PII:S0273-1223(96)00144-8

8) Pergamon Wat. Sci. Tuh. Vol. 32. No, 12, pp. 105-J1 I. 199.5.Copyrighte 1996 IAWQ. Publishedby Elsevier SCIence Ltd

Printed in GreatBritaiD. All ngblt reserved.0273-122319.5 S9·.50 + 0'00

APPLICATION OF ANAEROBICDIGESTION TO THE TREATMENT OFAGROINDUSTRIAL EFFLUENTS INLATIN AMERICA

L. Borzacconi, I. L6pez and M. Vinas

Instituto de Ingenieria Qulmica, Facultad de Ingenieria; J. Herrera y Reissig565.Montevideo. Uruguay

ABSTRACT

A 1994 survey of high rate anaerobic reactors employed in the treaJment of agroindustrial effluents in LatinAmerica is presented. Data including number. volume and type of reactors. their evolution with lime andtype of effluents are discussed. Latin America has an increasing and significant panicipatioo in theapplication of anaerobic treatment to agroindustriaJ effluents. In particular, the design parameters of alreadyoperating reactors and the impact of applying this technology to the most typical effluents are analyzed. Theequivalent energy of biogas that can be produced through this technology is given. CoPyright to 1996 IAWQ.Published by Elsevier Science Ltd.

KEYWORDS

Anaerobic digestion; anaerobic reactors; UASB; agroindustrial effluents.

INTRODUCTION

Anaerobic digestion is a complex microbiological process within the carbon anaerobic cycle. Through thisprocess, in the absence of oxygen, organic matter can be transformed into biomass and inorganiccompounds. most of them volatile. Although this is a natural process, only in the last twenty years has itbecome a competitive technology in comparison with other alternatives. This has been achieved throughsystems which separate hydraulic residence time (HRT) from cellular residence time (CRT) by using highfa te reactors.

Since the energy crisis of the 70s anaerobic digestion has had a remarkable development Many researchgroups have developed significantly, and the use of large scale reactors to treat industrial and domesticeffluents increased. Latin America has followed the international trend (Craveiro, 1991; Montalvo et al.,1992) and is participating today on an acceptable level. The temperate and tropical climates of most LatinAmerican countriesimprove the operation of anaerobic reactors. The different realities of Latin Americancountries regarding energy supply and environmental regulations have conditioned the application of thistechnology.

105

106 L. BORZACCONI et al.

The agroindustry sector constitutes a major part of Latin American economies and has great developmentpotential. The effluents generated by this industrial sector generally have a significant polluting organic loadwhich makes them especially suitable to apply anaerobic technology. The anaerobic treatment of theseeffluents generates biogas and sludge that can be used as an energy source and a soil improver respectively.

DEVELOPMENT OF ANAEROBIC REACTORS APPLIED TOAGROINDUSTRIAL EFFLUENTS IN LATIN AMERICA

Anaerobic digestion technology has grown permanently in the region since 1982, both in number andvolume of reactors constituting an important contribution to the world-wide development of this technology.

Until mid-1994, a total of 396 anaerobic reactors with a total volume of 394,421 m3 had been built in LatinAmerica. This includes a 119,040 m3 reactor in Veracruz, Mexico, for the treatment of sewage and industrialeffluents, which has not started operating yet. 43% of the total. amounting to a volume of 182,286 m3,correspond to reactors that treat industrial effluents. and the rest to reactors that treat sewage or domesticeffluents (Borzacconi and Lopez, 1994). 97% of this 43% correspond to agroindustrial effluents; thefollowing data are obtained from this group.

Table I. Agroindustrial anaerobic reactors in Latin America

COUNTRYArgentineBoliviaBrazilColombiaCosta RicaCubaGuatemalaMexicoParaguayUruguayVenezuela

NUMBER5I

11510I2222I45

VOLUME (rn-)9105300

117054174245

240030002895020001020

16683

120 ,.---- ----------- - - - - -.=Ml

100

80

60

40

20

o 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993

• UASB o FA I!I Oth e rs

Figure 1. Evolution of the number of anaerobic reactors used for the treatment of agroindustrial effluents in LatinAmerica.

Agroinduslrial effluents treatment in LatinAmerica 107

Table I shows the contribution of the different countries (with data up to mid-1994) in number and volumeof reactors. Brazil has a noticeable predominance and is followed by Mexico. It is in these countries that agreater development and application of this technology are observed.

Figure I shows the evolution of the number of reactors. An exponential growth trend is observed. Reactorshave been discriminated according to their type. UASB (Upflow Anaerobic Sludge Blanket) reactors (atpresent, 82% of the total number) prevail over filters (14%); "others" includes basically hybrid reactors.Fluidized bed anaerobic reactors, have not been reported.

Table 2 shows the relative importance of different agroindustrial effluents in reactor number and volume.

Table 2. Relative importance of reactors according to the effluent

EFFLUENTMalting - BreweryDistillerySlaughterhouses - Pork processingYeastDairy productsSoft drinksCitrusFishPaperWineSweets, sugarCanningFlour, manioc, com flourCoffeeChocolateOthers

NUMBER(%)24.48.98.96.014.37.12.41.83.60.62.41.23.04.80.68.9

VOLUME(%)38.916.36.76.66.33.83.83.62.41.81.41.41.30.20.15.3

Figure 2 shows the treated pollution discriminated by effluent.

Brewery · Mailing )iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiilCanning

Choco late

Cigarette

CoHee

Dairy products

Distillery ••••••••••••••••••

Fish

Paper

Siaughterhhause • Pori<""----- -

Soil drinks .r-- -

Sweets. sugar

Yeast )II•••~Wine

Others )!!~!!I!!!!L-i---+----i----+--+--+---i,....--+--~o 1 ooסס0 ooסס20 300000

kgOa O/dooסס40 ooסס50

Figure2. Pollution treated in anaerobic reactors.

108 L. BORZACCONl etaL

There is. in general, a significant participation of out-of-the-region companies in the construction ofanaerobic reactors. in particular in the countries with the largest volumes. This participation focuses on theeffluents from malting-brewing. distilleries. yeasts and soft drinks. The treatment of these effluents by usingthis technology is firmly established world-wide (Borzacconi and Lopez, 1994).

MAIN APPLICATIONS OF ANAEROBIC DIGESTION TOAGROINDUSTRIAL EFFLUENTS

Four effluents of great importance. due to the development of the corresponding industries in Latin America,have been chosen to illustrate the application of anaerobic technology: brewing. malting, distillery (sugarcane vinasse), and yeast effluents.

These four effluents have different compositions. which must be taken into consideration at the moment ofapplying an anaerobic treatment While brewing and malting effluents do not originate major problems. theother two may have Ca. K and soi- concentrations above the recommended values (Duran et al.• 1991;Vinas et al.• 1994). In these last cases a particular study of the effluent is necessary. Typical values for theseeffluents are presented in Table 3.

Table 3. Typical values of effluent parameters"

EFFLUENT pH COD TS TKN N-NH 4 P Ca KBrewery 7.5 2550 1680 9.2 10.3Stillage 3.9 31290 21100 412 30 109Yeast 7.2 19500 1070 70 10 930

1473260

REFERENCECraveiro (1986)

Craveiro (1986)Vinas (1994) ••

• All values in mg/L, except pH... Reactor input.

The pollution generated in a year presented in Table 4 is estimated from typical values and annualproduction of these effluents in Latin America. The Equivalent Population has been calculated taking aproduction of 200 Uday per inhabitant with a concentration of 0.5 gCODIL (Vieira, 1984).

Table 4. Effluent characteristics

Brewery 140 • 1()6 3.0 4.2 • 108

Malting 8.1 * 106 2.7 2.2 * 107

Stillage 183 • I()6 30 5.5 • 109

Yeast ••• 5.8 * 1()6 12 7.0 * 107

EFFLUENT PRODUCTION •(m3/year)

Average COD ••(kgCOD/m3)

GENERATEDPOLLUTION(kgCOD/year)

EQUIVALENTPOPULATION

(millioninhabitants)

11.50.61501.9

* Pollock and Pool Ltd .• 1991; Bios Francia; ALAFACE. 1988; Hopsteiner; FAO, 1989... Borzacconi, 1994...* Only South America.

Parameters from UASB operating reactors are shown in Table 5 (Borzacconi and Lopez, 1994).

Comparing the pollution generated in a year with the pollution treated in a year (calculated from Fig. 2) weobserve that only a fraction of the total effluent generated by each industry is treated: Brewing 40%. Malting21%. Stillage 5%, and Yeast 60% (Fig. 3).

Agroindustrial effluents treatment in LatinAmerica

Table 5. VASB reactor parameters (mean values)

109

EFFLUENT

BreweryMaltingStillageYeast

NUMBER OFREACTORS

32I610

HRT(d)

0.330.631.8

1.654

LOAD(kgCOD/rn3.d)

8.72.7148.0

EFFICIENCY(%)81777566

Although other types of effluents have not been so thoroughly studied except by the research groups, theperspectives of introducing anaerobic technology for their treatment are good. An example is the coffeeindustry effluents in Colombia, where this technology has been largely developed using small volumereactors (Rojas, 1994). Another example is highly polluting effluents, such as those generated at tanneries(Koetz et al., 1994) and wool-scouring plants (Hernandez and Villas, 1994), where local studies for theanaerobic alternative have been started.

600

500

400

300

200

100

o

Figure 3. Pollution generated and treated and energy potential,

ECONOMIC CONSIDERAnONS

Apart from the inherent technical advantages, anaerobic technology has comparative economic advantagesover other types of treatment.

The potential of methane production and its energy equivalent were estimated from the generated pollutionneglecting the amount of biogas actually used as source of energy. For the four effluents previously chosenthese results are presented in Table 6. The potential of methane production was calculated from the datapresented in Table 4 and 5, considering a yield of biogas production of 0.4 m3/kgCOD removed and a 65%methane content of biogas.

Between 35% and 50% of the energy used in industrial processes can be recovered by using biogas, Forexample, it is estimated that in Cuba the energy production potential from biogas generated by the sugarcane industry and its byproducts is equivalent to 52,000 tons of oil per year (Valdes and Montalvo, 1994).

110

EFFLUENT

BreweryMaltingStillageYeast *

L. BORZACCONl et al:

Table 6. Effluent estimates

METHANE PRODUCTIONPOTENTIAL(m~yeM)

8.8 * 107

4.4 * 1()61.1 * 109

1.2* 107

ENERGY POTENTIAL(MJ/yeM)3.2 * 109

1.6 * 108

3.6 * 1010

4.3 * 108

• Only South America.

In a yeast producing plant that generates 120 m3/d of effluent, with a concentration of 19.2 kgCOD/m3, and63% efficiency in COD removal (Vinas et al., 1994), biogas could replace 45% of the fuel oil consumptionof the factory (on a basis of 70% utilization).

In an ethanol producing plant in Brazil where 1800 tons of sugar cane Me treated daily and which generates1500 m3 of vinasse per day, the costs per cubic metre of reactor range between U$S 330 and U$S 480.15,000 m3/day of biogas with a 60% methane content (Craveiro et al., 1986) Me produced.

For local technology in Mexico, the investment costs of an UASB anaerobic reactor Me estimated in U$S210,000 for a 1000 m3 reactor, and in U$S 330,000 for a 2000 m3reactor (Noyola and Monroy, 1994).

CONCLUSIONS

Anaerobic digestion technology applied to the treatment of agroindustrial effluents is being intenselydeveloped and has great potential for growth. This is particularly true for Latin America. where theagroindustrial sector has a decisive weight.

Most anaerobic reactors operating at industrial scale for this type of effluents Me UASB reactors (82% of thetotal), and this percentage shows a growing trend. There is enough information on a number of effluents soas to handle the values of design parameters,

The use of high rate anaerobic reactors. in comparison with other types of treatment, is highly competitivefor agroindustrial effluents, both regarding technological aspects and costs involved. The generated biogascan be used to replace a good part of the energy requirements of the plant itself.

REFERENCES

ALAFACE (1988). Bolelln de estadfsticas cerveceras.BiosFrancia. Bolelln Especial de Esladlstica. 1977 a 1989.Borzacconi, L. and Lopez, I. (1994). Re1evamiento de reactores anaerobios en America Latina. III Taller Latinoamericano de

Digestioll AflQerobia, Montevideo, Uruguay.Craveiro, A. M., Soares. H. M. and ScbmideU, W. (1986). Tecbnical aspects and COSts estimation for anaerobic systems treating

vinasse andbrewery/soft drink wastewater. Wat. Sci. Teen; 18, 123-134.Craveiro, A. M. (1991). Evolution and presentsituation of full anaerobic digestion of induslrial wastewaters in Brazil. Poster

Paperill SixthIniemationalSymposium 011AnaerobicDigestion: mayo12·16,SaoPaulo.FAO(1989). Anuario.Hirata, Y. S. (1994). Experi!ncias e perspectivas do tratamento anaerobic de efluentes industriais no Brasil. III Taller

Latinoamericano de Digestidll Anaerobia, Montevideo. Uruguay.HernAndez, A.• Vinas, M. (1994). Tratamiento anaerobio de efluentes de lavadero de lanas. III Taller Latinoamericano de

Digestion. Anaerobia, Montevideo, Uruguay.Hopsteiner. Boletfn annal, 1981, 1984, 1986.Koetz, P. R.• Faria. O. L. and Nunes. W. A. (1994). Upflow anaerobic reactors treating tannery effiuents. III Taller

Latinoamericano de Digestidll Anaerobia, Montevideo, Uruguay.Montalvo. S. J., AraUjo. J. A. and Escobedo. R. (1992). Tendencias aetuales en los estudios sobrc tratamientos anaercbicos, II

TallerLatinoamericano de Digestion A.fIDerobia. La Habana, Cuba.Noyola. A. and Monroy, O. (1994). Experiencias y perspectivas del tratamiento anaerobio en Mtxico. III TallerLati1loamericano

de Digestioll AflQerobia, Montevideo, Uruguay.PoUock and PoolLtd.(1991), TheMaltilll1lf1dustrv.

Agroindustrial effluentstreatmentin Latin America 111

Rojas. O. (1994). Aplicaci6n de tecnologfas de tratamiento anaerobio para la depuraci6n de aguas residuales. Experiencias enColombia. 111 Taller Latinoamericano de Digestion Anaerobia, Montevideo. Uruguay.

Valdt5,E. and Montalvo.S. J. (1994).Experiencias y perspectivas del tratamiento anaerobio en Cuba. 111 TallerLatinaamericanode DigestionAnaerobia, Montevideo. Uruguay.

Vieira. S. M. (1984). Tratamentode esgotospor digestoresanaer6bios de f1uxo ascendente, RevistaDAE.44(139).322-328.Villas, M~ Borzacconi, L. and Martinez. J. (1994). Anaerobic treatment of yeast manufacturing wastewaterin UASB reactors.

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