International Journal of Engineering Advanced Research eISSN: 2710-7167 [Vol. 3 No. 3 December 2021]
Journal website: http://myjms.mohe.gov.my/index.php/ijear
A REVIEW OF REMOVING ESCHERICHIA COLI GROWTH IN RIVER WATER BY USING RIVER BANK FILTRATION
(RBF)
Rhahimi Jamil1*, Rossitah Selamat2, Husaini Aza Mohd Adam3, Azhani Ariffin4 and Zarina Syuhaida Shaarani5
1 2 4 5 Civil Engineering Department, Politeknik Tuanku Sultanah Bahiyah, Kulim, Kedah, MALAYSIA
3 Kolej Komuniti Seberang Jaya, Permatang Pauh, Pulau Pinang, MALAYSIA
*Corresponding author: [email protected]
Article Information:
Article history:
Received date : 21 October 2021 Revised date : 10 November 2021 Accepted date : 3 December 2021 Published date : 8 December 2021
To cite this document:
Jamil, R., Selamat, R., Mohd Adam, H., Ariffin, A & Shaarani, Z. (2021). A REVIEW OF REMOVING
ESCHERICHIA COLI GROWTH IN RIVER WATER BY USING RIVER BANK FILTRATION (RBF).
International Journal of Engineering Advanced Research, 3(3), 38-53.
Abstract: An increase of pathogenic bacteria (E. coli) in river water is a concern as it is the main precursor to health hazard disinfection in conventional drinking water treatment systems. One possibility of growing interest in water utilities is the technology of riverbank filtration (RBF). RBF is a new method that could introduce non- chemical techniques and natural treatments in Malaysia.
Although RBF systems are efficient in reducing or removing the concentrations of contaminants, they are mostly ineffective in the removal of pathogenic bacteria especially during flood and wet seasons. Therefore, this review aimed to remove Escherichia coli (E. coli), and reduce the concentration with low-frequency electromagnetic fields (LF-EMF) as a component of the non-ionising radiations in RBF. The presence of E.coli bacteria in natural and treated waters serves as a pathogenic microorganism indicator for water pollution.
In this instance, the geometric mean of the indicated E. coli density should not exceed 126 CFU/100 mL of water. RBF and SSF systems are also examples of effective water treatment processes to remove E. coli by means of compounds undergoing natural filtration process through aquifers. The specific research on RBF was reviewed by water quality based on categories and summaries of the objectives, and the major findings. From this review, most of the methods focused on the determination of water quality in bank filtrates to improve the quality of the
1. Introduction
Malaysia is rich with groundwater as a freshwater source apart from surface water supply, and its demand has been projected to increase by 63% from 2000 to 2050 (Manap et al., 2013). In Malaysia, groundwater is in severe demand where surface water supply is non-existent and inadequate. However, groundwater has only become a highly-sought water source in the recent years because the quality of river water is continually deteriorating while water demand is expected to increase (Shamsuddin et al., 2014). Moreover, low surface water levels at the point of intake during the dry season could prevent water from being pumped to water treatment plants, and consequently stop the supply of clean water to millions of people. One of the groundwater abstraction techniques that has proven be effective in preserving groundwater and treating polluted river water for drinking purposes is the riverbank filtration (RBF) system (Bauer et al., 2011). RBF has long been recognised as a natural method for surface water treatment (Shamrukh and Wahab, 2008). It is an efficient and low-cost alternative of water treatment for drinking water. During infiltration and underground transport, the processes of filtration, biodegradation, and sorption are significant to improve raw water quality (Partinoudi and Collins, 2007). The RBF system is interesting because it can control and remove contaminants from surface water using low-cost treatment technology (Buzek et al., 2012; Adlan et al., 2016; Hu et al., 2016). It is also an effective method of removing pathogenic bacteria and viruses during the infiltration of surface water (Won et al., 2007; Diem et al., 2013; Hu et al., 2016; Wang et al.,2015). Nonetheless, this method is sensitive to the surrounding activities on the ground, aquifer layer properties, and the physical characteristics of the river water (Kuehn and Mueller, 2000). As a result, the removal efficiency of microbial contaminants at different locations are varied, with less than 2.1 logs removal for E.
coli, and more than3.2 logs removal of viruses (Weiss et al., 2005). Nevertheless, E.coli and other bacteria were still observed in RBF or groundwater wells (Tufenkji et al., 2002; Dash et al., 2010;
Cady et al., 2013; Gutierrez et al., 2017). Therefore, some improvements or enhancements with other treatment techniques can increase RBF efficiency.
surface water. Majority of the RBF systems used in European countries and America alike have achieved excellent total coliform removal percentages, ranging from 99.2% to 99.99% (2.1 to 5 logs). It was also observed that 25 to 87% of groundwater can be co-extracted from these RBF wells. According to this review, the obtained results revealed the efficiency of the RBF system in eliminating bacteria mainly at the water-media interface. Therefore, it is advisable for the RBF system to be considered as a pre- treatment method to be combined with more effective conventional disinfection technologies in order to meet the target.
Keywords: Drinking water, E. coli, RBF, banks filtration.
2. Literature Review
Drinking water pollution can be divided into different types, such as organic substances, toxic substances, thermal pollution, and ecological pollution (Maeng et al., 2011; Cucurachi et al., 2013), which are illustrated in Figure 2.1.
Figure 2.1: Types of Drinking Water Pollution
Drinking water polluted by microorganisms of faecal origin is a current worldwide health concern because of epidemic occurrences globally in relation to microbial-contaminated water. In drinking water, these microorganisms of interest include protozoa, bacteria, viruses, algae, and helminths.
An overview of these microorganisms is given in Table 2.2.
Table 2.2: Microorganism in Drinking Water Sources; Modified From (Crittenden et al., 2012; Ibrahim 2018)
Microorganisms with a range of 1 to 10 μm in particle size are harder to remove by conventional treatment systems, and unfortunately, most of the microorganisms of concern in drinking water fall within this diameter range (Crittenden et al., 2012). These microbiological particles have a consequence on surface effect, which is sediments, and this causes the anionic filter media to become ineffective in removing the particles without repulsion by means of coagulation (Ibrahim, 2018). Additionally, motile microorganisms are harder to remove without prior deactivation by disinfectants. As a measure of the degree of contamination in samples of water, or the degree of the infection in humans and animals, the term ‘CFU’ (colony-forming units) is used, referring to the number of living bacterial cells.
2.1 Escherichia Coli
Escherichia coli or E. coli is also known as a facultative anaerobic bacterium that is gram-negative.
Cells of E. coli are typically rod-shaped with a cell volume of 0.6 to 0.7 μm3, 2 μm long, and 0.5 μm in diameter (Odonkor and Ampofo, 2013). Generally, E. coli is found in the faeces of healthy cattle, and is transmitted in the lower intestinal tracts of warm-blooded organisms, including humans and animals (Ishii et. al, 2006). In 1885, this microorganism was discovered by Theodor Escherich, and was first classified as a human pathogen in 1982 (Lim et al., 2010; Mead and Griffin, 2010). Most of the E. coli strains harmlessly colonise the gastrointestinal tracts of humans and animals as normal flora. However, other strains grow into pathogenic E. coli by acquiring virulence, which is caused by bacteriophages, plasmids, transposons, and pathogenicity islands.
Differences in survivability, external structure, size, shape, and zeta potential are some of the factors that influence the behaviour of these bacteria. This pathogenic E. coli can be categorised based on pathogenicity mechanisms, serotypes, clinical symptoms, or virulence factors (Nataro and Mobley, 2004; Guionet et al., 2015). Several of the enterohaemorrhagic E. coli are defined as pathogenic bacteria that produce Shiga toxins, and cause the life-threatening sequelae of haemolytic uraemic syndrome, and haemorrhagic colitis in humans (Mayer et al., 2012; Shamsul et al., 2016). An illustration of the E. coli bacteria is in Figure 2.2.
Figure 2.2: Scanning Electron Micrograph of E. coli Isolated from River Water.
Sources from; (http://www.bacteriainphotos.com/bacterial-biofilm.html#)
3. Method
Generally, water treatment methods can be categorised mainly into conventional and non- conventional methods. Unit treatment processes for conventional methods are coagulation, flocculation, sedimentation, filtration, and disinfection, while non-conventional methods use more sophisticated equipment. Majority of the water treatment plants in Malaysia operate based on the conventional treatment system for water supply (Soh and Abdullah, 2007). Through this system, E. coli is reduced by oxidation through pre-chlorination and/or the aeration process. These processes are most important to remove the contamination in raw water. Chlorination is the most common and applicable practice for the deactivation of microorganisms, and is also reasonably cheap (Umar et al., 2011). The finished water is usually chlorinated at levels between 2 and 3 mg/L to ensure free residual chlorine of not less than 0.2 mg/L throughout the distribution system (MOH, 2000). Chlorination should meet the level of 0.4 to 0.5 mg/L of free chlorine; however, one limitation of chlorination is that some parasitic species have shown resistance to low doses of chlorine (Li et al., 2010). Generally, chlorination is the most widely used disinfection process.
However, the disinfection by-products made from chlorination are carcinogenic and mutagenic to human health (Nan et al., 2010; Yang and Cheng, 2007; Lu et al., 2009; Coleman et al., 2005). A disadvantage of chlorine is its ability to react with natural organic matter to produce other halogenated disinfection by-products (WHO, 2006). However, by product formation may be controlled by the optimisation of the treatment system. This issue is addressed around the world through different water treatments to destroy or remove pathogenic bacteria. For the past few decades, several treatment methods have been developed and enhanced to remove E. coli, and minimise disinfection by-product formation potential in the drinking water system. In addition to the typically practiced treatment process, new technologies were incorporated into the system to efficiently remove E. coli. Examples of several treatment methods are highlighted in Table 3.
Table 3: Summary of Several Proposed Treatment Methods Suggested for E. coli Removal
Based on this overview, many water treatment methods have been developed to remove E. coli in water, such as titanium dioxide (TiO2) photocatalysis, slow sand filtration (SSF), silver nanoparticle adsorption, riverbank filtration (RBF), granulated activated carbon (GAC), ozonation system, ultraviolet (UV) irradiation, and biosolids on grassland. These systems are examples of the technologies that have been applied in drinking water treatment facilities. In the case where raw water contains too high or too low concentrations of E. coli, titanium dioxide photocatalysis becomes less effective; thus, further treatment such as UV irradiation and GAC filters are required to efficiently remove the E. coli remaining in the water prior to the disinfection process. RBF and SSF systems are also examples of effective water treatment processes to remove E. coli by means of compounds undergoing natural filtration process through aquifers.
3.1 Riverbank Filtration (RBF)
Subsurface or groundwater in Malaysia are natural water sources that can be exploited to meet the demands for water of high quality. The RBF process is an existing method referring to the process of extracting potable water at the riverbank, utilising subsurface or groundwater to supply sources of high-quality water (Mustafa et al., 2016; Hu et al., 2016). RBF systems and natural treatment processes typically take place during water infiltration. Figure 3 shows the natural process of extracting treated water from an adjacent pumping well to a river.
Figure 3: Schematic Diagram of Mechanisms in Natural Filtration by RBF System (Hiscock & Grischek, 2002)
As illustrated in the figure above, the difference in hydraulic gradient causes the water from the river to flow towards the well during the pumping process (Worch et al., 2002; Boving et al., 2014). Additionally, the RBF process is known as a sustainable and economical method to improve poor surface water quality (Sandhu et al., 2011; Umar et al., 2017). A complex attenuation method occurs during the transportation of water through the aquifer layer, resulting in raw water of high quality. The high-quality raw water is then supplied to the water treatment plants, making it easier to be treated at low operating costs by conventional treatment systems (Partinoudi and Collins,
2007). Therefore, water from the well can be directly consumed with very minimum treatment in certain areas.
3.1.1 Samples
Describe how the data was collected or generated and, how was it analysed. Clearly state whether there is a population that you would ideally want to generalize to; explain the characteristics of that population.
3.1.2 Site
Describe the site(s) of data collection, why the site is chosen.
3.1.3 Procedures
RBF is a natural treatment technique by means of soil passage of river water. RBF has been used for common pre-treatments implemented by drinking water companies consuming river water as a drinking water source, used for the removal of 0-bacteria, pathogens, protozoa, turbidity, and natural organic matter (Florian et al., 2012). In evaluating the efficiency of RBF, a number of methods were used, and their success or otherwise were reported. Measuring the efficiency of RBF involves many diverse components, ranging from site characteristics, lithological information, aquifer hydraulic parameters, hydrochemistry, and degradation processes (Umar et al., 2017).
Numerous recent studies on RBF have demonstrated the available water treatment methods that can be utilised together with RBF, as shown in Table 3.1.
Table 3.1: Summaries of Available Water Treatment Methods that has Utilized Together with RBF
The specific research on RBF was reviewed by water quality based on categories and summaries of the objectives, and the major findings. From this review, most of the methods focused on the determination of water quality in bank filtrates to improve the quality of the surface water. Thorp (2013) reported that aqueous geochemical techniques increased the groundwater chloride concentrations, and indicated that 35% to 40% of groundwater was induced from the river. This method is one of the possible solutions in RBF inducement for river water induced into the adjacent aquifer as recharge to increase groundwater quality (Hiscock and Grischek, 2002). In the RBF process, subsurface water under the direct influence of surface water flows through the aquifer. In a study by Mutiti and Levy (2010) using heat flow modelling, they found that hydraulic conductivity increases during storm events when the river stage is high enough to potentially scour
between the river and the underlying aquifer did increase during the rising limb of the storm. The riverbed and aquifer material act as filters for contaminants in river water and, therefore, protect the production-well water from contaminants (Alessio et al., 2015).
3.2 E. coli Removal via Riverbank Filtration
RBF is a water treatment technology that involves extracting water from rivers by pumping wells located in the adjacent alluvial aquifer. In the underground passage, a series of physical, chemical, and biological processes take place, improving the quality of the surface water, while substituting or reducing conventional drinking water treatments. A study based on a model-oriented approach by Wang et. al (2015) used an example of riverbank wells near the Kuybyshev Reservoir, Russia.
The wells were designed in order to minimise the uncertainties in the estimated hydraulic parameters. During water transport towards the RBF wells, the water quality improved significantly, aided by processes like microbial degradation, ion exchange, precipitation, sorption, filtration, dispersion, and groundwater dilution. Faecal and total coliforms are bacterial indicators that are widely used to monitor microbial water quality in developed and developing regions of the world. Faecal contamination of drinking water supplies is a public-health concern because they could contain pathogens that cause gastroenteritis, meningitis, and other waterborne diseases (WHO, 2006). Potential sources of faecal contamination include direct discharge from human and animal wastes as well as non-point sources (agricultural and storm water runoffs). Majority of the RBF systems used in European countries and America alike have achieved excellent total coliform removal percentages, ranging from 99.2% to 99.99% (2.1 to 5 logs).
3.3 Drawbacks of RBF Treatment System
Implementation of RBF has higher potential advantages for conjunctive use with infiltrated surface water and groundwater from the alluvial catchments of intake structures (Wang et al., 2015), which ensure the long-term productivity and stability of the water supply (Lorenzen, Sprenger, T. Taute, Asaf Pekdeger, & Massmann, 2015). Additionally, surface water contaminants can be significantly removed or degraded as the infiltrating water moves from the river or lake to the production wells due to a combination of physicochemical and microbiological processes (Hiscock and Grischek, 2002; Maeng et al., 2010; Singh et al., 2010). While RBF has good pollutant attenuation, there is still a possibility for this source to be contaminated by anthropogenic or natural pollutants. For example, short flow paths, high heterogeneity, high hydraulic gradients, and accompanying high flow velocities (Derx et al., 2013) can impair the efficiency of removal of microbial contaminants with RBF. Nevertheless, an important benefit of RBF processes is that they can remove pollutants, and dilute contaminant concentrations during the infiltration process.
3.3.1 Validity and Reliability
Furthermore, the removal efficiency of RBF systems is influenced by climate change.
Temperature, and the natural organic, dissolved organic, and particulate organic matter composition of surface water, as well as seepage travel times, may influence the redox milieu during RBF, and result in the decreased quantity and quality of water (Maeng et al., 2010; Doussan et al., 1997). Temperature directly influences redox processes by influencing microbial activity, the solubility of various components, and redox reactions (Tessaro et. al, 2015). Moreover, extreme climate conditions also influence the redox conditions in RBF systems, which is reflected in infiltration rate, seepage residence time, oxygen consumption, and variations in pollutant concentrations in the surface water (Diem et al., 2013; Doussan et al., 1997). Although the removal efficiency of pollutants by RBF is remarkable, it cannot replace waterworks treatment processes.
When compared with water treatments by traditional waterworks, the main disadvantages of RBF are limitations in the specific pollutant removal capacity, and requirements for seepage residence time. Moreover, variations in external conditions (e.g., changes in river hydrodynamics, climate, and river quality) also limit the purification capacity of RBF. Thus, in public water supply systems, RBF is only used as a pre-treatment step.
4. Results and Discussion
Compared to the achievements in the management and construction of RBF in the Western hemisphere, there is still a large gap in Malaysia. Because of a lack of specific management standards, operation technology guidelines, and waterworks construction standards for riverside groundwater sources, the government’s management responsibility is ambiguous. Thus, the application of RBF in Malaysia has only just begun. According to previous studies, RBF systems in Malaysia have a large effect on the contaminant concentration, and consequently on the quality of water produced (Mustafa et al., 2016). These factors impose pressure in terms of treatment costs and increased demand on existing water treatment plants, which has prompted water-resource agencies to look for alternative supplementary sources. However, detailed published works on the successful implementation of the RBF system in the tropical region remain few, and only a few efforts have been made so far to understand the RBF mechanism and processes. The gap in water abstraction knowledge on RBF needs to be explored in order to provide better alternatives for water security sources.
5. Conclusion
In order to understand and develop further knowledge on RBF, the Universiti Sains Malaysia (USM) research team embarked on the study of RBF at different locations in Malaysia. Three pilot projects of RBF facilities were constructed in the states of Selangor, Perak, and Kedah. The results from the proposed analytical model are well matched with the data collected from a RBF site in France. After this validation, the model was then applied to the first pilot project of a RBF system conducted in Malaysia. Sensitivity analysis results highlighted the importance of the degradation rates of contaminants on groundwater quality, for which higher utilisation rates led to the faster consumption of pollutants (Mustafa et al., 2016). The development perspective of RBF in Malaysia is promising. With the establishment of a management system, improvement of the monitoring system, reinforcement of legal protection, and promotion of civic awareness, Malaysia RBF will
6. Acknowledgement
The authors would like to acknowledge the Centre of Research and Innovation, Department of Polytechnic and Community College Education for providing TVET Research Grant Scheme on
“E.Coli Removal Via Low Frequency Electromagnetic Field In Riverbank Filtration” (T- ARGS_ID: K2146).
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