The Effect of Potassium Permanganate on the Removal of Iron and Manganese from Ground Water

For the past three years or so, a gradual migration of iron and manganese deposits has been observed in the water mains to the west of the East Water Treatment Plant of Brookings, South Dakota. These deposits have been gradually migrating further westward from the plant (8). Routine analyses of the treated water from the East Plant indicate that the iron and manganese levels are within the USPHS recommended limits (9). Consequently, conclusive evidence that this plant is the source of the problem does not exist. However, the analyses are normally conducted on samples collected shortly before backwashing the filters. Thus, it is conceivable that enough iron and manganese could leak through the filters for a time after being placed back into operation from cleaning. If any bacteria exist in the filters, perhaps some iron and manganese may be getting through due to reduction from the insoluble to the soluble form in the filters. Also, maybe the concentrations in the filter effluent, even though below the USPHS recommended limits, are high enough to cause a build-up of deposits in certain stagnant locations in the mains. At any rate, the fact that the complaints initially were from users near the plant and, in later years, from further and further away, strongly suggests that the source of the trouble is the East Plant. The purpose of this investigation was to determine the effectiveness and optimum dosage of potassium permanganate for maximum removal of iron and manganese from the influent of the recarbonation basin, East Water Treatment Plant. Because the East Plant was designed specifically to remove iron and manganese by lime precipitation, a logical solution to the problem would be to increase the pH with a more complete precipitation of those ions. However, previous attempts to do this resulted in stability problems when this water mixed with that from the North Water Treatment Plant. Consequently, other possible solutions were considered. One of these potential solutions was 3 the addition of a strong oxidizing agent such as potassium permanganate to precipitate any unoxidized iron and manganese prior to filtration. To avoid disruption of treatment plant operations, it was decided to evaluate the effectiveness of potassium permanganate on a pilot scale. The effluent from the solids contact basin was selected as the point of application. Thus, the pilot units required were a recarbonation basin and a filter since these were the only units that followed the solids contact basin in the East Plant. Using a pilot plant having the same detention time, filter medium, and filter rate as the East Plant, the objectives of these studies were as follows: 1) To duplicate the performance of the East Plant in terms of iron and manganese concentration in the filter effluent, 2) To evaluate the effectiveness of feeding potassium permanganate on the filtered effluent iron and manganese concentrations, 3) To determine the permanganate dosage that will produce the lowest iron and manganese concentration in the filtered effluent, and 4) To design and estimate the cost of a permanganate feeding system for the East Plant

Levodopa Plus Occlusion Therapy versus Occlusion Therapy Alone for Children with Anisometropic Amblyopia

Purpose: This study aimed to compare the effects of short-term administration of levodopa plus occlusion therapy versus occlusion therapy alone in preschool children with hyperopic anisometropic amblyopia. Methods: This comparative interventional study included 40 eligible preschool children aged 6 to 7 years with hyperopic anisometropic amblyopia. The primary outcome measure was the logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity recorded at baseline, 3 weeks after the treatment initiation and 12 weeks after the treatment termination. The results were compared between the two groups. Results: No statistically significant intergroup difference was observed in baseline logMAR visual acuities (P = 0.92). The mean logMAR visual acuities of the amblyopic eyes were significantly better in both groups three weeks after the treatment initiation than the baseline (P < 0.01 in both groups). At 12 weeks after treatment termination, the logMAR visual acuities of the amblyopic eyes were significantly better than the baseline values (P < 0.001 in the placebo group and P = 0.09 in the levodopa group). Intergroup comparisons revealed no statistically significant difference in visual acuities 3 weeks after the treatment initiation (P = 0.11) and 12 weeks after the treatment termination (P = 0.10). Twelve weeks after the treatment termination, visual acuities regressed 0.037 logMAR in the placebo group and 0.042 logMAR in the levodopa group. These regression rates were not significantly different (P = 0.89). Conclusion: The results of this study provide evidence that adding short-term administration of levodopa to occlusion therapy in hyperopic anisometropic amblyopia offers no additional benefit in visual outcomes and provides no advantage in terms of the regression rate

The propionylation of cellulose and behaviour of cellulose tripropionate in solution.

An extensive heterogeneous kinetic study was carried out for acid catalysed propionylation of cotton cellulose. In this study a series of metal chlorides and sulphuric acid as catalysts were used, and the effect of temperature, solvent medium, propionylation solution composition, and catalyst concentration on propionylation were investigated. The degree of propionylation was determined by a saponification method and, where necessary, confirmed by infrared spectroscopy and microanalysis. The reaction process was described on the basis of an initial, first, and second stage. Up to 15% of the completed reaction appeared to take place in the initial stage which is suggested to be diffusion controlled. Whereas the first and second stages were shown to be nondiffusion ones since they obeyed pseudo first-order kinetics with respect to the reacting hydroxyl groups. A mechanism and transition state complex were proposed for the propionylation reaction. Acid catalysed propionylation conditions (catalyst, temperature, solvent or non-solvent and propionylation solution composition) were investigated for the preparation of high molecular weight cellulose tripropionate in the shortest time. Optimum conditions were found for both the solution and fibrous processes, with molecular weights of samples being determined viscometrically in chloroform. Solubility behaviour and solvent power of cellulose tripropionate in a large number of solvents was studied. The results were explained on the basis of possible types of interaction between solvent and polymer. Fractionation by the non-solvent addition method was employed for cellulose tripropionate, and the solvent-precipitant systems of propionic acid-water and acetone-petroleum ether were investigated. A satisfactory fractionation was only obtained in the case of the acetone-petroleum ether system. Number-average molecular weights of fractionated cellulose tripropionate samples were determined osmometrically. Solution viscosities of these samples were measured in chloroform from which the Mark-Houwink constants and molecular conformation parameters were obtained. The cellulose tripropionate chain appeared to be more flexible than that for cellulose triacetate. The applicability of gel permeation chromatography for measuring the molecular weight of cellulose tripropionate was considered using different methods of calibration with standard polystyrene samples. A hydrodynamic rather than Q-factor method of calibration was found to give the best agreement with osmometric molecular weights for sharp cellulose tripropionate fractions

The propionylation of cellulose and behaviour of cellulose tripropionate in solution.

An extensive heterogeneous kinetic study was carried out for acid catalysed propionylation of cotton cellulose. In this study a series of metal chlorides and sulphuric acid as catalysts were used, and the effect of temperature, solvent medium, propionylation solution composition, and catalyst concentration on propionylation were investigated. The degree of propionylation was determined by a saponification method and, where necessary, confirmed by infrared spectroscopy and microanalysis. The reaction process was described on the basis of an initial, first, and second stage. Up to 15% of the completed reaction appeared to take place in the initial stage which is suggested to be diffusion controlled. Whereas the first and second stages were shown to be nondiffusion ones since they obeyed pseudo first-order kinetics with respect to the reacting hydroxyl groups. A mechanism and transition state complex were proposed for the propionylation reaction. Acid catalysed propionylation conditions (catalyst, temperature, solvent or non-solvent and propionylation solution composition) were investigated for the preparation of high molecular weight cellulose tripropionate in the shortest time. Optimum conditions were found for both the solution and fibrous processes, with molecular weights of samples being determined viscometrically in chloroform. Solubility behaviour and solvent power of cellulose tripropionate in a large number of solvents was studied. The results were explained on the basis of possible types of interaction between solvent and polymer. Fractionation by the non-solvent addition method was employed for cellulose tripropionate, and the solvent-precipitant systems of propionic acid-water and acetone-petroleum ether were investigated. A satisfactory fractionation was only obtained in the case of the acetone-petroleum ether system. Number-average molecular weights of fractionated cellulose tripropionate samples were determined osmometrically. Solution viscosities of these samples were measured in chloroform from which the Mark-Houwink constants and molecular conformation parameters were obtained. The cellulose tripropionate chain appeared to be more flexible than that for cellulose triacetate. The applicability of gel permeation chromatography for measuring the molecular weight of cellulose tripropionate was considered using different methods of calibration with standard polystyrene samples. A hydrodynamic rather than Q-factor method of calibration was found to give the best agreement with osmometric molecular weights for sharp cellulose tripropionate fractions