PubMed · 14948135
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P D BERNARD. 1952. [Ionophoresis, complementary technic].. https://pubmed.ncbi.nlm.nih.gov/14948135/
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Laboratory and modeling studies were conducted to assess the potential performance of a permeable reactive barrier constructed of a natural zeolite material at the West Valley Demonstration Project in western New York State. The results of laboratory column tests indicated that the barrier material would be effective at removing strontium from groundwater under natural gradient conditions. Two one-dimensional contaminant transport models were developed to interpret the data. A single-solute retardation factor model provided good agreement with the column test data, but time-consuming extraction and analysis of the zeolite material was required to parameterize the model. A preliminary six-solute model was also developed based on the assumption of competitive cation exchange as the primary removal mechanism. Both models yielded similar predictions of the long-term performance of the barrier, but the cation exchange model predicted higher effluent concentrations during the first 1000 pore volumes of operation. The cation exchange framework has several advantages, including the ability to calibrate the model using only data from column effluent samples, and the ability to account for site-specific differences in the groundwater cation composition. However, additional laboratory work is needed to develop a suitably robust model.
The effect of volumetric flow rate, ranging from 5 to 45 Bed Volumes per hour (BV h(-1)) and temperature, ranging from 25 to 59 degrees C, during pretreatment of clinoptilolite on its effective capacity has been investigated. Pretreatment tests have been performed in an upflow ion exchange bed. Increased temperatures were found to increase the effective capacity of clinoptilolite. Effective capacity was maximal at low volumetric flow rates, indicating an influence of contact time and complete saturation of the zeolite bed at flow rates lower than 10 BV h(-1). Furthermore, a comparison between upflow and downflow operation at the same operating conditions showed that better results are obtained in upflow conditions, probably due to the better wetting of the material and the absence of liquid maldistribution.
Ammonium nitrogen was removed from pretreated domestic sewage using a natural zeolite-clinoptilolite, applying a column with downflow regime. The pretreated wastewater had an average total ammonium nitrogen (TAN) of 23 mg l(-1). Ion exchange was allowed to take place under normal sewage treatment plant conditions and tropical temperature setting. The sorption capacity of the natural clinoptilolite was studied with the column fitted to a chemically enhanced primary treatment (CEPT)-upflow anaerobic sludge blanket (UASB) system, operating at 33 degrees C. Optimal operational cation exchange capacity (CEC) of 14 g TAN kg(-1) zeolite was obtained for the zeolite granulometry of 1-2.5 mm in a reversible way. The treatment was done at 3.9 bed volumes (BV) per day, and breakthrough was attained after about 560 BV. Regeneration of exhausted zeolite was effected with a 25 g NaCl l(-1) salt solution, rendering the column amenable to reuse. Employing a 3-column test and bed contact times of 6, 2.6 and 1.1 minutes, the use of pretreated wastewater with average concentration of 38 mg NH4(+)-N l(-1) showed that the operational cation exchange capacity also depended on flow rate, with the removal efficiency decreasing from 95 to 47% with increase in the flow rate. Overall, the approach of removing TAN from digested sewage offers potential to recover the TAN from the domestic wastewater, thus minimizing the need for subsequent nitrification-denitrification of the whole water volume.