UNIVERSIDADE FEDERAL DE SANTA CATARINACENTRO TECNOLGICO
PROGRAMA DE PS-GRADUAO EM ENGENHARIA AMBIENTAL
REUSE OF DOMESTIC EFFLUENT THROUGH PELETIZED DUCKWEEDS WITH RED TILAPIA
Flvia Tavares, Dra. OEI consultant at MPA
Rodrigo Roubach, PhDProject Manager/MPADigenes Lemainski
OEI consultant at MPAFlvio Rubens Lapolli, Dr.
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
Considering pollutants removal
And its use as a feed source in tilapia production
Wastewater Treatment Plant Florianpolis
Facultative pond I
Facultative pond II
Facultative pond III
The effluent used in the Reuse System was pumped from the last Facultative Pond (Facultative pond III).
Duckweed-fish reuse pilot system
The Reuse System was composed by the duckweeds treatment and fish production tanks during a 83
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.
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.
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.
Rodrigo Roubach, PhDProject manager - MPA0 xx 61 firstname.lastname@example.org
Esplanada dos Ministrios, Bloco DCEP: 70.043-900 - Braslia/DF
Telefones: (61) 3218-2872 / 2876Fax: (61) 3224-5049
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