Initial turbidity and e concentrations of moringa solution used in experiments.
Contamination of water resources, especially in areas with inadequate sanitation and water supply, has become a risk factor for health problems (Fundação Nacional de Saúde [FUNASA], 2003), with water playing a role as a vehicle for transmission of biological agents (viruses, bacteria, and parasites) as well as a source of contamination by chemicals (industrial effluents).
Among the waterborne diseases, enteric diseases are most frequent. Approximately 19% of waterborne gastroenteritis outbreaks in the United States are attributed to parasitic protozoans (Lindquist, 1999), particularly
Despite regulations and control measures turning to be more and more stringent, outbreaks of waterborne
Due to its small size and resistance to chlorine disinfection, conventional processes used in water treatment systems are unable to remove or inactivate efficiently all (oo)cysts of these protozoans, depending, among other factors, on concentration of (oo)cysts in water and the integrity of the water treatment plants. In addition to these microorganisms, many other impurities can harm human health if not reduced or eliminated. These impurities do not approach each other, it is necessary to add a coagulant.
Chemical coagulants are the most used and among them the most common is aluminum sulfate, since it is cheap and easily obtained. However, chemical coagulants have certain disadvantages, as they require tight control over their residual concentration in treated water for human consumption as well as in industrial food production. The possibility of trace aluminum contamination in food, as well as undesirable damage to the human body, especially the nervous system, are scientifically proven facts and subject of constant and innovative medical research worldwide, which increasingly requires a rigorous control of the presence of metals in both drinking water and groundwater (Ndabigengesere & Narasiah, 1998; Rondeau et al. 2000).
One alternative that arises in this context is the use of natural coagulants that have advantages over chemical coagulants since they are biodegradable and non-toxic, and produce sludge in less quantity and with lower metal content. Seeds of
Studies have shown that moringa seeds have coagulation properties for treating effluents, as well as water. The seeds can be prepared either in water or in saline solution, removing color, turbidity, and total and thermotolerant coliforms (Nkurunziza et al., 2009; Madrona et al., 2010).
The use of coagulants for drinking water treatment, in spite of being efﬁcient in the removal of most contaminants, is not able to generate water of high potability standards, which leads to the necessity of the simultaneous use of other techniques. Membrane ﬁltration technique is already widely recognized and can be implemented in combination with coagulation processes.
The NOM found in the liquid leads to membrane fouling, flux reduction and inferior effluent quality. Therefore, the application of coagulants for the raw water pretreatment may bring about an improvement in permeates quality. This is very important, especially in the case of drinking water production. Conjunctive use of coagulation and membranes is becoming more attractive for water treatment because the coagulation is an opportunity to join NOM with other particles present in water before NOM reaches the membrane surface.
This way, this chapter will look at the use of alternative techniques for water treatment based on the use of natural coagulant (moringa seeds) associated with the membrane filtration process (microfiltration) to obtain
Cryptosporidiumspp .and cryptosporidiosis
The oocyst is the stage transmitted from an infected host to a susceptible host by the faecal-oral route. Routes of transmission can be (1) person-to-person through direct or indirect contact, possibly including sexual activities, (2) animal-to-animal, (3) animal-to-human, (4) water-borne through drinking water or recreational water, (5) food-borne, and (6) possibly airborne (Fayer et al., 2000). The water-borne transmission depends by the level of environmental contamination, survival of the oocysts to environmental conditions (Robertson et al., 1992), and oocyst resistance to a variety of methods used to water treatment (Korich et al., 1990) as chlorination, ozonation or incomplete removal of the oocysts by filtration methods. The disease is caused by protozoan parasites of genus
According to Neves (2005), the genus
Until now, it is recognized 15 species of
The diversity of reservoirs and the means of
The rapid lifetime, the auto-infective cycles of
In the immunocompetent patients, the disease is self-limiting, the symptoms are often sudden with diarrhea over about 10-14 days, although there are cases described as long as three to five weeks. The symptoms disappear spontaneously and within a few months get the parasitological cure. The excretion of oocysts in the feces is intermittent and usually longer than the symptomatic phase of disease (Andrade Neto & Assef, 1996).
In immunocompromised individuals, infection is chronic and the severity and persistent diarrhea are greater than in immunocompetent individuals, it can persist indefinitely and evolve into intense dehydration and death. There is no data to indicate that immunocompromised individuals are more susceptible to infection than immunocompetent individuals. However, those with compromised immune systems are more severely affected by cryptosporidiosis (Butler & Mayfield, 1996).
The control of cryptosporidiosis is often limited by the high resistance of the oocysts to disinfectants commonly used, such as ammonia, sodium hypochlorite and chlorine. The absence of an effective treatment to combat infection increases the magnitude and enhances the importance of preventing cryptosporidiosis. The oocysts control in public water supplies, in the face of their resistance to conventional treatment is a concern worldwide, and numerous studies have been developed for this purpose (Assavasilavasukul et al., 2008; Brown & Emelko, 2009).
The small size of the oocysts, as well as apparently existing flexibility facilitate the passage of
Further studies are being conducted to improve the treatment processes, optimizing filtration processes, operating conditions, including the coagulant dosage, mixing and monitoring of filters (Rose, 1990; Brown & Emelko, 2009). Problems such as coagulant dosages, inadequate processes of mixing, inadequate monitoring of filters, turbidity, using saturated filters, among others were analyzed in Pennsylvania by Consonery et al. (1997), with optimization of processes, positive samples were reduced from 35% to values lower than 5%.
Oocysts and other microorganisms that are not effectively removed by filtration should therefore be inactivated by the disinfection process. However, the
Campbell et al. (1982) demonstrated that
Giardiaspp. and giardiosis
Currently, the classification has been adopted for
The cysts are released for an extended period and in large numbers (1.4x1010 daily) in the feces of humans and certain animals. Can survive for several months in cold water, are relatively resistant to chlorination and ultraviolet light. The boiling is very effective in destroying the cysts, but some may resist freezing for a few days. The infection can be caused by low doses of up to 10 cysts, can occur by direct contact, very common among children in day care center and through ingestion of contaminated food or water (Ortega et al., 1997).
Due to several reasons, nowadays giardiosis is considered a reemerging parasitic. The first of these reasons relates to the large number of diarrhea outbreaks in day care centers. In developed countries, the increasing use of these institutions is one reason for the reemergence of the disease. Another reason pointed out as a cause of re-emergence of this disease relates to high rates of
The filtration processes are important barrier for removal of cysts in the water treatment. The main concern in water treatment plants for cysts removal should focus on the filtration processes, as well as optimizing operations and improvements in processes for cysts removal (Plutzer et al., 2010).
Disinfection with chlorine and derivatives is an important barrier to waterborne pathogens, however they are less effective against
There is also the risk of post-contamination (Karanis et al., 2007) when the water distribution system or water reservoirs are contaminated. This post-contamination can occur because of leakage of contaminants along the distribution system, on distribution reservoirs opened or due to inadequate disinfection after construction or repair in the network. Improper connections can inject water sources contaminated with domestic sewage on the distribution network. Public or domestic water tanks can be contaminated due to animals’ access (Robertson et al., 2009).
Biofilms formation in the pipeline distribution network can also contribute as a potential source for water contamination by
1.3. Moringa oleifera Lam
If moringa is proven to be active, safe, and inexpensive, it is possible to use it widely for drinking water and wastewater treatment. Besides, moringa may yet have financial advantages bringing more economic benefits for the developing countries (Okuda et al., 1999).
The moringa seed has a protein that when solubilized in water is able to promote coagulation and flocculation of compounds that cause color and turbidity in highly turbid water. Several studies have also shown their effective antimicrobial and antifungal capacity, thereby contributing to good water quality at low cost (Chuang et al., 2007; Coelho et al., 2009). Several studies have shown the effectiveness of moringa on color, turbidity and other compounds removal present in the water.
Moringa has been found to be effective as a natural coagulant for high turbidity water in previous studies (Okuda et al., 2001). This was verified in a study by Nishi (2011). The authors obtained values of color and turbidity removal over 90% when the water to be treated showed high values of initial turbidity, between 350 and 450 NTU. A moringa concentration of 150 mg/L would have been sufficient to achieve this level of removal. The coagulant derived from moringa seeds, as it contains a certain amount of organic matter, can give color and turbidity to the treated water.
An important point to be considered when using moringa as a coagulant is related to the pH of the water to be treated. For chemical coagulants, water pH adjustment is necessary for the flakes to be properly formed. In the case of the moringa, there is no need for this adjustment, and this parameter is not changed after treatment, as evidenced by Vieira et al. (2010). Moringa is an efficient coagulant in a wide pH range (6-8), which is an advantage compared with other coagulants, as the pH adjustment step can be eliminated in the coagulation/flocculation processes.
2. Materials and methods
2.1. Water samples
Surface water used in the tests was collected in the river basin Pirapó, which supplies the Maringa city, Paraná, Brazil. Samples of the water with high and low turbidity were mixed in order to obtain different initial turbidity in the range 50 - 450 NTU. Prepared samples were artificially contaminated with 106 cysts/L for
After sample preparation, these were submitted to processes of (1) coagulation/flocculation with moringa seeds (CFM), (2) microfiltration (MF) and (3) combined coagulation/flocculation with moringa seeds followed by microfiltration (CFM-MF).
2.2. Coagulation/flocculation with moringa (CFM)
The coagulant solution of moringa was prepared and used on the same day. 1 g of mature
|Initial turbidity of water samples (NTU)||50||150||250||350||450|
|Moringa solution concentration (mg/L)||25||50||75||100||125||150||175||200||225||250||275||300|
CFM tests were conducted in a Jar-Test equipment, Nova Ética - Model 218 LDB in six buckets, with rotation regulator of mixing rods. The experimental conditions for the CFM process were: rapid mixing gradient (100 rpm), rapid mixing time (3 min), slow mixing gradient (10 rpm), slow mixing time (15 min) and settling time (60 min) (Cardoso et al., 2008, Madrona et al., 2010).
In this process, the measured parameters in experiments were color, turbidity, pH,
2.3. Microfiltration process (MF) and coagulation/flocculation/ microfiltration sequence (CFM/MF)
The membrane filtration tests were performed on a microfiltration bench unit (PAM-Membranas Seletivas®) (Figure 1). This module is made of stainless steel, with polymeric membrane (1). The system is composed by manometers (2) and flow meter (3) to control the transmembrane pressure and flow rate, feed tank (4) with volume capacity of 5 liters. The permeate output (5) was collected with valve opening (6) and the return of the concentrate to the feed tank was conducted through the pipe (7).
The MF membrane employed had form of hollow fibers made up of poly (imide), with 0.40 μm pore diameter, fiber external diameter between 0.8 and 0.9 mm, fibers with external selective layer. The filtration is cross flow and the pressure used was 1.0 bar. In order to have uniformity in the tests set up the feed initial volume of 5 liters and assay time of 60 minutes.
In this part of the study, MF without pretreatment and coagulation/flocculation/ microfiltration sequence with moringa (MF-CFM) were performed. These processes were performed to observe if MF with pre-treatment (coagulation/flocculation with moringa) showed differences between the MF processes without pre-treatment. The membrane processes, in addition to analysis of
2.3.1. Evaluation of permeate flux and fouling percentage of membranes for MF and CFM-MF processes
The membranes were first compacted and were then stabilized with deionized water until achieving a steady permeate flux. Permeate samples were collected at predetermined times, by known time intervals, and analytical balance were used to measure the permeate flow rate indirectly based on weight increase, according to the Equation (1).
where f is the permeate flux, m is permeate mass (g), ρ is the water density (25ºC), Δt is the time interval during which the sample was collected (s) and Am is the surface area.
The permeate samples were collected at shorter time intervals at the beginning of filtration, such intervals, increased subsequently to determine the curve of permeate flux versus time. The membrane filtration processes were performed using raw water (RW) without pre-treatment and after coagulation/flocculation with moringa (CFM).
The removal efficiency for each parameter analyzed using different treatment processes was calculated from Equation (2), where Ci and Cf are the initial and final concentrations, respectively, to each parameters:
The water flux of deionized water (DW) were determined before each experiment (Jinitial) and after the MF of RW and CFM solutions (Jfinal) for determining the fouling of the membrane. The percentage of fouling (% F) was calculated according to Equation (3), proposed by Balakrishnan et al. (2001), using stable flow values, which assume that the flow tends to constant values. This %F represents a reduction of deionized water flow after tests with contaminated water. In Equation (3), F% is the percentage of fouling, Ji is the initial flow of water obtained in the first filtration with deionized water and Jf is the final flow of water obtained with the filtration of deionized water after filtration of surface water.
2.4. Parameters evaluated
The parameters evaluated were apparent color, turbidity, pH,
2.4.1. Apparent color
The color was measured on a spectrophotometer HACH DR 2010, method 8025, program 120, wavelength of 455 nm, by visual comparison with platinum-cobalt standard, according to the procedure recommended by the Standard Methods (APHA, 1995). The result of color was given in uH = Hazen unit (mgPt-Co/L).
The turbidity was determined in Turbidimeter portable HACH - Model 2100P, according to the procedure recommended by the Standard Methods (APHA, 1995). The result of turbidity was expressed in NTU (Nephelometric Turbidity Units).
2.4.3. Giardia spp. e Cryptosporidium spp. analisys
The treated samples were evaluated for the presence of
1) Filtration in cellulose acetate membrane (Millipore ®), with 47 mm pore diameter and 1.2 µm porosity, 2) mechanical extraction of the material retained on the membrane with the aid of plastic spatulas by alternating washes of the membrane surface during 10 minutes in a Petri dish with a solution of elution Tween 80 1%, 3) Repeat of procedure (2) to extract the greatest possible amount of material retained; 4) the material was centrifuged at 600 x g for 15 minutes. The supernatant was discarded with the aid of glass pipettes until the volume of 3 ml and the sediment was resuspended in distilled water by supplementing 15ml of centrifuge tube and then centrifuged again at 600 xg for 15 minutes, 5) The supernatant was discarded to a volume of 1 ml of centrifuge tube and the sediment was resuspended in this volume.
Of the sediment resuspended in 1 ml of distilled water, 5 µl were used for the direct immunofluorescence technique, using the Merifluor commercial kit (Meridian Bioscience,
Cincinnati, OH, USA). Simultaneously, a confirmatory test was performed with inclusion of the fluorogenic vital stain DAPI (4¢, 6¢-diamidine-2-phenylindole; Sigma Chemicals Co., St Louis, MO, USA) to reveal the morphological characters (nucleus, axoneme and suture) (Cantusio Neto & Franco, 2004). To read the preparations, an Olympus BX51 epifluorescent microscope was used (with excitation filter: 450–490 nm and emission filter: 520 nm for the Merifluor; excitation filter: 365–400 nm and emission filter: 395 nm for the DAPI). The numbers of oocysts and cysts per litre in the positive samples were estimated by the following calculation (EPA, 1999; Cantusio Neto & Franco, 2004):
The following are the results obtained in the processes of coagulation/flocculation with moringa (CFM), microfiltration (MF) and coagulation/flocculation/microfiltration sequence with moringa (CFM-MF) for protozoan parasites, color, and turbidity removal and pH values of the of treated water samples.
3.1. Results obtained in coagulation/flocculation process with moringa (CFM)
The initial characteristics of water samples used in the study are presented in Table 2.
|Turbidity (NTU)||Color (uH)||pH|
Table 3 presents the results of turbidity, color and parasitic protozoa removal efficiency and pH values of water samples after coagulation/flocculation with moringa.
|Moringa solution concentration 1% (mg/L)|
|Initial turbidity (NTU)||Removal efficiency (%)||25||50||75||100||125||150||175||200||225||250||275||300|
Using moringa as coagulant, turbidity ramoval was in the range of 3 – 97,4%. The lower removal efficiencies were in the range of 3-45,6% for water with low initial turbidity (50 NTU), removal below 90% were observed for water with turbidity 250, 350 e 450 NTU. The decrease in efficiency of turbidity removal in water with initial turbidity 50 NTU, after the moringa addition, can be explained by an increase in organic load. This is justifiable, considering moringa is an oilseed rich in organic substances such as oil, protein, fat, vitamins, etc.. This parameter increase in color and turbidity in water treated with moringa is observed in other studies, especially when the water has initial color and turbidity relatively low (Ramos, 2005).
Nkurunziza et al. (2009), using solution of moringa seeds 3%, prepared in saline solution, in water from rivers of province Rwanda, observed removal efficiency of 83.2% in the samples with turbidity of 50 NTU and higher removals (99.8 %) in water with turbidity of 450 NTU. The best concentrations found in this study were 150 mg/L for 50 NTU and 125mg/L for other levels of turbidity tested by researchers. The results of turbidity removal for water with low initial turbidity (50 NTU) were higher than those obtained in this study (45.6%) and for water with high initial turbidity (450 NTU) were similar (97.4%). The differences may be due to the way of moringa solution preparation by extracting aqueous or saline, and different concentrations used of the moringa stock solution (1% in this study). In both studies, it was noted that the coagulating property of the moringa is shown more effectively in water with high initial turbidity, in agreement with published studies (Ndabigengesere et al., 1995; Madrona et al, 2010).
Ndabigengesere et al. (1995) using solution of moringa seeds 5% on synthetic turbid water (kaolin) with initial turbidity of 426 NTU, obtained removal of 80-90% and reached the optimum concentration of 500 mg/L coagulant solution. This concentration is higher than optimal concentration of 450 NTU water obtained in this study, which was 275 mg/L. This difference between the optimal concentrations of the moringa solution may have occurred due to the water used in the study. Ndabigengesere et al. (1995) used synthetic water prepared with kaolin and the present study used surface water. Cardoso et al. (2008), however, used similar conditions to the present study, obtained turbidity removal of 91.4% in surface water from the river Pirapó with 247 NTU, with aqueous moringa, removal efficiency with a value close to that observed in this study (96% rof turbidity removal for water with initial turbidity of 250 NTU). Thus, the similarities or differences between the removal efficiencies of turbidity and optimal concentrations can be explained by the different types of water samples used by the works (raw water, artificial water), as well as the method of moringa solution preparation (salt extraction, aqueous) concentrations evaluated, seed quality, among other factors.
With respect to color, removal ranged from 0.11 to 30% for water with initial turbidity of 50 NTU, high removals in this sample were within the concentration range 175-250 mg/L. Water with higher initial turbidity (150-450 NTU), the removal efficiency varied from 10 to 97%, with the major removals from the concentration of 150 mg/L of the coagulant. It is observed that the color removal by Moringa is similar to its behavior with respect to turbidity, the lowest values of the color parameter are obtained in waters with high initial turbidity, which agrees with literature data (Cardoso et al., 2008; Nkurunziza et al., 2009; Madrona et al., 2010). For pH values of water samples after the coagulation process with different concentrations of moringa, it was observed that the pH is maintained, on average, 7.6, ranging from about 10%. There was little variation between samples regardless of the amount of moringa solution added, which consists of one of the advantages of moringa as a coagulating agent, i.e., its addition does not significantly alter the pH of water (Ndabigengesere et al., 1995; Nkurunziza et al., 2009), unlike treatment with aluminum sulfate in which it is necessary to adjust the pH of the water to improve its coagulating action, increasing the amount and cost of chemicals for water treatment.
Regarding the removal of
The removal of protozoan parasites obtained in this study is close to the results of other studies, using chemical coagulants such as aluminum sulfate and ferric chloride, for these microorganisms removal of these microorganisms (Bustamante et al 2001; Xagoraraki & Harrington, 2004), and also charge neutralization the main mechanism of coagulation using aluminum sulfate in that frame. Brown & Emelko (2009) analyzed other natural coagulant, chitosan, for the removal of
3.2. Results obtained in microfiltration process (MF) and coagulation/flocculation/microfiltration sequence (CFM-MF)
The results obtained in the processes of microfiltration (MF) and coagulation/flocculation with moringa followed by microfiltration (CFM-MF) are presented below. These results are presented together to show if the pretreatment (coagulation/flocculation with moringa) had differences in relation to the MF process without pretreatment. The removal efficiencies and the pH of the water treated by the MF and CFM-MF processes are presented in Table 4.
|Initial turbidity (NTU)|
|Treatment process||Removal efficiency (%)||150||250||350||450|
It can be observed that the largest color and turbidity removals occurred with the combined CFM-MF process, compared with the MF process without pretreatment. There were no changes in the pH of the treated water. It is clear that the use of coagulation/flocculation with moringa prior to microfiltration improves the quality of treated water.
Few studies were found in the literature regarding the CF/MF process using moringa as a coagulant for surface water treatment. Madrona (2010) evaluated the combined process of coagulation/flocculation with moringa and MF with ceramic membranes, and obtained 97 to 100% removal of turbidity and color in the treatment of surface water from the Pirapó River, in Maringá, Paraná. These results were similar to those obtained in the present study, which used a polymer membrane for the MF process. Parker et al. (1999), using hollow fiber MF membranes with 0.2 µm pores for the treatment of water that had been previously treated in settling tanks, obtained water with turbidity below 0.1 NTU, with average removal of 99.46%, similar to those obtained in this study.
Neither in the microfiltration (MF) process alone, nor in the combined (CFM-MF) processes, (oo)cysts of
Thus, one can say that MF may act as a barrier against protozoan (oo)cysts. The coagulation/flocculation with moringa associated with microfiltration resulted in high levels of removal of the evaluated parameters.
Figure 3 shows the permeate flux versus time for the microfiltration of deionized water (DW), raw water without coagulant (SW), and pretreated water (CFM).
For the MF process with raw water, that is, without previous treatment (coagulation/ flocculation), permeate flux ranged from 157 to 187 L/hm2 for water samples of turbidity from 150 to 450 NTU. In the combined process (CFM-MF), permeate flux ranged from 157 to 226 L/hm2 for water samples with initial turbidity of 150 to 350 NTU. Samples of 450 NTU presented the lowest permeate flux, 91 L/hm2, on average (Nishi, 2011). This may be due to the presence of a greater number of particles that can cause the process of concentration polarization and due to superposition of various fouling mechanisms in the membrane, which may cause the decrease of the permeate flux (Stopka et al., 2001).
The combined processes of coagulation/flocculation/microfiltration showed slightly higher fluxes when compared with the microfiltration process alone. The improvement in permeate flux using coagulation/flocculation prior to microfiltration was also observed in other studies (Katayon et al., 2007; Horčičková et al., 2009).
The percentage of fouling (%F) for the MF process with raw water (SW) and water coagulated/flocculated with moringa (CFM) with initial turbidity from 150 to 450 NTU is shown in Figure 4.
It is observed that the MF process with raw water showed higher percentages of fouling, ranging from 6.13 to 56.32% when compared with the combined process of coagulation/ flocculation with moringa followed by MF, which presented percentages of fouling from 7.48 to 40.9% (Nishi, 2011). This reduction in membrane fouling when using the process of coagulation/flocculation as pretreatment was also observed in other studies. Madrona (2010) used coagulation/ flocculation with moringa, followed by MF with ceramic membranes with porosity of 0.1 and 0.2 µm, for the treatment of surface water and observed fouling percentages of around 94% during the filtration of raw water and slightly lower values, around 88%, when water previously coagulated/flocculated with moringa was filtered. Carroll et al. (2000) used polypropylene hollow fiber MF membrane to filter surface water from the Moorabool River, Australia, and observed fouling percentages of 80% for water without pretreatment and 50% for water pretreated by coagulation with alum.
According to Cheryan (1998), the type and extent of fouling depend on the chemical nature of the membrane, the solute, and the solute-membrane interactions, as well as on the porosity of the membrane and the working pressure used in the process.
It was possible to conclude that the coagulation with moringa performed satisfactory results, reducing the number of (oo)cysts of protozoan parasites in the study, 1.2 log removal for
Furthermore, there was a reduction on turbidity and color approximately 97% and the pH remained stable in all water samples treated with moringa.
The combined process, coagulation/flocculation/microfiltration sequence, removed almost 100% of
The use of M. oleifera Lam seeds can be considered advantageous and a promising step towards improving the processes of water coagulation/flocculation followed by microfiltration.
List of abbreviations
Coagulation/flocculation = CF
Coagulation/flocculation using moringa as coagulant = CFM
Coagulation/flocculation using moringa as coagulant followed by microfiltration = CFM-MF
Microfiltration = MF
Moringa oleifera = moringa
Natural organic matter = NOM
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