COMPARATIVE STUDY OF AERATION INJECTOR SYSTEM AND MICRO-PERFORATED AIR DIFFUSER HOSES IN SUPER INTENSIVE CULTURE OF Litopenaeus vannamei IN SOUTHERN BRAZIL

Wilson Wasielesky Jr*, Lucas Genésio Silveira, Bob Advent, Geraldo Foes, Alessandro Cardozo, Luis Poersch, Carlos Gaona and Dariano Krummenauer
Institute of Oceanography
Universidade Federal do Rio Grande (FURG)
Rio Grande, RS, Brazil
manow@mikrus.com.br
 

One of the most important requirements for the bioflocs formation is a high oxygenation of the culture tanks, which is primarily provided by aeration devices. The aeration system choice is crucial to obtain high productivity in the system. In BFT systems, aerators are used in the raceways for several reasons: (a) to supply oxygen for animals beyond their limitations, maintaining high stocking densities and productivity; (b) to distribute the oxygen into the culture tanks horizontally and vertically; (c) to mix the water column; and (d) to supply oxygen for microorganism communities. Therefore, it is important to evaluate the performance of different aeration sources on oxygenation, water column turbulence and the formation of microbial aggregates to achieve higher productivity and better performance in BFT systems. Several aeration devices have been used in the BFT systems. The most common in super-intensive raceways are venturis and diffusers (air stones and tubes driven by blowers) where paddlewheel aerators are more common in lined ponds for intensive culture.  Recently a new type of air injector has been used in these raceway systems with great success. These injectors use only a centrifugal pump to re-circulate the water while naturally aspirating ambient air it into the water column at a ratio of 3:1 (air : water). This air injector produces a fine micro-bubble, high transfer rate.

The aim of this study was to evaluate the effects of the different aeration types available in the market on biofloc formation, the microbial community, and water quality as well as to determine the influence of these factors on the growth parameters of Litopenaeus vannamei juveniles raised in a biofloc technology culture system.

A 70 day-trial was conducted at the Marine Station of Aquaculture, University of Rio Grande, Rio Grande do Sul State, Brazil. After nursery, Pacific white shrimp (1.06g ±0.58) juveniles were stocked at 400/m3 in a nine-35 m³ lined raceways greenhouse enclosed. Three treatments (three replicates) were tested: Air injectors (driven by a 2HP centrifugal pump) (Treatment 1), Aerotube® micro-perforated air diffuser (driven by a 2HP blower) (Treatment 2) and a mix of them (Treatment 3). In the injector treatment the a3™injectors were positioned parallel to the direction of flow along the bottom of each tank wall. The Aerotube hoses were cut into 10cm lengths and connected together by PVC pipe and placed one piece every 1.5m2 in the bottom of the tanks. Water temperature, salinity, dissolved oxygen, pH, TA-N, NO2-N, NO3-N, Alkalinity and Settleable solids were daily monitored. The results were analyzed by one-way analysis of variance (ANOVA) and Tukey's test (α = 0.05).

The water quality parameters were influenced by the treatments (P<0.05), but were not limiting for shrimp survival and growth in all treatments. Shrimp survivals were not influenced (P>0.05) by the treatments. The growth parameters were also different among treatments (P<0.05), except FCR (P>0.05). Results suggest that air injectors (A3®) can be incorporated as an important tool in super intensive BFT system in raceways.