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Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx

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Ultrasound-chitosan enhanced flocculation of low algal turbid waters

Sara Ann Fast , Veera Gnaneswar Gude *

Department of Civil and Environmental Engineering, Mississippi State University, Mississippi State, MS 39762, USA

A R T I C L E I N F O

Article history:

Received 15 February 2014

Received in revised form 18 September 2014

Accepted 19 September 2014

Available online xxx

Keywords:

Algae

Chitosan

Ultrasound

Flocculation

Sedimentation and rapid mix

A B S T R A C T

In this study, we evaluated the effect of ultrasound-chitosan enhanced flocculation process for efficient

removal of algal cells from low algal turbid waters comparing with the conventional rapid mix process.

The results show that the turbidity removal efficiencies for ultrasound-enhanced coagulation (97.8–99%

removal) were comparable to the conventional rapid mix coagulation (96.8–99% removal) for alum and

for chitosan (84.1–90.5% for RM and 84–97% for US). This study confers that ultrasound mixing can be

performed instead of conventional rapid mixing to improve the algal cell removal efficacies from the low

algal turbid waters.

� 2014 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering

Chemistry.

Contents lists available at ScienceDirect

Journal of Industrial and Engineering Chemistry

jou r n al h o mep ag e: w ww .e lsev ier . co m / loc ate / j iec

30313233343536373839404142434445464748495051525354

Introduction

Algae growth is a common problem in water treatment plantsand water reservoirs. Algae are aquatic organisms classifiedseparately from plants. Algae are a large and diverse group ofsimple, typically autotrophic organisms, ranging from unicellularto multicellular forms. Algae blooms are a seasonal problem inmany surface waters worldwide both in natural and engineered/industrial systems. Many rivers and streams which serve asdrinking water sources are contaminated by algal growth and areconsidered nuisance [1,2]. For example, cooling towers in powerplants also provide ideal conditions for algal growth, offsetting theheat transfer capacity of the cooling surfaces and eventuallyreducing the process performance [3]. The presence of algae isoften associated with production of phthalate esters and poly-chlorinated biphenyls (PCBs) [4,5]. Algae are of particular concernto water companies with respect to the provision of drinking waterto a satisfactory standard. Cell populations can vary widely interms of cell count and diversity, and this can impact thetreatability of the algae. Algae can also affect the color, tasteand odor of drinking water, and a limited number of species alsoexcrete toxic metabolites which, if consumed in insufficientquantities, can cause health problems [1,6,7]. Many freshwaterblue-green algae can produce toxins, i.e., cyanotoxins (classifiedbased on their toxin group as heptotoxins, neurotoxins, cytotoxins

55565758

* Corresponding author. +1 662 325 0345.

E-mail addresses: gude@cee.msstate.edu, gudevg@gmail.com (V.G. Gude).

Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng. C

http://dx.doi.org/10.1016/j.jiec.2014.09.023

1226-086X/� 2014 Published by Elsevier B.V. on behalf of The Korean Society of Indus

and dermatoxins) which can result in liver hemorrhage, muscularparalysis, respiratory effects and can cause headache, anorexia,vomiting and damage to organs [8]. Algae presence can alsoincrease the coagulant demand and treatability issues includingfilter blockage [1]. A survey on 76 water supply utilities in the USAby EPA has recommended many alternatives to control the algalgrowth in the water treatment plants by chlorination fordisinfection, use of an occasional shock treatment, and additionof algaecides in-situ in reservoirs [8,9].

Algae can be removed by using techniques such as centrifuga-tion, air floatation, coagulation, flocculation, electro-coagulation–flocculation and hydrodynamic cavitation [10,11]. Among these,flocculation is the most widely practiced technique for simplicityand economic feasibility. Commonly used flocculants are alumi-num and ferric based salts which form precipitates to agglomeratethe microalgae. Despite the high efficiency of these flocculants, theabundant sludge that is generated in the process is difficult todehydrate, its efficiency is entirely dependent on the pH, and whenformed in cold water, alum flocs are not very mechanicallyresistant. In addition, the use of alum is a source of concern, and thedebate about its possible toxicity is still open. Since high aluminumconcentrations in water may have human health implications,environmentally friendly coagulants will present an interestingalternative for water purification [12]. Chitosan, a naturallyoccurring organic biopolymer, seems to be a promising alternativeto address the aforementioned issues. Chitosan is a linear poly-amino-saccharide, which is produced by alkaline deacetylation ofchitin [13]. Chitin is the second most abundant biopolymer in theworld, after cellulose. The main sources exploited are two marine

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trial and Engineering Chemistry.

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ustaceans, shrimps and crabs. It is insoluble in water and soluble acids. Chitosan also possesses several intrinsic characteristicsat make it an effective coagulant and/or flocculant for themoval of contaminants in the dissolved state. It has character-ics of both coagulants and flocculants, i.e., high cationic chargensity, long polymer chains, bridging of aggregates and precipi-tion (in neutral or alkaline pH conditions). Its uses are justified byo important advantages: firstly, its non-toxicity and biodegrad-ility [14,15]; secondly its outstanding chelation behavior. Itsique physico-chemical properties render it very efficient in

teractions with various contaminants including both particulated dissolved substances. These properties have been exploited fore design of coagulation/flocculation processes applied to theeatment of various effluents [16].

Harvesting highly concentrated algal suspensions does notpear to be a serious concern since it can be achieved by sweepcculation, a widely practiced technique. On the other hand,

moving low algal cell concentration from low turbid watersspecially in drinking water sources) can pose several processallenges. Thus, the aim of this research is to utilize the chitosan

biopolymer coagulant/flocculant) and ultrasound (a non-nventional mixing and inactivation technique) simultaneously

enhance the algal cell removal efficiency from low algal turbidaters. Chitosan and ultrasound were individually evaluated foreir effect and enhancement of coagulation and flocculationocesses in the past, but their combined effect on these chemical/ysical processes was not reported to date. In this study, theitosan-ultrasound enhanced coagulation/flocculation methodas compared with the conventional rapid mix/flocculationocess to evaluate the performance of the proposed method.other aim of this research is to investigate if the ultrasound

fect can be used as a mechanism to distribute the chemicalagulant (rapid mix step) and promote pin-floc formation while

ultaneously inactivating the algal cells by the shock treatment the acoustic waves to facilitate easy flocculation/sedimentationocess. The following sections will provide the details on theperimental procedures and the process optimization study foritosan-ultrasound enhanced coagulation/flocculation process to

eat the low algal turbid waters.

aterials and methods

w algal turbid waters and coagulants

Concentrated Chlorella sp. paste was obtained from ammercial producer which was used to prepare a stable algalll suspension of 10–40 NTU of measurable turbidity. Thespension was tested to ensure 99.9% of turbidity over a 24 httling period. A 1% chitovan coagulant polymer was purchased

om a commercial water chemicals company Dungenessvironmental Inc ., Washington, USA. We also prepared a

fferent chitosan solution by using dry chitosan powderrchased from Fisher Scientific (Acros-Organicas) with molecu-

r weight in the range of 600,000–800,000. This chitosanueous solution was prepared by dissolving chitosan in a 1%lute aqueous acetic acid solution (1% v/v) with a 90% degree ofacetylation and mixed with a magnetic stirrer at 100 rpm forer 24 h to obtain a 1% (w/w) stock solution. The aluminumlfate (Al2(SO4)3nH2O; n = 12–14) coagulant was procured fromsher ScientificTM. 5.8 g of aluminum sulfate was added to 50 mL

DI water to form a concentrated solution of 100, 000 ppm,hile the chitovan or chitosan concentrations were 10,000 ppm.us, for alum, 0.1 mL of dosage equals to an actual concentration

10 mg/L whereas the dosage for chitovan and chitosan aremg/L (for 0.1 mL dosage).

Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng.

Coagulation/flocculation experiments

Several experiments were conducted to study the combinedeffect of alum, chitosan and ultrasound. The effects of chitosandosage and ultrasound power were tested in low algal turbidwaters with a turbidity ranging between 10 and 40 NTU at 10 NTUintervals. The ultrasound enhanced coagulation/flocculation wasperformed using a NO-MS100 ultrasonicator manufactured byColumbia International Technologies with 1000 W power outputcapacity. The ultrasonic frequency was 25 kHz. The horn is made oftitanium alloy with 10 levels of amplitude to vary the effectof ultrasonic application. An ultrasound exposure time of 1 minwas applied in lieu of rapid mixing process. After the simultaneousultrasound exposure and coagulant addition (alum or chitovan),the algal suspension was subjected to slow mixing at 50 rpm for20 min. For the tests which followed conventional rapid mixing, a200 rpm mixing speed was applied for 2 min. For both methods(conventional rapid mix-flocculation–sedimentation vs. ultra-sound-flocculation–sedimentation), the sedimentation time was24 h. The turbidity was measured at 1 h of settling time and at 24 hsettling time to capture the maximum removal efficiency.

The algal suspension test volumes were fixed at 1000 mL in a1500 mL standard jar for both conventional rapid mix (RM) andnon-conventional ultrasound (US) methods. This study consistedof batch experiments, using a Phipps and Bird jar tester unit (model7790-400; 120 V, 60 Hz and 220 V, 50/60 Hz) which accommo-dates six 2-L jars/beakers. The beakers were filled with 1000 mL ofthe microalgae culture for each test run. Six stainless steel 100 � 300

paddles are spaced 6 in. apart and are adjustable to a maximumdepth of 9 in. with a highly reliable electronic motor controlsystem regulated at variable speeds (of all paddles simultaneous-ly), from 1 to 200 rpm. The contents of each beaker weresimultaneously stirred at the same speed with a six-spindle ofsteel paddles.

The experiments started with the effect of coagulant dosage forboth alum and chitosan. For the coagulant dosage effect test the pHwas maintained at 7. To measure the effect of optimum pH, the pHwas varied between 5 and 9 units, i.e. at 5, 6, 7, 8, and 9 while fixingthe coagulant dosage. The pH of the algal suspension was adjustedby adding either NaOH (base) or HCl (acid) prior to flocculation.Also, the effect of ultrasound power on the algal cell removalefficiency was tested at different power levels 100, 250, 500 and1000 W which gives a power density of 0.1 W/mL, 0.25 W/mL,0.5 W/mL and 1.0 W/mL respectively. All the experiments wereconducted in triplicate, and the average of the three results wereevaluated.

Flocculation removal efficiency

The samples were collected at the start of the experiments, after1 h sedimentation time as well as 24 h sedimentation time. Theturbidity of the water samples was measured at these specifiedsteps and time intervals. The turbidity was measured using HACH2100 N Turbitimeter1turbidity meter. The turbidity removalefficiency (RE) was calculated using the following equation [17]:

RE %ð Þ ¼ 1 � TF

TI

� �� 100% (1)

where TI is the initial turbidity and TF is the final turbidity of thealgal suspension.

The concentration factor (CF) was measured using the followingequation [18]:

CF ¼ V � ODI � VS � ODF

ðV � VSÞ � ODI(2)

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Where ODI is the optical density of the algal turbid watersample, ODF is the optical density of the clarified water sampleafter flocculation and sedimentation, V is the total sample volume,VS is the volume of the clarified water after flocculation andsedimentation.

Results and discussion

Effect of ultrasound enhanced coagulation–flocculation process

The effect of ultrasound as a rapid mixing technique wasevaluated. The purpose of ultrasound irradiation was two-fold: (1)

Fig. 1. Flocculation removal efficiency (%) for alum and chitosan using ultr

Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng. C

to evenly distribute the coagulant; and (2) to promote theformation of pin floc. The ultrasound was applied for 1 min fordifferent algal turbid waters with turbidity between 10 and40 NTU. Two coagulants (alum and chitovan) were tested toevaluate the efficiency of ultrasound-enhanced coagulation–flocculation process. Fig. 1 shows the turbidity removal efficienciesfor different water turbidities using alum and chitosan ascoagulants. At 10 NTU, about 90% turbidity was removed at0.1 mL dosage, but the efficiency decreased with increased dosage,perhaps, due to over dosage (Fig. 1a). For 20 NTU water turbiditythe removal efficiency was 90.5% at a 0.25 mL dosage (Fig. 1c). For30 NTU turbidity, the removal efficiency was 94.5% at a 0.3 mLdosage (Fig. 1e), and for 40 NTU turbidity; a 96.9% turbidity

asound (for alum 0.1 mL = 10 mg/L; and for chitosan 0.1 mL = 1 mg/L).

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Fig. 2. Effect of pH on flocculation removal efficiency (%) for chitovan using

ultrasound: (a) alum and (b) chitosan.

Fig. 3. Changes in pH for alum addition after ultras

S.A. Fast, V.G. Gude / Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx4

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Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng.

removal was observed at a dosage of 0.4 mL (Fig. 1g). For 10 NTUturbidity, alum dosage in the range 0.1–0.6 was found to beeffective (Fig. 1b), but with highest removal efficiency at 0.5 mLdosage with a 99.1% turbidity removal. For 20 NTU water turbidity,an effective dosage of 0.6 mL with a 97.4% was identified (Fig. 1d).For 30 NTU water turbidity, the optimum dosage was 0.6–0.7 witha removal efficiency of 98.1% (Fig. 1f), and for 40 NTU waterturbidity, the optimum dosage was 0.7 with a removal efficiency of98.5% (Fig. 1h). From these experiments, it was noticed that alumwas effective as coagulant/flocculant at a wide range of dosages,indicating the flexibility in operations. Also, the possible mecha-nism responsible for higher alum dosages is ‘‘sweep coagulation’’(charge neutralization and enmeshment in the precipitate), awidely used mechanism in the water and wastewater treatmentfacilities [19]. For chitovan, the removal efficiency at higherconcentrations did not positively impact the coagulation/floccula-tion process, perhaps due to restabilization of the polymerbranches due to over dosage. Adsorption and charge neutralizationis another coagulation/flocculation mechanism which can be easilyaffected by the concentration of the suspended particles, coagulantdosage and the type of mixing. Slight over dosages might causecharge reversibility and restabilization of the algal suspension. Thisis due to the inefficient coagulation that may result fromoverdosing of polymer or from intense or prolonged mixing. Ifexcessive polymer is added, the segments may saturate thesurfaces of algal cells so that no sites are available for the formationof polymer bridges, which can restabilize the algal cells and maycause charge reversal. Intense or prolonged mixing may destroypreviously formed bridges and lead to restabilization.

Effect of pH on ultrasound enhanced coagulation–flocculation process

We studied the effect of ultrasound-enhanced coagulation/flocculation process over a pH range of 5–9. The flocculationremoval efficiencies for alum and chitovan are shown in Fig. 2. Itcan be observed from Fig. 2a that the alum as coagulant has workedwith in the entire tested range of pH which can be found in natural

ound mixing and after slow mixing (flocculation).

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Fig. 4. Changes in pH for chitovan addition after ultrasound mixing and after slow mixing (flocculation).

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waters. This proves the applicability of alum. However, thechitovan was sensitive to the pH changes. The pH 7 and pH 8 haveproduced highest algal turbidity removal rates (Fig. 2b). Low pHwas observed to be ineffective on the coagulant/polymer chemis-try. At lower turbidities (for 10 and 20 NTU), the flocculation wassensitive to the pH of the water as well. For 10 NTU, the residualturbidity after coagulation/flocculation was even higher than theoriginal condition. It is interesting to note from Fig. 3a–d that alumaddition has higher effect on the pH at different turbidities comparedto the effect of chitovan on the pH shown in Fig. 4a–d. From thesefigures, it can be noted that chitovan has less effect on the pH whencompared to alum. Chitosan, a natural biopolymer, does not formacidic compounds as much as alum does. Thus, chitosan may offer aclear advantage of even treating low alkalinity and high turbiditywaters most commonly found in southeastern states ofthe USA.

Dosage requirements

The dosage requirements for alum and chitovan for differentwater turbidities are shown in Fig. 5. In general, as a comparison,dosages of 0.5–1.5 mg/L of cationic polymer are often effective for

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Fig. 5. Coagulant dosage requirements for alum and chitosan at different algal water

turbidities.

Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng. C

coagulation, whereas as much as 10–20 times that amount of alumwould be required to achieve the same results. In this study, weobserved that alum dosage (100,000 ppm) requirement was 15–50times higher than chitovan dosage (10,000 ppm). This can beexplained as follows: at low water turbidities, it is difficult to causecoagulation/flocculation due to lower number of algal cells presentand a possible mechanism that occurred here in both cases was acombination of adsorption (charge neutralization) followed byenmeshment with addition of extra coagulant. For alum, thismechanism worked very well. However, for chitovan, at lowerturbidities, we observed a restabilization condition increasingresidual turbidity, perhaps, due to charge reversal on the algal cells(Fig. 2b).

Floc formation

Fig. 6 shows the images of floc formation for the alum andchitovan coagulants. The sludge formation was proportional to thealgal water turbidity and the coagulant dosage. It can be noted thatthe higher turbidities required higher coagulant dosages resultingin higher sludge volumes. In comparison, the alum produced moresludge than chitovan. It is interesting to note from Figs. 6 and 7 thatthe alum floc size was smaller than the floc formed by chitovan.Alum sludge varied between 0.5 and 1 mm in size while thechitovan floc size varied between 0.5 and 1.75 mm for 10–40 NTUwater turbidity (Fig. 7). Alum sludge settled at a comparablevelocity to the chitovan sludge although it is smaller in size. Thealum sludge is inorganic in nature while the chitovan sludge wasorganic and has less specific gravity. For this reason, a slightamount of chitovan sludge remained on the water surface at theend of the settling period.

The mechanism responsible for ultrasonic flocculation is basedon the principle of collision between particles. When the ultrasonicwaves are introduced into the algal suspension containing singlealgal cells in micrometer size, vibrations are caused by theultrasonic waves. The vibration amplitude of the particles dependson the size of the algae cells. Smaller algae cells vibrate greater

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Fig. 6. Comparison of the floc formation between alum and chitovan for ultrasound enhanced coagulation–flocculation process at different turbidities: (a) 10 NTU–alum; (b)

20 NTU–alum; (c) 30 NTU–alum; (d) 40 NTU–alum; (e)10 NTU–chitovan; (f) 20 NTU–chitovan; (g) 30 NTU–chitovan; (h) 40 NTU–chitovan.

Fig. 7. Floc size difference between alum and chitovan.

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an larger algal cells. The larger the vibration amplitudefference, the higher will be the collisions between the cells. Asresult of this collision, two or more cells stick together to formrger cells. The more the contact between these agglomerated

Fig. 8. Comparison between the conventional rapid mixing and non-conventiona

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cells, the larger will be the size of the resulting agglomerated algalcells, which would increase their settling characteristics [20,21].

Comparison between the rapid mix and ultrasound coagulation/

flocculation

A set of experiments were conducted with the pre-determinedcoagulant dosages for different algal water turbidities (10–40 NTU)to compare the performance of conventional rapid mixing andnon-conventional ultrasound mixing for coagulation process andchemical distribution. In this test, the rapid mixing at 200 rpm wasprovided for 2 min while ultrasound exposure was provided for1 min. In both cases, 20 min of slow mixing was provided tofacilitate agglomeration of algal cells. Fig. 8 shows that theturbidity removal efficiency for ultrasound enhanced coagulation(97.8–99% removal efficiencies) was comparable to conventionalrapid mix coagulation (96.8–99% removal efficiencies) for alum, aswell as for chitosan (84.1–90.5% for RM and 84–97% for US) andultrasound worked better for chitosan coagulation/flocculation.The mechanisms responsible for the coagulation/flocculationprocess by the two methods are described in the followingdiscussion.

l ultrasound enhanced (alum and chitosan) coagulation–flocculation processes.

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Fig. 9. Effect of ultrasound power effect on flocculation removal efficiency (%) at

different algal water turbidities.

Fig. 10. Relation between the power density and flocculation removal efficiency (%)

for ultrasound enhanced coagulation–flocculation process.

Fig. 11. Effect of flocculation time on ultrasound enhanced coagulation–flocculation pr

efficiency for different flocculation times; (c) flocculation removal efficiency at 120 min

different sedimentation times.

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Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng. C

Ultrasonic coagulation/flocculation mechanism: The complexmechanism of the acoustic or ultrasonic agglomeration involvesorthokinetic and hydrokinetic interaction. The orthokinetic interac-tion is based on the principle that collision is produced by differententrainment experienced by particles of different sizes or weightswhile the hydrodynamic mechanism is produced by particleinteraction through the surrounding fluid due to hydrodynamicforces ([22,21]). The ultrasonics can remove turbidity as well asalgae cells in this manner as demonstrated in many researchstudies. In the recent studies, it was noted that the reduction in thewater turbidity levels correspond well with the algal cell removal[22]. Ultrasound has been proven to remove other pollutants suchas ibuprofen.

Conventional coagulation/flocculation mechanism: Flocs areformed by two principal mechanisms: (1) perikinetic andorthokinetic flocculation. When the particle contact is achievedby the Brownian motion, it is called perikinetic flocculation andwhen the floc is formed by stirring or settling, it is calledorthokinetic flocculation, similar to ultrasonic flocculation. Periki-netic flocculation dominates for particles with size less than0.1 mm in diameter and orthokinetic flocculation becomesdominant once these particles reach a size of 1 mm by particlecontact, which requires a very low velocity gradient to promoteparticle contact and flocculation [23].

Effect of ultrasound power

The effect of ultrasound power on the turbidity removalefficiency using chitosan is shown in Fig. 9. It was determined that100 W ultrasound power was adequate to provide 98.5% or greaterturbidity removal efficiencies. Higher ultrasound power application

ocess: (a) final turbidity at different sedimentation times; (b) flocculation removal

settling time for different flocculation times; (d) flocculation removal efficiency for

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Fig. 12. Concentration factor vs. flocculation time.

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d not show a positive trend, while a 50 W power application hassulted in low efficiencies. Fig. 10 shows the response surface fore relationship between the power density (W/mL), turbidity (NTU)d the turbidity removal efficiency. Lower power densities resulted

higher turbidity removal efficiencies as shown in Fig. 10. Thiseans that higher ultrasound power exposure may result indesired algal cell damage, introducing intracellular materials intoe water being treated.

e effect of flocculation and sedimentation time on turbidity removal

ficiency

Further, the effect of different flocculation times following thetrasound mixing was studied. Different flocculation times (5, 10,, 20, 30, and 40 min) were applied followed by a 2-hdimentation process. An initial water turbidity of about

NTU was maintained in these tests. Fig. 11a shows the finalrbidity (NTU) levels at 2-h sedimentation while Fig. 11b–d showse turbidity removal efficiencies for different flocculation anddimentation times. In these tests, it can be noted that the finalrbidity of the supernatant was lower than 1 NTU for flocculation

e between 20 and 40 min. The removal efficiencies did notprove considerably after 20 min of flocculation time. It wasnfirmed from this test that about 20–30 min of flocculation timeas adequate to produce high quality treated water. Velocityadients in flocculation basins must be high enough to achieve therticles contact necessary to promote aggregation; however, theyust not be so high that they shear the flocs apart. Flocs produced

organic polymers may be stronger than those produced fromuminum salts and can withstand higher shearing stresses.wever, if flocs are ruptured, reaggregation is more likely to occur

r aluminum flocs than for polymer flocs because the polymergments once detached by mixing, may fold back and restabilizee particles. Also, the pH may have a significant effect on thelymer bridging and adsorption in the destabilization of algalspensions [24]. In applications such as adsorption columns, themobilization of chitosan on support materials such as glassads could help improve process efficiency [25]. Fig. 12 shows thencentration factor of the ultrasound enhanced process forfferent flocculation times. It is important to determine in therms of concentration factor, which gives an idea of effectiveness the slow mixing and sedimentation time. As shown in Fig. 12, thencentration factor was only 5 for 5 min, while at 20 min of slowixing a concentration factor of 30 was observed. Longer

Please cite this article in press as: S.A. Fast, V.G. Gude, J. Ind. Eng.

flocculation times did not show significant effect on theconcentration factor. Higher concentration factor indicates lowersludge volumes and vice versa.

Conclusions

The presence of algae in drinking water sources poses severalprocess and health related concerns at water and wastewatertreatment plants. In most cases, these algal suspensions exhibitlow turbidity levels, and treating such waters can be a challenge. Inthis study, the feasibility of ultrasound-chitosan enhancedflocculation process was evaluated in lieu of conventional rapidmix-flocculation method. The results from this study suggest thatultrasound-chitosan enhanced flocculation process can providecomparable turbidity removal efficiencies when compared to rapidmixing method while reducing the chemical dosages as well as thesludge volumes. Further studies on process, design and optimi-zation may result in an environmental-friendly and sustainablealternative to the conventional rapid mixing-flocculation process,especially for low algal turbid waters.

Acknowledgments

This research project was supported in part by The UnitedStates Q3Environmental Protection Agency (USEPA) under the grantnumber SU835519. Also, this research was supported by the Officeof Research and Economic Development (ORED), the BagleyCollege of Engineering (BCoE), and the Department of Civil andEnvironmental Engineering (CEE) at Mississippi State University.SAF was supported by the research fellowship from MississippiState University’s Shackouls Honor College. Q4

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