Membrane and Desalination Technologies - TCE Moodle Website

610 P. Kajitvichyanukul et al.
UV irradiation with lamps is another disinfection technique using a similar mechanism in
destroying pathogenic microorganisms. This method is well known for its performance in
inactivating two waterborne, chlorine-resistant protozoans, Cryptosporidium parvum oocysts
and Giardia lamblia cysts. To obtain high performance of this method, low turbidity of water
is required.
(2) Chemical treatment
Among several chemicals, free chlorine is the most widely used in POU/POE system. This
chemical can destroy various types of waterborne pathogens except Cryptosporidium parvum
oocysts and the Mycobacteria species (15). The taste and odor problems cause low socio-cultural
acceptation of this method.
(3) Filtration
Several types of filtration have been used to remove various types of pathogens. These methods
are biosand filtration and fiber or fabric filtration (2). Biosand filter is the sand filter with a
bioactive layer that can eliminate pathogens such as bacteria and protozoa. This filtration process
has relatively low performance in destroying viruses.
Fiber or fabric filters are commonly used in the removal of large waterborne pathogens, such as
free-swimming larval forms of Schistosomes and Faciola species, guinea worm larvae within
their intermediate crustacean host, and bacterial pathogens associated with relatively large
copepods and other zooplanktons in water, such as the bacterium Vibrio cholerae (2, 3, 16,
17). This filter has limitation in removing viruses, bacteria, and smaller protozoan parasites (17).
(4) Membrane filtration Membrane filtration is the most widely used treatment method for drinking
water, especially in POU/POE system. This method provides superb advantage as an absolute
barrier for pathogens and suspended solids or turbidity. In comparison to other conventional
water treatment methods, this process can treat water in one step without the addition of
chemicals. Membrane systems used in POU/POE system include ultrafiltration (UF), microfiltration
(MF), nanofiltration (NF), and RO. Summary of available POU/POE water treatment
technologies for developing and transition countries is presented in Table 14.4. Among these
membranes, RO is the most recognized system at the industrial level (1). Details of fundamental
concept, type, composition, operation and maintenance, and design of RO are described in the
next section.
3. REVERSE OSMOSIS IN POU/POE SYSTEM
3.1. Application of Reverse Osmosis in POU/POE
Reverse osmosis is one type of membrane filtration that is widely used in drinking water
treatment. The RO water treatment method has been used comprehensively to convert
brackish or seawater to drinking water (18–21), to clean up wastewater (22–24), and to
recover and treat water from industrial processes (25–29). Nowadays, RO is becoming more
popular as the household water treatment method for the direct consumption of water, such as
for drinking and cooking purposes. Owing to the increasing concern about contaminants that
affect human health, as well as non-hazardous chemicals that affect the taste, odor, or color of
drinking water, RO has become a common method for the treatment of household drinking
water supplies.