AWWA WQTC56935

The objectives of this study were to determine if a new particulate detection system has the sensitivity to detect a single fiber breach within a membrane system and to assess whether the presence of particles in the pathogenic size range could be determined. In addition, the objectives were to use at least two methodologies for simulating a cleaved membrane fiber and compare the results of each method using this new sensor technology. Two tests used in this study include cleaving an actual membrane fiber or fibers and a new fiber bypass method. The cleaving test has been used in the past and has many variables such as the location of the break, the nature of the break, the particulate characteristics in the filter influent, the age of the fibers, etc. A second test, the fiber bypass method, was designed to be a substitute for cleaving a fiber. This filter bypass test involves transporting influent water to the effluent stream immediately after the membrane cartridge. The execution of either of these integrity loss methods, while monitoring the effective change in the baseline of the monitoring system,will indicate if the particulate detection sensor is capable of detecting the respective failure. The testing was conducted under stringent conditions. The turbidity of the influent was very low, with measured values between 0.8 and 1.0 NTU. The temperature of the water was also very low, at 4 C. These two factors slow the flow through a broken fiber and make the detection more difficult. Even in these difficult conditions, the sensors detected changes from the fiber bypass and the actual membrane fiber cleaving tests. When the filter bypass testing was applied, the effects of between 0.5 and 3 broken fibers were simulated. The particulate detection sensor easily determined each of these changes. The membrane cleaving tests did not show the same trending response, indicating that the location of the cleaved fibers, the flow rate through the fiber, the pressure drop through the fiber, and the viscosity of the water all affected the results. However, in the end, the turbidity sensor did see the changes to the fibers. Additional testing was also performed with particle surrogates, in the size range of 0.028 to 5 um, to assess if an integrity loss could be qualified in regard to particle size. Preliminary results from this testing indicate that it may be possible to determine a particle size range in an integrity loss. The testing also demonstrated that sampling methods were critical when using a turbidimeter with highly enhanced sensitivity. When the detection sensitivity was increased, sampling methods were carefully applied to avoid contaminating the system. To date, the use of direct membrane processes to replace traditional filtration has been very successful in producing high quality drinking water in nearly all occurrences. It was demonstrated that the new particulate monitoring system discussed in this paper has the sensitivity to see a single fiber break in a membrane cartridge while providing a continuous monitoring approach for an entire membrane system. In addition, this system provides a direct and rapid means of isolating a membrane cartridge with an integrity problem. Includes 8 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

20

File Size:

1 file , 870 KB