China
Africa
Explore chapters and articles related to this topic
Introduction to Wastewater
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Flocculation is the process by which the coagulated particulates are clumped together in a floc, which will generally float to the top of the liquid or settle down at the bottom of the liquid to be filtered out. Flocculants are substances that promote agglomeration of fine particles present in water, creating a floc, which either floats or settles down and can be easily removed from the liquid. Flocculants counterbalance the charge of the particles, adsorb on the particles, and cause destabilization by bridging and/or charge neutralization. In water treatment, flocculation is the phase of formation of large flocs by the addition of a secondary chemical (after the addition of the coagulant) called a flocculent. Nowadays polymeric flocculants are widely used. The polymeric material forms bridges between individual particles. Bridging occurs when segments of a polymer chain adsorb on different particles and help the particles agglomerate into larger particles. This can largely flocculate the particles with a very small amount of flocculant.
Water Systems/Saving Our Valuable Resource
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
Most city water systems achieve purification by the filtration method. Water from the primary source is pumped or forced into a chemical building or area for the first phase of the purification process. Water arriving in this area is mixed with prescribed quantities of lime, activated carbon, alum, and chlorine. From this area the mixture then passes into a coagulation basin, where it is thoroughly mixed. A coagulant is a specific type of chemical that forms a small fluffy mass when placed in water. Aluminum sulfate or fiber alum is a common chemical used as a coagulant. The fluffy mass formed by this action is called floc. Floc particles are used to remove foreign material suspended in the water by adhering to it. Floc and other suspended material settle to the bottom of a basin after a short period of time. This action is representative of the coagulation and sedimentation function of the purification process.
Advanced or Tertiary Treatment
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
Don E. Burns, George J. Crits, Donald Dahlstrom, Stacy L. Daniels, Bernardo Rico-Ortega, Chakra J. Santhanam, E. Stuart Savage, Frank P. Sebastian, Gerald L. Shell, Paul L. Stavenger
A coagulation system has the following functions: Preparation of solutions of coagulants, flocculants, and coagulant aids. Usually employed are alum, ferric chloride, or other inorganic coagulants; cationic polyelec-trolyte flocculants; or anionic or nonionic polyelec-trolyte flocculants.Rapid mixing of coagulants with wastewater.Growth of floc to produce large agglomerates under gentle mixing conditions.Separation of floc from water, usually by settling or flotation.
Valorization of conventional rice starch in drinking water treatment and optimization using response surface methodology (RSM)
Published in Chemical Engineering Communications, 2021
Siong-Chin Chua, Fai-Kait Chong, Chia-Heng Yen, Yeek-Chia Ho
Figure 7a showed the three-dimensional response surface for turbidity reduction in the function of pH and dosage of starch in 3.3 min of settling time. High turbidity reduction (represent by red color) is achieved at dosage of starch range from 34.3 to 40 mg/L and at pH 3–3.5. This is attribute to the high concentration of H+ in low pH water that helps to form hydrophobic interactions in the bridging mechanism. The hydrophobic interactions promote the surface attachment of the particles through the reduction of electrostatic repulsion between particles. Hence, more particles are linked and bonded together to form microfloc. The dosage of starch further helps in bridging and absorption of microfloc. The particles are absorbed onto the starch chains through chemical bonding and physical attachment. The starch polymers simultaneously bind to the surface of the particles to form a bridge between particles. As a result, particles are bridged together to form floc and the process is known as flocculation. However, low concentration of H + in water (pH around 6.5) reduces the efficiency of the starch due to insufficient of hydrophobic interactions which can be observed in Figure 7a where maximum turbidity reduction in pH 6.5 was approximately 63%.
Determination of suspended sediments particle size distribution using image capturing method
Published in Marine Georesources & Geotechnology, 2018
Sivakumar Ramalingam, Venu Chandra
Generally, noncohesive sediments deposit due to their self-weight, but cohesive sediments deposit after forming flocs (Einstein and Krone 1961; Mehta and Partheniades 1975). The process of floc formation depends on both sediment and flow characteristics (Krone 1986; Mehta 1989; Eisma et al. 1990). The SCS can flocculate in the form of cluster or like a chain (Partheniades 1965), and floc density influences suspended sediment settling process (Gibbs 1985; Hayter and Mehta 1986; Manning and Schoellhamer 2013). Temporal variation of SCS concentration (Mehta 1989; Dyer and Manning 1999; Chandra et al. 2010; Chandra, Mohapatra, and Nestmann 2012) or particle size distribution (PSD) (Lau and Krishnappan 1992; Winterwerp 2002) is used to estimate sediment settling velocity. Further, the floc size distribution (FSD) data help to improve performance of numerical models and also to manage aquatic ecosystem (Klassen et al. 2013). Similar kinds of instruments are used to analyze PSD and FSD of suspended sediments. Conventionally used hydrometer test provides only PSD of fine suspended sediments, but it is unable to provide FSD. Modern instruments that work either laser-based or image-processing method for FSD determination are discussed below.
Reduction of sedimentation and water turbidity at intakes of drinking water treatment plants
Published in Water Science, 2023
W.A. Fahmy, MOHAMED A. E. Halawa, NASR T. H. Hekal
Jar test is the most widely used experimental method/procedure for simulating coagulation-flocculation with differing chemical doses (Asrafuzzaman, Fakhruddin, & Alamgir Hossain, 2011). According to (WATER.MECC, 2022), Coagulation/flocculation is defined as the process of binding small particles in the water together into larger, heavier clumps which settle out relatively quickly. The larger particles are known as floc. Properly formed floc settle out of water quickly in the sedimentation basin, removing the majority of water turbidity.