Surface water filtration using granular media and membranes: A review

Abstract

Significant growth of the human population is expected in the future. Hence, the pressure on the already scarce natural water resources is continuously increasing. This work is an overview of membrane and filtration methods for the removal of pollutants such as bacteria, viruses and heavy metals from surface water. Microfiltration/Ultrafiltration (MF/UF) can be highly effective in eliminating bacteria and/or act as pre-treatment before Nanofiltration/Reverse Osmosis (NF/RO) to reduce the possibility of fouling. However, MF/UF membranes are produced through relatively intensive procedures. Moreover, they can be modified with chemical additives to improve their performance. Therefore, MF/UF applicability in less developed countries can be limited. NF shows high removal capability of certain contaminants (e.g. pharmaceutically active compounds and ionic compounds). RO is necessary for desalination purposes in areas where sea water is used for drinking/sanitation. Nevertheless, NF/RO systems require pre-treatment of the influent, increased electrical supply and high level of technical expertise. Thus, they are often a highly costly addition for countries under development. Slow Sand Filtration (SSF) is a simple and easy-to-operate process for the retention of solids, microorganisms and heavy metals; land use is a limiting factor, though. Rapid Sand Filtration (RSF) is an alternative responding to the need for optimized land use. However, it requires prior and post treatment stages to prevent fouling. Especially after coating with metal-based additives, sand filtration can constitute an efficient and sustainable treatment option for developing countries. Granular activated carbon (GAC) adsorbs organic compounds that were not filtered in previous treatment stages. It can be used in conjunction with other methods (e.g. MF and SSF) to face pollution that results from potentially outdated water network (especially in less developed areas) and, hence, produce water of acceptable drinking quality. Future research can focus on the potential of GAC production from alternative sources (e.g. municipal waste). Given the high production/operation/maintenance cost of the NF/RO systems, more cost-effective but equally effective alternatives can be implemented: e.g. (electro)coagulation/flocculation followed by MF/UF, SSF before/after MF/UF, MF/UF before GAC.

Biofiltration technique for removal of waterborne pathogens

“…Removal of Giardia cysts and Cryptosporidium oocysts was shown to be affected by extent of filter maturation and application of coagulant chemicals. Treatment of coagulated primary effluent through RSF demonstrated approximately 1 log unit decrease in fecal coliform, pathogenic bacteria (Salmonella and Pseudomonas aeruginosa) and enteroviruses, 50%e80% of protozoan (Giardia and Entamoeba histolytica) cysts, and 90%e99% of helminth ova (Adelman et al, 2012;Hoslett et al, 2018;Jiménez et al, 2009).…”

Modeling and design optimization for pleated membrane filters

“…At the most basic level, membrane filtration is a process of separation, whereby undesired/desired particles are removed from a fluid suspension (known as a feed) by passing through a porous membrane. Membrane filters are commonly used in many applications and feature in many aspects of daily life, such as drinking water production [1], beer purification [2], vaccine purification [3], food and dietary supplement production [4], natural gas purification [5] and many more. With growing interest from both industrial and academic sectors in understanding the various types of filtration processes in use, and improving filter performance, the past few decades have seen many publications in this area, including excellent review articles that cover various aspects of membrane filtration (see, for example, [6][7][8][9]).…”

Facile preparation of a crosslinked hydrophilic UHMWPE membrane

“…Microporous filters are widely used in filtration and separation applications, such as water purification, drug concentration, and food products . Ultra high molecular weight polyethylene (UHMWPE), with its wide range of excellent characteristics, that is, mechanical properties, high chemical stability, nontoxicity, is an ideal material for filter fabrication …”