Thomasine Rudd

Anaerobic digestion processes in industrial waste water treatments

1 The Biochemistry of Anaerobic Digestion.- 1.1 Kinetics of Substrate Utilisation and Bacterial Growth.- 1.1.1 COD Fluxes and Mean Carbon Oxidation State.- 1.1.2 Bacterial Growth and Biokinetics.- 1.1.2.1 Growth and Single Substrate Kinetics.- 1.1.2.2 Multisubstrate Systems.- 1.2 Kinetics and Biochemistry of Hydrolysis.- 1.3 Kinetics and Biochemistry of Fermentation and ?-Oxidation.- 1.4 Kinetics of Methanogenesis.- References.- 2 The Microbiology of Anaerobic Digestion.- 2.1 Nutrient Balance in Anaerobic Digesters.- 2.2 Origin and Nature of Digester Bacteria.- 2.3 The Hydrolysing Bacteria.- 2.3.1 End-Product Inhibition During Hydrolysis.- 2.4 Intermediate Metabolism.- 2.4.1 The Fermenting Bacteria.- 2.4.2 The Bacteria of ?-Oxidation.- 2.5 The Methanogenic Bacteria.- 2.6 Other Bacterial Conversions.- 2.7 Anaerobiosis.- References.- 3 Forms of Biomass.- 3.1 Adhesion.- 3.1.1 The DVLO Theory.- 3.1.2 Interfacial Free Energy and Adhesion.- 3.1.3 Deformation in Relation to Adhesion.- 3.2 Biofilm Formation.- 3.3 Floc Formation.- 3.4 Pellet Formation.- 3.5 Entrapment in Natural Polymers.- 3.6 Estimation of Microbial Mass and Activity.- References.- 4 Influence of Environmental Factors.- 4.1 Temperature.- 4.2 Hydrogen Ion Concentration (pH).- 4.3 Physical Parameters.- 4.4 Nutrients.- References.- 5 Toxic Substances in Anaerobic Digestion.- 5.1 Volatile Acids Inhibition.- 5.2 Sulphide Inhibition.- 5.3 Ammonia-Nitrogen Inhibition.- 5.4 Heavy Metals.- 5.4.1 The Effect of Heavy Metal Speciation in Anaerobic Digestion.- 5.4.2 The Effect of Heavy Metals on the Bacterial Flora of Anaerobic Digesters.- 5.5 The Effect of Cyanide.- 5.6 Anthropogenic and Recalcitrant Compounds in Anaerobic Digestion.- 5.6.1 Response of Digester Systems to Complex Organics.- 5.6.2 Response of Anaerobic Bacteria to Hazardous Organic Molecules.- References.- 6 Single-Staged Non-Attached Biomass Reactors.- 6.1 The Continuously Stirred Tank Reactor.- 6.1.1 Design and Operation.- 6.1.2 Process Efficiency.- 6.2 The Contact Process.- 6.2.1 Design and Operation.- 6.2.2 Process Efficiency.- 6.3 The Upflow Anaerobic Sludge Blanket Reactor.- 6.3.1 Design and Operation.- 6.3.2 Process Efficiency.- References.- 7 Single-Stage Fixed-Film Filter and Contact Processes.- 7.1 Anaerobic Filters.- 7.1.1 Design and Operation.- 7.1.2 Process Efficiency.- 7.2 Rotating Biological Contactors.- 7.2.1 Design and Operation.- 7.2.2 Process Efficiency.- 7.3 Carrier-Assisted Contact Reactors.- 7.3.1 Design and Operation.- 7.3.2 Process Efficiency.- 7.4 Hybrid Reactors.- References.- 8 Single-Stage Fixed-Film Expanded Processes.- 8.1 Expanded Bed Reactors.- 8.1.1 Design and Operation.- 8.1.2 Process Efficiency.- 8.2 Fluidised Bed Reactors.- 8.2.1 Design and Operation.- 8.2.2 Process Efficiency.- References.- 9 Developments in Reactor Design.- 9.1 Improvements.- 9.2 Multi-Stage Operations.- 9.3 Two-Phase Digestion.- References.- 10 Start-Up of Anaerobic Bioreactors.- 10.1 Nutrient Balance and Inhibition at Start-Up.- 10.2 Seeding and Loading Regimes.- 10.3 Washout.- 10.4 Turbulence and Shear.- References.- 11 Economic Considerations.- 11.1 Comparisons of Reactor Types and Efficiencies.- 11.1.1 Overloading and Intermittent Operation.- 11.1.2 Tolerance to Toxic Shocks.- 11.2 Wastewater Characteristics.- 11.3 Cost Analyses.- References.- 12 List of Abbreviations.- 13 Subject Index.

Formation and conditional stability constants of complexes formed between heavy metals and bacterial extracellular polymers

The strength and nature of the binding of heavy metal ions to bacterial extracellular polymers has been investigated. The conditional stability constants (Kt) for complexes formed between extracted Klebsiella aerogenes polymer and copper, cadmium, cobalt and nickel were determined, using a gel chromatographic technique, and log Kt values of 7.69, 5.16, 5.48 and 5.49 respectively were obtained. Adsorption isotherms constructed for copper, cadmium and cobalt indicated that metal uptake occurred after the initial complexation capacity had been exceeded, suggesting the presence of more than one binding site, but nickel adsorption ceased when the complexation capacity was reached. Nickel was found to be associated predominantly with the soluble form of polymer, and copper and cadmium with the colloidal fraction when metals were added to the polymer simultaneously, rather than individually. The overall specific metal uptake by polymers extracted from activated sludge was approximately ten times higher than that by K. aerogenes polymer.

Fate and effects of cyanide during wastewater treatment processes

This paper presents a literature review on the fate and effects of cyanide and its species during wastewater treatment at conventional sewage treatment works. Initially, the chemistry, speciation and associated toxicities of cyanide are considered, after which the sources of cyanide to wastewaters are reviewed. The susceptibility of cyanide species present in wastewater to stripping to the atmosphere, adsorption to particulate material, chemical transformations and biological degradation during primary treatment and activated sludge treatment is discussed. The possible adverse effects of cyanide on biological sewage treatment processes are considered to assess whether there are any threshold effect levels.

Extraction of extracellular polymers from activated sludge

SummaryMethods of deflocculating activated sludge to facilitate separation of extracellular material have been investigated. Total sludge carbohydrate was estimated to be 160 mg g−1 SS, of which 60 mg g−1 SS could be extracellular. An alkaline treatment extracted this quantity but a less rigorous ion-exchange technique was chosen for routine extraction.

Mass balance of heavy metal uptake by encapsulated cultures ofKlebsiella aerogenes

Dialysis was employed as a method of speciating heavy metals in cultures of an extracellular polymer forming strain ofKlebsiella aerogenes. A noncapsulated strain of the same bacterium was used as a control, and a mass balance of copper, cadmium, cobalt, nickel, and manganese in batch culture at pH 4.5 and pH 6.8 and in continuous culture at pH 6.8 was constructed. Copper and cadmium were accumulated by the cell during rapid proliferation whereas all 5 metals were bound nonspecifically by extracellular polymer produced during stationary phase and at low dilution rates. The presence of extracellular polymer appeared to inhibit cellular uptake of nickel. At the lower pH, metal uptake was considerably reduced. The results are discussed in the context of metal removal in the activated sludge process of waste water treatment.

Influence of Environmental Factors

Several environment factors can affect anaerobic digestion, either by enhancing or inhibiting parameters such as specific growth rate, decay rate, gas production, substrate utilisation, start-up and response to changes in input.

DISTRIBUTION OF HEAVY METALS IN THE RIVER YARE AND ITS ASSOCIATED BROADS. III, LEAD AND ZINC

Abstract The magnitude and spatial distribution of lead and zinc within the bottom sediments of the River Yare, Norfolk, have been investigated, together with effects imposed by grain size, sediment organic content and channel morphological controls. Metal concentrations varied widely, ranging between 10.7 and 728 mg Pb kg −1 and between 23 and 1190 mg Zn kg −1 , producing maximum enrichments of 22 and 27 times the Yares natural background levels of lead and zinc, respectively. Non-point source metal inputs appeared to be the dominant mode of entry into the system. Sediment texture, particularly its organic content, appeared to be the principal factor controlling metal accumulation. Mean lead and zinc concentrations increased by a factor of four as the proportion of volatile solids increased from 0.5 to 25%. The influence of grain size appeared to be limited to its effects upon sediment transport and sediment organic content rather than to the adsorptive capacity of different particle sizes. Lead and zinc concentrations did not increase with decreasing particle size, but showed elevated loadings in the 1000-250 and 250-64 μm particle size ranges. A shift in dominant metal/particulate associations was observed towards the finer size fractions with increased distance downstream. This probably reflected disaggregation effects during sediment transport and the contrasting nature of metallic inputs, from the coarser runoff derivatives in the upper urban stretch to the finer, highly organic particles released in STW final effluent further downstream.

The Microbiology of Anaerobic Digestion

The combined and coordinated metabolic activity of an anaerobic reactor population is required for the complete degradation of complex organic matter to CO2 and CH4. The intermediates necessary for certain microorganisms are produced as a consequence of the action of others and therefore consortia of bacteria are frequently involved in these conversions. Despite several analyses of the major non-methanogenic bacteria present in anaerobic digesters, detailed investigations into the generic and specific nature of the hydrolytic and fermentative populations have not generally been reported. The predominant organisms in some waste-treatment systems may not, moreover, participate actively in the process but may merely be components of the wastestream itself; coliforms have been implicated here [1].

Comparison of the treatment of a synthetic meat waste by mesophilic and thermophilic anaerobic fluidized bed reactors

Abstract Thermophilic anaerobic fluidised bed reactors (AFBRs) were shown to achieve inferior COD removal efficiencies in comparison to mesophilic AFBRs treating a synthetic meat waste. Organic removal efficiencies of 45.6–83.7% were observed for mesophilic reactors over a range of COD loadings between 0.5 ‐ 32 kg m‐3 d‐1, while removal efficiencies of the thermophilic reactors were between 33.1–62% over the same range. The optimum hydraulic retention time (HRT) was found to lie within the range of 6–13 h at a COD loading of 4.6 kg m‐3 d‐1. There appeared to be little difference between the optimum HRT for thermophilic and mesophilic reactors.

Start-up of anaerobic bioreactors on high strength industrial wastes

Abstract Anaerobic filters, anaerobic fluidized beds and upflow anaerobic sludge-blanket (UASB) reactors were started up on two types of pharmaceutical waste; anaerobic fluidized beds were also started up on glucose, fruit processing, soft drink manufacturing and pharmaceutical wastes. Fluidized beds proved superior to UASB reactors and filters in COD removal capacity and pH stability during start-up, although methane production was greatest in the UASB systems. The industrial wastes proved recalcitrant to anaerobic conversion as they contained substances inhibitory to microorganisms but loadings of up to 7·5 kg COD m −3 day −1 could be applied with a COD removal of 78% achieved. The types of volatile acids produced in four of the units were found to relate closely to substrate composition.