PERFORMANCE OF THE H-FFBR IN REMOVING ORGANIC POLLUTANTS

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Biofilm carriers

A moving-bed biofilm reactor (MBBR) and an integrated fixed-film activated sludge (IFAS) bioreactor are compact biological wastewater treatment systems that use submerged highsurface- area movable/floating plastic carriers (media) in aerobic and/or anoxic zones (Sen and Randall, 2008; Boltz et al., 2009). The IFAS process was introduced in the late 1990s as an evolution of the MBBR where activated sludge is recycled back to the bioreactor containing the carriers (Rosso et al., 2011).
The analysis of hybrid systems is very complicated due to the difficulty of conducting the biofilm analyses, and differentiation between suspended (heterotrophic biomass) and attached (nitrifying biomass) microbial activity (Albizuri et al., 2009). Describing a hybrid system using steady state model based on Monod kinetics expressions often yields a set of algebraic equations having no explicit solution even for biofilm only (Sen and Randall, 2008). At present, hybrid bioreactors are designed and based on a recommended volume ratio of the biofilm carrier to the reactor, which is obtained from field experience or experimental results (Fouad and Bhargava, 2005). Ratcliffe et al. (2006) reported that the filling of carrier media may be decided for each case giving flexibility in the specific biofilm surface area. A carrier filling ratio of 70% allowed the plastic media to move freely (Abdul-Majeed, 2012) without dead or unused spaces in the reactor (Ratcliffe et al., 2006).
Minimal difference in performance was found between a 33% and 66% carrier filling rate; however, at a carrier filling rate of 70% the attached growth density was 5 to 13 times higher and responded more strongly to influent COD than that of activated sludge floc found in suspended activated sludge systems (Qiqi et al., 2012). Makowska et al. (2013) reported that a carrier filling rate of 70% achieved 91% to 94% removal of organic compounds and 73% to 85% removal of nitrogenous compounds from CGWW.
Biofilm carriers are found in a variety of shapes, sizes, geometries, material composition and treatment capabilities. Manufactured carriers of the fixed-bed cord type variety include exagonal-cell-cord-looped and linear-looped-cord types, while carriers of the movable type include polyethylene-finned cylinders resembling wagon wheels and cuboid sponges. The carrier material must protect the biofilm from toxic and inhibitory effects and excessive shear forces (Boltz et al., 2009; Quan et al., 2012; El-Jafry et al., 2013).
The type of media selected should be such that the biofilm specific surface area does not decrease significantly as the thickness increases (Sen et al., 2007).

CHAPTER 1: INTRODUCTION
1.1 Background
1.2 Problem statement
1.3 Aims and objectives
1.4 Methodology
1.5 Organisation of the thesis
CHAPTER 2: LITERATURE REVIEW
2.1 Background
2.2 Sasol-Lurgi Fixed-Bed Dry Bottom (FBDBTM) process generating coal gasification stripped gas liquor wastewater
2.3 Characterisation of coal gasification stripped gas liquor wastewaters
2.3.1 Organic compounds
CHAPTER 3: MATERIALS AND METHODS
3.1 Chemicals, reagents and gases
3.2 Pilot plant reactor design and operating parameters
3.2.1 Pilot plant reactor design
3.2.2 Reactor operating parameters
3.3 Collection and preservation of reactor samples
3.4 Analytical methods and equipment
3.4.1 Determination of metals
3.4.2 Determination of chemical and physical parameters
3.4.3 Determination of anions by ion chromatography
3.4.4 Identification of organic compounds by gas chromatographymass
spectrometry (GC-MS)
3.4.5 Determination of soluble phenol
3.5 Mobilisation of the bioaugmentation inocula for laboratory test work
3.6 Phylogenetic analysis of the microbial communities
3.7 DNA extraction and PCR analysis of the bioaugmentation inocula
3.7.1 Metagenomic sequencing data
3.7.2 16S rRNA and 18S rRNA sequencing
3.8 Analysis of attached and suspended biomass
3.8.1 Attached biomass weight
3.8.2 Attached and suspended biomass activity
3.8.3 Biofilm structure
3.8.4 Fourier transform infrared (FT-IR) spectroscopy
3.9 Artificial intelligence model development
3.9.1 Model topology development
3.9.2 Selection of input variables
3.9.3 ANN training and validation
3.9.4 Sensitivity analysis and knowledge discovery
3.10 Statistical analysis
CHAPTER 4: METAGENOMIC STUDY OF THE MICROBIAL COMMUNITY
IN THE H-FFBR
4.1 Microbial community and diversity by Illumina high-throughput sequencing
4.1.1 Microbial community and diversity at high taxonomic levels
4.1.2 Microbial community and diversity at low taxonomic levels
4.1.3 Core microbial genera and species of the indigenous microbial community
4.2 Measurement of community diversity across the H-FFBR
4.2.1 Alpha diversity
4.2.2 Principal coordinates analysis (PCoA) of beta diversity
4.2.3 PERMANOVA statistical analysis using unique fraction metric
(UniFrac)
4.2.4 Effect of operating rameters on the microbial community diversity
CHAPTER 5: PERFORMANCE OF THE H-FFBR IN REMOVING ORGANIC
POLLUTANTS
5.1 Characteristics of the coal gasification stripped gas liquor
5.1.1 Identification of organic compounds in the feed and effluent by GC-MS
5.1.2 Identification of organic compounds in the effluent by FT-IR
5.1.3 Chemical and physical composition of the effluent
5.1.4 Metals in the effluent and effect of metals on biomass activity
5.2 Attached biomass and suspended biomass
5.2.1 Attached biomass activity versus suspended biomass activity
5.2.2 Biofilm structure
5.3 Performance of the H-FFBR in removing pollutants
5.3.1 Removal of phenols
5.3.2 Removal of soluble COD
5.3.3 Removal of nitrogen
5.3.4 Nutrient uptake
CHAPTER 6: BIOAUGMENTATION OF THE H-FFBR FOR THE REMOVAL
OF COD AND PHENOLS
CHAPTER 7: AN INTELLIGENT MODEL FOR THE PREDICTION OF COD AND PHENOL REMOVAL
CHAPTER 8: CONCLUSIONS AND RECOMMENDATIONS
CHAPTER 9: REFERENCES
APPENDICES