History of Anaerobic Digestion Para aula

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History of Anaerobic Digestion 
Prof. Dr. Eugenio Foresti 
Based on McCarty, P.L. “One hundred Years of Anaerobic Digestion” 
Content: 
Introduction 
Definition of Anaerobic Digestion 
From the observation of methane formation on natural environments to 
technological applications on wastewater treatment 
Early years of anaerobic technology 
Anaerobic Digestion of Sludge and Agricultural Wastes 
Role of AD in Conventional Wastewater Treatment Plants 
Kinetics, microbiology and biochemistry: Remarkable advances on process 
fundamentals that lead to technological development 
Anaerobic Digestion in Latin-America and India 
Recent process developments 
 
Introduction 
Definition of Anaerobic Digestion 
According to Mosey (1983), “The anaerobic digestion process is a natural biological 
process in which a close-knit community of bacteria co-operates to form a stable, self-
regulating fermentation that converts waste organic matter into a mixture of carbon-
dioxide and methane gases”. 
This definition is still valid, although formulated when methane was the most important 
final product desired. A broader definition, however, would include all intermediary 
valuable products possible to be formed and separated, both from liquid (such as 
volatile fatty acids – VFA, and solvents) and gas (such as hydrogen) phases. The 
urgency for improving environmental sustainability has driven the anaerobic process 
development to obtain not only energy carriers from wastes, but also other fermentation 
products. 
Probably, a broader definition would be: “The anaerobic digestion process is a natural 
biological process occurring in the absence of molecular oxygen in which different 
microorganisms co-operate to form a stable, self-regulating fermentation that converts 
waste organic matter into final gas products (H2, CH4 and CO2), valuable dissolved 
compounds in the liquid phase and stabilized biosolids.” 
Methane Formation in Natural Environments 
There are records on the use of biogas in the East, especially China, probably more than 
2000 years ago. In the West, Van Helmont assumed that flammable gases could derive 
from organic matter decomposition in 17
th
 century. Many authors attributed the first 
observation of the occurrence “combustible air” formed from sediments in lakes, ponds 
and streams to the Italian physicist Alessandro Volta in 1776. He associated the 
“combustible air” formation to the presence of plants in the sediment. Later on, other 
scientists, such as Bunsen and Hoppe-Syler, confirmed the observation of Volta. In 
1804 – 1808 Dalton, Henry and Davy established that the combustible gas was methane. 
The liberation of methane from decomposing manure piles was observed by Reiset in 
1856 and Béchamp associated methane formation to a microbiological process in 1868. 
Popoff (1875) reported on the natural formation of methane in different environments 
and from different substrates. In 1890 Van Senus associated the anaerobic 
decomposition of cellulose to the cooperation of several microorganisms. After, 
additional developments on the anaerobic digestion process understanding can be 
credited to the interest related to improve technological applications. 
Early Years of Anaerobic Technology 
Although the first digestion plant was constructed in 1859 at a leper colony in Bombain, 
the first significant contribution related to the treatment of wastewater suspended solids 
is credited to M. Louis Mouras (McCarty, 1982). In 1882, the French journal Cosmos 
published a description of na air-tight chamber – the “Mouras Automatic Scavenger”. 
This chamber was meant to retain and decompose the influent suspended solids. 
However, due to its hydraulic characteristics, that allowed the permanent contact of the 
influent with the digesting sludge, the effluent still contained suspended solids not 
completely stabilized. 
The advantages of holding the solids inside the tank for the hydrolytic and bacteriolytic 
actions of the microorganisms to obtain a stable effluent suspended solids was indicated 
by the Massachusetts State Board of Health in 1984. 
Different researchers started to study possibilities to better retain the solids. In England 
W. D. Scott- Moncrief (1990 – 1991) constructed a unit composed of two chambers: an 
empty chamber bellow and a stone-bed above. 
Attempting to separate the sedimentation zone from the solid digestion zone, in 1895 
Donald Cameron constructed a “septic tank” similar to the Moras’ automatic scavenger 
to pre-treat 60,000 U.S. gallons per day of screened combined wastewater. He patented 
his invention, propitiating other engineers to get involved in designing tanks similar to 
the Mouras’ automatic scavenger, such as A. N. Talbot. Cameron recognized the value 
of the methane produced during the anaerobic digestion of the solid fraction. He was 
probably the first engineer to use methane for heating and lighting the area near the 
treatment plant. 
Septic tank reduced the problems associated to sludge disposal. But it often produced 
effluent containing a black sludge not completely digested, and emitting offensive odor. 
To solve this problem, Harry W. Clarck stated that the solids should be separated from 
the liquid flow and digested separately. 
In 1904, William Travis proposed a septic tank that allowed a partial separation of the 
solid phase from the liquid phase in a single unit. The presence of baffles partially 
immersed in the liquid phase functioned as a barrier for the emission of suspended 
solids that should be driven to a hydrolyzing chamber. However, he allowed some 
wastewater to flow through the hydrolyzing chamber creating problems with the 
emission of suspended solids in the effluent. A Travis Tank was being constructed in 
Emscher in 1905 when Karl Imhoff assumed the responsibility of the Emscher Drainage 
District Board. He modified the Travis Tank design providing the isolation of the 
digestion zone from the sedimentation zone to avoid the wastewater to washout 
digesting solids. The Imhoff Tank became the most important unit for the primary 
treatment and solids digestion for attending small populations. However, the 
constructive characteristic of the Imoff Tank was a serious drawback for its use in 
centralized treatment plants in cities. In its design, the superficial area was imposed by 
the sedimentation zone. As high the flow rate, as high the superficial area. As the tank 
depth was mainly determined by the radius of the circular tank, the unit resulted very 
tall for populations higher than about 5,000 inhabitants. 
Attempts to separate the solids and digesting them in a separate tank were not 
successful at the beginning. Finally, the presence of a clarifier to separate the settleable 
solids and the use of sludge-heating to improve the digestion process was demonstrated 
at Easen-Reallinghausen plant. Thus, a new conception of sewage treatment plant 
emerged composed of screen and grit chamber as preliminary units; 
clarification/sedimentation to separate the liquid from the sludge phase; digesters for 
solids stabilization and aerobic reactors for dissolved organic matter in the liquid phase. 
The importance of the temperature for a stable process led many researchers to direct 
their attention to this particular aspect. In 1927, Rudolfs demonstrated that temperature 
affects the velocity of the process but not the total amount of methane that can be 
obtained from the sludge. The existence of two optimum temperature ranges, 
mesophilic – 28oC to 35 oC - and thermophilic - 55oC to 60oC - was demonstrated by 
Fair and Moore in 1930. By the end of the 1930s, sanitary engineers could have enoughknowledge about domestic wastewater treatment to design systems able to remove 
organic matter efficiently and produce very stable digested solids. 
Even currently, many cities have domestic wastewater treatment plants designed 
according to fundamentals of sludge anaerobic digestion established before 1950. 
The possibility of producing biogas in rural areas attracts the attention of many 
countries, especially in India, in the beginning of 1900 and there were several attempts 
to produce biogas from manure. But, it was only in the 1950s that several plants were 
designed and resulted in the development of the floating-dome model. Interest in biogas 
production from manure was resumed in early 1960 and many digesters were designed 
to produce 3 to 14 m
3
.d
-1
 of biogas. Inspired in small digester installed in China, the 
“Chinese” design substitutes the steel floating-dome by a dome-shaped model. This 
model is claimed to be cheaper and more resistant to corrosion than the Indian Digester. 
In 2011, about four million biogas plants were operating in Indian. In 2009, the number 
of rural digesters accounted over 37 million digesters in China. 
 
Sludge digesters in cities and manure digesters in rural areas changed very little from 
the former design proposed in the last century to current days. This fact contrasts with 
the development of anaerobic reactors for the treatment of wastewater liquid phase. The 
increasing knowledge on the anaerobic process fundamental resulted in new 
configurations of anaerobic reactors from 1950 onwards. A better understanding of 
process chemistry and microbiology has driven the most important advances in 
anaerobic reactors’ design and process control. 
 
Evolution of Chemistry and Microbiology 
 
In the 1890s, Omelianski isolated organisms that produced hydrogen, acetic, and butyric 
acid from cellulose fermentation process and reported on methane formation from H2 
and CO2. 
 
 4H2 + CO2 CH4 + 2 H2O 
 
Söghen confirmed the formation of methane from H2 + CO2 later. Although he could 
not demonstrate the mechanism of methane formation from acetate, he formulated the 
hypothesis of acetate decarboxylation to form methane and carbon dioxide, a very 
controversial statement at that time. 
 
The experience with sludge digestion leads Thum and Reiche to describe the anaerobic 
process to occur in sequential acid and methanogenic phases. In 1916, Imhoff adopted 
the expressions “acid digestion” and methanogenic digestion”. 
From 1920 to 1930, Buswell and co-workers developed intense studies at lab- and pilot-
scale and revealed the viability of anaerobic processes for the treatment of a wide range 
of industrial and agricultural residues, besides domestic sewage. They demonstrated the 
importance of volatile organic acids as intermediary metabolic products. They also 
established the stoichiometric relation to predict the potential methane production from 
organic matter anaerobic decomposition; 
CnHaOb + (n-a/4-b/2) H2O = (n/2 - a/8 + b/4)CO2 +(n/2 + a/8 – b/4) CH4 
 
In 1936, Barker proposed the oxidation of acetate to methane according to the 
following series of reactions: 
 ΔG0 
Oxidação: H3CCOOH + H2O 2CO2 + 8H 1,42 
Redução: 8H + CO2 CH4 + 2H2O -15,63 
 H3CCOOH + CO2 CH4 + CO2 - 6,67 
 
However, in 1948, Buswell and Sollo used C
14
 to prove that the methane formation 
from acetate did not come from CO2 reduction. Further on, Stadtman and Barker, 
Pine and Barker verified that methane from acetate came from decarboxylation. It is 
worthy to observe that the Söhngen hypothesis on methane formation from two 
separate mechanisms, respiration (H2 + CO2) and fermentation (acetate) was finally 
accepted. 
 
Using radiotracer, Jeris showed that 70% of the methane produced from different 
substrates derived from acetate decarboxilation. However, there were some 
uncertainties regarding the microorganism able to decarboxilate acetate, because 
these microorganisms were difficult to isolate and cultivate. 
 
In 1940, Barker published a paper on the isolation of Methanobacterium Omelianski 
that oxidized ethanol to acetate and methane. In 1950, Hungate developed 
microbiology techniques that resulted on the isolation of various so-called bacteria 
able to convert hydrogen and carbon dioxide into methane. However, no bacteria 
able to convert propionate, butyrate or higher fatty acid salts to acetate and methane 
could be isolated. Researches formulated to fundament the hypothesis of a single or 
multi-organism process were conducted. 
 
In 1967, Bryant e co-workers reported that the M. Omelianski culture contained two 
species of bacteria and not just one. One of the microorganism isolated converted 
ethanol to acetate and hydrogen and the other converted CO2 e H2 to methane. It 
became clear that the complete conversion of ethanol to methane requires the 
participation of three species: 
 
 ΔG0(kcal) 
Species1: CH3CH2OH + H2O H3CCOO
-
 + H
+
 + 2H2 1.42 
Species 2: 2H2 + ½ CO2 1/2CH4 + H2O - 15.63 
Species 3: H3CCOO
-
 + H
+
 CH4 + CO2 - 6.77 
 CH3CH2OH + H2O 3/2 CH4 + 1/2 CO2 - 20.98 
 
Bryant and co-works demonstrated the syntrophic association between 
microorganisms that form hydrogen and acetate with those that consume hydrogen 
to form methane. This association propitiates the conversion of ethanol to acetate 
and hydrogen that is thermodynamically unfavorable. Bryant and co-workers also 
demonstrated the existence of similar syntrophic association for butyrate and 
propionate oxidation. 
 
Hydrogen inter-species transfer was probably the most significant advance in 
methanogenic process control. Its minimization is still significant to obtain valuable 
fermentation products such as hydrogen gas. 
 
Development of Anaerobic Reactors for Wastewater Treatment 
 
In the 1950s, two different developments were particularly important for the 
successful applicability of sludge digesters: introduction of mechanical mixing in the 
digesters and development of the anaerobic contact process (“anaerobic activated 
sludge”). Mechanical mixing avoided scum formation and propitiated the 
development of “high-rate digesters”, as demonstrated by Morgan and Torpey. 
 
In 1950, Stander recognized the importance of keeping high concentrations of 
microorganisms in the sludge, and demonstrated the feasibility of treating effluents 
from different industries at lab scale. He started to use a sedimentation unit after the 
digester to promote the return of sludge to the reactor. Later, Stander developed the 
“Clarigester” by incorporating a settling zone in the upper part of the digester. In 
1955, Schroepfer and co-workers developed the “Contact Process” based on the 
activated sludge process. 
 
In 1964, McCarty published a series of four papers in the journal “Public Works” 
entitled “Anaerobic Waste Treatment Fundamental (parts 1, 2, 3, and4)”. Many 
concepts exposed in these papers are still used. 
 
In 1969, Youngand McCarty published paper on the conception of “Anaerobic 
Filter” (AF), an upflow fixed-film reactor to be used mainly for the treatment of 
wastewater with very low concentration of suspended solids. The importance of AF 
for Brazilian researchers was very significant because, after some pilot-scale 
experiments in 1975, full-scale AF were designed to treat soft-drink, and meat 
canning wastewater. 
 
In 1970, Lawrence and McCarty published “Unified basis for biological treatment 
design and operation” in the Journal of the Sanitary Engineering Division. In this 
paper, the relationship between the ratio food/microorganisms (F/M) and the cellular 
retention time (Θc) was explicated. The authors derived an expression applicable to 
anaerobic and aerobic systems. The expression is based on kinetic and operation 
parameters showing the effect of Θc on the reactors efficiency. 
 
In 1980, Swtzenbaun and Jewel proposed the “Anaerobic Attached-Film Expanded-
Bed” (AAFEB) to avoid problems of fixed-bed clogging, a common occurrence with 
AF applied to some types of industrial wastewater. Although the AAFB reactor was 
able to avoid clogging, the recycling rate has to be high to keep the bed expended. 
 
In 1980, Lettinga and co-works published a paper on the development and 
application of the “Up-flow Anaerobic Sludge” (UAS) reactor that incorporates a 
solid/gas/liquid (SGL) separation device at the upper part of the unit. Further, the 
USB became UASB – “Up-flow Anaerobic Sludge Blanket” reactor. The UASB 
reactor became the most important anaerobic unit used in the 1980s and 1990s, 
inclusive in Latin-America. Although some pilot-plant experiments were conducted 
In 1980, Lettinga and co-works published a paper on the development and 
application of the “Up-flow Anaerobic Sludge” (UAS) reactor that incorporates a 
solid/gas/liquid (SGL) separation device at the upper part of the unit. Further, the 
USB became UASB – “Up-flow Anaerobic Sludge Blanket” reactor. The UASB 
reactor became the most important anaerobic unit used in the 1980s and 1990s, 
inclusive in Latin-America. Although some pilot-plant experiments were conducted 
in São Paulo, Brazil, in 1986 to 1989, and some full-scale modified UASB have 
been built in Paraná, Brazil, by the state company SANEPR, the first full-scale 
UASB plant for domestic sewage treatment was constructed in Bucaramanga, 
Colombia. Full-scale UASB reactors for food processing wastewater were designed 
and constructed in Brazil in the 1980s. 
 
The knowledge accumulated on fundamental and applications of anaerobic process 
for different substrates and the evident need to keep a very active biomass inside the 
reactor propitiated the development of different reactors’ configurations such as 
ASBR (Anaerobic Sequential Batch Reactor), ARDR (Anaerobic Rotating Discs 
Reactor), ABR (Anaerobic Baffled Reactor), and (AMR) Anaerobic Membrane 
Reactor. All these configurations have been studied by Latin-American research 
groups to apply and improve their performance for the treatment of many different 
substrates, from domestic sewage to agro-industries wastewaters. Some research 
groups in Latin-America are still looking for obtaining other by-products from 
anaerobic digestion besides methane. 
 
The evolution of sanitary landfills and attempts to produce and recover biogas 
probably started in the 1980s. In many Latin-American countries, private companies 
are responsible for collection and final destination of municipal solid wastes. 
Although many investigations have been done on anaerobic treatment of municipal 
solid waste, the implementation of the solutions obtained at lab-scale has been 
difficult. However, the search for environmental sustainable solutions has improved 
the interest for the adoption of anaerobic process as the first biological treatment unit 
of a treatment plant. 
 
In São Paulo, Brazil, in 1986 to 1989, and some full-scale modified UASB have 
been built in Paraná, Brazil, by the state company SANEPR, the first full-scale 
UASB plant for domestic sewage treatment was constructed in Bucaramanga, 
Colombia. Full-scale UASB reactors for food processing wastewater were designed 
and constructed in Brazil in the 1980s. 
The knowledge accumulated on fundamental and applications of anaerobic process 
for different substrates and the evident need to keep a very active biomass inside the 
reactor propitiated the development of different reactors’ configurations such as 
ASBR (Anaerobic Sequential Batch Reactor), ARDR (Anaerobic Rotating Discs 
Reactor), ABR (Anaerobic Baffled Reactor), and (AMR) Anaerobic Membrane 
Reactor. All these configurations have been studied by Latin-American research 
groups to apply and improve their performance for the treatment of many different 
substrates, from domestic sewage to agro-industries wastewaters. Some research 
groups in Latin-America are still looking for obtaining other by-products from 
anaerobic digestion besides methane. 
 
The evolution of sanitary landfills and the attempts to produce and recover biogas 
probably started in the 1980s. In many Latin-American countries, private companies 
are responsible for collection and final destination of municipal solid wastes. 
Although many investigations have been done on anaerobic treatment of municipal 
solid waste, the implementation of the solutions obtained at lab-scale has been 
difficult. 
 
However, the search for environmental sustainable solutions has improved the 
interest for the adoption of anaerobic process as the first biological treatment unit of 
a treatment plant. 
 
References 
 
Abbasi, T., Tauseef, S. M., Abbasi (2012) – A brief history of anaerobic digestion 
and “biogas”. Biogas Energy. SpringerBriefs in Environmental Science V. 2, pp 11-
23. 
 
Bond, T., Templeton, M. R. (2011) History and future of domestic biogas plants in 
developing countries. Energy for Sustainable Development. V. 15, pp 347-354. 
 
McCarty, P.L. (1982) One hundred years of Anaerobic Digestion. In: Proceedings 
Anaerobic Digestion 1981. Hughes et al. Eds. Elsevier Biomedical Press. Pp. 3-22.