Coagulation Diagram Research Articles

Biorefinery of peanut shell agroindustrial lignocellulosic waste for synthesis of a natural coagulant applied in the treatment of dairy wastewater

Agro-industrial lignocellulosic residue from peanut shell was used to obtain a natural coagulant, cationic hemicelluloses (CH), adding value to the residue through means of biorefinery. The hemicellulose was applied, after its cationization by etherification reaction in alkaline medium with ETA, as a natural coagulant in the treatment of synthetic dairy effluent (SDE). FTIR showed an increase of the methyl group band in 1480 cm-1, degree of substitution DS 0.38 ± 0.05 and the positive zeta potential of +13.1 ± 0.5 mV CH indicating the insertion of ETA in the structure hemicelluloses whose zeta potential was negative of ‐11.4 ± 0.6 mV. The evaluation of the CH was performed with jartest on turbidity, apparent color, and COD for a pHcoagulation range 5–11 and dosages from 50-500 ppm. Coagulation diagrams were determined using the data spatial interpolation method of the adapted Kringing regression model. The maximum performance of CH of SDE by sedimentation and DAF occurred at 50 ppm and pH 11 with turbidity removal efficiency, true color and chemical oxygen demand (COD) of 84.74%/87.48%, 98.75%/99.37% and 99.89%/93.38%, respectively. Flake morphology was analyzed through the application of an image capture non-intrusive method indicated low particle aggregation, with fractal dimension (Df) of the flakes stabilized in the range of 1.68–1.83 ± 0.020 in 15 min with a predominance of flakes with first-class flake diameters (0.022–1.20 mm) for all dosages. That explains the slower sedimentation and occurrence of smaller dispersed flakes which favored subsequent solid-liquid separation by DAF.

Investigation of new natural coagulant - cationic hemicellulose associated with cationic tannin - for coagulation/dissolved air flotation (C/DAF) in the treatment of industrial effluent

The use of plant-based coagulants (natural coagulants) in wastewater treatments has potential advantages over the inorganic coagulants used commercially. This study evaluated organic coagulants cationic hemicelluloses (CH) synthesized from peanut shell and associated with commercial cationic tannin (TSG) for use as the primary coagulation/flocculation treatment, followed by solid-liquid separation via sedimentation/flotation by dissolved air (DAF). The assay was carried out in a jar test on effluent from a multinational industry in the grain processing sector, located in the city of Uberlândia-MG. Coagulation diagrams were determined using the data spatial interpolation method of the Kringing regression model and the Tukey test was used to assess the difference in the results obtained. The optimum removal points of turbidity removal efficiency (TRE), greater than 98%, were achieved for the TSG/CH association with 200 mg L-1 (pH 10.72), 350 mg L-1 (pH 9.72), 500 mg L-1 (pH 9.56) in sedimentation. For the separation by DAF, the association of TSG/CH resulted in TRE values greater than 95% at dosages of 350 mg L-1 (pH 9.59) and 500 mg L-1 (pH 7.92). Furthermore, the results indicate that the associated use of TSG/CH, a coagulation aid, favored the coupling of the DAF bubble-particle, resulting in a smaller volume of sludge. In addition, CH expanded the action of TSG to the basic region.
 Keywords: agroindustry residue, natural organic coagulants, primary physical chemical treatment.

Performance of cationic hemicelluloses arising from peanut shell residue from agroindustry in application as primary coagulant in physical-chemical treatment of dairy wastewater

Cationic hemicelluloses (CH) are increasingly studied as an alternative to the use of inorganic coagulants. However, the CH has been used as coagulation aids. In the present study shows its potential to be used directly as a coagulant in a physical chemical treatment of synthetic dairy wastewater (SDW). Hemicelluloses were cationized by etherification reaction in alkaline medium with ETA. FTIR indicated cationization by increase of the methyl group band (1475 cm−1), supported by theoretical analysis. CH elemental analysis showed 1.92% (±0.09) of nitrogen and degree of substitution (DS) of 0.32 (±0.01). Turbidity, apparent color, TSS, COD and BOD5.20 was performed in a jartest with coagulation pH (5–11) and dosages range (100–900 ppm). Coagulation diagrams were determined for spatial interpolation by Kringing regression model. The optimal point selected occurred at the dosage of 400 ppm (coagulation pH 9.00 and 7.38), promoting removals for CH/TSG, respectively, of: 94.79%/98.67% (turbidity); 56.72%/65.21% (apparent color); 79.76%/97,22% (TSS); 47.83%/62.50% (COD) and 73.93%/62.39% (BOD5.20). The flakes morphology was analyzed by the image capture non-intrusive method. Fractal dimension (Df) of the flakes stabilized after 10 min at values of 1.319 (±0.020) and 1.871 (±0.001), with range diameters of 0.023–0.254 mm and 0.032–5.718 mm, for CH and TSG, respectively. Consequently, CH are a promising alternative for application as primary coagulants, provided removal of turbidity, apparent color and organic matter, not altering the pH and not promoting addition of color in the SDW.

Avaliação de Aloe arborescens como coagulante para remoção de cor e turbidez em tratamento convencional de água

O uso de coagulantes naturais no tratamento de água é alternativo ao de sintéticos, possíveis causadores de toxicidade. Este trabalho avaliou a viabilidade do uso de extrato de babosa (Aloe arborescens) como coagulante para remoção de cor aparente e turbidez no tratamento convencional. Os ensaios foram realizados em jar test, com água bruta do rio São Tomás, estado de Goiás, Brasil, abrangendo os intervalos de 6.0 a 8.0 unidades de pH e de 0.025 a 10.0 mL L-1 de coagulante. Elaboraram-se diagramas de coagulação com as eficiências obtidas de cada um dos 72 pares de valores pH versus dose de coagulante e obtiveram-se remoções na água decantada de 36% para turbidez e 52% para cor aparente e na água filtrada de 68% para turbidez e 70% para cor aparente. As eficiências obtidas não foram suficientes para atender às exigências do padrão de potabilidade brasileiro para os parâmetros analisados.

Response surface methodology applied to tropical freshwater treatment

ABSTRACTThis paper presents the profits and disadvantages of the chemometrics approach instead of the one-factor-at-a-time (OFAT) coagulation diagram approach for tropical water physicochemical treatment. Central composite design associate to response surface methodology (CCD-RSM) is used to find the real best conditions for coagulant dosage and pH aiming at high-turbidity removal. The number of experiments needed to chemometrics model construction (12) is comparatively smaller than that used in the coagulation diagram (84), saving financial and environmental resources. Arguments for Water Treatment Plants (WTP) considering the replacement of coagulation diagram approach by the CCD-RSM approach in drinking water treatment are presented. Chemometrics models are all constructed on a free software platform, providing the best pH within the range 7.7–8.1, and the best coagulant dosage (polyaluminium chloride, PAC) between 2.0 and 3.1 mg Al2O3 L−1 (equivalent in mass). CCD-RSM provides a faster, lower-cost and more reliable alternative tool for WTP decision-making instead of the OFAT model, mainly for waters more affected by seasonal effects as can be seen in tropical and subtropical countries.

AVALIAÇÃO DA EFICIÊNCIA DE COAGULANTES COMERCIAIS PARA APLICAÇÃO EM SISTEMAS DE TRATAMENTO DE ÁGUA

A grande variedade de coagulantes permite que as Estações de Tratamento de Água busquem pelo reagente com melhor custo benefício para remover a turbidez da água bruta. Os principais objetivos deste trabalho foram avaliar a eficiência de remoção de turbidez em águas captadas em período de estiagem usando dois coagulantes comerciais, policloreto de alumínio (PAC) e o Tanfloc-SL, e realizar um estudo de viabilidade econômica levando em conta os gastos com coagulação e desinfecção. Diagramas de coagulação foram utilizados para avaliar a eficiência dos coagulantes em questão. Após a coagulação, algumas amostras foram filtradas e receberam uma carga de solução desinfectante. A eficiência máxima do PAC foi 94%, em pH 7 e dosagem de 28 ppm. Para o Tanfloc-SL, a eficiência foi 92%, em pH 6,95 e dosagem de 17 ppm. Quando comparadas as dosagens para remoção de 90% da turbidez inicial da água bruta, o consumo de Tanfloc-SL em relação ao PAC foi 54% menor. Por outro lado, o consumo de cloro foi 23,58% maior quando o Tanfloc-SLem relação ao PAC. Com os resultados alcançados neste trabalho, pode-se concluir que a subtituição do PAC pelo Tanfloc-SL gerará uma economia de 49,61% considerando os custos com coagulantes e desifetantes.

Construção e emprego de diagramas de coagulação como ferramenta para o monitoramento contínuo da floculação em águas de abastecimento

In this work coagulation diagrams were constructed from bench tests with the aid of jartest equipment in order to evaluate the remaining turbidity of water prepared by adding kaolin suspension (until reaching a turbidity of 25 ± 2 uT). The water was then subjected to coagulation, flocculation and sedimentation. Iron-free aluminum sulfate was used as a coagulant in dosages varying from 5 mg L-1 to 100 mg L-1 and coagulation pH varying from 3 to 9. Three different rates of sedimentation velocities were investigated (3.0; 1,5; and 0.5 cm min-1). Based upon the coagulation diagrams, satisfactory results for turbidity removal were observed with coagulation pH values between 6.5 and 7.5 and coagulant dosages greater than 15 mg L-1; high dosages of coagulant did not necessarily lead to lower remaining turbidity values. Turbidity removal efficiency was higher in lower rates of sedimentation velocities, reaching values less than 1 uT at the lowest sedimentation rate studied. The construction of coagulation diagrams using jartest equipment proved to be an effective tool for the optimization of the coagulation phases, flocculation and sedimentation in water treatment, producing flocs whose characteristics were more easily analyzed using techniques of continuous monitoring flocculation.

Optimization of process conditions in water treatment through coagulation diagrams, using Moringa oleifera Lam and aluminium sulphate

The construction of coagulation diagrams is provided to obtain colour, turbidity and compounds with absorption at UV254 nm removal by associating the coagulants Moringa oleifera Lam and aluminium sulphate to define the optimal conditions of the process in water treatment. Experiments were performed in jar test with several coagulant dosages and coagulation pH. Optimal conditions for raw water with high colour/turbidity were obtained at pH values ranging from 7.5 to 8. After filtration, three dosages of association aluminium sulphate—M. oleifera, 25 ppm/300 ppm; 20 ppm/350 ppm and 15 ppm/400 ppm, performed efficient removal of evaluated parameters, namely 97.7% plus for colour and turbidity and 68.2% for compounds with absorption at UV254 nm. Results showed that the use of coagulation diagram is useful since it provides development of tests in optimal conditions, depending on water initial characteristics. The association of coagulants aluminium sulphate—M. oleifera may be considered an alternative technique for conventional water treatment.

<b>Coagulation diagram using the <i>Moringa oleifera</i> Lam and the aluminium sulphate, aiming the removal of color and turbidity of water</b> - doi: 10.4025/actascitechnol.v35i3.12268

This work suggests the study of the coagulation diagram as a tool to verify the efficiency in removing color and turbidity of the water, using the Moringa oleifera Lam and the association of this biopolymer with the aluminium sulphate as coagulating agents. The assays were carried out in Jar Test, by varying the concentrations of coagulants and pH of coagulation. After the assays of coagulation/flocculation/sedimentation, samples were collected for the evaluation of the process efficiency. Best results were obtained at dose of 50 ppm of Moringa oleifera Lam. When associating the coagulants, the addition of the aluminium sulphate provided an increase in the efficiency of coagulation/flocculation, whose parameters of control used were color and turbidity. It was verified that the study of the coagulation diagram is useful, since it enables developing the assays in the optimal range, as a function of the raw water characteristics. The use of the Moringa oleifera Lam can be considered as an alternative technique to the conventional treatment.

Influence of the apparent molecular size of humic substances on the efficiency of coagulation using Fenton's reagent

This work used Fenton's reagent as a coagulating agent in the treatment of water samples with high true colour caused by humic substances (HS) extracted from peat. In addition, the effects of the apparent molecular size of HS on coagulation, flocculation and flotation were studied. To that end, four distinct water samples having the same true colour were prepared using HS with different molecular sizes, which were obtained by ultrafiltration fractioning. Through optimisation of coagulant dosage and coagulation pH, as well as posterior construction of coagulation diagrams for each water sample, it was verified that the sample prepared with the smallest apparent molecular size of HS was the most difficult to treat, requiring higher coagulant (Fenton's reagent) dosages than samples prepared with larger HS molecular sizes. Furthermore, filtration experiments after dissolved air flotation (DAF) were carried out in an attempt to simulate conventional treatment. The most representative results in filtered water were: apparent colour ≤ 3 HU; turbidity < 0.5 NTU; and residual iron concentration < 0.005 mg/L. The absorbance and total organic carbon values of filtered water samples were also very low, suggesting that the formation of disinfection by-products with chlorine would likely be insignificant.

Rates of the colloid coagulation in the presence of irreversibly adsorbing and non‐adsorbing polymers

AbstractWe have developed an analytic self‐consistent field theory of the effective interactions between nano‐ colloids mediated by irreversibly adsorbing polymers and non‐adsorbing polymers having a gyration radius much larger than that of colloids. By making use of this theory, we have calculated the potential of the polymer‐mediated forces for the above cases of polymer adsorption. On the basis of the obtained results for the polymer‐mediated potentials, we have obtained the stability ratio and rate of the coagulation in the presence of adsorbing and non‐adsorbing polymers. As a final result of our studies, we constructed the coagulation diagram that quantifies the combined effect of the Van der Waals and polymer‐mediated forces on the rate of colloid coagulation. Kinetic stability of the material‐specific colloid systems is discussed. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Mechanisms for removal of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from drinking water by conventional and enhanced coagulation

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are persistent organic pollutants that have been found to be ubiquitous in the environment. This article, for the first time, delineates removal areas of these polar compounds on a coagulation diagram that associates chemical conditions with different coagulation mechanisms. Variables considered were solution pH, coagulant dosage, coagulants (alum and ferric chloride), natural organic matter (NOM), initial turbidity, and flocculation time.The jar-test results show that conventional coagulation (alum dosage of 10–60 mg/L and final pH of 6.5–8.0) removed ≤20% of PFOS and PFOA. These chemicals tended to be removed better by enhanced coagulation at higher coagulant dosages (>60 mg/L) and (thus) lower final pH (4.5–6.5). A coagulation diagram was developed to define the coagulant dosage and solution pH for PFOS/PFOA removal. The results suggest that the primary PFOS/PFOA removal mechanism is adsorption to fine Al hydroxide flocs freshly formed during the initial stage of coagulation; increasing flocculation time from 2 to 90 min could not further improve PFOS and PFOA removals. Furthermore, the effect of NOM on PFOS/PFOA removal by coagulation was examined, and possible removal mechanisms were discussed.

Removal of humic substances with different apparent molecular sizes using Fenton’s reagent

Fenton’s reagent was used as a coagulating agent in the treatment of water samples with high true color caused by humic substances (HS) extracted from peat. The effects of the apparent molecular size of HS on coagulation, flocculation, and flotation were studied. Four distinct water samples having the same true colors were prepared using HS with different molecular sizes obtained through ultrafiltration fractioning. Through optimization of the coagulant dosage and coagulation pH and the construction of coagulation diagrams for each water sample, it was verified that the sample with the smallest apparent molecular size of HS was the most difficult to treat, requiring higher coagulant (Fenton’s reagent) dosages than samples prepared with larger HS molecular sizes. Furthermore, filtration experiments after dissolved air flotation were carried out to simulate conventional treatment. The most representative results in filtered water were: absorbance at 254nm ⩽ 0.016 cm-1; apparent color ⩽ 3 HU; and residual iron concentration < 0.005 mg L-1. The total organic carbon values of filtered water samples were also very low, always < 1.0 mg L-1.

Os benefícios da utilização de coagulantes naturais para a obtenção de água potável

This work aims to evaluate the benefits of obtaining potable water from natural coagulants, in function of the removal of the parameters color, turbidity and compounds with absorbing in UV-254 nm, using Tanfloc SS as a coagulant. To that end, coagulation/flocculation/sedimentation tests were performed in jar test with surface water featuring high color/turbidity. The coagulation pH (3.0 to 9.0) and the concentration of coagulant (10.0 to 60.0 mg L-1) were varied with the purpose of constructing coagulation diagrams and determine regions of best efficiency for removal of color and turbidity. The working conditions for the process of coagulation/flocculation/sedimentation were set according to preliminary tests. With the data obtained, the coagulation diagram was built using the 3DField 2.7.0.0 software. Based on these diagrams, for the coagulant Tanfloc SS, it is concluded that the best removals of the parameters studied, in their majority, occurred in the range of pH between 6.0 and 9.0 in all the concentrations studied. Thus, it was noted that the use of biodegradable organic coagulant is therefore a technical alternative to conventional coagulants, with public health benefits in addition to environmental preservation.

A methodology for optimising the removal of cyanobacteria cells from a brazilian eutrophic water

This work is concerned with optimizing the performance of the coagulation process in terms of the removal of intact cyanobacteria cells and saxitoxins (STX). The evaluation has been carried out through bench-scale jar tests to construct coagulation diagrams for aluminium sulphate, polyaluminium chloride (PACl) and ferric chloride. The test water was taken from a eutrophic surface source, collected at the inlet to the water treatment plant that supplies Ponta Grossa City, Brazil, at a time of high algal activity corresponding to a total of 108833 cells/mL of cyanobacteria. By constructing the coagulation diagram for turbidity, the optimal dose-pH conditions were used in subsequent tests involving both coagulation and sand filtration. In these tests the benefits of adding a cationic synthetic polymer and powdered activated carbon (PAC) to the overall treatment were investigated. From the results of the tests, the optimal dosages and pH for each coagulant, polymer and PAC were obtained corresponding to the lowest concentrations of cyanobacteria cells, STX and turbidity.

Tratamento de efluente de refinaria de óleo de soja por sistema de flotação por ar dissolvido

Propôs-se, neste trabalho, avaliar o desempenho de coagulantes combinados a três tipos de polieletrólitos (aniônico, catiônico e não iônico), através de Flotação por Ar Dissolvido (FAD), no tratamento de efluentes de refinaria de óleo de soja. O experimento, conduzido em escala de laboratório, ensejou não apenas encontrar, pelos diagramas de coagulação, a melhor faixa de pH e a melhor concentração de coagulante mas, também, as dosagens e os tipos de floculante, culminando em sua dosagem ótima. Para tanto, parâmetros, como tempo e gradiente de mistura rápida (1 min / 150 s-1), tempo e gradiente de mistura lenta (10 min / 40 s-1 - 5 min / 20 s-1), pressão na câmara de saturação (450 kPa) e velocidade ascensional (1,67 cm min-1) foram usados para a fase da flotação nos ensaios. Após o término dos ensaios, amostras do efluente tratado foram utilizadas para comparativo com o efluente bruto, obtendo-se um grau de remoção de demanda química de oxigênio (DQO) de 93,7 e 95,1% e de óleos e graxas (O&amp;G) de 94,2 e 99,8% para os ensaios 1 e 2, respectivamente. Apesar de sua excelente eficiência de remoção, o efluente tratado não apresentou características de reúso em torres de resfriamento, haja vista que sua DQO ficou muito acima de 75 mg L-1 O2.

Factors affecting the coagulation of seawater by ferric chloride

The combination of chemical coagulation and membrane filtration (e.g. micro- or ultra- filtration) represents an effective pretreatment for seawater desalination by reverse osmosis (RO). The removal of dissolved organic substances requires optimization in order to enhance treatment performance and minimize the risk of membrane fouling. For this reason a detailed understanding of the performance of hydrolyzing metal salts during coagulation is essential. In this study, coagulation experiments with ferric chloride were carried out using a standard jar test technique, and microfi ltration (MF) was simulated using a 0.45-µm membrane filter. Factors affecting the coagulation behaviour in terms of the removal of humic acids (HA) in seawater were investigated, namely the pH, coagulant dose, saline strength, HA concentration and presence of oil. Experimental evidence concerning the chemical bonding of high valence metal ions (Fe+3, Ca+2, Mg+2) were provided by fluorescence spectroscopy and its theoretical relevance to the coagulation processes has been discussed. Laboratory experiments were carried out over a wide range of iron dosage (16–2,500 µmol/L) and pH (4–9) and a coagulation diagram (iron dosage versus pH) defi ning domains of HA removal has been established with corresponding values for the electrical surface potential of aggregates. The maximum removal of HA (∼95%) in samples of Singapore seawater was found to occur at pH 5 and at a coagulant dose ≥150 µmol Fe/L. For water quality comparable to that of offshore seawater the coagulation performance in terms of HA removal was not strongly infl uenced by seawater strength, the presence of oil or the initial HA concentration within practical ranges of these parameters.

AVALIAÇÃO DA REMOÇÃO DE CIANOBACTÉRIAS E SAXITOXINAS DA ÁGUA BRUTA AFLUENTE À ETA PITANGUI DE PONTA GROSSA/PR, UTILIZANDO OS DIAGRAMAS DE COAGULAÇÃO PARA O CLORETO FÉRRICO E O REAGENTE DE FENTON

With the increasing water quality degradation on springs used to human supply, the responsible for the operation of Water Treatment Plants (WTP) is founding innumerous problems in the plant operational routine. Therefore, they need to adequate their treatment processes in function of the present reality, which no more suits to the WTP original project. In this context, this work had as objective evaluate cyanobacteria intact cells and cyanotoxins removal by means of coagulation diagram construction for ferric chloride and Fenton Reagent. The study water was proceeding from a eutrophized spring, collected at Parshall unit of the WTP that supplies Ponta Grossa City, Brazil. After the pair of values ‘coagulant dosage versus coagulation pH’ selection in the diagrams for each coagulant, it was tried to simulate the traditional treatment, realizing sand filtration experiments after decantation (bench scale), for the selection of an adequate cationic synthetic polymer and powder activated carbon (PAC) dosages, reaching total cyanobacteria removal, saxitoxins concentration below Brazilian standards, as well as turbidity values below 0.5 NTU.

GPE 2007 - Utilization of the Coagulation Diagram in the Evaluation of the Natural Organic Matter (NOM) Removal for Obtaining Potable Water

The natural organic matter (NOM) is a mixture of many organic compounds that can be dispersed in superficial water. The NOM is due to the compounds formed in the biologic degradation process of the vegetable organic matter and its interaction with the clay and the other hydrographic basin soil constituents, besides algae and other microorganism activity. Many researchers have obtained results that indicate that the coagulation/flocculation process is an effective process in the NOM reduction without committing the non-stabilization colloidal particles. So, with the intuit to guarantee a better final water quality in the water treatment plants, different studies were evaluated based on the coagulation diagram for obtaining the best concentration of the chitosan coagulant as function of the pH for the NOM removal for obtaining potable water. The data for the coagulation diagram construction will be obtained by a series of tests in a jar-test apparatus. Different concentrations of the coagulant solution (0.1% w/v of chitosan) will be studied. The pH will be varied (4.0 – 8.5) with sodium hydroxide solution (NaOH) and hydrochloric acid (HCl) 25 and 50%. The rapid mixture gradient, the coagulation time, the slow mixture gradient and the flocculation time will be maintained constant during this experiment. The process efficiency will be evaluated by the color, turbidity and compounds with absorption in UV-254nm removal. The best results of removal were found for the chitosan in the concentration of 1.0mg/L and pH between 4.0-5.0, approximately.

Emprego do reagente de fenton como agente coagulante na remoção de substâncias húmicas de água por meio da flotação por ar dissolvido e filtração

O reagente de Fenton foi empregado como agente coagulante no tratamento de água com cor verdadeira elevada (100 ± 5 uH) causada pela introdução de substâncias húmicas extraídas de turfa, empregando-se a flotação por ar dissolvido. Otimizou-se o par de valores dosagem de coagulante x pH de coagulação para posterior construção dos diagramas de coagulação, obtendo-se eficiências de remoção de cor aparente pouco superiores a 60%. Procurou-se simular um tratamento em ciclo completo, realizando-se ensaio de filtração em areia após flotação, obtendo-se efluente de excelente qualidade, apresentando cor aparente, turbidez e absorvância a 253,7 nm remanescentes menores ou iguais a 2 uH, 0,40 uT e 0,009 cm-1, respectivamente, e ferro total residual &lt; 0,005 mg/L e COD &lt; 0,001 mg/L.