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

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Figure 3.5: Orthographic projection of the pilot-scale ABR (Dama et al., 2001) 3.1.1.2 Construction of feed box Wastewater feed was fed to the reactor via a feed splitter box. The splitter box consisted of 3 chambers (Figure 3.6). Wastewater was delivered to the middle chamber. Approximately 90 % of the flow supplied by the pump was bypassed (left compartment in Figure 3.6 (a); right compartment in Figure 3.6 (b)). The rest overflowed into the feed chamber (right compartment in Figure 3.6 (a); left compartment in Figure 3.6 (b)). The feed chamber had 3 outlets. A butterfly control valve (FC1) was fitted on the lowest outlet. This valve was used to periodically drain the feed chamber in order to control flow into the reactor. When the control valve was closed, the level in the feed chamber rose until wastewater overflowed through the feed pipe into the ABR. A third (highest) outlet on the feed chamber was supplied to collect overflow in the event of a blockage to the ABR feed line (emergency overflow, Figure 3.6 (b)). (Dama, (in preparation)). Figure 3.6: Schematic diagram of the feed splitter box installed at the inlet of the pilot-scale ABR (left); and reverse view of the splitter box installed on the ABR (right) 3.1.1.3 Auxiliary equipment The pilot-scale ABR study aimed to investigate microbiological and chemical performance of the ABR configuration when fed domestic wastewater under controlled feed conditions. All of the 54 Emergency overflow Controlled bypass and valve Reactor feed line Wastewater in 90% bypass
additional equipment used in the pilot-scale ABR installations was there for the purpose of sampling wastewater from a much larger flow than could be handled by the ABR, and feeding it to the reactor in a controlled and quantifiable manner. These included: • A submersible pump to deliver municipal wastewater to the pilot-scale ABR. • A pneumatic valve to control air supply to the by-pass valve. • A compressor to supply air to the pneumatic valve. • A magnetic flow meter (FI1) to measure and transmit flow rate at the outlet of the last compartment and cumulative flow. • A programmable logic controller (PLC) to capture flow rate data, calculate feeding/by-passing requirements and control the by-pass valve. • A timer control switch to control the by-pass valve when the PLC was off-line. 3.1.1.4 Principle of flow control The reactor outlet passed through a magnetic flowmeter (FI1) which produced a signal that was recorded by a programmable logic controller (PLC). A number of different control algorithms were implemented to achieve a fixed and relatively steady flowrate. The measured flow at the outlet was used to increase or decrease the flow at the inlet by adjusting the timing of the bypass valve (FC1) opening. During the experimental studies, there were three control regimes vis. timer control, bang-bang control and Proportional Integral (PI) control. • Timer control: Before the PLC was correctly programmed a timer switch was used to open and close the by-pass valve for fixed times in a fixed control cycle. For example, the pump would be set to turn on for 10 seconds in every minute. The timer control system had no mechanism for adapting when the pump delivery rate changed. Pump delivery was erratic due to the heterogeneous nature of the wastewater, particularly the presence of rags that would jam or block the pump impellor. There was thus little control over the amount of wastewater delivered to the reactor. Further, turning the pump on and off so frequently resulted in damage to the pump motor and electrical circuits. • On-off control to flow setpoint: A bang-bang control algorithm was implemented on the PLC. This aimed to control the flow rate to not exceed a specified flow rate. This target flow was determined as the flow required to achieve a target hydraulic retention time (T-HRT). This method of control did not allow compensation for periods of high or low flow, and no record was made by the PLC of the actual amount of flow through the reactor. Therefore, the average applied hydraulic retention time (A-HRT) cannot be accurately calculated when bangbang flow control was implemented. A sample of flow data for bang-bang control is presented in Section 5.2.1. • PI control of hydraulic retention time: A Proportional-Integral (PI) controller was programmed into the PLC using a time-slicing algorithm where, for a fixed cycle of 1 min, the 55
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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
Page 27 and 28: obtained from anaerobic systems rel
Page 29 and 30: • Lalbahadur (MTech, 2005) perfor
Page 31 and 32: 1.7 ORGANISATION OF THE THESIS This
Page 33 and 34: 9 2 LITERATURE REVIEW A detailed re
Page 35 and 36: • Disintegration of composite par
Page 37 and 38: Homoacetogens are one of the most v
Page 39 and 40: Most of the control in anaerobic di
Page 41 and 42: therefore the sensitivity of the ov
Page 43 and 44: ∆Gº (W) [kcal] -10 -8 -6 -4 -2 L
Page 45 and 46: For systems with low potential for
Page 47 and 48: design of the digester in which the
Page 49 and 50: 2.2.2 Expanded granular sludge bed
Page 51 and 52: fact that for most non-ideal flow s
Page 53 and 54: hydrolysis steps to convert them to
Page 55 and 56: from the clarified zone between the
Page 57 and 58: Table 2.4: Typical pathogen surviva
Page 59: Table 2.5: Studies using anaerobic
Page 62 and 63: • There is no requirement for bio
Page 64 and 65: Kennedy and Barriault (2005) perfor
Page 66 and 67: methanogenic (Akunna and Clark, 200
Page 68 and 69: and 6 h with no significant differe
Page 70 and 71: 2.5.1.12 Granule formation in ABRs
Page 72 and 73: • A baffled reactor is described
Page 74 and 75: 2.5.3.4 Scanning electron microscop
Page 76 and 77: spacing on flow patterns in a singl
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 and 126: wastewater was probably higher than
Page 127 and 128: 5.5.2.2 Damping Figure 5.12 and Fig
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• The outflow COD values were not
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• Information about the volume of
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As with the total volume of sludge
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It is not clear why the rate of acc
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most compartments was exactly 6.5,
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Soluble COD [mg/ℓ] 600 500 400 30
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pathogens and parasites, which may
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% Probe of DAPI % Probe of DAPI % P
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later compartments at all. Furtherm
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and 4, with decreasing observations
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• The mechanism of sludge build-u
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Table 5.6: Inflow and outflow chara
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Behling et al. (1997) studied the p
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organisms in previous compartments.
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velocities. Unfortunately, these tw
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Thus for a fixed sludge load, at hi
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sampling was not possible since in
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Wentzel (2006) recommends a COD to
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6.2.1.4 Calculation of CH4 producti
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organically bound N) or that N accu
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All VFA is consumed in the process,
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However, these assumptions are clea
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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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