Environmental Engineering Reference
In-Depth Information
and membrane iltration are the major physical leachate treatment methods; coagulation-
locculation, chemical precipitation, and chemical and electrochemical oxidation meth-
ods are the common chemical methods used for landill leachate treatment [22-27]. Li et
al. [28] reported that ammonium removal can be achieved by chemical precipitation. In
the landill leachate treatment, a 66% COD and 50% ammonia removal were obtained by
nanoiltration [27]. Evaporation and reverse osmosis have been used for the treatment of
industrial landill leachate [29]. Furthermore, combined processes have been successfully
applied together, with coagulation-locculation + biological treatment [30]; photochemical
oxidation + activated sludge; Fe(III) chloride coagulation + photooxidation; and ozonation +
adsorption [31-33]. Several researchers have investigated the eficiency of ozonation for
treating landill leachate [26,34-36]. Activated carbon adsorption systems have also been
used in the treatment of landill leachates for removal of dissolved organics; however, most
of these techniques are generally considered expensive treatment options and often must
be combined with other treatment technologies to achieve desired results.
37.1.4 Nanomaterials in Leachate Treatment
Most commonly encountered engineered nanoparticles (ENPs) fall into one of the follow-
ing categories: carbonaceous nanoparticles, metal oxides, quantum dots, zerovalent metals,
and nanopolymers, with new products gradually being added to the list. Presently, ENPs
are widely used in many applications, including wastewater and polluted plumes treat-
ments and hazardous waste treatment, owing to the unique sorptive and reactive proper-
ties that contribute for eficient treatment or degradation of contaminants [37]. Mainly, these
nanomaterials possess unique atomic structure and distinctive chemical (such as behavior
of excellent electron donor) and mechanical or physical properties (such as large surface-
to-volume ratio involved in surprising surface and quantum effects or sorptive properties)
[37]. This may be due to the small particle size (<100 nm) that falls in the transitional zone
between individual atoms or molecules and the corresponding bulk material, which can
modify the physicochemical properties of the material (e.g., performing exceptional feats of
conductivity, reactivity, and optical sensitivity). For instance, nanoscale particulates such as
nano-zerovalent iron (NZVI), iron oxide (γ-Fe 2 O 3 , Fe 2 O 3 ), silver, and gibbsite particulates are
used for wastewater treatment purposes [38-42]. Among these materials, NZVI has been
tested widely for a wide range of pollutant plumes and contaminated sites.
Nanosized particles that can degrade a wide range of hazardous pollutants are suc-
cessfully used for environmental remediation [43]. To date, large-scale treatment plants
incorporated with zerovalent iron (ZVI) (i.e., iron shavings) can be applied to industrial
wastewater treatment [44]. However, comparative studies have shown that nanoparticu-
late (<100 nm) zerovalent iron (NZVI) degrades contaminants more effectively than ZVI
with micron-sized particles [45]. Different approaches have been used to bring ZVI in con-
tact with contamination. These include construction of permeable reactive barriers (PRBs),
into which contaminants low, and in situ injection, where ZVI is delivered actively to the
plume. The in situ injection of NZVI has shown signiicant eficiency with low operating
costs compared with conventional ZVI PRBs [37,46]. Figure 37.1 shows a typical PRB system
that is used for removing contaminants from groundwater.
These nanoparticles immobilize heavy metals such as Cr(VI) and As(V), chlorinated hydro-
carbons such as trichloroethene and pesticides (DDT, chlorpyrifos, lindane, etc.), and nutri-
ents (nitrates, phosphates, etc.) [38,47-49]. Although signiicant numbers of publications in the
ield of pollution prevention using nanomaterials are reported, the use of nanomaterials in
landill leachate treatment is still lacking. A few studies have demonstrated the use of NZVI
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