Coagulant Aluminum Sulfate Research Articles

Effects of several water quality parameters on arsenic removal by coagulation: laboratory experiments and a pilot-scale study

In laboratory experiments a traditional drinking water treatment method, coagulation/flocculation followed by solid/liquid phase separation has been applied in order to decrease arsenic concentration below 10 μg/L (which is the new Hungarian standard for arsenic). The goal of the research work was to examine the transition of the dissolved arsenic to solid form, to determine the factors which have significant effect on arsenic removal efficiency. The organic content of the water highly affected the arsenic removal process. The difference in the required coagulant dosage can be order of one magnitude depending on the organic content of the water. The phosphorous content also increases the required coagulant dose, since ferric phosphate precipitates are formed, decreasing the amount of coagulant available for arsenic removal. pH also proved to have significant influence when experiments were carried out at wide pH range. However, under more realistic conditions (pH is between 7.5 and 8), the effect of pH was not that significant. The inorganic carbon content at some extent favors the liquid/solid transition of arsenate, since it contributes to the buffering capacity of the water, therefore enhances the metal hydroxide formation process. However, the excess inorganic carbon has disadvantageous effect, since it competes with the arsenate ions for the free sites of metal hydroxides. Two oxidants (chlorine and potassium permanganate) and two coagulants (ferric chloride and aluminum sulfate) were studied in pilot scale experiments. The pilot plant was operated at Hajdúbagos, where the arsenic, iron and manganese concentration of the raw water is above the standard. In the experiments it was found the potassium permanganate + ferric chloride combination was the most efficient.

Aplicação de polieletrólitos sintéticos na clarificação do extrato aquoso de estévia

The extract of stevia leaves is usually dark which demands a clarification in order to be accepted by sweetener consumers. One of the using techniques is the decantation, which requires the use of effective products for best results. In the market, flocculant products are available, such as: NOVUS TM CE2666 (cationic) and BETZDEARBORN TM F11 (anionic). When these products are used at a certain level of concentration, satisfactory results of decantation and consequent clarification are provided. The aim of this paper was to compare the performance of the best polymers by removal percentage (color and turbidity) and by the decantation speed. A Jar Test device was used and the concentration of coagulant (aluminum sulfate) and of polyelectrolytes were varied, as well as pH at 8,0, 9,0 and 10,0. Calcium oxide was applied in this phase. The best condition was obtained when the anionic polyelectrolyte was used, reaching a turbidity removal of 97%.

Comparison of Efficiency between Poly‐aluminium Chloride and Aluminium Sulphate Coagulants during Full‐scale Experiments in a Drinking Water Treatment Plant

The efficiency of poly‐aluminium chloride (PACl) and of aluminium sulphate (alum), two commonly applied coagulant agents, was studied comparatively in this work, during full‐scale experiments in a drinking water treatment plant. The removal of suspended solids (turbidity) and the residual aluminium concentrations were carefully monitored and they were used for the evaluation of effectiveness for each coagulant, as well as for the determination of optimal operative conditions. Two alternative treatment processes were examined: (a) the conventional coagulation‐flocculation‐sedimentation process, followed by gravity filtration through sand filter beds, and (b) the direct filtration process, i.e., coagulation‐flocculation and sand filtration, but without the intermediate sedimentation step. PACl proved to be a more efficient coagulant than alum, as lower dosages of PACl, about 1.35 mg Al/L in this case, resulted to the production of treated water with low turbidity and residual aluminium content. In addition, the direct filtration process through dual sand‐anthracite filter beds was found to be equally sufficient, as the conventional one, i.e., when applying the sedimentation step; in this case, 0.70 mg Al/L of PACl resulted in low turbidity water (around 0.1 NTU) and residual aluminium content (lower than 150 µg/L). In addition, the operation time of filters was extended to more than 24 hours.

Efeito da concentração de coagulantes e do pH da solução na turbidez da água, em recirculação, utilizada no processamento dos frutos do cafeeiro

Com o objetivo de determinar a dose e a faixa de pH dos coagulantes sulfato de alumínio (SA), sulfato ferroso clorado (SFC), cloreto férrico (CF) e extrato de semente de moringa (ESM), que proporcionassem maior eficiência na remoção da turbidez na água residuária da despolpa de frutos do cafeeiro (ARDC), após serem efetuadas cinco recirculações, foram conduzidos ensaios de coagulação/floculação utilizando o aparelho "Jar-test". Todos esses coagulantes foram avaliados nas concentrações de 0; 0,5; 1,0; 1,5; 2,0; 2,5 e 3,0 g L-1. No caso da solução preparada com ESM, as doses utilizadas foram: 0; 10; 20; 30; 40; 50 e 60 mL L-1. O pH da solução em teste foi alterado, utilizando-se do hidróxido de sódio (NaOH), na concentração de 0,3 mol L-1, sendo avaliadas as faixas de 4,0 a 5,0; 5,0 a 6,0; 6,0 a 7,0 e 7,0 a 8,0. No ensaio de coagulação/floculação, o ESM proporcionou maior remoção de SS (sólidos em suspensão) da ARDC com a dose de 10 mL L-1 e pH de 4,27 (natural). Para os coagulantes SA e CF, os melhores resultados foram obtidos com a concentração de 3 g L-1 e pH de 7,27 e, para o coagulante SFC, com a concentração de 3 g L-1 e pH de 4,27.

Clarification of kaolin suspension and turbid natural water in the presence of Praestols and aluminum sulfate and aluminosilicate coagulants

The kinetics of clarification of a kaolin suspension and turbid natural water in the presence of coagulants (aluminum sulfate and aluminosilicate) and flocculants (nonionic, cationic, and anionic Praestols) was studied in relation to the concentrations of coagulants and flocculants.

Sedimentation of Kaolin Suspension in the Presence of Praestol Anionic Flocculant and Aluminum Polyoxychloride and Sulfate Coagulants

The kinetics of sedimentation of kaolin suspension in the presence of coagulants (aluminum polyoxychloride and sulfate) and Praestol anionic flocculant was studied, as influenced by the concentrations of coagulants and flocculant, mode and time of their addition into the suspension, composition of the coagulant mixture, and chemical structure and conformation of flocculant macromolecules.

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.

Effect of phosphate on removal of humic substances by aluminum sulfate coagulant

The presence of humic acid may change the way phosphate is absorbed or stabilized by soil and how it influences the growth of plants. The binding of phosphate with the humic substance requires bridging between phosphate ions and humic acid by metal ions, such as aluminum or iron ions. The bridging reaction can take place in peat and allophane soil under acidic conditions, altering the effectiveness of the phosphate in soil. Whether ternary phosphate–metal–HA complexes are actually formed has not yet been verified. This study considers variation in fluorescence intensity (FI) under various coagulation conditions to assess the mechanism by which humic acids and phosphate react with aluminum ions. A bond between the functional group of the humic acid and the electron-releasing group of the phosphate will enhance the florescent intensity of humic acids. Consequently the removal efficiency of humic acid, measured by florescence, declines as the phosphate concentration increases at low pH. This observation suggests that at low coagulation pH, the positively charged aluminum species can be used to bridge between the phosphate ion and the humic acid molecules.

Return sludge employed in enhancement of color removal in the integrally industrial wastewater treatment plant

In this study, the recirculation of chemical sludge and integrated sludge were employed for enhancement of color removal in an integrally industrial wastewater treatment plant. The jar test was conducted for simulating chemical coagulation process with different coagulants, aluminum sulfate and polyaluminum chloride (PACl), after different activated sludge systems (with air or high-purity oxygen). The results showed that with sludge recirculation the process of coagulation for the color removal has up to 35% enhancement in comparison with no sludge recirculation. Meanwhile, the color removal enhancement of coagulant aluminum sulfate was approximately 2 to 3-times the color removal enhancement of coagulant PACl at the optimum ratio of return sludge. In coagulation process with influent color of 1220 true color unit (TCU), the optimum dosage of return sludge was 3010 mg/L, when coagulant PACl or aluminum sulfate was employed. In coagulation process with influent color of 536 TCU, the optimum dosages of return sludge were 2340 and 4680 mg/L using PACl and aluminum sulfate, respectively.

A Field Based Evaluation of Household Arsenic Removal Technologies for the Treatment of Drinking Water

Seven household treatment technologies for the removal of arsenic (Alcan, BUET, DPHE/DANIDA, Garnet, Sono, Stevens, Tetrahedron) were each evaluated using water from 63 different tube wells taken from 3 different regions of Bangladesh. The technologies that were evaluated were chosen from those that appeared user friendly, readily available and whose promoters were open to participate in the study. Arsenic concentrations in feed and treated waters were analysed by the PeCo 75 arsenic field test kit, AA-hydride generation and ICP-AES. Feed water arsenic concentrations were found to be up to 600 µg l−1. The more advanced treatment methods using: activated alumina (Alcan, BUET); metallic iron (Sono); anionic exchange resin (Tetrahedron) and iron coagulation (Stevens) were found to be most easily used and efficiently reduced arsenic concentrations to below the Bangladesh drinking water standard (0.05 mg As l−1). The use of aluminium sulphate coagulants and permanganate oxidants in the DPHE/DANIDA technology introduced unacceptably high concentrations of aluminium and manganese into the treated waters and are not recommended in household water treatment applications. While arsenic concentrations were initially considered to be of paramount importance, it became clear that such technologies can increase the risk of bacterial contamination in the treated water and this needs serious consideration as this could create a hazard much greater than the arsenic contained in the water. Ground waters sampled during the course of this study were mostly found to be bacteria free. To minimize any risks relating to bacterial contamination the addition of hypochlorite or the boiling of water is necessary.

Coagulation and Flocculation Purification of Fat- and Protein-Containing Disperse Systems

Procedure for treatment of wastewater with a coagulant (aluminum sulfate) and anionic flocculants to remove fats and proteins was studied The purification efficiency was evaluated from the flocculation parameters.

Removal of Natural Organic Matter by Coagulation-Flocculation: A Pyrolysis-GC-MS Study

The removal of the natural organic matter (NOM) in the Seine river water sampled at Le Pecq (France) was carried out by using three coagulants: ferric chloride, aluminum sulfate, and aluminum polychlorosulfate (PACS). The efficiency of the coagulation-flocculation process depended on the pH. The best results were obtained at pH = 5.5 with ferric chloride and pH = 7.0 with the Al based coagulants aluminum sulfate and PACS.The composition of NOM in the raw and clarified water as well as in the flocs was analyzed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Using this technique on the flocs formed with ferric chloride, a selectivity of this coagulant for polyhydroxyaromatics (PHA) was shown. A preferential binding was also observed between PACS and polysaccharides (PS). No such trend could be observed with aluminum sulfate. These results were confirmed and refined by Py-GC-MS analyses on the different mass fractions of the clarified water obtained by gel permeation chromatography.

Chemically assisted phosphorus precipitation: Effects on anaerobic digestion and ‘Aercon’ sludge thickening

Abstract Removal of phosphorus by chemically assisted primary sedimentation was assessed and its effects on anaerobic digestion and Aercon consolidation were examined. Phosphorus removals in excess of 96 and 99% were evident with the addition of aluminium sulphate and ferric chloride coagulants respectively. Further improvement of phosphorus removal was minimal with the application of a polymeric flocculation aid in combination with ferric chloride only. No adverse effects on amenability to anaerobic digestion were observed for coagulant sludges. Subsequently, ‘Aercon’ treatment was able to thicken ferric chloride and aluminium sulphate sludges satisfactorily thereby proving ‘Aercon’ applicable in such situations.