Coagulant Dosage Research Articles

Effect of Natural Coagulants on the Treatment of Municipal Wastewater

Nowadays, the study of the natural coagulants to treat wastewater has become a growing interest to the environmental researchers around the world as its numerous advantages over chemical coagulants. In this study, the effect of banana peel powder and banana stem powder as natural coagulant on the treatment of municipal wastewater was investigated. Wastewater samples were collected from two different primary drains located near Padma garden and Bornali within Rajshahi city corporation area. The collected wastewater samples were characterized based on turbidity, pH, conductivity, TDS, TSS, TS, alkalinity, acidity and organic content and also compared with maximum permissible limits before going treatment. The worst wastewater sample was treated with varying coagulant doses, contact time, speed and pH. The effectiveness of natural coagulants was evaluated based on the percentage removal of turbidity, alkalinity and acidity. The highest removal of turbidity, alkalinity and acidity were obtained 93.5%, 67.3% and 65.5% by banana peel powder and 93.4%, 71% and 72% by banana stem powder respectively. Therefore, the result revealed that both banana peel powder and banana stem powder had capability to treat municipal wastewater as natural coagulant. Higher treatment conditions were not economically feasible because it did not significantly remove the pollutants. The removal of alkalinity and acidity indicated that it was a partial coagulation and partial adsorption process in which both materials also had high adsorption capacities.

Modelling coagulant dosage in drinking water treatment plant using advance machine learning model: Hybrid extreme learning machine optimized by Bat algorithm.

Despite the high importance of coagulation process in drinking water treatment plant (DWTP), challenge remains in effectively linking raw water quality measured at the inlet of the DWTP with coagulant dosage rate. This study proposes an integral modelling framework using hybrid extreme learning machine and Bat metaheuristic algorithm (ELM-Bat) for modelling coagulant dosage rate using water temperature, pH, specific conductance, dissolved oxygen, and water turbidity. The aluminum sulphate (Al2 (SO4)3.18H2O) coagulant is determined using conventional Jar-Test procedure. Results obtained using the hybrid ELM-Bat were compared to those obtained using standalone ELM, outlier robust extreme learning machine (ORELM), online sequential extreme learning machine (OSELM), optimally pruned extreme learning machine (OPELM), and kernel extreme learning machine (KELM). First, the models have been calibrated during the training stage and in a second stage; they are validated using various statistical metrics, i.e., RMSE, MAE, the correlation coefficient (R), and the Nash-Sutcliffe model efficiency (NSE). We found that the hybrid ELM-Bat was significantly more accurate and it has yielded accuracy higher than all other models. During the validation stage, the R and NSE values calculated using the ELM-Bat were ≈0.959 and ≈0.918 exhibiting an improvement rates of approximately (≈15.26% and ≈33.82%), (≈10.35% and ≈21.92%), (≈14.98% and ≈31.89%), (≈7.63% and ≈16.35%), (≈10.99% and ≈23.05%), compared to the values obtained using the ELM, OPELM, OSELM, KELM and ORELM, respectively. Besides, the new ELM-Bat model has shown to have high predictive capabilities, which can be used optimally for calculating the optimal coagulant dosage with high accuracy.

The use of a pumice stone in removal of petroleum hydrocarbons from industrial wastewater through coagulation and flocculation

Background: Petroleum hydrocarbons that are released from industrial processes cause damage to aquatic life and degrade ecosystems by accumulating in the food chain, allowing living organisms to produce toxic secretions. Methods: In this study, a pumice stone was used to remove total petroleum hydrocarbons (TPHs) from industrial wastewater in the south refinery company in Iraq/Basrah by coagulation and flocculation processes using the design of experiments (DOE) approach using the method of analyzing screening designs and measurement of the samples using GC instrument. Results: The maximum removal was 99% at pH 3, coagulation dose of 0.5 g, and time of 60 min, and a comparison was made between the DOE and the multiple linear regression (MLR) to determine the effectiveness of the system used, which proved its incredible effectiveness. Conclusion: According to the results, a great convergence between the actual and prediction results of removal was found, while MLR was very far from the actual and predicted removal results. The high efficiency of pumice stone was found in removing petroleum hydrocarbons from the industrial wastewater of the South Refineries Company. Pumice stone is widely available in the market and cheap economically.

Use Of Tannin Mimosa Based Natural Coagulants For Wastewater Treatment: Optimization and modeling using RSM Methodology

Industrial waters are discharges classified as hazardous because of their quantity, concentration or the physical and chemical properties of their constituents (turbidity, heavy metals, organic or phosphorus compounds) that threaten human health and the environment. Among the hazardous industrial waters, we distinguish industrial wastewater. These industrial discharges contain various products in insoluble or soluble form of mineral and/or organic origin, more or less biodegradable and sometimes toxic even in very low concentrations.
 In this work, the coagulation-flocculation process was used as a new technology approach for the treatment of this type of rejection. In this study, the jar test was used to determine the optimal conditions of the coagulation-flocculation process using mimosa tannins as natural coagulant by applying a response surface methodology (RSM) based on the bencken box design (BBD) of three levels with three factors (PH, coagulant dosage and setting time) . The BBD is successfully demonstrated to effectively determine the optimized parameters, where 97% of the water turbidity was removed with an initial value of 201 NTU for the optimal conditions of pH (5), coagulant dosage (10 mL/L), settling time (60 min). To evaluate the performance of optimization and modeling of coagulation flocculation process, the coefficients of determinations R2 and R2 adjusted were used, the results obtained clearly show that the R2 (97.20%) and R2 adjusted (92.16%) obtained confirm the validity of this mathematical model.

The role of coagulation on the fate of PFAS, brominated flame retardants and other trace contaminants in tertiary wastewater treatment for phosphorus control

Coagulant dosing to achieve low phosphorus concentrations in wastewater effluents may favour the removal of trace organics such as pharmaceuticals, plasticisers and flame retardants. Nevertheless, the behaviour of trace organics in coagulation processes is currently poorly understood because of the complex interactions between these compounds, the coagulants and dissolved organic matter (DOM). This study assessed the coagulation removal from synthetic secondary effluent of twenty-four compounds including ten PFAS and four brominated flame retardants. Testing involved two coagulants (alum, ferric chloride) and five DOM surrogates (resorcinol, benzoic acid, citric acid, tannic acid, humic acid); DOM surrogates had assorted molecular weights, structures, charges, and hydrophobicity. With coagulant doses of 14 mg Fe/L and 4 mg Al/L, ten trace organics were removed by >30 % in the presence of at least one DOM surrogate. Humic acid effected the highest removals owing to complexation of trace organics and subsequent co-removal by adsorption or sweep floc. For instance, removal extents for three brominated diphenyl ethers were 60 to 75 % with Al and 50 to 88 % with Fe (initial concentration 0.4 to 0.8 ng/L); PFTDA, a long-chain PFAS, was removed by 87 and 91 % with Fe in the presence of tannic or humic acid, respectively (initial concentration 0.03 μg/L). The varying coagulation performance of different treatment works in terms of trace substance removal can be explained because of the site-specific DOM characteristics. Addition of humic acids as complexing agents has the potential to improve the removal of hydrophobic trace substances, including some long-chain PFAS and brominated flame retardants.

Modeling of a novel cascade-type electrocoagulation reactor using iron electrodes. Characterization of bubbling flow and coagulant dosage

This paper deals with the bubbling flow and coagulant dosage modeling in an innovative continuous cascade-type electrocoagulation (EC) reactor using iron plate electrodes. The reactor comprises seven iron plates. It is open to the atmosphere at the top to release the hydrogen bubbles produced at the cathode during the reduction of H2O. In this context, a two-phase flow model (H2OH2) was formulated. The H2OH2 flow was obtained by the solution of the Reynolds Averaged Navier-Stokes (RANS) equations for the continuous phase (H2O), which was coupled to the slip model for the dispersed phase (H2). Since H2 bubble formation co-occurs at the cathode as the aqueous solution passes through the continuous EC reactor, the two-phase flow and Laplace equations were solved simultaneously. The modeling of the ferric ion coming from the anodic dissolution was carried out by solving the diffusion-convection equation. The influence of the mean linear inflow velocity (2.63 ≤ u ≤ 2.56 cm s−1) and current density (4 ≤ j ≤ 8 mA cm−2) on the H2 dispersion and coagulant formation (Fe3+) was systematically examined. A comparison between simulated and experimental Fe3+ doses showed deviations < 4%. Excellent agreement between experimental and theoretical residence time distribution curves was obtained.

Chitosan of blood cockle shell (Anadara granosa) as a natural coagulant for removal of total suspended solids (TSS) and turbidity of well-water

Blood clam or blood cockle (Anadara granosa) is a clam species with high calcium carbonate (CaCO3) and chitin content; these compounds are commonly used in coagulation water treatment. This study examined the capacity of blood cockle shells (BCS) as an innovative natural coagulant in the form of unmodified powder (BCSP) and chitosan extracted from the shells (BCSC) to reduce TSS and turbidity of well-water. SEM and FTIR analysis were conducted to analyse the characteristics of the media. The coagulant dose, pH of the water sample, and settling time were investigated using a jar test experiment to determine the optimum condition for each experimental system. Rapid mixing (1 min at 120 rpm) was followed by slow mixing (10 min at 60 rpm), followed by settling times ranging from 10 to 30 min. The optimum settling time was 30 min, after which 76% TSS and 76% turbidity were removed using 75 mg/l of BCSP at pH 4. The tests with BCSC resulted in 80% TSS and 81% turbidity removal with 200 mg/l of BCSC at pH 5 and a settling time of 30 min. The results were compared to the performance of alum (Al2(SO4)3·18H2O), a commercial chemical coagulant. Under similar dosage (200 mg/L) and pH (= 6) conditions, alum reduced turbidity and TSS by 95% and 97%, respectively. These results indicate that blood cockle shell-based coagulant is a promising environmental-friendly material that can compete and possibly replace conventional chemical coagulants in water treatment systems.

Liquid treatment of food coloring industry waste using coconut and chitosan in removal dyes

Liquid waste has a component containing water that has been mixed with chemical compounds. One example of liquid waste containing chemical compounds is wastewater from a food coloring industry. The liquid waste of the food coloring industry has a very strong color density so that it has a negative impact on the environment, therefore it is necessary to treat liquid waste in order to meet the quality standards of wastewater in accordance with East Java Governor Regulation number 72 of 2013. The purpose of this study was to determine the effect of adding dose of coagulant and mass of biosorbent on percent color removal in food coloring industrial wastewater. The results showed that the addition of 35% coagulant and 13% biosorbent resulted in 97% optimal removal of color.

Moringa oleifera Seed Addition Prior to Sludge Thickening for Supernatant Quality Improvement: Analyses of Clarification Performance and Toxicity

Low-cost and easily accessible sludge treatment technologies are necessary in low- and middle-income countries. This study aimed to evaluate the use of Moringa oleifera seed powder (MO) as a natural sludge conditioner for supernatant quality improvement prior to thickening as a result of gravity settling. The zone settling rate (ZSR) and sludge volume index (SVI) were used to evaluate the gravity settling capacity. Supernatant clarification was evaluated in terms of the capacity to remove turbidity, apparent colour, Escherichia coli, and organic matter associated with zeta potential evolution. The effects on the values of pH and electrical conductivity were also evaluated. Finally, the effects on the toxicity (chronic and acute) of the supernatant effluent were examined. A significant supernatant quality improvement was observed with the addition of MO. The ZSR (0.16 cm/min) and SVI (53 mL/g) results showed that the sludge had good sedimentability, and the addition of MO maintained these characteristics in a statistical manner. Increasing the MO dosage increased the zeta potential of the supernatant, resulting in an optimal dosage of 1.2 g/L, with a removal of 90% turbidity, 70% apparent colour, 99% E. coli, and 40% organic matter. The pH and electrical conductivity values did not change with increasing MO dosage, which is a competitive advantage of MO addition compared to iron and aluminium salt addition. A reduction in the ability to remove organic matter was observed at higher dosages of the natural coagulant due to the presence of residual MO in the final effluent. The optimal MO dosage of 1.2 g/L did not affect the acute or chronic toxicity of the supernatant. These results emphasized that M. oleifera seed powder can improve the supernatant quality and can potentially be a low-cost and easily accessible conditioner for wastewater sludge thickening.

Use of Plant-Based Coagulants Sorghum Bicolor and Trifolium Repens as Future Alternatives for Textile Wastewater Treatment Based on Computational Model

Sorghum bicolor and Trifolium repens extracts as plant coagulants can be used for wastewater treatment instead of chemical coagulants. This study investigates the effects of pH and coagulant dose on COD and turbidity reduction by natural coagulants. In the optimum treatment conditions of 100 mg/L coagulant dose and pH 7, high turbidity (81.34%), and COD reduction (62%) (Compared with Alum and FeCl3) were obtained. The percentage of COD reduction is higher in Trifolium repens than the other plant coagulant and the percentage of turbidity reduction is higher in Sorghum bicolor. FT-IR spectra were performed on the plant extracts to identify the existing factors in active extracts. Also, outlet COD and turbidity values can be calculated according to computational equation in similar treatment systems where using the same plant coagulants. It should be mentioned that the only applied solvent for extracting the natural coagulant seeds, was distilled water and none of the other solvents such as NaCl and NaOH were used. According to the results, the characteristics of the treated effluents by the plant extracts make them appropriate alternatives for textile wastewater treatment.

Removal behaviors and mechanism of polystyrene microplastics by coagulation/ultrafiltration process: Co-effects of humic acid

Microplastics (MPs) have been detected in drinking water, which could absorb or accumulate humic acid (HA) and threaten the water quality. Coagulation-ultrafiltration (CUF) is a common drinking water treatment technology, but its behavior and mechanism of removing MPs and MPs-HA remain unclear. In this study, the removal mechanism of polystyrene (PS)-MPs coagulated by Al- and Fe-based salts with or without HA was investigated to optimize the CUF process. The results showed that Al-based salt (92.7 %) was better than Fe-based salt (91.2 %) in the removal efficiency of PS or HA, and the optimal coagulants dosage of PS-HA composite system (12 mg·L−1) was higher than that of the individual PS system (9 mg·L−1). Moreover, the coagulation mechanism was studied by Fourier transform infrared spectroscope (FTIR) and X-ray photoelectron spectroscopy (XPS). The oxygen group in PS and PS-HA was the main binding site of Al and Fe hydrolysate, and the effects of charge neutralization, adsorption bridging, and sweep flocculation became weaker in turn at the optimal dosage. In addition, the cake layer formed by coagulation and the presence of HA alleviated the irreversible membrane fouling by intercepting flow and re-adsorption. This study guides the improvement of the traditional drinking water treatment process to remove MPs.

Cake layer 3D structure regulation to optimize water channels during Al-based coagulation-ultrafiltration process

The variation in cake layer three-dimensional (3D) structures and related water channel characteristics induced by coagulation pretreatment remains unclear; however, gaining such knowledge will aid in improving ultrafiltration (UF) efficiency for water purification. Herein, the regulation of cake layer 3D structures (3D distribution of organic foulants within cake layers) by Al-based coagulation pretreatment was analyzed at the micro/nanoscale. The sandwich-like cake layer of humic acids and sodium alginate induced without coagulation was ruptured, and foulants were gradually uniformly distributed within the floc layer (toward an isotropic structure) with increasing coagulant dosage (a critical dosage was observed). Furthermore, the structure of the foulant-floc layer was more isotropic when coagulants with high Al13 concentrations were used (either AlCl3 at pH 6 or polyaluminum chloride, in comparison with AlCl3 at pH 8 where small-molecular-weight humic acids were enriched near the membrane). These high Al13 concentrations lead to a 48.4% higher specific membrane flux than that seen for UF without coagulation. Molecular dynamics simulations revealed that with increasing Al13 concentration (Al13: 6.2% to 22.6%), the water channels within the cake layer were enlarged and more connected, and the water transport coefficient was improved by up to 54.1%, indicating faster water transport. These findings demonstrate that facilitating an isotropic foulant-floc layer with highly connected water channels by coagulation pretreatment with high-Al13-concentration coagulants (having a strong ability to complex organic foulants) is the key issue in optimizing the UF efficiency for water purification. The results should provide further understanding of the underlying mechanisms of coagulation-enhancing UF behavior and inspire precise design of coagulation pretreatment to achieve efficient UF.

Color and COD Removal from Textile Effluent Using Alum and FeCl3 Coagulation

Textile dyeing companies use large amounts of water and chemicals during thedyeing process. Large amounts of sewage containing hazardous materials havebeen released into a nearby water bodies, posing a threat to environmentalsustainability. The aim of this research was to find out how the type and dosageof coagulant affect the removal of colour and COD from industrial wastewatercontaining dye using ferric chloride and Alum. The efficiency of thesecoagulants was determined using the jar test, which examined the percentagefrom dye removal in different wastewaters, coagulant dose, initial dyeconcentration, mixing velocity, and sedimentation duration. The highestdecolorization efficiencies for FeCl3 and Alum coagulants were 81% and 81%,respectively. Rremoval COD was 46% and 42% for FeCl3 and Alum,respectively. Where pH 11 and coagulant doses of 20 and 30 mg/L for FeCl3 andalum, respectively, the coagulants performed better. The results of the studyrevealed that FeCl3 is more successful than Alum in removing color and CODfrom industrial effluents containing Congo red dye. Because the dose ofcoagulant used is less. On the other hand, the physicochemical method can beused as a successful pre-treatment method before subsequent treatment of thepartially stabilized leachate.

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

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

Modeling and optimization of the coagulation/flocculation process in turbidity removal from water using poly aluminum chloride and rice starch as a natural coagulant aid.

The application of the coagulation/flocculation process is very important due to its simplicity in removing turbidity. Due to the disadvantages of using chemical coagulants in water and the lack of sufficient effect of natural materials alone in removing turbidity for proper performance, the simultaneous use of chemical and natural coagulants is the best way to reduce the harmful effects of chemical coagulants in water. In this study, the application of poly aluminum chloride (PAC) as a chemical coagulant and rice starch as a natural coagulant aid to remove turbidity from aqueous solutions was investigated. Effects of the above coagulants on the four main factors, coagulant dose (0-10mg/L), coagulant adjuvant dose (0-0.1mg/L), pH (5-9), turbidity (NTU 0-50), and each five levels were assessed using a central composite design (CCD). Under the optimized conditions, the maximum turbidity elimination efficiency was found to be 96.6%. The validity and adequacy of the proposed model (quadratic model) were confirmed by the corresponding statistics (i.e., F-value of 23.3, p-values of 0.0001, and lack of fit of 0.877 for the model, respectively, R2 = 0.88, R2adj. = 0.84, R2 pred = 0.79, AP = 22.04).

Synergetic Effect of Chemical Coagulation and Electroflotation on Synthetic Palm Oil Mill Effluent Treatment

Palm oil mill effluent (POME) is considered the most environmentally harmful when discharged without proper treatment. In addition to conventional biological treatment methods, physicochemical treatment techniques are considered alternative methods to treat POME as polishing or post-treatment techniques to meet the discharge water quality standards set by authorities. Recently, electroflotation (EF) has gained popularity in wastewater treatment owing to its high efficiency, no harmful by-products, and ease of operation. However, EF has limitations on energy consumption because high current density and long electrolysis time are often used to increase the density of gas bubbles and metallic ions produced in the EF system used in pollutant removal. Polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) are used as alternative options for the production of coagulants instead of using a sacrificial anode in EF. In this study, we hypothesized that PAC and CPAM could enhance the efficiency and reduce the specific energy consumption of EF by minimizing the electrolysis time used in POME treatment. The effects of electrolysis time, current density, and coagulant dosage on POME treatment were investigated. EF treatment at a current density of 2.5 mA/cm2 has achieved 82% of turbidity and 47% of chemical oxygen demand (COD) removal after 45 min electrolysis time, consuming 0.014 kWh of specific energy for the treatment of one gram of COD. There was no improvement in terms of turbidity removal when the current density was increased from 2.5 to 5 mA/cm2; however, the COD removal efficiency was increased up to 52% at 5 mA/cm2. When EF was performed at 1 A combined with PAC at a dosage of 40 mg/L and CPAM at a dosage of 20 mg/L, it was noticed that turbidity and COD removal increased up to 96% and 54%, respectively, within 15 min electrolysis. Subsequently, the specific energy consumption was reduced to 0.004 kWh (by 71%) per one gram of COD treatment. Results confirmed that the chemical coagulants could increase the POME treatment efficiency and reduce the specific energy consumption of EF. However, this method can be improved aiming at further reduction of COD by mineralizing the dissolved organic compounds to fulfill the POME discharge quality standards.

A Non-Hybrid Data-Driven Fuzzy Inference System for Coagulant Dosage in Drinking Water Treatment Plant: Machine-Learning for Accurate Real-Time Prediction

Coagulation is the most sensitive step in drinking water treatment. Underdosing may not yield the required water quality, whereas overdosing may result in higher costs and excess sludge. Traditionally, the coagulant dosage is set based on bath experiments performed manually, known as jar tests. Therefore, this test does not allow real-time dosing control, and its accuracy is subject to operator experience. Alternatively, solutions based on machine learning (ML) have been evaluated as computer-aided alternatives. Despite these advances, there is open debate on the most suitable ML method applied to the coagulation process, capable of the most highly accurate prediction. This study addresses this gap, where a comparative analysis between ML methods was performed. As a research hypothesis, a data-driven (D2) fuzzy inference system (FIS) should provide the best performance due to its ability to deal with uncertainties inherent to complex processes. Although ML methods have been widely investigated, only a few studies report hybrid neuro-fuzzy systems applied to coagulation. Thus, to the best of our knowledge, this is the first study thus far to address the accuracy of this non-hybrid data-driven FIS (D2FIS) for such an application. The D2FIS provided the smallest error (0.69 mg/L), overcoming the adaptive neuro-fuzzy inference system (1.09), cascade-correlation network (1.18), gene expression programming (1.15), polynomial neural network (1.20), probabilistic network (1.17), random forest (1.26), radial basis function network (1.28), stochastic gradient tree boost (1.25), and support vector machine (1.17). This finding points to the D2FIS as a promising alternative tool for accurate real-time coagulant dosage in drinking water treatment. In conclusion, the D2FIS can help WTPs to reduce operating costs, prevent errors associated with manual processes and operator experience, and standardize the efficacy with real-time and highly accurate predictions, and enhance safety for the water industry. Moreover, the evidence from this study can assist in filling the gap with the most suitable ML method and identifying a promising alternative for computer-aided coagulant dosing. For further advances, future studies should address the potential of the D2FIS for the control and optimization of other unit operations in drinking water treatment.

Reducing the pollution load of tannery wastewater and the atmospheric emission of hydrogen sulfide using modified tannin.

Industrial wastewater causes several environmental and health issues due to its composition, and hydrogen sulfide is one of the main contaminants from various industrial activities, including tannery wastewater treatment plants. This study aimed to evaluate the application of a modified tannin to remove hydrogen sulfide, chemical oxygen demand, total nitrogen, color, and turbidity from tannery wastewater and to reduce the atmospheric emission of sulfides. The wastewater was treated using modified tannin, aluminum sulfate, and a combination of both. Gaseous sulfide emissions were analyzed qualitatively using paper soaked in lead acetate. The qualitative methodology of hydrogen sulfide in the atmosphere was efficient to identify the most critical areas in the tannery. The wastewater treatment tests showed that the best option was the combination of both coagulants, in a 50:50 ratio, resulting in a total coagulant dosage of 3,000 mg/L. The removal efficiencies achieved were 13.8% sulfides, 23.3% chemical oxygen demand, 9.1% total nitrogen, 97.3% turbidity, and 96.4% color. This treatment technique promotes the replacement of 50% of the aluminum sulfate currently used in the tannery by a non-toxic coagulant and does not require chemicals to adjust the pH of the wastewater.

Is Electrocoagulation a Promising Technology for Algal Organic Matter Removal? Current Knowledge and Open Questions

AbstractElectrocoagulation (EC) is a practical alternative to chemical coagulation for the treatment of drinking water that contains various pollutants, including humic substances. Nevertheless, the performance of EC for removal of algal organic matter (AOM) is still largely unexplored. In this review, the properties of AOM, the principles of chemical coagulation and EC, and the current state of knowledge on the coagulation of AOM have been outlined. The limited available literature on the EC of AOM is critically reviewed and let conclude that this is a promising technology for AOM removal. However, the studies on EC are inconsistent in their approaches, and they lack thorough optimization of operating conditions (resultant pH, coagulant dosing) and reports of residual metal concentrations. Some of the identified needs for future research include the complete optimization of EC for AOM removal, its direct comparison with chemical coagulation, and EC testing for the elimination of mixtures of AOM, humic substances, and inorganic particles.

Performance, Modeling, and Cost Analysis of Chemical Coagulation-Assisted Solar Powered Electrocoagulation Treatment System for Pharmaceutical Wastewater

The combination of the chemical coagulation-assisted electrocoagulation (CC-EC) process with a solar photovoltaic energy source has attracted increasing attention for the efficient removal of chemical oxygen demand (COD) from pharmaceutical wastewater. In this paper, the CC-EC process has been utilized as an alternative to conventional chemical processes for the treatment of pharmaceutical wastewater. The effects of the various operating parameters, such as coagulant dosage, coagulant type, number of electrodes, the distance between electrodes, electrode configuration, operating time, and current density, on COD removal efficiency were investigated. The results indicated that the optimum conditions were achieved at 500 mg/L of alum dosage, 3.105 mA/cm2 of current density, six electrodes with a distance of 4 cm between electrodes, and the MP-S electrode configuration, where the operating cost of conventional energy was 0.283 $/m3. Indeed, by using the CC process alone, the COD removal efficiency was 26% and 61.5% at the optimal dosages of 750 mg/L of NaOH and 500 mg/L of alum, respectively. In the CC-EC treatment, the removal efficiencies of COD were 88.7, 92.9, 94.4, and 89.4% using six electrodes, 2 cm of distance between electrodes, MP-S electrode configuration, and 20 min with 1.553 mA/cm2 of current density, respectively. The removal efficiencies of COD achieved through CC, EC, and CC-EC processes were 61.5, 85.4, and 94.4%, respectively.