Download - Presentation1 biofloc
-
8/17/2019 Presentation1 biofloc
1/9
Biofoc ProductionSystems orAquaculture
-
8/17/2019 Presentation1 biofloc
2/9
Composition and nutritional value of bioflocs
Bioflocs are aggregates (flocs) of algae, bacteria,
protozoans, and other kinds of particulate organic
matter such as feces and uneaten feed.The biofloc community also includes animals that are
grazers of flocs, such as some zooplankton and
nematodes. Large bioflocs can be seen with the naked
eye, but most are microscopic. Flocs in a typicalgreenwater biofloc system are rather large, around !
to "!! microns, and will settle easily in calm water .
-
8/17/2019 Presentation1 biofloc
3/9
The nutritional #uality of biofloc to cultured animalsis good but rather $ariable. The dry%weight protein
content of biofloc ranges from " to ! percent, with
most estimates between &! and ' percent. Fat content
ranges from !. to percent, with most estimates between and percent.
ried bioflocs ha$e been proposed as an ingredient to
replace fishmeal or soybean meal in a#uafeeds. The
nutritional #uality of dried bioflocs is good, and trials
with shrimp fed diets containing up to &! percent dried
bioflocs show promise
-
8/17/2019 Presentation1 biofloc
4/9
Suitable culture species* basic factor in designing a biofloc system is the species to
be cultured. Biofloc systems work best with species that are able
to deri$e some nutritional benefit from the direct consumption of
floc. Biofloc systems are also most suitable for species that can
tolerate high solids concentration in water and are generally
tolerant of poor water #uality. +pecies such as shrimp and tilapiaha$e physiological adaptations that allow them to consume
biofloc and digest microbial protein, thereby taking ad$antage of
biofloc as a food resource. early all biofloc systems are used to
grow shrimp, tilapia, or carps. Channel catfsh and hybridstriped bass are examples o fsh that are not goodcandidates or biooc systems because they do nottolerate water with very high solids concentrationsand do not have adaptations to flter solids rom
water.
-
8/17/2019 Presentation1 biofloc
5/9
systems
Few types of biofloc systems ha$e been used in
commercial a#uaculture or e$aluated in research. Biofloc
systems e-posed to natural light include outdoor, a
comple- mi-ture of algal and bacterial processes control
water #uality in such greenwater/ biofloc systems. 0ost
biofloc systems in commercial use are greenwater.
These systems are operated as brown% water/ biofloc
systems, where only bacterial processes control water
#uality.The specifications and performance of $arious biofloc
production systems are discussed in more detail at the end
of this publication.
-
8/17/2019 Presentation1 biofloc
6/9
Denitrification and sludge treatment
*lkalinity can be reco$ered in denitrification units. itrateaccumulates in most intensi$e biofloc systems because of
ongoing nitrification. 1f unchecked, nitrate concentration
reflects the cumulati$e feed loading to the system. itrate
accumulation can be tempered by dilution through water
e-change, but this defeats the purpose of intensi$e water use
and reduces biosecurity.
enitrification units are used as part of a water conser$ation
and biosecurity strategy where it is also a cost issue to
conser$e salts. This is an acute need in superintensi$esaltwater systems for shrimp, especially those located inland.
Furthermore, the discharge of saline effluent is restricted or
regulated in many areas, especially inland.
-
8/17/2019 Presentation1 biofloc
7/9
enitrification units are operated under generally
#uiescent and ano-ic conditions. +olids can beshunted to a side%stream tank and allowed to
accumulate. * low flow of culture water, sufficient to
pro$ide a detention time of to " days, is ade#uate to
control nitrate concentration. +olids accumulation will
reach a steady state.
-
8/17/2019 Presentation1 biofloc
8/9
Problems+uspended solids are central to the function of biofloc systems.
The capacity to control solids concentration depends on system
configuration. 2-cessi$e solids concentration is counter%
producti$e because solids can log gills of fish or shrimp.
1t also increases the energy re#uired for mi-ing to keep solids in
suspension and aeration to meet the o-ygen demand of ele$atedwater respiration. 2-cessi$e solids concentration also means that
the response time in the e$ent of system failure is $ery short,
often less than hour. 3ccasionally and unpredictably bioflocs
will de$elop that include large numbers of filamentous bacteria.This so%called filamentous bulking/ effect makes flocs slow to
settle and makes it difficult to control solids concentration.
Filamentous bacteria can also clog shrimp gills and cause
mortality.
-
8/17/2019 Presentation1 biofloc
9/9
*s in most recirculating a#uaculture systems,
nutrients and minerals (especially metals) accumulatein the water of intensi$ely managed biofloc systems.
1n shrimp raceways with low water e-change rates,
nitrate can accumulate to se$eral hundred mg4L, a
le$el that reduces shrimp feed consumption. 1ncludingthe capacity for denitrification in intensi$ely managed
biofloc systems is recommended. 1n marine systems,
maintaining a nitrate concentration of about ! mg4L
is an effecti$e way to minimize the production ofhighly to-ic hydrogen sulfide.