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Physical Processes in Wastewater Treatment
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Ning Zhang, Ankur Dwivedi, Amita Chaudhary
Coagulation is the process of using chemical and/or physical techniques to promote particulate settling by reducing net electrical repulsion forces between particles. Coagulation is the process by which colloidal particles and very fine suspended solid particles present in wastewater are combined into larger agglomerates that can be separated via flocculation, sedimentation, filtration, centrifugation, or other gravity-based separation methods. Coagulation is commonly achieved by adding different types of chemicals (coagulants) to the wastewater to promote the destabilization of the colloid dispersion and agglomeration of the resulting individual colloidal particles. The main coagulants are Al2(SO4)3, NaAlO2, FeSO4, and other coagulants, such as polyelectrolytes, can also be used. Coagulation requires the rapid dispersion of the coagulants throughout the wastewater through rapid agitation (Teh et al., 2016).
Controlling cyanotoxin occurrence
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Gayle Newcombe, Lionel Ho, José Capelo Neto
Conventional treatment generally comprises coagulation and flocculation, followed by clarification and rapid media filtration. Coagulation and flocculation are processes that aggregate suspended particles through the addition of a chemical coagulant. Common coagulants used in water treatment include various aluminium and ferric salts, synthetic organic polymers or a combination of inorganic and organic coagulants. In the clarification step, the coagulated particles, or flocs, are separated from the water by processes such as sedimentation, dissolved air flotation (DAF) or upflow clarification processes. Two common alternatives to the full conventional process are direct filtration, where there is no clarification step, and contact filtration, where the flocculation and clarification steps are eliminated. While the coagulation process is ineffective for the removal of extracellular (dissolved) cyanotoxins, it is very effective in removing cell-bound cyanotoxins through the removal of the whole cyanobacterial cell (Drikas et al., 2001; Henderson et al., 2008; Newcombe et al., 2015).
Water Chemistry
Published in Frank R. Spellman, The Science of Water, 2020
Chemical coagulation is usually accomplished by the addition of metallic salts such as aluminum sulfate (alum) or ferric chloride. Alum is the most commonly used coagulant in water treatment and is most effective between pH ranges of 5.0 and 7.5. Sometimes polymer is added to alum to help form small floc together for faster settling. Ferric chloride, effective down to a pH of 4.5, is sometimes used.
Application of cascade feed forward neural network to predict coagulant dose
Published in Journal of Applied Water Engineering and Research, 2022
Dnyaneshwar Vasant Wadkar, Rahul Subhash Karale, Manoj Pandurang Wagh
Coagulation is an essential process of water treatment. Determination of optimal coagulant dose is vital, as insufficient dosing will result in a high-value of turbidity in treated water (Zhang et al., 2013). On the other hand, doses that are too high can result in high cost and health problems related to high levels of residual aluminum (if alum is used as the coagulant). Thus, the turbidity of water is an assessment parameter for the coagulation process. Coagulant–turbidity dataset is used for the prediction of optimum coagulant dose in WTP. This dataset has 11688 data points (1 January 2012 – 31 December 2015) which include eight readings per day at an interval of three hours namely inlet water turbidity, outlet water turbidity, and coagulant dose. As we know determination of coagulant dose in the laboratory requires nearly three hours, the inlet water turbidity, outlet water turbidity, and coagulant dose observed at the interval of three hours were collected.
Removal of antibiotic resistance genes (ARGs) in various wastewater treatment processes: An overview
Published in Critical Reviews in Environmental Science and Technology, 2022
Coagulation has been commonly applied in wastewater and water treatment plants to improve water quality and remove the suspended particles as well as pollutants (Li et al., 2017; Sillanpaa et al., 2018). In the process of coagulation, the repulsive potential of the colloidal double electrical layer was reduced under the action of coagulants, leading to the aggregation and destabilization of the colloids as well as suspended solids in raw water. After that, the solid-liquid separation of large flocs occurred under the action of gravity, and further removed during sedimentation process. Chemical coagulants, such as ferric-based coagulants, and aluminum-based coagulants, are commonly used in the coagulation process due to their wide range of pH and temperature applicability. The application of coagulation process in the removal of ARGs from wastewater was shown in Table 9.
Integration of coagulation-flocculation and heterogeneous photocatalysis for the treatment of pulp and paper mill effluent
Published in Environmental Technology, 2022
Deepthi John, Suguna Yesodharan, V. Sivanandan Achari
PPME is not much biodegradable with high values of BOD and COD. Its biodegradability index (ratio of BOD to COD) is usually between 0.02 and 0.07 [3]. It has been reported by Chamarro et al. [4] that the biodegradability index of the effluent should be at least 0.40 for complete degradation. Therefore a primary clarification which targets an appreciable decrease of BOD and COD is an essential prerequisite before any subsequent treatments. In this respect coagulation – flocculation is an effective method due to its methodical simplicity and economic effectiveness. It is a widely used process, alone or in combination with other methods, for the treatment of PPME. It involves the use of a metal ion as a coagulating agent which when dissolved in water hydrolyses to form many hydrophobic monomeric and polymeric hydroxide species with different charges based on the pH of the solution. These hydroxides interact with the colloidal particles causing them to either get adsorbed or neutralised leading to coagulation-flocculation and finally sedimentation [5]. The effectiveness of the coagulation process depends on various factors such as the type and concentration of coagulants used, pH of the medium, ionic strength as well as the nature and concentration of the organic residues present in the effluent.