238
Introduction
Water is the most essential substance for all life on earth and a precious resource for
human civilization. Reliable access to clean and affordable water is considered one
of the most basic humanitarian goals, and remains a major global challenge for the
twenty-first century. Our current water supply faces enormous challenges, both old
and new. Worldwide, some 780 million people still lack access to improved drinking water sources [1, 2]. It is urgent to implement basic water treatment in the
affected areas (mainly in developing countries) where water and wastewater infrastructure are often nonexistent. In both developing and industrialized countries,
human activities play an ever-greater role in exacerbating water scarcity by contaminating natural water sources. The increasingly stringent water quality standards, compounded by emerging contaminants, have brought new scrutiny to the
existing water treatment and distribution systems widely established in developed
countries. The rapidly growing global population and the improvement of living
standard continuously drive up the demand. Moreover, global climate change accentuates the already uneven distribution of fresh water, destabilizing the supply.
Growing pressure on water supplies makes using unconventional water sources
(e.g., stormwater, contaminated freshwater, brackish water, wastewater, and seawater) a new norm, especially in historically water-stressed regions. Furthermore, current water and wastewater treatment technologies and infrastructure are reaching
their limit for providing adequate water quality to meet human and environmental
needs. Recent advances in nanotechnology offer leapfrogging opportunities to
develop next-generation water supply systems. Our current water treatment, distribution, and discharge practices, which heavily rely on conveyance and centralized
systems, are no longer sustainable. The highly efficient, modular, and multifunctional processes enabled by nanotechnology are envisaged to provide highperformance, affordable water and wastewater treatment solutions that rely less on
large infrastructure [3, 4]. Nanotechnology-enabled water and wastewater treatment
promises to not only overcome major challenges faced by existing treatment technologies, but also provide new treatment capabilities that could allow economic
utilization of unconventional water sources to expand the water supply. Here, we
provide an overview of recent advances in nanotechnologies for water and wastewater treatment. The major applications of nanomaterials are critically reviewed based
on their functions in unit operation processes. The barriers for their full-scale application and the research needs for overcoming these barriers are also discussed. The
potential impact of nanomaterials on human health and ecosystem as well as any
potential interference with treatment processes are beyond the scope of this review
and thus will not be addressed here.
13 Wastewater
Introduction
Water is the most essential substance for all life on earth and a precious resource for
human civilization. Reliable access to clean and affordable water is considered one
of the most basic humanitarian goals, and remains a major global challenge for the
twenty-first century. Our current water supply faces enormous challenges, both old
and new. Worldwide, some 780 million people still lack access to improved drinking water sources [1, 2]. It is urgent to implement basic water treatment in the
affected areas (mainly in developing countries) where water and wastewater infrastructure are often nonexistent. In both developing and industrialized countries,
human activities play an ever-greater role in exacerbating water scarcity by contaminating natural water sources. The increasingly stringent water quality standards, compounded by emerging contaminants, have brought new scrutiny to the
existing water treatment and distribution systems widely established in developed
countries. The rapidly growing global population and the improvement of living
standard continuously drive up the demand. Moreover, global climate change accentuates the already uneven distribution of fresh water, destabilizing the supply.
Growing pressure on water supplies makes using unconventional water sources
(e.g., stormwater, contaminated freshwater, brackish water, wastewater, and seawater) a new norm, especially in historically water-stressed regions. Furthermore, current water and wastewater treatment technologies and infrastructure are reaching
their limit for providing adequate water quality to meet human and environmental
needs. Recent advances in nanotechnology offer leapfrogging opportunities to
develop next-generation water supply systems. Our current water treatment, distribution, and discharge practices, which heavily rely on conveyance and centralized
systems, are no longer sustainable. The highly efficient, modular, and multifunctional processes enabled by nanotechnology are envisaged to provide highperformance, affordable water and wastewater treatment solutions that rely less on
large infrastructure [3, 4]. Nanotechnology-enabled water and wastewater treatment
promises to not only overcome major challenges faced by existing treatment technologies, but also provide new treatment capabilities that could allow economic
utilization of unconventional water sources to expand the water supply. Here, we
provide an overview of recent advances in nanotechnologies for water and wastewater treatment. The major applications of nanomaterials are critically reviewed based
on their functions in unit operation processes. The barriers for their full-scale application and the research needs for overcoming these barriers are also discussed. The
potential impact of nanomaterials on human health and ecosystem as well as any
potential interference with treatment processes are beyond the scope of this review
and thus will not be addressed here.
13 Wastewater