Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 100

potentially remove arsenic from source waters. Treatment options identiied by EPA include
ion exchange, reverse osmosis, activated alumina, nanoiltration, electrodialysis reversal, coag-
ulation/iltration, lime softening, greensand iltration, and other iron/manganese removal
processes, and emerging technologies not yet identiied (USEPA, 2003). New combinations
of materials as sorbents such as granular activated carbon (GAC) supported nano scale zero-
valent iron (nZVI) are being developed (Chowdhury and Mulligan, 2013). Treatment facilities
or alternative water sources are required. We can see that this treatment method, along with
the others do not eliminate the arsenic source before delivery and that other methods must be
developed to accomplish this. Other groundwater methods such as oxidation can lead to the
formation of toxic by-products and sludge. These will require disposal.
Methods for treatment of MTBE include bioremediation, granular activated carbon (GAC),
air-stripping, ozonation, ozone/hydrogen peroxide, or phytoremediation (Richardson, 2003).
These include ion exchange, reverse osmosis, activated alumina, nanoiltration, electro-
dialysis, coagulation/iltration, lime softening, greensand iltration, and other processes.
Thermal techniques include pyrolysis and super critical water oxidation. For a detailed
discussion of standard chemical and biological treatment processes, readers are referred to
various textbooks dealing with wastewater treatment, e.g., Metcalf and Eddy (2003).
Previously, efluent quality was the only basis for evaluating treatment capabilities of
water treatment processes. Capital, energy, nutrient, and other requirements need to be
included to determine if the process under consideration is sustainable for future gen-
erations. Recycling of resources needs to be practiced as much as possible. Mulder (2003)
compared the sustainability of nitrogen removal systems that included (a) conventional
activated sludge systems, (b) an activated sludge system that relies on autotrophic nitro-
gen removal, (c) algal or duckweed ponds, and (d) constructed wetlands (Figure 3.15).
The author used six sustainability indicators: production of sludge, energy consumption,
resource recovery, space requirements, and N 2 O emissions. They determined that the sys-
tem that combines nitriication and anaerobic ammonia oxidation (autotrophic nitrogen
(a)
Inlet pipe
Outlet pipe
Low permeability soil
(b)
Inlet pipe
Outlet pipe
Gravel or soil
FIGURE 3.15
Overview of (a) surface and (b) subsurface low constructed wetlands. (Adapted from adapted from Mulligan,
C.N., Environmental Biotreatment , Government Institutes, Rockville, MD, 395 pp., 2002.)