Use Of Aluminum Sulfate Research Articles

Risk minimisation of FGD gypsum leachates by incorporation of aluminium sulphate

The incorporation of aluminium sulphate to (flue gas desulphurisation) FGD gypsum before its disposal was investigated as a way to minimise the risk supposed by the high fluoride content of its leachates. Using a bath method the kinetic and equilibrium processes of fluoride removal by aluminium sulphate were studied at fluoride/aluminium molar concentration (F/Al) ratios in the range 1.75 10 − 2 –1.75 under the pH conditions (about 6.5) of FGD gypsum leachates. It was found that fluoride removal was a very fast process at any of the (F/Al) ratios subject of study, with equilibrium attained within the first 15 min of interaction. High decreases in solution fluoride concentrations (50–80%) were found at the equilibrium state. The use of aluminium sulphate in the stabilization of FGD gypsum proved to greatly decrease its fluoride leachable content (in the range 20–90% for aluminium sulphate doses of 0.1–5%, as determined by the European standard EN 12457-4). Such fluoride leaching minimisation assures the characterization of this by-product as a waste acceptable at landfills for non-hazardous wastes according to the Council Decision 2003/33/EC on waste disposal. Furthermore, as derived from column leaching studies, the proposed stabilization system showed to be highly effective in simulated conditions of disposal, displaying fluoride leaching reduction values about 55 and 80% for aluminium sulphate added amounts of 1 and 2%, respectively.

Synthesis of nanozeolite A from natural clinoptilolite and aluminum sulfate; Optimization of the method

The zeolite NaA was synthesized from natural clinoptilolite as Si source and aluminum sulfate or sodium aluminate as Al source. The use of aluminum sulfate for the synthesis of zeolite A has not been reported in the literature. This study presents as the first time a synthesis approach in which the low cost and available source is used to prepare zeolite NaA. These nano particles of zeolite were prepared at different conditions in autoclave and a mixer was designed specifically for this purpose. The synthesized zeolites were characterized by instrumental analysis methods, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and wet chemical analysis by atomic absorption spectroscopy (AAS). Cation exchange capacity (CEC) and loss on ignition (LOI) have been also measured on the prepared samples. The influences of different parameters such as reaction time, temperature, initial gel concentration, mechanical stirring and drying conditions on the improvement of the final products were experienced and the procedure for the efficient synthesis of zeolite NaA was optimized with available quality control tests. Solubility of clinoptilolite as the Si source in alkaline solutions was also investigated.

Use of zeolitised coal fly ash for landfill leachate treatment: A pilot plant study

Treatment of municipal solid waste (MSW) landfill leachate generally results in low percentages of nutrient removal due to the high concentration and accumulation of refractory compounds. For this reason, individual physical, chemical and biological processes have been used for the treatment of raw landfill leachate and sometimes for the mixture of domestic wastewater and landfill leachate. In this work, the possibility of treating landfill leachate was tested in a bench-scale pilot plant by a two-step method combining adsorption and coagulation–flocculation. Zeolite synthesized from coal fly ash, a by-product of coal-fired power stations, was used in this study both as a decantation aid reagent and as an adsorbent of COD and NH 4–N. The coagulation–flocculation step was performed by the use of aluminium sulphate and a polyelectrolyte (ACTIPOL A-401). The leachate was collected directly from a storage unit of the organic fraction of MSW, before it was composted. For this reason the raw leachate was diluted before treatment. The sludge was recirculated to enhance the removal efficiency of nutrients as well as to optimize flocculant saving and to decrease sludge production. The results showed that it is possible to remove 43%, 53% and 82% of COD, NH 4–N, and suspended solids, respectively. Therefore, this method may be an alternative for ammonium removal, as well as a suitable pre- or post-treatment step, in combination with other processes in order to meet regulatory limits.

The role of dissolved aluminum in silica chemistry for membrane processes

The use of aluminum sulfate (alum) coagulation prior to reverse osmosis (RO) treatment has been shown to be problematic. Membrane fouling was theorized to occur through soluble aluminum (Al 3+) reacting with ambient silica (H 4SiO 2) to form kaolinite (Al 2Si 2O 5(OH) 4) within the RO unit. Chelating agents (citrate at 34 mg/L and ethylenediaminetetraacetic acid [EDTA] at 16 mg/L) were tested for their efficacy in controlling aluminum silicate fouling. The results of bench-scale testing demonstrated that both citrate and EDTA did control aluminum silicate formation, citrate more so than EDTA. Additional aluminum-based fouling was encountered when a commercial, phosphonate-based antiscalant — used to control barium sulfate scaling — reacted with the excess aluminum despite the presence of either citrate or EDTA.

Plywood Mill Water System Closure by Dissolved Air Flotation Treatment

In plywood industry water is mainly needed for soaking the logs. Dissolved air flotation with chemical precipitation was found to be a suitable treatment method for the soaking basin overflow of a plywood mill using birch as raw material. According to pilot treatment studies over 90% reductions of the suspended solids are possible with a hydraulic surface load of 6.5 m3/(m2h). In subsequent experience in full scale following reductions have been achieved: suspended solids 93%, BOD7 50%, CODCr 57%, P 92% and N 52%. Two-thirds of the flotation treated water is led to flue gas scrubbers and circulated back to the soaking basin. Optionally water can be led to the heat recovery, too. One-third of the flotation treated water is disposed of as the mill effluent. Concentrations of organic matter in the system have been reduced after the addition of flotation indicating the possibility of further closure. However, due to the use of aluminium sulphate in coagulation, aeration is needed for sulphate reduction prevention. Further closure of the water system is possible in the future if the heat recovery is renovated, preventing the increase of the water temperature (now 37°C) which otherwise might cause occupational safety hazards.

Plywood mill water system closure by dissolved air flotation treatment

In plywood industry water is mainly needed for soaking the logs. Dissolved air flotation with chemical precipitation was found to be a suitable treatment method for the soaking basin overflow of a plywood mill using birch as raw material. According to pilot treatment studies over 90% reductions of the suspended solids are possible with a hydraulic surface load of 6.5 m 3 /(m 2 h). In subsequent experience in full scale following reductions have been achieved: suspended solids 93%, BOD 7 50%, COD Cr 57%, P 92% and N 52%. Two-thirds of the flotation treated water is led to flue gas scrubbers and circulated back to the soaking basin. Optionally water can be led to the heat recovery, too. One-third of the flotation treated water is disposed of as the mill effluent. Concentrations of organic matter in the system have been reduced after the addition of flotation indicating the possibility of further closure. However, due to the use of aluminium sulphate in coagulation, aeration is needed for sulphate reduction prevention. Further closure of the water system is possible in the future if the heat recovery is renovated, preventing the increase of the water temperature (now 37°C) which otherwise might cause occupational safety hazards.

Effect of Dry Storage on Bacterial Counts in Stems of Cut Rose Flowers

The number of bacteria in the basal 5 cm of the stems of cut rose flowers (Rosa hybrida L. cv. Sonia) stored in water for 1 to 4 days was positively correlated with the number of bacteria in the water. Subsequent dry storage of the flowering rose stems resulted in an increase in the number of bacteria in the stems, similar to that occurring in stems that were held in water. Low temperatures during dry storage (SC) reduced the reproduction rate of bacteria in the stems. Use of aluminum sulfate (0.8 g-liter-`) during the rehydration period before dry storage limited the number of bacteria in the stems and prevented their subsequent increase during dry storage.

The use of aluminium sulphate to control algal blooms and chironomids in Jackadder Lake, Western Australia

The use of aluminium sulphate to control algal blooms and chironomids in Jackadder Lake, Western Australia

The Elimination of Mineral Micropollutants

Mineral micropollutants in waste waters and drinking water are essentially composed of heavy metal salts. Their elimination, when present in trace quantities, is discussed in this paper. The techniques, which water treatment facilities can use, necessitate preclarification in open basins (efficiency varying between 20 and 90%), elimination by filtration, with efficiencies depending largely on preoxidation but particularly on coagulation-precipitation and related techniques. Our investigations, as well as certain literature data, demonstrate the predominating importance of contact between water and sludges in decanters-clarificators. Thus, Jar tests often yield only a poorly representative result of the elimination of heavy metals by coagulation-flocculation-decantation. As to the use of aluminium sulphate, for example, the elimination rates mentioned relating to the elimination rate or % removal in laboratory experiments, in pilot tests with sludge beds and in treatment plants respectively are as follows: Fe: 100, 95, 100; Mn: 4, 38, 97; Cu: 91, 83, 85; Cr: 29, 8, 83; Cd: 21, 29, 96; Ni: 0, 20, 50; Co: 0, 16, 51; Pb; -, 52, 61. It should be noted that treatment in plants is much more elaborate (oxidation by chlorine dioxide, application of activated silica and a one hour contact time with the sludge bed) than in pilot experiments (15 minutes contact time and a sludge bed without activated carbon). The oxidation state of metals plays an important role in techniques for their elimination by the usual methods such as coagulation-flocculation-decantation as well as in coprecipitation phenomena of Fe and Mn for example. The method of alkaline precipitation, in which the pH value needed is obtained by addition of lime, results in elimination rates over 80% and generally far over 90%. This method uses at the same time direct precipitation and coprecipitation in a calcium carbonate/magnesium oxide matrix. Ion exchange gives highly variable elimination results according to the ion present and its concentration. In practice, strong cation exchange resin are generally applied. In treatment plants, adsorption on carbon allows an overall yield of 50-100% removal of the metal concerned, provided that preoxidation and sufficient contact times are allowed. The experimental distinction of the specific effect due to adsorption is difficult, but according to our studies, adsorption occurs to a small extent only in the majority of cases. 30-50% of the remaining traces are eliminated by infiltration of purified waters underground, where a levelling of concentrations also occurs. In addition to the investigations presented, studies still being carried out demonstrate a sufficient stabilization of heavy metals immobilized with lime in order to allow them to be dumped in the environment without risk. This method seems confirmed as a method of choice in treatment of waste waters loaded with heavy metals.