Coagulation Flocculation Sedimentation Research Articles

Flow cytometry as a tool for the rapid enumeration of 1-μm microplastics spiked in wastewater and activated sludge after coagulation-flocculation-sedimentation

Considering the limited literature and the difficulty of quantifying 1-μm micro-nanoplastics (1-μm MNP) in complex aqueous matrices such as wastewater and sludge, the removal rate of these very small particles in wastewater treatment plants (WWTP) represents a major challenge. In this study, coagulation-flocculation-sedimentation (CFS) with aluminum salts was investigated to evaluate the removal of 1-μm MNPs spiked in tap water, raw wastewater, pre-settled wastewater, and activated sludge. Quantification of 1-μm MNP was performed using the high-throughput flow cytometry (FCM) analysis which takes only a few minutes and produces results with high accuracy and reproducibly.The results indicated that the 1-μm MNPs were highly stable in pure water and unable to settle rapidly. In raw wastewater, sedimentation without coagulants removed less than 4% of 1-μm MNP. Conversely, CFS treatment showed a significant improvement in the removal of 1-μm MNP from wastewater. At dosages of 0.3-3 mg Al3+/L, the removal of MNPs in wastewater reached 30% and no flocs were observed, while floc formation was visible with increased dosages of 3-12 mg Al3+/L, obtaining MNP removal greater than 90%. CFS in activated sludge with a solids content of 6800 mg MLSS/L registered the highest removal efficiency (95-99%) even for dosages of 0.3-60 mg Al3+/L and pH dropping to 5. However, activated sludge showed extremely high removal efficiency of MNPs (97.3±0.9%) even without coagulants. The large, dense flocs that constitute activated sludge appear particularly efficient in capturing 1-μm MNPs during the sedimentation process even in the absence of coagulants.

Natural coagulants (Moringa oleifera and Benincasa hispida) based removal of microplastics

The presence of small-sized (<5 mm) plastic particles, called microplastics (MPs), in the environment, including aquatic bodies, air, soil, and bodies of living beings, is a cause of significant concern to the entire world. These MPs can contaminate drinking water sources, move up the food chain, and release toxic substances that could pose a threat to human health. Therefore, there is an urgent need to develop methods for removing MPs from the environment to protect present and future generations. The coagulation-flocculation sedimentation (CFS) process (using synthetic chemicals) has emerged as a fundamental method for treating MPs in water because of its economy, high efficiency, and ease of use. However, the xenobiotic nature of such compounds, coupled with their adverse health effects, calls for the development of sustainable solutions. This is the first study to report the effectiveness of plant-based natural coagulants in removing MPs from water and their comparison against synthetic coagulants. Two natural coagulants, Benincasa hispida (BH) and Moringa oleifera (MO), were investigated and have shown comparable MP removal efficiencies to commonly used synthetic coagulant: alum. The CFS approach resulted in 83.73 ± 1.41% (100 mg L–1 dosage) and 86.99 ± 1.41% (150 mg L–1 dosage) MP removal efficiencies for BH and MO, respectively, while alum resulted in 86.58 ± 1.22% removal (50 mg L–1 dosage). Further, FTIR analysis has revealed that these MPs are composed of high-density polyethylene (HDPE), and SEM imaging has shown their shapes as spherical, rod-like and irregular. The results of the present study show that plant-based natural materials can be used for MP removal, thus yielding a sustainable and cost-effective process.

Coagulative removal of polystyrene microplastics from aqueous matrices using FeCl3-chitosan system: Experimental and artificial neural network modeling

Effluent from sewage treatment plants (STPs) is a significant source of microplastics (MPs) re-entry into the environment. Coagulation-flocculation-sedimentation (CFS) process as an initial tertiary treatment step requires investigation for coagulative MPs removal from secondary-treated sewage effluents. In this study, experiments were conducted on synthetic water containing 25 mg/L polystyrene (PS) MPs using varying dosages of FeCl3 (1–10 mg/L) and chitosan (0.25–9 mg/L) to assess the effect of process parameters, such as pH (4−8), stirring speed (0–200 rpm), and settling time (10–40 min). Results revealed that ∼89.3% and 21.4% of PS removal were achieved by FeCl3 and chitosan, respectively. Further, their combination resulted in a maximum of 99.8% removal at favorable conditions: FeCl3: 2 mg/L, chitosan: 7 mg/L, pH: 6.3, stirring speed: 100 rpm, and settling time: 30 min, with a statistically significant (p < 0.05) effect. Artificial neural network (ANN) validated the experimental results with RMSE = 1.0643 and R2 = 0.9997. Charge neutralization, confirmed by zeta potential, and adsorption, ascertained by field-emission scanning electron microscope (FESEM) and Fourier-transform infrared spectroscopy (FTIR), were primary mechanisms for efficient PS removal. For practical considerations, the application of the FeCl3-chitosan system on the effluents from moving bed biofilm reactor (MBBR) and sequencing batch reactor (SBR)-based STPs, spiked with PS microbeads, showed > 98% removal at favorable conditions.

Pilot-scale study on the performance of high-rate DAF based on removal of organic precursors and formation characteristics of disinfection by-products

In recent years, there has been an increased focus on the design and development of dissolved air flotation (DAF) with a high surface loading rate (SLR), but little research has been conducted using advanced natural organic matter characterization techniques. This research thus investigates the performance of pilot-scale DAF (10–30 m h–1) and compares them with those for a full-scale coagulation–flocculation–sedimentation (CFS) system based on the reduction of organic precursors, different molecular weight (MW) fractions characterized by liquid chromatography with organic carbon detection, and disinfection by-products. The removal of dissolved organic carbon (DOC) decreased with increasing SLR, ranging from 29 % to 38 %. This may be because of the short flocculation retention time for high SLR. Thus, achieving a similar removal of DOC by high SLR required higher coagulant doses. Furthermore, the organic precursors were measured lower in the high-rate DAF effluent than the CFS, maybe because of the high coagulation pH of the CFS effluent (7.5–8). Similarly, the concentration of different MW fractions, especially biopolymers and building blocks, was lower in the high-rate DAF effluent than in the CFS. The removal of biopolymers was 74.64 % and 87.20 % for the CFS and high-rate DAF, respectively. Likewise, 2.78 % and 27.09 % for the CFS and high-rate DAF, respectively, for building blocks. The normalized trihalomethanes/DOC and chloralhydrate/DOC were higher for the CFS than the high-rate DAF. Coagulation chemistry (pH, coagulant doses, and retention time) strongly influences the DAF and CFS unit performance and should not be neglected.

Comparing Sedimentation, Flotation, and In-Line Pretreatment for Low-Pressure Membrane Fouling Reduction

Feed water pretreatment commonly is required for low-pressure membrane technologies employed in drinking water treatment applications to reduce membrane fouling and create stable operating conditions. Comparatively few studies have investigated coagulation–flocculation–dissolved air flotation (CF-DAF) pretreatment for drinking water applications, and none have compared CF-DAF, coagulation–flocculation–sedimentation (CF-S), and in-line coagulation (CF-IN) pretreatments using the same water. This study compared these three pretreatments for the filtration of a high dissolved organic carbon (DOC), high hydrophobic (HPO) surface water using a hydrophilic polyvinylidene fluoride (h-PVDF) ultrafiltration (UF) fiber. Multiday filtration tests were carried out using an automated bench-scale testing system operated in an outside-in configuration. CF-S and CF-DAF were found to be equally effective at mitigating membrane fouling, although CF-DAF pretreated water had a lower residual DOC and the greatest removal of UV254 absorbent organics. Compared with CF-DAF and CF-S, CF-IN pretreatment resulted in higher levels of total and irreversible fouling regardless of the applied coagulant dose. For all the pretreatments studied, irreversible membrane fouling was found to be strongly dependent on both the hydrophobicity of the feed water [in terms of specific UV absorbance (SUVA)] and the concentration of the 5–10-kDa DOC fraction, suggesting that the HPO humic organics were the principal foulant for this membrane–water combination. CF-IN pretreatment performance also was strongly impacted by the feed water zeta potential, suggesting that the characteristics of the formed flocculant particles are critical to the fouling behavior of the hybrid CF-IN-UF system.

Reduced Low-Pressure Membrane Fouling by Inline Coagulation Pretreatment for a Colored River Water.

Drinking water treatment (DWT) using low-pressure membranes (LPM) has become increasingly popular due to their many reported advantages compared to conventional technologies. Productivity decline due to fouling has prevented LPMs from becoming the technology of choice in DWT, however, coagulation pretreatment either with or without particle separation mitigates fouling phenomena. The effectiveness of coagulation/flocculation/sedimentation (CF-S), coagulation/flocculation/dissolved air flotation (CF-DAF), and inline coagulation (CF-IN) as technologies for pretreatment of feed water has rarely been investigated using the same water source. In this study, CF-S, CF-DAF, and CF-IN are directly compared as pretreatment of a tubular multi-channeled ultrafiltration (UF) membrane using the same highly colored river water. Three-day long filtration tests were performed using an automated bench-scale filtration apparatus with an inside-out configuration. Although CF-DAF had the greatest removal of dissolved organic matter (DOM) and hydrophobic organics, CF-S pretreatment resulted in a similar level of total fouling. Compared to CF-DAF and CF-S, CF-IN pretreatment resulted in lower fouling. The hydraulic and chemical reversibility of CF-IN fouling was seen to be strongly influenced by the feed water zeta potential, suggesting the importance of floc electrostatic and morphological characteristics on inline coagulation performance.

Use of Aloe vera as an Organic Coagulant for Improving Drinking Water Quality

The coagulation–flocculation–sedimentation process is widely used for removal of suspended solids and water turbidity reduction. The most common coagulants used to conduct this process are aluminum sulfate and ferric sulfate. In this paper, the use of Aloe vera as a natural-based coagulant for drinking water treatment was tested. The bio-coagulant was used in two different forms: powder as well as liquid; the latter was extracted with distilled water used as a solvent. The obtained results showed that the use of the natural coagulant (Aloe vera) in both powder (AV-Powder) and liquid (AV-H2O) forms reduced the water turbidity at natural pH by 28.23% and 87.84%, respectively. Moreover, it was found that the use of the two previous forms of bio-coagulant for drinking water treatment had no significant influence on the following three parameters: pH, alkalinity, and hardness. The study of the effect of pH on the process performance using Aloe vera as a bio-coagulant demonstrated that the maximum turbidity removal efficiency accounted for 53.53% and 88.23% using AV-Powder and AV-H2O, respectively, at optimal pH 6.

Removal of polystyrene microplastic spheres by alum-based coagulation-flocculation-sedimentation (CFS) treatment of surface waters

• Real river and lake water with carboxylated PS microplastics were treated via CFS. • Higher alum doses generally benefited the removal of PS microplastics ≤ 90 μm. • Smaller PS microplastics were better removed by alum CFS treatment. • Water source affected the removal efficiency of PS microplastics. • PS microplastics did not impact the removal of turbidity, NOM fractions, or metals. Microplastics are an emerging issue in water systems, and an understanding of their occurrence and behavior is complicated by a high diversity in physical (i.e., size and shape) and chemical characteristics. To date, there have been limited studies on microplastics in drinking water treatment processes. As the coagulation-flocculation-sedimentation (CFS) process is the first step of the particle/colloid removal at many plants, its ability to remove microplastics requires further investigation. By performing alum-CFS bench tests, this study examined the removal of carboxylated polystyrene (PS) microspheres in a wide size range (3, 6, 25, 45, and 90 μm) in two types of real surface waters (Grand River and Lake Erie water) that are sources for full-scale drinking water treatment plants. Based on experiments using water from the Grand River with a variety of alum doses (10, 20, 30, 40, and 50 mg/L), a higher alum dose generally led to better removal of microspheres smaller than 90 μm, while an alum dose > 30 mg/L did not substantially improve the removal of particles between 3 and 25 μm. Further experiments indicated that smaller PS microspheres were more effectively removed in both river (Grand River_Dec 06) and lake water (Lake Erie_Nov 29). For example, with an alum dose of 30 mg/L, 75.6 and 85.2% of the 6-μm PS microspheres were removed from Grand River and Lake Erie water, respectively. Moreover, the water source significantly (p = 0.0021) affected the removal of PS microspheres, which may have been primarily related to the difference in turbidity. No impacts of PS microspheres were observed on the removal efficiency for turbidity, natural organic matter fractions, or major metal elements by alum-CFS treatment.

Efficient recovery of phosphorus and sulfur from Anaerobic Membrane Bioreactor (AnMBR) permeate using chemical addition of iron and evaluation of its nutrient availability for plant uptake

Anaerobic membrane bioreactors (AnMBRs) represent an emerging environmental biotechnology platform with the potential to simultaneously recover water, energy, and nutrients from concentrated wastewaters. The removal and beneficial capture of nutrients from AnMBR permeate has yet to be fully explored, therefore this study sought to foster iron phosphate recovery through a tertiary coagulation process, as well as characterize the recovered nutrient product (RNP) and assess its net phosphorus release, diffusion, and availability for plant uptake. One of the primary goals of this study was to optimize the dose of the coagulant, ferric chloride, and coagulant aid, aluminum chlorohydrate (ACH), for continuous application to the coagulation-flocculation-sedimentation (CFS) unit of an AnMBR pilot plant treating municipal wastewater, through controlled bench-scale jar tests. Anaerobic systems present unique challenges for nutrient capture, including high, dissolved hydrogen sulfide concentrations, along with settleability issues. The addition of the coagulant aid increases settleability, while enhancing phosphorus removal by up to 20%, decreasing iron demand. Water quality analysis indicated that a variety of factors affect nutrient capture, including the COD (chemical oxygen demand) concentration of the permeate and the limiting coagulant dose. COD >200 mg/L was shown to decrease the phosphorus removal efficiency by up to 15%. A combination of inductively coupled plasma optical emission spectrometer (ICP-OES) elemental analysis, inductively coupled plasma mass spectrometer (ICP-MS) elemental analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) spectroscopy analysis was used to characterize the P-rich RNP which revealed a 2.58% w/w phosphorus content and the lack of a well-defined crystalline structure. Detailed studies on resin extractable phosphorus to assess the plant uptake potential also demonstrated that iron-based P-rich RNPs may not be an effective fertilizer product, as they can act as a phosphorus sink in some agricultural systems instead of a source.

PÓS-TRATAMENTO DE LIXIVIADO ESTABILIZADO POR CICLO COMPLETO, ADSORÇÃO E OXIDAÇÃO QUÍMICA

The leachatefrom landfillhas high concentrations of organic matter, humic and nitrogenous compounds, heavy metals and inorganic salts, which requiresproper treatment for its final destinationand does not cause damage to the environment. Studies show that the biologically treated effluent requires an association of physical-chemical techniques.Thisstudy aimed to evaluate the application of complementary techniques to thebiological treatmentsuch as coagulation-flocculation-sedimentation(CFS)andFenton's reaction oxidation(FR), followed by adsorption. The CFS with ferric chloride and FRpost-treatments isolated had100% and 87,9%, organic mattercorrelated with true color removal and 53,6% and 67,0% of CODremoval,which meetwiththe requirements of CONAMA 357/05 e 430/11 for disposal in water bodies. The adsorption after Fenton reaction resulted in 84,5% organic matter correlated with true color removal and 67,0% of CODremoval. Adsorption after coagulation-flocculation-sedimentation was able to reduce 76,9% of COD. CFSshowed higher removal efficiency of organic matter correlated to the true color, while RFobtained higher removal efficiency of NKT, N-ammoniacal and COD parameters. The biologically treated leachate did not show significant toxicityacute to the test organism saline artemia, however, after the post-treatment, acute ecotoxicity in the limits established by CEMA 81/10.

Controlling harmful algal blooms (HABs) by coagulation-flocculation-sedimentation using liquid ferrate and clay

Harmful algal blooms (HABs) occur worldwide and threaten the quality of marine life, public health, and membrane facilities in Seawater Reverse Osmosis (SWRO) desalination plants. The effects of HABs on seawater desalination plants include extensive membrane fouling, increased coagulant consumption and plant shutdown. To determine how to mitigate such effects, this study assessed if low doses (0.01 mg/L, 0.10 mg/L, and 1.00 mg/L) of liquid ferrate (58% yield) and kaolin or montmorillonite clays alone could remove algal organic matter in coagulation-flocculation-sedimentation (CFS) pretreatment desalination systems. Results showed that 0.01 mg/L of liquid ferrate coagulant removed 42% of dissolved organic carbon (DOC), 52% of biopolymers (BP), 71% of algal cells, and 99.5% of adenosine triphosphate (ATP). At a dose of 0.01 mg/L, clays exhibited high removal of turbidity (up to 88%), BP (up to 80%) and algal cells (up to 67%). The combination of liquid ferrate (58% yield) as a coagulant with kaolin or montmorillonite clays as coagulant aids in CFS pretreatment led to 72% removal of DOC, 86% of BP, and 84% of algal cells with a fixed dose of 0.01 mg/L for each. Findings from this study can help SWRO plants improve the performance of pretreatment systems during algal bloom events by reducing the consumption of coagulants while also maintaining high removal efficiencies.

Coagulation-flocculation followed by catalytic ozonation processes for enhanced primary treatment during wet weather conditions

Combined sewer overflows (CSO), generated during the wet weather flow from the combination of the inflow and stormwater runoff in sewer system, result in an overflow of untreated wastewater from sewer system, which might ultimately contain different micropollutants (MPs). In this study, a coagulation-flocculation-sedimentation (CFS) pretreated CSO spiked with MPs was treated by catalytic ozonation using carbon, iron, and peroxide-based catalysts. The catalysts were characterized and their activity on MPs removal was studied at two different ozone (O3) doses (5 and 10 mg L−1). The effect of the treatment on the spiked CSO effluent was also assessed from the acute toxicity of the effluent using Microtox®, Yeast, and Macrophage cell-line toxicity assay tests. All the carbon-based catalysts showed large surface area, which was strongly influenced by the activation technique in the preparation of the catalysts. The CFS treatment strongly reduced the turbidity (≥60%) but had marginal effect on the UV254, dissolved organic carbon (DOC), and pH. Sludge Based Carbon (SBC) showed strong adsorption capacity (≥60% removal efficiency) for all MPs studied compared to other carbon and iron-based catalysts. Ozonation alone was effective for the degradation of easily oxidizable MPs (sulfamethoxazole, mecoprop, and 2,4-dichlorophenoxyl acetic acid), achieving more than 80% degradation efficiency at 10 mg L−1 of ozone, but not effective for atrazine (≤60% degradation efficiency) at similar O3 dose. Catalytic ozonation (at 10 mg L−1 O3 dose) improved the degradation of the MPs at low catalyst dosage but higher dosage strongly inhibited their degradation. In all cases, the effluents showed negligible acute toxicity, indicating the suitability of the process for the treatment of CSO.

Lead and Zinc Smelting Wastewater Treatment and Reclamation by Coagulation-Flocculation-Sedimentation, Ultrafiltration and Reverse Osmosis Technique

The typical smelting wastewater is with characteristics of high concentration of TDS, conductivity, heavy metal ions, and low concentration of COD. The ultrafiltration (UF) and reverse osmosis (RO) is an attractive technology to reclaim and reuse this kind of wastewater. In this work, Coagulation-flocculation-sedimentation (CFS) and multi-media filter (MMF) was used as the pretreatment processes. UF, RO and concentration RO (CRO) processes was applied as the advanced treatment processes to reclaim the smelting wastewater. To enlarge the recovery of RO and CRO units, the influences of increasing the feed temperature by waste heat from the smelting plant and the feed pressure by change the operating frequency of the high pressure pumps were investigated. The optimize operation parameters of RO and CRO units were obtained. To understand the operation CIP cycle time of UF, RO and CRO membrane units in a long term operation, the trans-membrane pressure (TMP) and permeate flux difference were investigate. Good system operation stability, permeate flux recovery after CIP and qualified treated water were obtained in the recommend operation parameters. The results of this work can benefit to the designing of reclaiming the smelting wastewater by UF-RO-CRO approach within the Lead and Zinc smelting industrial application.

Efficiency analysis of enhanced Sb(V) removal via dynamic preloaded floc in coordination with ultrafiltration

Sb(V) can cause chronic or acute poisoning to animals and plants; Unfortunately, traditional coagulation–flocculation–sedimentation (CFS) process has limited effect on Sb removal. In this study, flocs produced by CF process were preloaded on the surface of the UF membrane, and the coordinated coagulation-floc preloaded-ultrafiltration (CFPLU) process was proposed. The removal effect of the CFPLU process on composite pollutants and the fouling degree of the UF membrane were studied under different solid contents of floc-preloaded water samples. Moreover, the removal mechanism of Sb(V) and membrane fouling mechanism in CFPLU process were also investigated. The results indicated that, compared with the CFS process, UF process, CF ultrafiltration (CF-UF) process, preloaded UF (PL-UF) process, the CFPLU process has the highest removal rate for Sb(V) and the lowest degree of membrane fouling. When the solid content is 1.5%, Sb(V) removal rate reaches the highest value of 97.29% and Sb(V) concentrations of CFPLU under all solid contents are < 5 μg/L and. The preloaded floc layer on the surface of UF membrane has adsorption and interception effects generated via electrostatic forces and chemical bonds. Furthermore, the preloaded floc layer can serve as a barrier toward the surface of the UF membrane, and then reduce the chance of the UF membrane-contacting contaminants such that membrane fouling is effectively alleviated. Thus, the CFPLU process not only enhances the removal of contaminants and mitigates membrane fouling but also provides new ideas for disposing coagulated sludge, which reduces the energy consumption of sludge disposal and realizes resource utilization.

Trihalomethane precursor reactivity changes in drinking water treatment unit processes during a storm event.

Source water quality can significantly impact the efficacy of water treatment unit processes and the formation of chlorinated and brominated trihalomethanes (THMs). Current water treatment plant performance models may not accurately capture how source water quality variations, such as organic matter variability, can impact treatment unit processes. To investigate these impacts, a field study was conducted wherein water samples were collected along the treatment train for 72 hours during a storm event. Systematic sampling and detailed analyses of water quality parameters, including non-purgeable organic carbon (NPOC), UV absorbance, and THM concentrations, as well as chlorine spiking experiments, reveal how the THM formation potential changes in response to treatment unit processes. Results show that the NPOC remaining after treatment has an increased reactivity towards forming THMs, and that brominated THMs form more readily than chlorinated counterparts in a competitive reaction. Thus both the reactivity and quantity of THM precursors must be considered to maintain compliance with drinking water standards, a finding that should be incorporated into the development of model-assisted treatment operation and optimization. Advanced granular activated carbon (GAC) treatment beyond conventional coagulation-flocculation-sedimentation processes may also be necessary to remove the surge loading of THM-formation precursors during a storm event.

Pulp and Paper Mill Effluent Treated by Combining Coagulation-Flocculation-Sedimentation and Fenton Processes

Pulp and paper industries face serious environmental challenges, especially with regard to the conservation of water resources. Chemical thermal mechanical pulping (CTMP) is a process of pulping that combines chemical and mechanical pulping. This reduces the volume of water used in the process. But on the other hand, CTMP generates an effluent with high concentration of organic matter and is difficult to treat. This study evaluated the efficiency in the combination of physicochemical pretreatment by coagulation-flocculation-sedimentation (CFS) process and advanced oxidation process (AOP) by Fenton in sequence to treat CTMP effluent of a Brazilian industry. At first, the best treatment conditions for this type of effluent were determined. To evaluate the efficiency, pH, chemical oxygen demand, biochemical oxygen demand, total organic carbon, lignin contents, color, total phenolic contents, turbidity, and solids were measured before and after treatment. The acute toxicity on Daphnia magna was also determined. The treatment with CFS showed better results in the removal of solids and Fenton in the removal of recalcitrant compounds, such as lignin, demonstrating the need to use them in sequence. Combining CFS and Fenton to treat CTMP effluent allowed to achieve a removal efficiency of 95% for TOC, 61% for COD, and 76% for lignin contents.

Removal of antimonate (Sb(V)) and antimonite (Sb(III)) from aqueous solutions by coagulation-flocculation-sedimentation (CFS): Dependence on influencing factors and insights into removal mechanisms

This study investigates the effects of different influence factors on the removal of inorganic Sb species using coagulation-flocculation-sedimentation (CFS) and establishes the mechanism of the process. Thus, the influence of pH, initial Sb concentrations, coagulant dosages and competitive matters on Sb(V) and Sb(III) removal via CFS with polymeric ferric sulfate (PFS) was investigated systemically. Competition experiments and characterization methods, including X-ray diffraction (XRD), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS), were performed to determine the mechanisms of the process. The main conclusions included: (i) Optimum Sb removal was observed at a pH range of 4–6 and dosages of 4 × 10−4 mol/L and 8 × 10−5 mol/L for Sb(V) and Sb(III), respectively. Additionally, both Sb(V) and Sb(III) removal could be inhibited by the presence of phosphate and humic acid (HA). (ii) A higher priority was observed for the removal of Sb(III) over Sb(V). (iii) After excluding precipitation/inclusion/occlusion, coprecipitation involving chemical bonding played a significant role in both Sb(V) and Sb(III) removal, and electrostatic force served another significant role in Sb(V) removal. The Sb(V) and Sb(III) contamination in real contaminated waters was successfully removed using PFS via CFS process. The results of this study provide insights into the removal mechanisms of inorganic Sb species via CFS.

Removal of microalgae from seawater using chitosan-alum/ferric chloride dual coagulations

During algal bloom, it's a challenge to provide good quality feed water, and ensure sustainable RO plant operations without an adequate pre-treatment of seawater. In this paper, the effectiveness of the coagulation process with the individual and dual coagulants, using alum, FeCl3 and chitosan, were explored aiming to remove microalgae from seawater. The coagulation-flocculation-sedimentation (C-F-S) experiments were conducted by optimizing multiple process strategies to reduce the amounts of coagulants and also to shorten the sedimentation process time. The coagulation-flocculation-dissolved air flotation (C-F-D) experiments were performed to generate the process data in order to evaluate the dual coagulation process performance of the C-F-S system. C-F-S experiments using FeCl3 coagulant gave better process performance (20 ppm FeCl3 dose, 8.2 pH, 30 min sedimentation time and 98% microalgae removal efficiency) when compared to alum and chitosan based individual coagulations. The process time of the coagulation process was significantly reduced by the addition of chitosan as a flocculent aid. For dual coagulation using alum (10 ppm) as coagulant and chitosan (1 ppm) as flocculent aid improved microalgae removal efficiency to 98% at a reduced process time of 5 min, making C-F-S process as attractive as C-F-D process.

Coagulation/Flocculation with Moringa oleifera and Membrane Filtration for Dairy Wastewater Treatment

The main objective of the present paper is to evaluate the use of Moringa oleifera (MO) as a natural coagulant in coagulation/flocculation/sedimentation (CFS) followed by the microfiltration (MF) or nanofiltration (NF) process in dairy wastewater treatment, focusing on determining the best association of treatments that can generate wastewater for reuse purposes. The association of CFS-MF-NF treatments showed a high removal efficiency for chemical oxygen demand (COD) (mean of 96%), turbidity, and color (mean of 99%) meeting water reuse standards, allowing the reutilization of the wastewater, in relation to the analyzed parameters. The results indicate a lower membrane fouling rate (63%), an increase in permeate flow, and better quality of the permeate, proving that the CFS-MF-NF treatment is the most suitable among all the tested treatments. Finally, the treated wastewater obtained with this process presents better quality than the wastewater obtained with the conventional treatments.

Considering energy efficiency in filtration of engineering nanoparticles

Engineering nanoparticles (ENPs) are an integral part of consumer products. Released to the atmosphere or disposed to sewage, ENPs quickly penetrate to surface and ground water sources. An absence of a dedicated ENP-retaining water treatment strategy imposes a potential health threat on drinking water consumers. The threat is met by gearing up an upgrade of treatment systems towards membrane filtration that provides a better barrier to ENP penetration at higher energy costs. The current study compares the energy demand of granular and membrane filtrations, with the retention efficiency of inorganic and organic ENPs. Dedicated experiments with gold and silver nanoparticles, dyed viruses, proteins, polysaccharides, and plasmid DNA showed that the energy demand increases from slow to river bank to rapid sand filtration, and to membrane ultrafiltration (UF). The UF alone consumes on average two times more energy than the entire coagulation–flocculation–sedimentation–sand filtration tray. The differences in retention efficiency however are much less pronounced. The traditional retention tray requires 0.4–0.45 kWh per m3 of effluent (kWh/m3) to provide between 90% and 99% (1 and 2 logs) ENP retention; 1 kWh/m3 on average is needed to secure the retention of 99.9% (3 log) ENPs by UF.