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.