Review Article Recent Development in Ammonia Stripping ...

Review ArticleRecent Development in Ammonia Stripping Process forIndustrial Wastewater Treatment

Lennevey Kinidi 1 Ivy Ai Wei Tan 1 Noraziah Binti Abdul Wahab1

Khairul Fikri Bin Tamrin 2 Cirilo Nolasco Hipolito1 and Shanti Faridah Salleh1

1Department of Chemical Engineering and Energy Sustainability Faculty of Engineering Universiti Malaysia Sarawak94300 Kota Samarahan Sarawak Malaysia2Department of Mechanical and Manufacturing Faculty of Engineering Universiti Malaysia Sarawak 94300 Kota SamarahanSarawak Malaysia

Correspondence should be addressed to Lennevey Kinidi lennybb93outlookcom

Received 5 March 2018 Revised 14 May 2018 Accepted 13 June 2018 Published 9 July 2018

Academic Editor Sebastien Deon

Copyright copy 2018 Lennevey Kinidi et al -is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

It is noteworthy to highlight that ammonia nitrogen contamination in wastewater has been reported to pose a great threat to theenvironment -is conventional method of remediating ammonia nitrogen contamination in wastewater applies the packed bedtower technology Nevertheless this technology appears to pose several application issues Over the years researchers have testedvarious types of ammonia stripping process to overcome the shortcomings of the conventional ammonia stripping technology Alongthis line the present study highlights the recent development of ammonia stripping process for industrial wastewater treatment Inaddition this study reviews ammonia stripping application for varied types of industrial wastewater and several significant operatingparameters Furthermore this paper discusses some issues related to the conventional ammonia stripper for industrial treatmentapplication Finally this study explicates the future prospects of the ammonia stripping method -is review hence contributes byenhancing the ammonia stripping treatment efficiency and its application for industrial wastewater treatment

1 Introduction

Human activities appear to be the major contributor to waterpollution for instance agricultural industrial and municipalactivities Nitrogen surplus released into the environment hasbeen proven to cause negative impacts on water qualitieshuman health and ecosystems [1] Nonetheless a wide rangeof technologies is available to reduce the release of ammonianitrogen into the environment such as ammonia stripping[2] breakpoint chlorination [3] ion exchange [4] electro-dialysis [5] and biological nitrification [6] -e ammoniastripping method has several plus points as it is a relativelysimple process and cost-effective to remove ammonia inwastewater [7] Besides the valuable ammonia stripped fromwastewater can be recovered from the stripping process Dueto the stability of this process the ammonia stripping processhas been deemed as an appropriate method in remediatingwastewater that contains high concentration of ammoniaand toxic compounds [8] Consequently ammonia stripping

has emerged as a strong interest research area among re-searchers and industrial community As such numerous lab-scale and pilot-scale studies have been performed especiallyfor the wide range of industrial wastewater that demands cost-effective remediation

-is paper looks into several emerging issues pertaining toremediating ammonia nitrogen by using the ammonia strippertechnique along with some significant operating parametersIn addition this paper reviews the recent progress in am-monia stripping method with advanced gas-liquid contactorsas conducted by some researchers Next a comparison wasmade between the advanced liquid contactors and the con-ventional packed tower Finally this paper explores the futureprospects of this ammonia stripping process

2 Ammonia Stripping Process

-e ammonia stripping process is based on the principle ofmass transfer It is a process by which wastewater is contacted

HindawiInternational Journal of Chemical EngineeringVolume 2018 Article ID 3181087 14 pageshttpsdoiorg10115520183181087

with air to strip the ammonia gas present in the wastewatere presence of ammonia in wastewater can be found in twoforms namely ammonium ions and ammonia gas erelative concentrations of ammonia gas and ammonium ionsare subjected to the pH and the temperature of wastewater [9]e formation of ammonia gas is favored by increasing thepH which shifts the chemical equilibrium to the right thusinducing the formation of ammonia gas Since high pH isrequired for eective ammonia stripping lime is used toincrease the pH values of wastewater prior to ammoniastripping [9] In fact various types of congurations forammonia stripping process have been applied to remediatethe varied types of wastewater containing ammonia nitrogenFor instance OrsquoFarell et al conducted a study on nitrogenremoval by stripping on a secondary e uent of a municipalwastewater treatment plant [10] Figure 1 illustrates a sche-matic diagram of lime precipitation process and ammoniastripping process Lime is incorporated to hike the pH of theinuent prior to stripping and this is followed by a recar-bonation process for neutralization Aside from raising thewastewater pH calcium oxide (lime) generates calciumcarbonate in the wastewater and serves as a coagulant for hardand particulate matters Additionally OrsquoFarell et al discov-ered that the ammonia stripping method could remove asmuch as 90 of ammonia from the secondary e uent [10]

Meanwhile Raboni et al investigated the eciency ofthe ammonia stripping technique for remediation ofgroundwater polluted with leachate [11] (Figure 2) In thestudy polyelectrolyte sodium hydroxide and iron (iii)chloride were added for the coagulation-occulation andsedimentation processes at pH higher than 11 [11] esystem also comprised of a heater to heat the wastewater at38degC and ammonia recovery via absorption with sulphuricacid Lastly the e uent was neutralized after adding sul-phuric acid As a result they found that the ammoniastripping system for groundwater polluted with leachatedisplayed removal eciency of 954 with initial ammoniaconcentration at 1990mgL

Next Saracco and Genon investigated the performanceof air-stripping system to treat ammonia nitrogen fromindustrial e uent (Figure 3) [12] ey suggested this routeas feasible only if the industrial e uent was characterized byrelatively high temperature and ammonia concentratione stripping process was followed by absorption andcrystallization processes Saracco and Genon concluded thatthe ammonia stripping and the recovery system along withits internal air recycle had been technically feasible and easyto control [12]

3 Ammonia StrippingApplication in IndustrialWastewater Treatment

To date ammonia stripping pilot-plants have been employedto treat various types of wastewater containing high con-centrations of ammonia and toxic compounds such as thatderived from secondary e uent of municipal wastewatertreatment plant [10] animal manure [13] and landllleachate [14] Most recently ammonia stripping was appliedto anaerobic-digested e uent as this method oers botheconomic and environmental advantages e biogas pro-duced in the anaerobic digestion was used for ammoniaremoval to prevent inhibition of methanogenesis in theanaerobic reactor [15ndash17] Meanwhile Bonmati and Flotatsrevealed that no pH modication was required for strippingof ammonia from pig slurry [18] On the other hand Limoliet al investigated ammonia removal from raw manuredigestate by employing the turbulent mixing strippingprocess ey found that the ammonia stripping process viaturbulent mixing was indeed feasible for raw manuredigestate [19]

Table 1 shows that the ammonia stripping technique isindeed highly ecient in treating wastewater that containsammonia nitrogen with toxic compounds Besides am-monia stripping combined with anaerobic digestion seemedto enhance the performance of anaerobic digestion processapart from being cost-eective for ammonia removal

InfluentLime

WasteFirst stage Second stage

To filter

Stripping

Carbondioxide

Figure 1 Schematic ammonia stripping process for leachate-polluted groundwater [10]

2 International Journal of Chemical Engineering

Nonetheless Serna-Maza et al revealed that in-situ am-monia stripping in mesophilic condition was unlikely tohave any commercial application for wastes with in-termediate total ammonia nitrogen concentrations as onlyhigh total ammonia nitrogen concentration stripping hadmanaged to reduce the total ammonia nitrogen concen-tration below the higher inhibition threshold of approxi-mately 8 gmiddotNmiddotLminus1 [29] us stripping coupled with dilution

may oer the best means of controlling total ammoniacalnitrogen concentrations Next Collivignarelli et al foundthat ammonia stripping without dosage of basicant hadbeen feasible when the initial alkalinity of the leachate wasequal to or greater than the acidity of ammonium ions forremoval [30] Notably this can potentially minimizechemical usage and slash operational cost in removingammonia nitrogen from leachate Ammonia stripping also

Liquid in

Fandemister

spraynozzles

T (in)

T (out)

T (out)

Liquid out

Ty (in)

Air internalcycle Tyi (out)

Tyi (in)

Tx (in)

Tx (out)

H2SO4 and H2Omake up

P (NH4)2SO4

Boiledawaywater

Steam

Condensate

Stripping Absorption Crystallization

Figure 3 Proposed plant for ammonia stripping for industrial e uent application [12]

CF SED

N F

H1

H2

ST

Stripping air(closed loop)

AT

H2SO4 98

(NH4)2SO4solution 30

H2SO4

Effluent

Sludge to dryingPolyelectrolyte

NaOH

FeCl3

CF coagulation-flocculationSED sedimentationST stripping towerAT absorption tower

F sand filtrationN neutralizationH1 heat exchanger (heating)H2 heat exchanger (cooling)

Figure 2 Schematic ammonia stripping process for leachate-polluted groundwater [11]

International Journal of Chemical Engineering 3

appears to be effective and suitable in agriculture due to itssimple process and cost-effectiveness in removing ammoniaefficiently

4 Process Condition

Numerous studies have highlighted the impacts of varyingoperational parameters upon the performance of ammoniastripping process Some important parameters that havebeen reported to influence the performance of ammoniastripping are temperature pH and air to water ratio

41 Temperature Temperature has been proven to havea significant impact on the performance of ammoniastripper-is is because the solubility of ammonia in water isgoverned by Henryrsquos law In Henryrsquos law the constant of gasrelies on solute solvent and temperature [31] For exampleCampos et al discovered that the removal of ammonia fromlandfill leachate at 60degC was relatively significant overa period of 7 hours than at 25degC [32] Generally higherefficiency ammonia removal can be obtained at highertemperature Saracco and Genon also found that the capital

cost of ammonia stripper at a stripping temperature of 80degCwas less by half than that at 40degC Nevertheless from theeconomic stance increment in temperature may lead toa hike in the cost of preheating [12]

42 pH Ammonia nitrogen in water exists in equilibriumbetween the molecular (NH3) and ionic form (NH4

+)according to the following reaction

NH3 + H2OlarrrarrNH +4 + OHminus (1)

-e distribution between molecular ammonia and am-monium ions in water can be defined by (2) [16] and (3) [18]

NH31113858 1113859 NH3 + NH +

41113858 1113859

1 + H+[ ]Ka(2)

pKa 4 times 10minus8T3+ 9 times 10minus5T2

+ 00356T + 10072 (3)

where [NH3] is the molecular ammonia concentration[NH3 + NH +

4 ] is the total ammonia concentration [H+] isthe hydrogen ion concentration and Ka is the acid ioni-zation constant Besides that pKa can be expressed in terms

Table 1 Several studies that had looked into the ammonia stripping process with varied types of industrial wastewater

WastewaterAmmoniastrippingreactor

Influent ammonia(mgL)

Ammoniaremoval

percentage ()Operating condition Reference

Biologically treated bluecrab processing wastewater Packed bed 2300 72

Liquid loading rate25 Lm2min [20]Temperature 14degCPH 120

Petroleum refinery wastewater Packed bed 100 85

Airflow rate 84951 L ofairgal of wastewater [21]Temperature 25degC

pH 105

Landfill leachate Packed bed 1213 88Airflow rate 4500 Lmiddothminus1

[22]Temperature 25degCpH 11

Piggery wastewater Packed bed 4950 80Airflow rate 10 Lmin

[23]Temperature 37degCpH 11

Fertilizer effluent Packed bed 2000 99Airflow rate 420m3middotmminus2middothminus1

[24]Temperature 26degCpH 11

Raw manure digestate Mixer 5000 887 Temperature 23degC [19]pH 10

Secondary effluent Packed bed 12 862Airflow rate 100 Lminsqmiddotm

[10]Temperature 206degCpH 117

Acetylene purificationwastewater Packed bed 125 91

Airflow rate 05m3h[25]Temperature 60degC

pH 12

Ammonia-rich soda ashwastewater

Microwave-assisted

air stripping1350 963

pH 11 time 5 mins[26]microwave radiation

power 750WSludge liquor from municipalwastewater treatment plants

Ion exchangerloop stripping 2300 846 pH 105 [27]

Swine wastewaterMicrowave-assisted

air stripping2740 882

pH 11[28]microwave

radiation 700W

4 International Journal of Chemical Engineering

of temperature as shown in (3) Higher pH favors theformation of ammonia gas whereas lower pH favors theformation of ammonium ions Hence raising the pH level ofthe wastewater prior ammonia stripping is crucial to favorthe formation of molecular ammonia nitrogen for strippingHowever according to Hidalgo et al excessive rise of pHposes extra cost of lime that is nonfeasible in terms of costHence an optimum pH is required to strike a balance be-tween process efficiency and economic cost -ey found thatwhen the pH exceeded 105 the removal efficiency wasinsignificant because pH no longer the affected the ioni-zation balance between molecular ammonia and ionicammonium but the cost incurred rose significantly due tothe additional lime consumption required to increase the pHlevels [33] Meanwhile Markou et al revealed insignificanteffect for the types of alkali (potassium hydroxide sodiumhydroxide and calcium hydroxide) used on the ammoniaremoval efficiency [34] However calcium alkali was pref-erable due to reduction of solids heavy metal concentra-tions and color of wastewater [35]

43 Air to Water Ratio Air to water ratio is an importantparameter that has an impact on the removal rates of am-monia in water Mass transfer of ammonia into the air isaffected by the variance between ammonia concentrationlevel in liquid form and air phase [18] Lei et al discoveredthat the ammonia stripping efficiency of anaerobic effluentwas influenced by airwater ratios -e study found thathigher ammonia removal rate was achieved after 12 h at anairflow rate of 10 Lmin in comparison to airflow rates at3 Lmin and 5 Lmin [16] Nevertheless from the engi-neering stance Lei et al concluded that 5 Lmin for 1 L ofanaerobic effluent should be feasible due to the expensivemethod of using an airflow rate of 10 Lmin for 1 L ofwastewater with only 5 increment in removal efficienciesas compared to airflow rates from 5 Lmin until 10 Lmin[16] Next Campos et al revealed that the influence of air towater ratio on ammonia stripping performance at highertemperature was less significant as it resulted in ammoniaremoval greater than 91 at 60degC with an airflow rate be-tween 73 Lh and 120 Lh [32]

5 Issues Related to Ammonia StripperWastewater in IndustrialTreatment Application

-e ammonia stripping process has been successfullyemployed for many types of high-strength ammonia waste-water (Table 1) -e method refers to one that is controlledand unaltered by toxic compounds Nevertheless the am-monia stripping process has several drawbacks Among theissues involving the implementation of ammonia stripper toremove ammonia nitrogen in wastewater are fouling prob-lems sludge production and release of ammonia gas

51 Fouling Problems -e fouling problems in an ammoniastripper tower are caused by the formation of calciumcarbonate scale on the surface of the packing materials Scale

builds up on the packing materials thus leading to lowerstripping performance [32] Viotti and Gavasci found thatthe progressive scaling of the packing reduced stripper ef-ficiency from 98 to 80 after 6 months of operation -eformation of calcium carbonate scale on the packing ma-terial is due to the absorption of carbon dioxide from the airstream used for stripping Moreover the nature of calciumcarbonate varies from soft to hard Viotti and Gavasci thussuggested chemical cleaning to attain higher removal ofammonia from wastewater [36] -e high operation andmaintenance cost for air stripping can be attributed to theformation of calcium carbonate scale [37]

52 Sludge Production -e stripped effluent of ammoniastripping often fails in meeting the discharge standardsHigh sludge production and high alkalinity effluent asso-ciated with ammonia stripping generate additional treat-ment cost to this process However the calcium carbonatefrom the ammonia stripper sludge can be recovered Mareeand Zvinowanda for example used the flotation techniqueto recover calcium carbonate from wastewater treatmentsludge [38] As a result they discovered that floatationtechnique can potentially recover commercial grade lime-stone from wastewater sludge [38] Meanwhile He et alassessed the feasibility and performance enhancement fortreatment of alkaline-stripped effluent in aerated con-structed wetlands [39] -e constructed wetland was rela-tively simple and was empowered with eco-friendlytechnology so that it can withstand extreme pH wastewaterHe et al also found that the remediation of alkaline effluentwas feasible due to the high buffering capacity of the wet-lands [39]

53 Ammonia Gas -e ammonia stripping process resultsin ammonia release into the environment thus causingadditional environmental issues Ammonia recovery byabsorption is generally employed to prevent ammonia gasfrom being directly released into the environment Ferrazet al used sulphuric acid to recover the stripped ammoniafrom landfill leachate and revealed that 87 of the strippedammonia was recovered [22] Next Zhu et al discoveredthat under optimal condition of pH 12 airflow rate of050m3h temperature of 60degC and stripping time of120min 02molL of sulphuric acid can absorb approxi-mately 93 of the ammonia stripped per volume of theacetylene purification wastewater [25] Meanwhile Laureniet al concluded that ammonia stripping coupled with ab-sorption proved to be a feasible option for valorization ofnitrogen found in pig slurry -e by-product of this processwas ammonium sulphate which is a marketable product inthe agriculture arena as fertilizers [15]

6 Advances in Ammonia Stripping Process

Research on ammonia stripping enhancement has contin-ued unabated Recent development of ammonia removal byammonia stripping fall into the following ammonia strip-ping reactormodifications membrane contactor membrane

International Journal of Chemical Engineering 5

distillation ion exchange-stripping loop and microwave-assisted ammonia stripping

61 Ammonia Stripping Reactor Modications e con-struction of a particular ammonia stripping reactor is crucialas it has a strong impact on the whole treatment eciencyand the capital cost e conventional ammonia stripperreactor employs the packed column technology in which thepacking materials are used to enhance mass transfer betweenthe two phases e countercurrent-packed tower draws airthrough its openings at the bottom as the wastewater ispumped to the top of the packed tower Nonetheless thisprocess generates carbonate scales on the surface of thepacking materials which can aect ammonia removal ef-ciencies over time Apart from that the average depth ofthe packed bed tower can range from 61 until 76 metershence consuming a considerably large amount of spaceerefore some researchers have suggested the use of in-novative ammonia stripper reactors as a solution for ecientremoval of ammonia Among the innovative ammoniastripping reactors proposed were rotating packed bed [40]water-sparged aerocyclone reactor [41] and semibatch jetloop reactor [42]

611 Semibatch Jet Loop Reactor Removal of ammonia viaair stripping in a semibatch jet loop reactor was initiated byDegermenci et al in which ammonia is removed by a jet loopreactor so as to reduce the construction and operational costs

of the conventional ammonia stripping process It also hasa highermass transfer coecient and easier adaption from thepilot scale to the industrial-scale [42]e jet loop reactor wasconventionally applied for chemical or biochemical catalyzedreactions [43] e jet loop reactor oers exceptional mixingperformance at relatively low energy consumption for ap-plication that involves mass transfer [44]

An overall overview of the jet loop reactor is illustrated inFigure 4 In general the jet loop reactors were constructed inmany designs in terms of apparatus nozzle dimensionsdraft tube and entry position of the jet stream [45] eprinciple of the jet loop reactor is the utilization of thekinetic energy of high-velocity liquid jet to entrain the gasphase besides producing ne dispersion between the gas andthe liquid phases [46]

Degermenci et al have developed (4) to model the rate ofammonia removal via air-stripping technique in a jet loopreactor [42]

minuslnCLt

CL0KHQG

VL1minus eminus KLaSLe( ) QGKH( )( )[ ]t (4)

As a result the temperature and the gas ow rateexhibited signicant impacts on the ammonia removal rateby using the jet loop reactor Besides the jet loop appeared tobe more eective than the conventional ammonia stripperpacked tower e jet loop reactors can also be used for theconversion processes in treating biochemical wastewaterFarizoglu et al studied the treatment of cheese whey in a jetloop membrane reactor and achieved 84ndash94 of chemical

Aircompressor

Flow

met

er

Air inlet Circulation inlet

Flow

met

er

Liqu

id ci

rcul

atio

n lin

e

Circulationpump

Drainage

Nozzle

Heatexchanger

Drafttube

Impactplate

Figure 4 Schematic diagram of jet loop reactor [42]

6 International Journal of Chemical Engineering

oxygen demand removal which possessed the capability tooperate at high biomass concentrations [47] Next Eusebioet al investigated the treatment of winery wastewater byusing jet loop reactor and found that 80 of COD removaleciencies had been achieved within 24 hours [48]

612 Water-Sparged Aerocyclone Reactor Removal ofammonia via water-sparged aerocyclone reactor was rstdesigned by Quan et al e basic motivation for the in-novation was to increase the mass transfer rate and itsapplicability to treat wastewater with suspended solids [41]e water-sparged aerocyclone gas-liquid contactor can beused to address two major drawbacks of the conventionalpacked tower which are the process performance and thefouling problems in long operations

e water-sparged aerocyclone reactor is illustrated sche-matically in Figure 5ewater-sparged reactor is comprised oftwo concentric right-vertical tubes and a cyclone header on theupper section Wastewater is pumped into the porous sectionof the inner tube and sprayed into the centerline of the water-sparged aerocyclone reactor After that air is drawn into theaerocyclone at the top header of the inner tube

Quan et al adopted (5) developed byMatter-Muller et alto model the ammonia removal rate via air-strippingtechnique using the water-sparged aerocyclone [49]

minuslnCAt

CA0HAQG

VL1minus eminus KLaVL( ) QGHA( )( )[ ]t (5)

It was found that the water-sparged aerocyclone re-moved ammoniacal nitrogen total phosphorus and CODfrom wastewater at 910 992 and 520 respectivelyDue to the promising ammonia removal eciency by the

water-sparged aerocyclone reactor the structure of thewater-sparged aerocylone reactor was improvised by Quanet al to maximize the mass transfer eciency of the reactor[50] Quan et al also investigated the arrangement and thediameter of the jet holes in water-sparged aerocyclone re-actor thus concluding that the spray holes should bearranged in a square mode with 128 lc of optimum distancebetween two adjacent spray holes [50]

613 Rotating Packed Bed Reactors Ammonia removal viaair-stripping technique in the rotating packed bed reactorwas conducted by Yuan et al to enhance the high volumetricgas-liquid mass transfer coecients as well as to reduce thefouling problem the equipment size and the cost incurredas an attempt to overcome the shortcomings detected in theconventional ammonia stripping technique e rotatingpacked bed reactor appeared to be highly ecient in processintensication as it maximized the gas-liquid mass transfereciency via strong centrifugal acceleration [51]

In fact this particular method have been employed ina number of industrial applications namely absorption [52]synthesis of biodiesel [53] hydrogen sulde removal [54]and synthesis of nanoparticles [55]

e rotating packed bed is illustrated schematically inFigure 6 e rotating packed bed consists of a rotatingpacked bed gas and inuent controls e uent analyzer ande uent gas neutralizer [40]

Yuan et al used (6) to model the ammonia removal ratevia air stripping using the rotating packed bed reactor [40]

KLa QL

VB

ln (1minus(1S)) CLinCLout( ) +(1S)[ ]1minus(1s)

(6)

Air pump

Valves

Rotameters Porous section

Water tank

TextValves

Rotameters

Valves

Air pump

Gas-liquidseparator

Figure 5 Water-sparged aerocyclone reactor congurations

International Journal of Chemical Engineering 7

It was found that the rotating packed bed displayedhigher mass transfer eciency (123ndash1841h) when com-pared to other conventional and advanced gas-liquid con-tactors Nonetheless information concerning economicfeasibility of the operating conditions seemed scarce forpacked bed reactors in industrial wastewater treatment [40]

62 Membrane Contactors Ammonia stripping by usingmembrane contactor is another alternative that has lowertendency to fouling and requires no post e uent treatment[56] Relatively ammonia stripping by membrane contactorhas a higher rate of mass transfer than the conventionalammonia stripping due to its large contact surface area be-tween the wastewater and stripping solution [57] Semmenset al have derived (7) to model the ammonia removal rate byammonia stripping by using membrane contactor [56]

lnCo

CQt

V1minus e(minuskaLv)( ) (7)

Ahn et al have founded that the highest mass transfercoecient by using PTFE membrane was at 11times 10minus3mh atthe operating condition of 1000mgL of ammonia initialconcentration with no suspended solids and temperaturedierence [57] Hasanoglu et al investigated the ammoniaremoval by using at sheet and hollow ber membrane

contactors and founded that the circulation congurationsolution has a strong impact on the eciency of the process[58] Tan et al studied the ammonia removal by usingpolyvinylidene uoride (PVDF) hollow membranes andfounded that mass transfer rate is higher at higher feedvelocity but only up to 059ms [59] e ammonia strip-ping by using membrane contactor is illustrated schemati-cally in Figure 7

63 Membrane Distillation In recent years there has beenan increasing research on ammonia removal using mem-brane distillation Membrane distillation is driven by thetemperature dierence across the permeable membrane Itoers prospective recycling and reuse of industrial waste-water and higher process eciency Membrane distillationcan be grouped into four basic congurations namely directcontact membrane distillation [60] vacuum membranedistillation [61] air gap membrane distillation [62] andsweep gas membrane distillation [63] Liu et al reported thatdirect contact membrane distillation process ammonia re-moval rate was more than 85 at ammonia concentrationhigher than 400mgL but the removal rate decreased as theammonia concentration was above 1200mgL [60] El-Bourawi et al addressed that the most important operat-ing parameters that aect the ammonia removal eciency of

T

T

D

Liquid inGas out

Gas in

Liquid out

Toneutralization

tankFrom ammonia

storage tank

Thermocouple

Rotating packed bed shell

Motor

Rotatingpacked bed

In situammonia monitor

Figure 6 Rotating packed bed reactor conguration for ammonia stripping

8 International Journal of Chemical Engineering

the vacuum membrane distillation are feed temperaturefeed ow velocity and downstream pressure ey reportedthat ammonia removal eciencies higher than 90 wereachieved by using vacuum distillation [61] Eykens et alconducted a lab scale and pilot scale on ammonia strippingby direct contact and air gap membrane distillation It wasfounded that air gap membrane distillation has betterperformance and lower energy requirement than directcontact membrane distillation for larger scale applications[62] Xie et al investigated the ammonia removal by sweepgas membrane distillation e eciency of the process wasaected by the feed temperature feed ow rate and gas owrate It was founded that sweep gas membrane distillationshowed promising result with regards to high-eciencyindustrial process water recycling [63] e removal e-ciency of the sweep gas membrane distillation was reportedto be up to 97 Liu et al reported that the asymmetricPVDF membrane possesses excellent antifouling and sus-tainable ux in relative with the commercial PTFE (poly-tetrauoroethylene) membrane [64] It was founded that thePVDF membrane has less than 8 ux decline in 15 hourscontinuous operation [64]

64 Ion Exchange Loop Stripping Due to the problems as-sociated with operating and maintenance costs of airstripping [65] and the economic viability of the resins usedfor ion exchange [66] ion exchange and air stripping arecombined and called ion exchange loop-stripping e ionexchange loop stripping oers relatively lower operating andinvestment cost due to the reduced energy demands andequipment size reductions [67] e ion exchange loopstripping is illustrated schematically in Figure 8 Ion exchange

loop stripping is made up of the zeolite bed stripping columnand a scrubber

Ellersdorfer suggested that sodium hydroxide solutionmay be an alternative to sodium chloride to reduce chemicalconsumption [27] Ellersdorfer has investigated the technicalfeasibility of ammonium recovery by using ion exchangeloop stripping for sludge liquor from municipal wastewatertreatment plants and founded that it can be a feasible optionfor recovering ammonium from sludge liquor wastewatertreatment plants at above 900mgL [27]

65Microwave-AssistedAirStripping Reports onmicrowaveradiation that could be used to reduce ammonia nitrogen inwastewater have opened the door for research in the eld ofammonia stripping by microwave radiation Li Lin et alimplemented a pilot-scale study of ammonia removal byusing microwave radiation and founded that 80 ammoniaremoval from coke-plant wastewater can be achieved [26]Ata et al carried out studies on optimization of ammoniaremoval microwave-assisted air stripping and founded thatthe optimum conditions were at 1800mgL of initial con-centrations 75 Lmiddotminminus1 of airow rate 60degC of temperature500 rpm of stirring speed and 200W microwave output with60minutes of radiatione removal eciency of microwave-assisted ammonia stripping was able to achieve 942 underoptimized conditions [68] La et al evaluated the ecienciesof microwave-assisted ammonia removal from swine waste-water e highest removal eciency was obtained at 831Ammonia removal by microwave radiation oers high am-monia removal rate and lower reaction time [28] Howevermore research is needed for optimizing the power con-sumption of this wastewater treatment system

S S

FF

Membranemodule

Sulphuric acid sinktank

Ammonia feed tank inwater bath

Flowmeter Flowmeter

Pump Pump

Figure 7 Membrane contactor conguration for ammonia stripping [59]

International Journal of Chemical Engineering 9

7 Comparisons between Different AmmoniaStripping Processes

A comparison of various parameters related to the dierentammonia stripping processes based on literature was tab-ulated in Table 2

Table 2 shows that among the processes evaluated thepacked tower displayed a higher tendency towards foulingwhich decreased its eciency and increased the operationalcost of the whole process Besides the packed tower alsorequired higher air consumption when compared to theother ammonia stripper processes Besides that the packedtower also requires higher air consumption in relation withother ammonia stripper processes However the newerammonia stripping processes such as the semibatch jet loopreactor water-sparged aerocyclone reactor and rotatingpacked bed reactor have lower tendency towards foulingproblems Since the rotating packed bed reactor operates incontinuous ow Yuan et al suggested that larger rotatingpacked bed reactor has to be used to ensure higher processeciency [40] e water-sparged aerocyclone also oeredsimultaneous removal of other contaminants such as totalphosphorus and COD In addition the conventional packedtower displayed lower tolerance to total suspended solidsHence this technique is limited to applications with lowersuspended solids present in wastewater In this case theammonia stripping processes via semibatch jet loop reactorwater-sparged aerocyclone reactor and rotating packed bedreactor are deemed suitable for wastewater that containshigher total suspended solids It can also be seen that theimplementation membrane technologies in ammoniastripping process have been receiving considerable attentionin recent years Separation technologies using membraneincorporated into the ammonia stripping has higher process

eciency and oers prospective wastewater reclamation andreuse [72] However the membrane technologies are sub-jected to membrane fouling which results in a substantialincrease in hydraulic resistance [73] Hence future researchshould emphasize on the membrane fouling control and theperformance on a larger scale e microwave-assistedammonia stripping also showed higher process eciencyat 942 Nonetheless higher power consumption andrunning costs posed a serious challenge for the microwave-assisted ammonia stripping process [69]

8 Summary of Review and FutureResearch Perspectives

is review paper has revealed the inherent benets of theammonia stripping process in comparison to the conven-tional packed tower Nevertheless pilot-scale investigationand economic evaluations are required before applying fullscale of the ammonia stripping process Moreover futureresearches can specically focus on the following threeaspects

First the structure optimization for the each of theammonia stripping process reactors deserves further re-search Since most of the new advanced ammonia strippingreactors were rst designed for various types of applicationsit is important that these reactors are tailor-made for am-monia stripping processes One of the most important as-pects of ammonia stripping reactorrsquos development refers tothe higher air-stripping eciency at a lower operational costHence structure optimization can illustrate a detailed designguide for optimized gas-liquid contactors

Second more studies are needed to evaluate the capitaland operational costs for advanced liquid-gas contactors inammonia stripping Since studies regarding these important

Zeolite bed Zeolite bedStripping column

Scrubber

Process water

Sludge liquor

NaOH

H2SO4

(NH4)2SO4solution

Na+ solution (NaCl)T~ 60ndash80 pH 10

Figure 8 Ion exchange loop stripping congurations [27]

10 International Journal of Chemical Engineering

Tabl

e2

Com

parisonof

thedifferent

ammon

iastripp

ingprocesses

Ammon

iastripp

ing

processes

Wastewater

volume

Process

efficiency

()

Removal

ofother

contam

inant

Suspendedsolid

stolerance

Fouling

prob

lem

Stripp

ing

time(h)

Airflo

wrate

Masstransfer

coeffi

cient

References

Packed

tower

1000

75Not

available

Low

High

35

25(airto

water

ratio

)042h

[69]

Semibatch

jetloop

reactor

9L

97Not

available

High

Low

58

56(airto

water

ratio

)063h

[42]

Water-sparged

aerocyclon

e10

L98

TotalP

andCOD

High

Low

35

114

(airto

water

ratio

)12h

[41]

Rotatin

gpacked

bedreactor

0025ndash

001

Lmin

64Not

available

High

Low

00037

1800

Lmin

(con

tinuo

usflo

w)

123h

[40]

Mem

branecontactor

094

L9983

Not

available

Low

High

10Not

available

0011mh

[57]

Mem

branedistillation

1L

985

Not

available

Low

High

4hNot

available

0079

[70]

Ionexchange

loop

stripp

ing

2L

846

Not

available

low

High

25

Not

available

Not

available

[27]

Microwaveradiation

075

L942

Not

Available

High

Not

available

00167

10(airto

water

ratio

)3354

[71]

International Journal of Chemical Engineering 11

aspects are in scarcity and such information is vital toengineers and decision-makers in-charge of devising newtechnologies more evaluations are required to look into thefull cost analysis of the advanced gas-liquid contactors so asto determine its economic feasibility for specific wastewatertreatment scenario Additionally a detailed pilot study onthe advanced gas-liquid contactors is also crucial to identifypotential hiccups and allay investor concerns

-ird two of the advanced gas-liquid contactors (ro-tating packed bed and water-sparged aerocyclone) utilizevortex to induce gas-liquid mass transfer Hence there isa possibility of harvesting energy from these water vortexesAs such it has been proposed that the advanced gas-liquidcontactors have to be integrated with water vortex generator-is may be a possible strategy to promote energy self-sufficient ammonia stripping process Nishi and Inagakiinvestigated the vortex-type water turbine to generateelectricity and discovered its ability in generating electricityby using a low head and a low flow rate using a simplestructure [74] -is ammonia stripping reactor liquidcoupled with water vortex generator seems to be a prom-ising technology for energy self-sufficient wastewatertreatment and demands further research

9 Conclusion

Ammonia stripping process is suitable for treating waste-water that contains high concentration of ammonia andtoxic compounds with the merits of simpler operation highefficiency and excellent treatment stability thus displayingan exceptional application potential for industrial waste-water treatment -e success of an ammonia strippingprocess is greatly dependent on temperature pH and air towater ratio As such the selection of optimized operatingparameter is vital for the ammonia stripper to achieve higherefficiency -e different types of ammonia stripping reactorsfor ammonia stripping are presented in this review articleIts outstanding mass transfer performance and higher totalsuspended solids tolerance discriminate the conventionalpacked tower for ammonia stripping method -e followingdirections are proposed for further research First thestructure optimization should be done for each of theammonia stripping processes for higher air-stripping effi-ciency at a lower operational cost Secondly full cost analysisof the advanced ammonia stripper processes is needed toevaluate its economic feasibility for specific wastewatertreatment scenario Lastly the integration of advanced gas-liquid contactors with vortex power generator for an energyself-sufficient wastewater treatment is proposed

Conflicts of Interest

-e authors declare that they have no conflicts of interestregarding the publication of this paper

References

[1] S R M Kutty S N I Ngatenah M H Isa and AMalakahmadldquoNutrients removal from municipal wastewater treatment plant

effluent using Eichhornia crassipesrdquo Engineering and Technologyvol 3 no 12 pp 826ndash831 2009

[2] V D Leite S Prasad W S Lopes J T Sousa andA J M Barros ldquoStudy on ammonia stripping process ofleachate from the packed towerrdquo Journal of Urban and En-vironmental vol 7 no 2 pp 21ndash222 2013

[3] T A Pressley D F Bishop A P Pinto and A F CasselldquoAmmonia-nitrogen removal by breakpoint chlorinationrdquo1973 httpsnepisepagovExeZyPDFcgi91020N8GPDFDockey91020N8GPDF

[4] BatellendashNorthwest Richland ldquoWastewater ammonia removalby ion exchangerdquo 1971 httpsnepisepagovExetiff2pngcgi9100GI2RPNG-r+75+g+7+D3A5CZYFILES5CINDEX20DATA5C70THRU755CTIFF5C000017085C9100GI2RTIF

[5] M Mondor L Masse D Ippersiel F Lamarche andD I Masse ldquoUse of electrodialysis and reverse osmosis for therecovery and concentration of ammonia from swine manurerdquoBioresource Technology vol 99 no 15 pp 7363ndash7368 2008

[6] R G Rice C M Robson G W G Miller J C Clark andW Kohn ldquoBiological processes in the treatment of municipalwater suppliesrdquo 1982 httpsnepisepagovExeZyPDFcgi9100LYD1PDFDockey9100LYD1PDF

[7] I Ozturk M Altinbas I Koyuncu and Y C Gomec ldquoAd-vanced physico-chemical treatment experiences on youngmunicipal landfill leachatesrdquo Waste Management vol 23no 5 pp 441ndash446 2003

[8] USEPA ldquoWastewater technology fact sheet ammonia strip-pingrdquo 2000 httpsnepisepagovExeZyPDFcgiP10099PHPDFDockeyP10099PHPDF

[9] L K Wang Y-T Hung and N K Shammas AdvancedPhysicochemical Treatment Processes Handbook of Environ-mental Engineering Vol 4 -e Humana Press Inc TotowaNJ USA 2006

[10] T P OrsquoFarell F P Frauson A F Cassel and D F BishopldquoNitrogen removal by ammonia strippingrdquo Journal of WaterPollution Control Federation vol 44 no 8 pp 1527ndash15351972

[11] M Raboni V Torretta O Viotti and G Urbini ldquoExperi-mental plant for the chemico-physical treatment ofgroundwater polluted by MSW leachate with ammonia re-coveryrdquo Revista Ambiente amp Agua vol 8 no 3 pp 22ndash322013

[12] G Sarraco and G Genon ldquoHigh temperature ammoniastripping and recovery from process liquid wastesrdquo Journal ofHazardous Materials vol 37 no 1 pp 191ndash206 1994

[13] A Alitalo A Kyro and E Aura ldquoAmmonia stripping ofbiologically treated liquid manurerdquo Journal of EnvironmentalQuality vol 41 no 1 pp 273ndash20 2012

[14] K C Cheung L M Chu and M H Wong ldquoAmmoniastripping as pretreatment for landfill leachaterdquo Water Airand Soil Pollution vol 94 no 1-2 pp 209ndash221 1995

[15] M Laureni J Palatsi M Llovera and A Bonmati ldquoInfluenceof pig slurry characteristics on ammonia stripping efficienciesand quality of the recovered ammonium-sulfate solutionrdquoJournal of Chemical Technology and Biotechnology vol 88no 9 pp 1654ndash1662 2013

[16] X H Lei N Sugiura C P Feng and T Maekawa ldquoPre-treatment of anaerobic digestion effluent with ammoniastripping and biogas purificationrdquo Journal of HazardousMaterials vol 145 no 3 pp 391ndash397 2007

[17] M A Rubia M Walker S Heaven C J Banks and R BorjaldquoPreliminary trials of in situ ammonia stripping from sourcesegregated domestic food waste digestate using biogas effect

12 International Journal of Chemical Engineering

of temperature and flow raterdquo Bioresource Technologyvol 101 no 24 pp 9486ndash9492 2010

[18] A Bonmati and X Flotats ldquoAir stripping of ammonia frompig slurry characterisation and feasibility as pre- or post-treatment to mesophilic anaerobic digestionrdquo Waste Man-agement vol 23 no 3 pp 261ndash272 2003

[19] A Limoli M Langone and G Andreottola ldquoAmmonia re-moval from raw manure digestate by means of a turbulentmixing stripping processrdquo Journal of Environmental Man-agement vol 176 pp 1ndash10 2016

[20] G D Boardman and P J McVeigh ldquoUse of air strippingtechnology to remove ammonia from biologically treated bluecrab processing wastewaterrdquo Journal of Aquatic Food ProductTechnology vol 7 no 4 pp 81ndash97 1998

[21] B V Prather ldquoWastewater aeration may be key to moreefficient removal of impuritiesrdquo Oil and Gas Journal vol 57pp 78ndash89 1959

[22] F M Ferraz J Povinelli and E M Veira ldquoAmmonia removalfrom landfill leachate by air stripping and absorptionrdquo En-vironmental Technology vol 34 no 15 pp 2317ndash2326 2013

[23] L Zhang Y W Lee and D Jahng ldquoAmmonia stripping forenhanced biomethanization of piggery wastewaterrdquo Journal ofHazardous Materials vol 199-200 pp 36ndash42 2012

[24] V K Minocha and A V S P Rao ldquoAmmonia removal andrecovery from urea fertilizer plant wasterdquo EnvironmentalTechnology Letters vol 9 no 7 pp 655ndash664 1988

[25] L Zhu D Dong X Hua Z Guo and D Liang ldquoAmmonianitrogen removal from acetylene purification wastewater byair strippingrdquo Water Science Technology vol 75 no 11-12pp 2538ndash2545 2017

[26] Li Lin J Chen Z Q Xu et al ldquoRemoval of ammonia nitrogenin wastewater by microwave radiation a pilot-scale studyrdquoJournal of Hazardous Materials vol 168 no 2-3 pp 862ndash8672009

[27] M Ellersdorfer ldquo-e ion-exchange-loop stripping processammonium recovery from sludge liquor using NACl-treatedclinoptilolite and simultaneous air strippingrdquo Water Scienceand Technology vol 77 no 3 pp 695ndash705 2017

[28] J H La T Kim J K Jang and I S Change ldquoAmmonianitrogen removal and recovery from swine wastewater bymicrowave radiationrdquo Environmental Engineering Researchvol 19 no 4 pp 381ndash385 2014

[29] A Serna-Maza S Heaven and C J Banks ldquoIn situ biogasstripping of ammonia from a digester using a gas mixingsystemrdquo Environmental Technology vol 38 no 24pp 3216ndash3224 2017

[30] C Collivignarelli G Bertanza M Baldi and F AvezzuldquoAmmonia stripping from MSW landfill leachate in bubblereactors process modelling and optimizationrdquo Waste Man-agement amp Research vol 16 no 5 pp 455ndash466 1998

[31] K Kojima S Zhang and T Hiaki ldquoMeasuring methods ofinfinite-dilution activity coefficients and a database for sys-tems including waterrdquo Fluid Phase Equilibria vol 131 no 1-2pp 145ndash179 1997

[32] J C Campos A P Moura L Costa F V YokoyamaD F Arouja and M C Cammarota ldquoEvaluation of pHalkalinity and temperature during air stripping process forammonia removal from landfill leachaterdquo Journal of Envi-ronmental Science and Health vol 48 no 9 pp 1105ndash11132013

[33] D Hidalgo F Corona J M Martin-Marroquin J D Alamoand A Alicia ldquoResource recovery from anaerobic digestatestruvite crystallisation versus ammonia strippingrdquoDesalinationand Water Treatment vol 57 no 6 pp 2626ndash2632 2015

[34] G Markou M Agriomallou and D Georgakakis ldquoForcedammonia stripping from livestock wastewater the influenceof some physico-chemical parameters of the wastewaterrdquoWater Science amp Technlogy vol 75 no 3-4 pp 686ndash692 2016

[35] S Gustin and R Marinsek-Logar ldquoEffect of pH temperatureand air flow rate on continuous ammonia stripping of theanaerobic digestion effluentrdquo Process Safety and Environ-mental Protection vol 89 no 1 pp 1ndash66 2011

[36] P Viotti and R Gavasci ldquoScaling of ammonia strippingtowers in the treatment of groundwater polluted by municipalsolid waste landfill leachate study of the causes of scaling andits effects on stripping performancerdquo Revista Ambient Aguavol 10 no 2 pp 241ndash252 2015

[37] C T Whitman G T Mehan G H Grubbs et al ldquoDevel-opment document for the proposed effluent limitationsguidelines and standards for the meat and poultry productsindustry point source categoryrdquo 2002 httpsnepisepagovExeZyPDFcgi20002F0QPDFDockey20002F0QPDF

[38] J P Maree and C M Zvinowanda ldquoRecovery of calciumcarbonate from wastewater treatment sludge using a flotationtechniquerdquo Journal of Chemical Engineering Process Tech-nology vol 3 no 2 pp 1ndash6 2012

[39] K L He S B Wu L C Guo Z S Ajmal H Z Luo andR J Dong ldquoTreatment of alkaline stripped effluent in aeratedconstructed wetlands feasibility evaluation and performanceenhancementrdquo Water vol 8 no 9 pp 1ndash11 2016

[40] M H Yuan Y H Chen J Y Tsai and C Y ChangldquoAmmonia removal from ammonia-rich wastewater by airstripping using a rotating packed bedrdquo Process Safety andEnvironmental Protection vol 102 pp 777ndash785 2016

[41] X J Quan and Z L Cheng ldquoMass transfer performance ofa water-sparged aerocyclone reactor and its application inwastewaterrdquo Journal of Hazardous Materials vol 170 no 2-3pp 983ndash938 2009

[42] N Degermenci O N Ata and E Yildiz ldquoAmmonia removalby air stripping in a semi-batch jet loop reactorrdquo Journal ofIndustrial and Engineering Chemistry vol 18 no 1pp 399ndash404 2012

[43] A Behr and M Becker ldquoMultiphase catalysis in jetloop-re-actorsrdquo Chemical Engineering Transactions vol 17 pp 141ndash144 2009

[44] H-J Warnecke M Geisendorfer and D C Hempel ldquoMasstransfer behaviour of gas-loop reactorsrdquo Acta Biotechnologyvol 11 no 1 pp 306ndash311 1988

[45] K H Tebel and P Zehner ldquoFluid dynamic description of jetloop reactors in multiphase operationrdquo Chemical EngineeringTechnology vol 12 no 1 pp 274ndash280 1989

[46] C A M C Dirix and K Van de Wiele ldquoMass transfer in jetloop reactorsrdquo Chemical Engineering Science vol 45pp 2333ndash2340 1990

[47] B Farizoglu B Keskinler E Yildiz and A Nuhoglu ldquoCheesewhey treatment performance of anaerobic jet loop membranebioreactorrdquo Process Biochemistry vol 39 pp 2283ndash22912004

[48] A Eusobio M Petruccioli M Lageiro F Federici andJ C Duarte ldquoMicrobial characterisation of activated sludge injet-loop bioreactors treating winery wastewatersrdquo Journal ofIndustrial Microbiology amp Biotechnology vol 31 no 1pp 29ndash34 2004

[49] C Matter-Muller W Gujer and W Giger ldquoTransfer ofvolatile subtances from water to the atmosphererdquo WaterResearch vol 15 no 11 pp 1271ndash1279 1981

[50] X J Quan Z L Cheng F Xu F C Qiu D Li and Y P YanldquoStructural optimization of the porous section in awater-sparged

International Journal of Chemical Engineering 13

aerocyclone reactor to enhance the air-stripping efficiency ofammoniardquo Journal of Environmental Chemical Engineeringvol 2 no 2 pp 1199ndash1206 2014

[51] D P Rao A Bhowal and P S Goswami ldquoProcess in-tensification in rotating packed beds (HIGEE) an appraisalrdquoIndustrial Engineering Chemical Resource vol 43 no 4pp 1150ndash1162 2004

[52] Y Sun T Nozawa and S Furusaki ldquoGas holdup and vol-umetric oxygen transfer coefficient in three-phase fluidizedbed reactorrdquo Journal of Chemical Engineering vol 21 no 1pp 15ndash20 1988

[53] J T Xu C S Liu M Wang et al ldquoRotating packed bedreactor for enzymatic synthesis of biodieselrdquo BioresourceTechnology vol 224 pp 292ndash297 2017

[54] K Guo J Wen Y Zhao et al ldquoOptimal packing of a rotatingpacked bed for H2S removalrdquo Environmental Science ampTechnology vol 48 no 12 pp 6844ndash6849 2014

[55] J F Chen Y H Wang F Guo X M Wang and Z ChongldquoSynthesis of nanoparticles with novel technology high-gravity reactive precipitationrdquo Industrial Engineering Chem-istry Resource vol 39 no 4 pp 948ndash954 2000

[56] M J Semmens D M Foster and E L Cussler ldquoAmmoniaremoval from water using microporous hollow fibersrdquoJournal of Membrane Science vol 51 no 1-2 pp 127ndash1401990

[57] Y T Ahn Y H Hwang and H S Shin ldquoApplication of PTFEmembrane for ammonia removal in membrane contactorrdquoWater Science and Technology vol 63 no 12 pp 2944ndash29482011

[58] A Hasanoglu J Romero B Perez and A Plaza ldquoAmmoniaremoval from wastewater streams through membrane con-tactors experimental and theoretical analysis of operationparameters and configurationrdquo Chemical Engineering Journalvol 160 no 2 pp 530ndash537 2010

[59] X Y Tan S P Tan W K Teo and K Li ldquoPolyvinylidenefluoride (PVDF) hollow fibre membranes for ammonia re-moval from waterrdquo Journal of Membrane Science vol 271no 1-2 pp 59ndash68 2006

[60] Q L Liu Z HWang LW Chen and P P Wang ldquo-e effectof ammonia initial concentration in membrane distillationprocess for high ammonia concentration wastewater treat-mentrdquo in Proceedings of the International Conference onConsumer Electronics Communications and Networks(CECNet) pp 1795ndash1797 Beijing China March 2011

[61] M S El-Bourawi M Khayet R Ma Z Ding Z Li andX Zhang ldquoApplication of vacuum membrane distillation forammonia removalrdquo Journal of Membrane Science vol 301no 1-2 pp 200ndash209 2007

[62] L Eykens I Hitsov K De Sitter C Dotremont L Pinoy andB V D Bruggen ldquoDirect contact and air gap membranedistillation differences and similarities between lab and pilotscalerdquo Desalination vol 422 pp 91ndash100 2017

[63] Z L Xie T Duong M Hoang N Cuong and B BoltoldquoAmmonia removal by sweep gas membrane distillationrdquoWater Research vol 43 no 6 pp 1693ndash1699 2009

[64] Y F Liu T H Xiao C H Bao J F Zhang and X YangldquoPerformance and fouling study of asymmetric PVDFmembraneapplied in the concentration of organic fertilizer by direct contactmembrane distillationrdquo Membranes vol 8 no 1 p 9 2018

[65] A G Capodaglio P Hlavinek and M Raboni ldquoPhysico-chemical technologies for nitrogen removal wastewatera reviewrdquo Revista Ambiente Agua vol 10 no 3 2015

[66] Q Deng B R Dhar E Elbeshbishy and H S Lee ldquoAm-monium nitrogen removal from the permeates of anaerobic

membrane bioreactors economic regeneration of exhaustedzeoliterdquo Environmental Technology vol 35 no 16 pp 2008ndash2017 2014

[67] M Ellersdorfer ldquoRecovery of ammonia from liquid digestatefor NOx removalrdquo in Proceedings of the 11th DepoTechConference vol 835 pp 367ndash372 Leoben Austria November2012

[68] O N Ata A Kanca Z N Demir and V Yigit ldquoOptimizationof ammonia removal from aqueous solution by microwave-assisted air strippingrdquoWater Air Soil Pollition vol 228 no 11pp 448ndash458 2017

[69] L Le H WWang and H H Lu ldquoNitrogen removal using airstripping tower in urban wastewater treatment plantrdquo ChinaWastewater vol 22 pp 92ndash99 2006

[70] Q Xia Y B Yun J J Chen D Qu and C L Li ldquoTreatment ofammonia nitrogen wastewater by membrane distillationPVDF membranerdquo Desalination and Water Treatmentvol 61 pp 126ndash135 2016

[71] O N Ata K Aygun H Okur and A Kanca ldquoDeterminationof ammonia removal from aqueous solution and volumetricmass transfer coefficient by microave-assisted air strippingrdquoInternational Journal of Science and Technology vol 13 no 10pp 2459ndash2466 2016

[72] S H You D H Tseng and G L Guo ldquoA case study on thewastewater reclamation and reuse in the semiconductor in-dustryrdquo Resources Conservation and Recycling vol 32 no 1pp 73ndash81 2001

[73] M Mulder Basic Principal of Membrane Technology KluwerAcademic Publisher Norwell MA USA 2nd edition 1996

[74] Y Nishi and T Inagaki ldquoPerformance and flow field ofgravitation vortex type water turbinerdquo International Journalof RotatingMachinery vol 2017 Article ID 2610508 11 pages2017

14 International Journal of Chemical Engineering

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