Removal of total suspended solids from water of superintensive biofloc shrimp farm (Litopenaeus vannamei) by the dissolved air flotation method Galasso, H.L.*,a; Lapa K.R. b; Arana L.V.A. b a UMR
MARbec (IRD, Ifremer, Université de Montpellier, CNRS) at Ifremer, Chemin de Manguelone, Palavas les Flots, 34250, France b Marine Shrimp Laboratory, Department of Aquaculture, Federal University at Santa Catarina (UFSC), Florianópolis, SC, 88061-600, Brazil *
[email protected]
INTRODUCTION
TSS and turbidity had good results with maximum efficiencies of 53.20 %,
The removal of total suspended solids from water is important for a great
44.87 % and 84.28 %, respectively.
management of marine superintensive shrimp farming in biofloc systems (Ray
The removal rates reached high values by applying 5 bar pressure when
et al., 2010). Due of its composition, the biofloc sludge may have lower
referring to phosphate (15.60 ± 5.31%) and applying 20% recirculation rate in
density than water, in consequence, have certain difficulty to settling in
TOCd (17.78 ± 3.91%).
conventional sedimentation tanks. Therefore, dissolved air flotation could be an alternative to suspended solids removal. The aim of this work was to contribute with specifications required for an appropriate design of a dissolved air flotation unit to remove suspended solids in a shrimp Litopenaeus vannamei biofloc system with zero exchange water.
MATERIALS AND METHODS Collected water from tanks of shrimp growed in biofloc system was used in flotation tests. The concentration of total suspended solids (TSS) was
Parameters
Average removal rates ± standard deviation (%)
TOCd BOD5 Phosphate Nitrate Nitrite TSS Turbidity
14.00 ± 5.07 49.78 ± 11.64 14.65 ± 5.62 17.86 ± 8.74 14.55 ± 6.97 40.53 ± 10.79 80.19 ± 8.44
Table 1: Average removal rates ± standard deviation (%) of the analyzed parameters.
maintained between 400 and 600 mg L ¹ (Schveitzer et al. 2013) with the aid of a vertical flow decanter attached to the pond. The experiment was carried
The low removal rates of dissolved parameter (N-NO2, N-NO3, P-PO43 and
out using bench scale equipment (Figure 1). Combinations of saturation
TOCd) were already expected because the flotation process is considered a
pressures
physical process of phase separation (solid-liquid or liquid-liquid) and not
(4.0,
4.5
and
5.0
bar)
and
recirculation
rates
(10, 15 and 20 %) were evaluated. A SAFETY VALVE
premised on the nutrients and dissolved particles removal, except when
MANOMETER
applying chemicals as coagulants and flocculants.
B FLOTATION PITCHER
G
CONCLUSION C
SATURATION CHAMBER COLLECTOR TUBE
H
D WATER SUPPLY
E COMPRESSED AIR
I F
The dissolved air flotation can be used for removing suspended solids in biofloc systems and considering all water quality parameters analyzed were achieved better performance with saturation pressure
DISCHARGE
DISTRIBUTION VALVE
above 4.5 bar and recirculation rate above 15%.
Figure 1: Ilustration of the bench scale equipment used in flotation essays. REFERENCES
RESULTS AND DISCUSSION The use of dissolved air flotation for the removal of suspended solids reached up to 60 %. In addition, this technology showed a potential to remove successfully other variables, such as turbidity and biochemical oxygen demand (Table 1).
Ray, A.J., Lewis, B.L., Browdy, C.L., Leffler, J.W., 2010. Suspended solids removal to improve shrimp (Litopenaeus vannamei) production and an evaluation of a plant-based feed in minimal-exchange, superintensive culture systems. Aquaculture 299, 89-98. Schveitzer, R., Arantes, R., Costódio, P.F.S., do Espírito Santo, C.M., Arana, L.V., Seiffert, W.Q., Andreatta, E.R., 2013. Effect of different biofloc levels on microbial activity, water quality and performance of Litopenaeus vannamei in a tank system operated with no water exchange. Aquacultural Engineering 56, 59-70.
