Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 99

3.4.1.10 Ex Situ Processes

For extracted groundwater, treatment is required before discharge or utilization of the
abstracted groundwater as drinking water. These techniques are usually quite extensive,
involving extraction of substantial groundwater. Standard physical, chemical, or biologi-
cal wastewater treatment techniquesare utilized. Physical-chemical techniques include
physical and/or chemical procedures for removal of the contaminants including precipita-
tion, air stripping, ion exchange, reverse osmosis, electrochemical oxidation, etc.
Techniques for groundwater treatment for arsenic and waste considerations are high-
lighted in Table 3.1. Treatment methods need to minimize the wastes produced to ensure
that these processes are sustainable. To evaluate the sustainability of these methods, several
factors including materials, energy, transportation, and waste management requirements
for the treatment process need to be taken into consideration. One of the principal methods
is ion exchange. However, in some cases, simple ion exchange techniques are insuficient.
An example of this is As(III). Oxidation of this form to As(V) must be required and per-
formed with a preoxidation ilter. Although this method is highly eficient, disposal of a
toxic arsenic waste from the regeneration of these ilters and the ion exchange resins as
a result of the water treatment procedures impacts the sustainability of these processes.
These puriication activities generate signiicant wastes that can severely impact the envi-
ronment, causing more harm than good. Due to the problems of arsenic in the groundwa-
ter, economic solutions need to be found to ensure the safety of the drinking water.
Several common treatment technologies are used for removal of inorganic contaminants,
including arsenic, from drinking water supplies. Large-scale treatment facilities often use
conventional coagulation with alum or iron salts followed by iltration to remove arsenic.
Lime softening and iron removal also are common, conventional treatment processes that can

TABLE 3.1
Comparison of Technologies for the Remediation of Arsenic Contaminated Groundwater

Technology Waste Stream Treatment of Waste Disposal Options

Coagulation/iltration Ferric sludge, redox

sensitive, 97% water
content

Dewatering and drying Landill after dewatering,

brick manufacture (Rouf
and Hossain, 2003)

Activated alumina with
regeneration

Alkaline and acidic
liquids

Neutralization and
precipitation with
ferric salts

Sewer, residual into
landill

Iron oxide ilters Exhausted adsorbent,

redox sensitive, <50%
solids, passes TCLP
test a

No treatment Landill, immobilization,

brick manufacture (Rouf
and Hossain, 2003)

Ion exchange Liquid saline brine Precipitation with ferric

salts

Sewer, brine discharge,
landill for residual,
possible recycling of
brines

Membrane techniques
such as reverse osmosis
or nanoiltration

Concentrated liquids None performed Sewer or brine discharge

Source: Adapted from Driehaus, W., Technologies for arsenic removal from potable water. In J. Bundschuh,
P. Bhattacharaya, and D. Chandrasekharam (eds.), Natural Arsenic in Groundwater: Occurrences, Remedia-
tion and Management , Taylor & Francis, London, pp. 189-203, 2005.
a TCLP refers to the Toxicity Characteristic Leaching Procedure (see Figure 7.4 and discussion in Section 7.3.5 in
Chapter 7).