The following results
were obtained when 5 % crude oil water was treated with C. zizanioides: pH was relatively unchanged in day 2 but slightly
reduced (12 %) in day 6. BOD, COD, PO43-, CN-,
Pb, Fe and Mn were continuously reduced from day 2 (Figure 12) until day 6,
with an average of 77 %, 79 %, 70 %, 83 %, 76 %, 83 % and 55 % respectively. Fe
was below detectable limits in day 4 and 6.
When treated with C. nigritanus, the following
observations
were made: Fe was below detectable limits in day 2, while pH was
relatively unchanged. BOD, COD, NO3-, PO43-,
CN-, Pb, Fe, Mn continuously reduced by 98 %, 80 %, 71 %, 67
%, 82 %, 74 %, 100 % and 61 % respectively from day 2 to day 6 (Figure 13).T-cal values obtained from these parameters when treated with C. zizanioides and C. nigritanus are as follows: pH (-1.942), BOD (-1.109), COD (-2.000), NO3- (-1.941), PO43- (1.525), CN- (0.378), Pb (0.354), Fe (-1.000), and Mn (-3.900) (Table 5).
Effect of Vetiver on Cassava mill Effluent
The following results were obtained when effluent from Cassava mill was treated with C. zizanioides: pH remained unchanged in day 2. BOD, COD, NO3-, PO43-, CN- , Pb, Fe, and Mn decreased continuously from day 2 (Figure 14) until day 6 with average reduction of 71 %, 80 %, 61 %, 60 %, 76 %, 71 %, 85 % and 82 % respectively. Highest reduction of CN was observed in day 4 (97 %), while, Zn and Fe were below detectable limits in day 6.When C. nigritanus was used, the following results were obtained: pH decreased continuously from day 2 (32 %) to day 6 (64%). BOD, COD, NO3-, PO43-, CN-, Pb, Fe, and Mn also decreased continuously by 83 %, 80 %, 69 %, 74 %, 89 %, 77 %, 85 % and 67 % respectively from day 2 to day 6 (Figure 15).
T-cal values obtained from these parameters when treated with C. zizanioides and C. nigritanus are as follows: pH (-0.429), BOD (-1.682), COD (0.054), NO3- (-0799), PO43- (-1.274), CN- (-0.901), Pb (-0.462), Zn (0.383), Fe (-0.094), and Mn (1.931) (Table 5).
|
Parameters
|
Effluent from
Fertilizer plant
|
Effluent from
quarry site
|
Urban irrigation
water
|
Refuse dump
leachates
|
Effluent from
abattoir
|
Crude oil polluted
water
|
Cassava mill
effluent
|
|
pH
|
1.07
|
0.62
|
1.45
|
2.11
|
0.48
|
-1.94
|
-0.43
|
|
BOD
|
-0.12
|
1.18
|
0.55
|
1.73
|
0.66
|
-1.10
|
-1.68
|
|
COD
|
-0.86
|
-2.50
|
-1.22
|
-0.14
|
0.62
|
2.00
|
0.05
|
|
NO32-
|
-1.14
|
0.18
|
1.26
|
1.00
|
2.64
|
1.94
|
0.07
|
|
PO43-
|
0.77
|
-0.77
|
-0.49
|
3.17
|
-0.36
|
1.52
|
-1.27
|
|
CN
|
-
|
-
|
0.71
|
-0.19
|
1.89
|
0.38
|
-0.90
|
|
Pb
|
-
|
0.65
|
-
|
-
|
-
|
0.35
|
0.46
|
|
Zn
|
2.48
|
-1.00
|
1.89
|
0.62
|
-1.00
|
-
|
0.38
|
|
Fe
|
-0.03
|
2.23
|
0.44
|
0.23
|
-0.83
|
1.00
|
-0.09
|
|
Co
|
1.00
|
-1.00
|
1.00
|
1.00
|
-
|
-
|
1.93
|
|
Cd
|
1.00
|
-
|
-
|
-
|
-0.61
|
-
|
-
|
|
Hg
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Mn
|
1.06
|
0.08
|
0.99
|
-
|
-
|
-3.90
|
-
|
|
As
|
1.00
|
0.86
|
1.96
|
-
|
-
|
-
|
-
|
|
Ni
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
|
Cu
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
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