[eBook ENG] Production of Hidrogen and Methane

8/14/2019 [eBook ENG] Production of Hidrogen and Methane

1/5

J. Chin. Inst. Chem. Engrs., Vol. 34, No. 6, 683-687, 2003

Short communication

Sequential Production of Hydrogen and Methane

from Wastewawter Sludge Using AnaerobicFermentation

Chi-Chung Wang[1], Chih-Wen Chang[2], Ching-Ping Chu[3], Duu-Jong Lee[4]

Department of Chemical Engineering, National Taiwan UniversityTaipei, Taiwan 106, R.O.C.

Bea-Van Chang[5]

Department of Microbiology, Soochow University

Taipei, Taiwan 111, R.O.C.

AbstractThis study demonstrates the feasibility of sequentially producing both hydrogenand methane from wastewater sludge using a clostridium strain, as was isolated by Wang etal. (2003a). Three commonly used pre-treatments were applied to wastewater sludge to in-

crease the hydrogen yield. Then, the waste liquor was externally dosed with methanogenicbacteria to produce methane. The waste liquor after fermentation of hydrogen produced

more methane than was directly derived without fermentation of hydrogen. The reduction ofnitrogen-containing organic matter is shown to compete with the formation of hydrogen,yielding ammonium nitrogen (NH3-N) in the fermented liquor.

Key Words : Anaerobic fermentation, Hydrogen, Methane, Clostridium, Pre-treatment

INTRODUCTION

Hydrogen is a clean source of energy.Bio-conversion of biomass to produce hydrogen hasbeen demonstrated, using the anaerobic fermentationof high-strength wastewater (Bolliger et al., 1985;Liu et al., 1995; Ueno et al., 1996; Zhu et al., 1999),solid waste (Mizuno et al., 2000a; Lay et al., 1999),and some well-defined compounds in water, such asmolasses (Tanisho and Ishiwata, 1994), glucose(Kataoka et al., 1997; Lin and Chang, 1999), crystal-line cellulose (Lay, 2001), peptone (Bai et al., 2001),

and starch (Lay, 2000). Methods for promoting hy-drogen production have been reported (Tanisho andIshiwata, 1995; Tanisho et al., 1998; Mizuno et al.,2000b; Sparling et al., 1997; Liang et al., 2001). Inthe literature, anaerobic fermentation has yieldedaround 11 mg-H2/g-dried solids (DS) from glucosesolution (Kataoka et al., 1997), and 1.4 mg-H2/g-DSfrom peptone-containing solution (Liang et al., 2001).Only a few data on the hydrogen yield from waste-

water sludge have been presented at local confer-ences, including the data of Huang et al.(2000) andCheng et al.(2000).

Recently, Wang et al.(2003a) conducted the first

systematic study of the production of hydrogen fromwastewater sludge, and found a ratherhigh hydrogenyield from wastewater sludge using a clostridiumstrain isolated from the sludge sample. Later, Wanget al.(2003b) claimed that applying a filtrate to thesludge could produce more hydrogen than could beobtained using all of the particles in the sludge. Al-though these studies successfully established the fea-

sibility of producing hydrogen from wastewatersludge, the hydrogen formed during the first 16-24 hof fermentation was consumed in a later stage. Wanget al. (2003a) blocked the methanogenic pathwayusing a pre-treatment. However, much of the pro-duced hydrogen was still consumed. The pathway forhydrogen consumption remains unknown, but is ofacademic and practical interest.

This study evaluated the feasibility of sequen-

[1] [2] [3]

[4] ,To whom all correspondence should be addressed [5]


2/5

684 J. Chin. Inst. Chem. Engrs., Vol. 34, No. 6, 2003

tially producing hydrogen and methane from waste-water sludge using a clostridium strain under anaero-bic conditions. Based on test data, a combined proc-ess, involving two fermenters, is proposed.Additionally, the possible incorporation of nitrogencycles, which compete with the production of hy-drogen during sludge fermentation, is demonstrated.

MATERIALS AND METHOD

The substrate

Waste activated sludge was extracted from awastewater treatment plant of the Presidental Enter-prise Corp., Taiwan, which daily treats 250 tons offood-processing wastewater using primary, secon-

dary and tertiary treatments. The pH of the sludgewas about 6.4. The chemical oxygen demand (COD)for the sludge was 9,600 mg/L (TCOD), as deter-mined by directly reading a spectrometer (DR/2000,HACH, U.S.A.). The COD for the filtrate of thesludge sample after it was filtered through a 0.45 mmembrane was called the soluble COD (SCOD), andwas 465 mg/L for the original sludge. The elementalcomposition of the dried samples was C: 34.3%, H:5.6%, and N: 5.5%, according to an elemental ana-lyzer (Perkin-Elmer 2400 CHN).

Three pretreatments were applied to the originalsludge to determine their effects on the yield of hy-

drogen. These pretreatments not only released in-soluble organic matter into water to enhance methaneproduction (Lee and Mueller, 2001), but also deacti-vated the methanogenic bacteria in the sludge toblock the pathway of the conversion of hydrogen tomethane. These pretreatments are summarized asfollows.

(1) Acidification: perchloric acid (HClO4) was

mixed with the sludge sample for 10 mins to ad-just the pH of the suspension to 3. Then, thesample was stored at 4C for 6 h (Jean et al.,2000).

(2) Sterilization: sludge samples were pasteurized at121C and 1.2 kgf/cm

2(HUXLEY AUTOCLAVE,

HL-360) for 30 min.(3) Freezing and thawing: the sludge was frozen at

17C for 24 h in a freezer and then thawed foranother 12 h in a water bath at 25C (Hung et al.,1997).

The inoculum

Wang et al. (2003a) isolated the inoculum. Thestrain was selected and identified as Clostridium

bifermentans using the polymerase chain reaction(PCR) and 16S DNA sequence analysis. In some

methane production tests, anaerobe K8 was added tothe samples after bio-hydrogen tests were performed.K8 was collected from the bottom sediment at aknown site of the Tam-Shui River (near Taipei). Thismixed culture had high methane productivity (Changet al., 1996).

Fermentation and tests

Batch fermentation tests were performed in 125mL serum bottles. In each bottle, 45 mL of substrate,original or pre-treated, was mixed with 5 mL of seedbacteria suspension and anaerobically incubated at35C without stirring or adding any nutrients. Thebottles were capped with butyl rubber stoppers andwrapped in aluminum foil to prevent photolysis ofthe substrate. Gas and liquor samples were collectedat 8, 16, 24, 32, 40, 48, 72, and 96 h of fermentation.

At each time interval, and for each substrate, the gascompositions of three serum bottles were measuredand their average was reported. After the measure-ments were made, these samples were abandoned toprevent the introduction of any possible error associ-ated with the sampling procedure, such as gas leak-age.

Tests to determine potential methane productionwere performed after 96 h of hydrogen fermentation.The anaerobe K8 was added to some serum bottlesafter the hydrogen fermentation tests were completed.The gas samples were collected at 24 h intervals up

to 240 h.A GC-TCD (Shimadzu, GC-8A), equipped with

a stainless column packed with Porapack Q (50/80mesh) at 70C and a thermal conductivity detector(TCD), was used to measure the hydrogen andmethane concentrations in the gas phase. The tem-perature of both the injector and the detector of theGC was 100C. Nitrogen served as the carrying gaswith a flow rate of 20 mL/min. An integrator(HP3396 Series II) was used to integrate the peakarea of the effluent curve, and to measure the gase-ous concentrations. Repeated measurements revealedthat the hydrogen and methane contents thus deter-mined included maximum relative errors of 15% and10%, respectively. The hydrogen content in the an-aerobic glove box was also measured, and was sub-tracted from the hydrogen concentrations read intheserum bottles.

The concentrations of ammonia-nitrogen (NH3-N)in the supernatant were measured during the fermen-tation test. The filtrate samples were extracted bycentrifugating the sludge at 13,500 rpm for 1 min.The NH3-N concentration of the filtrate was meas-ured spectrophotometrically (425 nm) using a mix-ture of the filtrate sample with two drops of mineral

stabilizer, three drops of polyvinyl alcohol dispersingagent, and 1 mL of Nessler agent in a spectropho-


3/5

Chi-Chung Wang, Chih-Wen Chang, Ching-Ping Chu, Duu-Jong Lee, and Bea-Van Chang : Sequential Production of 685Hydrogen and Methane from Wastewawter Sludge Using Anaerobic Fermentation

tometer (DR/2000, HACH, U.S.A.). Standard solu-tions of NH3-N were used for calibration.

RESULTS AND DISCUSSION

Hydrogen production

Figure 1 showsthe hydrogen yield forone gramof dried solid (DS). In contrast to the 66 h time lagreported by Cheng et al. (2000), this study foundnegligible time lag for hydrogen production, perhapsbecause the inoculum was directly derived from thesubstrate sludge. The hydrogen concentration in thegas phase yielded an increasing-decreasing curve,with a peak at about 16-24 h (indicated in Fig. 1 bythe arrow). A specific quantity of produced hydrogen

was, thus, consumed. As Fig. 1 reveals, the spe-cific hydrogen yield reached 5 g/kg-DS for theoriginal sludge, much higher than that reported byHuang et al. (2000) (0.16 g-H2/kg-DS). Meanwhile,sterilization increased the specific hydrogen yield toabout 21.5 g-H2/kg-DS. The acidification, freezingand thawing treatments enhanced the yield to about9-10 g/kg-DS. This observation shows that the yieldof hydrogen from wastewater sludge is similar to thatfrom glucose solution if the former is subjected tosuitable pretreatment.

Figure 2 plots the variation in the pH of the solu-tion during fermentation. Clearly, during hydrogenproduction, the solutions pH increased with timeuntil the yield peaked at 16-24 h, after which time thepH dropped or did not increase further in the case ofthe acidified sludge. The formation of hydrogenproduced a by-product acidic in nature.

Fig. 1. Time course of the hydrogen yield in the gas

phase. Clostridium strain was added at hour 0,

and K8 was added at hour 96. Each data point is

the average of triplicate tests.

Figure 3 plots the time evolution of the concen-tration of ammonium nitrogen (NH3-N) in the sus-pension. In the case of the original, sterilized andfreeze/thawed sludges, the NH3-N concentration in-creases with the amount of hydrogen produced untilit reached a peak at about 24 h, after which time itleveled off in the hydrogen consumption phase. Thenitrogen-containing compounds were reduced toammonium nitrogen when hydrogen was formed.The acidified sludge, on the other hand, produced theleast NH3-N of all the tests. Hence, although the ni-trogen cycles competed with hydrogen formation,they are not preferred in acidic environment.

Fig. 2. Time course of the pH of the suspension.

Fig. 3. Time course of the ammonium nitrogen con-

centration during hydrogen and methane pro-

ducing phases.

Methane production

In the hydrogen fermentation tests, the amount ofmethane produced was negligible (0-96 h as shownin Fig. 4). Hence, the consumption of hydrogenshown in Fig. 1 was not associated with methane

(g

/kg-DS)

Time (h)

NH3-N

(mg/L)

200


4/5

686 J. Chin. Inst. Chem. Engrs., Vol. 34, No. 6, 2003

Fig. 4. Time course of the methane yield. The anaerobe

K8 was added at hour 96.

production. Since only a small proportion of organicmatter was converted into hydrogen, the potential forusing the exhausted liquor to produce methane wasof interest. Anaerobe K8 was added to the serum bot-tles after 96 h of hydrogen fermentation.

After K8 was added, as Fig. 4 shows, the amountof methane accumulated in the serum bottles in-creased monotonically with time. The amount ofmethane produced followed the order freeze/thawed> original > sterilization >> acidification. Althoughthe acidification produced hydrogen at a yield twotimes that of the original sludge, it produced lessmethane. After K8 was added, the solutions pH in-creased again, corresponding to the formation ofmethane. The acidified sludge, however, also did notundergo an efficient increase in pH, and so generatedleast methane.

Sequential process

The data shown in Fig. 4 reveal that the sludgeafter hydrogen fermentation was more readily di-gestable than the unfermented sample. This observa-tion implies that some products of the fermentation

test promoted methane production. As Wang et al.(2003b) concluded, fermenting the filtrate of thesludge alone could produce more hydrogen than fer-menting all of the sludge (including solids). Hence,Fig. 5 shows a proposed combined process thatyields hydrogen and methane sequentially. Restated,the filtrate is first separated from the raw sludge(with or without pretreatment) and is sent to fer-menter #1 to produce hydrogen. Then, the waste liq-uor is mixed with the cake from the solid-liquidseparator and is sent to fermenter #2 to producemethane. This sequential arrangement effectively

produces hydrogen and methane from wastewatersludge.

Raw

sludge

Solid-Liquid

SeparationFermenter

H2

filtratePretreatment

Fermenter

CH4

Mixer

Liquor

CakeWaste

Liquor

Fig. 5. A proposed sequential process that produces

hydrogen and methane from wastewater sludge.

CONCLUSION

The clostridium strain used herein could fermentwastewater sludge into hydrogen at a much higher

rate than heretofore reported in the literature. Acidi-fication, sterilization and freezing and thawing couldincrease the hydrogen yield. After hydrogen fermen-tation, adding a methanogenic culture to the fer-mented liquor accelerated the production of methane,such that the rate of production was higher than thatof unfermented samples. A combined process thatcan produce hydrogen and methane sequentially has,thus, been proposed. The reduction in the amount ofnitrogen-containing matter can reduce the hydrogenyield, the effect of which is less profound in anacidic environment.

ACKNOWLEDGEMENT

Support for this work by the National ScienceCouncil, R.O.C., is gratefully appreciated.

REFERENCES

Bai, M. D., S. S. Cheng, and T. C. Tseng, Biohydrogen Pro-

duced due to Peptone Degradation by Pretreated Seed

Sludge, The IWA Asia-Pacific Regional Conference(Wa-

terQual 2001), Fukuoka, Japan (2001).

Bolliger, R., H. Zrrer, and R. Bachofen, Photoproduction of

Molecular Hydrogen from Wastewater of a Sugar Refinery

by Photosynthetic Bacteria, Appl. Microbiol. Biotechnol.,

23, 147 (1985).

Chang, B. V., J. X. Zheng, and S. Y. Yuan, Effects of Alter-

native Electron Donors, Acceptors and Inhibitors on PCP

Dechlorination in Soil, Chemosphere, 33, 313 (1996).

Cheng, S. S., M. D. Bai, S. M. Chang, K. L. Wu, and W. C.

Chen, Studies on the Feasibility of Hydrogen Production

Hydrolyzed Sludge by Anaerobic Microorganisms, The

25th

Wastewater Tech. Conference, Yunlin, Taiwan (inChinese) (2000).


5/5

Chi-Chung Wang, Chih-Wen Chang, Ching-Ping Chu, Duu-Jong Lee, and Bea-Van Chang : Sequential Production of 687Hydrogen and Methane from Wastewawter Sludge Using Anaerobic Fermentation

Huang, C. S., C. Y. Lin, Y. Y. Tsai, and Y. G. Shieh, Pre-

liminary Study of Anaerobic Hydrogen Production Using

Various Substrates and Incubation Methods, The 25th

Wastewater Tech. Conference, Yunlin, Taiwan (in Chinese)

(2000).

Hung, W. T., W. H. Feng, I. H. Tsai, D. J. Lee, and S. G.

Hong, Unidirectional Freezing of Waste ActivatedSludge: Radial Freezing Versus Vertical Freezing, Water

Res., 31, 2219 (1997).

Jean, D. S., B. V. Chang, G. S. Liao, G. W. Tsou, and D. J.

Lee, Reduction of Microbial Density Level in Sewage

Sludge through pH Adjustment and Ultrasonic Treat-

ment, Water Sci. Technol., 42(9), 97 (2000).

Kataoka, N., A. Miya, and K. Kiriyama, Studies on Hydro-

gen Production by Continuous Culture System of Hydro-

gen-Producing Anaerobic Bacteria, Water Sci. Technol.,

36(6-7), 41 (1997).

Lay, J. J., Y. J. Lee, and T. Noike, Feasibility of Biological

Hydrogen Production from Organic Fraction of Municipal

Solid Waste, Water Res., 33, 2579 (1999).

Lay, J. J., Modeling and Optimization of Anaerobic Digested

Sludge Converting Starch to Hydrogen, Biotechnol. Bio-

eng., 68, 269 (2000).

Lay, J. J., Biohydrogen Generation by Mesophilic Anaerobic

Fermentation of Microcrystalline Cellulose, Biotechnol.

Bioeng., 74, 280 (2001).

Lee, D. J. and J. A. Mueller, Preliminary Treatments,

Sludge into Biosolids, L. Spinosa and P. A. Vesilind, Ed.,

International Water Association, U.K. (2001).

Liang, T. M., K. L. Wu, and S. S. Cheng, Hydrogen Produc-

tion of Chloroform Inhibited Granular Sludge, The IWA

Asia-Pacific Regional Conference (WaterQual 2001), Fu-

kuoka, Japan (2001).

Lin, C. Y. and R. C. Chang, Hydrogen Production during the

Anaerobic Acidogenic Conversion of Glucose, J. Chem.

Technol. Biotechnol., 74, 498 (1999).

Liu, S. J., W. F. Yang, and P. Q. Zhou, The Research on

Hydrogen Production from the Treatment of Bean Prod-

ucts Wastewater by Immobilized Photosynthetic Bacte-

ria,Environ. Sci ., 16, 42 (1995).

Mizuno, O., R. Dinsdale, F. R. Hawkes, D. L. Hawkes, and T.

Noike, Enhancement of Hydrogen Production from Glu-

cose by Nitrogen Gas Sparging,Bioresource Technol., 73,

59 (2000a).

Mizuno, O., T. Ohara, M. Shinya, and T. Noike, Characteris-

tics of Hydrogen Production from Bean Curd Manufactur-

ing Waste by Anaerobic Microflora, Water Sci. Technol.,42(3-4), 345 (2000b).

Sparling, R., D. Risbey, and H. M. Poggi-Varaldo, Hydrogen

Production from Inhibited Anaerobic Composters, Int. J.

Hydrogen Energy, 22, 563 (1997).

Tanisho, S. and Y. Ishiwata, Continuous Hydrogen Produc-

tion from Molasses by the Bacterium Enterobacter Aero-

genes,Int. J. Hydrogen Energy , 19, 807 (1994).

Tanisho, S. and Y. Ishiwata, Continuous Hydrogen Produc-

tion from Molasses by Fermentation Using Urethane Foam

as a Support of Flocks, Int. J. Hydrogen Energy , 20, 541

(1995).

Tanisho, S., M. Kuromoto, and N. Kadokura, Effect of CO2

Removal on Hydrogen Production by Fermentation, Int. J.

Hydrogen Energy, 23, 559 (1998).

Ueno, Y., S. Otauka, and M. Morimoto, Hydrogen Produc-

tion from Industrial Wastewater by Anaerobic Microflora

in Chemostat Culture, J. Fermentation Bioeng., 82, 194

(1996).

Wang, C. C., C. W. Chang, C. P. Chu, D. J. Lee, B. V. Chang,

and C. S. Liao, Producing Hydrogen from Wastewater

Sludge by Clostridium Bifermentans, J. Biotechnol., 102,

83 (2003a).

Wang, C. C., C. W. Chang, C. P. Chu, D. J. Lee, B. V. Chang,

C. S. Liao, and J. H. Tay, Using Filtrate to Produce

Bio-Hydrogen by Anaerobic Fermentation, Water Res.,

37, 2789 (2003b).

Zhu, H., T. Suzuki, A. A. Tsygankov, Y. Asada, and J. Mi-

yake, Hydrogen Production from Tofu Wastewater by

Rhodobacter sphaerodies Immobilized in Agar Gels, Int.

J. Hydrogen Energy, 24, 305 (1999).

(Manuscript received Dec. 17, 2002, and accepted Jul. 4, 2003)

Wang et al. (2003a)

Documents

[eBook ENG] Production of Hidrogen and Methane