Table 3.10
Parameters, sub-index and aggregation functions, weights, and quality classification procedure of the different proposed physico-chemical indices
for the evaluation of water quality
Index
Parameter
Application limits
Sub-index function
Weight
Aggregation function
Water-quality
classification
ISQA
Temperature (_C)
20
IT
¼ 1 -
ISQA
¼ I
T I
TOC
þ I
SS
þI DO
þ I
COND
Þ
ð
0 (minimum
quality)
– 100
(maximum quality)
>20
IT
¼ 1–(T–20)*0.0125
Total organic carbon
5
ITOC
¼ 30–TOC
(mg/L)
12
! TOC > 5
ITOC
¼ 21–
(0.35*TOC)
>12
ITOC
¼ 0
Suspended solids
100
ISS
¼ 25–(0.15*SS)
(mg/L)
250 > SS > 100
ISS
¼ 17–(0.07*SS)
>250
ISS
¼ 0
Dissolved oxygen
<10
IDO
¼ 2.5*DO
(mg/L)
!10
IDO
¼ 25
Conductivity (lS/cm)
4000
ICOND
¼ (3.6-log
COND)*15.4
>4000
ICOND
¼ 0
Pesce and
Wunderlin
Dissolved oxygen
(mg/L)
1 2
! DO>1
IDO
¼ 0
–IDO ¼ 10
WQI
min
1
3 :
P
3
i¼1 I
i
0 (minimum
quality)
– 100 (maximum quality)
3
! DO>2
IDO
¼ 20
3.5
! DO>3
IDO
¼ 30
4
! DO>3.5
IDO
¼ 40
5
! DO>4
IDO
¼ 50
6
! DO>5
IDO
¼ 60
6.5
! DO>6
IDO
¼ 70
7
! DO>6.5
IDO
¼ 80
82
H. A. Aziz et al.