3rd Symposium on Biological Aerated Filters (BAF3) - 1999

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    BAF's get media attention
    (School of Water Sciences, Cranfield University, 1999-03-03) Smith, Alan J.; Edwards, Wayne; Hardy, Peter; Kent, Tanya
    The Biological Aerated Filter is an accepted wastewater treatment option that has the advantage of treatment and solids separation in a single, compact reactor. Choosing the correct support media for the attached biomass is critical in the design and operation of the process to achieve the required effluent quality. This paper considers the physical properties of granular media, such as density, shape, size and surface structure in relation to biomass attachment and treatment efficiency. A pilot evaluation of downflow granular media BAF columns filled with media of different particle sizes, operated over a range of hydraulic and volumetric loading rates, is reported. Nitrification on the smallest 2-4 mm media was found to be inhibited at loading rates above 0.5 kg NH4-N and 2.5 kg BOD / m3media/d due to the greater hetrotrophic growth and enhanced wash requirement.
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    High rate biofiltration
    (of Water Sciences, Cranfield University, 1999-03-03) Bedard, P.
    High rate biofiltration is a process which has gained popularity in recent years as effluent discharge consents become ever more stringent and the available land to construct new facilities becomes more scarce. This paper discusses the developments in the Biofor® process, which has allowed the previous design limiting parameters to be increased. Significant improvements in technology combined with a better understanding of the biofiltration mechanism have allowed a new generation of Biofor® plants to be constructed. This is due to a significant program of development work focussing on increasing the water velocity through the filter, to allow an increased applied loading rate without impairing filter performance.
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    Biomodule - a combined structured and granulat media BAF
    (School of Water Sciences, Cranfield University, 1999-03-03) Williams, T. R.; Stephenson, Tom
    Biological aerated filters operate as fixed film systems in which micro-organisms grow on a submerged fixed structured or granular inert support media within an aerated reactor (Stephenson et al., 1993). Periodic backwashing of the filter is required as the media bed gradually clogs due to the growth of biomass and retention of solids. The advantage of the BAF process is the small footprint it occupies relative to comparable processes such as activated sludge and trickling filters. The small footprint is due to the fact that the fixed film of biomass on the support material (media) leads to a high concentration of active bacteria per unit volume of the media and thereby to relatively small reactors. Another advantage is the retention of suspended solids that eliminate the need for final sedimentation tanks (Hagedorn et al., 1994). For the same degree of treatment, biofilters require approximately three times less aeration volume than activated sludge units, and twenty times less than trickling filters (Smith et al., 1992). In summary BAF systems are used for providing a treatment method for reducing the amount of organic carbonaceous material (BOD/COD), suspended solids and ammonia in wastewater.
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    Recent application and developments of the Biobead system
    (School of Water Sciences, Cranfield University, 1999-03-03) Cantwell, A. D. C.; Mosey, F. E.
    This paper describes the background of recent engineering changes to the BiobeadTM system. In particular known design pitfalls are described. The development of technically improved aeration and flow distribution methods are outlined. The extension of the system to combined C & N removal is outlined together with some recent experimental data which shows higher than expected de-nitrification performance. The benefits of a pre-filtration before the aerated part of the media bed is apparent particularly when removal of industrially derived COD is required to reach UWWT directives standards. This method also allows tertiary treatment of high influent solids whilst maintaining Ammonia removal.
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    Colne Bridge (Huddersfield) WWTW - Biopur plant process design and performance
    (School of Water Sciences, Cranfield University, 1999-03-03) Holmes, J.; Dutt, S.
    The complexity of the Huddersfield works and the issues addressed by the scheme design engineers are highlighted, including the need for a robust nitrification process due to the high levels of nitrification inhibition in the plant feed. Issues influencing the Biopur process selection are discussed and a detailed description of the Biopur process design is given, together with details on process commissioning and performance testing. Finally the plant performance to date is summarised together with a list of issues for consideration on future plants.
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    Development of a novel lightweight media for Biological Aerated Filters (BAFS)
    (School of Water Sciences, Cranfield University, 1999-03-03) Moore, R.; Quarmby, Joanne; Stephenson, Tom
    Clay has been foamed and extruded using novel technology, to produce a lightweight media called StarLight C. Altering the production process parameters allows control of the media diameter, density, strength, and surface roughness. In its application as a Biological Aerated Filter (BAF) media, a low density may be advantageous since this will reduce the minimum fluidisation velocity (Vmf) of the media. Consequently a lower liquid velocity will be required during filter backwashing, which could reduce the operating costs and increase the productivity of the reactor. This paper reports the performance of StarLight C and standard expanded clay (media A) as media in pilot scale BAFs treating settled sewage with hydraulic residence times between 58 and 96 minutes. The BAFs were backwashed every 24 hours at a liquid flow rate corresponding to 40% of the Vmf of the media. The BAF using StarLight C required approximately half the volume of backwash water needed by the BAF filled with media A. To optimise the performance of BAFs further the filter run time should be maximised. This requires the media size and voidage to be maximised without compromising filtration efficiency.
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    Industrial applications of Biological Aerated Filters
    (School of Water Sciences, Cranfield University, 1999-03-03) Rundle, Howard; Chen, Jeffrey J.; McCarty, Don
    Biological aerated filters (BAF's) are compact wastewater treatment reactors capable of achieving biological oxidation and solids removal in a single reactor. The basic principle of operation is that biomass grows on the surface of a submerged medium. Air is injected at or near the base of the medium. The effluent to be treated flows either upward or downward through the bed. Biological oxidation occurs during passage through the bed and suspended solids are retained within the bed. These solids are removed periodically by backwashing. The use of BAF technology is well known for treatment of municipal sewage. The application of this technology to industrial effluents is less well documented. In this paper the application of the TETRA ColOXTM BAF to treatment of effluents arising from paper making, from steel making, from plastics manufacture and from the electronics industry is described.
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    A new generation of Aerated Filter
    (School of Water Sciences, Cranfield University, 1999-03-03) Martin, J.
    The use of the activated sludge process is a very well known technology. It is and has been used very widely in full scale plants from its first development at the Davyhulme works in Manchester. However this process becomes very difficult to upgrade or to extend in order to ensure compliance with either more stringent discharge consent conditions or to achieve the same quality of discharge where increasing flows are the problem. This problem of upgrading or extension to existing works led OTV almost twenty years ago to develop the bio-filter process. This process consists of essentially biological filters operating either in the down flow or up flow mode, the main benefits of this system being they are compact in their space requirements, together with their ability to combine both filtration and aerobic/anaerobic bio degradation. They are used for the removal of suspended solids, COD, BOD, ammonia (and nitrate) either in the secondary or the tertiary treatment stage, plus with the use of a precipitating chemical, they can also be used for the removal of phosphates.