Biological Nitrification within the fouling layer of Cross-Flow Micro-Filtration
With the fouling layer being established in most membrane filtration applications, a study of the possible benefits of the fouling layer was researched. This investigation was aimed at the determination of a viable nitrifying biofilm within the fouling layer of membrane filtration which could oxidize ammonia. The membrane used was a 0.2 µm ceramic tubular membrane used in cross-flow operation. Nitrifying organisms were inoculated into a bench top filtration apparatus to oxidize ammonia and the corresponding rates of ammonia oxidation were determined in two different operating modes. A filtering mode included the process of membrane filtration by enabling filtration and a non-filtering mode established the ammonia oxidation rate occurring in the apparatus without the process of filtration.
The comparison of the two modes showed a significant increase in the oxidation rate of the filtering mode. The ammonia oxidation rates seen in the six experimental runs corresponding to the surface of the membrane were: 0.94, 2.38, 3.81, 3.14, 6.24, and 9.30 (mg/l-hr-m2) compared to the internal surface of the bench top apparatus which were: 0.12, 0.12, 0.12, 0.11, 0.20, and 0.29 (mg/l-hr-m2) respective to each run. The differences in ammonia oxidation rate suggests that not only will viable nitrifying organisms grow within the fouling layer of a membrane they will grow at rate approximately 20 times faster than that seen occurring on the internal surface of the bench top apparatus.
Also discussed in the research is the ammonia oxidation rate as a function of cross-flow velocity and trans-membrane pressure. Varying the cross-flow velocity and trans-membrane pressure suggested that the organisms on the membrane surface may actually be undergoing nitrification from the influent end of the membrane to effluent end of the membrane.
Advisor:Dr. Robert Reis; Dr. Ronald Neufeld; Dr. Leornard Casson
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Keywords:civil and environmental engineering
Date of Publication:09/13/2004