Bio-physcio-chemical Treatment of Paper Mill Effluents

8/9/2019 Bio-physcio-chemical Treatment of Paper Mill Effluents

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Journal of Scientific & Industrial ResearchVol. 64, January 2005, pp 61-64

Bio-physico-chemical treatment for removal of colour from pulp andpaper mill effluents

V Saravanan and T R Sreekrishnan*Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi 110 016

Received 17 May 2004; accepted 20 October 2004

Combination of biological and physico-chemical treatment method is adopted for colour removal of paper milleffluents. On treatment of effluent with Trichoderma sp in batch studies, 72 % colour reduction was achieved within 24 h. Incontinuous mode, treating effluent with the same fungus in a fluidized bed reactor, around 27 % colour reduction wasachieved. This biologically treated effluent is further treated with a poly-electrolyte (potash alum) to improve the colour

reduction. Maximum colour reduction of 81 % was obtained by this combined treatment.Keywords : Colour removal, Pulp and paper mill effluent, Biological treatment, Physico-chemical treatmentIPC Code: C 02 F 3/00, C 02 F 1/00

IntroductionPulp and paper mill effluents are highly coloured

mainly due to lignin and its derivatives 1-3, whichimpart an offensive colour to the water. Such colour isnot only aesthetically unacceptable, but also inhibitsthe natural process of photosynthesis in the streamdue to absorbance of sunlight 4. This leads to a chainof adverse effects on the aquatic eco-system as the

growth of the primary consumers as well as secondaryand tertiary consumers is adversely affected. Thus, itis important to have an eco-friendly treatment methodto treat the effluent.

Several physical and chemical processes for colourremoval extensively studied include combination ofultrafiltration and reverse osmosis techniques, ion-exchange, chromatography, lime precipitation, andmodified bleaching sequences such as peroxideaddition during extraction, replacement of chlorine byhypochlorite, sorption on hypo and alum sludge,activated carbon, and allophonic compounds 5-9.

However, these processes are expensive and none isconsidered to be economically viable when this isdone as standalone process 10. Biological methodshave been found to be more effective and eco-friendlysince they are capable of degrading not only lignin butalso chloro-organics contributing to AOX. Among thebiological methods, wood degrading white-rot fungi

has been found to treat the effluent effectively 11.Phanerochaete chrysosporium and Trametesversicolor strains possess good decolourizationcapacity 12-14 . A zygomycete, Rhizopus orzae , was alsofound to decolourize the bleach plant effluent 15. Someof the bacteria like, Pseudomonas putida, Citrobactersp and Enterobacter sp were used in an activatedsludge process for decolourization 16. The problem

with above strains is to maintain sterilized conditionof the effluent. In this study, Trichoderma sp wasused in effluent tretment for colour removal. Thiseffluent was further treated with alum.

Materials and MethodsEffluents

Samples of black liquor, bleach effluent and finaleffluent (combined effluent coming out of the plant)were obtained from an agro-residue based paper millsituated near New Delhi. All samples were collectedin plastic cans and stored at 4 ˚C.

Inoculum Used in Aerobic TreatmentTrichoderma sp was isolated in the laboratory 17, 18 .

It was found to grow in undiluted and unsterilizedeffluent, and was grown in pellet form in a mediumcontaining glucose (1 %) as the carbon source(Table 1). The culture was maintained in PDB (PotatoDextrose Broth) agar slants. Concentration of glucoseand nutrients was varied according to theexperimental requirements, but the same relativeconcentration values were maintained for all themedia components.

____________*Author for correspondenceTel: +91-11-26591014; Fax: +91-11-26582282E-mail: [email protected]; [email protected]


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Experimental Set-up of Fluidized Bed Reactor

Fungus grown in pellet forms was fluidized insidethe reactor containing effluent using compressed air.Reactor was started in batch mode (Fig. 1), and afterattaining steady state, it was switched to continuousmode. The outlet was collected from the overflow ofthe reactor.

Analytical MethodsChemical oxygen demand (COD) and solid were

analyzed as per the Standard Methods 19. Colour was

estimated according to standard given by CanadianPulp and Paper Association. Absorbance values wereconverted to Platinum Cobalt Units (PCU) as follows:

PCU = 500 x A 1 /A2 ,

Where A1 = Absorbance of sample, A2 = Absorbanceof 500 units of Platinum Cobalt standard ( A465 =0.132).

Results and DiscussionCharacterization of Effluents

The effluents collected from different sections ofthe paper industry were characterized. Estimation ofparameters (Table 2) enabled to get a completepicture of the nature of effluents being handled andthe type and extent of objectionable compoundspresent in them.

Colour Removal Study of Final Effluent with Trichoderma spThe final effluent was treated to get maximum

colour reduction, using combination of physico-chemical and biological treatment methods. Batchstudies were conducted to study the colour removalpattern by the isolated fungus. The Trichoderma sp

was grown in glucose (2%) medium. The pellets werecentrifuged and a definite mass of pellets wastransferred to several conical flasks containing 100 mlof final effluent. The system pH was adjusted to 5.5.The flasks were kept in a shaker at 150 rpm and at30 ° C. At a regular time intervals, one flask wasremoved.

Maximum colour reduction (72-73 %) wasobserved within 24 h (Table 3), after which the finaleffluent colour started increasing. This phenomenonwas observed repeatedly. The system pH also

Fig. 1 Fluidized bed reactor

Table 1 1 % glucose medium composition

Component (g/l)

Glucose 10.000

Yeast extract 0.340

NH4Cl 0.840

KH2PO 4 0.134

K2HPO 4 0.234

MgCl 2.6H2O 0.084

Table 2 Characterization of effluents

Parameters* Black liquor Bleach effluent Final effluent

pH 10.25 8.03 9.86COD 38014 2426 8323

Colour (CPU) 53220 2864 11600TKN 1052 918 830TS 46305 1925 10535

TDS 43990 1826 9585TSS 2315 99 950TFS 29885 1500 8955TVS 16420 425 1580DFS 29620 1410 8735DVS 14370 416 850

* All parameters in mg/l unless otherwise stated

TKN = Total Kjeldal Nitrogen; TS = Total solids; TDS = Totaldissolved solids; TSS = Total suspended solids; TFS = Totalfixed solids; TVS = Total volatile solids; DFS = Dissolved fixedsolids; DVS = Dissolved volatile solids

Table 3 Colour removal and growth pattern of theTrichoderma sp with high biomass concentration grown in PDB

Timeh

ColourPCU

Colourreduction

%

Dry cell massg

0 7591 - 0.46114 5091 32.9 0.4736 4545 40.1 0.5369

10 4030 46.9 0.465616 3106 59.2 0.514424 2068 72.8 0.5121


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10 Mehna A, Bajpai P & Bajpai P K, Studies on decolorization ofeffluent from a small pulp mill utilizing agro-residues withTrametes versicolor , Enzym Microb Technol , 17 (1995) 18-22.

11 Bajpai P & Bajpai P K, Reduction of organochlorine

compounds in bleach plant effluents, Adv Biochem Eng Biotechnol , 57 (1997) 213-259.12 Eaton D C, Chang H M, Joyce T W, Jeffries T W & Kirk T

K, Method obtains fungal reduction of the colour kraft bleachplant effluents, Tappi, 65 (1982) 89-92.

13 Bajpai P, Mehna A & Bajpai P K, Decolorization of kraftbleach effluent with white rot fungus Tremetes versicolor,Process Biochem , 46 (1993) 274-276.

14 Pallerla S & Chambers R P, Characterization of a Ca-alginate-immobilized Trametes versicolor bioreactor fordecolorization and AOX reduction of paper mill effluents,

Biores Technol , 60 (1997) 1-8.15 Nagarathnamma R, Bajpai P & Bajpai P K, Studies on

decolourisation, degradation and detoxification ofchlorinated lignin compounds in kraft bleaching effluents byCeriporiopsis subvermispora, Process Biochem , 34 (1999)939-948.

16 Chandra R, Microbial decolorization of pulp and paper milleffluent in presence of nitrogen and phosphorus by activatedsludge process, J Environ Biol , 22 (2001) 23-27.

17 Ali M & Sreekrishnan T R, Anaerobic treatment ofagricultural residue based pulp and paper mill effluents forAOX and COD removal, Process Biochem , 36 (2000) 25-29.

18 Ali M, Treatment of agro-residue based pulp and paper milleffluent, Ph D Thesis, Indian Institute of Technology, Delhi,2000.

19 Clesceri L S, Greenberg A E & Trussel R R, Standardmethods for the examination of water and wastewater (American Public Health Association, Washington DC)1992, pp 550-557.

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Bio-physcio-chemical Treatment of Paper Mill Effluents