Chemical Precipitant Research Articles

The use of calcined paper mill sludge as a chemical precipitant in the simultaneous removal of ammonium and phosphate - paper mill waste recycling and reuse

The use of calcined paper mill sludge as a chemical precipitant in the simultaneous removal of ammonium and phosphate - paper mill waste recycling and reuse

Use of Calcined Dolomite as Chemical Precipitant in the Simultaneous Removal of Ammonium and Phosphate from Synthetic Wastewater and from Agricultural Sludge

Phosphorus as phosphate and nitrogen as ammonium or nitrate are the main nutrients in wastewaters and agricultural sludges. They runoff easily to waterways and cause eutrophication in water bodies. However, ammonium and phosphate could be precipitated simultaneously and used as recycled nutrients. In this research, dolomite calcined at 650 °C, 750 °C, or 950 °C and commercial MgO were used as precipitants in simultaneous phosphate and ammonium removal from synthetic (NH4)2HPO4 solution and agricultural sludge. Calcination at 750 °C was the preferred option as dolomite was decomposed to MgO and CaCO3 for optimal struvite precipitation. Molar ratios of 1.1–1.6:1–2:2 (Mg:P:N) were employed in the experiments. Very robust ammonium removal was obtained with MgO (57%), dolomite 650 °C and dolomite 750 °C (75%). MgO removed almost all phosphate, while dolomite 650 °C removed 65%, and dolomite 750 °C removed 60% (70% from agricultural sludge). Some part of the phosphate was adsorbed, most likely by CaCO3, during dolomite precipitation. Struvite was the only identified reaction product in all samples after 24 h of precipitation. Calcined dolomite had great potential in ammonium and phosphate precipitation from both synthetic waters and agricultural sludges and the precipitates could be used as recycled fertilizers.

The Use of Ca- and Mg-Rich Fly Ash as a Chemical Precipitant in the Simultaneous Removal of Nitrogen and Phosphorus—Recycling and Reuse

The European Union’s circular economy strategy aims to increase the recycling and re-use of products and waste materials. According to the strategy, the use of industry waste material should be more effective. A chemical precipitation method to simultaneously remove phosphorus and nitrogen from synthetic (NH4)2HPO4 solution and the liquid phase of anaerobic digestate using fly ash as a precipitant was tested. Fly ash is a waste material formed in the power plant process. It mainly contains calcium oxide (CaO) and magnesium oxide (MgO). Saturated precipitant solution was prepared from fly ash, which was added in small proportions to (NH4)2HPO4 solution during the experiment. Fly ash’s effectiveness as a precipitant was compared with that of commercial CaO and MgO salts, and it can be observed that fly ash removed as much ammonium and phosphate as commercial salts. Fly ash sufficiently removed ammonium nitrogen and phosphate from the liquid phase of anaerobic digestate, which led to the formation of ammonium magnesium hydrogen phosphate hydrate, struvite (NH4MgPO4·6H2O), and calcium hydroxide phosphate, monetite, CaPO3(OH). In this study, we have shown for the first time that fly ash can be used to manufacture recycled, slow-release fertilizers from anaerobic digestate.

HDL-PARTICLES SEPARATION EMPLOYING DIFFERENT PRECIPITATING AGENTS: FUNCTIONAL PROPERTIES OF THE IMPACT OF CHEMICAL PRECIPITATION ON LIPOPROTEIN PARTICLE-SIZE AND PARAOXONASE-1-ACTIVITY

First-generation methods used to quantify HDL-cholesterol have been used for decades. Therefore, first-generation precipitatingreagents still in use, the chemical impact on HDL-particles functionality (structure/activity-relationship) is not well-documented. The study aim was to identify the most efficient precipitating-reagent for lipoprotein separation to be used in the HDL functionalevaluation. A cross-sectional design with convenience sampling was conducted. Plasma samples from 40 individuals, both genders, were evaluated. Biochemical analysis was performed after using different chemical precipitants (e.g. polyethylene glycol - PEG (P1), phosphotungstic-acid (P2), and dextran-sulfate/MgCl2 (P3)) to evaluate HDL-particle-size and PON1-activity. Parametric and non-parametric tests were performed using GraphPad-Prism 5.01 (USA). Differences were considered significant when a p-value < 0.05 were obtained. The PON1-activity comparison differed after NaCl stimulation (p < 0.001, paired t-test) and among chemical precipitant treatments. The PON1-activity differed after sample precipitation with P1 when compared to P2, and P3 (p < 0.05; ANOVA), before and after stratification for dyslipidemia group. The HDL particle-size comparison did not differ, but on the other hand, polydispersity differed after sample precipitation with P3 when compared to P1 or P2 (p < 0.05; ANOVA). Dextran- Sulfate/MgCl2 was a better chemical precipitant for PON1-activity, and PEG for HDL-particle-size, respectively. The HDL functional

A comparative study of different natural palygorskite clays for fabricating cost-efficient and eco-friendly iron red composite pigments

A series of α-Fe2O3/palygorskite (α-Fe2O3/Pal) inorganic-inorganic composite pigments were prepared by a one-step hydrothermal process using six kinds of iron-rich natural palygorskite clays (Pal-c) with different structures, morphologies and compositions as starting materials. The effects of different natural Pal-c on the structure, chemical composition, color and stability of the as-prepared composite pigments were studied comparatively by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmittance electron microscope (TEM), X-ray fluorescence spectroscopy (XRF) and CIE-L*a*b* colorimetric analyses. The results showed that the Fe(III) ions in the reaction solution can be converted into red α-Fe2O3 particles in situ on the Pal surface, without adding any chemical precipitant. Pal not only induce formation of α-Fe2O3 as a ‘green’ precipitant, but also effectively control the particle size of α-Fe2O3 nanoparticles as a microreactor and prevent the aggregation of particles as a supporter. The chemical composition of natural Pal-c has a great influence on the L*, a*, b* values of the composite pigments, while the associated mineral types have little effect on the color values of the pigments. The optimal iron-red composite pigment mainly composed of 58.59% Fe2O3 and 35.11% SiO2 exhibits the best L* value of 31.1 and a* value of 33.4, which is superior to commercial iron red pigment (a* = 26.9). The red composite pigment exhibits excellent chemical stability and remains in a good red color after treatment with an acid solution, an alkaline solution, or an organic solvent. In addition, the red composite pigment can be well dispersed in ethanol or water, and can be uniformly sprayed onto the ceramic substrate and stably coated on it, and remains a vivid red color after calcinations at 1100 °C.

Novel combined method of biosorption and chemical precipitation for recovery of Pb2+ from wastewater.

A novel combined biosorption-precipitation process has been designed and applied to recycle Pb2+ from low concentration lead containing wastewater. Pb2+ was firstly removed selectively from wastewater by pyromellitic dianhydride (PMDA) modified sugarcane bagasse (SB) fixed-bed column, and then, it was desorbed into the concentrated eluate and recycled by adding chemical precipitant. Adsorption performance of the column and optimum desorption and precipitation condition for Pb2+ were investigated in detail. Results showed that the as-prepared column could efficiently remove Pb2+ from aqueous solution and optimum condition for Pb2+ precipitation in eluate was at pH3.0 and molar ratio of precipitant to Pb2+ of 5:1 by using Na3PO4 as precipitant. Recovery experiment illustrated that Pb2+ was selectively removed from wastewater containing ions of Pb2+, Zn2+, Cd2+, Ca2+, K+, and Na+ through competitive substitution adsorption on the modified SB, and mass ratio of the five metal ions in eluate was 96.8:0.7:0.7:0.7:0.5:0.5. Pb2+ in this concentrated and purified eluate solution was recycled efficiently by adding Na3PO4. The combined method had great potential in application of heavy metal recovery from wastewater.

Synthesis of Cobalt hexacyanoferrate decorated graphene oxide/carbon nanotubes-COOH hybrid and their application for sensitive detection ofhydrazine

A three-dimensional graphene oxide/carbon nanotubes-COOH hybrid (GO/CNTs-COOH) consisted of two-dimensional graphene oxide (GO) and one-dimensional carbon nanotubes-COOH (CNTs-COOH) was synthesized. The GO/CNTs-COOH hybrid exhibited excellent water-solubility owing to the high hydrophilicity of GO components and the carboxylation of carbon nanotubes. The cobalt hexacyanoferrate decorated GO/CNTs-COOH (CoHCF/GO/CNTs-COOH) has been prepared using electrostatic adsorption of Co2+ on GO/CNTs-COOH and K4[Fe(CN)6] as an in-situ chemical precipitant. FT-IR, Raman spectroscopy, TEM, SEM, and cyclic voltammetry were utilized to characterize the nanohybrid. The electrochemistry behavior of hydrazine on different modified electrodes was also studied. The CoHCF/GO/CNTs-COOH modified GCE (CoHCF/GO/CNTs-COOH/GCE) exhibited greatly enhanced electrocatalytic performance towards electro-oxidation of hydrazine. The oxidation peak currents showed good linear relationships with concentration of hydrazine. It can be applied to detect hydrazine in samples sensitively.

Solids Role in Tertiary Chemical Phosphorus Removal by Alum

The need to control and remove phosphorus (P) in discharges from waste water treatment facilities (WWTF) to prevent eutrophication of receiving waters is well known. Regulatory initiatives are further contributing to the addition of stringent P limits to discharge permits. Accordingly, many agencies are facing increasingly stringent standards of effluent P and as a result the effluent limit of 0.1 mg P/L total phosphorus (TP) or lower is being achieved. Since the reliable performance limit of enhanced biological phosphorus removal (EBPR) is commonly accepted at about 0.1 mg P/L in the dissolved form, these facilities will need to utilize tertiary chemical phosphorus removal (CPR) to reliably achieve limits lower than 0.1 mg P/L (ultra-low limits) (Pagilla and Urgun-Demirtas, 2007). The mechanistic basis for P removal using chemical precipitant addition is generally considered to be more than simple precipitation. The role of adsorption and/or surface complexation in removal of reactive or unreactive phosphorus to the already formed chemical precipitates or complexes has been reported. Omoike and VanLoon (1999) showed that the most likely mechanism involves sorption of P species on Al(OH)3(s) formed by Al salt addition to water for P removal, and further precipitation/complexation of P onto the Al hydroxyl precipitate for additional P removal. In tertiary P removal, usually a non-stoichiometric dose or several times stoichiometric dose of the precipitant is needed. The chemical precipitates formed upon addition of such high doses of chemical precipitant are likely to serve as nuclei for further aggregation of newly formed precipitates, thus enhancing the overall tertiary P removal. The excess precipitant added to the secondary effluent produces hydroxyl precipitates which could serve as adsorbents for additional P removal. It is well proven that alum sludge from water treatment plants have high capacity for wastewater effluent P removal depending on their structure and/or age of the sludge solids. The role of mixing, pH, contact time, precipitated solids concentration in the mixing tank, and feed secondary effluent characteristics could influence this process of tertiary P removal. The investigation of such variables and the process along with careful analytical measurements would explain the basis for precipitation/solids contact P removal from wastewater effluents. Such information could be used to enhance the process and optimize the operating conditions of tertiary P removal by chemical addition. This paper presents full scale and lab scale investigations of some of the above listed parameters on tertiary P removal with specific focus on role of precipitated solids in enhancing P removal and/or reducing the dose of precipitant to be added to achieve the desired P removal. The study was conducted at the Iowa Hill Water Reclamation Facility (WRF) and Farmers Korner WWTF in Breckenridge, CO, and at the Illinois Institute of Technology. This title belongs to WERF Research Report Series . ISBN: 9781780406763 (eBook)

Biological Phosphorus Removal Combined with Ferrous Chemical Phosphorus Removal

Chemical phosphorus removal is widely applied to enhance the biological phosphorus removal in order to meet the discharge requirement. Performance change caused by ferrous sulfate was investigated in this study. Compared to the control system which was not chemically dosed, pH and SVI slightly decreased while conductivity increased. The correlation between phosphorus and conductivity was weakened. The release and uptake of potassium declined, illustrating a negative impact of chemical precipitant on phosphorus accumulating organisms (PAO). The phosphorus uptake decreased while phosphorus release fluctuated. The phosphorus was not suitable for revealing the metabolic activity of PAO due to formation of ferric phosphate and ferric hydroxide.

Effect of cement kiln dust addition on activated sludge process without primary settling for reuse applications

Today, numerous treatment plants are designed and operated using chemicals for nutrient removal, sludge conditioning and promotion of better sedimentation or flotation. Cement kiln dust (CKD) is useless byproduct from the cement industry and a significant resource value for lime substituting. In this paper work, CKD is used as a chemical precipitant for activated sludge process pilot plant without using primary settling at different temperature ranges (30–35) °C and (15–20) °C. For temp. ranges (30–35) °C, CKD addition concentration was 1 g/l and the system achieved very good removal of 93.5%, 93.3%, 93.6% and 87% for BOD5 COD, TSS, and Ptotal, respectively. The system also achieved high removal efficiency for pathogenic indicators with 5 log removal units for Total Coli forms (Tc), Fecal coliforms (Fc), Escherichia coli (E. coli), respectively. For temperature ranges (15–20) °C, different CKD addition concentration were used until reached 2 g/l which enabled the system to achieve high removal efficiencies of 94.1%, 94.1%, 94.2% and 87.9% for BOD5 COD, TSS, and Ptotal, respectively. The system achieved 6 log removal units for Tc, Fc, and E. coli respectively. As a result of CKD additions of 1.2 g/l for temperature ranges (30–35) °C and (15–20) °C, respectively to the used activated sludge process pilot plant without using primary settling, the system achieved high removal efficiencies of the chemical and bacteriological pollutants which enabled the system to achieve the permissible effluents of these pollutants to comply with the requirements of reuse limits of wastewater for agricultural purposes, Law 501/2005 limits.

The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal: Part 7: Application of the IAWQ model

The IAWQ Activated Sludge Model (ASM) No. 2 is a kinetic-based model and incorporates two simple processes for chemical precipitation and redissolution that are readily integrated with biological processes for carbon, nitrogen and phosphorus remov al. This model was applied to experimental data collected as part of this study from parallel pilot-scale 3-stage Phoredox systems with and without simultaneous dosing of chemical precipitant. The precipitants tested were alum, ferric chloride and ferrous-ferric chloride. The model was calibrated to the control unit (without precipitant addition) in order to match effluent phosphate (P) predictions (and hence P removal) as closely as possible. The same calibration was then applied to modelling the test unit (wit h precipitant addition). It was found that the default model input stoichiometry for the precipitation reaction (ideal 1:1 molar ratio of metal ion (Me) to P) was suitable for ferric chloride addition at a 20 d sludge age, but did not accurately reflect the test sy stem behaviour for all experimental periods. A lower stoichiometry (0.60 to 0.75) was required for alum at a 20 d sludge age, and fo r a blend of predominantly ferrous chloride at a 10 d sludge age. The input stoichiometry was further decreased under P-limiting conditions. A simple approach to, and possible reasons for, the manipulation of the model stoichiometry are discussed in the li ght of observed stoichiometry from system P removal and fractionation data collected as part of this study. Furthermore, an alterna tive approach based on manipulation of the precipitation (and hence redissolution) kinetic constant is suggested and evaluated using available experimental data. Model predictions and observed data in respect of polyphosphate (polyP) and suspended solids are a lso compared and discussed. It is concluded that the ASM No. 2 model provides a useful basis for modelling simultaneous P precipitation, provided certain minor modifications are made. Further investigation into the kinetics of the precipitation process(es) is recommended, particularly in relation to the effect of system sludge age. The model lends itself to further enha ncement by incorporating additional physico-chemical processes.

The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal: Part 5: Experimental periods using a ferrous-ferric chloride blend

A blend of ferrous chloride and ferric chloride (FeCl2-FeCl3) was simultaneously dosed into an activated sludge system at pilot scale in order to test the effect on biological P removal. Additional removal due to chemical precipitation was measured as the difference in system P removal between parallel test and control systems. Both systems strongly exhibited biological excess P removal (BEPR). The extent of P release in the anaerobic reactors of the two systems was compared by mass balance, as one indicator of the relative "magnitude" of BEPR. Phosphorus fractionation of the mixed liquor also served as an indicator of the biological and chemical mechanisms. Evidence was found that the BEPR mechanism is partially inhibited by simultaneous FeCl2-FeCl3 addition, even in the absence of effluent phosphate limitation. However, the degree of inhibition was relatively low, ranging from 3 to 25% (approximately) for Fe doses in the range ca. 10 to 20 mg/&#8467; as Fe, with an average system P removal of 14 to 18 mgP/&#8467; in the control. FeCl2-FeCl3 dosing in this range was sufficient to produce additional P removal of the order of 1 to 8 mgP/&#8467; over periods of one to seven sludge ages per experimental period, depending on the experimental conditions. Sustained operation of the BEPR mechanism in the presence of FeCl2-FeCl3 was possible over a continuous period of seven sludge ages, under conditions in which effluent phosphate was at least partially limiting. Under such conditions, the chemical and biological mechanisms appear to be "disadvantaged" to approximately the same extent, as evidenced by the apparent stoichiometry of Fe: P for the chemical precipitation and magnitude of the poly P containing fractions measured for the biological mechanism. This suggested that the biological mechanism is able to compete effectively with the chemical mechanism under conditions of low reactor phosphate concentrations (~1 mgP/&#8467; orthoP) for sustained periods. However, the presence of simultaneous chemical precipitant significantly reduces the extent to which the biological P removal potential is utilised under P-limiting conditions. This could explain the difficulty sometimes reported in the control of full-scale activated sludge systems with simultaneous precipitant addition where a very low effluent P concentration WaterSA Vol.27(2) 2001: 117-134

Development of a jar testing protocol for chemical phosphorus removal in activated sludge using statistical experimental design

Jar testing is an important tool for the determination of the best chemical dosing regime for a wastewater treatment process. A consistent methodology has been developed for physico-chemico processes such as sedimentation and coagulation. These techniques however, may not be applicable for precipitation processes in a biological system. A jar testing methodology was developed for the chemical removal of phosphorus from activated sludge mixed liquor. In these studies, the optimum conditions for 5 precipitants in activated sludge were determined to compare their relative effectiveness. The precipitants studied were aluminium sulphate, ferrous sulphate, ferric chloride and two aluminium-based polyelectrolyte compounds. Optimisation of this process by a conventional method requires many tests and is time consuming. A 7 factorial design experiment was used firstly to identify the most important variables, followed by a statistical “hill climbing technique” to determine the optimum conditions for a specific chemical precipitant. Using only 20 tests per chemical (not including repeats), good phosphorus removal efficiencies (ranging from 87.8–96.6%) were produced for all of the precipitants.

Demonstration of Calcium Ion Distribution in Calcifying Cells. X-ray Microanalysis and Electron Spectroscopic Imaging after Fixation with NHA-Containing Fixative and Microwave Irradiation.

We have seen reporting on the calcium ion distribution in cells and tissues with X-ray microanalysis (EDX) since 1978 [9] and with electron energy-loss spectroscopy (ESS) imaging since 1983 [10, 17], under various fixing conditions [12-16, 18-24]. Almost ten years ago, we tried a fixative containing NHA (N, N-naphthaloylhydroxamine) as a chemical precipitant for Ca2+ ions under microwaved conditions [12, 19]. However, the data did not seem to be as sensitive or useful, under conventional electron microscopy and computerized X-ray microanalysis, compared to the two-step replacement method combined with microwave fixation using potassium (K) oxalate followed by potassium (K) antimonate, for the detection of Ca2+ ions [12, 19-21]. Recently, however, we used ESS to analyze same tissue sections which were fixed with NHAcontaining fixative with microwave fixation ten years previously. We discovered with ESS analysis that NHA is a sensitive and ideal chemical reagent for calcium ion detection in a cell giving the same view as that of frozen dried or freeze-substituted tissue sections. Calcium was clearly seen and widely distributed in developing chondroblast endoplasmic ultrastructures: ribosomes, cell and endoplasmic membranes, mitochondria, Golgi, and nucleus. However, free mesenchymal cells which were not involved in calcifying functions had only a very small amount of calcium. Calcium was widely distributed in the lacunae of the surrounding space of the chondroblasts and inmature matrix, but the exoplasm of the chondroblasts was almost calcium-free. Other elemental images in the young chondrocytes or osteoblasts, i. e., P.L, S.L, O.K, and N.K, were seen clearly superimposed on the cell ultrastructures, i. e., the cell membranes, ribosomes, endoplasmic reticula, mitochondria, Golgi, and nucleus [24].

5328599 System using sulfide ion-selective electrodes for control of chemical feed of organic sulfide products for metal ion precipitation from waste water

A wastewater treatment system and method for chemical precipitation and removal of metals from wastewater in a continuous or batch treatment process includes an ion-selective sulfide electrode and a reference electrode disposed in a precipitation tank for measuring an electrochemical potential therebetween in a predetermined range. A controller unit is provided which is responsive to the electrochemical potential in the predetermined range and is connected to a precipitant feed unit for automatically controlling the chemical precipitant fed into the precipitation tank.

Phosphorus Fractionation of Activated Sludges from Modified Bardenpho Processes with and without Chemical Precipitant Supplementation

The natural occurrence of chemically precipitated phosphate in activated sludge (AS) has been hypothesized for over two decades and deserves fresh attention in view of the increasingly common practice of chemical addition to modified AS systems to achieve P removal. In this study, orthophosphate extracted from AS of modified Bardenpho plants could not be accounted for on the basis of polyphosphate interferences. In a plant not dosed with chemicals at least 14 mg P/g VSS were therefore formed by natural precipitation reactions while an identical plant dosed with ferric sulphate showed at least 37 mg P/g VSS to be of this fraction. A plant dosed with alum and receiving wastewater of mainly industrial origin contained up to 8 mg P/g VSS as chemical precipitate which was over half the total P content of that sludge. Restraint in dosing chemicals is suggested to prevent unnecessary suppression of the biological mechanism of P removal. Ferrous sulphate dosing may be superior to that with ferric sulphate Since the latter apparently causes poly P hydrolysis. Complex interactions between iron, ortho P and biomass are indicated. Furthermore, iron-ortho P complexes in mixed liquor supernatant may be unreactive in the colorimetric ortho P assay.

Zirconium-induced precipitation of phosphate as a means of controlling eutrophication

A potentially promising method of controlling eutrophication by means of zirconium oxychloride, a chemical precipitant for phosphate, is described. Zirconium oxychloride precipitates phosphate and limits algal growth at fairly low concentrations (100 ppm) at a pH range of 2–11. At this concentration, ZrOCl 2 does not seem to be harmful either to the tested fish or algae.