2.4 Potassium Permanganate, Ferrates, and Ozone
Potassium permanganate is also a strong oxidizing agent that oxidizes iron and
manganese ions and removes odor and taste. It is reported that it has antibacterial
properties against Legionella pneumophila (Yahya et al. 1989). Moreover, it is also
considered as a poor disinfectant because the concentration required to inactivate
microbes is too high (1 g/L). Bromine has the potential to control microbes in places
where a small area is to be disinfected (e.g., swimming pool). It works well by
forming hypobromous acid (HBrO) and other compounds like bromamines, which
can be potent antimicrobial products. The addition of bromine in water disinfection
is costlier than chlorine-based compounds. The main disadvantage is its reactivity
with ammonia or other amines that may hinder its effectiveness. The mechanism
behind the inactivation of microbes is oxidative stress (Taylor and Butler 1982).
Ferrates react with reducing agents and various compounds that can effectively
inactivate microbes (Audette et al. 1971). It is reported that ferrates can kill Pseudomonas over a range of concentrations (0–50 ppm) (Murmann 1975). Interestingly,
zero-valent iron nanoparticles are considered as an alternative to permeable reactive
barriers. It is reported that nanostructured iron adsorbs on the viral capsid, leading to
inactivation (Ryan et al. 2002).
Ozone is one of the strongest disinfectants and oxidants that can remove color and
turbidity and inactivates microorganisms. It is generated by passing dry oxygen or
air through high voltage electrodes. In literature, the inactivation of Salmonella is
reported with a 5 and 6 log removal at a concentration (2 mg/L) after the interaction
time of 45 and 60s, respectively (Jamil et al. 2017).
This process does not produce chlorinated THMs or HAAs, and it reacts with
bromine-containing compounds and forms toxic contaminants like bromate and
brominated organics. Ozone breaks down complex organic molecules, and smaller
size molecules can increase the growth of microbes and disinfection by-products
during the processes. The mechanism behind the inactivation of microbes by ozone
is the attack on the double bonds of the lipid layers in the cell membrane (Smith
1967).
2.5 Coagulation
Coagulation involves the addition of chemicals to remove dissolved and suspended
solids by filtration and sedimentation. The addition of coagulating chemicals (e.g.,
alum) will increase the settling rate of particles by combining smaller particles into
flocs. The required concentration ranges from 10 to 30 mg/L of water. After the
addition of chemicals, at least 30 min is required to settle at the bottom, and then the
clear water above the flocs can be decanted off.
6 Strategies and Limitations of Water Treatment Methods for Point-of-Use. . .
123
Potassium permanganate is also a strong oxidizing agent that oxidizes iron and
manganese ions and removes odor and taste. It is reported that it has antibacterial
properties against Legionella pneumophila (Yahya et al. 1989). Moreover, it is also
considered as a poor disinfectant because the concentration required to inactivate
microbes is too high (1 g/L). Bromine has the potential to control microbes in places
where a small area is to be disinfected (e.g., swimming pool). It works well by
forming hypobromous acid (HBrO) and other compounds like bromamines, which
can be potent antimicrobial products. The addition of bromine in water disinfection
is costlier than chlorine-based compounds. The main disadvantage is its reactivity
with ammonia or other amines that may hinder its effectiveness. The mechanism
behind the inactivation of microbes is oxidative stress (Taylor and Butler 1982).
Ferrates react with reducing agents and various compounds that can effectively
inactivate microbes (Audette et al. 1971). It is reported that ferrates can kill Pseudomonas over a range of concentrations (0–50 ppm) (Murmann 1975). Interestingly,
zero-valent iron nanoparticles are considered as an alternative to permeable reactive
barriers. It is reported that nanostructured iron adsorbs on the viral capsid, leading to
inactivation (Ryan et al. 2002).
Ozone is one of the strongest disinfectants and oxidants that can remove color and
turbidity and inactivates microorganisms. It is generated by passing dry oxygen or
air through high voltage electrodes. In literature, the inactivation of Salmonella is
reported with a 5 and 6 log removal at a concentration (2 mg/L) after the interaction
time of 45 and 60s, respectively (Jamil et al. 2017).
This process does not produce chlorinated THMs or HAAs, and it reacts with
bromine-containing compounds and forms toxic contaminants like bromate and
brominated organics. Ozone breaks down complex organic molecules, and smaller
size molecules can increase the growth of microbes and disinfection by-products
during the processes. The mechanism behind the inactivation of microbes by ozone
is the attack on the double bonds of the lipid layers in the cell membrane (Smith
1967).
2.5 Coagulation
Coagulation involves the addition of chemicals to remove dissolved and suspended
solids by filtration and sedimentation. The addition of coagulating chemicals (e.g.,
alum) will increase the settling rate of particles by combining smaller particles into
flocs. The required concentration ranges from 10 to 30 mg/L of water. After the
addition of chemicals, at least 30 min is required to settle at the bottom, and then the
clear water above the flocs can be decanted off.
6 Strategies and Limitations of Water Treatment Methods for Point-of-Use. . .
123