International Journal of Aquaculture, 2013, Vol.3, No.10, 43
-
48
http://ija.sophiapublisher.com
43
processes (Yusuff and Sonibare, 2004; Roy et al., 2010).
Particularly dyeing process contributes high concentration
of chromium, copper, mercury, and zinc, and could
have high level of colour, toxicity and turbidity
(
Kabir et al., 2002; Zinabu and Zerihun, 2002;
Moreira et al., 2004; Roy et al., 2010). As mentioned
by Moreira et al., (2004), up to 50% of dyes are lost as
waste substance in the effluents, and has serious
negative impact on aquatic biota, and change the
aesthetic value of the environment (Gomez et al., 2008;
Aslam et al., 2004). Thus, the effects of waste
substances from textile industries are therefore mainly
depend on the amount of discharged effluents to the
receiving water bodies.
Due to the fact that textile effluent has such characteristics,
it should be discharged into a well-designed treatment
plant before being released to the surrounding
environment (Kabir et al., 2002; Movahedian et al., 2005).
Physiochemical parameters are generally used to
evaluate the quality of such types of textile effluent.
However, it is not enough to determine the impact of
pollution; thus, inclusion of toxicity evaluation is an
important as toxicity evaluation provides a complete
response of test organisms in a cumulative way
(
Tisler and Koncan, 1999; Ogugbue and Oranusi, 2005;
Soni et al., 2006; Dahunsi and Oranusi, 2012). It is also
useful to determine short term and long term impacts
of wastewater to the receiving water bodies as well as
the safe concentration of wastewater to be discharged.
Hawassa textile industry, established in 1989, is one of
the oldest textile industry which discharges large
amount of wastewater to the surrounding wetland and
then into Lake Hawassa via Tikur Wuha River after
treatment in its biological lagoons (treatment plant).
Even though, the industry has biological lagoons
(
treatment ponds), nearly all its biological, chemical
and physical characteristics of the surrounding water
bodies are unchanged as compared with the treatment
ponds (Zinabu and Zerihun, 2002; Birnesh et al
.
, 2007).
The objective of this study was therefore, to evaluate
the efficiency of Hawassa Textile Effluent plant using
Nile tilapia:
Oreochromis niloticus
as test organism.
1
Results
1.1
Physicochemical Parameters
The mean values of water quality parameters such as
pH, conductivity, dissolved oxygen concentration and
temperature are summarised in Table 1. Dissolved
oxygen concentration was decreased as effluent
concentration increased and had inverse relationship,
while pH and conductivity were increased and thus
exhibited a direct relationship with effluent concentration
(
Figure 1, Figure 2 and Figure 3). These imply that the
recorded water quality parameters were affected by
effluent concentration.
Table 1 Physicochemical parameters of textile effluent concentration
Effluent concentration Intel of biological lagoon
Outlet of biological lagoon
DO (mg/l) pH Conductivity
(
µs/cm)
Temperatur (
℃
)
DO (mg/l) pH Conductivity
(
µs/cm)
Temperatur (
℃
)
0%
7.3
8.8 745
22.1
7.5
8.3 735
22.1
10%
6.0
8.5 780
22.0
6.7
7.8 750
22.3
20%
4.7
8.4 794
22.3
6.4
7.5 784
22.0
30%
3.6
8.2 809
22.0
6.1
7.3 889
22.5
40%
3.3
7.7 831
22.2
5.3
7.1 812
22.2
100%
2.5
6.8 975
22.3
4.1
6.8 942
22.5
Figure 1 Trend of DO concentration with respect to effulent concentration