Effects of Bioflocs on Artemia Growth and Water Quality

1 Introduction Bioflocs is a heterogeneous mixture of the microorganisms,particles,organic polymers and dead cells,etc.(Hargreaves,2006).Among which,heterotrophic bacteria convert efficiently the ammonia nitrogen into the bacterial protein,which provides the supplementary feed for culture animals and reduces the nitrogen level in the culture system(De Schryver et al,2008).In the closed aquaculture system,the growth of

Performance of feeding Artemia with bioflocs derived from two types of fish solid waste

The production of bioflocs with the solid waste from recirculating aquaculture systems(RAS)and feeding Artemia results in additional nutrient retention and lowers waste discharged from RAS.The solid waste from the drumfilters of two RAS,which stocked European eel(Anguilla anguilla)and Nile tilapia(Oreochromis niloticus),was used as substrate to produce bioflocs in suspended growth reactors,referred to as E-flocs and T-flocs,respectively.Mono-diets consisting of 100%E-flocs and 100%T-flocs were added to culture Artemia,referred as E-Artemia and T-Artemia,respectively,in a laboratory scale test.The efficiency of this feeding regime was investigated.A significant difference was observed in terms of crude protein content(35.59±0.2%)for E-flocs,(29.29±0.95)%for T-flocs,(70.01±0.92)%for E-Artemia and(65.63±0.89)%for T-Artemia.134 out of the total operational taxonomic units(OTUs)were present in E-flocs and T-flocs from the analysis of high-throughput sequencing data.Most of the shared OTUs belonged to cyanobacteria.C18:1n7 of T-flocs was higher than that of E-flocs(P<0.05).C18:2n6 of E-flocs was significantly higher than that of T-flocs(P<0.05).No significant difference was observed in the other fatty acid compositions(P>0.05).The survival rate of E-Artemia was(22±0.02)%,significantly higher than that of T-Artemia(16%±0.02%)(P<0.05).No significant difference was observed between the average body weight of E-Artemia(2.38±0.40 mg)and E-Artemia(2.91±0.21)(P>0.05).The EPA of Artemia fed with E-flocs was(3.00±0.46)%,significantly higher than that of T-Artemia(1.57±0.19%)(P<0.05).This study offers a method for reusing the aquaculture waste,which will be helpful to achieve a zero-pollution discharge for aquaculture systems.

Chicken Eggshell as an Innovative Bioflocculant in Harvesting Biofloc for Aquaculture Wastewater Treatment

Implementation of biofloc technology(BFT)system in aquaculture industry shows high productivity,low feed conversion ratio,and an optimum culture environment.This study was divided into two phases.The first phase involved maintaining the water quality using the optimum carbon-to-nitrogen ratio by manipulating pH in culture water.The second phase examined the performance of harvesting biofloc(remaining phytoplankton and suspended solids in the system)using chicken eggshell powder(CESP).This study showed that pH 7 to 8 were the best biofloc performance with high removal percentage of ammonia(>99%)with a remaining ammonia concentration of 0.016 mg L^(−1)and 0.018 mg L^(−1),respectively.The second phase of this study was performed to determine the optimal formulation and conditions of using CESP as a bio-flocculant in harvesting excess biofloc.The use of eggshell showed a higher harvesting efficiency of more than 80%under the following treatment conditions:0.25 g L^(−1)of eggshell dosage;with rapid and slow mixing rates of 150 and 30 rpm,respectively;30 min of settling time;settling velocity of 0.39 mm s^(−1)and pH of 6 to 7.Therefore,the results indicated that biofloc would be the best green technology approach for sustainable aquaculture wastewater and the CESP is an organic matrix that environmental-friendly bio-coagulant for biofloc harvesting.

Application of biofl oc technology in recirculation A rtemia culture system

Biofl oc technology(BFT)improves water quality,and productivity of the farmed species through converting ammonium nitrogen to microbial protein,stabilizing microbial community,and reducing the production cost.In this study,a small-scale biofl oc development unit was designed in combination of recirculation system(RAS)for Artemia culture.Artemia growth,water quality,and microbial composition of biofl ocs in RAS were studied in comparison with in-situ batch culture(Glu).Glucose was added in RAS and Glu at C/N ratio of 10.The cultures without glucose addition,but with 50%daily water renewal(WRe)and without water renewal(NWRe)were considered as the controls.Arte mia were cultured at 25℃ and salinity 30 for 24 days and fed formulated feed.The results showed that compared to the controls,Glu signifi cantly improved the Artemia biomass,increased the biofl oc volume,and reduced the content of total ammonia nitrogen(TAN),nitrite nitrogen(NO_(2)-N)and nitrate nitrogen(NO_(3)-N)in water column(P<0.05).In addition,RAS had similar results with Glu.High throughput sequencing analysis on biofl oc microbial composition demonstrated that glucose supplement shaped the microbial community structure,and increased proportion of potential probiotic bacteria and suppressed pathogenic bacteria growth.Furthermore,we analyzed the relationship between the microbial composition of biofl oc and environmental factors.Canonical correspondence analysis(CCA)indicated that inorganic nitrogen in culture water had great impact on biofl oc microbial composition in NWRe and WRe,whilst the dissolved organic carbon(DOC)modifi ed the microbial community in Glu and RAS.This study shows the advantages of BFT in Artemia culture and provides practical information for applying BFT-RAS in indoor Artemia culture.

Sexual Reversal with 17α-Methyltestosterone in Oreochromis sp.:Comparison between Recirculation Aquaculture System(RAS)and Biofloc Technology(BFT)

Precocity in tilapia implies the use of several methods of obtaining monosex seed;the most common tends to use masculinizing hormone 17α-methyltestosterone(17αMT),with variable results.Thus the objective of this study was to compare the efficiency of the sexual reversion process using 17αMT,in a recirculation system and in biofloc.In a totally randomized design,three tanks for recirculation(T-RAS)and three tanks for biofloc(T-BIO)with a capacity of 200 L effective volume were taken and filled with 1,056 larvae of Oreochromis sp.,without reversing and with an initial weight of 0.02 g and an initial total length of 1.4 mm.The study was carried out during 65 d,the fish were fed(10%biomass,adjusted every 15 d)by a commercial diet at 45%of crude protein that included 17αMT(60 mg/kg).Water quality,microbiology,zootechnical and gonadal analysis were monitored.Consequently the water quality results showed that just dissolved oxygen(DO),temperature(T-°C)and alkalinity did not show significant differences.Additionally,in the productive parameters there were significant differences in the final length,the gain in length and in K which were better in T-BIO.The microbiological ones did not present significant differences between the treatments.Lastly,the percentage of reversion was significantly better in T-RAS.Then,this study suggests that settleable solids concentrations above 35 cm decrease the efficiency of the sexual reversion for this species.

Effect of seeding biofloc on the nitrification establishment in moving bed biofilm reactor(MBBR)

In recirculating aquaculture systems,nitrification is usually accelerated by inoculating nitrifier or mature biocarriers.In this study,the performance of the establishment of nitrification in the MBBR according to three different strategies:conventional method(Control group A),inoculation with biofloc recovered from a tilapia biofloc culture system(Group B),and addition with extra nitrite(Group C)in the Moving bed biofilm reactor(MBBR)was compared.Among them,the biofloc-inoculated group considerably accelerated the nitrification process in the MBBR(38 d),which is roughly 18 d faster than the control group(A)(56 d)and 21 d faster than group C(59 d).Less ammonia(8 mg/L NH_(4)^(+)-N,10 mg/L in other groups)and external nitrite(2 mg/L NO_(2)􀀀^(-)N)in the influent caused effluent ammonia to drop more slowly(5 d slower than the control group,8 d slower than the B group),which is detrimental to the nitrification process’development.Notably,the influent’s hydraulic retention time(HRT)was reduced from 12 h to 6 h following the successful establishment of nitrification.During the adaptation to reduced HRT,the MBBR inoculated with biofloc experienced short-term changes in the water quality index of the effluent water,whereas the other groups did not.The biofilm seeded with biofloc had the highest mean gray value ratio(1.42)of live/dead cell fluorescence,which grew better and could cover the entire groove under multiple microscope observations.However,the other groups did not demonstrate a similar trend.In summary,the research found that seeding biofloc use as nitrification bioaugmentation into the MBBR of the recirculating aquaculture system(RAS)to greatly speed up the nitrification process.

Comparing salinities of 0, 10 and 20 in biofloc genetically improved farmed tilapia (Oreochromis niloticus) production systems

A 150 days(150-d)experiment was carried out to investigate the production efficiency,inorganic nitrogen syndrome and bacteria community of indoor biofloc technology(BFT)systems used to rear genetically improved farmed tilapia(Oreochromis niloticus)under 0(S-0),10(S-10),and 20 salinities(S20).The start-up period for BFT was 50,60 and 80 d for S-0,S-10 and S-20 groups,respectively.At steady state,the total ammonium nitrogen(NH4þ-N)and nitrite nitrogen(NO2-N)were lower than 3.0 mg/L and 0.34 mg/L,respectively and no nitrate-nitrogen(NO3-N)accumulation was observed.The fish survival rate was above 95%for all the groups.The final fish biomass of the S-10 group(35.83±1.08 kg/m^(3))was not significantly different from the S-0(34.79±1.33 kg/m^(3))group but was significantly higher than S-20(32.6±1.04 kg/m3).The feed conversion ratio for the tilapia in S-20 was 1.46,which was higher than the ratio in S-0(1.40)and S-10(1.39)tilapia.There was no significant difference in the crude protein content of the back muscle from tilapia of the three experimental groups.No significant difference in blood parameters,except for aspartate aminotransferase and alkaline phosphatase was observed between the three groups.Evaluation of microorganisms in the three BFT systems revealed that Proteobacteria,Bacteroidetes,and Fusobacteria were the top three at the phylum level in all groups.However,a significant difference was observed at the genus level in the bacteria of the three BFTs at different salinity(P<0.05).©2017 Published by Elsevier B.V.on behalf of Shanghai Ocean University.This is an open access article。

Dynamics of nitrogenous compounds and their control in biofloc technology (BFT) systemsA review

Controlling toxic nitrogenous substances in biofloc technology(BFT)systems is critical for the success of this novel technology.To effectively control nitrogen accumulation in BFT systems,it is important to first understand the dynamics and the removal pathways of this element and its related compounds from aquaculture water.This review focuses on synthesizing the information of nitrogen dynamics in BFT systems to provide researchers and practitioners with a guide to the fate of nitrogen and its control methods.This paper discusses the different types of nitrogenous compounds in BFT water,the transformation processes of ammonia to nitrites and nitrates,the relationship between the two forms of ammonia(NH3 and NH4+)in water and the equilibrium between them.This paper also discusses nitrification as a major nitrogen removal pathway and the factors that influence the nitrification process.Notably,the control of nitrogen in BFT systems by manipulating the carbon to nitrogen ratio(C/N)using external carbohydrates is described in this paper.This paper suggests that further studies should focus on investigating the various factors that influence nitrogen dynamics in BFT systems and the means of controlling contaminants other than nitrogen.