Experimental and artificial intelligence optimization of paint wastewater (PWW) coagulation using novel Phaseolus vulgaris seed extract (PVSE).

This study investigated the application of artificial intelligence algorithms (AIA) in the coagulation treatment of paint wastewater anchored by novel Phaseolus vulgaris seed extract (PVSE). Untreated wastewater discharge harms the ecosystem, and therefore harmful industrial effluent, such as paint wastewater, must be brought to safe discharge levels before being released into the environment. In addition to AIA, comprehensive characterization tests, coagulation kinetics, and process optimization were also executed. Characterization results revealed that total solid in the PWW was above allowable standard, justifying the need for effective particle decontamination. The XRD and FTIR characterization indicated that PVSE structure is amorphous with abundant amine groups. Results of analysis of variance (ANOVA) obtained from process modeling indicated that the coagulation-flocculation process was a nonlinear quadratic system (F-value = 45.51) which was mostly influenced by PVSE coagulant dosage (F-value = 222.48; standardized effect = 14.85). Artificial intelligence indicated that neural network training effectively captured the nonlinear nature of the system in ANN (RMSE = 0.00040194; R = 0.98497), and ANFIS (RMSE = 0.003961) algorithms. Regression coefficient obtained from process modeling highlighted the suitability of RSM (0.9662), ANN (0.9739), and ANFIS (0.9718) in forecasting the coagulation-flocculation process, while comparative statistical appraisal authenticated the superiority of ANN model over RSM and ANFIS models. The coagulation kinetics experiment, which used a coagulation kinetic model, revealed a constant flocculation constant (Kf-value) for all jar test batches and a strong association between the Menkonu coagulation-flocculation constant (Km) and Kf values. Best removal efficiency of 97.01 % was obtained using ANN coupled genetic algorithm optimization (ANN-GA) at PVSE dosage of 4 g/L, coagulation time of 29 min and temperature of 25.1oC.

Influence of chitosan properties and operating parameters on the flocculation efficiency and harvesting of microalgae (Scenedesmus sp.).

Physicochemical and structural characteristics of chitosan prepared from Deep-sea shrimp (DCs), including degree of deacetylation (DD), molecular weight (Mw), viscosity, crystallinity index (CrI) and surface morphology were compared with a commercial chitosan (CCs). The DCs had a higher DD of 81.33 ± 0.40 %, whereas the CCs had a lower DD of 74.62 ± 0.64 %. Additionally, the DCs exhibited a lower Mw of 192.47 ± 2.5 kDa and viscosity of 646.00 ± 4.00 cP compared to the CCs, which had a Mw of 202.44 ± 0.28 kDa and viscosity of 689.67 ± 5.91 cP. This study investigated the influence of chitosan properties, particularly DD and Mw on the harvesting of Scenedesmus sp. along with the chitosan dosage, pH of the culture medium, mixing speed and time. Under optimal operating conditions, the microalgae removal efficiency of the DCs reached a significantly higher level (94.71 ± 0.20 %) compared to that of CCs (88.25 ± 0.41 %). Chitosan with a higher DD and low Mw demonstrated superior flocculation efficiency. The results highlight the significance of DD and Mw of chitosan and its influence on the flocculation of microalgae, providing valuable insights for optimizing the harvesting process with the non-toxic and natural flocculent, chitosan.

Optimization use of watermelon rind in the coagulation-flocculation process by Box Behnken design for copper, zinc, and turbidity removal.

Watermelon rinds were investigated as a bio-coagulant for treating water contaminated by metals and turbidity, owing to their biodegradability and greater environmental friendliness compared to chemical coagulants. Fourier transform infrared spectroscopy, scanning electron microscopy paired with energy dispersive X-ray analysis and X-ray diffraction characterized the watermelon rinds before and after use. A Box-Behnken experimental design optimized the most influential parameters of initial pH, coagulant dose, and particle size based on response surface methodology. This analysis revealed the experimental data fit quadratic polynomial models, achieving maximum removal efficiencies of 97.51 % for zinc, 99.88 % for copper, and 99.21 % for turbidity under optimal conditions. Statistical analysis confirmed the models effectively captured the experimental data. Analysis of variance denoted the high significance of the quadratic effects of dose and pH. Removal of metal ions Zn2+ and Cu2+ was significantly impacted by these factors. The watermelon rind powder retained its coagulation efficiency after five cycles of reuse, with removal rates of 80.04 % for Zn, 88.33 % for Cu and 86.24 % for turbidity. These results demonstrate the potential of watermelon rind as an alternative coagulant for wastewater treatment. Further testing on real industrial effluents at larger scales would help assess their feasibility for real-world applications.

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 5800 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.

Development and techno-economic analysis of Grewia biopolymer-based dual coagulant system for wastewater treatment at pilot scale.

Use of Grewia biopolymer as a natural coagulant aid was explored in a dual-coagulant system (conventional coagulant + biopolymer) for wastewater treatment. Such use not only improved turbidity removal efficiency over a wide pH range (5-9) but also helped reducing the concentration demand of inorganic coagulants by 25-50 %. Response surface methodology was employed for investigating the interaction between factors (initial pH, coagulant, and biopolymer concentration) affecting coagulation/flocculation of aqueous laterite suspension, and process optimization for more than 80 % turbidity removal in the desired final pH range (6-7). Mechanisms potentially involved in coagulation/flocculation using biopolymer was elucidated. Techno-economic assessment indicated the feasibility of pilot-scale production of the biopolymer and its use in wastewater treatment. This study demonstrates that Grewia biopolymer has the potential to be used as a coagulant aid and will help researchers select appropriate markets for further cost reduction and successful implementation of biopolymer-based wastewater treatment.

Evaluating the effectiveness of coagulation-flocculation treatment on a wastewater from the moroccan leather tanning industry : An ecological approach.

The removal of pollutants from tannery wastewaters, which is renowned for its substantial volumes, intricate composition, and considerable hazards to human health and the environment, is a prominent research area in the field of water treatment. The aim of this study is to employ a bio-coagulant derived from Parkinsonia aculeata seeds and a bio-flocculant derived from Hibiscus esculentus to minimise the concentration of pollutants in the combined wastewater originating from tanneries. In the course of the research, a thorough physicochemical analysis of the coagulating and flocculating agents, Parkinsonia aculeata (PA) and Hibiscus esculentus (HE), was performed using techniques such as XRD (X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), and SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy). This analysis aimed to determine the composition and characteristics of these biomasses. Subsequently, a comprehensive overview was conducted to summarize the various factors that influence the treatment of tannery wastewater through coagulation/flocculation. This was accomplished by manipulating the target factors and observing their impact on the removal of specific physicochemical parameters such as chemical oxygen demand (COD), electrical conductivity (EC), total chromium (Cr) and Optical density (OD). The variables that were established include pH, dosage of coagulant and flocculant, as well as the speed and duration of agitation in both the fast and slow mixing stages. The experiments were carried out while taking into account the optimal parameters, leading to the near-complete removal of all analyzed pollutants. The optimal requirements for the Parkinsonia aculeata-Hibiscus esculentus Coagulation Flocculation System involve adjusting the pH to 8, choosing concentrations of approximately 1.25 g L-1 and 0.6 g L-1 for the coagulant and flocculant respectively, maintaining a fast speed of 170 rpm for 3 min while keeping the slow agitation at around 30 rpm for 20 min. The removal rates achieved after treating tannery wastewater using the PA-HE coagulant-flocculant combination demonstrate high efficacy, with values reaching approximately 100% for TSS, 98.71% for BOD5, 99.93% for COD, 98.88% for NH4+, 98.21% for NO3-, 90.32% for NO2-, 93.13% for SO42-, 95.44% for PO43-, 96.08% for OD and 60% for total chromium. These results indicate the successful removal of a wide range of pollutants from tannery wastewater through the PA-HE treatment method. In predicting the CF treatment approach, PCA has been employed to preprocess the input data and determine the key variables that impact the process. This can streamline the modeling process and enhance the precision of the predictions.

Effect of FeCl3 concentration in chemically enhanced primary treatment on the performance of a conventional wastewater treatment plant. A case study.

The effect of coagulant dosage in a chemically enhanced primary treatment (CEPT) on the performance of a conventional wastewater treatment plant (WWTP) has been investigated. Lab-scale experiments simulations were carried out in order to evaluate the effect of coagulant addition on the primary settling performance. In these experiments, FeCl3 was used as coagulant. Later, the WWTP was theoretically simulated using a commercial software (WEST®) to evaluate the effect of coagulation/flocculation on the global system, based on the results obtained at lab-scale. According to these results, the CEPT modifies the organic matter balance in the WWTP, decreasing the contribution of readily (SS) and slowly (XS) biodegradable fractions of COD to the aerobic biological process up to 27.3% and 80.8%, respectively, for a dosage of FeCl3 of 24 mg L-1. Consequently, total suspended solids in the aerobic reactor and the secondary purged sludge decreased up to 33% and 13%, respectively. However, the influence on effluent quality was negligible. On the contrary, suspended solids concentration in the sludge to be treated by anaerobic digestion increased, mainly regarding the Ss and Xs fractions, which caused an 8.1% increase in biogas production potential, with approximately 60% of CH4 concentration.

Wilderness Medical Society Clinical Practice Guidelines on Water Treatment for Wilderness, International Travel, and Austere Situations: 2024 Update.

To provide guidance to medical providers, wilderness users, and travelers, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for treating water in situations where the potability of available water is not assured, including wilderness and international travel, areas impacted by disaster, and other areas without adequate sanitation. The guidelines present the available methods for reducing or eliminating microbiological contamination of water for individuals, groups, or households; evaluation of their effectiveness; and practical considerations. The evidence base includes both laboratory and clinical publications. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according to the criteria published by the American College of Chest Physicians.

Green industry work: production of FeCl3 from iron and steel industry waste (mill scale) and its use in wastewater treatment.

Mill scale (MS) is considered to be a significant metallurgical waste, but there is no economical method yet to utilize its metal content. In this study, which covers various processes in several stages, the solution of iron in MS, which is the Iron and Steel Industry (I&SI) waste, as FeCl3 (MS-FeCl3) in the thermoreactor in the presence of HCl, was investigated. In the next step, the conditions for using this solution as a coagulant in the treatment of I&SI wastewater were investigated using the jar test. The results of the treated water sample were compared by chemical oxygen demand (COD), total suspended solids (TSS), color, and turbidity analyses using commercial aluminum sulfate (Al2(SO4)3) and FeCl3 (C-FeCl3). Additionally, heavy metal analyses were conducted, and the treatment performance of three coagulants was presented. Accordingly, while 2.0 mg/L anionic polyelectrolyte was consumed at a dosage of 4.05 mg/L Al2(SO4)3 at pH 7.0, 0.25 mg/L anionic polyelectrolyte was consumed at a dosage of 1.29 mg/L at pH 5.0 in the C-FeCl3 and MS-FeCl3 studies. Also, Fe, Cr, Mn, Ni, Zn, Cd, Hg, and Pb removal efficiencies were over 93.56% for all three coagulant usage cases. The results showed that the wastewater treatment performance of MS-FeCl3 by the recycling of MS, which is an I&SI waste, was at the same level as C-FeCl3. Thus, thanks to recycling, waste scale can be used as an alternative to commercial products for green production.

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.

A closed-loop process for spent washing solution from multi-metal contaminated soil: EDTA reclamation and recycling.

The proper disposal of spent soil washing solution is a great challenge to ethylenediamine tetraacetate (EDTA)-base soil washing technologies, particularly when the solution contains multi-metals. In this paper, we proposed an environmentally friendly disposal of multi-metal spent washing solution, in which the multi-metals were concentrated as hazardous precipitates for further safe disposal, and EDTA was reclaimed and recycled to further wash contaminated soil together with the cleansed process water. The results showed that Cr3+ was poorly removed by sole heavy-metal-capturing agent (HMCA) chelation because of the high solubility of HMCA-Cr, which also yielded a low percentage of EDTA reclamation in the multi-metal spent washing solution. We established a closed-loop process for the disposal of multi-metal spent washing solution by combining coagulation-flocculation-sedimentation and HMCA chelation. The novel recycling process was able to remove 99.67% Cu, 99.62% Pb, 92.48% Cd, 88.19% Sb, 84.38% As, and 82.39% Cr as precipitates from the real spent washing solution, and up to 95.64% of EDTA was reclaimed in the cleansed process water. On the average, the overall efficiency of the reclaimed EDTA solution could reach 65% of the fresh EDTA solution in extracting various HMs from contaminated soil. The recycling method provides an efficient and promising alternative for spent soil washing solution with both EDTA and process water reusage in a closed-loop process.

Treatment of effluents from Food Services Establishment (FSEs) by physico-chemical processes: a case study for Trinidad & Tobago.

BACKGROUND: Effluents from Food Services Establishments (FSEs) contain primarily Fats, Oil and Grease (FOG) which severely impact on sewers and the environment when released in high concentrations. In Trinidad & Tobago, it is estimated that approximately 231,304 kg/day of unaccounted for FOG bearing wastewaters from FSEs, are released into the environment with no viable treatment in the country. This research explored the optimization of physico-chemical processes for the treatment of FOGs for subsequent release into sewers. RESULTS: Bench-scale studies analysed the characteristics of FSE's effluents from three popular sources, conducted the treatment of these effluents using Jar Tests, and subsequently confirm results via a pilot plant study. Characterization showed the mean concentration of the parameters examined to be; FOG (511 mg/l ± 116 mg/l), Suspended Solids (446 mg/l ± 146 mg/l), Chemical Oxygen Demand (2229 mg/l ± 963 mg/l) and pH (6 ± 0.3). Jar Tests were conducted using Poly-aluminium Chloride (PACl) as coagulant, anionic and cationic polyelectrolytes as flocculant aids with suitable pH adjustments of samples to determine the isoelectric point for the coagulant. Effluent results showed FOG removal levels of 99.9% and final effluent concentration of 0.17 mg/l. This was attained using PACl concentration of 250 mg/l, a 0.1% low cationic polyelectrolyte (CP 1154) at 4 mg/l with the pH of sample adjusted to 8. The pilot plant achieved a 97.4% removal of FOG (residual of 16.8 mg/l) using the same coagulant dosing, and pH value, but increasing the strength of the flocculant aid to 0.1% medium cationic (CP1156) at 5 mg/l. CONCLUSION: Experimentation showed high concentrations of emulsified FOG can be efficiently removed to levels below the permissible requirements (20 mg/l) for entry into sewer systems in Trinidad and Tobago using coagulation, flocculation and sedimentation techniques. Pilot scale study also revealed that a higher strength and/or dose of the cationic polyelectrolyte and increased times in primary and final tanks were required to attain the desired results as in the bench level study, where equipment limitations in the flocculation tank were faced. This is in alignment with theory where factors critical for agglomeration is equipment type and density charge. It is, concluded that the optimum combination of chemicals and the respective dosages attained at the bench level study should prove effective should the right equipment be made available.

Phytotoxicity assessment of treated vegetable oily wastewater via environmentally coagulation/flocculation and membrane filtration technologies using lettuce (Lactuca sativa) seeds.

The present investigation highlights the necessity of monitoring some basic physico-chemical water quality indicators and their phytotoxic effect using ecotoxicological bioassays such as "seed germination tests." The phytotoxicity of raw and treated vegetable oil refinery wastewater (VORW) using different treatment processes was assessed through some physiological responses (relative seed germination (RSG), seedling elongation, and germination index (GI)) using Lactuca sativa cultivar. Biotest results of different raw water samples revealed a noticeable correlation between the organic matter content and water phytotoxicity. In fact, VORW showed a very low RSG (17 ± 0.7 to -47 ± 0.58%) and high phytotoxic effects (GI < 50%). The use of coagulation/flocculation (CF) allowed a satisfactory phytotoxicity removal where RSG obtained ranged from 83 ± 1.58 to 90 ± 1.2%. However, the effluent still presents high to moderate phytotoxicity since GI remained below 80% which indicates the presence of toxic elements remaining after CF treatment. When VORW were treated using membrane processes, their phytotoxicity was gradually decreased with the decrease in the membrane pore size. The use of microfiltration membranes (MF), with pore size of 5 µm, 1.2 µm, 0.45 µm, and 0.22 µm, showed RSG values ranged from 37 ± 1.15 to 77 ± 1.68% and GI of less than 80% indicating a moderate to high phytotoxicity. However, the use of ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) of 100 kDa, 30 kDa, and 10 kDa made it possible to achieve an RSG of 100% and an IG exceeding 80% showing that the VORW-treated using UF does not exhibit any phytotoxicity effect. Hence, UF appears to be the most efficient and environmentally friendly technology that could be used for safely treated VORW irrigation purposes compared to CF and MF processes.

Cheese wastewater treatment through combined coagulation-flocculation and photo-Fenton-like advanced oxidation processes for reuse in irrigation: effect of operational parameters and phytotoxicity assessment.

The present study aims to investigate the efficiency of a combined cheese wastewater treatment approach involving coagulation with ferric chloride coupled with a photo-Fenton-like oxidation process for potential reuse in irrigation. Laboratory-scale tests were conducted, examining the effect of various operational parameters on the treatment process. Specifically, the effects of initial wastewater pH, coagulant dosage, decantation time for the coagulation process, and initial pH, chemical oxygen demand (COD) concentration, and Fe3+ and H2O2 dosages for photo-Fenton-like oxidation were studied. Coagulation was found effective at natural pH of 6 and showed a highest removal efficiency in terms of COD (50.6%), biological oxygen demand BOD5 (42.1%), turbidity (99.3%), and least sludge volume generation (11.8% v/v) for an optimum coagulant dose of 400 mg Fe3+ L-1 and 8 h of decantation time. Thereafter, photo-Fenton-like oxidation (Fe3+/H2O2/UVA-300W) of the pretreated cheese effluent enhanced the removal of COD, BOD5 and TOC to 91.2%, 91.4%, and 97.5%, respectively, using the optimized conditions (pH = 3; [Fe3+] = 5.0 × 10-4 mol L-1; [H2O2] = 0.2 mol L-1 and tirr = 24 h). This study also shows that the proposed combined process allowed a significant phytotoxicity reduction toward lentil seed germination. The obtained outcome was encouraging and supports the possible use of the treated cheese wastewater as an additional water source for agricultural irrigation.

Per- and polyfluoroalkyl substance (PFAS) removal from soil washing water by coagulation and flocculation.

Soil washing is currently attracting attention as a promising remediation strategy for land contaminated with per- and polyfluoroalkyl substances (PFAS). In the soil washing process, the contaminant is transferred from the soil into the liquid phase, producing a PFAS contaminated process water. One way to treat such process water is to use coagulation and flocculation; however, few studies are available on the performance of coagulation and flocculation for removing PFAS from such process water. This study evaluated 6 coagulants and flocculants (polyaluminium chloride (PACl), zirconium oxychloride octahydrate, cationic and anionic polyacrylamide, Polyclay 685 and Perfluor Ad®), for the treatment of a proxy PFAS contaminated washing water, spiked with PFAS concentrations found at typical Aqueous Film Forming Foam (AFFF) contaminated sites. PFAS removal efficiencies (at constant pH) varied greatly depending on the coagulants and flocculants, as well as the dosage used and the targeted PFAS. All tested coagulants and flocculants reduced the turbidity by >95%, depending on the dosage. Perfluor Ad®, a specially designed coagulant, showed the highest removal efficiency for all longer chain (>99%) and shorter chain PFAS (>68%). The cationic polyacrylamide polymer removed longer chain PFAS up to an average of 80%, whereas average shorter chain PFAS removal was lower (<30%). The two metal-based coagulants tested, PACl and zirconium, removed longer chain PFAS by up to an average of 61% and shorter chain PFAS up to 48%. Polyclay 685, a mixture of powdered activated carbon (PAC) and aluminium sulphate, removed longer chain PFAS by 90% and shorter chain PFAS on average by 76%, when very high dosages of the coagulant were used (2,000 mg/L). PFAS removal efficiencies correlated with chain length and headgroup. Shorter chain PFAS removal was dependent on electrostatic interaction with the precipitating flocs, whereas for longer chain PFAS, hydrophobic interactions between apolar functional groups and flocs created by the coagulant/flocculant, dissolved organic matter and suspended solids played a major role. The results of this study showed that by selecting the most efficient coagulant and aqueous conditions, a greater amount of PFAS can be removed from process waters in soil washing facilities, and thus included as part of various treatment trains.

Potential of ash from agricultural waste as substitute of commercial FeCl3 in primary treatment of landfill leachate.

Due to the ever increasing global population, higher volumes of industrial waste discharges to landfill have caused major problems for the environment. This study investigated the performance of rice straw ash (RSA) as a natural coagulant under different conditions for the treatment of landfill leachates by coagulation-flocculation and microfiltration, with and without addition of FeCl3. The highest performing treatment conditions (RSA = 2.48 g/L, FeCl3 = 4.98 g/L, settling time = 54.75min) were achieved with the combined use of RSA and FeCl3 as coagulant and led to a sludge volume index of 41.65 mL/g, 51.27% COD removal and 76.48% total suspended solid removal. In contrast, FeCl3 alone achieved slightly better COD and total suspended solid removal rates, however it resulted in higher sludge volume index and sludge production. The combined use of RSA and FeCl3 reduced the consumption of these two coagulants by 78.76% and 46.69% respectively. Functional groups and thermal stability of the flocs showed that RSA + FeCl3 synergistically enhance the mechanisms of the coagulation-flocculation process, including adsorption by particle's bridging, charge neutralization and size of flocs. Combining the coagulants resulted in increased van der Waals forces and lower attractive forces of the inter-colloidal energy barrier in the leachate. Additionally, the highest and lowest heavy metals removal rates for treatment by microfiltration were found for Fe (92.15%) and Mg (7.63%), with a total heavy metals removal efficiency in the range of 6.08-90.78%. The findings of this study show that RSA can serve as a natural eco-friendly coagulant both alone and in combination with FeCl3 in the leachate treatment.

Coagulation pretreatment coupled with indigenous microalgal-bacterial consortium system for on-site treatment of rural black wastewater.

Improper treatment of rural black wastewater (RBW) presents substantial challenges, including the wastage of resource, environmental contamination, and economic consequences. This study proposed an integrated process for RBW treatment, consisting of coagulation/flocculation (C/F) pretreatment and subsequent inoculation of indigenous microalgal-bacterial consortium (IMBC) for nitrogen recovery, namely C/F-IMBC process. Specifically, the optimal C/F conditions (polyaluminium chloride of 4 g/l, polyacrylamide of 50 mg/l, and pH of 6) were determined through a series of single-factor experiments, considering CN, turbidity, and dissolved organic matter (DOM) removal, economic cost, and potential influence on the water environment. Compared to the sole IMBC system for RBW treatment, the proposed C/F-IMBC process exhibited a remarkable 1.23-fold increase in microalgal growth and a substantial 17.6-22.6 % boost in nitrogen recovery. The altered RBW characteristic induced by C/F pretreatment was supposed to be responsible for the improved system performance. In particular, the abundance of DOM was decreased and its composition was simplified after C/F pretreatment, based on the analysis for excitation-emission matrices with parallel factor and gas chromatography-mass spectrometry, thus eliminating the potential impacts of toxic DOM components (e.g., Bis(2-ethylhexyl) phthalate) on IMBC activity. It should also be noted that C/F pretreatment modified microbial community structure as well, thereby regulating the expression of nitrogen-related genes and enhancing the system nitrogen recovery capacity. For instance, the functional Cyanobacteria responsible for nutrient recovery was enriched by 1.95-fold and genes involved in the assimilatory nitrate reduction to ammonia pathway were increased by 1.52-fold. These fundamental findings are expected to offer insights into the improvement of DOM removal and nitrogen recovery for IMBC-based wastewater treatment system, and provide valuable guidance for the development of sustainable on-site RBW treatment technologies.

Evaluation of combined thermo-chemical processes for the treatment of landfill leachate using virgin and recovered FeCl3 coagulants.

Sludge resulting from treatment of municipal waste landfill leachate contains suitable cationic substances such as Fe-based recovered coagulants which, if not recovered, can cause environmental problems. The present study aimed to maximise coagulant recoverability and investigate its potential reuse for the treatment of municipal waste landfill leachate. The study focused on establishing (i) the effect of mineral acids on leaching of Fe, (ii) the % of maximum recovery of Fe coagulant, (iii) the impact of ultrasound on recovery, and (iv) effectiveness of recovered coagulant when reused in coagulation-flocculation treatment of landfill leachate. Sulfuric acid outran hydrochloric acid in performance, with the acid leaching process leading to the recovery of 70.12% of Fe (acid concentration = 3.80 M, solid-to-liquid ratio = 8%, and heating time = 5 h). Subsequently, a developed acid leaching process was tested, which results showed that the highest rate of Fe recovery occurred without ultrasound treatment, meaning the use of it could reduce the recovery rate due to the increase in the iron (III) oxide-hydroxide [Fe(OH)3] sedimentation. Comparative experiments were undertaken with the recovered and virgin coagulants. These revealed that Fe-based recovered coagulant led to the 60.21% and 91.40% removal of COD and total suspended solid respectively, while the values of the COD and total suspended solid removal with the virgin FeCl3 were 7.66% and 6.42% lower than that of Fe under optimal conditions (dosage = 9.38 g/L, pH = 8.94, settling time = 52.9 min). The present study established that Fe recovered could be exploited as an eco-friendly coagulant to replace FeCl3 in the landfill leachate treatment.

Novel thermodynamic mechanisms of co-conditioning with polymeric aluminum chloride and polyacrylamide for improved sludge dewatering: A paradigm shift in the field.

This study investigated the combined effects of polymeric aluminum chloride (PAC) and polyacrylamide (PAM) on sludge dewatering, aiming to unveil underlying mechanisms. Co-conditioning with 15 mg g-1 PAC and 1 mg g-1 PAM achieved optimal dewatering, reducing specific filtration resistance (SFR) of co-conditioned sludge to 4.38 × 1012 m-1kg-1, a mere 48.1% of raw sludge's SFR. Compared with the CST of raw sludge (36.45 s), sludge sample can be significantly reduced to 17.7 s. Characterization tests showed enhanced neutralization and agglomeration in co-conditioned sludge. Theoretical calculations revealed elimination of interaction energy barriers between sludge particles post co-conditioning, converting sludge surface from hydrophilic (3.03 mJ m-2) to hydrophobic (-46.20 mJ m-2), facilitating spontaneous agglomeration. Findings explain improved dewatering performance. Based on Flory-Huggins lattice theory, connection between polymer structure and SFR was established. Raw sludge formation triggered significant change in chemical potential, increasing bound water retention capacity and SFR. In contrast, co-conditioned sludge exhibited thinnest gel layer, reducing SFR and significantly improving dewatering. These findings represent a paradigm shift, shedding new light on fundamental thermodynamic mechanisms of sludge dewatering with different chemical conditioning.

Algae-based treatment of a landfill leachate pretreated by coagulation-flocculation.

Landfill leachate (LL) management is an urgent issue at recently closed Sisdol Landfill Site (SLS) used to dispose of solid waste generated in Kathmandu (Nepal) as untreated leachate is flowing directly to the nearby Kolpu River causing environmental and health concerns. This study aims to assess the potential of algae-based treatment of LL pretreated by optimized coagulation-flocculation (CF) for the removal of conventional pollutants such as biological oxygen demand (BOD5), chemical oxygen demand (COD), ammonia, nitrate, and phosphate. Response Surface Methodology (RSM) was used to optimize the operating variables (dose and pH) during the pretreatment of leachate by the CF process using ferric chloride (FeCl3.7H2O), alum (Al2(SO4)3.6H2O) and commercial poly aluminium chloride (PAC) as coagulants using a jar test apparatus. The pretreated LL was subjected to algal treatment using the mixed microalgae culture isolated and enriched from the wastewater collection pond and grown in artificial light. The combined physicochemical and algal treatment of LL from SLS achieved 62.93-72.43%, 74.93-75.55% and 87.58-93.40% and 73.63-86.73% removal for COD, BOD5, ammonium-nitrogen and phosphate, respectively. Thus, this research has proven the feasibility of a combined physiochemical and algae-based treatment of LL and also offers an exciting alternative to current treatment practices for LL.