Aluminum Coagulants Research Articles

Effects of Chelators on Fluoride Removal by AlCl3 and Al13 Coagulation: Performance and Mechanism.

Aluminum (Al) coagulation is one of the most widely used techniques for the defluoridation of industrial effluents. This study examined the influence of two common chelating agents, i.e., ethylenediaminetetraacetic acid (EDTA) and citric acid (CA), on fluoride removal during coagulation using monomeric Al (AlCl3) and polymeric aluminum species [Al13O4(OH)24(H2O)127+, Al13]. The results revealed that EDTA reduced the fluoride removal efficiency by up to 95.4% with AlCl3 and by 28.3% with Al13. In contrast, CA inhibited fluoride removal by up to 100% with AlCl3 and 90.6% with Al13. Both chelators impaired fluoride removal primarily by disrupting floc formation. Advanced analytical techniques, including 19F/27Al NMR spectroscopy combined with DFT calculations, demonstrated that this interference was due to the formation of EDTA-Al-F ternary complexes and Al-CA binary complexes. Additionally, the formation of a bridging fluoride (μ-F) in the Al13 structure enhanced its thermodynamic stability against chelators. Specifically, Al13 maintained structural stability even in the presence of up to 1.50 mmol/L EDTA, whereas CA progressively destabilized the Al13 structure by forming soluble Al-CA complexes. These findings are believed to help guide the rational design of Al-based coagulants and optimize water treatment strategies aimed at defluoridation of industrial effluents.

Comparative study of the removal of urea by electrocoagulation and electrocoagulation combined with chemical coagulation in aqueous effluents

AbstractUrea is a major issue in human wastewater because it may be easily broken down by the urease enzyme produced by bacteria, leading to ammonia production. Due to its ability to increase soil pH and eutrophicate streams, ammonia-containing effluent emissions pose environmental and health risks. This study aimed to evaluate the effectiveness of various treatment approaches in reducing urea concentrations by comparing the removal rates of conducting electrocoagulation (EC), EC followed by chemical coagulation (EC-CC), and CC followed by electrocoagulation (EC-CC). Numerous electrocoagulation parameters have been investigated, including current density, electrode gap distance, electrolyte type, concentration, and electrolysis duration. The electrode morphology was examined using a scanning electron microscope, while the produced sludge was analyzed using Fourier transform infrared spectroscopy. Three kinds of aluminum coagulants—potash alum, aluminum sulfate, and aluminum chloride—were used in the chemical coagulation, while the electrocoagulation was optimized at 30 A/m2. The results of this investigation suggest that the application of EC-CC, regardless of the type of coagulant used in both synthetic and real effluent, could marginally improve the efficacy of urea removal. Conversely, CC-EC exhibits an adverse effect on the efficiency of urea removal in both synthetic and real wastewater. The application of CC-EC demonstrated a significant improvement in the effectiveness of COD removal from actual wastewater, according to experimental results. The study emphasized the effectiveness and economic advantages of electrocoagulation over EC-CC and CC-EC techniques, used to remove urea from both real and synthetic wastewater.

Direct filtration system composed of coconut fiber as a filtering medium in water treatment

The use of inorganic coagulants has sparked discussions regarding the potential consequences on human health. In contrast, polymeric coagulants derived from tannin compounds show promise in water treatment. An important issue is the use of alternative materials in the construction of filters used in water treatment, such as those made with coconut fiber. The objective of this study was to compare the performance of sand filters (F1) with coconut fiber filters (F2), as well as the use of the inorganic coagulant aluminum sulfate (C1) compared to the organic tannin (C2). The tests were performed in duplicate, and the parameters pH, electrical conductivity, apparent color, and turbidity were evaluated using R software. The results showed that the pH was not altered and that the electrical conductivity decreased after the application of both coagulants, with F2 achieving a reduction of up to 73.4% using tannin. For turbidity, F2 achieved removals of 95.44% and 81.35% for C2 and C1, respectively. When analyzing the apparent color, F2 removed 85.38% using C2 and 55.38% with C1, demonstrating the efficiency of the coconut fiber filtering material. However, the use of a large amount of water for cleaning this filter becomes a problem and an issue to be addressed.

Reduction of organic matter and disinfection by products formation at surface water treatment plants in Egypt

ABSTRACT Although the removal of colloidal particles continues to be an important reason for using coagulation, currently a newer approach, the removal of organic matter to reduce the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs) are suspected carcinogens. Inefficient removal of total organic carbon (TOC) leads to the formation of carcinogenic THMs. This motivates the research efforts to find a way to reduce them in potable water. The first objective of this research is monitoring the water quality (raw and produced) for selected three water treatment plants within Giza Governorate to reveal the most polluted site (high TOC in the raw water and THMs in the treated water) in the study areas. The second objective of this study is enhancing coagulation to reduce TOC and THMs from surface water treating. In this study, two different coagulants aluminum sulfate (alum), and ferric chloride were tested under different conditions of pH and coagulant concentration to determine their effectiveness for removal of TOC, THMs and turbidity. Optimum values for the mentioned conditions were used to achieve the maximum reduction for TOC and THMs in Al-Ayat drinking water treatment plant (DWTP) which recorded the highest concentration of TOC and THMs. Ferric chloride as a coagulant achieved the maximum removal percentage % of TOC, THMs and turbidity as 79%, 82% and 94%, respectively, at ferric chloride dose 100 mg/L, while alum as a coagulant recorded the maximum removal percentage % of TOC, THMs and turbidity as 46%, 52% and 91%, respectively, at alum dose 100 mg/L. The results indicated that ferric chloride as a coagulant has the highest efficiency reduction of TOC, THMs and turbidity if compared to alum with the same dose added.

Formation of Aluminum-Fluoride Complexes Compromises Defluoridation Efficiency of Aluminum-Based Coagulation.

Aluminum-based coagulation has long been regarded as a reliable and cost-effective process for the defluoridation of industrial effluents. However, such a well-recognized viewpoint is challenged by the underestimation of fluoride levels in treated effluents. Herein, we developed a systematic protocol to distinguish different fluoride species, including free F-, exchangeable fluoride (EF), and nonexchangeable fluoride (NEF). We demonstrated that EF forms complexes with octahedral aluminum (AlO6) on the surface of polyaluminum and can be exchanged with (1,2-cyclohexylenedinitrilo)-tetraacetic acid (CDTA). However, NEF is incorporated with tetrahedral aluminum (AlO4) at the core of polyaluminum, as confirmed by 19F/23Al NMR and ESI-MS analysis, and cannot be exchanged with CDTA due to steric hindrance. Increasing the aluminum coagulant dosage effectively reduced free F- levels in photovoltaic and electroplating effluents to below 1 mg/L. However, the total fluoride content, with over half in the form of EF and NEF, was above 2 mg/L, exceeding the discharge limit regulated by many local governments of China. Furthermore, both EF and NEF can gradually transform to free F- in natural waters. Our findings indicate that aluminum-based coagulation inevitably accompanies the formation of substantial amounts of EF and NEF, compromising its defluoridation efficiency toward industrial effluents.

Comparative study of iron and aluminium coagulants in conditioning sludge: Sludge dewatering performance, physicochemical properties, and risk of heavy metal migration

Inorganic coagulants are essential agents that can facilitate the sludge deep dewatering, but comprehensive comparative research of commonly used coagulants is lacking. The systematic comparison of six coagulants, including Ferric Chloride (FeCl3), Polymeric Ferrous Sulfate (PFS), Ferrous Sulfate (Fe2(SO4)3), Aluminium Chloride (AlCl3), Aluminium Sulfate (Al2(SO4)3), and Polymeric Aluminium Chloride (PAC) regarding their performance in conditioning sludge dewatering, physicochemical properties, the risk of heavy metals migration in sludge cake and the mechanism of sludge dewatering, was investigated. Within a dosage range of 20% dry solids (DS), the PFS and FeCl3 showed a better dewatering effect among the six coagulants, and the water content (Wc) of the sludge cake decreased from 81.2%±1.1% to 57.7%±1.0% and 59.2%±1.6%, respectively. There was a correlation between the pH, zeta potential, viscosity, and bound water content of the sludge and the Wc of the sludge cake during dewatering conditioned by six coagulants. However, there was no correlation between sludge particle size and Wc of the sludge cake. The PFS and FeCl3 reduced the protein content of tightly bound extracellular polymeric substances (TB-EPS) by 66.1% and 62.6%, respectively. Moreover, the iron coagulants significantly reduced the content of As, Cu, Ni, and Zn in the sludge cake, where the risk levels of As and Ni were largely weakened. The economic analysis shows that iron coagulants were more valuable than aluminium coagulants for engineering applications. Meanwhile, the dewatering mechanisms of the two types of coagulants were revealed. This study provides significant insights into the application of coagulants in engineering practice.

The practical meaning of the classical optimizing method and Angular Detection Photometer (ADP) in coagulation tests of surface water

Because of the growing deficit of clean water, rational use of its supplies through adaptation of purification techniques to the needs is becoming vital. The commonly used coagulation process requires optimization tools and techniques. The following were used in this paper to optimize coagulation of natural water pollutants: the standard jar test method with direct filtration and the angular detection photometry (ADP) method. We tested two aluminium coagulants – PAC with different basicity – and an iron coagulant: PFS. A modified jar test method allowed to obtain results similar to those of the sedimentation method. At the optimum doses 1.3 mg Al/mg C org. and 2 mg Fe/mg Corg – colour (PtCo), A254, A436 – achieved reduction in the 84–96% range and DOC 60–67% after filtration. The titration method using an ADP successfully allows determine optimum coagulant doses. The SD and FI values were determined based on the recorded fluctuations of the signals measured by detectors placed at three angles relative to the IR beam. A variation in SD was observed, depending on the angle of detection and the coagulant and correlates well (R2 =0.6–0.86) with sedimentation time ST, which was twice as long in the case of fine suspension in the PFS.

Unraveling the characteristics of dissolved organic matter removed by aluminum species based on FT-ICR MS analysis

Given the complexity of dissolved organic matter (DOM) and its interactions with coagulant chemicals, the mechanisms of DOM removal by aluminum (Al) coagulants remains a significant unknown. In this study, six test waters containing DOM with molecular weight (MW, <1 kDa, 1–10 kDa and >10 kDa) and hydrophobicity (hydrophilic, transphilic and hydrophobic) were prepared and coagulated with Al0, Al13 and Al30. The molecular-level characteristics of DOM molecules that were removed or resistant to removal by Al species were analyzed using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that at the molecular level, saturated and reduced tannins and lignin-like compounds containing abundant carboxyl groups exhibited higher coagulation efficiency. Unsaturated and oxidized lipids, protein-like, and carbohydrates compounds were relatively resistant to Al coagulation due to their higher polarity and lower content of carboxyl groups. Al13 removed molecules across a wider range of molecular weights than Al0 and Al30, thus the DOC removal efficiency of Al13 was the highest. This study furthers the understanding of interactions between Al species and DOM, and provides scientific insights on the operation of water treatment plants to improve control of DOM.

Comparison of aluminum formate and traditional aluminum coagulants in structure, hydrolysates, coagulation behavior, and its corrosion resistance advantage

Aluminum formate (AF) has been considered as a superior coagulant that can decompose under the UV light without causing equipment corrosion during water treatment. The main components of the aluminum formate coagulant are aluminum formate (C3H3AlO6), aluminum formate hydrate (C3H3AlO6·3H2O), and aluminum hydrogen formate (C3H3AlO6·2H2O2). Analysis of the hydrolyzed products revealed that the content of added formic acid during the synthesis of aluminum formate is a crucial factor influencing its coagulation effectiveness. Increasing the HCOOH/Al ratio from 1.5 to 4.0 resulted in smaller mass-to-charge ratio (m/z) and higher positive charge for AF hydrolysates, with fewer undetected aluminum species present. Hydrolysates of AF 1.5 exhibited similar characteristics to those of aluminum polychloride, while AF 3.0 demonstrated optimal glucan removal efficiency (>55 %) through physical absorption rather than chemical bond bridging as the primary coagulation mechanism. The jar test results for bovine serum albumin (BSA) coagulation removal indicated a decrease in removal efficiency as the HCOOH/Al molar ratio increased from 1.5 to 4.0, accompanied by a decrease in pH conditions from 6.35 to 7.27. The highest BSA removal efficiency (58 %) was achieved using AF 1.5 at pH 6.35, suggesting that BSA molecules were captured by aluminum formate through chemical bonds such as NO-Al-, Al2(SO4)3, unlike the physical absorption effect observed in glucan coagulation process. Furthermore, it should be noted that compared to traditional aluminum salt coagulants, aluminum formate exhibits excellent pipeline corrosion resistance properties.

Low waste technology for mine waters treatment using lime and aluminum coagulants

In this paper the process of reagent desalination of mineralized mine waters was studied. The peculiarity of mine waters in many regions of Ukraine is that, along with hardness ions, they also contain sulphates in fairly high concentrations. Therefore, the task of desalination of mineralized waters consists in effective removal of sulphates along with softening of the solution. For effective purification of water from sulphates and hardness ions, 5/6 aluminum hydroxychloride (Al2(OH)5Cl) and sodium tetrahydroxoaluminate (Na[Al(OH)4]) were used during liming. A significant increase in efficiency of the treatment process was achieved when the solution was acidified with carbon dioxide after treatment with reagents. The directions of processing of the formed sediments as part of building materials have been determined. Complex processing of the generated waste in the process of water treatment allows creating a low-waste technology for the purification of mineralized water.

Revelation of the interaction between aluminum coagulants and natural organic matters in the dual-system during nanofiltration membrane scaling

Aluminum (Al) coagulants are widely and frequently applied to coagulation pretreatment before nanofiltration. However, the excess coagulants and residual natural organic matters (NOMs) might affect the gypsum scaling during nanofiltration process. This study investigated the nanofiltration membrane fouling process under Al coagulants and specific NOMs, including humic acids (HA), bovine serum protein (BSA), and sodium alginate (SA) in a dual-system. The flux and the particle size decreased significantly when both above were present. The gypsum crystallization on the membrane surface was enhanced, while the bulk crystallization was weakened. Zeta potential and the NICA-Donnan model showed that Al coagulants competed with Ca2+ to bind HA weakening the bulk crystallization of gypsum. Meanwhile, Al coagulants decreased the salt rejection rate. Interestingly, the BSA and SA alleviated the flux decrease. Furthermore, the characterization of the fouled membrane showed that the concentration of Ca2+ and SO42− on the membrane surface increased further in the presence of Al coagulants, the grain size reached 582.0 nm when both HA and Al were present, larger than the control group and when they were present in the feed solution alone. Finally, the modified Hermia model was introduced to analyze the mechanism of the interaction between Al coagulants and NOMs. It is suggested that the control of Al coagulants and HA is necessary for the coagulation pretreatment before nanofiltration.

A system dynamics approach for large-scale water treatment plant sludge management: A case study in Brazil

A simulation model for water treatment plant sludge management was proposed, based on the system dynamics approach. This model can be extended to the sludge management of a sanitation system (WTP + WWTP). The model is useful for the selection of the best destination for the sludge generated in treatment plants based on the various changes that a decision can have throughout the operation of the sanitation system. The applicability of the proposed model was tested in a case study of WTPs 3 and 4 and the Anhumas Wastewater Treatment Plant located in Campinas, the main city of the Piracicaba, Capivari and Jundiaí river basin, an important area of water resource management in Brazil. The developed model can be used by treatment plants to: select the best final destination option according to treatment technologies; select the best location for final disposal, considering transport, disposal and storage costs; verify the influence on treatment costs to adapt to a pre-defined final destination for joint management; or compare beneficial disposal costs with landfill disposal costs. The model was developed to allow for gradual increase in acceptance of the residue over time. By establishing this variable, slightly lower final costs were observed in the scenario of sending the sludge with aluminum coagulant to ceramic industries, compared to sending it to landfill, in the case study used for model development. Despite the interesting results, these values should be considered only indicative. Therefore, it can be stated that the major challenge to using the SD model is the accurate and appropriate data collection for correct simulation, as well as its historical series, for accurate evaluation of the viability of the model. The proposed simulation methods showed greater sensitivity to treatment costs, highlighting the importance of beneficial use of the proposed sludge to the technologies employed for water and sludge treatment.

Complex Agent for Phosphate Sequestration from Digested Sludge Liquor: Performances and Economic Cost Analysis

Phosphorus (P) management in the “water-energy-resource-nexus” in wastewater treatment plants (WWTPs) remains a longstanding challenge. P adsorption from the P-enriched digested sludge liquor (DSL) is a comparatively more practical and economically viable approach for P recovery in WWTPs. However, high concentrations of impurities in DSL might pose a negative and interferential effect on P adsorption, hindering the application of sorbents or precipitation methods. Given such a situation, highly efficient and cost-effective sorbent towards P reclamation from DSL is highly needed. Therefore, this study aims to develop a novel complex agent containing aluminum coagulant and superparamagnetic nano-sorbent (SNS) that can be used in magnetic seeding coagulation for P recovery. The complex agents with different PACl: SNS ratios showed varied turbidity removal rates and P recovery efficiencies and the optimal ratio was 15 mg PACl: 15 g SNS. PAC and SNS showed significant interaction because PAC could enhance P adsorption by shielding the interferential effect of colloidal impurities. In addition, the complex is highly regenerative, with turbidity and P removal rate stably maintained at 70–80% after 10 adsorption/regeneration cycles. The cost–benefit analysis of the dosing complex agent showed a dosing cost of 0.154 EUR/m3, admittedly much higher than the conventional magnetic seeding coagulation, which could probably be covered by the profit if the expensive and rare P product is reclaimed. This work indicated that the complex agent was superior due to its high adsorption capacity, easy separation, and repeated dosing, and therefore had the potential for P recovery from DSL.

Efficiency of water purification from oil with aluminum coagulants

In this work, the processes of reagent purification of aqueous emulsions from oil using aluminum coagulants, such as: aluminum sulfate, aluminum hydroxide, and aluminum hydroxochloride, were investigated. In emulsion cleaning processes, coagulants were used separately, as well as in the presence of sorbents: bentonite or activated carbon.&#x0D; The results of the conducted studies demonstrate that aluminum sulfate, aluminum hydroxide, and aluminum hydroxochloride in doses of 2–50 mg/dm3 provide a high degree of oil extraction from emulsions. The degree of water purification reaches 97–99 %.&#x0D; It was established that the efficiency of oil extraction from water with the help of aluminum coagulants depends significantly on the chemical composition of the coagulant and the original mineralization of the water. Aluminum hydroxide has the greatest efficiency in removing oil from water, which ensures the maximum reduction of oil concentration in both fresh and mineralized water.&#x0D; The combined use of aluminum coagulants and sorbents such as bentonite and activated carbon is characterized by fluctuating efficiency, which depends on the type of coagulant and sorbent, their concentrations, and the mineralization of the source water.&#x0D; To a large extent, the ambiguity of the presented results can be explained by the heterogeneity of the emulsions. However, it can be unequivocally stated that the use of aluminum coagulants in the processes of removing oil from water of different mineralization is expedient and effective.

A model for predicting reduction in mobile phosphorus of lake sediment by aluminum drinking water treatment residuals

Drinking water treatment residual (DWTR) derived from flocculation and sedimentation of raw water using aluminum coagulants is a valuable environmental remediation byproduct capable of inactivating phosphorus (P). However, no generalizable model exists in the literature to describe reduction of releasable (mobile) P in lake sediment as a result of DWTR addition. The reduction of mobile P (sum of labile P and reductant soluble P) was investigated in over 100 sub-samples using five sediment samples from two lakes and three DWTRs from different water treatment plants. A consistent relationship was determined across a range of mobile P contents (0.23 g/m2/cm to 0.92 g/m2/cm, or 15.8 to 186.1 µg/g DW) and DWTRs. The relationship was best described as a function of the mobile P content of the sediment and the oxalate-extractable aluminum content of the DWTR. An empirical model was developed to predict the immediate reduction in mobile P following the addition of DWTR containing aluminum. This model was validated using two additional lake sediments and one additional DWTR (R² = 0.995). Thus, the immediate inactivation of P in lake sediment following DWTR addition can be predicted with this model, which can be used with internal P loading or other water quality goals to determine an appropriate DWTR dose. Further recommendations were made about dosing DWTRs for lake restoration, allowing practitioners to use DWTR to inactivate P in lake sediment without conducting individual sorption experiments.

Solid–Liquid Separation of Dairy Barn by Electrocoagulation with Cationic Polymer Coagulant

High–molecular-weight polymer coagulants are widely used in wastewater treatment combined with traditional inorganic coagulants to improve the solid–liquid separation efficiency. However, it is desirable to keep chemicals used in treatments at minimum levels for economic and safety reasons. This study aimed to increase the efficiency of two-stage electro- and chemical-coagulation treatment with a minimum chemical dosage for the separation of solids and liquid in dairy manure slurry for the safe composting of solids and safe discharge of wastewater. Accordingly, dairy manure slurry was treated with aluminum (Al) coagulants, such as polyaluminum chloride (PAC), aluminum chloride (AlCl3), and aluminum sulfate (Al2(SO4)3), PAC combined with the cationic polyacrylamide (CPAM), and PAC and CPAM combined with electrocoagulation (EC). Results revealed that PAC was the best among the Al coagulants evaluated for the reduction in turbidity in the liquid fraction at a dosage of 100 mg/L. PAC dosage was reduced to 40 mg/L when the treatments were combined with CPAM at a dosage of 40 mg/L, which was further reduced to 30 mg/L when treatments were combined with 5 min EC and 20 mg/L of CPAM dosage.

Characteristics and mechanisms of As(III) removal by potassium ferrate coupled with Al-based coagulants: Analysis of aluminum speciation distribution and transformation

This study was carried out to investigate the enhanced removal of arsenite (As(III)) by potassium ferrate (K2FeO4) coupled with three Al-based coagulants, which focused innovatively on the distribution and transformation of hydrolyzed aluminum species as well as the mechanism of K2FeO4 interacted with different aluminum hydrolyzed polymers during As(III) removal. Results demonstrated that As(III) removal efficiency could be substantially elevated by K2FeO4 coupled with three Al-based coagulants treatment and the optimum As(III) removal effect was occurred at pH 6 with more than 97%. K2FeO4 showed a great effect on the distribution and transformation of aluminum hydrolyzed polymers and then coupled with a variety of aluminum species produced by the hydrolysis of aluminum coagulants for arsenic removal. During enhanced coagulation, arsenic removal by AlCl3 was main through the charge neutralization of in situ Al13 and the sweep flocculation of Al(OH)3, while PACl1 mainly depended on the charge neutralization of preformed Al13 and the bridging adsorption of Al13 aggregates, whereas PACl2 mainly relied on the sweep flocculation of Al(OH)3. This study provided a new insight into the distribution and transformation of aluminum species for the mechanism of As(III) removal by K2FeO4 coupled with different Al-based coagulants.

The removal efficiency and reaction mechanism of the aluminum coagulant on phenolic compounds in the presence of hardness salts

This study is the evaluation of the coagulation efficiency of the aluminum sulfate on the removal of catechol and pyrogallol. The study has focused on the impact of inorganic components of hardness Algerian waters. Jar-test trials were conducted on the two phenolic compounds dissolved in distilled water only, which was later enriched with minerals. Several reaction parameters varied, including the effect of pH and the influence of the salt content, and this approach yielded a better understanding of interaction between phenolic compounds and calcium/magnesium salts. The results indicate that the process efficiency depends on the number and position of OH in molecules. The main mechanisms would be either a physical adsorption, an exchange of ligand, or complexation on the floc surface of aluminum hydroxide. Moreover, the addition of inorganic salts appears to improve removal efficiency of tested phenolic compounds and have an effect on the optimal pH range for coagulation.

Compounds to mitigate cyanobacterial blooms affect growth and toxicity of Microcystis aeruginosa

Numerous products and techniques are used to combat harmful cyanobacterial blooms in lakes. In this study, we tested nine products, the phosphate binders Phoslock® and Aqual-PTM, the coagulant chitosan, the phosphorus binder and coagulant aluminum salts (aluminum sulphate and sodium aluminate), the copper-based algicides SeClear, Captain® XTR and CuSO4·5H2O, the antibiotic Streptomycin and the oxidant hydrogen peroxide (H2O2) on their efficiency to manage the cyanobacterium Microcystis aeruginosa (M. aeruginosa). To this end, 7 days of laboratory experiments were conducted and effects were determined on chlorophyll-a, photosystem II efficiency (PSII), soluble reactive phosphorus (SRP) and intracellular and extracellular microcystin (MC) concentrations. The algicides, chitosan and H2O2 were the most powerful in reducing cyanobacteria biomass. Biomass reductions compared to the controls yielded: Chitosan (99.8%) > Hydrogen peroxide (99.6%) > Captain XTR (98.2%) > SeClear (98.1%) > CuSO4·5H2O (97.8%) > Streptomycin (86.6%) > Phoslock® (42.6%) > Aqual-PTM (28.4%) > alum (5.5%). Compounds that caused the largest reductions in biomass also strongly lowered photosystem II efficiency, while the other compounds (Phoslock®, Aqual-PTM, aluminum salts) had no effect on PSII, but strongly reduced SRP. Intracellular MC concentration followed the biomass patterns, extracellular MC was generally lower at higher doses of algicides, chitosan and H2O2 after one week. Recovery of PSII was observed in most algicides and chitosan, but not at the highest doses of SeClear and in all streptomycin treatments. Our results revealed that M. aeruginosa can be killed rapidly using several compounds, that in some treatments already signs of recovery occurred within one week. P fixatives are efficient in reducing SRP, and thus acting via resource suppression, which potentially may provide an addition to fast-acting algicides that kill most of the cells, but allow rapid regrowth as sufficient nutrients remain.

Improvement of permeation flux by evaluating the effects of coagulated-humic acids flocs and pH during coagulation-microfiltration hybrid process for water treatment: Performance, fouling modeling, specific energy consumption, and processes comparison

The objective of this study is to analyze the relation between flocs shape and the permeation flux stability in a pilot-scale Coagulation/Flocculation-Microfiltration hybrid process for humic acids removal from water under different coagulant dose and pH values. Besides, the treatment performance was examined. The results showed that at pH 7.1 and polychloride of aluminum coagulant of 10−1 mmol Al.L−1, coagulation/flocculation was effective in maintaining membrane permeability flux. Also, UV254, TOC, and turbidity removal efficiencies were almost ≥ 90%. In addition, this condition proved a potent effect on residual aluminum control and specific energy consumption, where they were, respectively, 0.0852 kWh.m−3 and 20 µg.L−1. Furthermore, humic acids fouling using four Hermia mechanisms (individual and combined) was modeled. Complete pores blocking and cake filtration appeared to be the major mechanisms of microfiltration membrane fouling. Finally, this hybrid process was compared with the most used technologies for the humic acids removal from water. It was concluded that the former process is more reliable, efficient, and cost-effective.