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CHEMICAL ENGINEERING TRANSACTIONS 

VOL. 38, 2014

A publication of 

The Italian Association 
of Chemical Engineering 

www.aidic.it/cet
Guest Editors: Enrico Bardone, Marco Bravi, Taj Keshavarz 
Copyright © 2014, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-29-7; ISSN 2283-9216       

Comparative Study on Efficiency of Biodigesters Upflow 
Anaerobic Sludge Blanket Treating Brewery Effluent 

Ederaldo Godoy Juniora,b,c,*,  Ricardo O. Jesusa,d, Argemiro C. Silvad, José Rui 
Camargoa,c, José R. Danilettoe, Eugênio P. D. Coelhob,f

aUniversity of Taubaté - Rua Daniel Danelli s/n, Zip: 12.050-720, Taubaté, SP, Brazil; 
bVale Soluções em Energia S.A. – Rod. Presidente Dutra, km 138, Zip: 12.247.004, São José dos Campos, SP, Brazil. 
cScholarship in and Productivity and Innovative Extension – CNPq 
dHeineken Brasil S.A.  Av. Pres. Humberto de Alencar Castelo Branco, 2911, Zip: 12.321-150, Jacareí, SP, Brazil 
ePolyEasy do Brasil S.A. 
fFederal University Itajubá 
godoyjr@unitau.br; ederaldo.godoy@vse.com.br; godoyjr@pq.cnpq.br  

The present work was a comparative study of four types of biodigesters systems upflow anaerobic sludge 
blanket (UASB) operating with brewery effluent in hot climate region. In case a UASB IC 20 meters high and 
660 m3 in volume in steel protected by epoxy resin, a conventional UASB 6 feet tall with a volume of 965 m3 
protected concrete with high density polyethylene (HDPE) film, a conventional UASB 6 feet tall with 
cylindrical volume of 2,000 m3 protected steel, and end a digester system consists of two UASB arranged in 
series, plug flow, forming cascade of 0.5 m3 volume at 1.2 m height each, built in HDPE rotomolded. Both 
systems operated hydrolyzed receiving tributary. The hydraulic retention time varied between 2.66 and 24 
hours, removing the organic load of between 70% and 91% and the methane concentration between 75% 
and 81%. Preliminary results allowed the comparison of performance and eco-efficiency of both systems 
studied when objective environmental sanitation and/or bioenergization of wastewater from the brewery.  

1. Introduction

The present work was a comparative study of four systems of biodigesters upflow anaerobic sludge blanket 
(UASB) operating with brewery effluent in a hot climate region. In this case, there was a UASB IC steel, a 
cylindrical steel UASB, a UASB rectangular concrete and high density polyethylene (HDPE) and also a 
digester system consists of two UASB plug flow in rotomolded HDPE. 
According Etheridge (2003) the biogas produced in breweries in surveys conducted in Europe, has an 
average concentration of 60 % methane. 
Yet, the biogas generated at the brewery under study, located in a region of warm weather, an average 
methane concentration of about 84 %. 
The development of anaerobic biological applications for the purpose of removing organic matter is due to 
the development of the biodigester upflow anaerobic sludge blanket, developed at the Agricultural University 
of Wageningen in the end of the 70s (Lettinga et al. 1980). 
The major factors that favor the use of the anaerobic process are low cost of implementation and operation, 
absence of electricity usage (does not need aeration for electrical equipment), produces low amount of 
excess sludge compared to aerobic systems, and cases with significant generation of biogas, can justify the 
energy utilization. 
The biodigester UASB is basically a tank where the tributary should be distributed as evenly as possible 
under a blanket composed of anaerobic microorganisms, that metabolize the organic load of the effluent 
producing treated effluent (liquid biofertilizer), small volume of sludge (biofertilizer solid) and biogas fuel. 
Later the particulate biodegradable material will be stabilized by the sludge (HUANG et al., 2006) 

 DOI: 10.3303/CET1438027 

 
 

 
 
 
 
 
 

 
 
 
 
 
 
 
 
 
 
 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Godoy Junior E., Jesus R.O., Silva A.C., Camargo J.R., Daniletto J.R., Coelho E.P.D., 2014, Comparative study 
on efficiency of biodigesters upflow anaerobic sludge blanket treating brewery effluent, Chemical Engineering Transactions, 38, 157-162  
DOI: 10.3303/CET1438027

157



The reactor efficiency can be measured by the COD (Chemical Oxygen Demand), which equals the amount 
of oxygen to oxidize organic matter. 
 
2. Materials and Methods  
 
The research was conducted in a sewage treatment station of a brewery located in Jacarei, Brazil, latitude 
23°18'19''S Longitude: 45°57'57''W, altitude: 567 meters relative to sea level. The climate, according 
KOPPEN is characterized as humid subtropical climate and an average temperature of 23°C. The effluent 
from a thermally stabilized at a temperature of 38°C brewery chemically with an average pH of 6.8 was 
hydrolyzed and used in the experiment. 
 
2.1 Characterization of the sludge 
The biodigester were inoculated with flocculent anaerobic sludge reactors of the brewery. The wastewater 
used in the experiment was of the brewery, stabilized thermally and chemically at COD of 2,090 mg/l. The 
flocculent sludge volume index was 20-40 ml/ g TSS. The sludge used in the reactor was pointed granules 
and they have up to 60 % CaCO3.The presence of filamentous microorganisms interconnected with archaea 
Methanothrix soehngenii is predominant. According to Stokes law larger aggregates will sink faster than 
discrete cells of the same density. The specific mass of the sludge granules varies between 1,020 and 1,080 
kg/m3 which are similar specific masses of dispersed cells, indicating that good settling properties of the 
sludge of 20 to 100 m/h are due to aggregation of microorganisms. Figure 1 illustrates the sedimentation of 
the sludge used and a microscopic view magnified 40 times. 
 
 
 
 
 
 
 
 
 
 
 

Figure 1: View of test sediment sludge used for inoculation of the digesters and sludge microscopic view 
magnified 40 times. 

2.2  Characterization of affluent 
The research was conducted in sewage treatment station of a brewery located in Jacarei SP, latitude 
23°18'19'' S, Longitude: 45°57'57'' W, altitude: 567 meters in relation to sea level. The climate, according 
KOPPEN is characterized as humid subtropical climate and an average temperature of 23°C. The 
experiments were performed using simulated sewage effluent from the brewery. It was then possible to 
simulate the organic load on the input from the digesters. 

2.3 Configuration UASB rectangular concrete 
The rectangular UASB digester used was constructed in reinforced concrete and protected from the harsh 
environment of the effluent through pockets polyethylene. The concrete digester contains two distinct zones 
for biological conversion of effluent: The lower treatment zone contains the granular sludge in fluidized or 
expanded form. The modulated separator installed at the top of the reactor will capture the biogas generated 
in the upper zone and the entire flow of treated effluent from the system. The treated liquid leaves the system 
through overflow in gutters collecting effluent, conveniently distributed at the top of the reactor. This reactor 
has a volume of 974 m3 and a treatment capacity of 120 m3/h. Figure 2 illustrates the schematic drawing 
and a photo of the protected concrete with HDPE film studied. 

 
 
 
 
 
 
 
 
 

Figure 2. Design and view the UASB digester system rectangular in concrete and HDPE 
 

158



2.4 Configuration UASB circular steel 
The UASB circular steel digester was protected by epoxy paint and anodic protection. This reactor follows 
the same principle of the reactor concrete previously presented and has a volume of 2.000 m3 and a 
treatment capacity of 210 m3/h. Figure 3 illustrates a photo of the UASB circular steel studied. 
 
 
 
 
 
 
 
 
 
 
Figure 3. View of the biodigester system UASB circular in steel 
 
2.5 Configuration UASB IC steel protected with epoxy 
The biodigester UASB IC in AISI 304 stainless steel has 20 meters height, volume of 664 m3 and a treatment 
capacity of 250 m3/h. The IC consists of a reactor, relatively large circular tank that contains two distinct 
zones for the biological conversion of the effluent: The lower treatment zone contains granular sludge in 
fluidized or expanded form. This zone of complete mixing is characterized by high speed upward flow of 
liquid. These speeds are produced by the flow of effluent fed plus the flow of internal recycle. The recycle 
flow is generated by the gas collected at the top of the first separator installed in the central part of the 
reactor and the resulting effect "gas lift”, which drags the liquid mix and sludge to the top of the reactor where 
it is effectively mixed with the pre-acidified tributary that is entering the process. The phase separator 
installed at the top of the reactor captures the biogas generated in the upper zone and the entire flow of 
treated effluent. The treated effluent leaves the system for overflow gutters collecting effluent distributed on 
top of the reactor. Figure 4 illustrates the schematic view of the digester and UASB IC used in the experiment. 

 
 
 
 
 
 
  

 
 
 
 
 
 
 
 
Figure 4: View of the digester system UASC IC in stainless steel AISI 304 

2.6 Configuration UASB Plug Flow Polyethylene rotomolded 
The bio-digester UASB plug flow was made of rotomolded polyethylene. Becuse the study was conducted 
in a WWTP of a brewery, the effluent already arrives with primary treatment.  
As the effluent passes through the blanket of sludge, anaerobic microorganisms digest the organic matter, 
producing biogas on the surface of the sludge granules increasing its fluctuation. 
 Depending on the upward speed of the flow, the blanket of sludge expands, and some of aerated sludge 
granules can be dragged toward the surface.  
In the separation zone of solid, liquid and gas phases, by means of a helical phase separator zone, the flow 
is directed to the output, the sludge granules are degassed, causing them to return to the blanket of sludge, 
the biogas bubbles are directed to the bell collection.  
Then, the effluent passes through the other UASB arranged in series. Figures 5 and 6 illustrate drawings 
and view the UASB digester system Plug Flow deployed  
 

159



 
 
 
 
 
 
 
 
 
 
 
Figure 5: Schematic drawing in section details of the Optimized System Biodigestores UASB. 
 
 
 
 
 
 
 
Figure 6: View of UASB System Biodigesters Plug Flow deployed in brewery in Jacareí SP Brazil. 

2.7 Parameters of evaluation for the efficiency of the system 
To evaluate the efficiency of the systems the following parameters were analyzed: a) COD b) BOD c) 
temperature d) Residence Time e) System Efficiency and f) Determination of Amount of Biogas. To measure 
the efficiency of the system sampling sites were at the entrance of biodigester UASB 1, the output of the 
biodigester UASB 1 and the output of the biodigester UASB 2. 
 
3. Results and Discussion 
 
3.1 UASB Plug Flow operating several hydraulic retention times 
Because UASB digesters Pug Flow were connected in series, the effluent from the reactor 1 is the affluent 
of reactor 2. Four flows rates were simulated to confirm the best efficiency for the system as shown in Table 
1, for a hydraulic retention time of 12 hours. 
 
Table 1: Results of analysis of digesters 

Flow rate 
(m3/dia) 

 

HRT  
(h) 

COD Inlet 
(mg/l)  

UASB 1 

COD Outlet
(mg/l) 

UASB 1 

COD Outlet
(mg/l) 

UASB 2 

COB5  
Inlet  

(mg/l) 

COB5  
Outlet  
(mg/l) 

Temperature 
(°C) 

Efficiency 
 (%) 

10 
7 
5 
2 

2,40 
3,43 
4,80 
12 

1100 
1100 
1100 
1100 

638 
654 
691 
704 

335 
323 
285 
216 

550 
550 
550 
550 

167,5 
161,5 
142,5 
108 

34 
35 
33 
35 

69,55 
70,64 
74,09 

80 
 
3.2 Removal of COD comparative between UASB 
Table 2 shows the results of the comparison between the systems. 
 
Table 2: Comparative characteristics of the parameters studied UASB reactors 

Reator 
Capacity

(m3) 

Flow rate 
(m3/d) 
(m3/h) 

HRT 
(h) 

COD Inlet 
(mg/l) 
(mg/l) 

COD 
Outlet
(mg/l)

Flow rate biogas
(Nm3/d) 

Temperature 
(oC) 

Efficiency 
% 

UASB Steel N°1 2.000 
3.120 
210 

9,52 2090 202 
 

3.330,43 
 

 
34 °C 

 
90,33 

UASB 
rectangular  

concrete N°2 
974 

2.880 
120 

8,12 2090 329 1.775 35 °C 84,26 

UASC IC 
stainless steel 

N°3 
664 

6.000 
250 

2,66 2090 420 3.507 33 °C 
 

79,90 
 

UASB 
 Plug Flow N°4 

1 
2 

0,0833 
12 2090 418 1,17 34 °C 80 

160



Figure 7 shows a comparative graph of efficiency and residence time between the reactors. It can be seen 
that the UASB reactor in cylindrical steel has a higher efficiency than the others, but it has a high design 
cost and maintenance. On the other hand, the IC reactor has a retention time and lower efficiency, but it is 
most used in breweries because of the low design cost and maintenance as well as the ability to treat larger 
flows of effluent compactly. 
 
 
 
 
 
 
 
 
 
 
Figure 7. Comparative graph of efficiency and residence time between UASB. 
 
3.2 Ammonia Nitrogen Removal 
 
The analysis of ammoniacal nitrogen inlet and outlet of the reactor was performed and it was possible to 
identify a reduction in the output of the reactors in HDPE. Probably the reduction of ammonia is due to the 
reactors being connected in series. Figure 8 shows the graph of the reduction of ammoniacal nitrogen on 
the output of the UASB reactor Plug Flow HDPE which was 18.6 to 15.9 mg/l. 
 
 
 
 
 
 
 
 
 
 
Figure 8. Graph of the reduction of ammoniacal nitrogen inlet and outlet of the reactors 
 
In a parallel experiment using two UASB plug low, cylindrical PVC, volume 46 m3, operates at a flow rate of 
1.91 m3/h, HRT of 24 hours, and average COD affluent of 1211.33 mg/l. The same brewer sludge was 
inoculated, but treating sanitary sewage, it was obtained a COD removal of 87.98%, and 16.44 of 
ammoniacal nitrogen. It is believed that the removal of ammoniacal nitrogen is related to its passage through 
more than one effluent sludge blanket. 
 
3.3 Quality of Biogas 

 
As Table 3 shows, the analysis of the biogas generated in the reactors was performed using the method of 
the gas chromatograph according to DIN 51872 (Bestimmung der Bestandteile Gaschromatographisches 
Verfahren). 
 
Table 3: Comparative characteristics of biogas produced in UASB analyzed 

Parameter Unit UASB Steel N°1 
UASB rectangular

concrete N°2 
UASC IC 

 stainless steel N°3
UASB Plug Flow  

CO2 
CH4 
H2S 
N2 
O2 

% 
% 
% 
% 
% 

22,03 
75,18 
0,03 
2,50 

0,261 

16,04 
81,10 
0,048 
2,615 
0,205 

17,77 
79,44 
0,03 
2,40 

0,262 

24,80 
72,33 
0,048 
2,615 
0,205 

 

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4. Conclusion 
 
After study four digesters UASB operating systems with effluent from brewery in a hot climate region, we 
conclude that the cylindrical UASB steel is the most efficient in the removal of organic matter, already in 
short time periods, In other words, periods of overload, IC is better, but has a high cost of implementation 
and maintenance compared to the other reactors. The cylindrical UASB steel showed the best efficiency for 
HRT of 9 hours. The UASB IC is the most used in breweries when there are problems to be compact area. 
It is noteworthy that the UASB rotational molded plug flow, has a removal efficiency of organic load very 
good, comparable to the IC when operated with HRT of 2.66 hours plus the cost of implementing the system 
is much smaller than the UASB IC, as well as maintenance because the IC any maintenance in sludge 
digestion column is the highest, rather risky from the point of safety, and in the case of plug flow UASB this 
height can be reduced to 6 meters, in addition to the gain removal of ammonia. With this, the plug flow UASB 
system has proved to be more feasible when compared to conventional models. 

Acknowledgment 
 
Logistical support of the UNITAU, PolyEasy of Brazil S.A., Heineken SA of Brazil and VSE (Vale Soluções 
em Energia S.A.). To support CNPq in the form of Productivity and Innovative Extension Scholarship. 
 
References 
 
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de Minas Gerais, 379p., 2007. 

CASTRO, F.M.S., Estudo do comportamento hidrodinâmico de uma nova proposta de configuração interna 
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FEACHEM, R.G., BRADLEY, D.J., GARELECK H., MARA D. D., 1983, Sanitation and Disease – Health 
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GODOY JUNIOR, E., Desenvolvimento e avaliação de uma estação ecoeficiente de tratamento de esgoto 
e reuso de água, com sistema registrador queimador, para baixas vazões de biogás e cogeração de 
energia. Tese de doutorado em engenharia mecânica, UNESP, Guaratinguetá, SP, 2010, 149p. 

GODOY JUNIOR, E., JESUS, P.H. Sistema Difusor de Efluentes para biodigestores anaeróbios de fluxo 
ascendente, Patente número: BR1020130172138, São Paulo, SP, 9p., 2013. 

HUANG, J. et al. Consecutive reaction kinetics involving a layered Structure of the granule in UASB reactors. 
Water Research, 40, 2947 – 2957, 2006. 

LETTINGA, G. et al. Use of Upflow Sludge Blanket (UASB) Reactor concept for Biological Wastewater 
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