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1.
Several coagulants/flocculants have been studied in order to remove the color and turbidity of raw water, employing natural ones demonstrated advantages in relation to chemicals. Moringa oleifera Lam is a natural polymer that has been gaining prominence in water treatment. It acts as a clarifying agent, providing a cationic protein that destabilizes the particles contained in a liquid medium. The main objective of the present work is to study the efficiency in terms of removing color and turbidity of raw water in order to obtain drinking water. For this purpose, different coagulant solutions were obtained utilizing three solutions of KCl in different concentrations (0.01, 0.1, and 1 M) and pure water combined with M. oleifera Lam seed. Each coagulant solution obtained was studied with concentrations ranging from 50 to 600 ppm of Moringa in solution. The pH was varied (4.0, 6.0, and 8.0) with 25% and 50% sodium hydroxide solution (NaOH) and hydrochloric acid (HCl), respectively. The tests were conducted with the “Jar Test Device” and the efficiency of the process was evaluated regarding the reduction of color and turbidity. The best results were found employing the coagulant solutions extracted with 1 M salt solution, pH 8.0, and different concentrations of coagulant solution. It is important to explain that the best results were in various concentration ranges, as the concentration of protein in solution becomes higher, the greater is its power as a coagulant. The lowest content of protein was found in the solution extracted with water, which consequently had the lowest values of color and turbidity removal.  相似文献   

2.
The occurrence of fluoride in groundwater has been reported in many countries, mainly because the excess fluoride in drinking water can lead to dental or skeletal fluorosis. Fluoride removal by coagulation with Moringa oleifera seeds, followed by separation with membranes, was investigated in this work. Artificially fluoridated water, at a starting fluoride concentration of 10?mg?L?1, was submitted to a coagulation process with aqueous extracts of M. oleifera seeds. The coagulation process was followed by ultrafiltration with membranes at different pressures. The coagulation process with 2.5?g?L?1 of M. oleifera promoted a reduction of 90.90?% in the fluoride content of the treated water, making it possible for poor communities to consume this water. It is noteworthy that the combined coagulation/filtration process using raw coagulant showed the highest values of colour and turbidity, which, however, were still below the limits set for drinking water by Brazilian legislation. The advantage of proposing a sequential process using membrane separation is that it removes colour and turbidity, caused by the use of M. oleifera as a coagulant, resulting in water that meets potability standards.  相似文献   

3.
The textile industries are characterized as one of the biggest consumers of potable water and chemical products throughout its process, being responsible for the elevated wastewater generation with intense coloration and wide polluting potential. In this context, the present study proposes the development and application of a new coagulant material for textile wastewater treatment. The proposed coagulant (α-Fe2O3-MO) was composed by hematite nanoparticles (α-Fe2O3) obtained by a simple non-pollutant methodology, associated with Moringa oleifera (MO) seeds saline extract compounds. Coagulation/flocculation (CF) efficiency was evaluated by removal of physicochemical parameters such as apparent color, turbidity, and compounds with absorption at UV254nm (UV254nm) through CF tests carried out on Jar test equipment and sedimentation carried out in the presence and absence of external magnetic field (600 k Am?1). Kinetics sedimentation was from 0 to 90 min. The use of this new coagulant allowed the removal of 92.37% for apparent color, 91.43% for turbidity, and 46.09% for UV254nm, indicating that the proposed coagulant association was efficient in the treatment of this type of wastewater under external magnetic field with only 10 min of sedimentation. In addition, the resulting sludge from CF process was tested as base material for a new coagulant synthesis, demonstrating great reuse potential. Therefore, the new proposed coagulant, composed of α-Fe2O3 and the compounds present in the seed extract of MO, has applicability for textile wastewater treatment demonstrating high removal rate for all evaluated parameters with cost reduction in the proposed treatment for this wastewater.  相似文献   

4.
Attempt has been made to study the treatability of printing ink wastewatergenerated from an Indian currency printing press using coagulation-flocculation process. Coagulant agents, viz. ferrous sulphate, ferric chloride, aluminium sulphate and polyaluminium chloride were studied to select the most suitablecoagulant for effective treatment, and attain the optimum coagulant concentration. Cationic polyeletrolyte in conjunction with the most effective coagulant was also studied to assess its effect on floc settleability. Polyaluminium chloride (PAC) was found to be the most efficient coagulant, achieving removals of colour, suspended solids (SS), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) of 95.9–96.5%, 96.5–97.0%, 61.3–65.8%and 54.8–61.8%, respectively at an optimum concentration of 1500 mg L-1. Other coagulants, viz. ferrous sulphate, ferric chloride and aluminium sulphate did not show substantial removals of colour, BOD and COD, except suspended solids in comparison to the performance of PAC. Cationic ploylectrolyte in combination with PAC at an optimum concentration of 1500 mg L-1 of PAC and 1.0 mg L-1 of polyelectrolyte further improved the removal efficiency of various parameters studied, in addition to improving the floc settling rate, and reduction in quantity of sludge generation.Effect of rapid mixing intensity expressed as mean temporal velocity gradient (G), and mixing time (t) on flocculation was also investigated. Rapid mixing at an impeller rotational speed (n) of 300 rpm and mixing time (t) of 60 sec indicated good floc formation, which resulted in achieving velocity gradient of 821 s-1, and was found to be an optimum combination. This was also indicated by relatively high settling velocity of sludge formed and low residual colour in the supernatant. However, slow mixing beyond 5 min, adopted after initial optimum rapid mixing, indicated negligible effect on flocculation.  相似文献   

5.
Chitosan is a biodegradable cationic polymer that may be a potential substitute for aluminum salts in water treatment systems. In our study, we compared the coagulation performances of chitosan with those of coagulant mixtures of chitosan and aluminum sulfate and chitosan and poly-aluminum chloride, respectively. The coagulation efficiency was evaluated in terms of coagulant dosage, solution pH, settling velocity of flocs, floc diameter, and water turbidity. The optimum dosages for acid-soluble and water-soluble chitosan required for removal of a bentonite suspension (100 NTU) were only 1.25 and 1.50 mg/l, respectively, at a respective efficiency of 99.2% and 95.8%. The optimal dosage range for water-soluble chitosan was broader than that for acid-soluble chitosan. The coagulation of bentonite decreased with increasing pH when acid-soluble chitosan was the coagulant. In contrast, the coagulation efficiency of bentonite was not affected at pH 5?C9 when water-soluble chitosan was the coagulant. The mixing of chitosan with alum or PAC in a 1:1 mass ratio significantly improved the coagulation process in terms of preventing the occurrence of re-stabilization. The highest floc settling velocity occurred at a dosage of 5?C6 mg/l of the coagulant mixtures, which was also the highest coagulation efficiency. Given the relatively high cost of chitosan and the good coagulation performance of the coagulant mixtures, we suggest that a 1:1 mass ratio of chitosan mixed with alum or PAC may be an alternative method to the use of pure chitosan in water treatment systems.  相似文献   

6.
Two tannin-based coagulants have been tested on anthraquinonic dye elimination from aqueous solutions. Acquapol S5T, derived from Acacia mearnsii de Wild, and Silvafloc, derived from Schinopsis balansae, were found to be excellent agents in the destabilization of Alizarin Violet 3R dye and its elimination through coagulation from textile effluents. Both coagulants showed that high affinity to the dye molecule in a wide pH range and q values reaches significant levels (up to 0.5 mg mg???1) with reasonable low coagulant doses. Dye?Ccoagulant system presented a consistent behavior if studied under the statistical perspective of a design of experiments, where initial dye concentration and coagulant dose were the operating variables. Finally, both coagulants seemed to follow a predictable theoretical model under the Langmuir hypothesis with an accurate adjusted r 2 coefficient above 0.9.  相似文献   

7.
The pulp left after the extraction of juice from Citrus reticulate (kinnow), is a waste material, which was used as a potential sorbent for Cr(III) and Cr(VI) in the present study. The effect of experimental parameters such as pH, biosorbent dosage, biosorbent particle size, initial metal concentrations, temperature, shaking speed and sorption time on the Cr removal is apparent from the obtained results. The Freundlich isotherm and pseudo second order kinetic models fitted well to the data of Cr(III) and Cr(VI) biosorption by Citrus reticulata waste biomass. Effect of several pretreatments such as gases, natural coagulant and many other chemicals on Cr(III) and Cr(VI) sorption capacity of Citrus reticulata waste biomass was first time analyzed in the present study. The metal sorption capacity of Citrus reticulata waste biomass after a specific pretreatment was not only related to the nature of chemical but also strongly dependent on the oxidation state of the metal.  相似文献   

8.
The objective of this work was to optimize the synthetic dairy effluent (SDE) treatment using the central composite rotatable design (CCRD) and the Doehlert matrix to evaluate the adjustment of the models to the data, besides verifying if it is possible to find the same optimum point to the turbidity removal, chemical oxygen demand (COD), and UV254 compounds using two experimental designs. The coagulation and flocculation assays were made in jar test and the flotation in a flotatest in bench scale. For each experimental design, the effect of two organic coagulants was evaluated in the removal of turbidity, COD, and UV254 compounds of the SDE: the polyacrylamide (PAM) and the Tanfloc. The generated mathematical models in both experimental designs adjusted well to the data, showing a high capacity of prediction. To the PAM coagulant, the optimal point found in the CCRD design was 46.49 mg L?1 of coagulant in a pH of 6.53; in the Doehlert design, the optimal point in the CCRD was 48.40 mg L?1 of coagulant in a pH of 6.50. When Tanfloc was used, in the CCRD, the optimal point found was 40.42 mg L?1 of coagulant in a pH of 5.00 and, in Doehlert design, the optimum found was 37.57 mg L?1 in a pH of 5.05. It is concluded that, using a smaller number of runs, through Doehlert design is possible to find the optimal point really close to the obtained through CCRD in which are observed efficiencies of similar pollutant removal.  相似文献   

9.
A rapid titration method was developed for predicting the optimal coagulant concentration for making filled tofu. Cooked soymilk (350 mL, 20 degrees C) in a 400 mL beaker was stirred by a magnetic stirrer to form a swirl. The quick-acting coagulant solution (20.0 Brix) was added into the soymilk at 1.0 mL/min. The swirl depth decreased when the soymilk viscosity increased as a result of increasing the concentration of coagulant in the soymilk. At a suitable stirrer speed, the swirl finally disappeared but the soymilk still maintained rotation, and then the swirl reappeared after around 1 min. The critical point of coagulant concentration (CPCC) was calculated on the basis of the volume of coagulant consumed to get the swirl to disappear. The influences of several factors on the CPCC were investigated, including coagulant addition rate, soymilk temperature, soymilk concentration, soymilk volume, stir bar length, and container size. For validation, 33 soybean samples were used to determine their CPCCs and make filled tofus. The results indicated that CPCC was a characteristic parameter of soymilk and could be used as an effective indicator for predicting optimal coagulant concentration.  相似文献   

10.
Coagulation and flocculation are basic chemical engineering operations employed to remove suspended solids from water. The growing concern for environmental and ecological issues warrants the use of the biodegradable flocculants in wastewater and industrial effluent treatment. In this work, unconventional coagulant, namely lactic acid, calcium lactate, sodium lactate, and citric acid were studied in comparison with AlCl3, a usual coagulant widely employed to remove water turbidity. It was observed that lactic acid and calcium lactate were able to reduce the water turbidity similarly to AlCl3. This fact can be very interesting because lactic acid salts can be produced by biotechnological process, and contrarily to aluminium salts, they are biodegradable, reducing the risk for human and animal’s health.  相似文献   

11.
A series of 24 factorial design experiments were performed to study the effects of source water type, contaminant concentration, prefiltration and use of a coagulant on the performance of ultrafiltration process (UF) for treatment of waters contaminated with petroleumhydrocarbons (PHCs). The process performance was evaluated in terms of initial flux through the membrane, fouling time and PHC removal efficiency. The higher levels of PHC contamination significantly decreased the initial flux, membrane life and PHC removal efficiency. Coagulation pretreatment significantly improved the membrane life and PHC removal efficiency with no significant effect on theinitial flux. Prefiltration to remove the flocs from the coagulated water samples did not improve the fouling time but improved the PHC removal efficiency.  相似文献   

12.
A method was developed to fractionate chloride ions from complex effluents using an ion exchange column. The procedure utilizes a strongly basic anion exchange resin with hydroxide ions as the exchange ion. The chloride within the effluent is exchanged for hydroxide which is less toxic to Ceriodaphnia dubia. The addition of hydroxide to the solution requires a pH adjustment to a physiologically acceptable pH for Ceriodaphnia with an acid. The fractions are added to Ceriodaphnia and the ET 50 (median lethal time) determined. The column was applied to two effluents with suspected chloride toxicity. The column successfully removed virtually all of the chloride from the effluents. A significant reduction in toxicity was found following the process for one of the effluents. In addition, a control that consisted of the original effluent at the ionic strength of the column fractions revealed that chloride was a causative toxicant in both of the effluents.  相似文献   

13.
The aim of this work was to evaluate the role of three biopolymers used as coagulant?Cflocculant aids in the treatment of a high-load cosmetic industry wastewater (WW) located in Mexico. Discussion is based on a surface response methodology. When using guar, locust bean gum, and Opuntia mucilage, conductivity and turbidity removals as high as 20.1 and 67.8?% were found, respectively. Chemical oxygen demand (COD) removals as high as 38.6?% were observed. The maximum removal efficiency was found for mucilage, with 21.1?mg?COD/mg polymer. At the end of the process, pH was in the range of 5.8?C7.3 for an initial wastewater pH value of 5.6. The production of sludge was very dependent on the WW organic load. An analysis of some metal content in the sludges is presented. From the response surface analysis, it was observed that the parameter which strongly affected the removal of COD, turbidity, oil and greases (O&G), and the amount of sludge including their metal contents was the polymer dose. Only in the case of O&G removal was a combination of dose?Cwastewater organic load responsible for the removals. The values of R 2 for the correlation process were between 0.5451 (O&G) and 0.7989 (COD). The p values for the different expressions were between 0.1985 (COD) and 0.7195 (O&G). The values of adequate precisior (AP) indicate how feasible it is to use the surface response analysis (AP?>?4). Most of the analysis indicated that AP?>?4, except in the case of the O&G removal analysis where AP?=?2.9.  相似文献   

14.
Biological and chemical oxidation characteristics of two kinds ofcoke-oven wastewaters, A and B, discharged from a conventional batch coke-oven and a newly developed continuous coke-oven, respectively, were studied for selecting effective treatment processes of the wastewaters. Pollutants contained in Wastewater-A could be removed by biological process with a sufficient effluent quality, while those which existed in Wastewater-Bcould not be satisfactorily removed. Microbial community structure investigation using the respiratory quinone profile clarified that Pseudomonas putida (dominant quinone: ubiquinone-9) was a dominant species in the biological treatmentsystem. The refractory organic pollutants, existed in Wastewater-B,were mineralized more effectively by Fenton's reagent than by ozone. A wastewater treatment process, in which Fenton's oxidation is followed by a biological treatment, was proposed forthe treatment of Wastewater-B based on the experimental results.  相似文献   

15.
This study aimed to optimize two process variables, namely extractant concentration, i.e., di-2-ethylhexylphosphoric acid concentration ([D2EHPA]) and equilibrium pH (pHeq), in Cu(II) extraction from aqueous solutions with a soybean-oil-based organic solvent using response surface methodology by maximizing the percentage extraction (%E). A central composite design was applied, and a regression model for %E was developed. Adequacy of the model was examined, and it was found to be statistically significant. The optimum conditions were determined as follows: [D2EHPA] of 84.71?mM and pHeq of 4.46, which resulted in 99.78% of %E. The experimental value of %E (98.17%) obtained is found to agree satisfactorily with that (99.78%) predicted from the model.  相似文献   

16.
Moringa oleifera (MO) is a multipurpose, medium- or small-sized tree, from regions of north-west India and indigenous to many parts of Asia, Africa, and South America. Its pods have been employed as an inexpensive and effective sorbent for the removal of organics, and coagulant for water treatment. It is a non-toxic natural organic polymer. The main objective of this work was to use the MO seeds as a natural adsorbent for the treatment of dairy industry wastewater (DIW). The effects of agitation time, pH, MO biomass dose, and DIW concentration were evaluated. Removal efficiencies of up to 98%, for both color and turbidity, were reached using 0.2 g MO and 0.2 L of 1.0 g/L sorbate solution (DIW). The obtained results showed that MO seed keeps its adsorption power under a pH range between 5 and 8. The adsorption data was fitted to Langmuir isotherm. There was a significant uptake capacity of MO biomass, q max, which suggested a good affinity between DIW components and sorbent. We conclude that the MO biomass has the potential to be used in the dairy industry wastewater treatment in an efficient way and with low cost.  相似文献   

17.
The coagulant retained in cheese curd is a major contributor to proteolysis during ripening. The objective of this study was to quantify the effects of several milk-related factors and parameters during cheese manufacture on the retention of coagulant in cheese curd. The amount of coagulant retained in curd was determined by its activity on a synthetic heptapeptide (Pro-Thr-Glu-Phe-[NO2-Phe]-Arg-Leu) using reversed-phase HPLC. The retention of chymosin in cheese curd increased significantly when the pH of milk was reduced at rennet addition below pH 6.1, the pH at whey drainage below pH 5.7, or the average casein micelle size in milk and when the ionic strength of milk was increased. The casein content of milk and the quantity of chymosin added to milk had no significant effect on the retention of chymosin in curd; the quantity of coagulant bound per gram of casein remained unchanged.  相似文献   

18.
Purpose

There is increasing public concern about the amount of fresh water used on New Zealand dairy farms and the adverse impacts that farm dairy effluent (FDE) has on the environment. FDE mainly consists of fresh water (99%) with a small amount of solid material (1%). There is an opportunity to treat FDE to remove the colloidal solid material and recycle the water to wash the farm yard.

Materials and methods

A new method of treating FDE has been developed. The method uses a coagulant to flocculate and settle the colloidal particles in the FDE and thus produce the clarified water for recycling. The research and development programme involved three stages: (i) standard laboratory jar tests to establish the amount of coagulant required to treat the FDE, (ii) large tank tests to confirm the effectiveness of the coagulant at a larger scale and (iii) construction and testing of two pilot plants. A pasture field trial was conducted to test the effect of the clarified water and treated effluent on plant production.

Results and discussion

The new method of treating FDE was highly successful in removing the colloidal material and producing clarified water that can be recycled to wash the farm yard. The average turbidity of the clarified water from the first pilot plant was 52 nephelometric turbidity units (NTU) (a 97% reduction in NTU compared to the original FDE) and the average Escherichia coli concentration was 9 cfu per 100 mL (a 99.99% reduction compared to the original untreated FDE). The average total-phosphorus (P) concentration of the clarified water was 1.8 g m?3 (94% reduction), dissolved reactive phosphorus (DRP) was <?0.1 g m?3 (99% reduction) and total nitrogen (N) was reduced by >?70% (from 200 to 61 g m?3). The average turbidity of the clarified water from the second pilot plant was <?20 NTU (a 99.5% reduction). There was no adverse impact from the land application of the clarified water or the treated FDE on plant growth.

Conclusions

A new method for treating farm dairy effluent was successfully developed that produced clarified water that could be recycled to wash the farm yard and had a lower potential risk of environmental impacts when applied to land than untreated FDE. Land application of the clarified water or the treated FDE had no adverse impact on plant growth.

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19.
The amount of coagulant added to soy milk is a critical factor for tofu-making; particularly it affects the textural properties of tofu. Earlier research indicated that the critical point of coagulant concentration (CPCC) is a characteristic parameter of soy milk and could be used as an effective indicator of optimal coagulant concentration (OCC) for making filled tofu. The objective of this study was to investigate the possible correlations between CPCC and the characteristics of soy milk made from various soybean samples and the effect of soy milk cooking and dilution conditions on CPCC. CPCC was determined by a titration method. Calcium chloride and magnesium chloride were used as coagulants. Soy milk characteristics including solid, protein, phytate, pH, titratable acidity, mineral content, and 11S/7S protein and these characteristics as affected by heating rate, heating time, and sequence of dilution and heating were studied. The results showed that the CPCC was significantly (p < 0.05) positively correlated with phytate content (grams per gram of protein), pH, and 7S protein content but negatively correlated with protein content, 11S protein content, 11S/7S ratio, titratable acidity, and original calcium content. Within the same soybean material, more proteins required more coagulant, but higher protein concentration during cooking resulted in less coagulant required by each gram of protein during coagulation. The CPCC decreased with increasing soy milk heating time or decreasing heating rate. The sequence of heating and diluting for preparing soy milk also had an effect on CPCC.  相似文献   

20.
The transformation of MeHg under anaerobic conditions in axenic cultures ofDesulfovibrio desulfuricans strain LS is compared to that in anoxic marine sediments contaminated by Hg of industrial origin. MeHg was added to cultures ofD. desulfuricans strain LS and incubated at 28°C for two weeks. Significant amounts of dimethylmercury and metacinnabar were produced. These two Hg compounds were formed from the slow decomposition of the intermediate dimethylmercury-sulfide. Other collateral compounds, such as methane and ionic Hg, were also detected during the MeHg degradation process. On the other hand a sample of fresh sediment (1.5 g d.w.) was spiked with 10 μg of MeHg and 2 mmoles.ml?1 of pyruvate, as carbon source for sulfate-reducing bacteria. After 9 days of incubation at 28°C, significant amounts of dimethylmercury were produced. A lower content of this volatile species was found in a subsample of sediment supplemented with sodium molybdate, which is a strong inhibitor of sulfatereducing activity. A kinetic study showed the disappearance of monomethylmercury from the sediment and the formation of dimethylmercury over the incubation period. The environmental significance of dimethylmercury and dimethylmercury-sulfide in the natural biogeochemical cycle of Hg is discussed.  相似文献   

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