International Journal of Civil Engineering and Technology (IJCIET) Volume 10, Issue 06, June 2019, pp. 298-305, Article ID: IJCIET_10_06_029 Available online at http://iaeme.com/Home/issue/IJCIET?Volume=10&Issue=6 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication

REMOVAL OF OUT OF RAW WATER FOR SYSTEMS BY MEANS OF FILTRATION IN MULTIPLE STAGES USING HIGH APPLICATION RATES

Jhon J. Feria Díaz* Faculty of Engineering, University of Sucre, Carrera 28 No. 5-267. Sincelejo, Colombia

Juan P. Rodríguez Miranda Faculty of Environment and Natural Resources, Universidad Distrital Francisco José de Caldas, Carrera 7 No. 40B-53. Bogotá D.C, Colombia

Marinela B. Álvarez Borrero Faculty of Health Sciences, University of Sucre, Carrera 28 No. 5-267. Sincelejo, Colombia * Corresponding Author

ABSTRACT Localized irrigation is an important technique for a high yield of agricultural crops. Nonetheless, use of raw water with high turbidity is the cause of obstructions in sprinklers and deterioration of irrigation systems. Then, it is necessary to treat raw water to reduce present solids and avoid this problem. This research study aimed at evaluating MSF technology for raw to use in irrigation systems. A pilot plant with PVC pipe, gravel and sand was built, two types of raw water were tested with different Initial Turbidity levels (100 and 200 NTU) and different application rates (100, 160, 240 and 360 m3m-2d-1). Tests showed 94% turbidity removal efficiencies and 4 NTU final turbidity for initial turbidity waters of 100 NTU; and 16 NTU for initial Turbidity waters of 200 NTU. By applying a complete treatment train of MSF to water samples with high turbidity, it is possible to guarantee non-obstruction of nozzles from the sprinklers and their continuous use in high performance crops. Key words: Multi-Stage Filtration, Turbidity, Localized irrigation systems, Sprinklers Cite this Article: Jhon J. Feria Díaz, Juan P. Rodríguez Miranda and Marinela B. Álvarez Borrero, Removal of Turbidity Out of Raw Water for Irrigation Systems By Means of Filtration in Multiple Stages Using High Application Rates, International Journal of Civil Engineering and Technology 10(6), 2019, pp. 298-305. http://iaeme.com/Home/issue/IJCIET?Volume=10&Issue=6

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1. INTRODUCTION Productivity and of modern agriculture has increased thanks to the implementation of irrigation systems. Furthermore, low-irrigated agriculture with low inputs is more productive than -fed agriculture with high inputs. Control, with sufficient precision, of water absorption by plants roots has these advantages [1]. Nevertheless, raw waters with high turbidity levels represent a major technical problem when applying water to soils due to the obturation of nozzles from the sprinklers, avoiding uniformity of irrigation and, therefore, uniformity in production and plant growth [2] [3]. Localized irrigation systems are highly demanding in and should be treated before being distributed in the system in order to reduce obstruction risk [4]. On the other hand, surface water is a global problem that contributes to high rates of morbidity and mortality due to water and foodborne [5] [6], one more reason to treat raw water before use in irrigation systems. Multi-Stage Filtration (MSF) is a combination of Coarse Filtration in Gravel (CFG) and Slow Filtration in Sand (SFS) [7] [8]. This combination allows to treat water with pollution levels much higher than those that can be treated using only SFS [8]). In a MSF system, water passes through different treatment stages, with progressive removal of solid substances occurring at each stage. In the first treatment stage, called dynamic coarse pre-filtration, separation of large solids is presented. In the next step or ascending gravel pre-filtration, gradual reduction of fine matter and is achieved, with a greater polishing of the raw water before passing to the SFS. In the third stage (SFS), a biological layer is formed on the sand´s surface that helps in the production of water with acceptable quality [9]. Water quality obtained using SFS technology is comparable, and even better, than that obtained with a purification plant of conventional technology, because processes of elimination of and microorganisms are mainly physical and biological [10] [11]. High application rates (between 96 and 240 m3m-2d-1) have been tested, but in large- scale conventional treatment systems for raw water with turbidity between 300 and 500 NTU, with granular media up flow, managing to reduce construction costs between 30% to 50%, compared to conventional systems of equal capacity [12] [13]. In general terms, MSF can provide a robust treatment alternative for surface water sources of variable quality in rural communities, with low operation and maintenance costs [11]. The objective of this work was to evaluate behavior of pre-treatment filters and slow sand filters from a MSF system, when subject to high application rates and under conditions of high turbidity of raw water, in order to improve water quality before being distributed through the sprinklers of the irrigation systems in a soil with agricultural use.

2. MATERIALS AND METHODS 2.1. Raw Water Samples Specific samples of raw water were taken from the Sinú , in the city of Monteria, Colombia. The samples correspond to both the rainy (August 2018) and the dry season (December 2018) from the region.

2.2. Pilot Plant Multi-Stage Filtration (MSF) In order to carry out the tests in the pilot plant, sand and gravel from the Sinu River were used, previously screened and washed. Three filters were mounted on a 6" PVC pipe, with lengths of 70 cm, 70 cm and 90 cm, for the Coarse Gravel Filter, Medium Gravel Coarse Filter and , respectively. The coarse gravel filter was constructed using rocks with a diameter between 2" and 4". For the next stage of the treatment, rocks with a diameter

http://iaeme.com/Home/journal/IJCIET 299 [email protected] Jhon J. Feria Díaz, Juan P. Rodríguez Miranda and Marinela B. Álvarez Borrero between 0.5" and 2" were used and finally, the was made up of a 10 cm layer of thick rocks in the bottom, followed by a 10 cm layer of medium rocks and finally, a sand layer passed through a sieve of 0.7 mm and a height of 20 cm (Feria et al., 2018). Figure 1 shows the pilot plant assembly used for the treatability tests.

Figure 1 Experimental Pilot Plant Assembly

2.3. Physico-chemical parameters In order to determine the efficiency of the multi-stage filtration plant, turbidity, pH and alkalinity of water before and after treatment were evaluated, according to the standard methods proposed by The American Public Health Association [10] [14]. Efficiency of the turbidity removal was estimated according to the following equation:          (1) 

2.4. Experimental Design An experimental design was carried out for 2 variables: initial turbidity of raw water and application rates. 100 and 200 NTU were the evaluated and correspond to the dry and rainy season of the Sinu River, respectively. 100, 160, 240 and 360 m3m-2d-1 were the application rates used in the pilot plant evaluation. The response variable measured before and after the treatment train was Turbidity. The Statgraphics Centurion XVI Software (Version 16.0.07) was used to analyze results and an ANOVA was applied with a 95% confidence level.

3. RESULTS AND DISCUSSION 3.1. Turbidity Removal in the Coarse Gravel Filter Figure 2 shows results of turbidity removal achieved in the coarse gravel filter; the first stage of the treatment train responsible for serving as a shock structure against high turbidity of raw water.

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72

62 ) % (

52 l a ov m

e 42 R

32

22 100 200 Initial Turbidity (NTU)

Figure 2. Turbidity Removal in Coarse Gravel Filter For the raw water sample of 100 NTU initial turbidity, a turbidity removal between 32% and 61% efficiency was achieved. It was verified that, at a higher rate of application, the removal efficiency increased. For the water sample with initial turbidity of 200 NTU, the removal was less than the one achieved in the previous samples, regardless of the value of the applied rates. Removals between 22% and 63% removal efficiency were obtained. To check if there were statistically significant differences between the removal efficiencies found among the samples, compliance with the assumptions of normality, variance, homogeneity and independence of the samples was verified and an ANOVA was applied [15]. Table 1 shows the ANOVA results.

Table 1. ANOVA between Turbidity Removals in the Coarse Gravel Filter Source Sum of Squares DF Mean Squares F-Value P-Value Between 0.1250 1 0.125 0.00052 0.9824 Within Groups 1421.75 6 236.958 Total (Corr.) 1421.88 7 Since P-value is greater than or equal to 0.05, there is no statistically significant difference between the turbidity removal average (%), one turbidity level and another, with a 95.0% confidence level. That is, the average turbidity removal is similar between samples, regardless initial turbidity of raw water and application rate.

3.2. Turbidity Removal in the Medium Gravel Coarse Filter

60

50

) 40 % (

l a

v 30 o m e

R 20

10

0 100 200 Initial Turbidity (NTU) Figure 3. Elimination of turbidity in the coarse gravel filter

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Figure 3 shows the behavior of the turbidity removal in the raw water samples tested. Only the removal efficiency of the medium gravel coarse filter and not the cumulative efficiency of the treatment train at this stage is shown. There was less removal efficiency on samples of 100 NTU of initial turbidity (between 10% and 37%) than on samples of initial turbidity of 200 NTU (17% and 52%). This behavior is possible because the water that enters the Medium Gravel Coarse Filter receives the water from the previous filter with less turbidity in the water samples of 100 NTU of initial turbidity than of the water samples of 200 NTU. Nonetheless, when applying the ANOVA, a 0.445 P- value was found, that is, there are no statistically significant differences between turbidity removals of samples. Table 2 shows ANOVA results for the Medium Gravel Coarse Filter.

Table 2 ANOVA between Turbidity Removals in the Medium Gravel Coarse Filter Source Sum of DF Mean F-Value P-Value Squares Square Between groups 153.125 1 153.125 0.670 0.445 Within groups 1374.750 6 229.125 Total (Corr.) 1527.880 7 The final turbidity values, after passing the water samples through the filter, were between 25.5 NTU and 37.8 NTU, for the samples with initial turbidity of 100 NTU and between 20.0 NTU and 60.0 NTU for the samples with initial turbidity of 200 NTU. There was no direct influence of application rates on the turbidity removal in the samples.

3.3. Turbidity Removal in the Slow Sand Filter Turbidity of samples, after passing through the last of the three filters, was between 6.4 NTU and 4.60 NTU for the initial turbidity samples of 100 NTU. It was observed that, at higher application rate in these samples, they a showed lower final turbidity. For initial turbidity samples of 200 NTU, turbidity was reduced to values between 5.8 NTU and 15.90 NTU. Efficiencies achieved in the slow sand filter are shown in Figure 4.

40

30 ) (%

l a

v 20 o m e R 10

0 100 200 Initial Turbidity (NTU) Figure 4. Turbidity Removal in Slow Sand Filter For the samples of initial turbidity of 100 NTU, an average efficiency of 24.5 ± 5.97% was achieved, whereas for the initial turbidity samples of 200 NTU, the average efficiency was 15.5 ± 6.55%, without observing a direct relationship of the application rates on removal efficiencies. A better water quality was observed at the end of the treatment train when the initial turbidity of samples was lower. Table 3 shows the ANOVA made for the results obtained in the Slow Sand Filter.

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Table 3. ANOVA between turbidity removals in the Slow Sand Filter Source Sum of DF Mean F-Value P-Value Squares Square Entre grupos 162.0 1 162.00 4.12 0.0887 Intra grupos 236.0 6 39.33 Total (Corr.) 398.0 7 Since the P-value was greater than 0.05, there is no statistically significant difference between the mean turbidity removal between the samples with initial turbidity of 100 NTU and 200 NTU, with a level of 95% confidence. When analyzing the behavior of the treatment train as a single unit, it was verified that average removal efficiency obtained for the initial turbidity samples of 100 NTU was 94 ± 1.41% and, for the initial Turbidity samples of 200 NTU it was 94 ± 2.16; that is, they are technically the same. Figure 5 shows the behavior of the removal efficiency in the entire treatment plant of the pilot plant.

97

96 ) (%

95 l a v o m

e 94 R

93

92 100 200 Initial Turbidity (NTU)

Figure 5. Total turbidity removal in MSF From the general results, it is possible to affirm that, even though the water turbidity is high, the filtration system in multiple stages guarantees a high efficiency of turbidity removal, even with high application rates (between 100 and 360 m3m-2d-1).

4. DISCUSSION Turbidity is an indirect measure of the amount of colloidal in suspension of clay, , plankton, microorganisms, and others [16], generally associated directly with Total Suspended Solids (TSS) in a water sample [17]. For localized irrigation systems, excessive presence of TSS greater than 50 mg L-1 represents an obstruction risk in the sprinklers [12]. For the results obtained in this study and based on to the relationship found between SST and Turbidity for a river in Colombia proposed by [17], turbidities of 100 NTU and 200 NTU correspond to an approximate concentration of 140 and 560 mg L-1 of TSS, respectively, representing a high risk of obstruction (TSS ≥ 100 mg L-1) according to the ranges proposed by [18]. Once samples are treated in the first coarse filter, the turbidity decreases considerably until reaching between an average risk (50 and 100 mg L-1 of TSS) and a high risk of obstruction, independently of the filtration rate applied, i.e., that it is necessary to continue with the treatment to further reduce the obstruction risk in the nozzles from the sprinklers. The water effluents of medium gravel thick filters showed turbidity between 20 NTU and 60 NTU, corresponding to between 6.0 and 50 mg L-1 in SST, equivalent to a low risk of

http://iaeme.com/Home/journal/IJCIET 303 [email protected] Jhon J. Feria Díaz, Juan P. Rodríguez Miranda and Marinela B. Álvarez Borrero obstruction (SST≤ 50mg L-1). Depending on the selected diameter and type of sprinkler intended to be used in the irrigation system, it is possible to treat the water up to this stage. Finally, the effluents of the slow sand filters show low turbidity (between 4 and 16 NTU), equivalent to concentrations less than 1.0 mg L-1 of TSS for the initial turbidity samples of 100 NTU and between 0.40 and 3.6 mg L-1 of TSS for the initial turbidity samples of 200 NTU. By applying the complete train of treatment and for turbidity of samples smaller than 200 NTU, it is adequate conditions of water quality are guaranteed to avoid the obstruction in the nozzles of the sprinklers of the localized irrigation systems.

5. CONCLUSIONS Use of turbid water in localized irrigation systems represents a high risk of damage to sprinklers, due to obstruction of nozzles by the particulate and colloidal material present in water. It is necessary to remove as much solid material from water through a previous treatment system. Multi-Stage Filtration is an excellent treatment alternative for this type of water, nonetheless, the use of only one part of the MSF treatment train does not guarantee to avoid the risk of obstruction of the nozzles, but it is necessary to bring the mass of water under the three stages making up the treatment so that a low turbidity is obtained that does not represent any obstruction risk of the nozzles of sprinklers of the localized irrigation system. With MSF technology, excellent results are obtained with application rates lower than 360 m3m2d-1 and for raw waters with initial turbidity up to 200 NTU, achieving even turbidity removals up to 94%, regardless of the rates and initial turbidity of water.

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