Test filter systems are quite helpful to study the persistence of organic compounds in order to give hints for a better remediation of the environment. Therefore special test filters are used in the chemical industry in Germany for more than 20 years in order to determine the microbial bad degradable parts of the dissolved organic carbon (DOC) in the sewage outlets. These test filters can be considered as biological active fixed bed reactors which enable to simulate the biological degradation of organic compounds during an underground passage. It was shown by different investigations, that these test filter systems are well suitable for their expected tasks by determining group parameters. While looking for single compounds they were proven to be such good model systems. For good degradable compounds as e.g., 6-(methyl (phenylsulfonyl) amino)-hexanoic acid (HPS) it could be shown that these substances are microbially degraded on the test filter systems, while the more stable compounds, and an important example for that in Germany is naphthalene-1,5-disulfonic acid, showed a total different behavior. Therefore, the elimination of e.g. napthalene-1,5-disulfonic acid was investigated utilizing labscale filters containing Siran (porous, sintered glass) and activated carbon as support materials for bacteria. However, the different adsorption capacities of activated carbon and Siran had large effects on the measured substrate concentration. Thereby the test filter being run with Siran glass showed to be suitable for modeling the degradation behavior of single compounds during the underground passage. It can be concluded that those test filters can be utilized for studying organic compounds on their behavior as being relevant for water works by means of bad microbial biodegradability

Macro-porous cellulose carrier (AQUACEL) was applied for immobilization of denitrifying bacteria to develop a practical nitrogen removal system with high performance. When the immobilized cell was applied to denitrification under high nitrogen loading rate, flotation of carriers caused by the evolution of nitrogen gas resulted. To counter the problem of carrier flotation, new reactors using hydrodynamic jet flow and centrifugal force were developed. These new reactors distributed homogeneously the floating carriers, and complete denitrification was obtained even at high loading rate of 20 kg N/cu m-carrier/d. This AQUACEL system was effectively applied to denitrification of wastewater discharged from an eletroplating factory