Coagulant Dosage Research Articles

Enhancing the removal efficiency of microplastics in drinking water treatment

Microplastics (MPs) have been commonly detected in aquatic environments, however, the effectiveness of most drinking water treatment plants (DWTPs) in removing MPs is limited. The primary objective of this study was to investigate the efficacy of modified starch and traditional coagulants (PAC + PAM) in removing MPs through coagulation, followed by the application of biochar filtration for further removal of MPs present in the effluent from the coagulation process. The removal efficiency of MPs by modified starch / PAC + PAM was >80 %. Moreover, the incorporation of modified starch demonstrated a reduction in PAC coagulant dosage requirements. The main mechanism of modified starch was electrical neutralization, while the combination of modified starch with PAC + PAM effectively could utilize electric neutralization, adsorption bridge, and net sweep mechanisms. The MPs present in the coagulation effluent could be effectively eliminated by biochar, exhibiting a removal efficiency surpassing 90 %. And the coagulation-filtration process exhibited an exceptional efficacy in removing MPs, with removal efficiency reaching as high as 97 %.

Physical and Chemical Treatability Study in Wastewater Treatment Plant Design (Case Study: Leather Tanning Industry)

The leather tanning industrial is one of the industries that produces wastewater from its production process which contains several contaminants. In wastewater treatment plant design, the treatability study is important because it becomes a consideration in selecting treatment units in wastewater treatment plant based on the characteristics of the wastewater produced. Two methods were carried out in this treatability study, the physical method with imhoff cone sedimentation and the chemical method with jar test. The results of imhoff cone test found that the removal efficiency for wastewater samples was 80% of COD, 72% of BOD, 64.6% of TSS, 72% of total chromium, and 80% of color with the optimum sedimentation time of 50 minutes. Furthermore, the waste water sample was tested by the jar test by adding PAC and FeCl3. The results of the jar test obtained the optimum coagulant dose of 3000 mg/L with PAC coagulant, it was capable of removing 77% of COD, 33% of BOD, 92.68% of TSS, 33% of total chromium, and 98% of color. Based on the results achieved from this study, the physical and chemical treatment can be considered for use in WWTP planning in the leather tanning industry.

Improving bioenergy recovery from municipal wastewater with a novel cloth-filter anaerobic membrane bioreactor

Anaerobic membrane bioreactors (AnMBR) have been used for treating high-strength industrial wastewater at full-scale and the potential to use them for mainstream municipal wastewater treatment presents an important opportunity to turn energy-intensive plants into net-energy producers. However, several limitations of the AnMBR technology have prevented their adoption in the municipal wastewater industry, namely, high membrane cleaning energy demand and low membrane flux. This study demonstrated a novel AnMBR configuration that uses a commercially available cloth filter technology to address the key limitations of cleaning energy and membrane flux. The cloth filter anaerobic membrane bioreactor (CFAnMBR) is comprised of an anaerobic fixed-film bioreactor coupled with a cloth filter membrane with nominal pore size of 5 µm. The pilot CFAnMBR was operated for 150 days through the winter at a municipal wastewater plant in central Illinois (minimum/average influent temperature 5/13°C). The CFAnMBR increased membrane flux by more than 2 orders of magnitude (3,649 ± 1,246 L per meter squared per hour) and reduced cleaning energy demand by 78%—92% (0.0085 kWh/m3) relative to previously reported AnMBR configurations. With the CFAnMBR, average chemical oxygen demand and total suspended solids removal were 66% and 91%, respectively, and were shown to be increased up to 88% and 96% by in-line coagulant dosing with ferric chloride. Average headspace methane yield was 154 mL CH4/g CODremoved by the end of the study period with influent temperatures of 11°C± 4°C. The CFAnMBR resolves major limitations of AnMBR technology by employing a commercially-available technology already used for other municipal wastewater treatment applications.

Microplastic removal in batch and dynamic coagulation-flocculation-sedimentation systems is controlled by floc size

Most studies examining the removal of microplastics (MPs) during controlled bench-scale trials have applied high coagulant dosages, which are characteristic of sweep flocculation. As such the impact of other typical operating conditions remains largely unknown. The use of bench-scale jar testing is ubiquitous in the literature, however the hydrodynamics of a batch-type approach bear little resemblance to full-scale treatment processes. In this study, a range of microplastics sizes and types were employed to assess their removal via conventional jar tests as well as to compare results to a continuous-flow bench-scale system. Jar tests were performed to identify pH values and alum dosages that are optimal for MP reduction when considering a range of coagulation conditions. The production of large and readily settling aluminum hydroxide (Al(OH)3) floc represented the dominant condition driving MPs removal. However, total MP removal was observed to be lower during continuous-flow trials when compared to jar tests, suggesting that direct extrapolation of results from jar tests may overpredict performance observed at full-scale. Irrespective of microplastic type and size, strong correlations were observed between MP concentration and turbidity reduction, indicating that turbidity may potentially serve as a very useful surrogate. Significant correlations were observed when comparing both floc size, especially 90th percentile floc diameter, and concentration of floc >100 μm to the reduction of MPs.

Effective turbid water treatment using natural eco-friendly coagulants derived from oat and onion seeds

Conventional chemical coagulants are used for potable water treatment, which requires unsustainable mining and transformation of raw materials for their production with costly sludge disposal. Natural coagulants are potential alternatives to chemical coagulants. This study emphasized the use of natural eco-friendly coagulants (oat and onion seed) for turbid water treatment. Coagulant seeds were characterized by different techniques such as SEM, EDX, FTIR, and zeta potential analyzer. Response surface method (RSM) was used to optimize the coagulation process. The effect of initial water turbidity, pH, coagulant seed extract dose, slow mix time, and settling time on the efficiency of turbidity removal was studied. The relation between removal efficiency and the main three significant operational parameters (initial water turbidity, pH, and coagulant extract dose) was fitted to a quadratic model. The optimal removal was achieved at alkaline and neutral media (pH = 7–11 for oat extract and pH = 7–9 for onion extract). The turbidity removal efficiency was 99% using 6 ml/L oat extract dose and 98.9% using 4 ml/L onion extract dose at pH equal to 8 and initial turbidity of 190 NTU. The effect of using oat extract or onion extract with alum was studied, and the results indicated that the optimum dose was found to be 1 ml/L of a natural extract with 10 mg/L alum. Furthermore, oat and onion extract aids were able to decrease the organic load in the treated water. Oat and onion seed extracts were proven to be efficient and eco-friendly natural coagulants or coagulant aids for surface water treatment.

Avaliação do Emprego de Cloreto Férrico e Tanino como Coagulantes na Remoção de Sólidos de Efluentes Industriais

The circular economy has generated a lot of interest in the industrial sector, and one of the proposed principles is the reuse of waste generated by the industry. Considering this, it is important to apply adequate treatments for their reuse, thus avoiding inappropriate disposal, and to bringing economic advantages to the sector. The present proposal applied the alternative coagulants ferric chloride and tannin aiming at the removal of solids from the effluent generated in the painting booth of liquefied petroleum gas (LPG) containers of the company Supergasbras, located in Londrina-PR, considering it uses the iron sulfate. The experimental planning for the tests followed by varying two factors, sedimentation time and coagulant dosage, subdivided into 3 coded levels (+1, 0 -1), hence totalizing 9 experiments in duplicate. After the experiment, analyzes of pH, apparent color, turbidity and COD indicators were perfomed. Ferric chloride proved to be extremely efficient for turbidity removal and chemical oxygen demand, with values exceeding 90% of removal, in addition, the apparent color indicator also obtained a good result. However, in relation to the pH, all the tests with ferric chloride acquired an acid character, consequently it is necessary to use lime to correct the acidity. The application of the tannin organic coagulant, provided excellent efficiency in removing apparent color and turbidity, in addition to obtaining adequate pH values that comply with current legislation. Regarding the removal of the chemical demand for oxygen, it is approximately 90% for all tests using tannin as a coagulant.

Method for Extraction and Evaluation of Heliocarpus popayanensis and Triumfetta bogotensis as Natural Coagulants for the Treatment of Wastewater.

This research evaluates extracts from the bark of Heliocarpus popayanensis and Triumfetta bogotensis as coagulating agents for removing turbidity in domestic wastewater, considering the coagulant dosage and pH of the wastewater. ANOVA was conducted to assess differences between the coagulants, dosages, and pH, with three pH levels (5, 8, and 9) and six dosages (7, 9, 11, 13, 15, and 17 mL per 1000 mL of wastewater) at a significance level of α = 0.05, and both the p-value and effect size were evaluated. This study found that the mucilaginous compound from the bark of Triumfetta bogotensis performed better in reducing turbidity levels, with an average reduction of 30.2 NTU (Nephelometric Turbidity Unit) (CI [25.9 NTU; 34.5 NTU], α = 0.05) at a pH of 5, and an average initial NTU of 102.2. This represents an average reduction of 70.45%. The dosage factor did not show significant effects on turbidity reduction, which opens the possibility for further study to determine the optimal dosage of the best coagulant.

Milk-Clotting Properties and Primary Proteolysis of a Lyophilised Extract from Artichoke Flowers (Cynara scolymus L.).

A few studies have investigated Cynara scolymus enzymes as a substitute for calf rennet in cheese making. They used aqueous extracts prepared by maceration of plant material and stored by freezing. However, it was indicated that lyophilisation is a better alternative to preserve the coagulant properties of plant extracts over a longer period of time, as it is a more controllable, stable and hygienic alternative with a better shelf life that is easier to transport, store and standardise. We obtained a lyophilised extract of mature artichoke flowers, named CS, which was characterised for its milk-clotting properties at different pH and temperatures. In addition, the potential yield, whey composition and the primary hydrolysis profile of caseins by urea-polyacrylamide gel electrophoresis (PAGE) of mini curds prepared with different doses of coagulant were determined. The lyophilised extract was able to hydrolyse casein and showed stable proteolytic activity at pH=6.4 and 37 °C for 50 min, which decreased when the process temperature was increased to 41 and 45 °C and was lost at 70 °C. On the other hand, milk-clotting activity increased significantly (p<0.001) when the temperature increased from 37 to 45 °C and the pH of the milk decreased from 6.8 to 5.8. Potential yield ​​between 10 and 17 % was obtained for the mini curds prepared with the lyophilised artichoke extract, and the casein degradation pattern obtained by urea-PAGE was similar to that of the commercial coagulant. On a laboratory scale, our work has shown that the lyophilised artichoke extract has sufficient proteolytic and coagulant activity to be used as a milk coagulant, i.e. plant rennet, in cheese making as an alternative to animal rennet. As this extract is lyophilised, it has the advantage of being a better alternative in terms of preservation and shelf-life. It offers an innovative way to diversify cheese products and appeal to consumers with different dietary preferences and needs.

Differently charged polyacrylamides (PAMs) significantly affect adsorption affinity and associated floc growth behaviors during ballasted flocculation: Performance and mechanism

Various organic polymers have been widely used to provide inter-particle bridging between microsand and microflocs for producing ballasted floc aggregates during ballasted flocculation. However, it is not yet clear how differently charged polymers will determine predominant mechanisms of ballasted floc growth at diverse coagulant dosages. In this study, three representative aluminum sulfate (AS) coagulant dosages (where microfloc aggregates formed after coagulant addition possessed negative, zero and positive zeta potentials, respectively) were prearranged, and then the role of cationic, anionic and nonionic polyacrylamides (PAMs) in ballasted flocculation of clay suspensions was comparatively evaluated at each AS dosage. As expected, the temporal evolution of floc average size at stages of ballasted floc maturation and regrowth (following breakage) was dependent upon both AS coagulant dosage and PAM selection. Also, the selection of differently charged PAMs produced maturated floc aggregates with different shear-resistant and recovery abilities at a fixed AS dosage, presumably owing to the predominant mechanism of ballasted floc growth. Differently from the removal efficiency of water turbidity after sedimentation, the involvement of nonionic PAM (rather than the case of “without adding PAM”) gave rise to the lowest removal percentage of UV254 at the same AS dosages. This finding was probably attributed to the role of possible flocculation mechanism(s) in the transformation of dissolved humic acid (HA) complexes into insoluble HA composites at the maturation stage. Based on the experimental results, a conceptual model of ballasted floc growth process induced by differently charged polymers was proposed to vividly explore the possible floc-growth mechanism (such as charge neutralization, polymer bridging, and/or electrostatic patch) occurring for each combination of coagulant dosage and PAM type. This research may contribute to gaining a deep insight into the combined effects of coagulant dosage and differently charged polymer selection on the interaction between polymer-enhanced floc cohesion and ballasted floc formation.

Comparative assessment of different scenarios for upgrading activated sludge wastewater treatment plants in developing countries

Improvement of current wastewater treatment plants (WWTPs) to accommodate the growing influent flow rate and cope with the increasingly stringent regulations is hindered by the allowed space and the difficulty of changing the design parameters. Mathematical modeling is a useful tool for assessing the performance of WWTPs in light of broadening objectives. We herein explore the utilization of mathematical modeling to improve effluent quality in conventional activated sludge systems. BioWin was used to model Mansoura WWTP, one of the largest WWTPs in Egypt. Lab records, design reports, and additional analyses were conducted through site visits and a comprehensive sampling campaign. The wastewater was characterized, and the plant-wide model was calibrated following the protocol of the Dutch Foundation for Applied Water Research STOWA. Important kinetic and stoichiometric parameters were identified and adjusted during the calibration process. The model validity was assessed using different validation periods considering average relative deviation (ARD) values below 20 % as acceptable. The optimized nitrification and denitrification processes involved 16 scenarios with different operational conditions. By changing some zones in the aeration basin from aerobic to anoxic and increasing the return activated sludge, the average ammonia and nitrate concentrations were significantly reduced from 23.06 and 0.5 mg/L to 4.64 and 0.07 mg/L respectively. Furthermore, phosphorus removal optimization was carried out through biological and chemical processes. Chemical phosphorus removal was 85.76 % by using a coagulant dosage of 25 mg/L, resulting in an effluent concentration of 1.04 mg P/L. Biological phosphorus removal was increased to 85.43 % by modifying the volume of anaerobic and aerobic zones with lower power consumption. Overall, this study demonstrates the effectiveness of mathematical modeling in enhancing effluent quality and reducing energy consumption to meet stringent wastewater treatment regulations.

Vanadium removal and floc characteristics of tannin biocoagulants and iron sulphate in the treatment of mine effluent

This study compared the performance of tannin (quebracho and spruce) and iron sulphate (FS) coagulants for the removal of vanadium from effluent derived from an abandoned vanadium mine. The efficacy of the materials was studied at the natural pH of the mine effluent (7.4), and at adjusted pH levels of 4 and 9. The quebracho tannin coagulant (QT) recorded impressive turbidity and vanadium removals of above 88% over a wide pH range. However, the spruce tannin coagulant (ST) was not as effective at pH 9 (39%) although it showed an improved vanadium removal of 46% and 70% at pH 7.4 and 4, respectively. This was attributed to the lower charge density of ST than that of QT, and to a loss of cationic properties at pH 9. FS performed better in terms of vanadium removal (pH 4: 86%, pH 7: 98%, pH 9: 100%) with lower coagulant doses, although effective turbidity removal required precise pH control. QT produced the largest flocs and the highest floc regrowth at pH 4 and 7. Under alkaline conditions, tannin coagulants exhibit no regrowth, which implies that a careful flocculation and floc separation step is needed. The natural organic matter fractionation results revealed that FS effectively removed hydrophilic carbon (76%) in a pH-controlled mine effluent better than tannin coagulants (QT: 12% and ST: 22%) from the pH 4 effluent; however, ST removed hydrophobic carbon entirely. All coagulants adequately removed humic substances, with FS being the most efficient (88%), followed by ST (53%) and QT (47%). X-ray photoelectron spectroscopy (XPS) analysis of jar test residues showed that some of the vanadium removed existed in the V(IV) oxidation state.

Moderate pre-photocatalysis-enhanced coagulation alleviates ultrafiltration membrane fouling of algae-laden water

Moderate chemical pre-oxidation of coagulation to remove algae without breakage of the algae cells and release of algal organic matter has been well reported, while little was known about moderate pre-photocatalysis followed by coagulation on the ultrafiltration performance and membrane fouling control during algae-laden water treatment. Herein, three pretreatment methods (photocatalysis, coagulation and moderate pre-photocatalysis-enhanced coagulation (PC)) were investigated to reduce membrane fouling during ultrafiltration of algae-laden water. Moderate photocatalysis by a composite of Bi2O3-TiO2/PAC (Bi-doped TiO2 nano-composites supported by powdered activated carbon) not only avoided algae cell breakage and controlled the release of intracellular organic matter, but also halved the aluminum sulphate (AS) coagulant dosage, since Bi2O3-TiO2/PAC acted as both a photocatalyst and flocculation core. Under optimal conditions (1.2 g/L Bi2O3-TiO2/PAC irradiated under visible light for 20 min and 0.1 mM AS), the removal of OD680, DOC and UV254 were 83.8 %, 60.3 % and 77.3 % respectively. Moderate photocatalysis degraded medium and high molecular weight organics (biopolymers, humic substances and building blocks) to low MW acidic and neutral organics, resulting in effective removals of humic substances and microbial metabolites typically present in algal-derived pollutant. Following PC pre-treatment with ultrafiltration, 87.5 % increase in the final specific flux, 96.1 % reduction in irreversible resistance, and a change in the fouling mechanism from cake layer blockage to intermediate blockage. In addition, the zeta potential was reduced and the interaction force between pollutant-pollutant/membrane became a repulsive force. This work demonstrates the potential benefits of moderate pre-photocatalysis-enhanced coagulation to remove algal contaminants and mitigate ultrafiltration membrane fouling.

Optimization Studies on the Coagulation–Flocculation Process for PWW Treatment Using Cactus oputia Extract: Comparative Studies for Performance Evaluation

The treatment of Paint Waste Water, PWW is an important global issue for the minimization of water pollution especially in a developing country like Nigeria. The coagulation–flocculation process using Cactus Oputia Extract, COE as natural coagulant is reported for PWW treatment in the present study. The important process parameters pH, settling time, coagulant dosage and initial concentration were optimized using design of experiments (DOE). A full factorial composite experimental design and response surface methodology (RSM) were used to obtain the optimum values of the parameters. Also utilized in this study were Artificial Neural Network, ANN and Adaptive Neuro Fuzzy Inference System, ANFIS for performance evaluation. Using the numerical optimization technique of the design expert software, a combination of factors which concurrently fulfil the requirements placed on the response variable were determined. The best effluent removal efficiency was predicted to be 89.78% at the optimum values of the process parameters pH 6, settling time 30 mins, coagulant dosage 3 g and initial concentration 1.2 mg/l in this study.

Neural Network Modelling for Prediction of Coagulant Dosage

Water treatment plants (WTP) in Indonesia commonly applied conventional treatment that, among others, relies on the coagulation process to treat turbid surface water to produce clean and safe water for daily purposes. Meanwhile, standard Jar-Test methods for coagulant dosage determination are inefficient, inaccurate, and possibly will not function well for water with high variability of quality. This study aims to improve and optimize the coagulant dosing process by considering the main parameter that greatly affects the coagulation process, i.e., turbidity. For this purpose, a multilayer artificial neural network model (ANN) with an adaptive backpropagation algorithm was developed using MATLAB software. A network architecture with 1 input, 5 hidden and 1 output was implemented. For the input, 4465 turbidity data of the raw water taken from Surabaya Municipal Water Enterprise (PDAM) were used, while the output is the optimal dose obtained from the results of the Jar-test. This study resulted in an empirical model of the optimum dosage of coagulants as a function of the turbidity of the raw water. Training and testing on the given ANN resulted in R2 (determination coefficient) of 0.99444 from regression analysis with the following equation: output = 0.99 x target + 0.66. This study showed that the ANN model provides a very high success rate for coagulant dose prediction.

Anaerobically Digested Distillery Wastewater Treatment Using Coagulation–Flocculation Followed by Microalgal Treatment: Optimization of Coagulant Dosage, Dilution Ratio, and Photoperiod

Anaerobically Digested Distillery Wastewater Treatment Using Coagulation–Flocculation Followed by Microalgal Treatment: Optimization of Coagulant Dosage, Dilution Ratio, and Photoperiod

Optimization of the use of natural coagulants in wastewater treatment using Rotational Central Composite Design

Contamination of water resources by industrial effluents represents a major environmental problem and, in Brazil, the dairy industry is one of the main causes of these problems. The composition of its effluent has a high amount of organic matter and nutrients and, therefore, it is necessary to treat them before disposal. This study aimed to optimize the treatment of synthetic dairy effluents, simulating the coagulation/flocculation process, through the application of a natural coagulant based on Moringa oleifera seed extract, using the Rotational Central Composite Design associated with the Surface Methodology response (MSR). The independent variables in the project were the fast and slow mixing times, the coagulant dosage and the concentration of pollutants. A mathematical model was established with an R² of 0.6, in which the significance of the pollutant concentration and coagulant dosage was proven. From the re-parameterization of the mathematical model, considering only these two variables, an adjustment of 74% was obtained. As a result, a removal efficiency of 94.9% of turbidity was obtained, demonstrating – in the first approximation analysis – a strong result for the use of a natural coagulant to remove turbidity from dairy effluents.

Performance evaluation and optimization of the treatment of dye laden wastewater using alum and Luffa cylindrica seed extract as coagulant

AbstractThe treatment of dye laden wastewater (DLW) was investigated using alum, and Luffa cylindrica seed extract, . Cibacron green dye and distilled water were used to simulate the DLW in the laboratory. The optimum conditions for the removal of color and chemical oxygen demand (COD) from DLW was determined using both regular and response surface methodology, RSM‐Jar tests with coagulant dosage, DLW pH, stirring time, and temperature as the independent variables. Instrumental characterization of the coagulant and produced sludge were studied. Individual effect using regular Jar test, and had best color removal efficiency of 98.4% (2 g/L, pH 8, 30 min and 55°C), and 97.7% (5 g/L, pH 2, 20 min and 55°C), respectively. Also, for COD removal efficiency, and had 85.6% (2 g/L, pH 10 and 30 min), and 88.1% (4 g/L, pH 4 and 30 min), respectively. Applying RSM‐Jar test, 99.6% and 88.7% color and COD removal efficiency were achieved with 4 g/L , 0.25 g/L , pH 8, and 40°C and 5 g/L , 0.40 g/L , pH 6, and 40°C, respectively. The results indicated that the combination of both coagulants () performed maximally with highly reduced alum dosage, exposing the novelty of the work. Hence, the novelty of the work is the use of minimal quantity of alum and Luffa cylindrica seed extract for effective removal color and COD from the DLW.

Ballasted flocculation pretreatment for mitigating ultrafiltration membrane fouling: Role of differently charged polyacrylamides at typical coagulant dosages

In this work, ballasted flocculation (without sedimentation) was suggested as a potential pretreatment for ultrafiltration to improve cake layer microstructure and mitigate membrane fouling. First, three representative aluminum sulfate (AS) coagulant dosages (including 1.0, 2.5 and 8.0 mg Al/L) were determined during preliminary testing to produce microfloc aggregates with negative, zero and positive zeta potentials at the coagulation stage of ballasted flocculation. Regardless of the applied coagulant dosage, not only ballasted floc size but also their strength and recovery abilities (following breakage) were dependent upon the selection of differently charged polyacrylamides (PAMs), likely due to the effect of PAM selection on polymer bridging and associated flocculation mechanisms. Second, comparisons of membrane flux decline and resistance distribution were performed to evaluate the importance of coagulant dosage and PAM type to cake layer formation and membrane fouling potential in the ballasted flocculation and ultrafiltration integrated process. The results demonstrated that the ballasted floc aggregates formed by ballasted flocculation pretreatment contributed to diverse structural characteristics of the fouled layer during their accumulation on the membrane surface, thereby affecting the degree of membrane fouling for various combinations of AS dosage and PAM type. Besides, the microsand particles involved in the formed layer could act as a skeleton of the cake layer structure, so their spatial distribution within the layer interior played a critical role in cake layer microstructure improvement, ultrafiltration efficiency enhancement and membrane fouling mitigation. In other words, the extent of steric-hindrance effects by ballasted floc aggregates should be emphasized in the formation of cake layer.

Simultaneous modulation of CHO cell cytotoxicity, turbidity, and DOC by coagulation with or without pre-oxidation in water from the Pearl River Delta region, China

Coagulation with or without pre-oxidation are important drinking water treatment processes. However, the efficacy of these processes in mitigating water toxicity remains unknown. To further improve drinking water safety, we employed water from the Pearl River Delta region of southern China to investigate a treatment approach consisting of coagulation with or without pre-oxidation to simultaneously modulate health-relevant cytotoxicity to CHO cells, on top of the conventional foci of turbidity and dissolved organic carbon (DOC) during water treatment. Three coagulants (two aluminum-based and one iron-based salts) and three pre-oxidants (ozone, permanganate, and peroxymonosulfate) were studied. For coagulation without pre-oxidation, intermediate coagulant doses and pH reached optimum cytotoxicity to CHO cells, turbidity, and DOC control simultaneously. Introducing oxidants reduced cytotoxicity to CHO cells significantly, enhanced by increasing oxidant concentrations and pre-oxidation duration. The cytotoxicity to CHO cells mitigation capabilities of three pre-oxidants were: ozone > peroxymonosulfate > potassium permanganate. Modulation of water cytotoxicity to CHO cells was mostly attributable to controlling DOC (specifically humic-acid like substances, tyrosine, tryptophan). However, the addition of pre-oxidants led to significant shifts in water cytotoxicity to CHO cells forcing drivers, rendering humic-acid like substances the sole decisive cytotoxicity-inducing fluorophores. For the first time, ‘sweet spots’ were identified to simultaneously monitor cytotoxicity to CHO cells alongside turbidity and DOC. These methods better modulate water cytotoxicity to CHO cells without sacrificing conventional water treatment goals while shedding light onto the mechanisms behind.

A combined experimental-modeling approach for turbidity removal optimization in a coagulation–flocculation unit of a drinking water treatment plant

The drinking water treatment plant plays a key role in providing the consumers with a safe water, in compliance with the United Nations Sustainable Development Goal n. 6 (Clean water and sanitation). The typical drinking water treatment plant includes: coagulation–flocculation,​ sedimentation, filtration and disinfection. Turbidity removal is among the more common pollutants to remove; this goal is mainly achieved by the coagulation–flocculation process. The present paper shows the results of the application of a combined experimental-modeling approach for turbidity removal optimization in a coagulation–flocculation unit of a full-scale drinking water treatment plant. The applied approach consisted of a laboratory experimental activity aimed at determining the best coagulant type and dosage. Among the different chemicals tested, Poly aluminum chloride (PAC) provided the highest removal at the lowest dosage (90% at 3.5 mg/L PAC, 88% at 18.9 mg/L PACS and 77% at 30 mg/L FeCl 3). The addition of polyelectrolytes did not improve the removal at such a level to justify the consequent increase of the costs. Based on the findings of this phase of the study, a data-driven model was implemented using as input variables the historical data of influent and effluent turbidity and influent flow rate. Combining regression models and statistical analysis, it was possible to build up an algorithm for the case-study plant allowing to select the PAC dosage to apply as a function of the influent turbidity, to ensure the constant compliance with the regulation limit on effluent turbidity.