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Thus pilot-scale ABR inflow COD concentration data and related calculations presented from any of the operating periods may be considered to be overestimated by as much as 100 mgCOD/ℓ. More data of this type (hourly samples over 24 h) are required to support this conclusion. 5.5.1.2 Inflow alkalinity concentration Figure 5.13 presents values for alkalinity in inflow and outflow samples. In general, the outflow alkalinity is higher than the inflow alkalinity concentration, as expected. There appears to be a systematic diurnal oscillation of inflow alkalinity values, although several days worth of data would be required to confirm this. Highest alkalinity values were observed between 07h00 and 11h00. The average value was calculated to be 180 mgCaCO3/ℓ and the average value for the normal sampling hours (10h00 to 15h00) was approximately 193 mgCaCO3/ℓ. These values are not significantly different to the average value reported from all available data during regular sampling (an average value of 193 mgCaCO3/ℓ was obtained during Phase III). 5.5.1.3 Inflow pH value Figure 5.12 shows inflow and outflow pH values measured in duplicate on an hourly basis over a 24 h period. Inflow pH values varied between 6.5 and 7.5. Outflow values showed smaller variations, and were consistently lower than inflow values. As with COD and alkalinity concentrations, an increase in inflow pH value was observed between 08h00 and 13h00. The median pH value measured for the regular sampling times of day (10h00 – 15h00) was 7.0. This is the same as the median value of various combinations of regular data (Municipal data only, project team data only and both combined). However the overall median pH value for the sampling campaign was 6.8. Thus the pH values presented for inflow wastewater for regular sampling may be slightly high when considering the overall effect of pH of the inflow wastewater on ABR performance (i.e. for modelling purposes, it may be appropriate to use an inflow wastewater pH value of 6.8, rather than the value of 7.0 that arises from data from regular sampling). However, more than 1 data set is required to confirm this observation. 5.5.2 Diurnal variation of outflow characteristics Analysis of outflow characteristics led to a number of observations about the action of the ABR on the wastewater as it passed through the reactor. 5.5.2.1 Burping At 22h00, the outflow sample COD concentration exhibited a sudden spike to 1 230 mgCOD/ℓ (circled in Figure 5.12), caused by a sudden and brief expulsion of sludge. Visually, the samples appeared substantially more turbid than usual with more solids than usual settling out at the bottle of the sample vial during storage. There was no significant change in outflow COD or filtered outflow COD values for the sampling times immediately before and after this measurement, suggesting that there was no biological upset that caused the high outflow COD observed. The incident was ascribed to a burping phenomenon, whereby gas production or other fluid effects caused mixing of the sludge in the last compartment, with a short term overflow of the sludge to the outlet. Biochemical upsets are most commonly associated with inhibited methanogenesis, and corresponding increase in acid and soluble COD concentration, which was clearly not the case in this event. Burping was (visually) observed from time to time in all operating periods. 102
5.5.2.2 Damping Figure 5.12 and Figure 5.13 show that treatment in the pilot-scale ABR has a damping effect on the pH values and COD and alkalinity concentrations observed in the outflow. This can be shown using measurements of variance: • The coefficient of variation (defined on page 98) for the inflow COD concentration is 37%, while that for the outflow is 26%. (This value is calculated ignoring the 22h00 “burp” since it does not appear to be a function of the overall reactor biological or hydraulic dynamics, but rather is caused by specific solids and gas dynamics in the last compartment) • The pH range measured in inflow samples was 1.23 pH units (minimum = 6.60, maximum = 7.83), while the range of outflow pH values was 0.85 pH units (minimum = 5.83, maximum = 6.67) • Alkalinity concentrations showed higher co-efficient of variation in the inflow (21%) compared to the outflow (7%). The cause of this damping effect was not investigated, however, it is expected that the damping of oscillations in concentration was due to the combined effect of axial mixing (non-plug flow conditions in and between compartments) and non-linear dependence of biological reaction rates on substrate and product concentrations. 5.5.2.3 Applied vs. Apparent hydraulic retention time The hydraulic retention times (A-HRT) quoted throughout this thesis were calculated from the applied flow rate and the empty reactor volume i.e. 3 reactor volume m HRT h = Eq. 5-2 3 Flow rate [ m h] This implies that fluid spends the same amount of time in the ABR as it would if passed through a plug flow reactor in which the entire working volume was available for through flow. However, retention of solids in each compartment would have resulted in a reduction of the volume of the compartment available for flow of the liquid phase. This concept is depicted graphically in Figure 5.14 where reactor volume available for fluid flow is equal to the total compartment volume less the volume filled with sludge. [] [ ] Total compartment volume Apparent compartment volume (available for fluid flow) Figure 5.14: Apparent compartment volume is related to the total compartment volume and the volume occupied by solids that are retained in the compartment. 103
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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
Page 76 and 77: spacing on flow patterns in a singl
Page 78 and 79: Figure 3.5: Orthographic projection
Page 80 and 81: PLC calculated the fraction of that
Page 82 and 83: epresent buulk conditionns. Compart
Page 85 and 86: The rreactor was initially commmiss
Page 87 and 88: Phase I Phase II Phase III Phase IV
Page 89 and 90: Table 4.1: Characteristics of degri
Page 91 and 92: Table 4.2: Pilot-scale ABR approxim
Page 93 and 94: COD [mgCOD/ℓ] 2000 1800 1600 1400
Page 95 and 96: 4.3.5 Phosphorus Figure 4.8 present
Page 97 and 98: Observation of sludge in compartmen
Page 99 and 100: Another interesting observation is
Page 101 and 102: 4.4.3 pH pH measurements were perfo
Page 103 and 104: esult in low pH values. The reasons
Page 105 and 106: 4.5 SUMMARY: PHASE I - OPERATION AT
Page 107 and 108: than the optimal range for methanog
Page 109 and 110: 5 EXPERIMENTAL PHASES II-IV: KINGSB
Page 111 and 112: sludge on a number of occasions. Wh
Page 113 and 114: On days 99 and 100 of Phase III, a
Page 115 and 116: 5.3.2 Analysis of variations in fee
Page 117 and 118: Table 5.2: Pilot-scale ABR average
Page 119 and 120: 5.4.1.2 Phase III In Phase III, (Fi
Page 121 and 122: Phase II: Alkalinity [mgCaCO3/ℓ]
Page 123 and 124: Eq. 5-1 However, at a COD/SO4 2- ra
Page 125: wastewater was probably higher than
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 174 and 175: The calculated pH value is compared
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influent alkalinity will increase d
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The original objective to develop a
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• It was not possible to simulate
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employed for a medium strength wast
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6.6.4 Alternative baffle design Thi
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6.7.3 Monitoring requirements The m
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compartments (Section 6.1.1) pH val
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generally about anaerobic digestion
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7.1.1.6 Effect of sludge age on bio
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7.1.2.4 Critical design parameters
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172
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Batstone D. J., Keller J., Angelida
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Gopala K. G. V. T. (2007). Treatmen
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MacLeod F. A., Guiot S. R. and Cost
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Sasse L. (1998). Decentralised wast
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Wanasen (2003). Upgrading conventio
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METTHODS OFF SAMPLINNG AND ANNALYSI
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3.6 Enumeration of total coliforms
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that the means are the same, or con
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And the significance of the regress
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ADDITIONAL RESULTS 193 APPENDIX A3
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Table A3. 1 cont. Phase I Phase II
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each of the eight compartments were
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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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