Environmental Engineering Reference
In-Depth Information
2
NaNostructured Metal oxides
for WasteWater disiNfectioN
Erick R. Bandala
1
, Marco Antonio Quiroz Alfaro
2
, Mónica Cerro-López
2
,
and Miguel A. Méndez-Rojas
2
1
Departmento de Ingeniería Química, Alimentos y Ambiental, Universidad de las Américas Puebla, Puebla, Mexico
2
Departamento de Ciencias Químico-Biológicas, Universidad de las Américas Puebla, Puebla, Mexico
2.1
iNtroductioN
Wastewater generation and release into the environment is a major concern because of its impact on surface and underground
water quality. This is particularly important in developing countries where, in many of the cases, domestic and industrial waste-
water is discharged into natural water bodies with improper or no treatment. As an example, in Mexico, the annual production
of both domestic and industrial wastewater is estimated to be as high as 13.5 km
3
/year. Only 30% (about 3.9 km
3
/year) of this
wastewater is treated. The estimated amount of pollutants generated is 9 million tons of BOD
5
per year, with only 20% (1.94
million tons of BOD
5
) being removed [1]
.
There may be many different undesirable consequences associated with the release of such significant amounts of contami-
nants into natural water courses. Among them, probably the most disturbing is the dissemination of pathogenic microorganisms
causing waterborne diseases through the ingestion of wastewater effluents in the water source downstream. The prevalence of
such pathogenic microorganisms in water is probably among the most important human health problems. It is known that
unsafe drinking water is related to millions of deaths yearly (around 1,400,000 yearly worldwide) as a result of waterborne dis-
eases [2, 3]
.
One-sixth of the world's population has been estimated to lack access to water and sanitation services [4] usually
associated with poverty [5]
.
Waterborne diseases affect the poorest sectors of society and are recognized by the United Nations
to be the cause of infections for around one billion people in developing countries [6]
.
Removal of pathogenic microorganisms
capable of causing waterborne diseases has become one of the most important scientific and technological tasks, and many dif-
ferent sanitary engineering processes have been developed for achieving this goal [7, 8]
.
Chlorination is probably the most
widely used cost-effective water disinfecting methodology around the world; nevertheless, in some cases chlorination is not
capable of inactivating these microorganisms, and it has been associated with unpleasant taste and several concerns on the
toxicity of its reaction by-products [9]
.
Among the alternative methodologies developed to generate safe drinking water, advanced oxidation processes (AOPs) have
been identified as emerging technologies for inactivating pathogens in water. Destruction of parasites by applying ozone, ultra-
violet (UV) radiation, and homogeneous and heterogeneous photocatalysis (HP) has been discussed in the past for bacteria,
fungi, viruses, and other highly resistant microorganisms [10-13]
.
Among all these interesting alternatives, HP is the tech-
nology most extensively discussed in the literature [14] for inactivating microorganisms in water.
