China
Africa
Explore chapters and articles related to this topic
Clarification of Fruit Juices and Wine Using Membrane Processing Techniques
Published in M. Selvamuthukumaran, Applications of Membrane Technology for Food Processing Industries, 2020
Membrane fouling and concentration polarisation are one of the main problems of membrane processing. Membrane fouling is defined as the alteration in membrane properties because of the interaction of the feed stream and membrane (Mohammad et al. 2012). Four different types of membrane fouling were identified in the literature, namely complete blocking, intermediate blocking, standard blocking and cake filtration (Figure 5.2). When large particles are present in the feed stream generally complete or intermediate blocking occurs. Large particles get trapped on the surface of the membrane and block the pores in both cases. In intermediate blocking other particles were held up by the particles that block the pores (Iritani and Katagiri 2016). In standard blocking, particles smaller than the pores are held up by the internal walls of the membrane and pore volume gradually decreases during filtration (Amosa 2017). Cake formation is the formation of filter cake outside of the membrane surface without blocking the pores (Wang and Tarabara 2008).
Towards Energy-Efficient Reverse Osmosis
Published in Andreas Sapalidis, Membrane Desalination, 2020
Mohamed T. Mito, Philip Davies
Membrane fouling, the build-up of substances on the membrane surface, has a direct effect on membrane performance and energy requirements. Membrane fouling can be identified as scaling resulting from the accumulation of precipitated salts; biological fouling resulting from admission and growth of microorganisms that form an adherent biofilm; and organic fouling resulting from adsorption of dissolved organic matter. Excessive membrane fouling affects permeability and salt rejection, which, in turn, has a direct effect on the energy requirement owing to the necessity of higher pressure to maintain the same water flux. Moreover, membrane fouling leads to the need for excessive chemical cleaning, shortening the membrane life, and increasing running cost. Factors that affect membrane fouling are feed water quality, operation parameters (i.e., flux and pressure) and membrane surface properties. As feed water quality is site dependent and could be improved by pretreatment processes, current research is focused on developing membrane materials with low fouling propensity to minimize the effect of fouling on energy consumption. Propensity to fouling can be reduced by increasing the membrane surface hydrophilicity, using smoother membrane surfaces, and introducing strong electrostatic repulsion between membrane surface and charged foulants. RO membranes with smooth, hydrophilic surfaces have shown resistance to biofouling and biofilm formation, leading to lower energy requirements and requiring less frequent chemical cleaning (Goh et al., 2016).
Application of ATP and BGP methods to monitor media filtration and dissolved air flotation pre-treatment systems
Published in Almotasembellah Mustafa Jawdat Abushaban, Assessing Bacterial Growth Potential in Seawater Reverse Osmosis Pretreatment: Method Development and Applications, 2019
Almotasembellah Mustafa Jawdat Abushaban
The key operational challenge that seawater reverse osmosis (SWRO) systems face during operation is membrane fouling (Matin et al. 2011, Goh et al. 2018). Membrane fouling reduces membrane permeability; permeate quality and leads to higher operating pressures. Membrane fouling can be due to suspended and colloidal particles, organic matter, dissolved nutrients and sparingly soluble salts. One or more types of fouling can occur depending on feed water quality, operating conditions and type of membrane (She et al. 2016). To mitigate fouling in SWRO systems, pre-treatment is commonly applied (Henthorne and Boysen 2015). Pre-treatment improves the quality of SWRO feed and increases the efficiency and life expectancy of the membrane elements by minimizing fouling, scaling and degradation of the membrane (Dietz and Kulinkina 2009).
Challenges and potentials of forward osmosis process in the treatment of wastewater
Published in Critical Reviews in Environmental Science and Technology, 2020
Ibrar Ibrar, Ali Altaee, John L. Zhou, Osamah Naji, Daoud Khanafer
In-situ and real-time fouling monitoring is a hot spot for FO research, and it can give us an insight into fouling layer formation and the severity of fouling on the membrane, and thus correspondingly conduct timely cleaning. Fouling in the forward osmosis is usually evaluated through monitoring water flux decline, which generally occurs due to membrane fouling. Amongst the various technologies for monitoring real-time fouling, the simplest one is confocal laser scanning microscopy (CLSM) in combination with multiple fluorescence labeling. This technique gives insight into the structure, distribution, and function of biofilm constituents at a microscale (0.5–1.5 μm) (Yun et al., 2006). Yuan, Wang, Tang, Li, and Yu (2015) used this technique to investigate the biofouling mechanism in OMBR. This study revealed that EPS plays a major role in the formation of biofouling layer and extending the operating time of OMBR leads to a reduction in the growth of microorganisms as well as easy detachment from the fouling layer. Though it is a useful technique, CLSM has several drawbacks such as photo-bleaching can kill some living organisms on the biofilm, the monochromatic laser beam can be harmful, and it can be costly as well.
Static turbulence promoters in cross-flow membrane filtration: a review
Published in Chemical Engineering Communications, 2020
Chiranjit Bhattacharjee, V. K. Saxena, Suman Dutta
Among the above, the main problem limiting the widespread applicability of membrane-based techniques in process industries is the phenomenon called membrane fouling. Deposition of macromolecules, suspended solids, colloids, or biological suspensions on membrane surface and blocking of pores are the main reasons of membrane fouling. The main impact of membrane fouling is on the permeate flux which reduces drastically with time. The depositions form a polarized layer over the membrane surface and the process is known as concentration polarization. Concentration polarization is reversible to a certain extent but the blocking of pores is in most cases irreversible. Due to this concentration polarization, a cake layer with high concentration is generated which then acts as a secondary membrane. The extent of this phenomenon depends on the type of feed being used, the pore size of the membrane, membrane properties, operating parameters of the process, etc. Researchers have tried various techniques to reduce pore blocking and concentration polarization. Altering the module hydrodynamics is one of the ways that can effectively tackle this polarization phenomenon. Some of the most tried methods for changing system hydrodynamics are use of rotational or vibratory modules, incorporation of turbulence promoters, etc. In this paper, we will review the use of turbulence promoters in membrane process in recent times.
Performance of a new ceramic microfiltration membrane based on kaolin in textile industry wastewater treatment
Published in Chemical Engineering Communications, 2019
Priyanka Saini, Vijaya Kumar Bulasara, Akepati S. Reddy
In comparison with organic membranes, ceramic membranes have several benefits such as ease of cleaning and regeneration, high mechanical strength, thermal stability, corrosion resistance and less degree of fouling (Hofs et al., 2011; Kaur et al., 2016a). Also, ceramic membranes can be applied in large scale treatment as polymeric membranes proved inadequate for industrial applications due to their short life span (Jedidi et al., 2011; Singh and Bulasara, 2015). Therefore, several researchers are focusing on the development of low cost ceramic membranes from cheaper and abundant natural materials such as clay and waste substances such as fly ash (Jedidi et al., 2011; Fang et al., 2011; Rawat and Bulasara, 2018). Lee and Cho (2004) showed that a tight-UF range ceramic membrane behaves in a way similar to that of a nanofiltration (NF) range polymeric membrane. The authors also concluded that an equivalent ceramic membrane exhibits good retention of organics and higher permeability in terms of natural organic matter removal. Presently, ceramic membranes are successfully implemented in desalination processes, chemical, metal, textile, food, and beverage industries (Barredo-Damas et al., 2010; Barredo-Damas et al., 2012). However, a major limitation of membrane processes is flux decline due to membrane fouling (Fersi et al., 2009). Membrane fouling can be overcome by using feed specific pretreatment process prior to membrane treatment (Marcucci et al., 2003).