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159A.T. Atimtay and S.K. Sikdar (eds.), Security of Industrial Water Supply and Management,NATO Science or Peace and Security Series C: Environmental Security,DOI 10.1007/978-94-007-1805-0_11, Springer Science+Business Media B.V. 2011

Abstract As globalization continues, and the earths natural processes transormlocal problems into international issues, ew societies are being let untouched bymajor environmental problems. Water-our most precious natural resource-is beingthreatened by a multitude o contaminants (toxic metals, recalcitrant organiccompounds, pathogenic microorganisms), resulting in an unprecedented watercontamination crisis with local and national implications. The research communityproposes dierent solutions or this problem, some o them have been appliedsuccessully or dierent environmental water/wastewaters problems, considered as

the Best Available Technologies. However, the concept o best available technologiesmust be considered in addition to technical easibility and costs, potential trade-osbetween environmental issues, in order to avoid creating a new and more seriousenvironmental problem when solving another. Thereore, research o EnvironmentalFriendly Technologies, considering a complete environment assessment, will be theuture o the water/wastewater treatment technologies. Under these circumstances,during the last 6 years, the environmental research group rom Laboratory oSeparation and Reaction Engineering (LSRE) has been ocused on bring otherperspectives to best available technologies or wastewater treatment and reuse,

including the use o low cost materials, e.g. algal biomass and industrial wastes ortoxic metal ions removal, and the use o solar radiation, as UV photon source, ordisinection o water by photocatalytic processes or detoxication o wastewatersusing the combination o these processes with biological oxidation ones.

V.J.P. Vilar (*) C.M.S. Botelho R.A.R. BoaventuraLSRE Laboratory o Separation and Reaction Engineering, Department o ChemicalEngineering, Faculty o Engineering, University o Porto, Rua Dr. Roberto Frias,Porto 4200465, Portugale-mail: [email protected]

Chapter 11

Environmental Friendly Technologies

for Wastewater Treatment: Biosorptionof Heavy Metals Using Low Cost Materialsand Solar Photocatalysis

Vtor J.P. Vilar, Cidlia M.S. Botelho, and Rui A.R. Boaventura

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160 V.J.P. Vilar et al.

Keywords Biosorption Heavy metals Solar photocatalysis Water disinfection

Compound parabolic collectors Environmental friendly technologies

Detoxication of wastewaters

11.1 Introduction

Nowadays it is well known that heavy metals escaping into the environment pose aserious health hazard because they accumulate in living tissues throughout the oodchain. The Decision No 2455/2001/EC o the European Parliament and o theCouncil o 20 November 2001 established a list o priority substances in the eld owater policy, where toxic metals are included. The main metal pollution sources o

emissions in Portugal are the metal plating and battery industries and oil reneriesand smelters. Conventional treatment technologies o metal bearing industrial efu-ents are precipitation, oxidation/reduction, adsorption onto activated carbon,ion-exchange, evaporation and electrochemical treatment [16]. As these processesgenerate high volumes o toxic sludge or are expensive (high energy consumption,operation and investment costs) or not eective enough, there has been an increas-ing demand or ecient, particularly cost-eective and ecoriendly alternatives.Biosorption promises to ulll the requirements, principally or the treatment odilute metal solutions, in the range o low hundreds o mg L1 or less. Biosorption is

a passive process o metal uptake whereby the metal is sequestered by chemicalsites naturally present and unctional even when the biomass is dead [75]. A uniqueand ubiquitous type o macroscopic biomass known or its metal-sorbing potentialis seaweeds. Seaweed biomass has a certain rigid macro-structure o its own and, insome instances, it has been revealed to oer excellent metal-sorbing properties [15].At certain ocean locations, seaweeds are plentiul and very ast growing, as orexample in the 1,230 km o the Portuguese coast, with dierent species o algae. Atsome locations, they threaten the tourism industry by spoiling pristine environmentsand ouling beaches. For example, the invasion o Ria Formosa (Faro, South o

Portugal) by macro-algae Sargassum muticum has been causing a serious problemto the ecosystem. Turning seaweeds into a resource can be quite benecial to somelocal economies. The renewable character o the macro-algae makes it an inexhaust-ible resource or the biosorption application in ull-scale.

Dierent brown macro-algae, Pelvetia c.,Laminaria h.,Ascophyllum n., Fucus s.,Sargassum m. and Gelidium s. harvested in the north coast o Portugal were used asbiosorbents or Cu(II), Pb(II), Zn(II), Cd(II), Ni(II) and Cr(III) removal [21, 66](Fig. 11.1).The maximum biosorption capacities ound or Pelvetia c., at pH 5.0without pre-treatment, were 1.24 (Cu), 0.96 (Pb), 0.91 (Zn), 0.79 (Cd) and 0.71 (Ni)

mmol g1

[21]. However, ater a pre-treatment with an acid solution ollowed by acalcium solution (Fig.11.1), the Ca-biomass was able to accumulate up to 1.45 mmolo lead per gram o biosorbent (more than 50%) [14].

Dierent kinds o equilibrium models have been used to describe biosorption equilib-rium data, as Langmuir [36], Freundlich [22], Langmuir-Freundlich combination [60],

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16111 Environmental Friendly Technologies or Wastewater Treatment

Redlich-Petterson [53], Brunauer et al. [12], Radke and Prausnitz [52], and others.As these equilibrium models, in their simple orm, do not consider the heterogene-ity o the binding sites, the infuence o pH on the biosorption process and hardlyrefect the sorption mechanism, continuous anity distribution equilibrium models,considering a complexation mechanism and non ideal competitive adsorption(NICA) have been used successully to describe biosorption o Cu(II), Pb(II) andCd(II) by raw algae Gelidium s. [66, 68, 71], showing that Cu(II) presents a narrowdistribution o the anity constant, while Pb(II) and Cd(II) present a wider distribu-tion o the same constant. Metal ions act as Lewis acids by accepting electron pairs

rom ligands. Class A metal ions, also called hard or nonpolarizable, preerentiallyorm complexes with similar nonpolarizable ligands, particularly oxygen donors,and the binding is mainly ionic. Class B or sot metal ions preerentially bind topolarizable sot ligands (S), to give a rather more covalent bonding [49]. Lead, cop-per and cadmium ions are considered as borderline metals. The anity increases inthe ollowing order Cd(II) < Cu(II) < Pb(II) or algae Gelidium s. [69]. The covalentindex (product o the electronegativity square by the sum ionic radius + 0.85, whichis an appropriate constant assumed to refect the radius o O and N donor atoms)also increases in the order: Cd(II) (5.20) < Cu(II) (6.32) < Pb(II) (6.61) [47]. In gen-

eral, the greater the covalent index o a metal ion, the greater its Class B character,and consequently its potential to orm covalent bonds with biological ligands.The biosorption mechanism or lead uptake in algae Pelvetia c. loaded with

calcium was identied as ion exchange between calcium, lead and hydrogen ions,with a stoichiometry 1:1 (Ca:Pb) and 2:1 (H:Ca or H:Pb). Lead ions showed higher

Fig. 11.1 Scheme o algae preparation procedure

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anity than hydrogen and calcium ions to the carboxylic groups, as indicated by

the respective selectivity constants o the mass action law (aCaPb = 44 5, aCaH = 91and a

HPb = 51) [14]. These values also shows that lead ions bind more easily to the

biomass pre-treated with calcium ions than hydrogen ions, since the last ones bindmore strongly to the carboxylic groups present in the surace o the biosorbent.Similar results were also obtained by other authors [58, 82]. A mathematical modelusing the Nernst-Planck approximation or the ionic fux o counter-ions, takinginto account the intraparticle diusion resistance and the infuence o the electriceld in the biosorbent was able to predict the kinetic behavior in batch and columnsystems [14]. Fourier Transorm Inrared Spectroscopy (FTIR) analyses have shown

a complex nature o the biomass and provided inormation about predominant bind-ing groups present on the surace o the algae, as carboxylic groups (Pelvetia c.-alginic acid: mannuronic and guluronic acids; Gelidium s.-agaropectin: D-glucuronicacid, Pyruvic acid), hydroxyl groups (Pelvetia c. -mannitol, laminaran and cellu-lose; Gelidium s.-agarose, Floriden starch, cellulose) and sulphate ester groups(Pelvetia c.-ucoidan; Gelidium s.-sulated galactans) (Figs. 11.2 and 11.3).

Potentiometric acid-base titrations showed a heterogeneous distribution o thetwo major binding groups, carboxyl and hydroxyl, ollowing a Quasi-Gaussiananity constant distribution [60], which permitted to estimate the maximum amount

o acid unctional groups (2.8 and 0.36 mmol carboxylic groups/g respectively oralgae Pelvetia c. and Gelidium s.) and proton binding parameter (pKcarboxylic groups

= 3.5and 5.0, respectively or algae Pelvetia c. and Gelidium s.) [14, 72].

The adsorption capacity o the brown algal material is directly related to the pres-ence o the carboxylic sites on the alginate polymer (up to 40% o dry weight, [50]

0

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0.2

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600110016002100260031003600

Absorbance

Wavenumber (cm-1)

Raw Pelvetia

Raw Gelidium

R-OH

R-OH

R-COOH

CH

Fig. 11.2 Inrared spectroscopy o algae Gelidium s. and Pelvetia c.

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o the dried seaweed biomass). Furthermore, the majority o metals o interest(i.e. Cd(II), Cu(II), Ni(II), Pb(II)) show maximal, or near maximal, sequestration atpH near the apparent dissociation constant o the carboxylic acids observed in algalbiomass (pK

aaround 45), although or low pH values (< 2.5), the biosorbents

reveal competitive adsorption capacities when compared with the ion exchange res-ins, which are in the same way aected by the pH, but has a price ten times higherthan the biosorbents. Moreover, the biosorption technology is normally used as apolishing step in wastewater treatment with a metal concentration between 1 and100 mg L1. As the majority o metal contaminated efuents present high metal

concentrations, its necessary to carry out a pre-treatment, normally chemicalprecipitation, ater which the pH o the efuent is neutralized. So, the subsequenttreatment, using the biosorption process, will be not aected by the alkaline precipi-tation pH. The role o carboxylic groups in the adsorption process has been clearlydemonstrated by a reduction in cadmium and lead uptake by dried Sargassum bio-mass ollowing partial or complete esterication o the carboxylic sites [20]. FTIRspectral analyses have shown that ater Pb biosorption onto algae Pelvetia c., thepeak related to C-O stretch o COOH disappeared (Fig. 11.4) [14] and Cd biosorp-tion to Sargassum arises rom bridging or bidentate complex ormation with the

carboxylate groups o the alginate [20].The second most abundant acidic unctional group is the sulonic acid o ucoidan.Sulonic acid groups typically play a secondary role, except when metal bindingtakes place at low pH. Hydroxyl groups are also present in all polysaccharides butthey are less abundant, and only become negatively charged at pH > 10, so, they are

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2.5

3.0

3.5

0 2 4 6 8 10 12

F(mmol/g)

QH(mmol/g)

pH, log(Ki,Hint)

R-OH

R-COOH

Fig. 11.3 Experimental data and model curves or biosorbent potentiometric titrations and anitydistribution unction or hydrogen ions. ____, __ __ Continuous model; , __ __ __ __ Sips distributionor a IS = 0.1 M. respectively or Algae Pelvetia c. and Algae Gelidium s.

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less relevant or metal binding at low pH. The titration curves are not aectedsignicantly by the salinity or ionic strengths between 0.005 and 0.1 M, which areusual in the majority o the industrial efuents [14, 72]. This result reveals that thepolyelectrolyte eect is small leading to the conclusion that the charges are wellspaced (distance larger than the Bjerrum length) [10].

I the biosorption process is to be used as an alternative in wastewater treatment,the biosorbent regeneration is important to keep low processing costs and open thepossibility to recover the extracted metal(s). The desorption process should yieldmetals in a concentrated orm, which acilitates disposal and restores biosorbent oreective reuse [77, 78]. The desorption mechanism is similar to ion exchange. Thebiomass stripping can be achieved with inexpensive acids such as HCl, HNO

3and

H2SO4 [2, 35, 65] and EDTA as metal chelating agent [62, 64, 81, 84]. Desorption odierent metal ions rom dierent brown algae has been completely achieved at pH 1[21, 67]. An intermediate conditioning step is normally used ater desorption andbeore the next adsorption cycle, whereby the protons binding to the active sites(ater acidic desorption) are replaced by Ca2+. Multiple reuses o the active sorbentparticles in consecutive adsorption/desorption cycles have been perormed withoutany loss in the uptake capacity, which greatly increases the process economy [70].Although dierent kinds o biosorbents have been tested to remove several metals[5, 8] only ew have been commercialized [4, 24, 75, 76, 78]. Despite the simplicity

o the biosorption process, the technology is not yet established and it requirescontinued Research and Development (R and D) eorts at pilot-scale, using realmetal bearing efuents.

0

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Wavenumber (cm-1)

Raw algae

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Fig. 11.4 Inrared spectroscopy o algae raw Pelvetia c. and saturated with Pb

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11.2 Solar Photocatalysis

Nowadays, the elimination o recalcitrant, non-biodegradable organic chemical

compounds is one o the most important problems in the treatment o efuentsderiving rom industrial applications (textile, winery, cork, etc.) and also as a resulto the agricultural exploration and domestic use (pesticides, ertilizers, detergents,etc.). On the other hand, the reuse o wastewater ater adequate polishing step con-stitutes a potential water resource, which could be o great interest to several activities,such as agriculture, especially in countries suering rom a deciency in waterresources. More than 200 dierent chemical compounds many o which may beacutely or chronically toxic to aquatic organisms and may pose a health risk to manand animals alike, since they are not easily degraded have been identied in sec-

ondary efuents o municipal Wastewater Treatment Plants (WWTP). Additionally,environmental regulations are getting stringent and with the introduction o EUWater Framework Directive in 2000 [48], secondary sewage efuent (SSE) was nolonger a guarantee or discharge [33]. Advanced tertiary treatment is thereorerequired or urther removal o the residual constituents in SSE, especially nearsensitive areas. The search o eective methods to remove these compounds is oglobal interest in order to ulll the discharge regulations and, particularly, to allowwater recycling.

Advanced Oxidation Processes (AOPs) are an emergent and promising method-ology or the degradation o persistent environmental pollutants, reractory to otherdecontamination/remediation treatment processes. In the near uture, AOPs maybecome the most widely used water/wastewater treatment technologies or organicpollutants which cannot be removed by conventional techniques, due to their highchemical stability and/or low biodegradability [26, 27]. AOPs involve generationand subsequent reaction o hydroxyl radicals ( O ), which are one o the mostpowerul oxidizing species. Their attack is not very selective, which is a useulattribute or use in pollution treatment. Many oxidation processes, such as TiO

2/

UV, H2O

2/UV, photo-Fenton and ozone (O

3, O

3/UV, O

3/H

2O

2) are currently employed

or this purpose and their versatility is enhanced by the act that there are many di-erent

HO radical production possibilities. The use o AOPs or wastewater treat-ment has been studied extensively, but ozone production or UV radiation generationby lamps are expensive processes [46], and, in the latter case, uture applicationscan only be economically envisaged through the use o solar energy. So, research isocusing more and more on those AOPs which can be driven by solar irradiation,such as photo-Fenton and heterogeneous catalysis with TiO

2. Several photocatalysis

reviews have been published during the last years [7, 30, 38]. It has been demon-strated that the photo-Fenton reaction is more ecient or the treatment o dierentrecalcitrant pollutants [17, 37] than TiO

2, since the reaction rate is much higher and

very low iron concentrations are enough or promoting wastewater treatment. Thisis very helpul because removal o iron at low concentrations will not be necessarybeore disposal. The advantage o the photo-Fenton process is the higher light

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sensitivity up to 580 nm, corresponding to 35% o solar radiation spectrum, whencompared with5% or TiO

2photocatalysis.

Apart rom developments increasing the reaction rate, the most importantprogress in solar photocatalysis in recent years has been related to its combinationwith biological treatment techniques, which proved to be successul in decreasingtreatment time (i.e. plant size) and consequently increasing the overall processeciency [19, 39, 57].

The southern European countries, due to their high average number o sun hoursare very prone to the application o solar photocatalytic technologies. Besides,Spain has been the rst country that has built a commercial photocatalytic solarplant (Albaida) where, in a eld o 150 m2 o compound parabolic collectors (CPCs),is perormed the wastewater treatment rom a pesticide containers plastic recoveryacility (treatment capacity: 21,600 ton year1). In Spain is also ound, at DSM-

Deretil company, a demonstration plant or the treatment o wastewaters containingpharmaceuticals in a sequential chemical-biological process using photo-Fentonphotocatalytic technology in a eld o 100 m2 o CPC (treatment capacity: 6.3 m3day1 in the solar eld).

Portugal is the world leader in cork production and manuacturing, harboringabout 800 industrial acilities and employing 12,000 people in 2009 [3]. The corkproduction process (Quercus suber L.) ollows a series o steps: preparation o thecork barks (stabilization, boiling and fattening), production o the cork stoppers(cutting into strips, punching out the stoppers), and their nal treatment or launching

in the market (disinection, drying, sorting and packing). This process creates twotypes o wastewaters: the cork boiling wastewater (CBW) and the cork bleachingwastewater (CLW) [73].

The CBW consists o a dark liquor, o around 400 L per ton o prepared cork,that is produced ater the repeated boiling o cork in water (around 2030 times orthe same batch o water) [44]. This wastewater has a high non-biodegradable organicload and is rich in phenolic acids and polyphenols [31]. The CLW is produced in thedisinection o the cork stoppers in a volume o around 400 L per 50,000 stoppers(and 1 ton o cork = 75,000 stoppers, approximately). The most common reactant

used in the bleaching process is hydrogen peroxide, which concentration can rangerom 0.7 to 7.7 g L1 in the nal wastewater, depending on the industrial process.CLW has a lower organic load than CBW but is equally non-biodegradable [73].

Previous studies rom Silva et al. [59] and Vilar et al. [73] have concluded thatheterogeneous photocatalysis with TiO

2is inecient in treating CBW in a short

period o time. However, photo-Fenton and solar-photo-Fenton showed improvedresults rom Fenton alone. Moreover, photo-Fenton can make use o the high con-centration o hydrogen peroxide o CLW or its treatment. Pintor et al. [51] showedthat is possible to perorm the decontamination o CBW and CLW simultaneously,

using CLW as a H2O2 source in solar-photo-Fenton treatment o CBW, modeling theAOP as a pre-oxidation step beore a traditional biological treatment. This methodproved to be ecient, achieving mineralization rates higher than 90% or dierentiron concentrations. Lower energy consumption was achieved or higher ironconcentrations, and 60 mg L1 was selected as the optimum (16.6 kJ

UVL1 or

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91% mineralization) and used or biodegradability studies. According to theZahn-Wellens test, the optimum phototreatment energy to achieve a biodegradableefuent is 13.6 kJ

UVL1 (65% mineralization), which corresponds to a hydrogen

peroxide consumption o 76.1 mM (approximately 8.5 L o CLW (at 7.7 g H2O

2L1)

or 15 L o CBW).Sanitary landll leachates resulting rom the rainwater percolation through the

landll layers and waste material decomposition is a complex mixture o high-strength organic and inorganic compounds that constitutes a serious environmentalproblem [13]. The photo-Fenton process is much more ecient in leachates treat-ment than heterogeneous (TiO

2, TiO

2/H

2O

2/UV) or homogeneous (H

2O

2/UV) photo-

catalysis, showing an initial reaction rate more than 20 times higher, and leading toalmost complete mineralization o the wastewater. However, when compared withTiO

2/H

2O

2/UV with acidication, the photo-Fenton reaction is only two times aster

[56]. The optimal energy dose estimated or the photo-treatment to reach a biode-gradable efuent, considering the Zahn-Wellens test, respirometry test, and biologicaloxidation tests at pilot plant scale, is 29.2 kJ

UVL1 (3.3 h o photo-Fenton at a

constant solar UV power o 30 W m2), consuming 90 mM o H2O

2when used in

excess, which means almost 57% mineralization o the leachate, 57% reduction opolyphenols concentration and 86% reduction o aromatic content [74].

The high concentration o nitrogen in landll leachates constitutes, beyond thepresence o recalcitrant carbon content, a big environmental concern that must besolved. Complete removal o ammonium, nitrates and nitrites o the photo-pre-treated

leachate was achieved by biological denitrication and nitrication, ater a previousneutralization/sedimentation o iron sludge (40 mL o iron sludge per liter o photo-treated leachate ater 3 h o sedimentation). The optimum C/N ratio obtained or thedenitrication reaction was 2.8 mg CH

3OH per mg NNO

3, consuming 7.9 g per

8.2 mL o commercial methanol per liter o leachate. The best nitrication ratioobtained was 68 mg NNH

4+ per day, consuming 33 mmol o NaOH per liter

(1.3 g NaOH per liter) during nitriication and 27.5 mmol o H2SO

4per liter

during denitrication [74].

11.3 Solar Photocatalytic Disinfection

Due to the lack o available on-site disinection technologies in many rural areas,water supply is not widely treated and the risk o transmission o many diseases isvery high and has been largely responsible or several large epidemics such astyphoid and cholera throughout the world [79]. The most commonly used tech-niques or water disinection are chlorination and ozonation. However, the overall

water service coverage in rural areas is rather low, because o many actors (techno-logical, cost, maintenance, social, cultural, logistics, education, etc.) responsible opresent situation. In addition, there is the risk caused by the chlorinated by-productssuch as trihalomethanes (THMs) and other organohalides resulting rom the reactiono chlorine with organic matter. Other existing technologies, such as ozone and UV

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disinection, are clearly o very dicult implementations in rural areas [45], otenamong the sunniest in the world. This is why solar water disinection methods, suchas the solar drinking-water disinection process called SODIS [http://www.sodis.ch/], have gained relevance in recent years, mainly in rural areas [61]. Nevertheless,the disinection eciency o the SODIS treatment can easily be aected by waterturbidity, low irradiation intensity and regrowth o bacteria ater the solar treatment,probably due to photo-repair mechanisms [55].

The combination o sunlight and a photocatalyst may be a promising option ordisinection/decontamination o natural waters or human consumption, in areaswith insucient inrastructures but high yearly sunshine. The reactive oxygen spe-cies produced can destroy a large variety o co-adsorbed chemical pollutants andinactivate waterborne microorganisms [6, 80].

Application o TiO2

to water treatment has been reviewed by Fujishima et al.

[23] and more recently by Herrmann [34]. Some authors suggest that the cell mem-brane is the primary site o attack by the reactive hydroxyl radicals [40, 63], whichcan be explained by peroxidation o the polyunsaturated phospholipid componento the lipid cell membrane leading to a loss o essential cell unctions, e.g., respira-tory activity, and in the end, to cell death [11, 83]. Disinection with supported TiO

2

or Fe reduces the need o a post-treatment not only in the laboratory, but also inlarge solar reactors [18, 25, 41, 54]. On the other hand, the immobilization o ironavoids also the initial acidication procedure, in order to prevent iron precipitation[9]. Fe-ions deposited onto chemically treated carbon abrics or encapsulated in

Naon thin lms cast directly onto the carbon abrics are ecient in decomposingH

2O

2used as an oxidant in the photo-assisted abatement o non-biodegradable

azo-dyes used in textiles even at neutral pH [32]. The supported catalyst was rmlyattached around an inner glass tube closed at the bottoms beore being placed in twoo the CPCs tubes. Tedlar polyvinyl fuoride (PVF) lm has also been tested as theinert support or TiO

2deposition ollowed by a subsequently coating with iron

oxides by means o orced hydrolysis o solution o FeCl3

[42].McLoughlin et al. [43] studied the use o three types o static solar collectors,

with aluminum refectors consisting o compound parabolic, parabolic, and V-groove

proles and all enhance the eect o the natural solar radiation, or the disinectiono water containingEscherichia coli, although the CPC was ound more ecient.As a result, they suggest that the disinection mechanism in the reactor congura-tion is either a synergistic eect between UV radiation and the mechanical stress orecirculation, or a stroboscopic shock eect in which bacteria are intermittentlyexposed to radiation and dark in the reactor, which is in agreement with the resultspresented by other authors Fernandez et al. [18].

The majority o work in this eld uses articially contaminated samples that areprepared with standard microorganisms in distilled water. Very little work has been

done with real water sources, such as rivers, lakes and wells as reported by Rincnand Pulgarn [55] and Wist et al. [80].Solar disinection o synthetic and natural waters rom the Douro River, northern

Portugal was studied in a pilot plant with CPCs [28, 29]. Inactivation oEnterococcusfaecalis (E. faecalis) was slower than oEscherichia coli (E. coli) possibly due tothe cell wall composition o the gram positive and negative bacteria, respectively.

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The high content o peptidoglycan, teichoic acids, polysaccharides, and peptidogly-colipids, inE.faecalis cell wall, when compared withE. coli, acts as a protectivecoating. The obtained results revealed thatE. coli inactivation can be achieved byphotolysis; however, the presence o TiO

2in suspension accelerates the reaction.

The Degussa P25 TiO2 coated on a paper matrix Type NW10 Ahlstrom paper [1],was tested and showed low eciency or bacteria inactivation. A non-empiricalmodel (Langmuir-Hinshelwood), considering a simplied reaction mechanism, wassuccessully used to describe the E. coli inactivation. The interaction between thebacteria and the supported TiO

2is the reaction constraint, reducing signicantly the

bacteria inactivation. The release o organic matter rom the support (paper matrixNW10) is also responsible by the absorption o UV light, radical scavenging andinhibition o the catalyst and, urthermore, may act as a nutrient supply or bacteria.No bacterial regrowth was observed orE.faecalis in synthetic waters. Oppositely,

regrowth occurred in natural waters. This behavior can be due to the natural waterchemical composition, with the presence o various organic and inorganic species.

11.4 Conclusion

Environmental Friendly Technologies are the new trend or water and wastewatertreatment. The strict environmental regulations and the world concern about environ-

ment issues became a high priority o all governments around the world. Funds orenvironment research are continuously rising, increasing the number o researchersand environmental research inrastructures. Under these circumstances, this chapterbrings other perspectives to best available technologies or water/wastewater treat-ment, as the use o low cost materials, e.g. algal biomass, or toxic metal ionsremoval, and the use o solar radiation, as photon source. Solar-driven photocatalysisalone or combined with biological oxidation is a green technology or detoxicationo dierent recalcitrant wastewaters and disinection o water.

Acknowledgments Financial support or this work was in part provided by national research proj-ect FCT/POCTI/AMB/57616/2004, companies projects with EFACEC Ambiente SA and guas doDouro e Paiva (AdDP) and by LSRE nancing by FEDER/POCI/2010, or which the authors arethankul. V. Vilars acknowledges his Doc and Post-Doc scholarships by FCT (SFRH/BD/7054/2001and SFRH/BPD/34184/2006) and Cincia 2008 Program.

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