Vertical flow constructed wetlands for the treatment of inorganic ...

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wet and dry cycles, oxidation-reduction (redox) potential, among others, which dictate removal processes, can be easily regulated in order to enhance removal of one or more selected pollutants. It has been verified that the maturity of a CW system is an important factor influencing its removal efficiency – pollutant removal in wetlands is dependent on plant and microbial mediated reactions, plant and microbial communities take time to establish and reach steady state conditions. Because of this, it is common that new wetlands improve in pollutant removal performance as they age (Bulc, 2006). The following sections will highlight some major pollutant removal mechanisms in constructed wetlands with a greater focus on nitrogen and heavy metals which are commonly found in inorganic industrial wastewaters. 2.4.1 Organic carbon (C) While organic carbon is a major pollutant in municipal and food/beverage processing wastewaters, in wastewaters from chemical and fertiliser industries, carbon is usually lacking. The lack of carbon has major implications for nitrogen removal systems relying on the conventional denitrification pathway and it will be further discussed in the nitrogen section. Carbon is not considered difficult to remove biologically and, in general, wetlands are efficient in the reduction of organic matter. Organic carbon compounds in wastewaters are usually quantified and monitored indirectly by different analytical techniques with the most common being: Biochemical Oxygen Demand (BOD) is a measure of the oxygen consumed by microorganisms in the oxidation of organic matter. This test usually runs for 5 days and the final oxygen consumption is designated BOD5. Chemical oxygen demand (COD) is the amount of a chemical oxidant, usually potassium dichromate, required to oxidise the organic matter. This measure is larger than BOD because the strong oxidant oxidises more compounds than microorganisms do. 14
Total organic carbon (TOC) determination usually involves measuring the inorganic and organic carbon fractions present in a sample and then subtracting the inorganic component (i.e. CO2) from the total. Measurements of organic carbon can be made before or after filtration in 0.45um pore size filter, resulting in total and dissolved COD, BOD or TOC. 2.4.1.1Organic Carbon reactions Treatment wetlands may receive large amounts of external organic carbon. Degradable carbon is decomposed or transformed by a variety of reactions depending on the conditions present in the wetland. Under aerobic conditions carbon compounds are oxidised via respiration by microorganisms with oxygen being the final electron acceptor. When no oxygen is available other electron acceptors are involved in decomposition. Under anoxic (no dissolved molecular oxygen is available) or anaerobic (no dissolved molecular nor bound oxygen) conditions carbon compounds are degraded via fermentation, denitrification, iron/sulfate reductions or methanogenesis. Important reactions are represented below (Kadlec and Wallace, 2009, Mitsch and Gosselink, 1993). In aerobic conditions respiration prevails (glucose as substrate): C6H12O6 + 6 O2 � 6 CO2 + 6 H2O (2.1) In anoxic or anaerobic conditions fermentation occurs: C6H12O6 � 2 CH3CHOHCOOH (lactic acid) (2.2) C6H12O6 � 2 CH3CH2OH (ethanol) + 2 CO2 (2.3) Nitrate (NO3 - ) reduction (denitrification) occurs in anoxic zones: C6H12O6 + 4 NO3 - � 6 CO2 + 6 H2O + 2 N2 + 4 e - (2.4) Iron reduction occurs in anaerobic conditions (acetate as substrate): CH3COO - + 8 Fe3 + + 3 H2O � 8 Fe +2 + CO2 + HCO3 - + 2 H2O + 8H + (2.5) 15
Page 1: Vertical flow constructed wetlands
Page 4 and 5: 1. Journal articles: Items derived
Page 6 and 7: Berryman and Frances Brigg provided
Page 8 and 9: The feasibility of using carbon ric
Page 10 and 11: Table of Contents Items derived fro
Page 13 and 14: 1.1 Industrial wastewaters Chapter
Page 15 and 16: eneficial as long as the water is t
Page 17 and 18: 1.4 Scope of this thesis The main r
Page 19 and 20: Chapter 8 describes the design rati
Page 21 and 22: similar to aerobic ponds, usually s
Page 23 and 24: 2.3 Common uses of constructed wetl
Page 25: These systems favour settling of su
Page 29 and 30: organically bound N is called ammon
Page 31 and 32: Biochemically equation 2.11 is subd
Page 33 and 34: oxidised. External carbon sources s
Page 35 and 36: 2009) in FWS wetlands, and also oxy
Page 37 and 38: intensive (Reed et al., 1995). Harv
Page 39 and 40: limited because they only allow the
Page 41 and 42: whose distribution followed a clear
Page 43 and 44: The concentration of heavy metal io
Page 45 and 46: Metal carbonates: When the concentr
Page 47 and 48: and 8.3g Na2SO4/L. The authors attr
Page 49 and 50: therefore were selected for a 97 da
Page 51 and 52: Chapter 3: Salinity impact on nitri
Page 53 and 54: associated with the reduced number
Page 55 and 56: 2000). The theoretical HRT is the a
Page 57 and 58: 3.2.3 Water sampling and analysis W
Page 59 and 60: Table 3.1: Sediment sampling dates
Page 61 and 62: threshold calculation suggested by
Page 63 and 64: 18 days. The plants in T2 wetlands,
Page 65 and 66: Even though known amounts of sea sa
Page 67 and 68: 3.3.3.1 Ammonia removal Ammonia rem
Page 69 and 70: NH 3-N (mg/L) 160 140 120 100 80 60
Page 71 and 72: attempted to be answered in one of
Page 73 and 74: During Phase I, the overall average
Page 75 and 76: NH3-Nconcentration out (mg/L) Figur
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to the literature, some peaks have
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3.3.5.2.1 Control wetland TRFLP ana
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% of total peak area 100 90 80 70 6
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% of total peak area 100 90 80 70 6
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3.4 Discussion 3.4.1 Plant health S
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ones reported by Kantawanichkul et
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Chen et al. (2003) observed nitrite
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Ward et al. (2000) found that in th
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Chapter 4: Nitrification and denitr
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Figure 4.1: Experimental set up dem
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of sediment was performed through t
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4.2.7 Data analysis Microsoft Excel
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4.3.2.2 NO3-N Effluent nitrate conc
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The load vs concentration chart pre
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Because the influent pump did not d
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increased during the first two week
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clear seasonal variation in nosZ ge
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4.4 Conclusions The unplanted semi
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Fick 1997; Ingersoll and Baker, 199
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Both systems were planted with nati
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A B C Figure 5.2: A. Containers hol
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5.3.1.1 Implications of storage for
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NO 3-N (mg/L) 100 90 80 70 60 50 40
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COD (mg/L) 600 500 400 300 200 100
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Chapter 6: Heavy metals in a constr
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Figure 6.1: Photo of the constructe
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potassium, phosphorus, sulphur and
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Table 6.2: Mean (standard deviation
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values are comparable to the Aqua R
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On a dry weight basis, macrophyte r
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Chapter 7: Nitrogen removal and amm
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etween the sand surface and 0.3m ab
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profiles were analysed using Genema
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Table 7.1: Monthly total flows, ave
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clones S8-sludge and S9-sand which
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specific 119bp OTU. Even though N.
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Chapter 8: Design and monitoring of
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VF wetlands operated in parallel in
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8.2.1.1.4 Distribution/collection p
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Figure 8.4: Wetland cell 1 on the f
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Figure 8.7: Cell 2 being tested at
Page 159 and 160:
on Figure 8.7. Within a year vegeta
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NH3-N Load (kg/d) 900 800 700 600 5
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The same strong positive correlatio
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construction and planting costs, in
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Considering the findings and limita
Page 169 and 170:
Brant A.H., Jagoe C.H., Kelsey-Wall
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Crites, R., Tchobanoglous, G. (1998
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Gorra, R., Coci, M., Ambrosoli, R.
Page 175 and 176:
Kadlec, R.H., Bastiaens, W.V. and U
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eactors. WEFTEC 79th Annual Technic
Page 179 and 180:
16S rRNA and amoA sequence analysis
Page 181 and 182:
Sun, G. and Austin, D. (2007). Comp
Page 183 and 184:
Wu, Y., Tam, N.F.Y. and Wong, M.H.
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Figure A2: Permeability of the sand
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Treatment 1 wetland Dec-08 Mar-09 A
Page 189 and 190:
Comparison of Surface samples from
Page 191 and 192:
Treatment 1 wetland Mar-09 Figure B
Page 193 and 194:
Appendix C. Complementary results f
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