Advanced technologies such as phytoremediation, bioremediation, and artificially
constructed wetlands are also effective strategies for As remediation (Bundschuh
et al. 2010). Apart from this, deep tube wells, artificial groundwater recharge, surface
water sources, rainwater harvesting systems, and digging of wells gained a marked
degree of success in As amelioration technologies (Kabir and Howard 2007;
Shibasaki et al. 2007; Shafiquzzaman et al. 2009; Bundschuh et al. 2010; Mosler
et al. 2010). In southern parts of Bangladesh and many states of India, the rainwater
harvesting is still a common practice. In Mizoram, almost 90% households use
rainwater for drinking and cooking as a potential strategy to minimize arsenic
toxicity. Government agencies such as Central Groundwater Board-Mid Eastern
Region (CGWB-MER), Public Health Engineering Department (PHED) as well as
UNICEF have started As mitigation programs (CGWB and NIH 2010).
Government of India (GoI) initiated As mitigation technologies include arsenic
removal plants (ARP), new hand pumps (NHP), arsenic treatment units (ATU), and
new tube wells with stand post (NTWSP) (CGWB and NIH 2010).
Phytoremediation is also an effective strategy for As and fluoride removal. Plants
have evolved an extraordinary potential to remediate As through strategies including
uptake, repression, sequestration into vacuoles or extrusion. Arsenic removal plants
will not be effective until they are not managed and maintained properly and there is
an urgent need of political and people’s participation. These proposed arsenic
mitigation interventions will benefit millions of people, whether directly or indirectly
(CGWB and NIH 2010).
5.4.1 Precipitation Processes
For As removal, precipitation is an effective method. Precipitation involves coagulation, coagulation-assisted microfiltration, filtration, and enhanced lime softening.
Coagulation of As with salts of iron and aluminum and softening with lime is the
most effective treatment. Adsorption co-precipitation with hydrolyzing metals such
as iron and aluminum is the effective technique for groundwater As removal.
Sedimentation is followed by rapid sand filtration or microfiltration to remove the
precipitates (Mishra et al. 2016). In this method of As removal, oxidation of AsIII to
AsV is necessary to improve the efficiency of this method. Hypochlorite and
permanganate are commonly used for the oxidation of As. The examples of major
techniques used for As removal based on precipitation process are fill and draw
treatment unit, bucket treatment unit, iron As treatment unit, and tube well-attached
As treatment.
5.4.1.1 Fill and Draw Units
This treatment unit is based on the precipitation method. Fill and draw treatment unit
has good capacity to store water with slightly tapered bottom. The water
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S. Awasthi et al.
constructed wetlands are also effective strategies for As remediation (Bundschuh
et al. 2010). Apart from this, deep tube wells, artificial groundwater recharge, surface
water sources, rainwater harvesting systems, and digging of wells gained a marked
degree of success in As amelioration technologies (Kabir and Howard 2007;
Shibasaki et al. 2007; Shafiquzzaman et al. 2009; Bundschuh et al. 2010; Mosler
et al. 2010). In southern parts of Bangladesh and many states of India, the rainwater
harvesting is still a common practice. In Mizoram, almost 90% households use
rainwater for drinking and cooking as a potential strategy to minimize arsenic
toxicity. Government agencies such as Central Groundwater Board-Mid Eastern
Region (CGWB-MER), Public Health Engineering Department (PHED) as well as
UNICEF have started As mitigation programs (CGWB and NIH 2010).
Government of India (GoI) initiated As mitigation technologies include arsenic
removal plants (ARP), new hand pumps (NHP), arsenic treatment units (ATU), and
new tube wells with stand post (NTWSP) (CGWB and NIH 2010).
Phytoremediation is also an effective strategy for As and fluoride removal. Plants
have evolved an extraordinary potential to remediate As through strategies including
uptake, repression, sequestration into vacuoles or extrusion. Arsenic removal plants
will not be effective until they are not managed and maintained properly and there is
an urgent need of political and people’s participation. These proposed arsenic
mitigation interventions will benefit millions of people, whether directly or indirectly
(CGWB and NIH 2010).
5.4.1 Precipitation Processes
For As removal, precipitation is an effective method. Precipitation involves coagulation, coagulation-assisted microfiltration, filtration, and enhanced lime softening.
Coagulation of As with salts of iron and aluminum and softening with lime is the
most effective treatment. Adsorption co-precipitation with hydrolyzing metals such
as iron and aluminum is the effective technique for groundwater As removal.
Sedimentation is followed by rapid sand filtration or microfiltration to remove the
precipitates (Mishra et al. 2016). In this method of As removal, oxidation of AsIII to
AsV is necessary to improve the efficiency of this method. Hypochlorite and
permanganate are commonly used for the oxidation of As. The examples of major
techniques used for As removal based on precipitation process are fill and draw
treatment unit, bucket treatment unit, iron As treatment unit, and tube well-attached
As treatment.
5.4.1.1 Fill and Draw Units
This treatment unit is based on the precipitation method. Fill and draw treatment unit
has good capacity to store water with slightly tapered bottom. The water
112
S. Awasthi et al.