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Flow rate variation and biological agents that obstruct drippers of swine effluent.


The water scarcity and pollution problems increase worldwide, indicating that the use of wastewater for irrigation purposes minimizes the current imbalance between supply and demand for public water supply (Puig-Bargues et al., 2010; Song et al., 2017).

In this context, emitters clogging has become one of the main obstacles of drip irrigation in the application of effluents. Several studies with wastewater types have shown that drip obstruction affects both the useful life and the hydraulic performance of the application systems (Liu & Huang, 2009; Eroglu et al., 2012; Li et al., 2012; Batista et al., 2013; Silva et al., 2013; Batista et al., 2014; Oliver et al., 2014; Batista et al., 2016; Marques et al., 2016; Zhou et al., 2016; Batista et al., 2018).

In the wastewater it is possible to find several types of biological agents that can lead to drip obstruction, such as bacteria and fungi (Sahin et al., 2005; Dazhuang et al., 2009), algae (Batista et al., 2009; Batista et al., 2015), protozoa and worms (Mesquita et al., 2016a, b).

The drippers obstruction lead to lower flow rate (Batista et al., 2014; Fernandes et al., 2014) and uneven application of the effluent (Yan et al., 2010; Batista et al., 2013; Batista et al., 2018) in drip irrigation systems.

In order to detect the clogging of the emitters, there are several indicators of hydraulic performance, however the coefficient of variation of the flow is an indicator that has been used in several studies with wastewater (Silva et al., 2013; Batista et al., 2016; Mesquita et al., 2016b).

According to the exposed, the objective of this study was to evaluate the variation of the coefficient of flow variation, as well as to identify the main biological agents that cause obstruction in dripping units operating with times of swine effluent and public water supply.

Materials and Methods

The experiment was performed at the Pilot-unity of treatment and localized application of swine residual water (UTARS) of the Federal University of Vicosa (UFV) in Minas Gerais State, Brazil (20[degrees]46'11.25" S and 42[degrees]51'44.96" O) from August 2nd to September 10th, 2006.

The experiment was settled in subdivided plots, being the main plots the times of swine effluent (ES) and public water supply (AAP) application (U1 - 1h of EF plus 3h of AAP; U2 - 2h of EF plus 2h of AAP; U3 - 3h of EF plus 1h of AAP, U4 - 4h of ES), being the secondary plots the drippers types (G1--not self-compensating dripper of 2.0 L [h.sup.-1]; G2--not self-compensating dripper of 1.7 L [h.sup.-1]; and G3--self-compensating dripper of 3.6 L [h.sup.-1]) and in the tertiary plots the times of evaluations (0, 20, 40, 60, 80, 100, 120, 140 and 160h) of the coefficient of flow variation (FCV) in a completely randomized design (CRD) with three repetitions.

For this, an experimental bench was settled, consisting of a public water supply reservoir with 5.6 [m.sup.3] (1), a swine effluent reservoir with 7.0 [m.sup.3] (2), two pump sets of 3 CV each (3), one disc filter with apertures of 130 [down arrow]m (4A), one sieve with a screen with openings of 47 [down arrow]m (4B), a main line in 32 mm PVC (5), a branch line in 32 mm PVC (6), four pressure regulating valves of 105 kPa (7), dripper units operating with effluent application times of swine effluent -ES and public water supply - AAP (U1 - 1h of EF plus 3h of AAP, U2 - 2h of EF plus 2h of AAP, U3 - 3h of EF plus 1h of AAP, U4 - 4h of ES) and 12 drip subunits equipped with emitters G1, G2 and G3, as shown in Figure 1.

In each drip subunit were installed nine lateral lines in level, being three of each type of emitter with 18 m of length. The technical characteristics of the emitters tested with swine effluent application times and public water supply are shown in Table 1.

In these, 22 emitters were marked for flow measures, according to the collection of the applied volume during three minutes, according to the recommendations of NBR ISO 9261 (ABNT, 2006) for tests with drippers. Then, each emitter flow (qi in L [h.sup.-1]) were calculated using the following equation (1):

[q.sub.i] = [v/1000 t] 60 (1)

In which:

v - Volume of each effluent collected in each emitter, in mL; and

t - time of effluent collection for each emitter, in minutes

With the emitters flow it was determined the coefficient of flow variation (FVC in %) of the drippers subunits, using the equation 2 of NBR ISO 9261 (ABNT, 2006), for each 20 hours of operations until 160 hours, according to Silva et al., (2013), who detected levels of obstruction in drippers units that use waste water from cashew nuts at the same time of evaluation.

FVC = 100 [S[D.sub.q]/q] (2)

In wich:

SDq - Standard deviation of the emitters flow for each dripper unit, in L [h.sup.-1]; and

- Mean flow for the emitters in each dripper unit, in L [h.sup.-1].

The FVC values were classified according to ASAE EP 405 (Asabe, 2003), where the following values are suggested: less than 10%, good (G); between 10 and 20%, regular (R); and more than 20%, unacceptable (U).

In Table 2 is possible to observe the mean value and the standard deviation of the physical-chemical characteristics of the swine effluent (ES) and the public supply water (AAP) applied by the dripper subunits.

During the experimental period, ES samples were collected on every 20 h of operation of the drip subunits, which were then preserved in an isothermal box at 4[degrees]C and sent to the laboratories of the Departments of Animal Biology and Plant Biology of the Federal University of Vicosa (UFV). In these samples the presence of fungi, protozoa, cyanobacteria, zooplankton and phytoplankton were identified, as well as their frequency of occurrence, through the microscopic examination of the collected samples.

After 160 h of operation of the drip subunits, samples of the material that caused the emitters obstructions were collected and immediately conditioned in a sterilized container, being preserved in an isothermal box at 4[degrees]C, until the arrival at the laboratories of the Departments of Plant Biology, Animal Biology and Microbiology of the UFV and the Laboratory of Biological Processes of the Department of Hydraulics and Sanitation of USP, aiming to identify the agents that cause microscopic clogging using objective of 100, ocular of 10 and zoom of 1.25.

Results and Discussion

According to the variance analysis, the interaction N x G x T was significant at 1% of probability for the variable FCV, with CV of the tertiary plots of 32%. Similar results were observed by Silva et al. (2013) studying dripping unities using cashew nuts production wastewater, with CV of 29% (Table 3).

In Table 4, the mean values of FCV for the drip type factor were presented within each operating time level and each level of application time of swine effluent and public water supply. It was verified, in this table, that there was no effect of the effluent and water application times on the FCV, for each type of dripper, up to the operating time of 60 h; this result differs from that obtained by Mesquita et al. (2016b) that showed a significant reduction of FCV, from 40 h of application of percolate of diluted landfill, in the dripper unit with a non-compensating emitter of 1.65 L [h.sup.-1].

Using the classification of ASAE EP 405 (Asabe, 2003), it was shown that the value of FCV was classified as good (<10%) throughout the experimental period only in the drip subunits equipped with emitters G2 and G3 of U1 and in the dripping subunits G1 and G3 of U4, evidencing that the susceptibility to clogging is related to the constructive characteristics of the emitters and the quality of the applied fluid; however, at 160 h, the drip subunits G1, G2 and G3 presented FCV classified as unacceptable (> 20%) for U2 and U3, where the constructive characteristics of the emitters and the quality of the applied fluids contributed to obstruction of the emitters. It was also noted in Table 4 that the emitter obstruction started at 80h in the G4 drip subunit of U4, where FCV was classified as regular (10% < FCV <20%).

These results are in accordance with those found by Mesquita et al. (2016b) in dripping units by applying percolated landfill diluted for 160 h, where the not self-compensating dripper of 1.65 L [h.sup.-1] resulted in FCV also classified as unacceptable, due drippers obstruction.

Comparing the means of the FCV variable followed by at least one same capital letter in the columns of Table 4, it was found that: at U1 level, from 120 h, the FCV of the subunit with G1 dripper differed from the FCV of the subunits with G2 and G3 drippers; at the U1 level, from 100 h, the FCV of the G1 drip subunit differed from the FCV of the subunits with G2 and G3 drippers; at U3 level, the FCV of the G1 drip subunit differed from the FCV of the subunits equipped with the G2 and G3 drippers, at the 80, 100 and 120 h operating times, while the FCV values of the G1, G2 and G3 drip subunits differed between them, in the operating times of 140 and 160 h; and at U4 level, from 100 h, the FCV of the subunits with G1 and G3 drippers differed from the FCV of the subunit provided with drip G2. These results differ from those presented by Silva et al. (2013), where the average FCV values of the dripper unit with non self-compensating emitter differs from the FCV of the other dripper units with self-compensating emitters, after 20h operation with cashew nut residual water under the service pressure of 70 kPa.

Comparing the means of the FCV variable followed by at least one same lowercase letter in the lines of Table 4, it was observed that: at the 80 h time, the FCV of the G1 subunit submitted to the U1 level differed from the FCV of the subunits submitted at levels U1, U2 and U4; in the operating time of 100 h, the FCV of the subunits equipped with the G1 drippers submitted to the U1 and U4 levels differed from the FCV of the subunits submitted to levels U2 and U3, the FCV of the subunits with drip G2, submitted to the U1 level, differed of FCV of the subunits submitted to levels U2, U3 and U4, and the FCV of the subunits with G3 dripper, submitted to level U1, differed from the FCV of the subunit submitted to level U3; in the operating times of 120, 140 and 160 h, the FCV values of the subunits equipped with the G1 and G2 drippers, submitted to levels U1, U3 and U4, were different, while the FCV of subunits with G3 dripper, submitted to levels U1 and U4, differed from the FCV of subunits submitted to levels U2 and U3.

In Table 5, the biological groups present in swine wastewater are shown, according to the time of operation of the drip subunits, identified by optical microscopy.

The effluent of the phytoplancton was represented by the groups Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Cryptophyta and Dinophyta. In the primary domestic wastewater, Batist et al. (2015) observed other groups of phytoplancton, such as Chlorella, Scenedesmus, Chaetophora and Navicula. The group Bacillariophyta was observed for all times of evaluation, bein mainly represented by Diatomaceous. The groups Chlorophyta and Euglenophyta were not observed, except for the periods of 20 and 120 h, respectively. The group Cyanophyta was observed in the periods of 40, 80 and 100 h, being mainly represented by Cyanobacterias. The group Cryptophyta was observed in the periods of 20 e 60 h, while the Dinophyta group was only observed for the period of 40h. The lack of dissolved oxygen in the effluent avoided the developent of zooplancton groups such as Rotifera, Cladocera and Copepoda, commonly observed in secondary domestic effluents.

The biological groups bacteria, fungus and protozoa were also identified in the effluent throughout the testing period. In the study developed by Sahin et al. (2005), it was observed problems of drippers clogging due to the formation of mucilage by the activity of bacteria, fungi and protozoa.

Microscopic analysis of biofilms, performed to characterize the biomass present in each subunit (Figure 2), presented different phase contrast morphologies. In all biofilms, the predominant microorganisms were curved bacilli (probably sulphate-reducing bacteria). bacilli in pairs, bacillus cocci, filaments, filamentous bacteria (similar to Methanosaeta) and diatoms. Moraes & Paula Junior (2004), studying swine effluent, found the predominance of curved bacilli, straight bacilli and cocci bacilli in the biofilm formed inside reactors. Luiz (2007) identified bacilli, bacillus cocci, filaments and bacteria similar to Methanosaeta and Methanosarcina in the biofilm formed in reactors operating with coffee production wastewater.

Evaluating the culture media, it was observed population level of bacteria that could cause drippers clogging, as shown in Table 6. The population levels of bacteria in the U1, U2, U3 and U4 biofilms were 8.5 x 105, 1.8 x [10.sup.6], 1.9 x [10.sup.6] and 1.1 x [10.sup.6] CFU [ml.sup.-1], respectively. According to reports by Nakayama et al. (2006), the genera Enterobacter, Pseudomonas and Clostridium bacteria can cause serious obstruction problems in drippers.


The obstruction levels of the emitters were lower when the times of application of water of public supply were also lower.

The coefficient of variation of the flow was effective in detecting the clogging of the emitters, evidencing that the construction characteristics and the times of application of swine effluent and public water supply interfere in this process.

The main biological agents responsible for drip clogging were algae (Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Cryptophyta and Dinophyta), bacteria (Enterobacter, Pseudomonas and Clostridium), fungi and protozoa.


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Rafael Oliveira Batista (1*), Rubens Alves de Oliveira (2), Maria Elidayane da Cunha (1), Rutilene Rodrigues da Cunha (1), Jeane Cruz Portela (1), Marcelo Tavares Gurgel (1)

(1) Federal Rural University of Semi-Arido, Brazil

(2) Federa University of Vicosa, Brazil

(*) Corresponding author, e-mail:

Received: 07 April 2017

Accepted: 09 March 2018

DOI: 10.14295/CS.v9i2.2658
Table 2. Mean and standard deviation for the physical-chemical
characteristics of swine effluent (ES) and public water supply (PSA)
applied by dripper subunits.

Fluids  Temperature        DB[O.sub.5.sup.20]  DQO
        [degrees]C         mg [L.sup.-1]       [mmol.sub.c] [L.sup.-1]

ES      19.02[+ or -]0.66  602[+ or -]252      1228[+ or -]635
AAP     19.28[+ or -]0.48  NR                  NR

Fluids  OG            Alc             [Na.sup.+]
                                      [(mmolc L-1).sup.0.5]

ES      27[+ or -]25  1752[+ or -]99  2.14[+ or -]0.20
AAP     NR            NR              0.34[+ or -]0.10

Fluids  RAS

ES      1.10[+ or -]0.13
AAP     0.56[+ or -]0.15

Note: DB[O.sub.5.sup.20]--Oxygen biochemical demand t 5 days of
incubation at 20 [degrees]C. DQO--Chemical demand of oxygen; OG--Oil
and fat; Alc--Alkalinity at pH 4.3; [Na.sup.+] - Sodium; RAS--Sodium
absorption ratio; NR--Not realized.

Table 3. Variance analysis for the FCV variable, in a scheme of
subdivided plots.

Source of variation                      Degree of freedom
                                             liberdade      Mean square

Times of effluent and water application          3          4266 (**)
Residue (a)                                      8            81
Dripper type (G)                                 2          1357 (**)
N x G                                            6           854 (**)
Residue (b)                                     16            53
Time of operation (T)                            8          5416 (**)
N x T                                           24           762 (**)
G x T                                           16           253 (**)
N x G x T                                       48           143 (**)
Residue (c)                                    192            18
CV (%) main plots                                             68
CV (%) secondary plots                                        58
CV (%) tertiary plots                                         32

(**) F significant at 1% of probability. CV - Coefficient of variation.

Table 4. Mean values for FCV (%) for the factor dripper type for each
level of time of application of the effluent and water, with the
respective ASAE EP 405 classification (Asabe, 2003).

Operation time  Drippers  Times of application of swine effluent and
                                  water from public supply (*)
     (h)                      U1          U2                 U3

                  G1       2.37Aa (G)   2.24Aa (G)        2.04Aa (G)
       0          G2       1.78Aa (G)   1.55Aa (G)        1.59Aa (G)
                  G3       2.85Aa (G)   3.45Aa (G)        3.47Aa (G)
                  G1       2.12Aa (G)   1.94Aa (G)        2.24Aa (G)
      20          G2       1.58Aa (G)   1.68Aa (G)        1.70Aa (G)
                  G3       4.08Aa (G)   3.89Aa (G)        3.97Aa (G)
                  G1       2.18Aa (G)   2.47Aa (G)        3.54Aa (G)
      40          G2       2.08Aa (G)   2.55Aa (G)        2.47Aa (G)
                  G3       3.47Aa (G)   4.54Aa (G)        6.27Aa (G)
                  G1       2.92Aa (G)   3.35Aa (G)        4.47Aa (G)
      60          G2       1.93Aa (G)   2.29Aa (G)        2.21Aa (G)
                  G3       4.11Aa (G)   4.64Aa (G)        6.18Aa (G)
                  G1       3.64Ab (G)   8.82Ab (G)       22.55Aa (U)
      80          G2       2.17Aa (G)   5.86Aa (G)        5.75Ba (G)
                  G3       5.77Aa (G)   6.82Aa (G)        9.44Ba (G)
                  G1       9.37Ab (G)  26.67Aa (U)       30.73Aa (U)
     100          G2       3.26Ab (G)  13.90Ba (R)       17.21Ba (R)
                  G3       4.81Ab (G)  10.09Bab (R) (R)  15.11Ba (R)
                  G1      17.46Ab (R)  55.40Aa (U)       47.78Aa (U)
     120          G2       4.38Bc (G)  25.93Bb (U)       26.94Bb (U)
                  G3       6.70Bb (G)  27.82Ba (U)       28.06Ba (U)
                  G1      20.47Ab (U)  69.32Aa (U)       62.75Aa (U)
     140          G2       5.64Bc (G)  32.80Bb (U)       43.13Ba (U)
                  G3       5.58Bb (G)  38.32Ba (U)       32.40Ca (U)
                  G1      22.45Ab (U)  77.71Aa (U)       67.67Aa (U)
     160          G2       7.94Bc (G)  37.46Bb (U)       50.65Ba (U)
                  G3       6.82Bb (G)  45.11Ba (U)       37.42Ca (U)

Operation time  Times of application of swine effluent and
                        water from public supply (*)
     (h)          U4

                 2.03Aa (G)
       0         1.45Aa (G)
                 4.48Aa (G)
                 2.62Aa (G)
      20         1.49Aa (G)
                 4.30Aa (G)
                 7.93Aa (G)
      40         5.38Aa (G)
                 3.41Aa (G)
                 5.35Aa (G)
      60         3.61Aa (G)
                 4.88Aa (G)
                 4.36Ab (G)
      80        12.29Aa (R)
                 3.75Aa (G)
                 5.75Bb (G)
     100        16.62Aa (R)
                 5.00Bab (G)
                 3.87Bc (G)
     120        37.20Aa (U)
                 3.73Bb (G)
                 5.14Bc (G)
     140        29.26Ab (U)
                 3.79Bb (G)
                 7.17Bc (G)
     160        35.61Ab (U)
                 4.43Bb (G)

(*) Means followed for at least one uppercase letter in the columns for
each operation time and lowercase letters in lines for each water
amount are not different, at 5% of probability, according to Tukeys
Test. Classification of ASAE EP 405 (Asabe, 2003): G--Good, R--Regular
and U--Unacceptable.

Table 5. Characterization of the biological groups presented in swine
wastewater according to the operation periods of the drip units
identified using the optical microscopy.

Groups           Observed frequencies for the operation periods (h)
                 0     20    40    60    80    100   120   140   160

Bacillariophyta  ++    ++++  ++++  ++++  ++++  +++   ++++  +++   +++
Chlorophyta      ++++  -     ++    +++   +++   +++   +++   +++   ++++
Euglenophyta     +++   +++   +++   ++    +++   ++++  -     ++++  +++
Cyanophyta       -     -     +++   -     ++    ++    -     -     -
Cryptophyta      -     ++    -     +++   -     -     -     -     -
Dinophyta        -     -     +++   -     -     -     -     -     -
Rotifera         -     -     -     -     -     -     -     -     -
Cladocera        -     -     -     -     -     -     -     -     -
Copepoda         -     -     -     -     -     -     -     -     -
Bacteria         ++++  ++++  ++++  ++++  ++++  ++++  ++++  ++++  ++++
Fungi            +++   +++   +++   +++   +++   +++   +++   +++   +++
Protozoa         +++   +++   +++   +++   +++   +++   +++   +++   +++

Range: (++++) predominant, (+++) frequent, (++) less frequent and (-)
not observed.

Table 6. Characterization of the bacteria of the biofilm formed in the
subunits submitted to the levels U1, U2, U3 and U4.

Bacteria                                     Water proportion
                                         U1                U2

Bacteria population
(UFC [mL.sup.-1])                  8,5 x [10.sup.5]  1,8 x [10.sup.6]
Enterobacter (UFC [mL.sup.-1])     2,0 x [10.sup.3]  7,5 x [10.sup.3]
Pseudomonas (UFC [mL.sup.-1])      3,5 x [10.sup.3]  5,5 x [10.sup.3]
(*) Clostridium (UFC [mL.sup.-1])  1,0 x [10.sup.3]  < [10.sup.2]

Bacteria                                   Water proportion
                                         U3                U4

Bacteria population
(UFC [mL.sup.-1])                  1,9 x [10.sup.6]  1,1 x [10.sup.6]
Enterobacter (UFC [mL.sup.-1])     4,5 x [10.sup.3]  2,0 x [10.sup.3]
Pseudomonas (UFC [mL.sup.-1])      1,0 x [10.sup.4]  1,0 x [10.sup.4]
(*) Clostridium (UFC [mL.sup.-1])  6,5 x [10.sup.3]  < [10.sup.2]

Note: UFC = colony forming units. (*) Sulphite reducers Clostridium
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Title Annotation:Article
Author:Batista, Rafael Oliveira; de Oliveira, Rubens Alves; da Cunha, Maria Elidayane; da Cunha, Rutilene R
Publication:Comunicata Scientiae
Article Type:Report
Date:Apr 1, 2018
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