UNIVERSIDADE FEDERAL DE SANTA CATARINACENTRO TECNOLÓGICO
PROGRAMA DE PÓS-GRADUAÇÃO EM ENGENHARIA AMBIENTAL
REUSE OF DOMESTIC EFFLUENT THROUGH PELETIZED DUCKWEEDS WITH RED TILAPIA
FARMING
Flávia Tavares, Dra. OEI consultant at MPA
Rodrigo Roubach, PhDProject Manager/MPADiógenes Lemainski
OEI consultant at MPAFlávio Rubens Lapolli, Dr.
UFSC
The reuse of the effluent from duckweed based pondsin fish farming
It can reduce the environmental impact caused by the domestic wastewater treatment
Produce high protein biomass
The present study aimed to evaluate the sustainability of duckweed-based-ponds as a tertiary
treatment
Considering pollutants removal
And its use as a feed source in tilapia production
Objectives
Wastewater Treatment Plant Florianópolis
Reuse system
Facultative pond I
Anaerobic pond
Facultative pond II
Facultative pond III
The effluent used in the Reuse System was pumped from the last Facultative Pond (Facultative pond III).
Methodology
Duckweed-fish reuse pilot system
The Reuse System was composed by the duckweeds treatment and fish production tanks during a 83
days trial
Duckweeds treatment Fish production tanks
Effluent sampling and physical-chemical analysis from duckweeds and fish tanks were conducted weekly.
Variables analyzed were: TAN (NH3 + NH4+), nitrite (NO2-), nitrate (NO3-), total nitrogen (TN), Chemical oxygen demand (COD), Biochemical oxygen demand (BOD), Suspended, total and fixed solids, Orthophosphate,
Turbidity, and Total and Fecal coliforms
Also, pH, alkalinity, conductivity, temperature, dissolved oxygen, and transparency were recorded weekly. All
analyses followed APHA (1998) recommendations
.Fingerlings in each experimental unit were weighted every two weeks during experimental period for weight gain (final weight –
initial weight), feed conversion (total dry feed fed /total wet weight gain), and specific growth rate (100 x Ln final average
weight – Ln initial average weight/days) estimation.
Duckweed average production registered in the present study could reach up to 31.1 t/ha/year (dry matter), with a crude protein
content of 39.9%.
The results obtained shown that duckweeds presented a satisfactory pollutants removal, mainly for Turbidity
(54.5%), Suspended Solids (44.4%) and COD (39.4%), reaching adequate criteria for aquaculture (Nitrite, Nitrate
and COD concentrations under acceptable levels).
However, an increase in retention time could improve plant performance.
Results
Table 1. Final Weight, Feed Conversion Rate and Specific Growth Rate comparison between fish fed peletized duckweed and commercial ration.
VariableDiet P value
Dried duckweed Commercial ration
Final Weight (g) 25.9 a 32.06 a 0.0805
Feed Conversion Rate 1.61 a 1.59 a 0.2515
Specific Growth Rate 5.28 a 5.56 a 0.1459
Considering tilapia growth performance, it was observed no statistical difference between tilapia fed on pelletized duckweed and commercial
feed, as shown in Table 1.
Results
According to our results, we can conclude that fish
produced in the reuse system fed on pelletized duckweed
reached an average productivity of 22.5 t/ha/cycle, allowing the production of two tilapia production cycles per
year, similar to traditional systems.
Conclusion
Thank you!...
Rodrigo Roubach, PhDProject manager - MPA0 xx 61 [email protected]
Esplanada dos Ministérios, Bloco “D”CEP: 70.043-900 - Brasília/DF
Telefones: (61) 3218-2872 / 2876Fax: (61) 3224-5049
www.presidencia.gov.br/seap
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