Calcium Carbonate Flocculation Research Articles

Use of an acrylamide-based anionic polymer for the concentration and removal of Giardia duodenalis cysts from high-turbidity water samples

The increasing investigation into environmental contamination by Giardia spp. cysts and its impact on public health has spurred interest in developing more sensitive methods for detecting these protozoa, particularly in water. However, these methods remain complex and costly. This study evaluated the concentration and removal efficiency of Giardia duodenalis cysts using an acrylamide-based anionic flocculant polymer (AFP) in filter backwash water samples from a water treatment plant (WTP) located in Blumenau City, southern Brazil, and compared them with the calcium carbonate flocculation technique (CCF), which is routinely used for water matrices with high turbidity. The average recovery rates of G. duodenalis cysts using CCF and AFP were 33.33% and 43.33%, respectively, with an average turbidity reduction of 98.39% and 98.78%. The use of an anionic flocculant polymer proved to be an efficient alternative for the concentration and removal of protozoan cysts in water samples with high turbidity. It is important to highlight that the development and application of new studies and strategies aimed at increasing the efficiency of the removal of these organisms from complex environmental matrices would bring benefits to public health and promote a One Health perspective. Keywords: cyst recovery, high turbidity, water.

Concentration and risk assessment of Cryptosporidium infection associated with exposure to the Njoro River, Njoro Sub-County, Nakuru, Kenya

BackgroundCryptosporidium is a gastrointestinal pathogen. The oocysts are transmitted through the environment, and drinking contaminated water is one particular route. There is heavy pollution of Cryptosporidium in Njoro River, the main source of drinking water for humans and animals around the watershed. However, there is no information on the parasite concentration and estimated health risk exposed to these populations. This study determined the level of contamination and risk of infection by Cryptosporidium parasites in Njoro River. Water samples were collected monthly from three ecological sites along Njoro River for twelve months. Cryptosporidium oocysts were concentrated from these water samples using calcium carbonate flocculation method, examined and counted using epifluorescent microscopy. Quantitative microbial risk assessment was applied to estimate the health risk of Cryptosporidium infection in Njoro River using a beta-Poisson dose–response model.ResultsThe concentration of Cryptosporidium parasites in Njoro River is 0.936 ± 0.73 oocysts/litre. However, this concentration fluctuates with ecological site of the river; highest concentration occurs at downstream (1.325 ± 0.73), followed by midstream (0.917 ± 0.74) and least at upstream (0.567 ± 0.54). Concentration of Cryptosporidium in the river is higher during wet than dry seasons, with the difference in mean concentrations between the two seasons being significant (t(34) = − 6.101, p < 0.01). There was a negative correlation between Cryptosporidium concentration, temperature and pH, while a strong positive correlation existed between Cryptosporidium concentration and turbidity. The daily probability of infection by Cryptosporidium in Njoro River watershed is 0.25, while the annual risk is 0.99.ConclusionsNjoro River is heavily polluted with Cryptosporidium parasites. This exposes both the humans and animals that drink water from this river to a high risk of cryptosporidiosis, a potentially fatal infection particularly in immunocompromised individuals.

Reinforcement of Different Sands by Low-pH Bio-Mineralization.

Different sands have significant influences on MICP reinforcement effects. Using calcium carbonate production and bioflocculation lag period as evaluation criteria, this study investigates the optimal theoretical pH values of bacterial solutions with different concentrations. We reinforced four different sands using MICP at the optimal theoretical pH, and based on permeability, moisture retention, raindrop erosion, wind erosion, penetration, and SEM tests, the influence of sand properties on low-pH MICP reinforcement was analyzed and the low-pH MICP mechanism was revealed. The results indicate the following: (1) The optimal theoretical pH values for bacterial solutions with concentrations of 0.67 × 108 cells/mL, 3 × 108 cells/mL, and 10 × 108 cells/mL are 4.5, 3, and 4, respectively. (2) With 0.67 × 108, 3 × 108, and 10 × 108 cells/mL bacterial solutions, the strength of tailings sand containing calcium salt was 21.15%, 44.42%, and 13.61% higher than that of quartz sand, respectively. The effective reinforcement depth of alkaline reclaimed sand was 10, 8, and 6 mm lower than that of neutral calcareous sand, respectively. The strength of fine tailings sand was 70.41%, 58.04%, and 22.6% higher than that of coarse reclaimed sand. The effective reinforcement depth of fine quartz sand was 6, 4, and 4 mm lower than that of coarse calcareous sand. (3) Low pH temporarily suppresses urease activity, delaying calcium carbonate flocculation and enhancing reinforcement uniformity. To achieve optimal reinforcement effects, adjusting the actual optimal pH values of bacterial solution based on sand properties is essential in engineering applications.

Flocculation of alkyl ketene dimer and calcium carbonate on paper sizing and filling performance

Abstract In order to solve the conflict between precipitated calcium carbonate (PCC) filling and alkyl ketene dimer (AKD) sizing for paper, this study explored two new flocculation methods: AKD and PCC were flocculated separately in the process ((A)(P)F), while the two pre-flocs from AKD and PCC were blended in the process ((AP)F). The result showed that increasing the dosage of the flocculant cationic starch (CS) resulted in a significant growth in the median size of PCC flocs and reduction in the specific surface area, turbidity, the negative charge of Zeta potential, as well as the adsorption capacity of PCC to AKD. Consequently the sizing degree and filler retention rate of the handsheets rose markedly. With 125 mg g−1 of CS, compared with the conventional process, the filler retention rate for (A)(P)F grew up to 86.16%; the Cobb60 values for both (AP)F and (A)(P)F declined, and the contact angle (CA) increased to 120.65° and 127.65° respectively. At the same time, the filler bondability factor (FBF) were increased due to the intensified bonding force between fibers, and resultantly the comparable mechanical properties of papersheets with a high level of filler retention was obtained from (AP)F and (A)(P)F flocculation processes.

Preparation and performance of retention and drainage aid made of cationic spherical polyelectrolyte brushes

Abstract Spherical polymer brushes were synthesized by grafting acrylamide from the surface of γ-methacryloxypropyl trimethoxy-silane-modified SiO2 nanoparticles. Then, cationic spherical polyacrylamide (CSPAM) brushes were obtained by a manniched polyacrylamide (PAM). Fourier-transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, and gel permeation chromatography were introduced to analyze the structure, morphology, and molecular weight of CSPAM, respectively. The effects of pH and the dosage of CSPAM on the flocculation of fine pulp and precipitated calcium carbonate were studied. Furthermore, the optimal drainage performance could be achieved when the beating degree (°SR) decreased by about 14.42% with the dosage of CSPAM of 2 mg·g−1. The retention effect of CSPAM revealed that the highest first-pass retention was 71.1% when the dosage of CSPAM was 3.5 mg·g−1. In addition, the mechanism of retention and drainage of CSPAM was discussed.

Direct centrifugation for detecting Giardia spp. cysts in filter backwash water

Abstract Pathogenic protozoa endanger human health and challenge water treatment, especially during outbreaks in developing countries. For instance, Giardia spp. cysts can recirculate in the filter backwash water (FBW), reinforcing the relevance of their detection protocol in negligible matrices. This study aimed to detect Giardia spp. cysts in the FBW by direct centrifugation (DC) and immunomagnetic separation (IMS) with the addition of the detergent dispersion solution ICN 7X at 1.0%. To do this, cyst suspensions were inoculated into FBW samples (14 NTU), which was generated in bench-scale drinking-water treatment with high-turbidity study water (112 NTU). Furthermore, the DC+ICN 7X method was compared with the calcium carbonate flocculation. For instance, the DC+ICN 7X method provided cleaner microscope slides and minor damage to the cyst walls. The commercial suspension of Giardia lamblia had an adequate recovery rate (19.5%). However, the recovery rate of the EasySeed® suspension was 7.8%, which was below the required range by Method 1623.1 (above 8%). High costs and low efficiencies challenge several methods for detecting Giardia spp. cysts. Therefore, future studies should develop and improve detection protocols, especially for complex matrices. Detecting cysts in water treatment residues is crucial for addressing current sanitation issues in developing countries.

Detection of Cryptosporidium Parvum Oocysts in Artificially Contaminated Filter Backwash Water and Ozone Treatment at Pilot Scale

ABSTRACT Waterborne diseases are a relevant concern for public health systems since commonly applied treatment techniques may not remove all water contaminants. Cryptosporidium spp. oocysts are an issue in water treatment plants due to their reduced size and resistance to the disinfection process (e.g., chlorination). Moreover, oocysts retained on the filter media might recirculate amongst the filter backwash water (FBW). This study aimed to detect Cryptosporidium parvum oocysts artificially inoculated on the FBW and evaluate the ozone treatment performance. A synthetic FBW underwent three concentration methods followed by immunomagnetic separation: calcium carbonate flocculation, direct centrifugation, and direct centrifugation with the 7X ICN dispersion solution. The latter method was selected as it presented less interference on oocyst viability (37.2% reduction) and higher recovery (22.1%) on preliminary assays. The recovery for the commercial suspensions was 15.4 ± 3.3%, although the analytical quality performed with EasySeed® suspension obtained a recovery of 2.8 ± 0.8%. These limitations and methodologies for protozoan detection are challenging due to low recoveries, especially in complex matrices. Finally, FBW ozonation was performed on a pilot scale, and the propidium iodide dye indicated oocyst viability decreased after treatment. Oocyst inactivation was 2.83 log and 3.44 log for dosages of 7.5 mg O3 L−1 for 10 min (i.e., 75 mg min L−1) and 10 mg O3 L−1 for 5 min (i.e., 50 mg min L−1), respectively. Disinfection is a crucial pathway for addressing outbreak scenarios, and ozone treatment should be further studied.

Detection of Giardia and Cryptosporidium in environmental matrices with immunomagnetic separation: two or three acid dissociations.

This study evaluated the technology of detection of Giardia spp. cysts and Cryptosporidium spp. oocysts in environmental matrices obtained after water treatment on a bench scale. Calcium carbonate flocculation with immunomagnetic separation was the selected method to quantify the protozoa, and the importance of the number of acid dissociations in the immunomagnetic separation was assessed. When adding the third acid dissociation, an increase of 71% ± 6 in floated residue and 31.9% ± 28.7 in filter backwash water in cyst recovery was observed, while in oocyst recovery, a non-significant increase was detected. In the filtered water, this increased dissociation was important in the protozoa recovery with increases greater than 33%. The results showed that there is a strong interaction of these target organisms with the magnetic microspheres, since protozoa were still recovered in the third acid dissociation and some of them were still adhered to the magnetic microspheres.

Enzymatic nanocellulose in papermaking – The key role as filler flocculant and strengthening agent

Nanocelluloses have been increasingly used in composites since their reduced size, high aspect ratio and stiffness confer great strength to the materials. In papermaking, it has been proved that harsh and expensive chemical pre-treatments to generate nanofibrils, such as TEMPO-mediated oxidation, are not the most favourable and therefore the use of cellulose microfibrils (CMF) have gained extra attention, especially those produced with the aid of enzymatic hydrolysis. In the present work, strategies to improve filler flocculation and the papermaking properties, by using enzymatic CMF, are provided. The CMF degree of polymerization was found to be directly related to precipitated calcium carbonate flocculation, leading to higher retentions in the fibre matrix. Besides, the paper dry and wet strengths were much improved, allowing in return the production of high-filler loaded handsheets with reduced requirements for common paper additives.

Performance comparison of three methods for detection of Giardia spp. cysts and Cryptosporidium spp. oocysts in drinking-water treatment sludge.

Detecting pathogenic protozoa in drinking-water treatment sludge is a challenge as existing methods are complex, and unfortunately, there are no specific technical standards to follow. Selecting an efficient analytical method is imperative in developing countries, such as Brazil, in order to evaluate the risk of parasite infection. In this context, three methods to detect Giardia spp. cysts and Cryptosporidium spp. oocysts were tested in sludge generated when water with protozoa and high turbidity was treated. Jar testing was carried out using polyaluminium chloride as a coagulant to generate the residue to be analyzed. The results showed that calcium carbonate flocculation with reduced centrifugation and immunomagnetic separation obtained the highest recoveries in the tested matrix showing 60.2% ± 26.2 for oocysts and 46.1% ± 5 for cysts. The other two methods, the first using the ICN 7× cleaning solution and the second considering the acidification of the sample, both followed by the immunomagnetic separation step, also presented high recoveries showing 41.2% ± 43.3 and 37.9% ± 52.9 for oocysts and 11.5% ± 85.5 and 26% ± 16.3 for cysts, respectively. Evidently, these methods and others should be studied in order to make it possible to detect protozoa in settled residue.

Molecular surveillance of Cryptosporidium and Giardia duodenalis in sludge and spent filter backwash water of a water treatment plant.

The purpose of this study was to monitor the presence of Cryptosporidium spp. and Giardia duodenalis in a water treatment plant (WTP) using settling sludge and backwash water (BW) samples in previous and post the deflocculation of polyaluminium chloride (PAC) flacks. Eleven collections were performed. BW and settling sludge (SSF) were concentrated by calcium carbonate flocculation, and another aliquot of settling sludge (SSC) by centrifugation. The samples were divided as follows: Group A, containing 33 samples without degradation of PAC flakes, and Group B, with degradation by alkalinization with 10 M NaOH. Sample DNA was extracted with a commercial kit, and nested polymerase chain reaction (PCR) was used to detect Cryptosporidium and G. duodenalis. All samples from Group A were negative for Cryptosporidium spp., and 6.1% (2/33) were positive for G. duodenalis in SSC samples. While the absence of Cryptosporidium may be due to a low contamination level of the water resource, the presence of G. duodenalis indicates contamination of the raw water. The detection of G. duodenalis in SSC samples indicates that this detection method was the most effective. The 33 samples from Group B were negative for both protozoa, probably due to the presence of aluminium and humic substances.

Hydrolysis of cationic polyacrylamide and its effect on flocculation of ground calcium carbonate

Cationic polyacrylamides (C-PAMs) have been widely used as flocculating agents to aggregate particles carrying negatively charged surfaces. This study examined the effects of hydrolysis of C-PAM on its adsorption behaviour and flocculation of negatively charged particles, specifically ground calcium carbonate (GCC). C-PAM hydrolysis was examined using polyelectrolyte titration and ion chromatography, while the adsorption behaviour of the polymer was monitored using a quartz crystal microbalance with dissipation (QCM-D). Laser diffraction spectroscopy was used to measure the size of the GCC aggregates under neutral and alkaline conditions. The charge density measurements and ion chromatograms indicated that the hydrolysis of C-PAM was accelerated with increased pH and temperature. The QCM-D measurements of hydrolysed C-PAMs, adsorbed on a substrate with a flat and rigid structure, indicated that hydrolysis of C-PAM suppressed its ability to cause inter-particle bridging flocculation, which reduced the aggregate size of GCC.

Coagulation, flocculation, dissolved air flotation and filtration in the removal of Giardia spp. and Cryptosporidium spp. from water supply

ABSTRACTRemoving protozoa from a water supply using coagulation, flocculation, dissolved air flotation (DAF) and filtration on a bench scale was evaluated. Calcium carbonate flocculation with and without immunomagnetic separation (IMS) was chosen to detect Giardia spp. cysts and Cryptosporidium spp. oocysts in the studied samples. The results indicated that DAF removed between 1.31 log and 1.79 log of cysts and between 1.08 log and 1.42 log of oocysts. The performance was lower in filtration, with the removal of 1.07 log–1.44 log for cysts and 0.82 log–0.98 log for oocysts. The coagulation, flocculation, DAF and filtration steps removed more than 2.2 log of cysts and oocysts from the water studied. However, protozoa were detected in the filtered water, even with turbidity values of 0.2 NTU. The recovery of the detection method met the international criteria and was higher when there was no IMS. Including the third acid dissociation in the IMS was critical to improve the performance of the protocol tested. However, there was an increase in the technical and analytical complexity and costs. It was also observed that the efficiency of the treatment was linked to the performance of the selected method of detecting protozoa.

Utilizing Cellulose Nanofibril as an Eco-Friendly Flocculant for Filler Flocculation in Papermaking

Cellulose nanofibril (CNF) is a type of nano-sized cellulosic material with a high aspect ratio and a large specific surface area, which makes it a promising additive to flocculate particles such as fillers. In this study, CNFs were prepared by wet disk-milling with three different degrees of fibrillation. The effect of the CNF on the flocculation of precipitated calcium carbonate (PCC) was elucidated. A photometric dispersion analyzer (PDA) investigated the flocculation phenomena resulting from the interactions between the PCC and the CNF, or polymers, in real-time. The results clearly showed that CNF could be used to control the flocculation behavior of the PCC particles. Scanning electron microscopy (SEM) images showed that the CNFs functioned as bridges between the two PCC particles. A significant reflocculation capability was observed in one- and two-component systems that consisted of CNFs. The addition of cationic starch (C-starch) could induce more efficient flocculation within a two-component system.

Population balance modeling of precipitated calcium carbonate (PCC) flocculation induced by cationic starches

In order to predict and control the flocculation process, it is necessary to develop quantitative model which can describe aggregation, breakage and restructure phenomenon. In this paper, population balance equation was employed to model the PCC flocculation process. Energy dissipation rate was calculated to evaluate the floc strength. It was found, compared to the low charge density starch, the high charge density starch resulted in lower collision efficiency, lower restructure rate and stronger flocs (indicated by higher energy dissipation rate). The higher the temperature, the lower the energy dissipation rate was needed to break the flocs. The addition of NaCl did not show effect on the collision efficiency for both high and low charge density starches, but weaker flocs were formed and more prominent restructure rate was observed at higher NaCl concentration. The collision efficiency decreased with the increase of the shear rate for both starches. At higher starch dosage, lower energy dissipation rate could break the flocs and higher restructure rate was observed.

Cryptosporidium in small water systems in Puerto Rico: a pilot study.

A pilot study was undertaken to investigate the occurrence of Cryptosporidium in four very small drinking water systems supplying communities in rural Puerto Rico. Water samples (40 L) were collected and oocysts were concentrated by calcium carbonate flocculation, recovered by immunomagnetic separation and detected by immunofluorescence microscopy. Cryptosporidium oocysts were identified in all four systems. This is the first report of evidence of the potential public health risk from this chlorine-resistant pathogen in Puerto Rican small water systems. Further work is warranted to fully assess the health risks that Cryptosporidium and other protozoa pose to populations served by community-managed small drinking water systems.

Effect of charge balance and dosage of polyelectrolyte complexes on the shear resistance of mineral floc strength and reversibility

We evaluated the effect of polyelectrolyte complexes (PEC) with varying balance of charges on the flocculation of precipitated calcium carbonate (PCC) particles. PECs composed of polyacrylamides carrying opposite charges (A-PAM and C-PAM) were investigated in terms of PCC floc shear resistance and re-flocculation effects. Light transmission was used in real time to monitor the dynamics of flocculation under shear fields. Compared to the single polyelectrolytes, PECs greatly enhanced particle re-flocculation while minor differences in shear resistance were observed. Shear resistance and re-flocculation depended strongly on the molecular weight and charge ratio of the PEC components. In order to achieve floc stability and re-flocculation conditions a minimum concentration of charge-asymmetric PEC should be applied.

Correlating Aggregates Structure with PEL Characteristics Using an Experimental Design Methodology

Aggregation of particles is fundamental for improving the performance of many solid/liquid processes. Aggregation can be induced by different means, one of the most common being based on the addition of polymeric additives, namely polyelectrolytes (PEL). In this work we have studied the flocculation of precipitated calcium carbonate (PCC), used as filler in papermaking, induced by a range of cationic polyacrylamides with different structures, varying in molar mass and degree of branching. The flocculation process was monitored continuously using the LDS technique. Using an experimental design strategy it was possible to produce a model which allows us to relate the aggregates structure, described by the scattering exponent (SE), with the PEL characteristics and concentration (R2 around 79%). The Partial Least Squares (PLS) regression method was selected to perform the regression, given the significant collinearity among the input variables. The results obtained lead us to conclude that the polymer intrinsic viscosity (related with the PEL molar mass and charge density, and supplying information about the volume of the polymer molecule in the solution) and the degree of branching, are the parameters with a stronger influence on the resulting flocs structure. The PLS model developed was successfully validated using an independent data set, which provides confidence on its consistency and prediction accuracy.

Occurrence, source, and human infection potential of Cryptosporidium and Enterocytozoon bieneusi in drinking source water in Shanghai, China, during a pig carcass disposal incident.

In March 2013, thousands of domestic pig carcasses were found floating in the Huangpu River, a drinking source water in Shanghai, China. To investigate the impact of the pig carcass incident on microbial water quality, 178 river water samples were collected from the upper Huangpu River from March 2013 to March 2014. Samples were concentrated by calcium carbonate flocculation and examined for host-adapted Cryptosporidium and Enterocytozoon bieneusi by ploymerase chain reaction (PCR). Positive PCR products were sequenced to determine Cryptosporidium species and E. bieneusi genotypes. A total of 67 (37.6%) and 56 (31.5%) samples were PCR-positive for Cryptosporidium and E. bieneusi, respectively. The occurrence rates of Cryptosporidium and E. bieneusi in March 2013 (83.3%; 41.7%) and May 2013 (73.5%; 44.1%) were significantly higher than rates in later sampling times. Among the 13 Cryptosporidium species/genotypes identified, C. andersoni and C. suis were the most common species, being found in 38 and 27 samples, respectively. Seventeen E. bieneusi genotypes were found, belonging to 11 established genotypes (EbpC, EbpA, D, CS-8, PtEb IX, Peru 8, Peru 11, PigEBITS4, EbpB, G, O) and six new ones (RWSH1 to RWSH6), most of which belonged to pig-adapted Groups 1d and 1e. EbpC was the most common genotype, being found in 37 samples. The distribution of Cryptosporidium species and E. bieneusi genotypes suggest that dead pigs contributed significantly to Cryptosporidium and E. bieneusi contamination in the Huangpu River. Although most Cryptosporidium species found in river water were not major human pathogens, the majority of E. bieneusi genotypes detected were endemic in China. Data from this study should be useful in the development of strategies in addressing future contamination events in drinking water supplies.

Effect of tempo and periodate-chlorite oxidized nanofibrils on ground calcium carbonate flocculation and retention in sheet forming and on the physical properties of sheets

Nanofibrils (NFC) or microfibrils (MFC) are potential candidates for high filler-loaded papers and board as they are able to compensate for strength loss caused by the filler itself. However, the interaction of nanofibrils and the filler during sheet forming is not yet well understood. The aim here was to examine 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and periodate-chlorite oxidized (DCC) anionic nanofibrils during sheet forming in order to determine their effects on flocculation, filler retention and the strength and optical properties of the handsheets. The experiments were carried out by manufacturing filler-loaded sheets from refined kraft fibres and ground calcium carbonate (GCC) with various added levels of TEMPO and DCC nanofibrils. The results showed that both types of nanofibril caused pronounced agglomeration of the GCC filler, which increased its retention in the paper web. Given the same filler content, the strength properties were the same or slightly better than in a sheet formed without any chemical agent, while light scattering was slightly inferior. Poorer formation seemed to be the explanation for why the increased bonding induced by NFCs was not reflected in obviously better sheet strengths. The physical properties of sheets containing NFC were superior to those of sheets formed with cationic polyacrylamide as a retention aid with the same filler content and level of formation. Thus NFCs seem to be potential retention aids for use in fine paper production instead of traditional polymers.