Trickling Filters

Design of Trickling Filters (TFs) and Nitrifying Trickling Filters (NTFs)

The removal of dissolved and particulate organic matter in domestic wastewaters in fixed film bioreactors, such as trickling filters, is limited by the rate of mass transport of organic matter through the falling liquid film into the biofilm. My research program over the past fifteen years has examined the impact of this on the performance and operation of trickling filters.

Computer models have been developed to predict: sBOD removal in plastic media trickling filters based on the size distribution of organic matter in the wastewater and the geometry of the media; oxygen transport to biofilms in trickling filters (which can limit aerobic sBOD removal); and the maximum rate of sBOD removal assuming no kinetic limitations. Biofilm reactors are also used for ammonia removal following removal of carbonaceous BOD. Therefore, the oxygen transport model was used to develop a nitrifying trickling filter model (NTF) to predict ammonia removal in NTSs. These models are now incorporated into design procedures as described in the Water Environment Federations Manual of Practice (MOP 8) and are available on the internet via this web site (see the side bar).

In order to better understand the size distribution of organic matter in wasdtewaters, an ultrafiltration procedure to separate soluble organic matter present in wastewater into apparent molecular weight (AMW) fractions using ultrafiltration (UF) techniques. Since a major fraction of dissolved organic matter in waters and wastewaters consists of molecules too large to be directly transported through bacterial membranes, our research projects focus on the breakdown of macromolecules ( such as polysaccharides and proteins) by suspended and attached microorganisms.

For related research on determining the biochemical oxygen demands of wastewaters, visit the web page on the HBOD test.

Trickling Filter Model

The file below is a self-extracting archive. You won’t need any special programs to extract the enclosed files. The files can be downloaded to your computer. To begin downloading, just click on a file. Copy the downloaded file into a suitable directory on your computer and run it using Windows 95, Windows 3.1, or in DOS. For DOS, simply type in the file name (no extension). LOGANTFM.EXE

Photographs of different types of structured, trickling filter plastic media


Examples of cross flow media, both of which were originally made by Munters Corp. Notice that adjacent sheets run in opposite directions, creating a flow pattern that crosses and creates mixing points. These two media have different surface areas (89 and 98 m2/m3) and are classified using the LTF models as XF-89a and XF-98b.

Example of vertical flow medium. This particular plastic module was made by BF Goodrich and contains two different faces: one has straight and curved vertical faces (as shown) but the other side is a flat sheet. This medium has a surface areas of 89 m2/m3 and is classified using the LTF model as VF-89b.

Example of another type of vertical flow medium. This plastic module was made by Surfpac. Notice the highly curved surfaces which act to increase the detention time in the medium verus that possible with just a flat face. This medium has a surface areas of 89 m2/m3 and is classified using the LTF model as VF-89c.

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