CHROMIUM REMOVAL FROM TANNERY WASTEWATER USING CHEMICAL AND BIOLOGICAL TECHNIQUES AIMING ZERO DISCHARGE OF POLLUTION

Hesham Abdulla

Publication Name: science.zu.edu.eg

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PROCEEDING OF FIFTH SCIENTIFIC ENVIRONMENTAL CONFERENCE, 2010, ZAGAZIG UNI., 171 - 183

CHROMIUM REMOVAL FROM TANNERY WASTEWATER USINGCHEMICAL AND BIOLOGICAL TECHNIQUES AIMING ZERODISCHARGE OF POLLUTION

Hesham M. Abdulla

, Engy M. Kamal

, Amr H. Mohamed

,Ahmed D. El-Bassuony

Botany Department, Faculty of Science, Suez Canal University, Ismailia

Housing And Building National Research Center (HBNRC), Cairo*Author for correspondence (E-mail:nona74@hotmail.com)

ABSTRACT

Tannery effluent containing chromium is one of the most obvious problems in leatherindustry.

In Egypt,

the tannery wastewater is discharged directly to the main domestic sewagepipeline which adds difficulties to the sewer system and to the wastewater treatment plants.Chromium has been used widely in tanning for the excellent properties that it renders to theleather along with simplicity of operation. However, only 60% of the total chromium saltreacts with the hides. In the other word, about 40% of the chromium amount remains in thesolid and liquid wastes. Therefore, the removal and reuse of the chromium content of thesewastewaters is necessary for environmental protection and economic reasons. In this study,the recovery of chromium (III) was carried out by using precipitation process. To thispurpose, two common precipitating agents lime and cement dust were used. The effects of precipitating agent concentration, settling rate and supernatant volume were studied in batchexperiments. Results showed that the

characteristics of tannery wastewater samples collectedfrom the chromium tanning stage showed COD (4538 mg/l), Cr(III) (2350 mg/l) and Cr(VI)(900 mg/l). The maximum chromium (III) recovery (98%) was achieved using 2g/100ml of lime and 2hr settling rate. For biological removal of Cr(VI), thirty four actinomycete isolateswere found to tolerate up to 100 mg/l Cr(VI), five of these isolates could tolerate Cr(VI) atconcentration up to 2500 mg/l. The supernatant was further analyzed for bioremoval of soluble chromium (VI) using chromium resistant actinomycetes. The results showed thatisolate S65 is the most efficient isolate where nearly 97% of chromium (VI) was removedover 4hrs period. This paper surveys the development of technologies that have rendered thetanning process eco-sustainable, where the combination between the chemical precipitationand the biological removal of chromium from tanning wastewater make it meet theenvironment safely.

Keywords:

Actinomycetes, Cr(VI) bioremoval, Cr(III) precipitation, Tannery wastewater

INTRODUCTION

The tanning industry forms the backbone of the Egyptian leather industry. The totalnumbers of tanneries in Egypt are more than 300, of which more than 85% adopt thechromium tanning process (Ibrahim. and Shalaby, 1991) because of its processing speed, lowcosts, and light color of leather and greater stability of the resulting leather. Tannery effluentcontaining chromium is one of the most recognized problems in leather industry. Tanningprocess using chromium compounds is the most common methods for processing of hides(Sreeram, and Ramasami, 2003). In this process about 60% - 70% of chromium reacts withthe hides. In other words, about 30%- 40% of the chromium amount remains in the solid andliquid wastes (especially spent tanning solutions). The wastewater of tanning process isusually discharged, without proper treatment, into the sewerage system causing seriousenvironmental impact. In nature, chromium occurs in two major states {Cr(VI) and Cr(III)}.Even when the tanning wastewater has chromium only in trivalent form, since the tanning

CHROMIUM REMOVAL FROM TANNERY WASTEWATER

172process does not generate chromium (VI), some countries fixed regulatory limits for the twospecies. This criterion appears from the assumption that the oxidation would be producedduring storage and sometimes through the tanning process. Although chromium(III) oxidationto chromium(VI) occurs under specific environmental conditions (Bartlett and James, 1979;Eary and Rai, 1987), special attention is devoted to this transformation because chromium(VI)causes adverse effects for the human health (Committee on Biologic Effects of AtmosphericPollutants, 1974) where Cr(VI) induced acute and chronic toxicity, neurotoxicity,dermatotoxicity, genotoxicity, carcinogenicity, immunotoxicity, and general environmentaltoxicity (Bagchi

et al

., 2002) and has been shown to be mutagenic in a number of bacterialsystems (Nishioka, 1975; Petrilli and DeFlora, 1977). Although Cr(III) has relatively lowtoxicity (Anderson and Kozlovsky, 1985; Palmer and Wittbrodt, 1991), when soluble Cr(III)is added to soil, manganese oxides present in the soil may cause oxidation to Cr(VI) (Bartlettand James, 1979). When not oxidized to Cr(VI) form, Cr(III) may remain immobilized in thesoil.Due to the harmful effect of chromium on human and living organisms, in addition tothe cost of the chromium metal it is suggested to be recovered from the tanning wastewater(Fabiani

et al

., 1997; Kocaoba, and Akin, 2002).There are several methods have been used forremoving of chromium from the tanning wastewater as Cr(III). These methods are chemicalprecipitation, reverse osmosis membrane processes, and adsorption (Patterson, 1985; Ludvik,2000). Of these, chemical precipitation is the common way for this purpose. Substances usedhabitually to promote the precipitation are: calcium hydroxide, sodium hydroxide, magnesiumoxide or calcium magnesium carbonate. Many factors affect the process of chemicalprecipitation including the type of precipitation agent, pH, velocity of precipitation, sludgevolume, time of mixing and complexing agents (Tsugita, and Ellis, 1981; Kocaoba, and Akin,2002).On the other hand, advanced treatment techniques, such as reverse osmosis, ionexchange, membrane filtration, and electro dialysis are effective for removing Cr(VI), butthey are expensive and generate concentrated wastes that require subsequent treatment anddisposal (Komori

et al

., 1990). Biological removal may provide a suitable means for Cr(VI)treatment from wastewater (Lovley and Coates, 1997; Rittmann et al., 2004). Various fungaland bacterial species were reported for chromium bioremoval. However, there is nosystematic study on chromate tolerance, toxicity/resistance or reduction by mycelium formingactinomycetes except few sporadic reports (Basu and Paul, 1999). Although actinomycetesconstitute a significant component of the microbial population in most environments, theirmetabolic diversity and genomic characteristics indicate them as well suited agents forbioremoval of metal and organic compounds (Polti

et al

., 2007). Recent studies showedchromium bioremoval by

Streptomyces rimosus

generated from the antibiotic industry(Sahmoune and Louhab, 2008) and biological reduction of chromate by

Streptomyces griseus

(Poopal and Laxman, 2009).

This study aims to study the characteristics of Egyptian tannerywastewater, to design a laboratory scale system to remove chromium(III) from tannerywastewater by chemical precipitation method using low cost chemicals and some by productsof other industries and to study the efficiency of chromium resistant actinomycete isolates forthe bioremoval of hexavalent chromium from pretreated tanning wastewater.

MATERIALS AND METHODS

1 - Wastewater samples were collected from selected tanneries in old Cairo after thechromium tanning stage

in a as a grap from. Wastewater samples analyses were carried

out according to ‘Standard

Methods for the Examination of Water and

Wastewater’

(APHA, 1998). The following measurements were carried out:

Hesham M. Abdulla, Engy M. Kamal, Amr H. Mohamed,Ahmed D. El-Bassuony

173

a) Chromium concentration:

It was determined calorimetrically (

540

) with aspectrophotometer

using the diphenylcarbazide detection method according to (Bartlett andJames, 1991). Diphenyl carbazide solution was prepared (0.25% w/v in 50% acetone). 15 mleach of the sample solutions, containing various concentrations of Cr(VI) were pipette outinto 25ml standard flasks. To this 2ml of 3M H

was added followed by l ml of diphenylcarbazide and the total volume was made up to 25 ml using distilled water such that the finalconcentrations were in the range of 10 to 100 mg. The intensity of the colour complex formedwas measured using spectrophotometer (CECIL, CE 393, Series 2). The absorbance wasmeasured against a reagent blank at 540-nm wavelength.

Enumeration of actinomycetes, bacteria and fungi from the leather tanningwastewater:

One ml wastewater samples were serially diluted in phosphate buffer and 0.1ml of thesuitable dilutions were plated onto duplicates of the appropriate media using spread platetechnique. Dilutions up to 10

-3

and 10

-4

were used for enumeration of actinomycetes on starchcasein agar amended with cyclohexamide (0.05 g/l), to inhibit fungal growth. Plates wereincubated at 28°C for 10-14 days. Bacteria were enumerated using nutrient agar; plating wasperformed from dilutions 10

-3

and 10

-4

and plates were incubated at 37°C for 24-36 hours.Fungi were enumerated using

Czapek-Dox agar; plating was performed from dilutions 10

-3

and 10

-4

and plates were incubated at 28°C for 4 days.

2. Chemical precipitation (Jar test procedure)

Thirteen glass jars of 250ml volume were filled with 100ml tannery wastewater. Limeand cement dust were added with different concentrations from 0.5g to 3g per 100ml. Thestirring continued for 4 minutes with rapid mixing of 100 rpm, followed by slow mixing for 5minutes at 40 rpm. Jars were allowed to settle for 30 minutes extended before taking the firstsamples from the supernatant for analysis then the rest of samples were taken at intervals of 30 min for 3 hrs.

Screening of actinomycete isolates for chromium (VI) resistance

Actinomycetes were isolated from different habitats characterized by high levels of heavy metals (e.g. industrial wastewater). Hundred and fifty different isolates were recovered,purified and stored as spore suspension in 20% glycerol at -20

C. These isolates wereinoculated into plates of TSA medium composed of (15.0g) tryptone, (5.0g) soy-peptone,(5.0g) NaCl, (15.0g) agar and (1000ml) distilled water, in addition to Cr(VI) as K

atdifferent concentrations ranged from (100-3000mg/l). Plates were incubated for 7days at28°C. Results were recorded as changes in the color of colonies and formation of haloes, thetransparency of a halo were classified into categories according to intensity.

4. Biological removal of Cr (VI) and COD reduction from pretreated tanningwastewater using actinomycetes in batch culture

The chromate resistant actinomycetes inoculated in flasks containing pretreatedtannery effluent.

The inoculua of the tested strains were prepared by harvesting an overnightculture, grown in peptone water broth by centrifugation (6000g for 5min) and resuspended thepellets in sterile phosphate buffer. The actual cell density was counted as cfu/ml, 3 days afterinoculating appropriate dilutions onto starch casein agar plates. Flasks contain pretreatedtannery effluent were inoculated with the chromate resistant actinomycetes isolates in a celldensity (18 x 10

cfu/ml). The culture were incubated at 28ºC with shaking at 100rpm.

CHROMIUM REMOVAL FROM TANNERY WASTEWATER

174Chromate removal by the actinomycetes strains was monitored at different time intervals byestimating the residual Cr(VI) in the culture supernatant fluid by diphenylcarbazide detectionmethod and COD values were also determined.

RESULTS AND DISCUSSION1. Chemical, physical and biological characterization of tannery wastewater

Wastewater samples were collected as a grap from chromium tanning stream duringthe period from February to December 2008. The color of tanning house effluent was dark blue and very acidic. The chemical, physical and microbiological properties of tannerywastewater over the study period showed that the tannery effluent exceeded the limitestablished by the Egyptian regulations for wastewater (Table 1).

Table 1: Chemical, physical and biological characterization of tannery wastewater* Max limit of criteria, Annex 1 of the Egyptian Law 4/94: Waste limitsNA, Not applicable

SE (Standard Error)2. Chemical precipitation of Cr(III) (Pre-treatment)2.1 Effect of precipitating agents on pH of the wastewater

ParametersFebruaryMayAugustDecemberMean valueMaximumlimit *ColorDark blueDark blueDark blueDark blueDark blueFree of colorCOD (mg/l)45383920353847654190 ± 20

100BOD (mg/l)1.122.221.51.7 ± 0.0360TSS (mg/l)4037354238 ± 2.160Salinity (mg/l)3529263731 ± 2.7NAEC (S/cm)55.647.8415750 ± 4.4NApH43.53.13.83.6 ± 0.076- 9Sulphate (mg/l)265235198301249 ± 3.91Cr(III) (mg/l)23502141162524102131± 8.71Cr(VI) (mg/l)900814625945821 ± 5.80.5Fungi (cfu/ml)10510098115418 ± 2.3NABacteria (cfu/ml)160153146162621± 5.3NAActinomycetes(cfu/ml)35322941137± 2.1NA

Hesham M. Abdulla, Engy M. Kamal, Amr H. Mohamed,Ahmed D. El-Bassuony

175

0123456789100.5 1 1.5 2 2.5 3concentration (g/100ml)

p H v a l u e

Cement dustLime

Different concentrations of the two precipitating agents (lime and cement dust) wereadded to 100ml of tannery effluent in glass jars and pH values were determined. The solutionpH is an important factor in determining the physical and chemical properties of the watersample, and it can be affected by the precipitating agents. Figure 1 shows that an increase inthe precipitating agent's dose is associated with increase in a solution pH. The initial pH of thesample was 3.1. After the addition of lime at a concentration of 1g/100ml, the pH increased to5. The maximum rate of pH increasing occurs where the concentration of lime is in the rangeof 2-3 g/100ml, which gives a final pH values of 7.7 to 8.2, which was close to pH 8 theoptimum value for Cr(III) precipitation (Patterson and Minear, 1975). In the case of cementdust, there was a little increase in pH value. After addition of 2g/100ml of cement dust, pHincreased to 3.5. The results revealed that there was high positive correlation between pHvalues and the precipitating agent dose (R = 0.950). The wastewater tends to be acidic, andcaustic or chemical addition is necessary in order to compensate the pH drop due tochromium precipitation. The presence of lime maintaining a conductive pH for the formationof Cr(OH)

precipitate, it might also have had some coagulating effect. The pH increaseindicates that coagulation of tannery wastewater could offer a possibility for treatedwastewaters which may have a neutral or higher pH value. Chemical precipitation maybenefit tanneries where the pH correction of acidic stream is required in order to meetdischarge requirements (pH 6-9).

Fig 1. Effect of precipitating agent's dose on pH of the tannery wastewater2.2 Effect of precipitating agents on COD of tannery wastewater

The effects of the precipitating agents on COD removal depend on pH value and thisis shown in figure 2. It can be seen that COD removal is most effective (45-70 %) at aconcentration various from 1.5 to 3 g/100ml of lime when the pH range was between 6.6 and8.2, but optimally (66-70%) at concentration from 2 to 3 g/100ml. There was a negativecorrelation between COD and pH value in lime (R = -0.968). Previous reports have shownthat, the rate of COD removal decreased if the pH was lower than 5.0 or higher than 8.5 (Song

et al

. 2004). On the other hand, cement dust additions has a little effect on COD removal itbrought COD reductions by 38% at 0.5 g/100ml but when the concentration increased, theCOD value increased until reach 4385 mg/l higher than the value of raw wastewater (3538mg/l). There was low positive correlation between COD and pH value in cement dust (R =

CHROMIUM REMOVAL FROM TANNERY WASTEWATER

176

0500100015002000250030003500400045005000

C O D ( m g / l )

00.511.522.533.54

p H v a l u e

050010001500200025003000350040000.5 1 1.5 2 2.5 3Concentration (g/100ml)

C O D ( m g / l )

012345678910

p H v a l u e

CODpH

0.505).

This could be explained by the composition of the cement dust 69.5 % calcium, 12.5% magnesium, 0.513 % ferric, 0.0313 % manganese and lime 25.08% (Rashed, 2008) whichmay be responsible for the COD of wastewater. Lime has a broader optimum pH rangecompared to cement dust. At a high pH lime addition resulted in a larger reduction of CODcompared with cement dust.

Fig 2. Effect of precipitating agents dose and pH on COD of the tannery wastewater. (A)Cement dust; (B) Lime2.3 Effect of precipitating agents on Cr(III) removal

The results shows that precipitating agents dose and settling time could affect theremoval of chromium. The maximum Cr(III) removal efficiency (98-99%) observed withinthe lime was attributed to 2-3 g/100ml, while slightly less removal efficiency (95.5-97%) wasrecorded at 0.5-1.5 g/100ml. Settling rate was high, resulting in 98% chromium removal at120min. Settling time higher than 120min didn't significantly affect chromium removal (P-value > 0.05). Cement dust had a different behaviour, the chromium removal was very low,ranging from 1.5 to 2.6% at 2-3 g/100ml and settling time showed no affect on chromiumremoval. In general, there was a very high positive correlation between precipitating agentsdose and Cr(III) removal (R = 0.999) (Figure 3). This could be partly explained by theoccurrence of competition between protons and metal ions under acid conditions (Sutherland,1989). It was recommended that coagulation should be operated at an alkaline condition toachieve maximum chromium removal (Bailey and Tunick, 1982).

Hesham M. Abdulla, Engy M. Kamal, Amr H. Mohamed,Ahmed D. El-Bassuony

177

Fig 3. Effect of precipitating agents dose and settling time on Cr(III) removal fromtannery wastewater. (A) Cement dust; (B) Lime3. Biological removal of Cr (VI)3.1 Screening of actinomycete isolates for chromium (VI) resistance

The actinomycete isolates were screened on the TSA agar plates containing chromium(VI) as (K

). Figure 4. shows that 22% of the examined actinomycetes (34 isolates)from the total number of isolates (150 isolates) showed resistant to the initial chromiumconcentration 100mg/l but by increasing the concentration, the number of resistant isolatesdecreased until reach five isolates (R

, S

and S

) at concentration of 1500mg/l.The results revealed that those five isolates could tolerate up to 2500mg/l but no furthergrowth was observed at higher concentration (3000mg/l).

This is a much higher resistancepattern than recorded in earlier reports for some actinomycete species; 100 mg/l by two

Streptomyces

strains (Luli

et al

., 1983), 500 mg/l by soil actinomycetes (Basu and Paul,1999), 200 mg/l by

Streptomyces griseus

(Laxman and More, 2002)..

00.511.522.53

C r ( I I I ) r e m o v a l ( % )

9394959697989910030 60 90 120 150 180Settling time (min)

C r ( I I I ) r e m o v a l ( % )

0.5g1g1.5g2g2.5g3g

Report Work