International Journal of Aquaculture, 2013, Vol.3, No.21, 117
-
125
http://ija.sophiapublisher.com
124
5.1.3
Treatment Process
Water from the overhead tank (inlet water) entered the
pond where fishes are kept and then flowed into the
treatment tank as waste water. As waste water flowed
through biobrush, bioblocks, maifan stone, coral sand,
ceramic ring and activated carbon it is filtered. Solar
powered pump water and electric powered pump
water were then collected. Water lastly flowed into the
UV light compartment where it was disinfected (UV
treated water). After the waste water had passed
through the treatment tank, the treated water was air
lifted into the culture tank for use by the fish and
recirculated back again into the filter again for
purification.
5.2
Sample collection
Three critical points of sample collection were
focused on incoming and outgoing points of the fish
culture tank and outlet of the filter tank. The outlet is
important because it indicates the effectiveness of UV
light, specifically the ability to disinfect the water so
that pathogenic bacteria is killed by ultra violet rays
after the water has been conditioned. One sample each
was collected from the incoming and outgoing points
of the fish culture tank while 2 samples were collected
from the outlet of the filter tank i.e. from the solar
powered pump and electric powered pump. They were
collected into already properly washed two litres
plastic containers. The containers were labeled and
stored in the laboratory refrigerator prior to analysis.
The water samples for biochemical oxygen demand
were collected in properly washed glass bottles of
120
ml capacity with glass stoppers labeled and stored
in the laboratory refrigerator prior to analysis.
5.3
Determination of Relevant Parameters for
Recirculating System
Temperature was determined using mercury-in-glass
thermometer (British standard BS593). pH was
determined using a ATC pH meter, Calcium carbonate
(
CaCO
3
),
nitrate, nitrite, and ammonia were
determined by using water Analysis Kit by Hague
made in Canada (ASTM, 2008),
dissolved oxygen
were determined in situ using Labtec oxygen meter.
Microbial analysis was carried out using the
MaConkey agar plate method as described below.
Four water samples were cultured using nutrient agar:
Petri dishes were used for the culturing. Water samples
were diluted ten times from 10
-1
to 10
-10
. 50
mL of
diluted samples spread on the plate and incubated.
Colony count was done on plates after incubation and
total CFU calculated. Isolation was carried out using
the Mac Conkey agar plate; 50μC≥0.05ml was used.
Average micro agar/ml was counted and colony
forming unit (CFU) recorded (Monica, 1984).
Biochemical oxygen demand determination was
carried out using 250 ml of the sample was measured
into BOD bottle. 1 cm
3
of MnSO
4.
H
2
O to the sample
already measured. 1 cm
3
sodium hydroxide and
potassium Iodide were added. Then the sample was
stoppered and shaken thoroughly by inverting several
times and later allowed to settle for observation of
precipitate of magnesium hydroxide. 1.5 cm
3
of
concentrated H
2
SO
4
was added then restoppered and
mixed thoroughly to dissolve the
precipitate. 25 mL
was withdrawn from the solution into a titrating flask.
1
ml potassium iodide and concentrated H
2
SO
4
less
than 1ml were added into the solution. A little quantity
of starch indicator was added into the solution and
titrated against sodium thiosulphate (Na
2
S
2
O
3
.5
H
2
O).
The colour changed from blue to colourless. Sample
was kept at 20
℃
in the dark with test tube stoppered
to prevent photosynthesis
(
and thereby the addition
of oxygen) for five days, and the dissolved oxygen
was measured again. The difference between the
final DO and initial DO is the BOD. This was done
for five days intervals (Lenore et al
.
, 1999).
In
calculating, 1 cm
3
of 0.1M Na thiosulphate is equal
to 0.4 mg of oxygen. The value would be multiplied
by 0.4 mg out of 250 mls if used 25ml then multiply
by 40 (Monica, 1984).
Acknowledgements
Authors are thankful to the former Director of Energy Research Centre, Prof.
O. U. Oparaku for his assistance in providing solar panels, inverter and
technical supports. Also, I thank Mr. D. O. Aneke and Mr. Christian Eze of
the National Centre for Energy Research, UNN for their help in installation
of solar energy devices and Mr. Chinedu Nzelu for supplying all the
materials needed for the recirculating system during this work.
References
ASTM, 2008, Standard guide for use of test kits to measure inorganic
constituents in water, American Society for Testing Materials Inc., West
Conshohocken, PA, USA,
http://www.astm.org/Standards/D5463.htm
Boyd C. E., 1982, Water quality management for fish pond culture, Elsevier
Scientific Publishing Company, Amsterdam, the Netherland, pp.318
Boyd C. E., and Watten B. J., 1989, Aeration systems in aquaculture, CRC
Critical Reviews in Aquatic Sciences, 1: 425 - 472
Carole R. E., and Nathan S., 2002, Costs of Small-Scale Catfish Production,
Southern Regional Aquaculture Centre (SRAC) Publication No.1800
Colt J., Orwicz K., Bouck G., 1991, Water quality considerations and criteria