analysis of a pilot-scale anaerobic baffled reactor treating domestic ...

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The calculated pH value is compared to the median of all measured values on samples drawn from the last compartment of the pilot-scale ABR. It is significant that the pH values are similar. The measured value is slightly higher than the simulated value, but even the small difference observed is not unexpected since evolution of CO2 from samples that are exposed to the atmosphere after sampling and before measurement is expected, and widely reported as a source of error in pH measurement in closed systems (Stumm and Morgan, 1996; Sötemann et al., 2005). These results indicate that a final digester pH value close to 6.0 is to be expected from digestion of domestic wastewater with characteristics described by Table 6.3. Alk FSA pH 307 mgCOD/ℓ 301 mgCOD/ℓ 50 mgN/ℓ 46 mgN/ℓ 5.94 6.05 calculated measured 0 50 100 Calculated value as a fraction of measured value (%) Figure 6.4: Steady-state model predictions of outlet characteristics alkalinity, free and saline ammonia (NH3+NH4 + ) and pH value compared to average or median values obtained from Phase IV operation. Calculated outflow stream characteristics 350 300 250 200 150 100 Alkalinity mgCaCO 3/ℓ COD mgCOD/ℓ 50 0 FSA mgN/ℓ 0.5 0.7 0.9 1.1 Influent COD concentration [gCOD/ℓ] (a) (b) Figure 6.5: Steady-state model predictions of outlet characteristics (a) Alkalinity, outflow/accumulating COD, free and saline ammonia and (b) PCO2 and pH value for increasing influent wastewater strength Figure 6.5 shows the results of simulations estimating the effect of increasing influent wastewater strength at the same extent of treatment (e.g. for 80% of SBCOD removed, fE = 0.80) on conditions in the digester. Higher feed concentrations result in more digestion occurring, resulting in increased 150 Partial pressure of CO2 in biogas PCO2 [mol frac.] 0.484 0.480 0.476 0.472 0.468 0.464 P CO2 pH 5.98 5.97 5.96 5.95 5.94 5.93 0.5 0.7 0.9 1.1 Influent COD concentration [gCOD/ℓ] pH value in outflow stream
amounts of free and saline ammonia, and therefore alkalinity being generated. For the wastewater composition, it can be seen that increasing the wastewater strength increases PCO2 and pH values in the digester. Sensitivity analyses were performed in which the effect of changes in feed conditions from the base case described in Table 6.3 on digester pH was investigated. It was found that pH values were most sensitive to changes in feed alkalinity, and to a lesser extent, to feed composition in terms of the ratio of carbohydrate, lipid and protein components. Digester pH values were not sensitive to feed pH values. Digester pH value 7.2 6.8 6.4 6 5.6 0.5 0.7 0.9 1.1 Figure 6.6: Steady-state model sensitivity analysis: Estimated effect of influent alkalinity concentration and COD concentration on digester pH values for fixed wastewater composition (but varying strength). Digester pH value 6.10 6.05 6.00 5.95 Influent COD concentration [gCOD/ℓ] 5.90 0.5 0.7 0.9 1.1 Influent COD concentration [gCOD/ℓ] Figure 6.7: Steady-state model sensitivity analysis: Estimated effect of ratio of carbohydrate (C), lipid (L) and protein (P) and COD concentration on digester pH values for fixed feed alkalinity. Figure 6.6 shows the relationship between feed strength and pH at a range of influent alkalinity concentrations (from 200 mgCaCO3/ℓ to 5 000 mgCaCO3/ℓ). This analysis predicts that increasing 151 5 000 mgCaCO3/ℓ 3 500 mgCaCO3/ℓ 2 000 mgCaCO3/ℓ 1 500 mgCaCO3/ℓ 1 000 mgCaCO 3/ℓ 500 mgCaCO 3/ℓ 300 mgCaCO3/ℓ 200 mgCaCO3/ℓ C:L:P ratio in feed 17:33:50 33:17:50 33:33:33 25:50:25 33:50:17 25:25:50 17:50:33 50:17:33 50:25:25
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ANALYSIS OF A PILOT-SCALE ANAEROBIC
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i DECLARATIONS I, Katherine Maria F
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My deepest thanks must be extended
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vii TABLE OF CONTENTS ANALYSIS OF A
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5.3 Feed characteristics and loadin
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xi LIST OF TABLES Table 1.1: List o
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xiii LIST OF FIGURES Figure 1.1: Gr
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Figure 5.1 Installation of the ABR
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Figure 6.8: WEST® representation o
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xix LIST OF ABBREVIATIONS A-HRT App
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1 1 INTRODUCTION The work presented
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obtained from anaerobic systems rel
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• Lalbahadur (MTech, 2005) perfor
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1.7 ORGANISATION OF THE THESIS This
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9 2 LITERATURE REVIEW A detailed re
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• Disintegration of composite par
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Homoacetogens are one of the most v
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Most of the control in anaerobic di
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therefore the sensitivity of the ov
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∆Gº (W) [kcal] -10 -8 -6 -4 -2 L
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For systems with low potential for
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design of the digester in which the
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2.2.2 Expanded granular sludge bed
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fact that for most non-ideal flow s
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hydrolysis steps to convert them to
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from the clarified zone between the
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Table 2.4: Typical pathogen surviva
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Table 2.5: Studies using anaerobic
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• There is no requirement for bio
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Kennedy and Barriault (2005) perfor
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methanogenic (Akunna and Clark, 200
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and 6 h with no significant differe
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2.5.1.12 Granule formation in ABRs
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• A baffled reactor is described
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2.5.3.4 Scanning electron microscop
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spacing on flow patterns in a singl
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Figure 3.5: Orthographic projection
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PLC calculated the fraction of that
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epresent buulk conditionns. Compart
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The rreactor was initially commmiss
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Phase I Phase II Phase III Phase IV
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Table 4.1: Characteristics of degri
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Table 4.2: Pilot-scale ABR approxim
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COD [mgCOD/ℓ] 2000 1800 1600 1400
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4.3.5 Phosphorus Figure 4.8 present
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Observation of sludge in compartmen
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Another interesting observation is
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4.4.3 pH pH measurements were perfo
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esult in low pH values. The reasons
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4.5 SUMMARY: PHASE I - OPERATION AT
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than the optimal range for methanog
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5 EXPERIMENTAL PHASES II-IV: KINGSB
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sludge on a number of occasions. Wh
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On days 99 and 100 of Phase III, a
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5.3.2 Analysis of variations in fee
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Table 5.2: Pilot-scale ABR average
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5.4.1.2 Phase III In Phase III, (Fi
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Phase II: Alkalinity [mgCaCO3/ℓ]
Page 123 and 124: Eq. 5-1 However, at a COD/SO4 2- ra
Page 125 and 126: wastewater was probably higher than
Page 127 and 128: 5.5.2.2 Damping Figure 5.12 and Fig
Page 129 and 130: • The outflow COD values were not
Page 131 and 132: • Information about the volume of
Page 133 and 134: As with the total volume of sludge
Page 135 and 136: It is not clear why the rate of acc
Page 137 and 138: most compartments was exactly 6.5,
Page 139 and 140: Soluble COD [mg/ℓ] 600 500 400 30
Page 141 and 142: pathogens and parasites, which may
Page 143 and 144: % Probe of DAPI % Probe of DAPI % P
Page 145 and 146: later compartments at all. Furtherm
Page 147 and 148: and 4, with decreasing observations
Page 149 and 150: • The mechanism of sludge build-u
Page 151: Table 5.6: Inflow and outflow chara
Page 154 and 155: Behling et al. (1997) studied the p
Page 156 and 157: organisms in previous compartments.
Page 158 and 159: velocities. Unfortunately, these tw
Page 160 and 161: Thus for a fixed sludge load, at hi
Page 162 and 163: sampling was not possible since in
Page 164 and 165: Wentzel (2006) recommends a COD to
Page 166 and 167: 6.2.1.4 Calculation of CH4 producti
Page 168 and 169: organically bound N) or that N accu
Page 170 and 171: All VFA is consumed in the process,
Page 172 and 173: However, these assumptions are clea
Page 176 and 177: influent alkalinity will increase d
Page 178 and 179: The original objective to develop a
Page 180 and 181: • It was not possible to simulate
Page 182 and 183: employed for a medium strength wast
Page 184 and 185: 6.6.4 Alternative baffle design Thi
Page 186 and 187: 6.7.3 Monitoring requirements The m
Page 188 and 189: compartments (Section 6.1.1) pH val
Page 190 and 191: generally about anaerobic digestion
Page 192 and 193: 7.1.1.6 Effect of sludge age on bio
Page 194 and 195: 7.1.2.4 Critical design parameters
Page 196 and 197: 172
Page 198 and 199: Batstone D. J., Keller J., Angelida
Page 200 and 201: Gopala K. G. V. T. (2007). Treatmen
Page 202 and 203: MacLeod F. A., Guiot S. R. and Cost
Page 204 and 205: Sasse L. (1998). Decentralised wast
Page 206 and 207: Wanasen (2003). Upgrading conventio
Page 209 and 210: METTHODS OFF SAMPLINNG AND ANNALYSI
Page 211 and 212: 3.6 Enumeration of total coliforms
Page 213 and 214: that the means are the same, or con
Page 215 and 216: And the significance of the regress
Page 217 and 218: ADDITIONAL RESULTS 193 APPENDIX A3
Page 219 and 220: Table A3. 1 cont. Phase I Phase II
Page 221 and 222: each of the eight compartments were
Page 223 and 224: 3.2 Pathogen indicator organisms A
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APPLIED VS. APPARENT HYDRAULIC RETE
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19 h apparent HRT 14 h apparent HRT
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205 APPENDIX A5 CALCULATION OF SOLI
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i.e. the average SRT of an accumula
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X X = P Inert ⋅ where Xinert is t
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iodegradable organic material may b
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Substituting Eq. A6- 1 in Eq. A6- 7
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1.5 Implementation of steady-state
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X = 7⋅ Y = 7 Z = 7⋅ A = 7⋅ (
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Dama, P., Bell J., Naidoo, V., Foxo
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Lalbahadur T. (2004) Characterisati
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