Enhancement of Methane Productivity of Anaerobic Reactors of Wasterwater

Treatment PlantsAare Kuusik, E. Loigu, O. Sokk, Argo Kuusik

Estonia

Objectives of Experiments:

Enhancement of methane productivity of existing anaerobic reactors

To get rid of inconvenient waste solids: waste glycerol and fishery residues

To resolve above problems in one process

Self-made Reactor

Self-made Reactors

Manufactored ReactorsArmfield W8

Technological Scheme of Self-made Reactor

Technological Scheme of Manufactured Reactor

Maintenance of Reactors

• Mesophilic temperature 36-39 oC, mainly 37-38 oC

• Batch type or fill and draw input-output of sludge every morning

• Before and after the input-output process the contents of the reactors were mixed

• Produced biogas was evaluated

Concentrations were measured

• Every morning: pH, H2S, NH3, CO2, O2

• Once a week: TS and VS, VFA and alkalinity

of input and output sludge

The data of the single sludge digestion was summarised

Days consi-dered

 

Reten-tion ti-

me, days

 

Volume load TS kg/m3

 

Input, g/L

 

Output, g/L

Organic removal input-output,

g/LTS VS TS VS ∆TS ∆VS

9 -21 40 0.885 35.4 26.625 22.375 14.05 13.025 12.62522 - 30 35 1.011 35.394 26.62 22.159 13.234 13.234 1338.831 – 41 30 1.088 32.644 24.169 22.331 13.819 10.313 10.3542 – 55 25 1.048 26.203 16.25        56 - 82 20 1.601 32.025 22.375 21.863 13.713 10.163 8.663

Average   1.227 31.972 22.693 22.1 13.728 11.242 10.504

Continuation of previous table (single sludge)

Retention time, days

Tempe-ratureoC

Methane yield Methane contents in biogas

%

Solid removal %

Per volume

L/m3

TS removed

L/∆kg

∆TS ∆VS

40 36,5 109.7 339.6 50.98 36.51 47.23

35 37,4 82.1 217.1 51.84 37.40 50.25

30 36,4 92.9 270.3 52.16 31.59 42.81

25 38,5 117.9   54.51    

20 37,9 171.5 337.24 57.59 31.75 38.68

Average 37.2 128 310.9 54.39 33.55 42.95

Admixed sludge (sludge 98% + 2% waste glycerol) digestion

Days consi-dered

Reten-tion time, days

Volum load, TS

kg/m3/d

Input, g/L Output, g/L Difference between input-

output, g/LTS VS TS VS ∆TS ∆VS

12 – 19 40 1.315 52.575 42.375 23.0 14.525 29.575 27.8520 – 39 35 1.458 51.034 40.994 23.166 14.328 27.869 26.66640 – 63 30 2.567 44.925 34.613 23.269 10.448 21.656 24.16964 – 75 25 2.110 52.75 41.125 30.672 17.891 22.078 23.23476 – 80 20 2.497 49.938 38.213 24.543 9.536 25.4 16.175Averag

e  2.016 49.307 38.756 24.588 13.274 24.720 24.578

Continuation previous table (sludge 98% + glycerol 2%)

Reten-tion time,

days

Tempe-rature

oC

Methane yield Methane contents

in biogas, %

Solid removal %

Per reac-tor volu-me, L/m3

Per TS removed,

L/∆kg

∆TS ∆VS

40 37 336.7 483.5 62.71 56.3 65,72

35 37 268.8 352.8 61.17 54.62 65,06

30 39.3 287.3 356.6 61.81 48.19 69,82

25 36.5 386.8 416.3 60.05 41.85 56,49

20 37.9 536.7 374.2 61.75 50.85 75,06

Average 37.8 323 381.9 61.42 50.1 66

The weighted means of experimentsSubs-trate

Days consi-dered

Retention time,days

TS input,g/L

VS input,

g/L

TS output,

g/L

VS output,

g/L

∆TS,g/L

∆VS,g/L

Sludge 100%

73 27.6 32.0

(26.2-35.4)

22.7

(16.3-26.6)

22.1

(21.9-22.4)

13.7 (13.2-14.1)

11.2

(10.2-13.2)

10.5 (8.7-13.4)

Sludge 98% + glycerol

2%

69 31.0 49.3 (44.9-52.8)

38.8 (34.6-42.4)

24.6 (23.0-30.7)

13.3 (9.5-17.9)

24.7 (21.7-29.6)

24.6 (16.2-27.9)

Sludge 95% + glycerol

5%

70 35 64.0 (58.2-77.3)

58.6

(48.8-64.1)

27.0 (23.5-32.3)

15.1

(10.8-19.0)

44.5

(34.4-53.8)

43.7

(38.0-50.7)

Sludge 98% + fish 2%

29 35.7 43.0 (40.4-46.8)

32.4 (30.2-34.8)

23.8 (21.5-24.6)

14.0

(12.8-15.0)

20.8 (18.9-22.6)

18.4 (17.4-19.9)

Continuation of weighted means tableSubstrate Methane yield Methane

contents in biogas %

Solid removal %

Per volume ,L/

m3

Per remo-ved TS, L/∆kg

∆TS ∆VS

Sludge 100%

128 (82-172) 310.9 (217-340)

54. (51-57.6) 33.6(31.6-37.4)

43(38.7-50.3)

Sludge 98% +2% glyc.

323(269-537)

381.9(338-455)

61.4(60.1-62.7)

50.1(41.9-56.3)

66(65.1-75.1)

Sludge 95% + 5% glyc.

488.6(234.9-705.3)

386.1(273.1-530.4)

59.3(57-61.6)

62(54.7-69.6)

74.3(68.1-77.9)

Sludge 98% +2% fish

369.4(328.9-419.5)

627.7(582.6-686.2)

63.5(62.4-64.9)

48.5(46.7-50.7)

56.8(55.8-57.7)

Percentage comparison of essential weighted means (in brackets)

Substrate Retention time in days

Percentage relations

TS load per reactor volume

(kg/m3)

Solids residue after

treatment(g/L)

CH4 produc.

per reactor volume, (L/m3)

Raw sludge 100%

40 - 20 100 (1,227) 100 (22.1) 100 (128)

Sludge 98%+ glycerol 2%

40 - 20 164 (2.016) 111.3(24.588) 252 (323)

Sludge 95% + 5% glycerol

40 – 20 173.1(2.124) 122.1(26.994) 382 (488.6)

Sludge 98% + fish resid. 2%

40 - 30 99 (1.215) 107.9(23.836) 288.6(369.4)

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