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2.5.3.4 Scanning electron microscopy study of sludge samples Pillay (2006) studied samples of sludge from the pilot-scale ABR operating at two different flow rates using scanning electron microscopy (SEM). He tentatively identified anaerobic micro-organisms based on morphology and concluded that greater concentration and greater diversity of microorganisms were observed at lower flow rates. He was also not able to identify any Methanosaeta spp. in samples (Methanosaeta spp. are acetoclastic methanogens thought to be responsible for granule formation). These results are presented in some detail in Section 5.7.2.2. 2.5.3.5 Pathogen indicator organism removal Pillay (Pillay, 2006) measured pathogen indicator organisms (E. Coli, total coliforms, coliphages and helminth eggs) in inflow and outflow streams of the pilot-scale ABR. Statistically significant removals of all of these indicators were observed, with highest removal rates for helminth eggs. However, the outflow stream still had unacceptably high pathogen loads, and it was concluded that further treatment would be required before effluent could be safely discharged to the receiving environment. These results are also presented in Appendix A3.3.2 2.6 SUMMARY This chapter has presented a review of general theory of anaerobic digestion, anaerobic digester technology, anaerobic digestion of sewage and research into the anaerobic baffled reactor. Much research has been undertaken on baffled reactors treating soluble or synthetic wastewaters, but limited work has been performed on the treatment of real domestic wastewater. Further, most studies were have been undertaken at laboratory scale. Therefore experimental work is required to develop an understanding of the application of ABR technology for large-scale treatment of domestic wastewaters in order that they may be adequately designed and maintained for this purpose. 50
"AAs you know, , you go to wwar with thee army you have, h not thee army you mmight want or o wish to haave at a laterr time." – Doonald Rumsfeeld This project undeertook an expperimental sstudy using a 3 000 ℓ pillot-scale ABRR treating wastewater w att Umbiilo and Kinggsburgh WWWTPs. This chhapter is presented in two parts; in thhe first, the design d of thee pilot-scale ABR, the construuction of thhe reactor an nd details oof installationn configurat tions duringg experrimentation are reportedd. In the second part, methods m used in the anallysis of pilot t-scale ABRR perfoormance are ddescribed. 3.1 All experimental data presentted in this thhesis were obtained o fromm a 3 000 ℓ ppilot-scale ABR A treatingg municipal wastewwater. 3.1.1 3 THE PILOOT-SCALE A PILOT--SCALE AABR INS STALLATTIONS AND OPER RATIONN ABR Pilot-scale ABR desiign The ddesign of the pilot-scalee ABR was tthe basis of an MSc Enng study unddertaken by Dama D in thee School of Chemiccal Engineerring, Universsity of Natal. The design of the pilot rreactor used in this studyy was llaboratory-sccale ABRs thhat had beenn used for co o-digesting tooxic and higgh strength effluents e in a previous WRC pproject (WRRC project KK5/853, Bel ll et al., 2007). These reactors con nsisted of 8 comppartments, annd a total woorking volumme of 10 ℓ. Fl low betweenn compartments was throu ugh a slot inn each alternate bafffle. Figurre 3.1: 10 ℓ Perspex laboratory-scale ABRs s showing innlet, internaal baffles, ga as vents andd saampling porrts ((Bell, 20002)) Figurre 3.1 is a phhotograph off the laboratoory-scale reac ctors. As thhere was no experimentaal basis for ddeciding whether the design should be changed, , two designn parammeters were investigatedd using commputational fluid f dynamics (CFD) mmodelling te echniques too identiify improvemments for thhe pilot reacttor design (D Dama et al., 2001)). Firrstly, the effe fect of bafflee 51
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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
Page 23 and 24: xix LIST OF ABBREVIATIONS A-HRT App
Page 25 and 26: 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 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
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wastewater was probably higher than
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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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