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Technical report
Water Res. Vol. 17, No. 12, pp. 1945, 1983 Printed in Great Britain
0043-1354/83 $3.00 + 0.00 Pergamon Press Ltd
TECHNICAL REPORT
IAWPRC SPECIALISED SEMINAR ON ANAEROBIC TREATMENT OF WASTEWATER IN FIXED FILM REACTORS Copenhagen, Denmark, 16-18 June, 1982
This IAWPRC sponsored seminar was arranged by the Department of Environmental Engineering, Technical University of Denmark, in collaboration with the Danish Committee of IAWPRC. The 80 delegates from 21 countries included most of the specialists in basic research in the field of anaerobic fixed films. The research effort expended on fixed anaerobic film processes has increased considerably during the past few years in parallel with increased interest in anaerobic wastewater treatment processes. The seminar indicated that research can be expected to continue at the same level for some years to come. The scientific programme consisted of the presentation of a comprehensive review and 20 original papers, together with thorough discussions. The scientific outcome of the seminar can be summarised as follows:
Feasibility Anaerobic treatment of industrial wastes in fixed film reactors is already widespread. The process is cost effective for warm wastes with a high concentration of biodegradable organic matter (1-2 kg COD m-~). For colder and more dilute wastes, such as domestic sewage, the process is not cost effective at present, but the trend in process development indicates that this might change in the future. Substrates The composition of the substrate is important in relation to design of anaerobic processes. The removal rate, measured as kgCOD (kg VSS.d) -j, is 5-6 times higher when acetic acid is the substrate as compared to a process where glucose---or more complex organics--is the substrate, This illustrates the importance of making biomass balances to account for biomass fractions, Attached vs suspended biomass Many biofilm reactors operate with significant amounts of suspended biomass which obscures interpretation of experimental data and renders design of such reactors
difficult. It is an open question whether biofilm surface area or total biomass is the most important reactor property.
Diffusional resistance The question of diffusional resistance within the biofilm is crucial for the understanding of the kinetics of anaerobic fixed fires. Provisional theoretical calculations indicate that it does not play a significant role, but there is no experimental evidence to support this. In the literature the same set of data have been used for verification of models both with or without diffusional resistance. Biofilm structure The existence of a biofilm structure in a reactor is beneficial with respect to resistance to toxic substances and inert material in the waste and acts as a safeguard against biomass wash-out. The mechanisms governing the development of a biofilm both on inert support material and in pellets/granules is not well understood. Start-up Start-up problems often encountered in anaerobic fixed film reactors emphasise the lack of basic knowledge of the microbiology and the biochemistry of the processes involved. Time consumption during start-up might be reduced considerably through increased knowledge of biofilm build-up, the presence of essential micronutrients, pH and temperature effects. The proceedings of the seminar will be published in the 1AWPRC journal Water Science and Technology, available on subscription or as one of the benefits of Associate Membership of IAWPRC. The proceedings will also be published separately in book form. Individual Members may purchase all IAWPRC publications and any Pergamon Press publications at a discount of 25% on the normal price. Details from Pergamon Press at the address given in this journal.
1945
MOGENS HENZE Technical University o f Denmark Denmark
0043-1354/83 $3.00 + 0.00 Pergamon Press Ltd
TECHNICAL REPORT
IAWPRC SPECIALISED SEMINAR ON ANAEROBIC TREATMENT OF WASTEWATER IN FIXED FILM REACTORS Copenhagen, Denmark, 16-18 June, 1982
This IAWPRC sponsored seminar was arranged by the Department of Environmental Engineering, Technical University of Denmark, in collaboration with the Danish Committee of IAWPRC. The 80 delegates from 21 countries included most of the specialists in basic research in the field of anaerobic fixed films. The research effort expended on fixed anaerobic film processes has increased considerably during the past few years in parallel with increased interest in anaerobic wastewater treatment processes. The seminar indicated that research can be expected to continue at the same level for some years to come. The scientific programme consisted of the presentation of a comprehensive review and 20 original papers, together with thorough discussions. The scientific outcome of the seminar can be summarised as follows:
Feasibility Anaerobic treatment of industrial wastes in fixed film reactors is already widespread. The process is cost effective for warm wastes with a high concentration of biodegradable organic matter (1-2 kg COD m-~). For colder and more dilute wastes, such as domestic sewage, the process is not cost effective at present, but the trend in process development indicates that this might change in the future. Substrates The composition of the substrate is important in relation to design of anaerobic processes. The removal rate, measured as kgCOD (kg VSS.d) -j, is 5-6 times higher when acetic acid is the substrate as compared to a process where glucose---or more complex organics--is the substrate, This illustrates the importance of making biomass balances to account for biomass fractions, Attached vs suspended biomass Many biofilm reactors operate with significant amounts of suspended biomass which obscures interpretation of experimental data and renders design of such reactors
difficult. It is an open question whether biofilm surface area or total biomass is the most important reactor property.
Diffusional resistance The question of diffusional resistance within the biofilm is crucial for the understanding of the kinetics of anaerobic fixed fires. Provisional theoretical calculations indicate that it does not play a significant role, but there is no experimental evidence to support this. In the literature the same set of data have been used for verification of models both with or without diffusional resistance. Biofilm structure The existence of a biofilm structure in a reactor is beneficial with respect to resistance to toxic substances and inert material in the waste and acts as a safeguard against biomass wash-out. The mechanisms governing the development of a biofilm both on inert support material and in pellets/granules is not well understood. Start-up Start-up problems often encountered in anaerobic fixed film reactors emphasise the lack of basic knowledge of the microbiology and the biochemistry of the processes involved. Time consumption during start-up might be reduced considerably through increased knowledge of biofilm build-up, the presence of essential micronutrients, pH and temperature effects. The proceedings of the seminar will be published in the 1AWPRC journal Water Science and Technology, available on subscription or as one of the benefits of Associate Membership of IAWPRC. The proceedings will also be published separately in book form. Individual Members may purchase all IAWPRC publications and any Pergamon Press publications at a discount of 25% on the normal price. Details from Pergamon Press at the address given in this journal.
1945
MOGENS HENZE Technical University o f Denmark Denmark