Encyclopedia of Environmental Science and Engineering, Volume I and II

984 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS

this area. A review on the use of ferrate (VI) salt as a coagu-

lant and oxidant for water and wastewater treatment is pre-

sented by Jiang and Lloyd (2002). In this paper the authors

demonstrate the advantages of this approach in the treatment

of microorganisms, heavy metals, and SS, as well as present

the difficulties associated with this technique.

Ghoreishi and Haghighi (2003) propose a combined

bisulfite catalyzed sodium borohydride reduction followed

by activated sludge for the treatment of nonbiodegradable

textile effluent, reposting reductions of BOD, COD, and

TSS of 74–88%, 76–83%, and 92–97% respectively. Lin and

Wang (2004) investigated the performance of a proposed

granulated activated carbon bed combined with ozonation

and preceded by chemical coagulation, obtaining interest-

ing results. Akcil (2003) discusses the advantages of using

biological methods for the treatment of cyanide in gold-mill

effluents as compared to well-established chemical meth-

ods. Chung et al. (2003) evaluated the performance of a

combined chemical absorption–biological oxidation system

for the removal of H 2 S from gaseous streams such as those

produced by livestock wastewater-treatment plants. They

demonstrated the potential of this technique and obtained

reductions on the order of 85%. Another combined approach

is presented by Libra and Sosath (2003). In this case they

used ozonation followed by a biological process for the treat-

ment of textile wastewater, comparing two configurations

of treatment processes, concluding that the most attractive

alternative is the simplest: ozonation followed by aerobic

treatment as compared to anaerobic, aerobic, ozonation, and

aerobic treatments for their effluent and conditions.

A comprehensive review on the properties of alumina,

the chemical reactions involved in its use in water treatment,

and adsorption and catalysis using alumina was published

by Kasprzyk-Hordern in 2004. An interesting review on the

enhancement of biodegradability of industrial wastes by

chemical-oxidation pretreatment is presented by Mantzavinos

and Psillakis in 2004. This exhaustive review includes many

different pollutants, trends, and process schemes used as

segregation by effluent type; evaluation of the pretreatment

steps; and modeling of the individual steps involved.

Aiyuk et al. (2004) propose a chemically enhanced pri-

mary treatment followed by a UASB reactor for the treatment

of domestic wastewater. The chemical pretreatment consisted

of the addition of FeCl 3 or Al 2 (SO 4 ) 3 and polymers in a mixing

tank, and a posttreatment of the biologically treated water was

achieved by zeolite adsorption for NH 4  removal. Another

combined solution was proposed by Bressan et al. in 2004.

This approach includes the use of an enhanced Fenton process

followed by biological treatment of olive-mill wastewater.

Oxidative, Photochemical, and Electron-Beam

Processes

Oxidizing agents like chlorine, ozone, hydrogen peroxide,

potassium permanganate, and ultraviolet irradiation have been

used successfully in oxidizing and stabilizing certain impu-

rities like hydrogen sulfide, phenol, cyanide, and selected

refractory organic substances. The reaction of chlorine with

certain organic matter present in wastewater to form a more

harmful persistent chemical has raised a serious question

of continuing the use of chlorine for disinfection of waste-

water effluents. Ozone is gradually becoming more popular,

because it has strong oxidizing and disinfecting capacity and

leaves no harmful residuals. It has been shown that ozone

in combination with photochemical oxidation economically

removed inorganic, organic, and toxic refractory species and

effectively destroyed phenol in a bubble column or a stirred

cell (Wall, 1980; Otake, 1979). Ganes and Staubach (1980)

have reported the kinetics of the reaction between ozone and

nitrilotriacetate in water and the effects of pH, metal content,

and natural organics on the rate and extent of degradation.

In 1993, Legrini et al. published an extensive review

on photochemical processes for water treatment, including

UV, H 2 O 2 /UV, ozone/UV, O 3 /H 2 O 2 /UV, TiO 2 /UV, vacuum

UV, photochemical electron-transfer processes, and energy-

transfer processes. In 1999, Andreozzi et al. published studies

on the use of O 3 /UV and O 3 /H 2 O 2 for the treatment of mineral-

oil-polluted wastewaters, performing different experiments

and achieving an 80 to 90% reduction of COD for the O 3 /UV

treatment (Andreozzi et al., 1999). A discussion of the different

advanced oxidation processes (AOP), as well as experimental

apparatus and working procedures for the study of the applica-

tion of this technique, is presented in Andreozzi et al. (2000).

An extensive review on photocatalytic degradation was

presented by Bhatkhande et al. (2001). In it they include

a description of the process, the mechanisms implied, the

compounds that can be degraded with it, and the variables

that can affect this technique. Another review was pub-

lished by Kabra et al (2004), concluding that this process

can be used to treat industrial wastewater for the removal

of metal ions and nonbiodegradable organics. Another con-

clusion is that the costs of this method are slightly higher

than for conventional methods, but that future research can

make a competitive option. An interesting article on the

evaluation of the use of peracetic acid for the disinfection of

the effluent of Montreal’s wastewater-treatment plant was

FIGURE 4 Conventional DAF unit with water recycle

to the saturator (From Rubio et al., 2002, with permission

from Elsevier).

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