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performed at probabilities of 0.05 or less level of significance to determine whether
significant differences existed among treatment means.
6.3 RESULTS AND DISCUSSIONS
6.3.1 PERFORMANCE OF FILTRATION SYSTEM
Filtration efficiency for WW filtration by filter F1, F2, and their combinations (F3)
during the experiments are presented in Table 1. Filtration efficiency 64.3±29.8% for
turbidity and 19.21±19.3% for total solids were achieved with F3. Negative filtration
efficiency was observed for TS and Mg (column F1 in Table 1). The value for TS was
−3.08±21.5. It shows the variation in filtration efficiency from −24.58% to 18.42%.
This was due to variation in amount of TS available in WW and as testing was done
for the same filter without cleaning. Sometimes, if filter was not cleaned and WW
containing lower TS was passed through F1 then TS available in F1 came out with
WW. Thus the amount of TS available in WW, was higher and resulted in negative fil-
tration efficiency using Eq. (1). Similar reasoning can be made for negative filtration
efficiency in case of Mg through F1. Negative filtration efficiency was also observed
by Duran-Ros et al. [12] with screen and disk filter for turbidity and TS. Duran-Ros
et al. [12] observed 12.42±23.53% filtration efficiency for turbidity and 8.47±18.36%
for total suspended solids (TSS) with combination of screen and disk filter at 500 kPa
inlet pressure. The presence of less organic material after the sand media filters was
also observed by Tajrishy et al. [29] and can explain the lower fouling of emitters
protected by this type of filter [12]. Combination filter and lower inlet pressure caused
more effective filtration. Combination filter gave best results for removal of bicarbon-
ate (HCO 3 ) and carbonate (CO 3 ) in comparison to F2. However, filtration efficiency
obtained through F1 was close to F3. Therefore, F1 and F3 are not significantly differ-
ent (P=0.387) as shown in Table 1.
TABLE 1
Filtration efficiency and P value for difference in filtration of different water quality
parameters.
Quality
parameter
Filtration efficiency (%)
(mean and SD)
P value for LSD
at α = 0.05
F1
F2
F3
F1-F2
F1-F3
F2-F3
Turbidity
51.1±37.5
63.9±30.6
64.3±29.8
0.058
0.023
0.388
Total Solids, TS
-3.08±21.5
2.66±18.2
19.21±19.3
0.540
0.089
0.191
Ca
8.79±2.34
1.65±12.4
12.1±27.2
0.626
0.816
0.492
Mg
-2.53±6.88
6.38±1.6
7.33±4.16
0.017
0.012
0.696
CO 3
6.47±3.25
15.7±14.2
16.36±13.6
0.163
0.141
0.908
HCO 3
19.3±12.3
12.6±10.7
21.3±6.91
0.034
0.387
0.092
Removal of turbidity was highest with combination fi lter (F3) but it was close to
F2. It can be seen that F1-F3 were signifi cantly different ( P =0.023) but F2-F3 were
 
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