1983: literature review issue || anaerobic processes

Anaerobic ProcessesAuthor(s): Kerby F. Fannin, John R. Conrad, Vipul J. Srivastava, Douglas E. Jerger and DavidP. ChynowethSource: Journal (Water Pollution Control Federation), Vol. 55, No. 6, 1983: Literature ReviewIssue (Jun., 1983), pp. 623-632Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25041937 .

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_Wastewater Treatment

ponds at Corinne, Utah, and Eudora, Kansas, were compared

with computer model simulations.18 The primary mechanism

for nitrogen removal was through sedimentation of organic

nitrogen. Soluble inorganic nitrogen was incorporated into

cellular material. Ammonia removal resulted from biological

activity rather than volatilization. Pano and Middlebrooks,17

however, concluded through a steady-state approach, that vol

atilization governed ammonia-N removal in the Corrine and

Eudora wastewater stabilization ponds.

A mathematical model was developed by Buhr and Miller19 to describe the dynamic nature of the symbiotic growth of

algae and bacteria in a high-rate wastewater treatment pond. Data obtained from a high-rate algal pond of race-track de

sign, was used for model verification. Operating parameters

(pH, dissolved oxygen, and substrate concentration) changed on a diurnal pattern and along the length of the channel,

depending on the circulation rate employed. The authors eval

uated the influence of operating conditions on algal produc

tivity.

Dennis B. George is with the Institute of Water Research,

Lubbock Christian College. Correspondence should be ad

dressed to him at LCC Institute of Water Research, 5601 W.

19th St., Lubbock, TX 79407.

REFERENCES 1. Wittmann, J. W., "Discussion of: Recommendations for regula

tory modifications: the use of waste stabilization pond systems." J. Water Pollut. Control Fed., 54, 1428 (1982).

2. Gloyna, E. F., and Tischler, L. F., "Recommendations for reg

ulatory modifications: the use of waste stabilization pond sys

tems." J. Water Pollut. Control Fed., 53, 1559 (1981). 3. Rich, L. G., "Low-Cost Treatment of Wastewater." Public

Works, 113,6, 52 (1982).

4. Rich, L. G., "Design Approach to Dual Power Aerated Lagoons." J. Environ. Eng. Div., Proc. Amer. Soc. Civil Eng., 108, 532

(1982). 5. Rich, L. G., "A Cost-Effective System for the Aerobic Stabili

zation and Disposal of Waste Activated Sludge Solids." Water

Res. (G. B.), 16, 535 (1982). 6. Rich, L. G., and Connor, B. W., "Benthal Stabilization of Waste

Activated Sludge." Water Res. (G. B.), 16, 1419 (1982).

7. Rich, L. G., "Benthal Stabilization, A Low-Cost Process for the

Stabilization of Waste Activated Sludge Solids." Water Res.

(G. B), 16, 1399(1982).

8. Hatcher, K. J., "Permitting Options and Design Procedure for

a Controlled-Discharge Wastewater Treatment Facility." Tech

nical Completion Report, ERC 06-82, Inst. of Nat. Resour. Univ.

of Georgia, Athens, Ga. in coordination with Environ. Resour.

Center, Ga. Inst. of Technol., Atlanta, Ga. (1982). 9. Connick, D. J., et al, "Evaluation of a Treatment Lagoon for

Combined Sewer Overflow." EPA-600/2-81-196, Munie. Envi

ron. Res. Lab., U.S. EPA, Cincinnati, Ohio (1982). 10. Azov, Y., and Shelef, G., "Operations of High-Rate Oxidation

Ponds: Theory and Experiments." Water Res. (G. B), 16, 1153

(1982). 11. Abeliovich, A., "Biological Equilibrium in a Wastewater Reser

voir." Water Res. (G. B), 16, 1135 (1982). 12. Azov, Y., et al, "Effect of Hard Detergents on Algae in a High

Rate-Oxidation Pond." Appl. Environ. Microbiol, 43, 491

(1982). 13. Rich, L. G., "Influence of Multicellular Configurations on Algal

Growth in Aerated Lagoons." Water Res. (G. B.), 16, 929 (1982).

14. Sheladia, V. L., et al, "Isolation of Enteroviruses from Oxidation

Pond Waters." Appl. Environ. Microbiol, 43, 971 (1982). 15. Wittman, J. W., "How Screen Mounting Affects Microscreening

Hydraulics." Water Eng. Manage., 129, 2, 13 (1982). 16. Harrelson, M. E., and Cravens, J. B., "Use of microscreens to

polish lagoon effluents." J. Water Pollut. Control Fed., 54, 36

(1982). 17. Pano, A., and Middlebrooks, E. J., "Ammonia nitrogen removal

in facultative wastewater stabilization ponds." J. Water Pollut.

Control Fed., 54, 344 (1982). 18. Ferrara, R. A., and Avci, C. B., "Nitrogen dynamics in waste

stabilization ponds." J. Water Pollut. Control. Fed., 54, 361

(1982). 19. Buhr, H. O., and Miller, S. B., "A Dynamic Model of the High

Rate Algal-Bacteria Wastewater Treatment Pond." Water Res.

(G. B.) 17, 29 (1983).

Anaerobic processes Kerby F. Fannin, John R. Conrad,

Vipul J. Srivastava, Douglas E. Jerger, David P. Chynoweth

REVIEWS The status of U. S. research and commercialization activ

ities for biomass- and waste-to-energy was reviewed by Klass.1

Budgetary considerations for major sources of U. S. funding were discussed. Sheaffer2 explained that use of agricultural wastes as feedstocks for anaerobic digestion will help solve environmental pollution problems while producing substantial

amounts of energy and fertilizer. He noted that anaerobic

digestion of 60% of the manure produced, and about 400 X 106 kg of waste whey per year could produce benefits with an annual value as high as $13 billion. Anaerobic digester designs for treating high- and low-strength wastewaters con

taining soluble organic material were reviewed by Colleran

et al.3 Emphasis was placed on the application of anaerobic

filters for treating agricultural wastes. Operational and eco

nomic data were presented for representative systems.

MICROBIOLOGY Classification and characterization. A new species of meth

anogenic bacteria (Methanothrix soehngenii, sp. nov.) was

isolated from a mesophilic wastewater digester.4 The isolate

was very similar to the filamentous bacterium, earlier iden

tified as Methanobacterium soehngenii, and referred to as

"fat rod" or "acetate organism." Several properties of this

isolate were described, including optimum growth conditions,

kinetic data, effect of antibiotics and inhibitors, and substrate

specificity. Huber et al.5 isolated and characterized a new

methanogen, Methanococcus thermolithotrophicus, from geo

thermally-heated sea sediments. One hundred thirty bacteria

isolated from a swine manure digester were predominantly

gram-positive anaerobes, which were tentatively classified into

the following genera: Peptostreptococcus, Eubacterium, Bac

teroides, Lactobacillus, Peptococcus, Clostridium, and Strep

June 1983 623



Wastewater Treatment __

toccocus?plus two unidentified groups.6 Major fermentation

products of these organisms included acetate, propionate, suc

cinate, lactate, and ethanol. Miller et al1 observed methane

production from enrichments from five out of nine human feces

specimens. Each methanogenic enrichment contained organ

isms resembling Methanobrevibacter smithii in morphologic

and immunologie characteristics. A new plate-shaped meth

anogen, Methanoplanus limicoia, was isolated from a swamp

receiving drilling wastes.8 This organism grew on H2-C02 or

formate and required acetate.

Miller and Wolin9 reported that methanogens isolated from

methane-producing human feces were morphologically, phys

iologically, and immunologically identical to Methanobrevi bacter smithii. Growth of these methanogens in media that

were extracts of CH4-negative feces suggested that the growth

of these methanogens in individuals donating these feces was

not inhibited by a lack of nutrients or by the presence of

inhibitors. A new medium was developed that improved the

growth of bacteria isolated from swine manure digesters.10 The

requirement of added digester effluent to the medium indicated that the growth requirements for these organisms were not

completely understood.

Preparation of new antisera permitted immunological anal

yses to be carried out with antibody probes against 23 strains of bacteria, including almost all genera and species of meth

anogens.11 The absence of cross-reactions between families of

methanogens was confirmed. Several properties of soluble for

mate dehydrogenase from Methanobacterium formicicum were described.12 The formate dehydrogenase was purified 71

fold with a yield of 35%. Methanobacterium thermoautotro

phicum was found to require sodium for growth and C02 reduction to methane.13 The dependence was hyperbolic with

an apparent Ks for sodium of about 1 mM. By using C02

labeling during the growth of Methanobacterium thermoau

trophicum, Stupperich and Fuch14 confirmed the autotrophic C02 assimilation pathway for this organism. One-carbon met

abolic transformations associated with cell-carbon synthesis

and methanogenesis were analyzed by carbon-labeled meth

anol or carbon dioxide incorporation studies during growth

and by cell suspensions of Methanosarcina barkeri.15 Both

isotopes were incorporated into major cellular components

during growth on H2-C02-methanol. Evidence was presented

for synthesis of a two-carbon intermediate during metabolism

of these substrates. Krzycki et al16 studied the individual and mixed metabolism of acetate and methanol to methane by

Methanosarcina barkeri. Acetate metabolism was not catab

olite repressed by methanol, and cell yields were similar during exponential growth on either substrate.

Cellulose hydrolysis. A stable cellulolytic enzyme system was produced from a heat-treated mixed culture using anaer

obic digestion.17 The enzyme system exhibited endo- and exo

gluconase, cellobiase, and xylanase activities. Over 70% of

wood (white fir) carbohydrates were solubilized during staged autohydrolysis.18 Batch digesters and continuously fed anaer

obic filters showed similar conversion efficiencies of soluble

autohydrolysis products, with approximately 26% of the wood

chemical oxygen demand (COD) converted to methane. Pop lar wood pretreatment by partial acid hydrolysis resulted in

significantly increased glucose yields from enzyme hydroly sis.19 The pretreatments were carried out in a continuous flow

reactor at temperatures ranging from 162? to 222?C, acid

concentrations ranging from 0 to 15% and treatment times

from 3.6 to 12.7 hours. The increased susceptibility to enzyme attack was mainly attributed to hemicellulose removal during

pretreatment.

Acidogenesis. The importance of volatile acids in the feed,

or their production during anaerobic digestion, was exam

ined.20 Feedstocks containing volatile acids gradually shifted

the thermodynamics of the microorganism culture toward an

environment where appropriate levels of obligate proton-re

ducing bacteria were also maintained. This created greater

digester stability during shock caused by increased volatile acids concentrations. Increasing concentrations of magnesium

acetate up to 4 000 mg/L stimulated gas production in lab

oratory-scale wastewater sludge digesters, with a maximum

stimulation achieved at a concentration of 1 000 mg/L.21 Good

gas yields were observed when the ratio of propionic and bu

tyric acids to acetic acid was less than 80:1. Gas production was inhibited at higher ratios. Schwartz and Keller22 studied

glucose conversion to acetate and acetic acid tolerance by

Clostridium thermoaceticum. Under ideal conditions, dou

bling times were 5 to 7 hours. This organism was inhibited more by free acetic acid than by either acetate ions or low pH.

Growth did not occur when the redox potential exceeded -300

and -360 mV at pH values of 6 and 7, respectively. Studies on product inhibition in the acid-forming stage of the anaer

obic digestion showed that biomass yields decreased from 16 to 8% after the glucose concentration was increased from 2.5

to 75 g/L and the dilution rate was lowered from 0.54 to

0.044/h.23 Sudden large changes in inorganic nutrient con

centrations caused reactor failure.

Methanogenesis. Semicontinuous anaerobic digestion stud

ies on cornstover gave a maximum carbon conversion effi

ciency of 78% and a first-order reaction rate constant of 0.045/

d.24 Adding Clostridium butyricum to the digester resulted in an improved reaction rate constant to 0.05 3/day. Acetate

supplement increased the first-order rate constant to 0.096/d,

indicating that methane production was not the rate-limiting step. Carbon dioxide was reduced to methane by adding CH3

S-CoM to cell extracts of Methanobacterium thermoautotro

phicum.25 Similar stimulation was effected by formaldehyde, serine, pyruvate, or CH3CH2-S-CoM. Sulfhydryl compounds

were identified as effective inhibitors of C02 reduction. Robinson and Tiedje26 investigated Michaelis-Menten ki

netic parameters for H2 consumption in rumen fluid, anaerobic

digester sludge, and lake sediment. Mass transfer limitations

across the gas-liquid interface required dilution of the rumen

fluid and anaerobic digester sludge, but not of the sediment. Tricultures of a rumen anaerobic fungus with methanogens

resulted in the formation of two each of methane and carbon

dioxide per mole of hexose during cellulose fermentation.27 Cocultures of the fungus with either Methanobacter sp. or

Methanosarcina barkeri produced 0.6 and 1.3 mole of CH4

per mole of hexose, respectively. The maximum rate of cel

lulose degradation in the triculture was faster than previously

reported for bacterial cocultures, with complete degradation

within 16 days.

Nagase and Matsuo28 investigated the interaction between

amino acid degradation and methane production in a powder

milk digester. Certain amino acids were degraded by dehy

drogenation, with methanogens acting in the role of electron

acceptor. Glycine reduced chloroform inhibition of amino acid

624 Journal WPCF, Volume 55, Number 6




metabolism, apparently by acting as an electron acceptor.

Boone29 found that addition of acetate or H2-C02 to an animal

waste digester did not change the waste conversion because

the methanogens were able to adapt and convert the added

substrates. Hydrogen addition resulted in an increase in the

acetate pool.

Methanogens were found to coexist in anaerobic lake sed

iments with sulfate reducers in the presence of sulfate.30 The

outcome of competition at any time was a function of the rate

of hydrogen production, the relative population sizes, and sul

fate availability. Differences in substrate affinities (Ks values) accounted for inhibition of methanogenesis from H2 and C02 in mixed cultures of Desulfovibrio vulgaris and Methano

brevibacter arboriphilus.31 Using Ks values for utilization of

acetate, a kinetic theory was developed for the sulfate reducer,

Desulfobacter postgatei, to out-compete the methanogen,

Methanosarcina barkeri, for acetate.32 Sulfate-reducing bac

teria were found to out-compete methanogens for hydrogen

acetate, but would not compete with methanogens for com

pounds such as methanol, trimethylamine, or methionine.33

PROCESS STABILITY

Three models were presented to describe toxic effects on

methane fermentation to aid in operational strategies and re

actor design.34 Long solids retention times were shown to re

duce toxicity problems without significantly sacrificing process

efficiency. The effect of substrate inhibition and cell recycle on the stability of methane reactors was discussed.35 Cell re

cycle increased the conversion of digester influents and enabled a linear reduction in the residence time.

A novel method was developed to prevent the formation of

hydrogen sulfide during the anaerobic digestion of high sul

fate-containing wastewaters.36 The method used a specific

microbial association that maximized methane yields in the

presence of sulfate. Varel and Hashimoto37 studied the effect

of animal wastes containing the antibiotics monensin, lasal

ocid, salinomycin, and avoparcin on anaerobic digestion. Las

alocid and salinomycin had minimal effects, but avoparcin and monensin caused initial inhibition that receded after an ac

climation period.

PROCESS OPTIMIZATION General methodology. Three types of digester gas mixing

techniques were evaluated: the draft tube, multiple sequen

tially-discharged lances, and floor-mounted diffuser boxes.38

Experiments conducted under both clean water and active

digester conditions showed that, when properly designed, each

of the systems could maintain uniform digester contents, but

that the sequential-discharge lance was more effective for con

trolling floating solids. Hashimoto39 reported that continuous

mixing of thermophilic beef waste digesters resulted in slightly higher methane production rates than mixing 2 h/d. Also, operation under a vacuum of 38-cm water resulted in a 5%

increase in the methane production rate.

Membrane fractions derived from Escherichia coli were

shown to remove oxygen efficiently from a variety of bacter

iological growth media.40 This activity was caused by an active

cytochrome electron transport system located in the cyto

plasmic membrane system. Using this membrane technique, an 02-free environment could be maintained, even if small

amounts of air were introduced. Substantial decreases in di

gester efficiency occurred when chemical coagulation was used

with wastes high in colloidal protein or lipid content.41 These decreases were attributed to the greater inaccessibility to mi

croorganisms or lower enzyme reactivity of the substrate be

cause of its close association with the metal coagulant floe.

Operation and performance data from selected anaerobic

digestion studies are shown in Table 1.

Attached film reactors. Variations in temperature, flow rate,

or concentration of synthetic wastewater produced no signif

icant shock effect in an anaerobic attached-film expanded-bed

Table 1?Operation and performance data from anaerobic digestion studies.

Feed Temp.,

?C

Loading,

kg VS/ m3-day

Retention

time,

days

Methane

yield,

m3/kg VS

added

Methane

production

rate, vol/vol

culture-day

Methane

content,

mol %

Volatile

solids

reduction, %

Refer

ence

Municipal sludge Activated (90%) + Primary (10%) 35

Municipal sludge Activated (90%) + Primary (10%) 54 Municipal primary sludge 35

Municipal solid waste 35




Milk waste 28

Pear-blanching waste 35

Pear-peelings 35

Green bean blanching waste 35

Carrot peelings 35

Swine waste 24

Swine waste 24

Swine waste 24

2.08

3.20

1.6

4.9a

3.5a

16.5a

2.7a

7.5a

0.53

0.92

1.57

17

11.3

15

0.5

6

1

5.5

2.7

6

3

2

0.21

0.26

0.52

0.17

0.12

0.12

0.11

0.75b

0.29b

0.13b

0.25b

0.25b

0.58

0.48

0.42

0.44

0.83

0.83

3.68

1.02

2.15

0.68

1.88

0.31

0.44

0.66

65

65

69

59.4

66.9

68.9

61.8

82

60

55

60

77.6

76.2

76.6

31.3

34.0

85

82c

95c

96c

96c

58.4

54.3

54.8

73

73

76

78

78

78

78

86

84

48

84

84

90

90

90

(Table 1 Continued)

June 1983 625



Wastewater Treatment

Table 1?(Continued)

Feed Temp.,

?C

Loading,

kg VS/ m3-day

Retention

time,

days

Methane

yield,

m3/kg VS

added

Methane

production

rate, vol/vol

culture-day

Methane

content,

mol %

Volatile

solids

reduction, %

Refer

ence

Swine Waste 24 3.28 1 0.25 0.82 82.8

Pig slurry supernatant 28 19.6a 3 0.29b 5.68 80-85

Beef cattle manure 55 16.2 5 0.29 4.70 56.6

Beet cattle manure (50%)

molasses (50%) 55 11.3 6 0.30 3.39 48 Beef cattle manure-straw (two

stage) 53 13.4 5 0.22 2.96 52

Silage effluent (anaerobic filter) 28 4.7a 3 0.30b 1.41 84

Water hyacinth 35 1.3 12 0.23 0.31 63.4

Water hyacinth 35 1.6 15 0.19 0.30 59

Water hyacinth/sludge 35 1.6 15 0.28 0.45 63

Water hyacinth -I- Bermuda grass + MSW-sludge blend 35 1.3 12 0.26 0.35 63

Sea kelp (USR) 35 1.6 50 0.37 0.60 55.9

Sea kelp (USR) 35 2.4 27 0.20 0.48 47.5

Sea kelp (baffle flow) 35 1.6 ? 0.37 0.60 55.7

Sea kelp (STR) 35 1.6 50 0.35 0.56 57.4

Sea kelp (STR) 35 2.4 27 0.16 0.40 48.2

Bermuda grass 35 1.3 12 0.14 0.19 61.4

Bermuda grass (nitrogen addition)

C:N/6.3:1 35 1.3 12 0.27 0.35 59.8

Bermuda grass (nitrogen addition)

C:N/12.3:1 35 1.3 12 0.21 0.27 51.8

Bermuda grass (N + P addition) 35 1.3 12 0.26 0.35 60.6

Hybrid poplar (batch) 35 0.03 60 0.32 0.10 ?

Sycamore (batch) 35 0.03 60 0.32 0.10 ?

Black alder (batch) 35 0.03 60 0.24 0.08 ?

Cottonwood (batch) 35 0.03 60 0.22 0.07 ?

Eucalyptus (batch) 35 0.03 60 0.014 <0.01 ?

Loblolly pine (batch) 35 0.03 60 0.063 0.02 ?

Poultry manure 35 1.60 70 0.19 0.31 54

Poultry manure 35 2.21 70 0.21 0.45 54

Poultry manure 35 3.18 70 0.17 0.52 54

Poultry manure 35 2.71 25 0.25 0.65 54

Poultry manure 35 3.12 25 0.22 0.69 54

Poultry manure 35 3.05 15 0.33 1.00 54

Poultry manure 35 3.77 15 0.32 1.19 54

Poultry manure 35 4.38 15 0.29 1.25 54

Poultry manure 35 2.72 10 0.28 0.75 54

Poultry manure 35 3.81 10 0.34 1.30 54

Poultry manure 35 4.60 10 0.37 1.68 54

Poultry manure 35 1.95 50 0.27 0.53 62.2

Marine algae

Tetraselmis (air dried) 35 1.0 20 0.21 0.21 ?



Tetraselmis (air dried, two step

methanation) 20/35 1.95 14 0.21 0.41 ?


methanation) 20/35 4.05 14 0.19 0.77 ?


methanation) 20/35 3.95 14 0.19 0.75 ?

Tetraselmis (fresh) 35 1.0 20 0.33 0.33 ?

Porphyredium cruentum 35 1.0 20 0.22 0.22 ?

Laminaria sacchanna 35 1.0 20 0.25 0.25 ?

Freshwater algae

Hydrodictyon 35 0.9-11.36 1.6 0.22 0.20-2.50 ?

Scenedesmus acutus 35 1.0 20 0.20 0.20 ?

Hydrodictyon reticulatum 35 0.9 20 0.26 0.47 ?

46.1

88c

53

68

41

84c

49.7

44

58

34

20

37.5

33.7

38.1

54

57

33

32

<1

4

27

48

37

45

36

42

37

37

72

45

40

90

86

87

93

60

86

57

76

76

57

98

98

98

98

98

57

57

57

57

99

99

99

99

99

99

92

92

92

92

92

92

92

92

92

92

92

91

96

96

96

96

96

96

96

96

96

96

96

96

a Loading as kg COD/m3-day.

b Methane yield as m3/kg COD added.

c COD reduced.




Wastewater Treatment

reactor.42 This high degree of stability was attributed to ex

ceptionally high bacterial cell concentrations in the reactor and to a microorganism retention time in excess of 1 year. A

down-flow fixed-film reactor, operating on chemical industry

wastes, received eight times the normal loading rate for a 24

hour period, but recovered within 12 to 48 hours after over

loading was stopped.43 Decreasing the temperature from 35?

to 10?C had an insignificant effect on COD removal efficiency when the loading rate was reduced simultaneously from 16.3

to 4.1 kg VS/m3-d. A unified model of biofilm reactor kinetics was developed

and applied to steady-state conditions for completely mixed,

fixed-bed, and fluidized-bed reactors with and without recy

cle.44 The results demonstrated that interactions among uti

lization kinetics, biofilm growth, and reactor configuration

determined the performance, instead of just simple loading factors and kinetic relationships. The model predicted that a fluidized-bed reactor could achieve performance superior to

a completely mixed and fixed-bed reactor because the biofilm is evenly distributed throughout the reactor, while the liquid remains a plug flow. A mathematical model was used for pre

dicting the effluent concentrations from a fluidized bed reactor as a function of operating conditions.45 Unlike previous models,

the biomass particle size was not a required input parameter,

but was predicted as a consequence of the process by which

the fermenter reached steady state.

Factors limiting the biomethanogenesis process were deter

mined to be the low specific growth rate of methanogenic bacteria, the liquefaction of insoluble organic matter, and the

limitation of simple analytical methods for monitoring the

process.46 The use of an attached film reactor in two-stage

digestion was recommended to overcome these limitations.

Dahab and Young47 identified media type, pore size, and

shape as important factors in designing full-scale anaerobic

filters. Most COD removal was associated with the biological solids within the interstitial spaces in the lower third of the reactor height. Higher loading and methane production rates

were achieved by operating a stationary fixed-film reactor with

intermittent, rather than continuous feedings with bean

blanching or pear-peeling wastes.48 The biofilm thickness on

any surface depended on the substrate concentration, the fluid

shear because of the flow, and the loading rate.49 Substrate

removal depended on the active biofilm thickness and the depth of substrate penetration in the biofilm.

Sludge bed reactors. Upflow sludge-bed reactors Were able to operate at higher loading rates (up to 30 kg COD/m3 d)

with higher methane production rates (6 to 9 m3/m3 d) than fixed-film reactors.50 Fixed-film reactors were, however, more

resistant to temperature- or loading-induced shocks and re

covered more rapidly than upflow sludge-bed reactors. An

aerobic filter and sludge blanket reactors, operated at 35? and

50?C, were evaluated for treating thermally-conditioned

sludge decant liquors from a wastewater treatment plant.51 Little performance difference between the two reactor designs was noted, except for greater solids losses from the sludge

blanket reactor. The use of anaerobic digestion in combination

with heat pumps was estimated to provide a 25% savings in

energy cost in treating this waste.

Sludge with good settling properties was the preferred in oculum for starting upflow sludge blanket reactors.52 A stable

thermophilic population was obtained within 5 weeks, but

rapid increases in the loading rate caused an increase in pro

pionic acid concentrations. Zoetemeyer et al53 investigated

anaerobic acidification of wastewater from a sugar refinery

containing principally sucrose, lactate, and ethanol in a 1-m3

upflow reactor operated at 29?C and at residence times of 7.2

to 1 h. Sucrose was metabolized at all residence times and

lactate at long residence times. Ethanol was not converted. An

upflow sludge blanket reactor was described for treating ac

etate-rich wastes.54 Optimal gas production and a COD re

duction of 70% was achieved at an organic loading rate of 1.6

kg biochemical oxygen demand (BOD)/m3?d at a hydraulic retention time of under 10 h.

Using tracer studies, the residence times and distribution

of fluids were determined in a 30-m3 pilot plant and in a 200 m3 prototype upflow reactor used to treat beet sugar waste

water.55 Using residence time distribution curves to develop model descriptions of the fluid flow patterns, a sludge-bed height of 1.5 to 2.5 m was recommended. Van de Meer and

De Vletter56 presented a detailed discussion of the theory and

practice of using gas-liquid sludge separators in the upflow anaerobic sludge blanket digester. Methods for evaluating their performance were discussed.

Two-phase reactors. Using high COD industrial wastes, a

two-phase digestion process performed better than a conven

tional anaerobic digestion process.57 Higher loading rates and

shorter hydraulic retention times were reported to improve waste stabilization and net energy recovery efficiencies. A two

phase anaerobic digestion process was developed using a ver

tical hydrolysis redox state, a horizontal methane phase and

a controlled pore-size ceramic media for attachment of bac

teria.58 The reactors were operated on dilute wastewater (COD

of 800 to 2 000 mg/L) at temperatures of 20?, 30?, and 40?C, and residence times of 2.0 to 5.5 h. The resulting gas contained

greater than 90% methane and volatile solids reductions of 80 to 90% were observed.

A packed-bed reactor was studied as a methane phase di

gester in a two-phase digestion system.59 Using effluents from

an acid-phase digester receiving participate substrates, a

methane yield of 0.23 m3/kg COD was observed at a loading rate of 1.9 kg COD/m3?d and a 2.3-d hydraulic retention time. The effluent from an acid-phase digester of soluble feeds exhibited a methane yield of 0.41 m3/kg COD at a loading rate of 6.1 kg VS/m3 d and a hydraulic retention time of 5.2 d in the methane phase. A two-stage process was studied for

biogasification of a mixture containing a 1:1 ratio of cattle

manure and straw.60 The first stage was mixed, had a 1-d

residence time, and was autoheated from 40? to 60?C. The effluent from this first stage was subsequently transferred into a second-stage stirred tank reactor and maintained at 54?C.

With an overall retention time of 5 d, this process resulted in a methane yield of 0.22 m3/kg VS-added and a VS reduction of 41%.

Other reactors. Using food and drink industry wastes as a

feedstock, the performances of several anaerobic digestion

processes were compared.61 The anaerobic contact process had

a higher COD removal efficiency, 83 to 96%, and was more stable during changes in operating conditions than other pro

cesses. Thermophilic anaerobic digestion experiments at 49?C

conducted in a full-scale 170 000-m3 digester showed stability similar to that of mesophilic digestion when the temperature

was controlled within 0.8?C.62 It was suggested that digester

operation at 54? to 60?C was possible if temperature was

closely controlled.

Ethanol fermentation. The feasibility of commercial ethanol

production was dependent on the ratio of combustible energy

June 1983 627



Wastewater Treatment_

obtained from product to energy necessary for its production.63

To reduce the cost of separating ethanol from water, several

polysaccharide-type materials were used and found capable

of adsorbing water from water-ethanol mixtures. Starchy ma

terials such as potato and corn were most effective. Attached

film reactors with glass-fiber support media for Zymomonas

mobilis cells were operated for ethanol production from a glu

cose-yeast extract solution.64 The maximum effluent ethanol

concentration of 6.4% and the maximum volumetric produc

tivity of 152 g/L'h were attained at a hydraulic retention time of 10 to 15 min after about 28 d of continuous operation.

An attached-film reactor with ceramic support medium for

Acetobacter cells was used to study the production of acetic

acid from ethanol.65 The age of alginate-entrapped Saccha

romyces cerevisiae cells was shown to be one of the critical

factors that influenced efficient fermentation of glucose to

ethanol.66 Yeast cells that were 96-h old were substantially

superior to 24- to 72-h old cells in ability to produce maximum

yields of ethanol over an extended period of time. Wheat straw, thermally-treated at 170?C for 30 to 60 min

at a water-to-solids ratio of 7:1, yielded a cellulosic pulp of

70 to 82%, while a sodium hydroxide extraction yielded a 60% cellulosic pulp and a hemicellulose fraction.67 The fermenta

tion of cellulosic and hemicellulosic hydrosolate to ethanol by Saccharomyces evarum and Pochysolen tamophilus showed

efficiencies ranging from 40 to 60%, indicating that inhibitory substances were produced during pretreatment.

ENERGY AND ECONOMIC ASSESSMENT

Martin and Loehr48 estimated the capital investment levels

needed for biogas production and use that appeared justified by anticipated returns. These estimates helped with assessing

specific systems and evaluating levels of governmental assis

tance needed to encourage implementation of this technology. Studies by Chassin69 showed that use of crop residues for en

ergy may increase the instability of farm production systems

by changing the soil fertility and the socio-economic equilibria chiefly in marginalized areas.

Crawford70 evaluated the economics of using a packed bed

anaerobic digester for treating conditioning liquors from a

thermal treatment facility handling 1 400 m3/d of sludge pro duced by a 2.1 m3/d wastewater treatment plant. The total

capital and operating costs were reported to be $450 000 and $50 000/yr, respectively, and the annual value of the gas pro

duced was estimated to be $60 000. Using recommended de

sign and operating parameters, such as a loading rate of 4 kg

VS/m3'd, temperature of 30? to 35?C, and a retention time

of 15 d, swine manure digester energy and investment re

quirements were reported.71 The digesters could supply 100%

of electrical requirement and 93% of thermal requirement of the building and the digester investment could be amortized in 12 years with a 10% return on the investment. Digester

designs and economic returns on investments for using an

aerobic digestion for potato-processing wastes were provided

by Jackson.72

PROCESS APPLICATION

Municipal wastewater. A full-scale 8 900-m3 thermophilic

digester was operated on a mixture of 90% activated sludge

and 10% primary sludge at 54?C with about an 11.3-d reten

tion time.73 Effluent quality was comparable to that obtained

from mesophilic digestion, but the methane yield and pro duction rate (0.26 m3/kg VS added and 0.83 m3/m3-d, re

spectively) were higher than those obtained from a mesophilic digester (0.21 m3/kg VS added and 0.44 m3/m3*d, respec

tively). The increased energy requirement, 120% over meso

philic, was believed to be compensated by increased gas pro

duction.

An anaerobic attached-film expanded-bed reactor was op

erated on synthetic wastewater to determine its applicability to convert organic particulate matter to gases.74 Results in

dicated that approximately 75% of feed COD was converted to gas at loading rates up to 7.3 kg VS/m3?d. A combined anaerobic-aerobic treatment process, the ANAMET system,

was described for treating various kinds of concentrated waste

water.75 Improved loading rates to the anaerobic stage, better

understanding of the food-to-mass ratio and nutrient demands,

and removal of difficult-to-degrade COD were cited as areas

needing improvement. Baseline anaerobic digestion studies

conducted with water hyacinth, primary sludge, and a blend

(3:1 dry wt) of water hyacinth and sludge exhibited methane

yields of 44, 82, and 57%, respectively, of theoretical yields calculated from feed analyses.76 The experimental methane

yield from sludge, 0.52 m3/kg VS-added, was one of the high est published values.

Municipal solid wastes. Gas production was substantially

higher in controlled than in non-controlled landfills.77 In a

controlled landfill, about 50% of the biodegradable municipal solid wastes (MSW) was degraded in 3 months. Methane yield

was 0.14 m3/kg dry MSW. Parameters that affected gas yield and production rate were moisture content, pH, bacterial pop

ulation, nutrients, and material distribution of the MSW. The bulk density or compaction increased the methane production

rate, but not the yield. Refuse derived fuel (RDF) was taken from four places using different material-separation and par

ticle-size reduction techniques.78 Batch digestion showed the

lowest methane yield for a feed subjected to acid treatment to reduce particle size. This low yield was attributed to loss

of biodegradable matter by hydrolysis. Process wastes. Food processing wastes with 5 500 to 25 000

mg/L VS were treated readily in a downflow fixed-film reactor

with a surface-area-to-volume ratio of about 150 m2/m3.79 The

methane yield at 35?C was about 0.25 to 0.30 m3/kg VS-added and treatment efficiency was 60 to 75%. Whey was anaero

bically digested in an attached film expanded-bed reactor op

erated at 35?C with 13.8- to 16.4-h hydraulic retention time.

COD reductions of 61 to 92% were achieved at loading rates of 8.2 to 22 kg/m3?d.80 An energy balance of the system suggested that about 46% of the energy needs of a cheese

production plant would be recovered from the methane pro

duced during anaerobic digestion. Szendrey et al}1 treated rum distillery wastes in a 13 250 m3 downflow attached-film reactor containing almost 10 000 m3 of a plastic packing me

dia, with a surface area of about 109 ha. The operating costs,

in terms of fuel gas, were estimated to be under $1.90/mil kJ

produced.

Sludge accumulation in an anaerobic lagoon-filter system

after 793 days was 7.76% of the VSS input.82 The decay rates

for sludge and sludge accumulation rate doubled when tem

perature increased from 10? to 20?C. Operational data de

veloped at the laboratory scale with potato processing waste

water were used to design and construct a 50-m by 104-m by





7-m prototype digester.83 The digester was constructed as a

lined, earthen basin covered by a membrane for gas collection

and odor control. Design COD removals averaged about 71%,

but problems in making the cover gas-tight prevented acqui

sition of reliable gas production data.

The feasibility of using anaerobic digestion for stabilizing green-vegetable cannery wastes was demonstrated at the lab

oratory and pilot scale.84 COD removal efficiencies ranged

from 90 to 98% and methane yields varied from 0.25 to 0.3

m3/kg of incoming COD. An anaerobic fluidized bed reactor was used to treat moderate-strength lactic casein whey per

meate.85 Removal efficiencies decreased with increased organic

loading rates, but removal rates per unit mass of microorgan isms increased with increased organic loading rates. Nutrient

requirements were much lower than for stirred-tank reactor

systems, so supplemental nitrogen and phosphorus were not

required. The fluidized bed reactors operated with volatile acids concentrations between 1 000 and 2 000 mg/L and main tained a pH of 6.9 to 8.3.

Agricultural wastes. Colleran et al.*6 investigated anaerobic

filter treatment of pig slurry, milk wastes, and silage effluent, and two-phase digestion of straw, treated (NaOH) straw, and

grass. COD reductions of 80 to 88% were achieved with soluble wastes at retention times ranging from 0.5 to 3 d.

Using laboratory-scale fermentors receiving cattle wastes,

the maximum loading rates achieved with an unstressed di

gester were 7 kg VS/m3-d at 35?C and 20 kg VS/m3-d at 55?C.87 The highest methane production rate (6.11 m3/m3*

d) was achieved at 55?C with a 4-d retention time.An ultimate

methane yield of 0.42 m3/kg VS-added was obtained in batch fermentation.

A dairy cattle waste-fed 283-m3 digester was constructed

and operated on the basis of kinetic data obtained from lab

oratory batch reactors. It was expected to produce 21.6 X 1011

J/yr of energy at a 12% rate of return.88 Anaerobic biofiltra

tion of dilute piggery wastes was shown to remove 70 to 90%

of COD with a methane yield of 0.16 m3/kg COD removed at loading rates of 2.5 to 4.0 kg COD/m3*d and a hydraulic retention time of 1 d.89 A kinetic model for COD removal was

presented. Dilute swine wastes were effectively treated by an

anaerobic filter shown to be comparable to mesophilic, high

rate digesters in terms of methane production and solids re

duction.90 A 50% VS reduction and a methane yield of 0.45 and 0.62 m3/kg VS destroyed was observed at retention times between 1 and 2 d and loading rates ranging from 4 Kg VS/ m3*d and 2 kg VS/m3*d. The filter responded rapidly to

changes in loading rates and retention times.

A 96.7-m3 digester receiving diluted (11.4%-TS) poultry manure produced 92% of gas expected at a loading rate of

1.95 kg VS/m3?d.91 Approximately 37% of the gross energy output was needed for heating, mixing, and pumping. Another

study of a poultry manure-fed digester demonstrated a max

imum gas production rate of 3.1 m3/m3-d at a loading rate

of 4.6 kg VS/m3'd and a retention time 10 d.92 An energy analysis showed that the power consumption would be at least

25% of the gas produced at a loading rate of 4.4 kg VS/m3 d. Hashimoto93 found that at similar hydraulic retention times

and volatile-solids loading rates, thermophilic digesters re

ceiving 50:50, 75:50, and 100:0 mixtures of manure and mo

lasses produced the highest, most central, and lowest methane

production rates, respectively. The higher rates were caused

by higher biodegradability of the feed content. Addition of

molasses to manure resulted in decreases in the ratio of am

monia to total nitrogen in the effluent.

The potential role of methane production from dry agri

cultural residues was hypothesized for both small- and large scale bioconversion facilities.94 Experimental data indicated

that methane production became limited at 32% solids con

centrations, while hydrolysis continued until the solids con

centration reached approximately 60%. Batch conversion ef

ficiencies of 90% of the biodegradable matter were achieved at an initial solids concentration of 28% in 200 d. System feasibility and economics data were presented.

Energy crops. Samson and LeDuy95 evaluated mesophilic

anaerobic digestion of the alga Spirulina in a semi-continuous

feed, stirred-tank reactor. A two-step anaerobic digestion, a

first percolating step for liquefaction followed by an upflow methane digester, was found suitable for algae conversion to

methane.96 The effect of temperature and loading on first stage was found to have no effect on overall methane formation.

Biomethanation of six algal species showed methane yield in the range of 0.2 to 0.33 m3/kg VS-added. A summary of the

development of prototype units for the production of methane from energy crops and farm wastes was presented by Stafford

et al.91 A number of digester designs were evaluated for in

stallation problems, digester performance, and cost effective

ness. During the study of anaerobic digestion of sea kelp, Fan

nin et al.9% found that an upflow solids reactor and a baffle

flow reactor had higher methane yields, 0.37 m3/kg VS-added, with greater process stability than conventional stirred-tank

reactors. Jerger et al.99 demonstrated that methane yields of

nearly 0.31 m3/kg VS-added could be achieved for hybrid poplar in anaerobic digestion. Their studies, using several

woody species were performed in both semicontinuously- and

batch-fed digesters and showed that long solids retention times were needed for effective degradation of high lignin-containing feeds.

The authors are with the Institute of Gas Technology, Chi

cago, III. Correspondence should be addressed to Kerby F.

F annin, Institute of Gas Technology, 3424 S. State St., HT

Center, Chicago, IL 60616.

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And Wastes." Ann Arbor Sei. Publ., Inc., Ann Arbor, Mich.,

D. L. Klass and G. H. Emert, (Eds.), 185 (1981).

79. Stevens, T. G., and Van Den Berg, L., "Anaerobic Treatment Of

Food Processing Wastes Using A Fixed-Film Reactor." Proc.

36th Ind. Waste Conf. Purdue Univ., Ann Arbor Sei. Publ., Inc.,

Ann Arbor, Mich., 224 (1982).

80. Switzenbaum, M. S., and Danskin, S. C, "Anaerobic Expanded Bed Treatment Of Whey." Proc. 36th Ind. Waste Conf. Purdue

Univ., Ann Arbor Sei. Publ., Inc., Ann Arbor Mich., 414 (1982).

81. Szendrey, L. M., et al, "Pollution And Energy Management'

Through The Anaerobic Approach." Ind. Wastes, 5, 31 (1982).

82. Brown, G. J., et al, "Sludge Accumulation In An Anaerobic

Lagoon-Anaerobic Filter System Treating Potato Processing Wastewater." Proc. 35th Ind. Waste Conf. Purdue Univ., Ann

Arbor Sei. Publ., Inc., Ann Arbor, Mich. (1981).

83. Landine, R. C, et al, "Anaerobic Pretreatment Of Potato Pro

cessing Wastewater-A Case History." Proc. 36th Ind. Waste

Conf. Purdue Univ., Ann Arbor Sei. Publ., Inc., Ann Arbor Mich.

233(1982). 84. Chamberlhac, B., et al, "Stabilization And Methane Production

by Commercial Scale Digestion Of Green Vegetable Cannery

Wastes." In: "Symposium Papers: Energy From Biomass And

Wastes VI." D. L. Klass (Ed.), Inst. of Gas Technol., Chicago,

111., 483(1982).

85. Boening, P. H., and Larsen, V. F., "Anaerobic Fluidized Bed

Whey Treatment." Biotechnol. Bioeng., 24, 2539 (1982).

86. Colleran, E., et al, "The Application Of the Anaerobic Filter

Design To Biogas Production From Solid And Liquid Agricul tural Wastes." In: "Symposium Papers: Energy From Biomass

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87. Hashimoto, A. G., "Methane From Cattle Waste: Effects Of

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24,2039(1982). 88. Kebanli, E. S., et al, "Fuel Gas From Dairy Farm Waste." Agrie

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89. Oleskiewicz, J. A., and Koziarski, S., "Low temperature anaer

obic biofiltration in upflow reactors." J. Water Pollut. Control

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90. Brumm, T. J., and Nye, J. C, "Dilute Swine Waste Treatment

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Univ., Ann Arbor Sei. Publ., Inc., Ann Arbor, Mich. 453 (1982).

91. Converse, J. C, et al, "Methane Production From Large-Scale

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92. Morrison, S. R., et al, "Biogas From Poultry Manure: Volatile

Solids Loading Rate And Hydraulic Detention Time." Proc 4th

Inter. Symp. Livestock Wastes, Amarillo, Tex., 96 (1980). 93. Hashimoto, A. G., "Methane Production And Effluent Quality

From Fermentation Of Beef Cattle Manure And Molasses." Bio

technol Bioeng. Symp., 11, 481 (1981).

94. Jewell, W. J., et al, "Dry Anaerobic Methane Fermentation."

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Digestion of Spirulina maxima Algal Biomass." Biotechnol.

Bioeng., 24, 1919 (1982).

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And Energy Crops." Energy From Biomass, 1, 104 (1981).

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Denitrification T. B. S. Prakasam

Knowles1 published a concise review on denitrification in

soil, water, and wastewater treatment ecosystems. He also

discussed the microbiological, biochemical, and global impli cations of this phenomenon. In a recently published book by the American Society for Agronomy, various authors contrib

uted chapters on different concepts related to denitrification in soil, such as microbiology and biochemistry,2 current state

of-art of the methodology used in investigating the mechanism of denitrification,3 and modeling.4 Mariatti et al5 discussed the principles involved in the experimental determination of

nitrogen isotope fractions and how this technique could be used to study the processes of nitrification and denitrification..

Horsley6 developed a technique for the enumeration of het

erotrophic denitrifiers in which colonies developed on an agar medium were picked and tested for their ability to reduce nitrate in broth media. This technique was able to distinguish bacteria that reduced nitrate to nitrite only, and also those

that reduced nitrate beyond nitrite. In contrast to this, a mi

crotiter most probable number procedure was also reported

for the enumeration of denitrifying and nitrate-reducing bac

teria.7

Denitrifiers were enumerated in soils irrigated with second

ary effluents in Perth, Australia.8 These were in the range of

0.73 to 13.5 X 104/g of soil. The enumeration of denitrifiers and aerobic heterotrophs in a polluted river revealed that their

ratio was greater than 0.01, which was higher than that found

usually in a eutrophic lake.9

A heterotrophic nitrifier belonging to the genus Alcaligenes isolated from soil was reported to actively denitrify oxidized

nitrogen.10 Also, some strains of Rhizobium were shown to be

active denitrifiers under appropriate environmental condi

tions.11

Vossoughi et aln reported that denitrification of a synthetic wastewater was achieved by a mixed culture of bacteria im

mobilized in a fluidized-bed reactor and also by cells of Pseu

domonas aeruginosa immobilized in a fixed-bed reactor. With

methanol as the carbon source, the fluidized-bed reactor re

duced NO3-N at the rate of 560 mg/L h of empty reactor volume with a retention time of less than 3 minutes. In con

trast, the fixed-bed reactor reduced NO3-N at 50 mg/L*h of

empty reactor volume. However, it had a denitrification po

tential to reduce N03-N by 140 mg/L*h. In another study, Pseudomonas denitrificans cells immobilized in alginate were used to remove nitrate and nitrite from waters containing high concentrations of these ions.13

Several strains of the autotrophic denitrifier Thiobacillus

denitrificans were used to achieve nitrogen removal from an

inorganic industrial wastewater.14 In this study, design param

eters for suspended growth and attached growth sand column

reactors were optimized. Optimum denitrification rates were

obtained at a pH of 8 and temperature of 30?C. These were

34.43 and 73.34 mg N03-N/L-h for the suspended and at tached growth reactors, at detention times of 43 and 23.5 h,

respectively.

WATER AND SOIL SYSTEMS

Ventullo and Rowe15 reported that the denitrification rate

of the epilithic microbial communities residing in a free-flow

ing water environment was dependent on temperature and the

availability of organic carbon. They obtained a maximum de

nitrification rate of 8.53 mg N02-N/cm2-d at 23?C. Studies

conducted with water obtained from Balgives Loch, a eu

trophic lake located in Eastern Scotland, indicated that the annual denitrification rate in this lake was 151 kg N/ha.16

Naqvi et al.11 reported that the denitrification rate of the Arabian sea water was ?3.2 X 1012 g/yr, which according to the authors amounted to 5% of the denitrification occurring on a global basis. In another study, the denitrification rate of

an estuarine sediment was reported to decrease exponentially with depth, and it varied between 1.4 X 10"3 to 1.4 X 10"6

mg/g h within a range of about 1 to 8 cm of sediment depth.18 In a related study, the denitrification rate of an estaurine sed

iment-water system was measured, and it was reported that

27 to 57% of the N03~ added to the system was lost because of denitrification.19 George and Antoine20 studied the denitri fication potential of soil obtained from a salt marsh and re

ported that denitrification was completely inhibited at an N02 N concentration of 200 mg/L. This inhibition was reversed, however, in the presence of NO3-N. In an investigation of the

effect of pesticides on the denitrifying activity of a salt marsh

sediment, it was reported that six of the seven pesticides tested

did not inhibit denitrification potential at a concentration of 10 mg/L.21 At this concentration Dalpon was the only pes

ticide that reduced the denitrifying activity of this sediment

by about 88% after about 72 h of incubation. Denitrification as a unit process was used to remove nitrogen

from water, so that the denitrified water could be reused in

pisciculture systems. An expanded-bed nitrifying biofilter and a preozonation-activated carbon denitrification unit were used




1983: literature review issue || anaerobic processes

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