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Harvesting chlorella sp by electrocoagulation
Published in Yuli Rahmawati, Peter Charles Taylor, Empowering Science and Mathematics for Global Competitiveness, 2019
Various methods have been developed in order to get pure chlorella sp, such as centrifugation, sedimentation, filtration and flocculation (Matos et al., 2013). All of these methods require a large amount of electrical energy. For centrifugation, electrical energy of 8 kWh / m3 is required (Danquah et al., 2009), while filtration techniques only require 0.4 kWh/m3, although this type of technique increases operational costs because the screen filters need to be replaced periodically (Uduman et al., 2010). Meanwhile, flocculation requires a coagulant that is expensive, but its energy needs are few (Uduman et al., 2010). The most commonly used flocculants include cationic polymer flocculant (Wang et al., 2014), polyaluminum chloride, ferric chloride, aluminum chloride (Lam et al., 2015), chitosan (Delrue et al., 2015), nano chitosan particles, (Farid et al., 2013), nanomagnetite (Chun et al., 2016), and Moringa oleifera fruits (Hamid et al., 2016).
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
The choice of a specific flocculant depends on the characteristics of the process system to be flocculated. The density of the suspending liquid (usually water) and the effective density of the suspended particles must be sufficiently different to permit separation. Sand and grit particles are heavy and compact. They can have effective densities more than twice that of water. Biological solids and hydrated inorganic precipitates are hydrophilic, i.e., associated with surface-bound and internally contained water. Their densities can be only slightly greater than that of water. The density of water is affected slightly by temperature and more significantly by salt content.
Nano-Based Wastewater Treatment Technology
Published in M. H. Fulekar, Bhawana Pathak, Environmental Nanotechnology, 2017
A second process after coagulation is called flocculation. Flocculation involves a gentle mixing, increases the particle size from sub-microscopic microfloc to visible suspended particles (Exall, 2005). Flocculation promotes the aggregation and flocs formation, usually after the addition of an appropriate flocculant agent. Two general types of flocculation can be identified: micro-flocculation (or perikinetic flocculation), in which particles aggregation is brought about by the thermal motion of fluid molecules (Brownian motion) and macro-flocculation (orthokinetic flocculation), in which particle aggregation is brought about by inducing velocity gradients and mixing in the suspension (Tzoupanos and Zouboulis, 2008). The microflocs are brought into contact with each other through the process of slow mixing. Collisions of the microfloc particles cause them to bond to produce larger, visible flocs called pinflocs. The floc size continues to build with additional collisions and interaction with added inorganic polymers (coagulant) or organic polymers (Prakash et al., 2008). Macroflocs are formed. High-molecular-weight polymers, called coagulant aids, may be added during this step to help bridge, bind and strengthen the floc, add weight and increase settling rate. Once the floc has reached its optimum size and strength, water is ready for the sedimentation process. Design contact times for flocculation range from 15 or 20 min to an hour or more. In mineral processing industries, the scope of application of flocculants is much greater than the coagulants. Flocculants are widely used in the processing of coal, bauxite, phosphate, potash sand, gravel, cement, soda ash, copper, silver, gold, beryllium, lead and zinc (Tripathy and De, 2006).
Flocculant effects on fluidity and strength behavior of cemented dredged clay with high water content
Published in Marine Georesources & Geotechnology, 2021
Gui-Zhong Xu, Cheng-Chun Qiu, Miao-Miao Song, Yu-Peng Cao, Jie- Yin
In practical engineering, two types of soil-cement mixing methods are commonly adopted. One is the biaxial mixing method (BMM) (Miyazaki et al. 2003), and the other is the pipe mixing method (PMM) (Kitazume and Satoh 2003). It has been demonstrated that the unconfined compressive strength is the primary quality control index for BMM, and the main project quality control indicators for PMM are the unconfined compressive strength and the fluidity (Wu et al. 2018). Hence, it is essential to study the flocculant effects on the fluidity and strength behavior of solidified dredged clay for their engineering application. To this end, a series of flow tests and unconfined compressive strength (UCS) tests were conducted on the cement-treated dredged clay with and without flocculant. Five flocculants were adopted to investigate the impacts of flocculant type, including FeCl3, cationic polyacrylamide (CPAM), nonionic polyacrylamide (NPAM), anionic polyacrylamide (APAM) and Chitosan. The fluidity of dredged clay and cemented dredged clay with and without flocculant is investigated, and the working mechanisms controlling the changes in the fluidity due to the addition of flocculant are discussed. Then, the flocculant effects on the unconfined compressive strength (qu) of cemented clay are studied. Combined with the fluidity, the mechanisms responsible for the alteration in the strength are explored. Finally, the appropriate dosages for different flocculants are also investigated according to the target fluidity and the qu for practical engineering.
Enhanced efficiency of swine wastewater treatment by the composite of modified zeolite and a bioflocculant enriched from biological sludge
Published in Environmental Technology, 2018
Junyuan Guo, Jiali Du, Peilan Chen, Xinyi Huang, Qingyang Chen
For the removal of suspended particles and organic matters from wastewaters, the flocculation technique had been the most effective process [9], in which flocculants played key roles, and now, an environment-friendly flocculant, named ‘bioflocculant’, was increasingly attracting widespread academic attention. The biggest obstacle for the production and application of the bioflocculant was the high costs associated with purchasing substrates for strains’ cultivation in laboratory scale [10]. As is known to all, a large quantity of swine wastewater from the extensive swine breeding in China contains high levels of ammonia and organics, which can be used to cultivate strains, and further to extract bioflocculant from the strains’ metabolites. In this case, utilization of a bioflocculant from swine wastewater to treat swine wastewater not only can reduce pollution, but can also help us utilize the waste-water resources.
A Review on Floc-Flotation of Fine Particles: Technological Aspects, Mechanisms, and Future Perspectives
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Kaveh Asgari, Hamid Khoshdast, Fardis Nakhaei, Mohammad Reza Garmsiri, Qingqing Huang, Ahmad Hassanzadeh
Some other researchers have proposed the charge neutralization mechanism. The principles of this mechanism are based on the opposite charge of the flocculant and suspended particles, and flocculation takes place because of the destabilization of colloid particles via adding water-soluble polymer. In the case of effective flocculation, the ionic strength is incremented, besides, the surface charge will be neutralized via compression of double layer (Rose and John 2011; Tridib et al. 2006). Some other researchers announced that the main reason for adsorption is Van der Waals and electrostatic force, as well as hydrogen and chemical bonding (Singh et al. 2003; Somasundaran and Runkana 2000).