as to validate nanomaterial-enabled sensing technologies.
Secondly, the long-term efficacy of these nanotechnologies is largely unknown as
most lab studies were conducted for relatively short period of time. Research
addressing the long-term performance of water and wastewater treatment nanotechnologies is in great need. As a result, side-by-side comparison of nanotechnologyenabled systems and existing technologies is challenging.
Despite the superior performance, the adoption of innovative technologies strongly
depends on the cost-effectiveness and the potential risk involved. The current cost of
nanomaterials is prohibitively high with few exceptions such as nano- TiO 2 , nanoscale
Current and Potential Applications for Water and Wastewater Treatment