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Comparison of treatment potential of electrocoagulation of distillery effluent with and without activated Areca catechu nut carbon

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Journal of Hazardous Materials B137 (2006) 1803–1809 Comparison of treatment potential of electrocoagulation of distillery effluent with and without activated Areca catechu nut carbon N. Kannan a,∗ , G. Karthikeyan b , N. Tamilselvan c a Department of Chemistry, Ayya Nadar Janaki Ammal College (Autonomous), Sivakasi 626124, Tamil Nadu, India b Department of Chemistry, Gandhigram Rural Institute, Gandhigram 624302, Tamil Nadu, India c Department of Civil Engineering, Mepco Schlenk Engineering Col
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  Journal of Hazardous Materials B137 (2006) 1803–1809 Comparison of treatment potential of electrocoagulation of distilleryeffluent with and without activated  Areca catechu  nut carbon N. Kannan a , ∗ , G. Karthikeyan b , N. Tamilselvan c a  Department of Chemistry, Ayya Nadar Janaki Ammal College (Autonomous), Sivakasi 626124, Tamil Nadu, India b  Department of Chemistry, Gandhigram Rural Institute, Gandhigram 624302, Tamil Nadu, India c  Department of Civil Engineering, Mepco Schlenk Engineering College, Sivakasi 626005, Tamil Nadu, India Received 19 January 2006; received in revised form 5 May 2006; accepted 8 May 2006Available online 23 May 2006 Abstract Physico-chemicalcharacteristicsofdistilleryeffluentsampleshavebeendetermined.Thewaterqualityparameters(WQPs)measuredarecolour,pH, electrical conductivity, turbidity, total dissolved solids (TDS), chloride, total hardness (THA), calcium, iron, bio-chemical oxygen demand(BOD) and chemical oxygen demand (COD). Almost all the values of WQPs of the distillery effluents have been found to be very high and wellabove the permissible limit suggested by Bureau of Indian Standards (BIS). Electrocoagulation (EC) technique is employed to treat the distilleryeffluents. Removal efficiency of WQPs is compared by adopting EC technique with and without the addition of indigenously prepared activatedareca nut [botanical name:  Areca catechu ; kotta pakku, in (vernacular)] carbon (AAC). About 99% of turbidity has been removed in both the cases.The experimental results also revealed that the WQPs like EC, TDS, etc. of the effluents could be reduced. Loss of weight of sacrificial electrode(anode) is also ascertained. EC with AAC is found to be more effective than EC without AAC.© 2006 Elsevier B.V. All rights reserved. Keywords:  Electrocoagulation; Activated areca nut carbon (  Areca catechu ) (AAC); Aluminium and iron electrodes; Distillery effluent 1. Introduction Therearenearly290distilleryunitspresentinIndia,ofwhich,17unitsarelocatedinTamilNadu.Allthesedistilleryindustriesuse molasses obtained from sugar industries as raw materialand generate large amount of effluent. Alcohol is separated bydistillation and the residual liquor is discharged as effluent. Thiseffluent,calledasspentwash,ishot,highlyacidic,darkcolouredandcontainshighpercentageoforganicandinorganicmatter[1],bothinsuspendedanddissolvedforms.Foreverylitreofalcoholproduction,about12–14lofwastewaterisbeingdischarged[2],which affect the soil and groundwater resources of the region.The prolonged discharge of the effluent renders toxicity to thesoil on the same part of the land [3].Thermal degradation of reducing sugars and the amino com-pounds is mainly responsible for the dark colour of distillery ∗ Corresponding author. Tel.: +91 4562 254100 (O)/246162 (R);fax: +91 4562 254970.  E-mail addresses:  vgr anjac@sancharnet.in, dr n kannan@yahoo.co.in (N. Kannan). effluents. This is because of the formation of melanoidins andpolyphenolic compounds or complexes. The dark colour willprevent the penetration of sunlight and will damage the aquaticeco system [4,5]. Melanoidin is not easily decomposed by the conventional biological treatment processes and so it produceshighchemicaloxygendemand(COD),whichisamajorproblemfor pollution control [6].Though,thedistilleryeffluentcontainsnotoxicsubstances,ithashighamountoforganicmatter,whichcancausehighamountof BOD and COD. Further, it depletes dissolved oxygen (DO)in the receiving water bodies. This depletion of DO induces thewater bodies to be highly odoured due to the destruction of floraand fauna. In the long run, the water body will become a deadpool of water due to eutrophication. All these facts reveal thatthe distillery effluent is highly polluted and it needs treatmentbefore discharge into the natural water stream or land.Conventionalmethodsdealingwiththetreatmentofdistilleryeffluentsconsistofvariouscombinationsofbiological,chemicalandphysicalmethods.Severalmethodsviz.,filtrationusingvari-ety of filters, coagulation by added chemicals, reverse osmosis,adsorption,ionexchangeprocess,dissolvedairflotationmethod 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.jhazmat.2006.05.048  1804  N. Kannan et al. / Journal of Hazardous Materials B137 (2006) 1803–1809 etc., are available for treating distillery effluents [7]. Many of  these methods are using more quantity of water and they areeither pollutant specific, less efficient and more expensive thansimple discharge without any effluent treatment. Hence, thesemethods become obsolete and new methods need to be sought.Electrocoagulation (EC) in conjunction with electrofloccula-tion is one of the methods, which is simple, but very effectivefor treating many turbid waters and wastewaters [8]. Various authors have proved the removal of pollutants by EC tech-nique successfully. Mention may be made on the treatmentof potable water [9,10], textile wastewater [11–13], tar, sand and oil shale wastewater [14], urban wastewater [15], tannery wastewater[16],restaurantwastewater[17]andfoodwastewater [18]. EC has also been used to remove dyestuff  [19–22], arsenic [23] and nitrate [24] f rom wastewater. This process is charac- terised by an effective removal of pollutants [25–28], compact size of the equipment, simplicity in operation, low capital andoperating cost [29]. This process is more effective than other methods because of the subsequent electroflocculation [25–28].In electroflocculation, the pollutants are removed by the hydro-gen bubbles, which are generated during EC. These bubblesupliftthecoagulated/agglomeratedpollutantparticlestothesur-face, from where it could easily be removed. It is also reportedthat electrolytically added aluminium ions are more active thanchemically added aluminium ions [30]. This means that, less aluminium is required and electrocoagulation could be used totreat a number of wastewaters, which could not be handled bychemical flocculants such as alum.This process is used to remove suspended (fine) solids anddissolved molecules. The suspended solids include bacteria,algae, clay and spores. The dissolved matters are organic matter(humes), dye molecules, detergent molecules and other materi-als. We report that the addition of indigenously prepared acti-vated areca nut carbon (AAC) during EC enhances the rate of removal of turbidity to the order of 99% in the distillery efflu-ent. The results of EC with and without AAC by employing iron(cathode)andaluminium(anode)electrodes,intheelectrochem-ical treatment of distillery effluent are presented and discussedhere. 2. Experimental Distillery wastewater samples for this study have been col-lected from the discharge stream of a distillery industry situatedin Tirunelveli district of Tamil Nadu, India. During sampling,the samples have been collected in a 2l polythene can, once in4 for 24h and they are mixed in equal proportions to get uni-form homogeneous sample [31]. Random selection procedure was adopted for the selection of both sampling unit and thesampling point in a given site [32]. The sampling of effluents and its characterisation were carried out as per the method rec-ommended by APHA [32] and methods reported in literatures[31–33]. The values of physico-chemical characteristics of dis-tillery industrial effluent are shown in Table 1. The effluent was first filtered using a screen filter (bar and then fine screen) toremove large suspended visible solids before carrying out fur-ther studies. The experimental set-up with laboratory prototypereactor is schematically shown in Fig. 1.Thermostatically controlled inclined electrochemical reactor(conical flask with spout, 250ml capacity) made up of borosil-icate glass was placed inside a beaker (500ml capacity), whichwas then placed on magnetic stirrer (Remi-1MLH). The elec-trochemicalreactorconsistedoftwomonopolarelectrodes,onecathode and another anode viz., iron (stainless steel—SS) andaluminium,respectively.Boththeelectrodesarepurchasedfromthe local market (purity: Al=99.5%, Fe=99%). The dimen- Fig. 1. Schematic diagram of experimental set-up.   N. Kannan et al. / Journal of Hazardous Materials B137 (2006) 1803–1809  1805Table 1Range and average values of WQPs of distillery effluents, limit for drinking purpose and discharge of industrial effluents, prescribed by BISS. no. Parameter a Range(minimum − maximum)Average Limit prescribedby IS:10500, 1983Limits prescribed by IS forindustrial effluents dischargedAllowable MaximumpermissibleInto inland surfacewater IS:2490,1974Into onland forirrigation IS:3307,1977Into public sewers1. Temperature ( T  ) 30.4–32.8 31.92 – – Shall not exceed40 ◦ C– 45 ◦ C at the pointof discharge2. pH 5.71–6.86 6.22 6.5–8.5 6.5–8.5 5.5–9.0 5.5–9.0 5.5–9.03. Electrical conductivityat 25 ◦ C2800–12610 5157.50 – – – 3000 –4. Alkalinity 820–1125 952.17 – – – – –5. Total suspended solids 3103.3–21183.3 7168.89 – – 100 200 6006. Total dissolved solids 6763.3–39903.3 15390.55 500 1500 2100 2100 21007. Total hardness 1220–7460 2880 300 600 – – –8. Temporary hardness 100–560 270 – – – – –9. Permanent hardness 1070–6920 2610 – – – – –10. Chlorides 816.5–2996.2 1577.38 250 1000 1000 600 100011. Sulphates 99.9–1907.8 659.48 150 400 1000 1000 100012. Phosphates 9920–20160 14693.33 – – 5 b – –13. Sodium 393.1–779.6 570.68 – – – 60 6014. Potassium 594.9–1004.5 823.38 – – – – –15. Calcium 276–972 506.67 75 200 – – –16. Magnesium 127.2–1207.2 387.20 30 100 – – –17. Iron 8.66–40.66 16.97 0.3 1.0 3 3 318. BOD 5636.2–14820.4 9776.81 – – 30 100 c 350 c 19. COD 8032.1–28842.4 14555.12 – – 250 d – –20. Total solids 9963.3–60086.7 22226.11 – – – – –21. Total fixed solids(inorganic solids)3370–18566.7 7696.11 – – – – –22. Total volatile solids(organic solids)6006.66–41520 14530 – – – – –23. WQI 3441.1–6348.3 4882.48 – – – – –Ref. [34]. a Unit: in mg/l or ppm, except pH, EC (  mho/cm) and WQI. b If all these pollutants are present at the maximum permissible concentration, the effluent may lead to ethrophication. Therefore data on ecological changes shouldbe monitored. c Further relaxation may be decided by the concerned agencies. d For paper, dyestuff, pesticide and certain chemical and petrochemical industries, these values are relaxed; it shall be ensured that the effluent passes the test forlethal toxicity as given in IS:6582, 1972. sion of iron (stainless steel cathode) electrode and aluminium(anode) electrode is 104mm × 25mm × 6mm each. The spac-ingbetweentheelectrodeswasmaintainedat28mm.Theweightofironelectrode(electronicbalance,anamedmake,100gcapac-ity, 0.001g accuracy), before and after EC without AAC hasbeen noted to be 72.544 and 72.577g (+0.033g is gained for30min of EC). This is because of little electro-deposition of aluminium ions on SS cathode. Aluminium electrode looses0.098g from its initial weight (initial weight=42.682g; finalweight=42.584g) for 30min of EC without AAC. During EC,Al 3+ ions from aluminium electrode are leached out and takenpart in coagulation process. It is settled as sediment or floatedon the surface (due to bubbles) and it could easily be removed.After 60min of EC without AAC, the iron and aluminium elec-trodes weigh 72.604 and 42.512g, respectively. ConsideringEC with AAC, the iron electrode gain 0.002g from its initialweight (initial weight=72.543g; final weight=72.545g) andthe aluminium electrode loose 0.072g from its initial weight(initial weight=42.503g; final weight=42.431g) after 30min.After 60min, the iron and aluminium electrode show 72.549and 42.363g, respectively. The electrodes are cleaned initiallywith acetone and then washed [20] with a solution of concen-trated HCl (100ml) and hexamethylene tetramine (2.8% w/v;200ml). The electrodes are connected to a DC power supply(30V, 2A—Sigma electronics, Bangalore, India).About 200ml of well-mixed, screened, homogeneous dis-tillery effluent was taken in a conical shaped 250ml borosilicateelectrolytic cell (conical flask). The temperature of the effluentbefore EC was noted to be 30 ◦ C. The temperature was main-tained throughout EC (deviation  ± 1 ◦ C). The current densitywas adjusted to a desired value (182A/m 2 ). The whole set-upwas placed on a magnetic stirrer and the sample under studywas subjected to slow constant stirring. EC has been continuedwith fresh set-up and the WQPs have been determined at everyinterval of 10 up to 60min.Simultaneously, similar set-up was made with another elec-trolytic cell with intermittent addition of 1g of indigenouslyprepared AAC powder (size: 420  m) with constant, slow stir-  1806  N. Kannan et al. / Journal of Hazardous Materials B137 (2006) 1803–1809 ring to facilitate effective coagulation and agglomeration of colloidal particles. The areca nut particles have been cut intosmall pieces, washed, dried, carbonised in a muffle furnace (at250 ◦ C), digested and activated for 30min (2N HNO 3 ), andsieved (Jayant sieve, India) to a constant particle size (420  m).Similarly, EC was continued with fresh set-up and the parame-ters have been determined at the interval of 10 up to 60min.During EC, suspended matter in both the cell was removedwhenever needed. Then, the cell was allowed to stand aside for12h. Now, the electrolytically added insoluble aluminium ions,which is much more active than chemically added aluminiumions [30] combine readily with the toxic materials present in the effluentsandsettlethemeasilyassludge.Theinsolubilityofalu-miniumions,intheformofaluminiumhydroxideandthenatureof its effective coagulating power facilitate EC. Most of the alu-minium ions are used in the coagulation process and hence, thelevel of aluminium ions are reduced to less than 0.1mg/l after12–24h [25–29].The samples present in both cells were filtered separatelythrough G3 microfibre filter. The filtrates were analysed toestimate the various physico-chemical parameters [32,33]. The above filtrates of the both the samples with and without addedAAC, were again electrocoagulated for a period of contacttime, after cleaning the electrodes. At the end of each run, theelectrodes were cleaned and thoroughly washed with water toremove any solid residue on the surfaces and reweighed. 3. Results and discussion Table1liststhewaterqualityparameters(WQPs)ofdistilleryeffluent before EC treatment. The observed WQPs are found tobe higher than the prescribed limits by Bureau of Indian Stan-dards(BIS)forthedischargeofindustrialeffluents[34,35].This indicatethatthedistilleryeffluentcouldbedischargedonlyafterproper effluent treatment. Hence, in the present study EC tech-nique is employed for the effluent treatment.Aluminium and stainless steel (iron) are chosen as electrodematerials for EC. They are readily available and are very effec-tive in EC [17]. The current density applied is 182A/m 2 . Therate of turbidity removal by the EC technique with and withoutAAC is found to be high, of the order of 99%. This is becausethemicrobubblesandelectrolyticallygeneratedaluminiumionscoagulate with charged particles in the effluent and agglomer-ate it. They are later settled or floated on the surface from whichtheycouldeasilyberemoved.InthecaseofparameterslikeCl − ,SO 42 − , TDS, total hardness, Ca 2+ , BOD and COD, the removalefficiencyvariedbetween18.3%and96.8%fortheECwithandwithout AAC (Table 2). The overall removal efficiency of pol- lutants of distillery effluents by the EC with and without AAC isshown in Fig. 2. Table 2 represents the data of the WQPs noted for EC with and without AAC from 10 to 60min. In presence of AAC, EC is found to be effective than EC without AAC. 3.1. Effect of initial pH  Initial pH is an important operating parameter in EC process.Generally,thepHoftheeffluentischangedduringtheEC[9,17].  T   a    b    l   e    2    C    h   a   r   a   c    t   e   r    i   s    t    i   c   s   o    f    d    i   s    t    i    l    l   e   r   y    i   n    d   u   s    t   r    i   a    l   w   a   s    t   e   w   a    t   e   r    b   e    f   o   r   e   a   n    d   a    f    t   e   r    E    C   w    i    t    h   a   n    d   w    i    t    h   o   u    t    A    A    C    i   n   p   r   e   s   e   n   c   e   o    f    i   r   o   n   a   n    d   a    l   u   m    i   n    i   u   m   e    l   e   c    t   r   o    d   e   s    W    Q    P   s    B   e    f   o   r   e    t   r   e   a    t   m   e   n    t    R   e   m   o   v   a    l   a    f    t   e   r    E    C    t   r   e   a    t   m   e   n    t    W    i    t    h   o   u    t    A    A    C    W    i    t    h    A    A    C    a 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