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1.
Biofloc technology system (BFT), recirculation aquaculture system (RAS) and polyculture promote efficient use of water, area and nutrient recycling, which are essential practices for sustainable aquaculture development. The aim of this study was to evaluate the growth, feed efficiency, biofloc composition and water quality of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in monoculture and polyculture with giant freshwater prawn Macrobrachium rosenbergii (De Man, 1906) in BFT and RAS, over a period of 30 days. Fish (n = 128; 7.29 ± 0.67 g) were distributed randomly in 16 experimental tanks (8 fish/tank). Prawn (n = 96; 0.50 ± 0.09 g) were allocated in 8 experimental tanks (12 prawn/tank) in a polyculture. The experimental design was completely randomized with four treatments with four replicates each, in a factorial design 2 × 2 (BFT and RAS vs. monoculture and polyculture). The experimental diet (28% of digestible protein; 3100 kcal kg−1 of digestible energy) was used both to fish and prawn in BFT and RAS. There was significant effect (p < 0.01) of the system and the culture for weight gain, apparent feed conversion and protein efficiency ratio. The average weight gain and apparent feed conversion of tilapia in monoculture (30.04 g and 1.39) and in polyculture (36.44 g and 1.27) were superior (p < 0.01) in BFT than in monoculture (23.64 g and 1.74) and in polyculture (24.14 g and 1.61) in RAS. Weight gain and survival of giant freshwater prawn was superior (p < 0.01) in BFT (0.43 g and 87%) compared to RAS (0.26 g and 79%). The data showed that BFT provides better growth performance responses in monoculture for Nile tilapia and in polyculture with giant freshwater prawn compared to RAS.  相似文献   

2.
African catfish (Clarias gariepinus) and lemon fin barb hybrid (LFBH) (Hypsibarbus wetmorei ♂ × Barbodes gonionotus ♀) were cultured in either a biofloc technology (BFT) system or an individual recirculating aquaculture system (RAS) and their survival, growth, feeding efficiencies and biochemical composition were then compared after 8 weeks. LFBH and African catfish were chosen based on their different feeding habits. In the BFT treatments, glycerol was added to create a carbon to nitrogen ratio of 15, while the RAS system consisted of a fine mesh mechanical and biological filter. Each of the four treatments was triplicated, with each replicate consisting of 20 African catfish (0.98 ± 0.05 g) or LFBH (1.77 ± 0.02 g). Water quality and biofloc formation were examined weekly while the biofloc proximate composition was measured in weeks 5 and 8. During weeks 6, 7 and 8 the total viable bacterial colony forming units (CFU) were quantified. Regardless of species, biofloc formation was similar but the crude protein, lipid and ash significantly decreased from week 5 to week 8. However, biofloc crude protein and ash were significantly higher in the LFBH treatment. Total viable CFU were significantly higher (P < 0.05) in BFT compared to RAS, with LFBH having significantly more (P < 0.05) than African catfish. The proximate composition of the fish were unaffected by either system. Implementing BFT significantly (P < 0.05) improved both African catfish and LFBH growth, but this improvement was substantially higher for LFBH (41.6%) than for African catfish (7.6%). This may be due to a better ability of LFBH to consume smaller particles. Preliminary results also indicate that the nutritional composition of bioflocs could be influenced by biofloc age, which could have implications to solids management.  相似文献   

3.
为比较越冬期循环水系统(RAS)与生物絮团系统(BFT)两种模式下大规格罗非鱼(Oreochromis niloticus)鱼种的生长性能与养殖水质的差异。选择RAS组与BFT组,进行为期67 d的养殖,测定养殖过程中罗非鱼种的生长情况以及水质的变化情况。结果显示,RAS组与BFT组增重率和特定增长率分别为(870.69±33.25)%、(3.39±0.05)%/d和(659.47±62.84)%、(3.02±0.13)%/d,RAS组显著高于BFT组;在水质控制方面,RAS组氨氮和亚硝酸盐从养殖初期到实验结束均维持在较低水平,而BFT组在初期氨氮和亚硝酸盐有升高的趋势,峰值分别达到了(4.53±0.72)mg/L和(6.68±1.8)mg/L,分别在第3天和第6天下降到较低水平,硝酸盐两组均呈现不断积累的趋势。结果表明,RAS系统养殖罗非鱼生长速度要高于BFT系统,RAS系统在水质控制方面略优于BFT系统。  相似文献   

4.
Data on operation and performance of cost-effective solutions for end-of-pipe removal of nitrate from land-based saltwater recirculating aquaculture systems (RAS) are scarce but increasingly requested by the aquaculture industry. This study investigated the performance of a (semi)commercial-scale fixed-bed denitrification unit using single sludge for treating effluent from a commercial, saltwater RAS used for production of Atlantic salmon (Salmo salar). A fixed-bed denitrification reactor was fed continuously with 3-days hydrolyzed sludge from the commercial RAS, and was operated at different hydraulic retention times (HRTs; 1.82, 3.64, 5.46, or 7.28 h) or influent C/N ratios (3, 5, 7, or 10). Twenty-four h pooled samples were collected from the inflowing RAS water and the hydrolyzed sludge as well as from the denitrification reactor outlet, and samples were analyzed for nutrients and organic matter content.Nitrate removal rates increased consistently with decreasing HRT (from 64.3 ± 5.2–162.7 ± 22.0 g NO3-N/m3/d within the HRTs tested) at non-limiting C/N ratios, while nitrate removal efficiencies decreased (from 99.6 ± 0.3–58.2 ± 8.9 %). With increasing influent C/N ratios at constant HRT (3.64 h), nitrate removal rates increased until the removal efficiency was close to 100 % and nitrate concentration in the denitrification reactor became rate-limiting. A maximum nitrate removal rate of 162.7 ± 2.0 g NO3-N/m3/d was achieved at a HRT of 1.82 h and an influent C/N of 6.6 ± 0.5, while the most efficient use of hydrolyzed sludge (0.19 ± 0.02 g NO3-N removed/g sCOD supplied) was obtained with a HRT of 3.64 h and a C/N ratio of 2.9. Removal rates of organic matter significantly and consistently increased with decreasing HRT and increasing C/N ratio. In addition, reducing HRT and increasing C/N ratios significantly improved removal of total phosphorus (TP) and PO4-P.In conclusion, optimal management of the operating parameters (HRT and C/N ratio) in a single-sludge denitrification process can significantly reduce the discharge of nitrogen, organic matter, and phosphorous from land-based saltwater RAS and thus contribute to increased sustainability.  相似文献   

5.
为研究絮团浓度对革胡子鲇零换水养殖效果的影响,在不额外添加有机碳源（只利用饲料中的碳）的革胡子鲇（）养殖系统中,设置了平均絮团质量浓度为561.18 mg/L和780.41 mg/L两个处理组,比较了两实验组的水质、菌群结构、鱼生长及氮利用效率。结果表明,两种浓度絮团条件下,总氨氮（total ammonia nitrogen,TAN）和亚硝酸氮（NO2--N）能分别维持1.84 mg/L和1.79 mg/L以下。两处理组间pH、溶解氧（dissolved oxygen,DO）、TAN、NO2--N、氮素利用效率及主要生长指标无显著差异（-N）浓度（822.0 mg/L）明显高于低浓度絮团组（623.33 mg/L）。高通量测序分析菌群结构结果表明,两组间门水平的菌群组成种类及优势度无显著性差异（<0.05）。两处理组中的革胡子鲇存活率分别达到（91.11±1.53）%和（94.44±2.08）%,饲料系数为（1.41±0.18）和（1.27±0.26）,特殊生长率为（2.13±0.04）%/d和（2.19±0.08）%/d,均无显著差异（>0.05）。两实验组饲料氮的利用率分别达到了72.17%和71.34%。综合以上结果认为,仅利用饲料中的碳既能维持革胡子鲇的零换水养殖且能取得较高的氮素利用效率,两种絮团浓度对革胡子鲇的生长无显著影响,高浓度絮团组中的硝化作用更明显。  相似文献   

6.
Intensive recirculating aquaculture relies on biofilters to sustain satisfactory water quality in the system. Fluidized bed and immobilized cell technologies were used to remove ammonia from the water and maintain fish health. A high‐rate nitrifying fluidized bed biofilter combined with valveless filter was designed for use in a recirculation aquaculture system (RAS). The suspended solids produced during fish culture could automatically be removed using a valveless filter. Natural porosity with fitting proportion, steady fluidization and expanding rate was chosen as the fluidized carrier. The technology of bacterial separation and cultivation was used. The immobilized Rhodopseudomonas palustris (R. palustris) produced through a biotechnologically embedding medium is suitable for fish and could help prevent diseases. Nitrification was promoted through the selective rearing of nitrobacteria in a fluidized bed biofilter. Water quality was improved using fluidized bed biofilter and immobilized R. palustris in the RAS. In addition, the proposed system was able to reduce costs. Maximum fish load was 45 ± 3 kg m?3 in the closed recirculating water fish culture system, and water use was reduced by 80–90%. The total ammonia nitrogen removal rate of the technology was 80–95%, and nitrite N removal rate was above 80%.  相似文献   

7.
The objective of this study was to evaluate different hatchery systems used for the larviculture of the Macrobrachium carcinus based on survival, larval development and production of post-larvae. The experimental culture was carried out in three phases designated as Phase I (Zoea VI to VIII – ZVI – VIII), Phase II (Zoea VIII to X – ZVIII – X), and Phase III (Zoea X to PL – ZX – PL), with densities of 30, 27.5 and 25 larvae / L, respectively. The M. carcinus larvae (ZVI) were reared in four culture systems, two being open (Greenwater – GW and Clearwater – CW) and two being closed (Biofloc – BFT and Bio-filter – RAS), distributed in twelve 10 L plastic containers, filled with 20 ppt brackish water, equipped with constant aeration, and water circulated by air lift and heated with thermostat (∼30 °C). The GW treatment was maintained with Chlorophyceae algae in the density of 3–5 × 105 cells/mL. In the CW, the water was previously filtered through a 5 μm mesh screen, sterilized with 10 ppm active chlorine and, dechlorinated with vitamin C and subjected to aeration for 24 h. The BFT received water rich in bioflocs that was matured prior to the experiment and used molasses as a source of organic carbon. In the RAS, the culture water circulated through an external “Dry-Wet” biological filter. The feeding was carried out ad libitum four times daily, alternating a wet diet formula with a commercial diet, which was supplemented with newly hatched Artemia nauplii at a rate of 40–50 per larvae/day. Temperature, dissolved oxygen and pH were monitored daily and the salinity two times per week. Total ammonia, nitrite, nitrate, orthophosphate, alkalinity, total suspended solids, chlorophyll-a, COD and BOD were also analyzed. The best water quality (P < 0.05) was obtained in the RAS, with 0.49 (±0.38), 0.23 (±0.22), and 9.0 (±1.5) mg/L of TAN, NO2-N and NO3-N, respectively. In the GW, the nitrogen species showed high fluctuations and higher concentrations at 2.32 (±1.68), 3.53 (±3.53) and 18.2 (±12.9) mg / L of TAN, NO2-N and NO3-N, respectively. Considering the three phases (ZVI – PL), the overall survival was 0.03, 1.97, 2.23 and 17.32 % for the BFT, CW, GW and RAS, respectively. When considering the phases separately, the survival in Phase I (ZVI – VIII) was highest in the GW system at 58.7 % while the RAS was the highest in Phases II (ZVIII – X) and III (ZX – PL) at 70.6 % and 60.3 %, respectively. The BFT showed 8.4 (±3.5) PL/L, which was higher (P < 0.05) than that obtained in the RAS (2.8 ± 1.2 PL/L) and the GW (1.3 ± 1.1 PL/L) and similar to that obtained in the CW (5.6 ± 2.0 PL/L). Thus, the larviculture for the M. carcinus may be optimized by adopting a multiphase management strategy, which the intermediate larval stages (ZVI – IX) are reared in the GW system and the final stages (ZX – PL) are reared in the BFT system.  相似文献   

8.
Tropical and subtropical climatic conditions in India present an ideal and unique opportunity for being the leader in tropical marine finfish aquaculture. However, the problem persist due to non-availability of marine finfish seed for the culture. In response to this problem, broodstock development of different tropical marine finfishes for seed production was started. The present study was undertaken to design a recirculating aquaculture system (RAS) and studying their performance in managing the various water quality required for the marine finfish broodstock development and breeding. The design of RAS, developed in the present study, included a broodstock tank, egg collection chamber, electrical pump, rapid sand filter, venturi type protein skimmer and biological filter. Two RAS were designed, one was stocked with a demersal fish species, orange spotted grouper (Epinephelus coioides) and the other was stocked with a pelagic fish species, Indian pompano (Trachinotus mookalee) at the rate 1 and 0.5 kg/m3 with a sex ratio of 1:1 and 1:2 (female: male) respectively. Various physio-chemical parameters, viz, total ammonia nitrogen (TAN), nitrite, nitrate, pH, alkalinity, temperature, free carbon dioxide (CO2) and dissolved oxygen (DO) of both tank water were analyzed to assess the performance of recirculating aquaculture system in maintaining the water quality. Gonadal development of the fishes was assessed and the spawning performance was recorded and finally, economic performance of the system was also evaluated. During the entire experimental period, mean monthly total ammonia nitrogen was less than 0.07 and 0.06 mg L−1 and mean monthly nitrite was less than 0.02 and 0.01 mg L−1 in orange spotted grouper and Indian pompano RAS tanks respectively. The pH (7.8–8.2), DO (>4 mg/L) and alkalinity (100–120 mg/L) were found to be in optimum range in both recirculating aquaculture systems. Carbon dioxide was found to be nil during the entire experimental period in both the systems. In fact these levels were comparable or less than that is reported as the permissible limits for broodstock development. Indian pompano and Orange spotted grouper matured and spawning was obtained with production of fertilized eggs round the year. Economic evaluation showed the price of 10,000 fertilized eggs of orange spotted grouper to be US $ 1.33. The design of RAS devised in the present study is efficient in controlling and maintaining optimum water quality for broodstock development of both demersal and pelagic finfishes. The fishes stocked in RAS attained final maturation and round the year spawning was obtained.  相似文献   

9.

Careful nitrogen (N) management will be needed to nourish the growing human population while minimizing adverse environmental impacts. Aquaponic systems (AS) have a great potential to become a sustainable technology making further use of N-rich aquaculture wastewater. In the present study, we observed the N retention and losses in a running prototype of decoupled AS with Nile tilapia (Oreochromis niloticus) and tomatoes (Solanum lycopersicum) over 24 days. N losses amounted to 32.5% of feed N input and were observed in the recirculating aquaculture system (RAS) of the AS. Fish retained 21.1% of N input while 25.2% of N input accumulated in the RAS water. About 14.1% of the loss of N was caused probably by anaerobic denitrification processes in the lamellar settler (LS). In addition, 18.4% of N input was discharged during the three cleanings of LS. In the hydroponic unit of the AS that has been due to space limitations much smaller than an optimized AS could be (only about 20% of the optimal size relative to fish biomass), the tomato plants, including fruits, leaves, and stems, recovered 3.1% of N input with water uptake of 1700 L. The fish culture management, system design, and environmental management in the greenhouse affect the N recovery in the decoupled AS.

  相似文献   

10.

Diseases are one of the most critical limiting factors in aquaculture. Recirculating aquaculture systems (RAS) are one of the most functionally viable sustainable aquaculture production systems adopted world over. In the event of any eventuality caused by bacterial pathogens, antibiotics or other antibacterial agents cannot be applied due to the vulnerability of biological filters which form an integral part of the RAS. Because of this, newer drugs are required for the effective control of diseases in RAS which would not interfere with the activity of nitrifying bacteria used in the biological filters. The antagonistic activity of pyocyanin, a bioactive compound produced by Pseudomonas aeruginosa, against vibrios is well established. The purpose of this study was to prove the effectiveness of pyocyanin as an aquaculture drug for application in RAS by employing a pilot-scale shrimp culture under RAS. It was noted that at the concentration of 5 mg L?1, pyocyanin could significantly bring down the population of Vibrio spp. in RAS without affecting noticeably the other natural heterotrophic bacteria. Also, pyocyanin at this concentration did not inhibit the activity of nitrifying bacterial consortia used in the SBSBR (stringed bed suspended bioreactor) of RAS. The reared shrimp (Penaeus monodon) showed 100% survival after the application of pyocyanin, besides exhibiting normal health signs. Pyocyanin was non-toxic to the shrimp hybrid cell line (PmLyO-Sf9) at the concentration required for its application in disease management (IC50?=?419.26 mg L?1). The present study has demonstrated that pyocyanin is effective as an environment-friendly and safe aquaculture drug for the application in RAS-based shrimp culture to control Vibrio spp. without impeding nitrification established through the deployment of nitrifying bioreactors.

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11.
This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O2 (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.  相似文献   

12.
From an environmental point of view, hydrogen peroxide (HP) has beneficial attributes compared with other disinfectants in terms of its ready degradation and neutral by‐products. The rapid degradation of HP can, however, cause difficulties with regard to safe and efficient water treatment when applied in different systems. In this study, we investigated the degradation kinetics of HP in biofilters from water recirculating aquaculture systems (RAS). The potential effect of HP on the nitrification process in the biofilters was also examined. Biofilter elements from two different pilot‐scale RAS were exposed to various HP treatments in batch experiments, and the HP concentration was found to follow an exponential decay. The biofilter ammonia and nitrite oxidation processes showed quick recuperation after exposure to a single dose of HP up to 30 mg L?1. An average HP concentration of 10–13 mg L?1 maintained over 3 h had a moderate inhibitory effect on the biofilter elements from one of the RAS with relatively high organic loading, while the nitrification was severely inhibited in the pilot‐scale biofilters from the other RAS with a relatively low organic loading. A pilot‐scale RAS, equipped with two biofilter units, both a moving‐bed (Biomedia) and a fixed‐bed (BIO‐BLOK®) biofilter, was subjected to an average HP concentration of ～12 mg L?1 for 3 h. The ammonium‐ and nitrite‐degrading efficiencies of both the Biomedia and the BIO‐BLOK® filters were drastically reduced. The filters had not reverted to pre‐HP exposure efficiency after 24 h, suggesting a possible long‐term impact on the biofilters.  相似文献   

13.
This 210-day study compared variation in water quality and fish growth for channel catfish (Ictalurus punctatus; 47 g/fish) stocked in earthen ponds (1.5 fish/m2, 14,820/ha) and in a biofloc technology (BFT) production system with high-density polyethylene-lined rectangular tanks (12.6 fish/m2, 126,000/ha). Feed input and culture environment affected water-quality dynamics. In ponds, phytoplankton uptake predominated and little nitrification occurred, whereas in the BFT system phytoplankton uptake and nitrification maintained low ammonia-nitrogen concentrations. Size classes of fish were skewed toward the larger market sizes in ponds and toward smaller market sizes in the BFT system. Mean final fish weight was 630 g/fish in ponds and 542 g/fish in the BFT system. Despite these differences, fish yield was higher in the BFT system (7.7 kg/m3 v. 1.5 kg/m3) because of the greater initial stocking rate.  相似文献   

14.
A sustainable aquaculture production involves alternatives, as recirculating aquaculture systems (RAS), in order to increase the water supply efficiency. This paper aims: a) to propose a method for dimensioning a RAS filled and additionally supplied with water from a rainwater harvesting systems (RHS) and; b) to evaluate the efficiency of the system based on the supply of rainwater from the RHS, the quality of water in the RAS, and the development of aquatic organisms. A pilot aquaculture farm for rainbow trout (Oncorhynchus mykiss) production was designed and dimensioned. On one hand, the RAS with a configuration based on a treatment tower provided acceptable values of pH, TAN, and alkalinity. The temperature was slightly above the recommended temperature but did not negatively impact trout development. On the other hand, the water use efficiency reached 178 L/kg of fish, instead of 210,000 L/kg in an open flow system for trout rearing. The RHS fulfilled the additional required water on the test period of the pilot farm and is expected to supply at least 92% on average during the useful life. Regarding the aquatic organisms’ development, the system allowed both a better Length/ weight ratio and a lesser mortality rate compared to previous studies of RAS. In contrast to other studies in the literature, the mathematical models for dimensioning the system were calculated as a function of the final biomass expected in the tank instead of the quantity of supplied feed. Therefore, this method confirmed the applicability of this alternative criterion for designing biofilters and aquaculture systems.  相似文献   

15.
Recirculating aquaculture systems (RAS) discharge management limits the development of the aquaculture sector, because RAS do not automatically result in low nutrient emissions. Research has helped develop discharge management systems such as wetlands and woodchip bioreactors that have been adopted by Danish commercial model trout farms. To further develop the Danish concept, we have modelled and built a novel “zero-discharge” recirculating aquaculture system with an annual capacity of approximately 14 tonnes. The aim of this paper is to describe the entire concept and present the results from the start-up phase of the whole system. The concept includes the treatment of RAS effluent (overflow and sludge supernatant) using a hybrid solution of a woodchip bioreactor, constructed vertical wetland, and sand infiltration. Using this three-step process, the nitrate, phosphorus, and organic matter effluent are decreased to acceptable levels to reuse the water in the RAS process reducing the need for new raw water. In the first nine months of operation, a water treatment field was used as an end-of-pipe treatment to ensure the water was safe to recirculate for fish. During the winter, the water temperature dropped to 2.7 degrees in the sand filter, but the frost did not reach the water levels in any of the treatment processes. It therefore appears that a hybrid solution can operate sufficiently even in winter conditions. In the first year of operation, a woodchip bioreactor can remove 97 % of the nitrate, although the slow start-up of the RAS caused the bioreactor to be N-limited. On average, 79 % and 92 % of the inflow phosphate concentration was removed in the woodchip bioreactor and the entire hybrid treatment field respectively. The wetland and sand filter removed organic matter sufficiently (35 %), but because of the longer than designed actual water residence, it leached from the bioreactor more than was expected. Further experimentation is needed to identify the financial applicability and performance during higher feeding rates.  相似文献   

16.
Controlling the concentration of bioflocs is one of the main concerns in aquaculture systems with Biofloc Technology (BFT). Biofloc accumulation deteriorates the water quality and can negatively affect the production rates of the farmed river shrimp. This study describes and characterizes the settling velocity distribution of bioflocs generated with the addition of two carbon sources (molasses and chancaca) when applying the BFT for the rearing of the river shrimp Cryphiops caementarius. This study revealed that bioflocs generated with different carbon sources have different settling velocity curves. Regarding the mass fraction settling velocities, there were significant differences (P < 0.05) for mean solids fraction at similar withdrawn times between molasses and chancaca. The average settling velocities for bioflocs were 0.1044 ± 0.1224 cm s−1 for molasses and 0.1131 ± 0.1225 cm s−1 for chancaca. Therefore, a settling device operating with a given overflow rate will more efficiently remove bioflocs generated with chancaca than with molasses. The settling velocity curves obtained in this research contain valuable information to select appropriate devices for bioflocs and suspended solids removal in aquaculture systems with BFT.  相似文献   

17.
The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhynchus mykiss). Three set-ups with triplicate tanks were used: 1. two consecutive fixed bed bioreactors (FF); 2. a fixed bed bioreactor followed by a moving bed bioreactor (FM) and 3. two consecutive moving bed bioreactors (MM). Fish performance was not influenced by the design of the bioreactor, specific growth rate (SGR) being between 1.59 and 1.64% d−1 and feed conversion ratio (FCR) between 0.95 and 0.98. Water nitrite concentration was higher in the FF systems compared to FM and MM systems, whereas the average total ammonia nitrogen concentration (TAN) was not influenced by the treatments. Nitrification rate, which was measured in the laboratory, followed the water nitrite levels, indicating highest total ammonium oxidation rates in the MM systems. UV254 absorbance and total organic carbon (TOC) concentrations were higher in the groups with moving bed systems, indicating accumulation of organic substances in the circulating water. The total volume of particles was higher in the MM systems as compared to the FF systems. The total solids balance was similar in all the bioreactor groups, since the removal of solids by the FBBR backwash was compensated by the drum filter in the FM and MM systems. In general, no significant histopathological difference in gill, kidney, heart and liver tissue were observed between the RAS treatment groups and the flow-through treatment.  相似文献   

18.
This research reveals the applied engineering basis for determining the particle size and settling velocity distributions of solids generated while rearing wild-caught premature punctuated snake-eels (Ophichthus remiger) in a prototype recirculating aquacultural system. Settled solids were sampled from the bottom of the rearing tanks, and suspended solids were sampled before filtration within the drum filter and analyzed to characterize their settling velocity and particle size properties. These particle properties are considered bioengineering parameters since they will provide biological information to improve engineering solutions for RAS solids removal processes. The average settling velocity for the settleable solids in the rearing tanks was 2.89 ± 0.02 cm s−1, and the average particle size ranged between 7.32 ± 3.41 and 19.44 ± 8.58 mm. Suspended solids within the drum filters before filtration had an average settling velocity of 0.35 ± 0.11 cm s−1 and it was found that 69.93 % of the particles size was greater than 200 μm, 15.40 % were within the range of 120 μm and 90 μm sizes, and 6.53 % were between 70 μm and 40 μm sizes. The particle physical properties, settling curves, and particle sizes curves obtained from this experience represent valuable information to be used to improve engineering design of solids handling mechanisms, especially in marine land-based systems, and in this case, applied for rearing wild-caught punctuated snake-eels. The present investigation constitutes an advance in the knowledge of applied engineering to the design of a marine aquaculture fattening operation targeted to feed up wild-caught premature punctuated snake-eels to the point of sale or trade.  相似文献   

19.
为了评估全封闭循环水养殖系统中养殖密度对钝吻黄盖鲽生长的影响及水质变化情况,将体质量为(250.00±50.83)g的钝吻黄盖鲽分成8个试验组(放养密度分别为18、22、26、30、34、38、42、46 kg/m3),进行了3个月的饲养试验,检测不同养殖密度下鱼的成活率、体质量增长率及饲料系数,同时对试验期间氨氮、亚硝酸盐和溶解氧等各项水质指标的动态变化进行监测。试验结果显示,各试验组鱼的成活率均达到96%以上,但随着养殖密度的增加,钝吻黄盖鲽的成活率总体呈现降低的趋势;低密度组(18 kg/m3)的体质量增长率最高,为36.1%,高密度组(46 kg/m3)的体质量增长率最低,为24.8%,且体质量增长率随着养殖密度的增加而逐渐降低;随着养殖密度的增加,饲料系数呈逐渐升高的趋势;养殖期间各项水质指标均保持在适宜钝吻黄盖鲽生长的范围内。结果表明,在本试验的循环水养殖系统中,综合考量养殖生长指标及单位面积产量,钝吻黄盖鲽规模化生产的最适养殖密度为42～46 kg/m3。  相似文献   

20.
Competition between heterotrophic and nitrifying bacteria is of major practical importance in aquaculture biofilter design and operation. This competition must be understood to minimize the negative impact of heterotrophic bacteria on an aquaculture system. On the other hand, the heterotrophic population is suspected of having a positive effect against pathogenic bacteria. Little information is available on the bacterial communities present within aquaculture systems, except for nitrifying bacteria, but a combination of traditional aquacultural engineering research methods and novel microbiological techniques offers new opportunities for the study of these communities.

The heterotrophic bacterial population activity and the nitrification efficiency of a submerged biological filter were studied for an influent TAN concentration of 2 mg/l and varying C/N ratios. The TAN removal rate was found to be 30% lower at a C/N ratio of 0.5 than at a C/N ratio of 0. For higher C/N ratios the reduction in nitrification efficiency was 50% while the attached bacterial abundance was doubled. Moreover, results confirm that abundance of sheared and attached bacteria are correlated. It is not known to what extent biofilter configuration might influence the relationship between heterotrophic and nitrifying bacteria, and further work will be carried out with moving bed and fluidized filters. A better understanding of the role of the heterotrophic bacteria in RAS will help to optimize any positive “biocontrol” effect and to minimize the microbial degradation of rearing water and the reduction of nitrification rates.  相似文献   


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