Biotreatment of industrial effluents CHAPTER 11 – textile effluent

CHAPTER 11 Textile Effluent Textile industries receive and prepare fibers; transform them into yarn, thread, or webbing; convert the yarn into fabric or related products; and dye and finish these materials to the final product Textile manufacturing consumes a considerable amount of water The principal pollutants in the textile effluent are recalcitrant organics, color, toxicants and inhibitory compounds, surfactants, soaps, detergents, chlorinated compounds, and salts Dye is the most difficult constituent of the textile wastewater to treat The type of dye in the effluent could vary daily, or even hourly, depending upon the campaign The various processes in a textile mill that generate effluent are desizing, scouring, bleaching, dyeing, and printing Effluent from the desizing operation produces the most chemical oxygen demand (COD)(40%)and effluent from the final rinsing operation the least (7.5%) The suspended solids load is highest in the effluent generated from desizing (47.7%) and the least from the scouring and bleaching operation (7.3%) The volume of effluent produced is highest from the combined scouring and bleaching operation (53.9%) and the least from the final washing (7.5%)(see Figs 11-1 to 11-3) The typical cotton textile effluent stream will have a pH of 8.9 to 9.9, a biological oxygen demand (BOD)of 90 to 170 mg/L, a COD of 1,018 to 1,062 mg/L, suspended solids of 110 to 180 mg/L, a total kjeldahl Nitrogen (TKN) of 20 to mg/L, a phosphate concentration of 0.9 to 2.4 mg/L, sulfate concentration of 1.9 to 6.4 mg/L, C1- of 557 to 610 mg/L, and a color reading (at 669 nm using UV-visible spectrophotometer) of 0.15 to 0.21 (Sen and Demirer, 2003) Physical Treatment Chemical, physical, and biological methods have been tried for the treatment of textile effluent containing dyes (Robinson et al., 2001 ) The physical treatment methods include(l) adsorption with activated carbon, peat, wood chips, fly ash and coal (mixture), silica gel, and other materials such as natural clay, corn, cobs, rice hulls, etc.; (2)membrane filtration; (3)ion 123 124 Biotreatment of Industrial Effluents FIGURE 11-3 Volume contribution to the final effluent from various operations of a cotton textile mill Textile Effluent 125 exchange; (4)irradiation; and (5)electrokinetic coagulation The chemical methods include oxidative processes using hydrogen peroxide, H202-Fe(II) salts (Fenton's reagent), ozonation, photochemistry, sodium hypochlorite, cucurbituril, and electrochemical destruction Alum treatment is well suited for disperse, vat, and sulfur dyes, while activated carbon treatment is ideal for azoic, reactive, acid, and basic dyes Ozone has been found effective for azoic, reactive, acid, basic vat, and sulfur dyes The biological treatment methods include (1) decolorization by white rot fungi; (2)use of other microbial cultures like mixed bacterial cultures, Pseudomonas strains, Sphingomonas under aerobic, anaerobic, or mixed conditions; and (3) adsorption by living or dead microbial biomass Physical and chemical methods are expensive and are very effective only if the effluent volume is small Biodegradation It is generally difficult to degrade wastewater from the textile industry by conventional biological treatment processes because the BOD/COD ratio is less than 0.3 Decolorization of dyes by bacteria can be brought about by either adsorption to microbial cells or biodegradation Since dyes of different types are generally used in a textile industry, the microorganisms should be nonspecific and secrete extracellular enzymes The worldwide annual production of wool is about 1.6 million tonnes (clean weight, 2001 figures) The scouring (contaminant extraction)or washing of this wool removes an approximately equal weight of wool wax and u s e s a b o u t 10 m of water per tonne of raw wool The wastewater consists of a stable emulsion of wool wax ( ~75%) in an aqueous solution containing dissolved organic and inorganic compounds with very high COD (-~45,000 mg/L) A chemical flocculation process known as Sirolan CF removes over 95 % of wool wax The sludge produced from the process is used in composting The effluent left from this process contains the watersoluble organic and inorganic compounds washed from the raw wool, known as "suint," which is a highly colored mixture of mainly potassium salts of fatty acids, as well as peptides with a COD of 5,000 to 15,000 mg/L The effluent contains nonionic surfactants like nonylphenol polyethoxylates, which are used in the scouring process The treatment of this effluent for to days with anaerobic bacteria resulted in partial grease flocculation; the efficiency of this process varied widely (from 30 to 80%), depending on the concentration of free surfactant, rather than total surfactant, in the effluent Anaerobic microbes (taken from the sludge of a municipal wastewater treatment plant) could partially degrade this ethoxylate within days by shortening the hydrophilic chain, causing coagulation and subsequent flocculation of wool grease from the liquor (Charlesa et al., 1996) Wastewaters resulting from printing matrix washing and dyestuff leakage from the silk and Lycra printing industry contain a high concentration 126 Biotreatmentof Industrial Effluents of ammonia nitrogen (urea, ammonium sulfate, and tartrate used for the dyestuff preparation)together with organic compounds The effluent quality was improved by a single-sludge treatment process with an externally added carbon source in the form of a mixture of methyl and ethyl alcohols from pharmaceutical industry wastes This treated effluent when subsequently filtered and sterilized using UV radiation was found to be suitable for reuse for washing purposes, achieving a 30 to 40% reduction in water usage The treated water did not accumulate any recalcitrant or toxic compounds When the water was treated prior to filtration with a dose of 20 mg/L of ozone, the residual color and nonionic surfactants were degraded, allowing the water to be used for preparing dyes (Sterna et al., 1996) Aeromonas hydrophila could decolorize 24 azo, anthraquinone, and indigo textile dyes containing various substituents such as nitro and sulfonic groups with days of incubation (Chen et al., 2003) The decolorization efficiency was enhanced by the addition of an extra nitrogen source such as yeast extract or peptone Glucose inhibited the decolorization activity, probably because the acids formed during glucose conversion decreased the pH of the culture medium, thus inhibiting cell growth and decolorization activity The presence of oxygen inhibited the bacterial degradation of azo dyes, because the oxygen was probably competing with the azo group as the electron receptor in the oxidation of the reduced electron carrier When solid textile mill sludge mixed with cow dung was vermicomposted (with Eisenia foetida)(30% on dry weight basis) for 90 days, there was a significant reduction in the C:N ratio and an increase in TKN Dehydrogenase activity increased up to 75 days and decreased on further incubation (Kaushik and Garg, 2003) Biosorption The uptake and subsequent accumulation of chemicals and toxins by biomass is termed "biosorption." Dead bacteria, yeast, and fungi have been found to biosorb dyes from textile effluents and decolorize them (Robinson et al., 2001) The interaction involves adsorption, deposition, and ionexchange For living cells, however, the major mechanism for mineralizing dyes is biodegradation through the lignin-modifying enzymes they produce, such as laccase, manganese peroxidase, and lignin peroxidase Biosorption can be used when the dye is very toxic to the growth of the microorganism It had been observed that the biomass derived from the thermotolerant ethanol-producing yeast strain Kluyveromyces marxianus IMB3 had a relatively high affinity for heavy metals and biosorbed dyes from textile effluents Actinomyces have been used as an adsorbent for decolorization of effluents containing anthroquinone, phalocyanine, and azo dyes Biosorption is generally q u i c k - - a few minutes in algae to a few hours in bacteria Aspergillus niger can decolorize acidic and basic blue dyes by biosorption in 30 to 48 h Textile Effluent 127 Dead fungal cells such as Botrytis cinerea, Cryptococcuss, Candida rugosa, and Endothiella aggregata have been able to decolorize several reactive dyes through an adsorption process (Fu and Viraraghavan, 2001) Autoclaved Phanerochaete chrysosporium could decolorize a solution containing Congo Red better than living cells (90 and 70%, respectively) Several authors have found a similar pattern in the performance of dead and live cells, and it was concluded that because of the rupture of dead cells there was an increase in the surface area for adsorption Degradation using living cells has several limitations and disadvantages Living cells require a nutrient if the influent lacks it, and their performance depends on the appropriate operating conditions Waste products from fermentation could be a source for dead biomass Fungal biomass can be regenerated using organic solvents like methanol and ethanol and nonionic surfactants such as Tween and alkali solutions It was suggested that alcohols such as methanol modified the hydrophilic-hydrophobic interaction between the dye molecule and the biomass Pretreatment of the biomass increased its adsorption capacity There are two basic methods: (1) autoclaving or (2) washing with solvents such as formaldehyde or with inorganic chemicals such as sulfuric acid, sodium hydroxide, and sodium bicarbonate Autoclaving increased the biosorption of Basic Blue dye by a factor of 15, probably by disrupting the fungal structure and exposing the binding sites for the dye Sulfuric acid treatment doubled the adsorption capacity by changing the negatively charged surface of the biomass to a positively charged one, thereby increasing the attraction between the fungus and the dye The factors that affected the growth of the fungi were: characteristics of the medium (pure nutrient medium), type of carbon source (glucose, starch, maltose, and cellobiose were good carbon sources), type of nitrogen source, nutrient concentration, pH (between to 5) and temperature of the medium (20 to 35~ incubation time (1 to days}, and concentration of oxygen in the medium (Zhang et al., 1999) The factors that pertain to the wastewater are: ~ Structure of the dye Metal ions Metal ions could neutralize the surface charges and thus reduce the repulsive forces, bringing them closer and making the biosorption process more favorable Surfactants The presence of detergent in the wastewater could reduce the binding efficiency of the cells Temperature Lower temperatures favored biosorption if the process is physical absorption ~ pH Affected the solubility of some dyes as well as the biosorption capacity Ionic strength So far no clear conclusions can be drawn about how the structure of the dye affects its degradation Spadaro et al (1992) reported hydroxyl-, amino-, 128 Biotreatment of Industrial Effluents acetamido-, or nitro-substituted aromatic dyes degraded faster than unsubstituted ones, whereas a few authors have not seen any difference in the degradation of substituted and unsubstituted sulfonated dyes Combined Treatments Because of large variability of the composition of textile wastewaters, most of the traditional methods for treatment are inadequate Hence current research is focused on a combination of physical, chemical, and biological methods for treating this effluent in a cost-effective way The principal enzymes, lignin peroxidase and manganese peroxidase, present in the white rot fungus Phanerochaete chrysosporium can oxidize substrates by an electron transfer process or by radicals generated during the enzyme catalytic cycle Other white rot fungi capable of decolorizing dyes include Trametes versicolor, Coriolus versicolor, and Funalia trogii A combined biotreatment with Phanerochaete chrysosporium fungus followed by ozonization could lead to better degradation Ozone attacks nucleophilic centers like carbon-carbon or nitrogen-nitrogen double or triple bonds or acts through hydrogen abstraction, electron transfer, or radical addition, which degrade recalcitrant compounds like dye much more quickly Kunz et al (2001) observed that enzyme treatment led to a 30 to 40% decolorization, and the subsequent ozone treatment led to 55 % phenol degradation and 40% color reduction Chloride ion present in the effluent slows down the activity of the enzyme because it competitively binds to the active site, preventing the binding of hydrogen peroxide and thereby inhibiting the electron transfer in the first step of the cycle A typical dye house effluent containing an anthraquinone dye, an anionic detergent, a softening agent, and NaC1 was treated aerobically using an activated sludge process followed by UV radiation; this treatment decreased the inhibition of microbial growth from 47 to 30% The addition of mL H 2 to L of UV-irradiated sample decreased the inhibitory effect further to 26 % A combination of aerobic treatment and the addition of an adsorbenttype flocculent such as powdered activated carbon, bentonite, activated clay, or commercial synthetic inorganic clay has been found to degrade color more effectively The addition of activated carbon into the aeration tank increased the removal efficiency to 90% (Marquez and Costa, 1996) Pala and Tokat (2002) observed a 94% COD reduction and an 80% color removal efficiency when an organic flocculant was added to the activated sludge used to treat a textile dye effluent The color removal efficiency was only 35 % when the adsorbent was not added Although activated carbon removed dyes effectively from a waste stream, they were present in a more concentrated and toxic form in the liquid, and their safe disposal increased the treatment cost The regeneration of activated carbon also added to the operating cost Addition of low cost adsorbents such as peat, wood, silica, and fly ash during Textile Effluent 129 the activated sludge process was found to be very effective in color removal (Ramakrishnan and Viraraghavan, 1997) Removal of textile reactive dyes by renewable biosorbents like apple pomace and wheat straw have shown promising results (Robinson et al., 2002) A continuous process of combined chemical coagulation using poly aluminum chloride (PAC) and a polymer, followed by electrochemical oxidation and finally aerobic activated sludge treatment for h was able to reduce the COD of the textile effluent by 85 % The treatment cost of this combined process was estimated to be about $ 0.34 per ton of wastewater treated (Lin and Peng, 1996) The current cost figure of the conventional treatment process was about $0.45 per ton of wastewater Reactors A baffled anaerobic reactor was used to degrade a cotton textile mill effluent using sucrose, peptone, and nutrient as cosubstrates When a hydraulic retention time of 20 h was used, 70% COD (influent = 1000 mg/L) and 90% color removal rates were achieved A two-stage upflow anaerobic sludge blanket (UASB) reactor operated with tapioca as the cosubstrate (1,500 mg/L) achieved a 70% color removal and an almost 90% COD reduction When only one UASB reactor was used without any cosubstrate, a 60% COD reduction and 80% color removal were achieved Anaerobic treatment of textile wastewater and decolorization using a fluidized bed reactor with an external carbon source in the form of glucose led to an 82, 94, and 59% COD, BOD, and color removal, respectively, at a hydraulic retention time (HRT)of 24 h (Sen and Demirer, 2003) Pumice was used as the support material for the growth of the microorganisms Various types of reactors (including a sequencing batch reactor, UASB, anaerobic filter, batch, and fluidized bed) have been used to treat effluents containing synthetic phthalocyanine, diazo, azo, reactive, anthraquinone, and basic dyes under anaerobic conditions (Sen and Demirer, 2003) Synthetic wastewater from the desizing and dyeing sections of a textile mill was treated in an anaerobic/aerobic sequential batch reactor (SBR) with a hydraulic retention time of 2.6 days (Shaw et al., 2002) The desizing section effluent contained starch, polyvinyl alcohol (PVOH), and carboxymethyl cellulose (CMC), and the dyeing section effluent contained alkali, sodium salts, and an azo dye (Remazol Black) The reactor cycle (~5 h and 50 min) consisted of fill, anaerobic reaction, aerobic reaction, settle, decant, and idle (Fig 11-4) Color and dye reduction was greater than 90%, and partial degradation of PVOH was observed Decolorization improved with aeration despite the reduction in total organic carbon (TOC) removal, indicating that the decolorization process was independent of the methanogenic activity as long as the redox potential remained low It has been reported that PVOH is more easily degraded under aerobic conditions 130 Biotreatment of Industrial Effluents Part decant Idle Fill Anaerobic reaction 9% 4% 5% a o/,, ~ Aerobic reaction 69% Settle FIGURE 11-4 Various operational cycles (time) in a typical anaerobic-aerobic sequential batch reactor (SBR) Yu et al (1996) achieved a 92% degradation of a 75,000 MW PVOH in two reactors one was an anaerobic SBR, the other was aerobic A simulated cotton mill effluent was treated using a UASB and an aerobic reactor placed in series; the COD, BOD, and color removal efficiencies achieved were 88, 99, and 77%, respectively Most of the color removal took place in the UASB (O'Neill et al., 2000) Effluent from the Sirolan CF process was aerobically treated using a laboratory-agitated fermenter and 100- and 3000-L pilot-scale airlift fermenters with external recycle for 24-, 45-, and 94-h retention times, respectively, to achieve 65, 55, and 95% COD, TOC, and BOD removal efficiencies, respectively (Poole et al., 1999) The biomass used to treat this effluent was identified as from the genus Epistylis A combination of the Sirolan CF process followed by aerobic degradation could remove 90% of the COD, much more than any other process, but this process requires high capital and operating expenditures Textile effluent was processed in a pressurized bioreactor (~3 bar of pressure) coupled with an ultrafiltration membrane unit for sludge retention The treated effluent was then processed in a nanofiltration unit and was good enough to be reused in the plant The bioreactor was operated at very high biomass concentration, but the excess sludge production was very small (Krautha, 1996) A pilot-scale dynamic up-flow sand filter was used as a biofilm reactor for decolorization and denitrification as well as for filtration of suspended solids from a pretreated textile effluent Biomass growth and the sloughing of biological film did not prevent the removal of high concentrations of influent suspended solids At low nitrate-loading rates, the filter followed the ideal plug-flow hydrodynamics In the lower part of the filter, Textile E f f l u e n t pH adjustment Biological process Filter "1 I J~L~ I "1 I 131 Primary treatment Adsorbent NaOCI Ozonization UV Electro chemical treatment Aerobic or Anaerobic or Aerobic/Anaerobic Oxidation (H202) FIGURE 11-5 A typical flow sheet for treatment of textile dye effluent denitrification removal rates followed zero-order kinetics, while in the upper part of the filter, denitrification followed half-order kinetics (Canziania and Bonomoa, 1998) Conclusions Textile industries produce considerable amounts of effluent characterized by large amounts of suspended solids, high COD, fluctuating pH, high temperature, and a mixture of dyes A combination of biochemical, chemical, and physical processes appears to be promising in degrading such an effluent as shown in Fig 11-5 The presence of dyes in the effluent poses the biggest problem since they are recalcitrant and toxic Both aerobic and anaerobic processes have been successfully used for degrading the dyes, but the best appears to be a combination of both Adsorption of dyes by dead cells appears to be a better alternative than treatment with live cells Biological activity in liquid state fermentation is slow and hence is inefficient on a continuous basis Solid-state fermentation appears to be a good alternative for handling an enriched biomass Chapter 10, Degradation of Dyes, deals exclusively with the decolorization of dyes References Canziania, R., and L Bonomoa 1998 Biological denitrification of a textile effluent in a dynamic sand filter Water Sci Technol 38(1):123-132 Charlesa, W., H Goena, and R Cord-Ruwischa 1996 Anaerobic bioflocculation of wool scouring effluent: the influence of non-ionic surfactant on efficiency Water Sci Technol 34(11):1-8 Chen, K C., J.-Y Wua, D.-J Liou, and S.-C J Hwang 2003 Decolorization of the textile dyes by newly isolated bacterial strains J Biotechnol 101:57-68 132 B i o t r e a t m e n t of I n d u s t r i a l Effluents Fu, Y., and T Viraraghavan 2001 Fungal decolorization of dye waste waters: a review Bioresource Technol 79:251-262 Kaushik, P., and V K Garg 2003 Vermicomposting of mixed solid textile mill sludge and cow dung with the epigeic earthworm Eisenia foetida Bioresour Technol 90:311-316 Krautha, K 1996 Sustainable sewage treatment plants application of nanofiltration and ultrafiltration to a pressurized bioreactor Water Sci Technol 34(34):389-394 Kunz, A., V Reginatto, and N Duran 2001 Combined treatment of textile effluent using the sequence Phanerochaete chrysosporium Chemosphere 44:281-287 Lin, S H., and C F Peng 1996 Continuous treatment of textile wastewater by combined coagulation, electrochemical oxidation and activated sludge Water Res 30(3):587-592 Marquez, M C., and C Costa 1996 Biomass concentration in PACT process Water Res 30(9):2079-2085 O'Neill, C O., F R Hawkes, D L Hawkes, S Esteves, and S J Wilcox 2000 Anaerobicaerobic biotreatment of simulated textile effluent containing varied ratios of starch and azo dye Water Res 34(8):2355-2361 Pala, A and E Tokat 2002 Color removal from cotton textile industry wastewater in an activated sludge system with various additives Water Res 36:2920-2925 Poole, A J., R Cord-Ruwisch, and F W Jones 1999 Biological treatment of chemically flocculated agro-industrial waste from the wool scouring industry by an aerobic process without sludge recycle Water Res 33(9):1981-1988 Ramakrishnan, K R., and T Viraraghavan 1997 Dye removal using low cost adsorbents, Water Sci Technol 26(2-3):189-196 Robinson, T., B Chandran, and P Nigam 2002 Removal of dyes from a synthetic textile dye effluent by biosorption on apple pomace and wheat straw Water Res 36:2824-2830 Robinson, T., G McMullan, R Marchant, and P Nigam 2001 Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative, Bioresour Technol 77:247-255 Sen, S., and G N Demirer 2003 Anaerobic treatment of real textile wastewater with a fluidized bed reactor, Water Res 37:1868-1878 Shaw, C B., C M Carliell, and A D Wheatley 2002 Anaerobic/aerobic treatment of coloured textile effluents using sequencing batch reactors Water Res 36:1993-2001 Spadaro, J T., M H Gold, and V Renganathan 1992 Degradation of azo dyes by the lignin degrading fungus Phanerochaete chrysosporium Appl Environ Microbiol 58(8):2397-2401 Sterna, S R., L Szpyrkowiczb, and F Zilio-Grandib 1996 Treatment of silk and lycra printing wastewaters with the objective of water reuse Water Sci Technol 33(8):95-104 Yu, H., G Gu, and L Song 1996 Degradation of polyvinyl alcohol in sequencing batch reactors Environ Technol 17:1261-1267 Zhang, F., J S Knapp, and K N Tapley 1999 Decolorization of cotton bleaching effluents with wood rotting fungus Water Res 33(4):919-928 Bibliography Ledakowicz, S., M Solecka, and R Zylla 2001 Biodegradation, decolourisation and detoxification of textile wastewater enhanced by advanced oxidation processes J Biotechnol 89:175-184 Marmagne, O., and C Costa 1996 Color removal from textile plant effluents Am Dyest Rept 85(4):15-21  ...124 Biotreatment of Industrial Effluents FIGURE 11- 3 Volume contribution to the final effluent from various operations of a cotton textile mill Textile Effluent 125 exchange;... concentration 126 Biotreatmentof Industrial Effluents of ammonia nitrogen (urea, ammonium sulfate, and tartrate used for the dyestuff preparation)together with organic compounds The effluent quality... high affinity for heavy metals and biosorbed dyes from textile effluents Actinomyces have been used as an adsorbent for decolorization of effluents containing anthroquinone, phalocyanine, and