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et al., 2011). Therefore, it is very clear that the ITDAR possibly inhibited with the free ammonia toxicity during the trial runs 1–3 with the feed C/N ratio of 27. Table 4.1 Digestion Parameters and Methane Yield of ITDAR Run VFA (mg/L) VFA/Alk ratio pH Total Ammonia-N (mg/L) 66 Free ammonia (mg/L) Specific methane production (L/kgVS) VS loss (%) Feedstock 1 (avg. C/N ratio 27) Start-up 37857 a 1.41 6.29 1943 25 9.60 - 1 35920 1.21 6.95 2753 99 176 46.52 2 27567 0.52 7.53 3040 328 286 64.16 3 18025 0.51 7.49 2671 284 327 70.20 Feedstock 2 (avg. C/N ratio 32) 4 11725 0.31 7.75 2360 432 218 54.36 5 11417 0.35 7.35 1895 164 121 35.37 6 9625 0.39 7.50 2161 227 222 53.65 7 7469 0.39 7.29 1791 221 203 52.53 8 6010 0.56 7.34 1758 135 203 54.02 a Table gives average values for each run. In addition, the VFA/Alk ratio was also higher i.e., 1.21 during run 1 and it was around 0.5 for run 2 and 3. Very high concentration of unconsumed VFA from start-up phase carried to run 1 could be the possible reason for the higher VFA/Alk ratio during run 1. As discussed earlier, the higher VFA/Alk ratio in run 1 affected over the entire methane production rate in ITDAR. In addition to the ammonia-N concentrations, VFA/Alk ratio higher than its optimum value (i.e. ≤ 0.4) was also found to be affecting the overall methane yield while feeding the reactor with C/N ratio of 27. b) Effect of feedstock 2 (C/N ratio of 32) in ITDAR – Run 4 to 8 Feedstock 2 with the C/N ratio of 32 was used for runs 4–8 to reduce the free ammonia toxicity. Using this range of C/N ratio has been reported (Kayhanian, 1999) as a one of the best tools to mitigate ammonia-N inhibition in dry thermophilic anaerobic digesters. During trial 2 with the higher C/N ratio, the ammonia-N concentration further reduced from 2360 to 1758 mg/L (avg.) in ITDAR during different runs. The sudden change in feedstock composition (with the C/N ratio of 32) from run 3 (trial 1) with increasing OLR affected the overall reactor performance during run 4 (trial 2) as shown in Figure 4.4 (b-d). The reason was that higher C/N ratio helped system to increase alkalinity and pH value (8.00), which increased free ammonia concentration (657 mg/L) in ITDAR. The detailed explanation with data of Appendix C, Table C-1 is given here. When feeding of feedstock 2 was started, the change in alkalinity and pH was not very significant (alkalinity changed from 32000 to 35250 mg/L and pH changed from 7.59 to 7.75) as per data from day 98 to day 127 in the appendix. This duration can be regarded as acclimatization time for the new feedstock (i.e. Feedstock 2) for ITDAR being a biological system. After that, the increase in alkalinity and pH was quite significant (alkalinity changed from 35250 to 68750 mg/L and pH changed from 7.75 to 8.00) during day 127-141, which increased free ammonia from 411 to 657 mg/L and directly affected methane yield. This change in parameters by
feedstock 2 is considered as a sudden change, which is just in 14 days (from day 127 to 141), where the retention time of that run was 45 days. VFA 1000x (mg/L) Free ammonia 10x (mg/L) pH Methane yield 10x (L/kg VS) TAN 100x (mg/L) 14 12 10 8 6 4 50 40 30 20 10 0 8 7 6 805 60 40 20 0 50 40 30 20 10 0 c) b) e) d) a) 0 30 60 90 120 150 180 210 240 270 1 2 3 4 5 6 7 8 0 30 60 90 120 150 180 210 240 270 Figure 4.4 Interaction of ammonia and VFA in ITDAR 67 Time (days)
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DRY ANAEROBIC DIGESTION OF MUNICIPA
Page 3 and 4:
Abstract Global solid waste generat
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2.9 Characteristics of Digestates 3
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List of Tables Table Title Page 2.1
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4.20 Layout of conceptual decentral
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1.1 Background Chapter 1 Introducti
Page 13 and 14:
The specific objectives of this res
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scale plants of the two processes i
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acetogens play their part to run th
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In dry anaerobic digestion, recycli
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process is inhibited and at that po
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eported, which increased with time,
Page 25 and 26: acids and increased downfall of pat
Page 27 and 28: performance of a poorly mixed (1 rp
Page 29 and 30: conventional low-solid system at th
Page 31 and 32: supply of the nutrients missing in
Page 33 and 34: 2.6.2 Single-stage continuous syste
Page 35 and 36: single stage systems are DRANCO, Va
Page 37 and 38: of the solid content around 23% TS
Page 39 and 40: Substrate Feed TS (%) Reactor Type
Page 41 and 42: Second is that it has a high water
Page 43 and 44: 2.9 Characteristics of Digestates D
Page 45 and 46: For instance, Mumme et al., (2010)
Page 47 and 48: Comparison of liquid and solid dige
Page 49 and 50: 2.10 Management Aspects of Anaerobi
Page 51 and 52: Figure 2.11 Changing parameters dur
Page 53 and 54: amount of anaerobic fermentation re
Page 55 and 56: 3.1 Inoculum and Simulations of Was
Page 57 and 58: ed pump, water circulating jacket,
Page 59 and 60: the reactor was increased from 35°
Page 61 and 62: parts (wt/wt bas is) of digestate c
Page 63 and 64: Sand drying bed (SDB) is simple, ea
Page 65 and 66: 3.4.4 Estimation of GHG emissions i
Page 67 and 68: d) Calculation methods i) CH4 emiss
Page 69 and 70: Table 3.5 Analytical Methods for Va
Page 71 and 72: Biogas production 100X (NmL) Specif
Page 73 and 74: (i.e. 5.2 and 3.04 respectively, pl
Page 75: getting affected with the presence
Page 79 and 80: 8.0) at most of the above said time
Page 81 and 82: Table 4.2 Surplus Energy of ITDAR D
Page 83 and 84: VFA 100 X (mg/L) VFA/Alk ratio 200
Page 85 and 86: the VFA concentration increased to
Page 87 and 88: The increase in GPR was almost line
Page 89 and 90: Based on our results, the best oper
Page 91 and 92: Based on this property of digestate
Page 93 and 94: Table 4.5. With curing of digestate
Page 95 and 96: application (after curing) in CH 4
Page 97 and 98: digestion, etc. Moreover, mixing of
Page 99 and 100: Figure 4.20 Layout of conceptual de
Page 101 and 102: Chapter 5 Conclusions and Recommend
Page 103 and 104: 5.2 Recommendations Following are t
Page 105 and 106: References Abdullahi, Y. A., Akunna
Page 107 and 108: Cengel, Y.A. (2003). Heat Transfer
Page 109 and 110: Forster-Carneiro, T., Pérez, M., R
Page 111 and 112: Kaparaju, P., Buendia, I., Ellegaar
Page 113 and 114: Liu, C., Yuan, X., Zeng, G., Li, W.
Page 115 and 116: Paavola, T. and Rintala, J. (2008).
Page 117 and 118: Stroot, P. G., McMahon, K. D., Mack
Page 119 and 120: Zeshan, Karthikeyan, O. P. and Visv
Page 121 and 122: Fruit and vegetable Waste Closer to
Page 123 and 124: Figure A-5 Sand drying bed for dewa
Page 125 and 126: Assumptions Size of the community:
Page 127 and 128:
The flow rate of 0.569 m 3 biogas/h
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Area for 910 kg dry solids = 910 (k
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= 280 m 3 /d x 0.000717 tons/m 3 (D
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Table C-1 Operational Parameters of
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Run Time GPR % CO2 % CH4 Methane Yi
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Appendix D Data of Phase II Pilot E
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Table D-3 Characteristics of Feed a
Page 141 and 142:
Methodology Methodology for for Ene
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Q = Heat transfer rate or heat loss
Page 145:
Calculation of GHG Emission Potenti
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