Coagulation-flocculation Process Research Articles

Role of natural coagulants in the removal of heavy metals from different wastewaters: principal mechanisms, applications, challenges, and prospects

<p>Industrial wastewater has become a great concern due to high concentrations of several hazardous contaminants, particularly heavy metals. Heavy metal contamination and its consequences for human health and the environment have gained interest in developing low-cost, long-term cleanup technologies. Biologically based wastewater treatment approaches being more effective than conventional treatment methods are getting more attention recently. Applying natural coagulants in wastewater treatments has progressively improved the coagulation-flocculation process efficiency. The main mechanism for heavy metals removal by coagulation is adsorption; therefore, natural coagulants perform better than chemical coagulants in heavy metals removal as natural coagulants contain biopolymers with active sites for heavy metals adsorption. This systematic review focuses on applying nature coagulants for heavy metals removal from different environmental systems. A systematic and comprehensive search for related articles on Web of Science, PubMed, and Scopus on the use of natural coagulant for heavy metal removal from wastewater was conducted up to May 2022. After examining, extracting and deleting duplicate records, 81 relevant articles containing data on types of natural coagulants, extraction methods of active compounds, mechanisms of metal removal by coagulation process, and the performance of natural coagulants for the removal of heavy metals have been reviewed. Their major findings with technical gaps and possible solutions are summarized. The review is novel as it summarizes the main findings of a series of previously published articles on the role of natural coagulants, particularly the removal of heavy metals. The review also identified gaps and research questions and suggested possible solutions for the successful practical application of natural coagulants in wastewater treatment.</p>

A comprehensive review on the coagulant recovery and reuse from drinking water treatment sludge.

The main treatment unit in conventional systems for surface water is coagulation-flocculation (CF) process, which consumes huge quantities of coagulant, and produces large volume of sludge. The produced sludge is known as one of the components of water treatment sludge (WTS), which is considered as a global issue and hot topic require careful attention from the plant operators and sludge managers to be managed sustainably with applying an ecofriendly method. Among the suggested technologies, recovery and reuse of coagulants from WTS show the potential to decrease the waste disposal and chemicals usage for drinking water treatment significantly. So, this comprehensive review provides a useful insight into environmental and health problems of WTS, reports the sources, physicochemical properties of sludge, describes different sludge management methods by more focus on coagulant recovery (CR), which significantly point out the different aspects of WTS recovery and reuse, and eventually, economic evaluation of the CR process was also discussed. The results of this review confirm that coagulants can be recovered from WTS by different methods and also will be reused for multiple times in the removal of pollutants from water and wastewater. Moreover, the recovered coagulants can be used as building and construction materials, constructed wetlands substrate and other aims.

Adsorption-desorption of organic micropollutants by powdered activated carbon and coagulant in drinking water treatment

The addition of powdered activated carbon (PAC) and a coagulant during the coagulation-flocculation process is an easy and common option for tackling pollution peaks from organic micropollutants (OMPs) in the production of drinking water. However, the adsorption-desorption mechanisms during this process have not been thoroughly explored. Thus, this research aims to study the mechanisms involved and the impact of the operating conditions when PAC and coagulant are simultaneous used. A commercial PAC with a BET-specific surface area of 961 m2/g, and ferric chloride (FeCl3) were added simultaneously to three different waters spiked with 15 OMPs (pesticides and pharmaceuticals). Different parameters such as PAC and coagulant dosage, pH, contact time and the nature/content of the natural organic matter (NOM) were examined. Results showed that using coagulant + PAC reduced OMP adsorption efficiency, whereas increasing PAC dosage and extending contact time enhanced OMP removal efficiency. Furthermore, a high concentration of NOM affected micropollutant adsorption by competing for adsorption sites. This study highlights for the first time an unexpected phenomenon that significantly affects overall efficiency: i.e. OMPs adsorbed during the slow mixing step that desorbed during the sedimentation step. Desorption sometimes reduced by >30 % the overall efficiency of OMP removal. The parameters that affected efficiency loss were pH, contact time, NOM concentration, and PAC and FeCl3 dosage. Some operational adaptations could be considered regarding these parameters to avoid or reduce desorption, making the process more cost-effective.

The Efficiency Assessment of Poly-Aluminium Chloride (PAC) in Water Treatment Plant Process: A Case Study at Sultan Iskandar Water Treatment Plant, Johor

The rate of population growth and river pollution are significant factors contributing to the increase in water demand in Johor. Generally, this may affect the quality of water treated at one of the biggest water treatment plants in Johor namely Sultan Iskandar Water Treatment Plant (SIWTP). The coverage of SIWTP water supply is wide and comprise almost all area of Pasir Gudang and half of the Johor Bahru district. This situation indirectly affects consumer demand when the treated water is insufficiently supplied by the potable water supply provider due to the use of conventional coagulants in the water treatment plant process. Therefore, this is an initial study as the Poly-Aluminium Chloride (PAC) coagulant is still in the early stages of implementation at SIWTP. It is important to determine the performance of PAC coagulant in the coagulation-flocculation process of the water treatment plant. The PAC performance is compared to Aluminium Sulphate which is a common type of coagulant used in the treatment plant, in order to establish efficiency. A pH adjustment test, turbidity test and the residual Aluminium test were conducted for both coagulants and six jar test readings were recorded to plot the comparison graph between PAC and Alum coagulants. The results showed that PAC is more efficient with 83.74% as compared with Alum which has an efficiency rate of 83.35%. Even though the difference is too small, it is concluded that PAC has better performance and is more efficient compared to Alum due to its better coagulation performance. In addition, PAC produces lesser residual Aluminium and required a lesser amount of dosage. This may reduce cost and therefore save overall operating costs.

Utilization of Sludge from Textile Wastewater Treatment Plants as Raw Material for Iron Coagulant

Treatment of liquid waste using iron coagulant produces a by-product in the form of sludge which requires large handling costs. To reduce environmental pollution and sludge treatment costs, the sludge will be used as raw material for the manufacture of iron coagulant. This study aims to determine whether the sludge from textile WWTP can be used as raw material for iron coagulant. To determine the effectiveness of coagulants made from sludge, this study will compare the results of the coagulation-flocculation process using commercial iron coagulants and iron coagulants made from sludge as well as mixed coagulants with ratios of commercial iron coagulants to iron coagulants made from sludge of 70%, 60%, 50%, 40%, and 30%. The water quality resulting from the coagulation-flocculation process was indicated by pH, color turbidity, Total Dissolved Solid (TDS) and Total Suspended Solid (TSS). The results showed that the water quality of the coagulation-flocculation process was worse when mixed coagulant was used with a smaller ratio of commercial iron coagulant to iron coagulant made from sludge. A mixture of commercial iron coagulant and iron coagulant made from sludge that meets the quality standard for the TSS parameter is a mixed coagulant with a v/v ratio of 70%, while those less than 70% do not meet the quality standard.

Application of a 2k–p Fractional Experimental Design in Coagulation-Flocculation Processes in the Treatment of Wastewater from a Slaughterhouse

Determining the optimal dose of coagulant required to perform flocculation is critical in most water treatment plants’ planning and operation. This study implemented a 2k–p fractional factorial design of experiments to identify the factors influencing the color decrease of wastewater from a slaughterhouse. The variables assessed were the velocity gradient, residence time, primary coagulant dosage, chlorine dosage, and coagulation adjuvant dosage. The results indicate that the primary coagulant dose and the velocity gradient significantly affect the samples’ color and that the other factors can be run at a low technical-economic level to start up the water treatment plant. The fractional factorial design allowed reducing the number of experimental points without affecting the minimum information required to identify which factors are significant in reducing the color of a wastewater sample.

Linkage of pipeline blockage to coagulation-flocculation process: effect of anionic polymer and pH

This study investigated the frequent blockages observed in the discharge pipeline in the chemical mechanical polishing wastewater treatment plant. Preliminary analyses indicated that blockages were predominantly consisted of residual organically-bounded Al due to overdosage of polyaluminum chloride (PACl) and anionic polymer during coagulation-flocculation process. To minimize the recurrence of blockage, jar test experiments were conducted in this study to identify optimum dosages of PACl and anionic polymer as well as optimum pH value. According to the model derived from jar tests, the optimum PACl dosage was dependent on the soluble Cu concentration of wastewater with low initial turbidity [< 1000 nephelometry turbidity units (NTU)]. The PACl dosage would require more than 5 mg L−1 when soluble copper below 20 mg L−1, while PACl is not necessary when more than 20 mg L−1 of soluble copper in the wastewater. On the other hand, optimal PACl dosage was dependent on the initial turbidity of wastewater with high initial turbidity (> 1000 NTU), while the optimal PACl dosage was 30 mg L−1 when initial turbidity around 7000 NTU. The change of pH in the range of 8 to 9.5 did not significantly affect the turbidity or Cu removal, however, higher pH increased the deposition of residual monomeric Al species which might lead to blockage. In summary, controlling PACl dosage at optimum dosage under the conditions of pH 8.5 ± 0.5 and 1 mg L−1 polymer could reduce the blockage occurrence as well as maintain the effluent quality to meet the standards.

Groundwater arsenic contamination: impacts on human health and agriculture, ex situ treatment techniques and alleviation.

Groundwater is consumed by a large number of people as their primary source of drinking water globally. Among all the countries worldwide, nations in South Asia, particularly India and Bangladesh, have severe problem of groundwater arsenic (As) contamination so are on our primary focus in this study. The objective of this review study is to provide a viewpoint about the source of As, the effect of As on human health and agriculture, and available treatment technologies for the removal of As from water. The source of As can be either natural or anthropogenic and exposure mediums can either be air, drinking water, or food. As-polluted groundwater may lead to a reduction in crop yield and quality as As enters the food chain and disrupts it. Chronic As exposure through drinking water is highly associated with the disruption of many internal systems and organs in the human body including cardiovascular, respiratory, nervous, and endocrine systems, soft organs, and skin. We have critically reviewed a complete spectrum of the available ex situ technologies for As removal including oxidation, coagulation-flocculation, adsorption, ion exchange, and membrane process. Along with that, pros and cons of different techniques have also been scrutinized on the basis of past literatures reported. Among all the conventional techniques, coagulation is the most efficient technique, and considering the advanced and emerging techniques, electrocoagulation is the most prominent option to be adopted. At last, we have proposed some mitigation strategies to be followed with few long and short-term ideas which can be adopted to overcome this epidemic.

New pyridyl and aniline-functionalized carbamoylcarboxylic acids for removal of metal ions from water by coagulation-flocculation process

In this work, a library of new aniline and pyridyl functionalized carbamoylcarboxylic acids were synthesized, physicochemically analyzed and evaluated as ligands for the simultaneous removal of environmental interest cations. The effect of the structural characteristics of these functionalized ligands over the simultaneous removal performance of metal ions (Cr3+, Pb2+, Cd2+, Cu2+, Ni2+, Zn2+ and Ca2+) was established. The metal ion-ligand association constants calculated from zeta potential (102 to 104 M−1) and UV–vis (103 to 107 M−1) demonstrate a strong affinity of these ligands towards metal ions. The micro-Jar test for cation removal shows these new functionalized carbamoylcarboxylic acids L1-L12 show average removal efficiencies of 100 % Cr3+, 73 % Pb2+, 42 % Zn2+, 50 % Ni2+, 42 % Cd2+, 39 % Cu2+ and 30 % Ca2+. The quantification of destabilization phenomena through transmittance and backscattering measurements allowed to evaluate the mechanisms of colloidal instability to all ligands. Among the twelve ligands, L9 showed the best removal performance at pH = 4.0 with an overall removal capacity (19.28 mg Mn+ removed/mg of L9), clarification kinetics (55.99 T%/h) and sedimentation ratio (117.6 mm/h). The flocs recovered from the coagulation-flocculation tests were analyzed by scanning electron microscopy and dispersive energy spectroscopy with mapping finding the dispersion patterns of metals on the surface. A BOD5/COD = 0.44 indicates that L9 is a biodegradable compound. Based on the results, aniline and pyridyl functionalized carbamoylbenzoic acids have great potential to be applied in the wastewater treatment industry containing multiple cations.

DESAIN BIOFLOKULAN GELATIN TULANG IKAN LELE (CLARIAS BATRACHUS) UNTUK PENJERNIHAN AIR

Coagulation-flocculation wastewater treatment is widely used because the process is simple to facilitate the sedimentation process. The coagulation-flocculation process aims to alter very small colloidal particles (smaller than 10-3) into larger particles using synthetic or natural materials. The synthetic material is preferred because it does not need to adjust the pH of the media; only small quantities required (from 1-5 ppm), the floc formed is larger, stronger, and has better settling properties. However, it has many shortcomings, including nonbiodegradable, neurotoxic, and carcinogenic properties. Gelatin can be used as an alternative bioflocculant because it has a dual function in the coagulation and flocculation processes. The gelatin production is obtained by utilizing the bone waste of catfish (Clarias batrachus) using the acid method. This study aimed to design gelatin flocculant from catfish bone waste by specifying the intended characteristics such as pH, molecular weight (Mv), non-toxic, and insoluble in neutral pH and determining the effectiveness in purifying water. The method coveredthe production of gelatin using the acid method, determining the properties of gelatin flocculants, performing test of the effectiveness for water purification using the jar test, and calculate the cost. The results showed that gelatin flocculant met the criteria for flocculants with a pH of 5.2, Mv value of 302.648 g/mol, and non-toxic insoluble in neutral pH. The jar test results showed that the administration of a gelatin flocculant dose of 40 mg/L at pH 5.5 was able to reduce the turbidity of the artificial waste from 100 NTU to 28 NTU with a turbidity removal value of 72% with estimated cost of treatment of Rp 4,000 /m3.Keywords: catfish bone waste, flocculation, gelatin flocculant, jar test, molecular weight

Study of the coagulation-flocculation treatment of flowback water from shale gas hydraulic fracturing by using combination of dithiocarbamate compound-polyacrylamide

In this paper, a dithiocarbamate-type flocculant DTC-TETA was prepared by using triethylenetetramine as the material and combination of DTC-TETA and polyacrylamide was used for the coagulation-flocculation of flowback water from shale gas hydraulic fracturing (FWSG). The coagulation-flocculation process was optimized by using turbidity as index and the recommended process was as follows: DTC-TETA dosage 200 mg/L, anionic polyacrylamide AN905 dosage 1 mg/L, flocculation stirring speed 200 rpm, flocculation stirring time 3 min and settlement time 5 min. The turbidity of FWSG can be reduced to be 13 NTU from the initial turbidity of more than 2000 NTU under the recommended process. The performance of DTC-TETA was much better than that of polyaluminum chloride and the Fe2+ in FWSG also can be removed. The function mechanism of DTC-TETA was investigated through the studies of zeta potential change of suspended solids and structural characteristics of flocs. The results confirmed that the flocs were developed by the network formed by the coordination reaction between DTC-TETA and Fe2+, which can filter out suspended solids. This study signifies that both suspended solids and Fe2+ ion can be removed by using DTC-TETA as flocculant, which is a new choice for the FWSG treatment.

Removal of methylene blue (basic dye) by coagulation-flocculation with biomaterials (bentonite and Opuntia ficus indica)

The use of conventional chemical coagulants and flocculants to treat pollutant-laden effluents generates residues with harmful effects on the environment. This has led us to think through this study of their replacement by more ecological natural products. The present work focuses on the use of a bentonite-based coagulant and a cactus-based flocculant (Opuntia ficus indica (OFIP)) in the elimination of a methylene blue (MB), a basic textile dye. The biomaterials are characterized by FTIR, XRD, SEM and pHPZC. To estimate the performance of the biomaterials in the coagulation-flocculation process, jar-test work was performed on the MB dye in aqueous solution. The monitoring of the variation of MB removal rates was performed by UV–visible spectroscopy. The effect of biomaterial masses, stirring time and speed and settling time on the dye removal process were studied. In addition, the effects of pH and initial MB concentration were also studied. The results show that a mass of 0.9 g of bentonite and 0.4 g of OFIP are the optimal quantities, giving a dye removal rate of 98.29 % during 19 min, at a stirring speed of 180 rpm and 40 rpm for coagulation and flocculation, respectively. These optimum values are obtained with a settling time of 15 min. However, pH does not have a significant influence on the MB removal rates. These biomaterials gave excellent results with 98.99 % dye removal rates at an initial MB concentration of 90 mg/L. In addition, for the purpose of testing the performance of the biomaterials, a comparative study using conventional chemicals was performed.

Optimizing coagulation–flocculation processes with aluminium coagulation using response surface methods

A data-based multivariate method such as response surface methods and desirability function is considered advantageous for analysing coagulation treatment optimization. Thus, this study investigated the optimization of coagulation–flocculation using response surface methodology. The parameters investigated were pH, alum dose and alkalinity. The optimum coagulation conditions for the individual responses: turbidity, colour, residual aluminium and phenanthrene were pH 7.0, alum dose 80.0 mg/L and alkalinity 80.0 mg/L; pH, 6.5, alum dose 70.0 mg/L and alkalinity 90.0 mg/L; pH, 7.0, alum dose 63.2 mg/L and alkalinity 80.0 mg/L and pH 6.2, alum dose 80.0 mg/L and alkalinity of 80.0 mg/L, respectively. The model equation derived from the optimization study was adequate for predicting the response values. The quadratic model was significant (p < 0.0001), and it had a high correlation (R2, 0.746–0.975) and an insignificant (LOF, p > 0.05) lack of fit.

Modeling and Optimization by RSM for the Removal of the Dye "Palanil blue R” by Coagulation-Flocculation Process

Modeling and Optimization by RSM for the Removal of the Dye "Palanil blue R” by Coagulation-Flocculation Process

Modelization and optimization of the treatment of the reactive black-5 dye from industry effluents using experimental design methodology

This work investigated the coagulation-flocculation (CF) process of Reactive Black-5 (RB5) dye. The individual effects and interactions of different parameters, which include the pH, coagulant (Ferric chloride), and flocculant dosage (Himoloc DR3000), on the removal efficiency of RB-5 dye were studied. This study aims to build a mathematical model that allows for the representation of the studied responses according to different factors by using the experimental design methodology. The statistical fitness of the developed model was checked using analysis of variance (ANOVA). A second-order quadratic model, with a high determination coefficient (R2 =0.98% and R2=0.80% for chemical oxygen demand (COD) removal and overall cost, respectively), was best fitted to develop the relationship between independent and dependent variables. The results obtained show that the model was highly significant and in good agreement with the experimental results. The optimum conditions obtained for coagulant dose, flocculant dose, and pH were 550 mg/l, 210 mg/l, and 5.4, respectively. Under these optimal conditions, about 98% COD removal and 3.12 $/m3 for effluent treatment were achieved.

Predicting coagulation-flocculation process for turbidity removal from water using graphene oxide: a comparative study on ANN, SVR, ANFIS, and RSM models.

Three artificial intelligence (AI) data-driven techniques, including artificial neural network (ANN), support vector regression (SVR), and adaptive neuro-fuzzy inference system (ANFIS), were applied for modeling and predicting turbidity removal from water using graphene oxide (GO). Based on partial mutual information (PIM) algorithm, pH, GO dosage, and initial turbidity were selected as the input variables for developing the models. The prediction performance of the AI-based models was compared with each other and with the response surface methodology (RSM) model, previously reported by the authors, as well. The models' estimation accuracy was assessed through statistical measures, including mean-squared error (MSE), root-mean-square error (RMSE), mean absolute error (MAE), and coefficient of determination (R2). Among the evaluated models, ANN had the highest estimation accuracy as it showed the highest R2 for the validation data (0.949) and the lowest MSE, RMSE, and MAE values. Furthermore, ANN predicted 76.1% of data points with relative errors (RE) less than 10%. In contrast, the weakest prediction performance belonged to the SVR model with the lowest R2 for both calibration (0.712) and validation (0.864) data. Besides, only 57.1% of the SVR's predictions were characterized by RE < 10%. The ANFIS and RSM models exhibited a more or less similar performance in terms of R2 for the validation data (0.877 and 0.871, respectively) and other statistical parameters. According to the results, the ANN technique is proposed as the best option for modeling the process. Nevertheless, as the RSM technique provides valuable information about the contribution of the independent operational parameters and their complex interaction effects using the least number of experiments, simulating the process by this technique before modeling by ANN is inevitable.

Performance evaluation of Fe-based water treatment sludge for dewatering of iron ore tailings slurry using coagulation-flocculation process: Optimization through response surface methodology

This research attempted to investigate the feasibility of using drinking water treatment sludge (ferric chloride sludge, FCS) as a coagulant for turbidity removal from iron ore tailings slurry. The evaluation was performed in two phases. In the first phase, the one factor at a time (OFAT) approach was used to study the effects of FCS dosage, initial pH, and initial turbidity on turbidity removal efficiency (TR%) and the volume of the sediment produced at the end of the process (SV). In the second phase, response surface methodology (RSM) was employed to assess the individual and interaction effects of the parameters on TR% and SV. Numerical multiple-response optimization was carried out using RSM to maximize TR% and minimize SV simultaneously. At optimum condition (FCS dose of 0.13 g dried FCS/L, initial pH of 10, and initial turbidity of 538 NTU), the removal of all particles in the range of 0.25–1 μm and 2–55 μm from slurry led to the TR% of 78.80% and SV of 0.74 mL (per 250 mL of tailings). Characterization tests indicated that at alkaline pH values, the higher presence of hydroxide compounds intensified the enmeshment in a precipitate or sweep-floc mechanism, which was the predominant removal mechanism in this work. This study demonstrated the remarkable performance of FCS as a coagulant in water reclamation from iron beneficiation wastewater.

Application of Self - Cleaning Filters in the Removal of Turbidity from River Water: Pilot Study

Enhanced treatment of river water was investigated by the modified coagulation-flocculation process for the application of self-cleaning filters (SCF’s) in the removal of turbidity using a combination of Alum and Sudfloc 3880. This study is aimed to improve the removal of iron and turbidity concentrations from river water and reduce water loss. This is achieved by piloting innovative water treatment technologies such as the SCF’s Plant. The new technology further assessed the effectiveness, efficiency, and operability of the SCF’s Plant by varying certain operational parameters such as water flow, differential pressures, coagulant, and flocculent dosages. The results established in this study critically analyze the feasibility of deploying water treatment technologies such as the SCF Plant in areas with similar environmental conditions and/or facing similar water treatment challenges. The removal efficiencies of turbidity were about 40 % and further optimization will be continued until 90 % to 100 % is achieved. The average removal efficiency of turbidity was 40 % and achieved at a 250 m3/h flow rate. The average removal across all flow rates was over 20 %. Further optimization of the RF14 will be carried out using other chemical combinations and formulations at various process settings while bypassing the PLF filters. The PLF elements will be brought into service to further reduce the turbidity after the optimization of the RF14. Keywords: Water, Treatment, Coagulation, Flocculation, Processes, Technologies, Filters *

Textile-effluent treatment using Aloe vera mucilage as a natural coagulant prior to a photo-Fenton reaction

In this study, the mucilage of Aloe vera was used as a new auxiliary coagulant in pre-treatment using a combined system based on the photo-Fenton (PF) process for the treatment of textile effluents. Coagulation–flocculation (CF) using a combination of coagulants showed better performance in the elimination of turbidity, chemical oxygen demand (COD), dissolved organic carbon (DOC), and natural organic matter (NOM) when compared with a single inorganic coagulant. In addition, the combination of coagulants allowed a 28% reduction in the concentration of the inorganic coagulant used. To remove the dissolved and recalcitrant matter after CF, the pretreated effluent was subjected to a PF process that is efficient in the degradation and mineralization of dissolved organic compounds; this resulted in the elimination of 82.48% of COD, 80.34% of DOC, and 79.65% of NOM, as well as the formation of inorganic ions. The toxicity of the samples was evaluated base on three organisms of different trophic levels: Lactuca sativa, Artemia salina, and Eisenia fetida. The results showed that the samples treated by CF or CF/PF were non-toxic to A. salina and E. fetida. However, in the L. sativa bioassay, the root-growth parameter revealed toxicity in the effluents before and after treatment, excluding the untreated effluents with doses of 100 and 200 mL L-1 and the effluent with a dose of 100 mL L-1 treated by the CF process.

Investigation of the Application of Coagulants in Case of Domestic Greywater Fraction

Abstract During our research work, we examined the removal of contaminants from synthetically produced bathing waters using different coagulants and studied the efficiency and the mechanism of coagulation-flocculation processes in detail. In our work, we performed experiments with two different types of coagulants (iron(III) chloride and polyelectrolyte) and compared their efficiencies. The zeta potential and its change were monitored as a qualifying parameter while other water quality parameters were also analyzed. In our experiments, a newly acquired flocculator device was also used to study the coagulation-flocculation processes of larger volume samples. The main goal of our research is to promote the sustainable management of drinking water quality and to study the bathing water reuse possibilities.