Pilot-scale Recirculating Aquaculture Systems Research Articles

Ambient salinity and osmoregulation, energy metabolism and growth in juvenile yellowtail kingfish (Seriola lalandiValenciennes 1833) in a recirculating aquaculture system

The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 ± 0.6 g) were kept for 29 days at 14, 18, 22, 26 (experimental) and 30 g L−1 (control) salinity in independent, pilot-scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L−1 (7.61 ± 0.19, 7.61 ± 0.01 and 7.61 ± 0.13% day−1, respectively) had higher growth rates than fish at 26 and 30 g L−1 (7.10 ± 0.05 and 6.97 ± 0.06% day−1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on-growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.

The effect of temperature and pH on the growth and physiological response of juvenile yellowtail kingfish Seriola lalandi in recirculating aquaculture systems

A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in the Netherlands identified yellowtail kingfish Seriola lalandi as having excellent potential. To assist in determining the most appropriate water quality conditions for this species in RAS, the effect of water temperature (21, 23.5, 25, 26.5 and 29°C) and pH (6.58, 7.16 and 7.85) was tested in two separate experiments. Growth performance, feed conversion, stress-physiological and metabolic parameters were assessed in juvenile yellowtail kingfish grown in pilot-scale RAS. Growth was optimised at a water temperature of 26.5°C, in combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21°C to 26.5°C resulted in a 54% increase in the fish's final weight after 30days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish could not adapt.

Degradation and effect of hydrogen peroxide in small-scale recirculation aquaculture system biofilters

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.

Long term/low dose formalin exposure to small-scale recirculation aquaculture systems

Repetitive long term formalin application at low dose was investigated to determine the effect on formaldehyde removal rate, biofilter nitrification and the microbial composition in small-scale recirculation aquaculture biofilters. Six pilot-scale recirculation aquaculture systems holding rainbow trout ( Oncorhynchus mykiss) were designated to formalin treatments ( C 0 at 10 and 20 mg/L formaldehyde) on a daily or weekly basis. Formaldehyde removal rates were measured over 10 weeks, during which biofilter nitrification rates were measured in terms of standardized NH 4Cl spiking events. The rates were positively correlated to the amount and frequency of formalin treatment. In systems with regularly low formalin dosage, the formaldehyde removal rate increased up to tenfold from 0.19 ± 0.05 to 1.81 ± 0.13 mg/(L h). Biofilter nitrification was not impaired in systems treated with formalin on a daily basis as compared to untreated systems. In systems intermittently treated with formalin, increased variation and minor reductions of ammonium and nitrite oxidation rates were observed. Nitrifying bacteria were screened by specific gene probes using fluorescence in situ hybridization and quantified by digital image analysis. The relative abundance of ammonia-oxidizing bacteria (AOB) was up to 5.4% of all Bacteria (EUB) positive cells, predominantly Nitrosomonas oligotropha. Nitrite-oxidizing bacteria (NOB), mainly consisting of Nitrospira sp. were found in all biofilm samples up to 2.9%, whereas Nitrobacter sp. was not detected. The relative abundances of AOB and NOB in the untreated system were generally higher compared to the system exposed to formalin. Low dose formalin in recirculated aquaculture systems proved to be a possible treatment strategy, as the effect on nitrification was minimal. Since formaldehyde was steadily removed by microorganisms, available biofilter surface area, hydraulic retention time and temperature can be used to predict removal and hence estimate e.g. effluent concentration.

Powdered activated carbon for fouling reduction of a membrane in a pilot-scale recirculating aquaculture system

Recirculating aquaculture systems (RAS) are essential for the reduction in fresh water usage as well as the discharge of nutrients along with aquaculture effluents. A RAS consisting of an anoxic reactor, a membrane bioreactor (MBR) and a UV-disinfection unit was used to process 10,000 L/d of aquaculture effluent providing high-quality treated water for recirculation to a Barramundi fish culture. The system maintained low levels of nitrate (<20 mg/L), nitrite (<3 mg/L) and ammonia (<0.6 mg/L) in the fish tank. Permeate from the membrane that was recirculated to the fish tank contained <21 mg/L of nitrate, <2 mg/L of nitrite and 0 mg/L of ammonia. However, the rate of fouling of the membrane in the MBR was around 1.47 kPa/d, and the membrane in the MBR required cleaning due to fouling after 16 days. Cleaning of the membrane was initiated when the TMP reached around 25 to 30 kPa. In order to reduce the rate of fouling, 500 mg of powdered activated carbon (PAC) per litre of MBR volume was introduced, which de...

Powdered activated carbon for fouling reduction of a membrane in a pilot-scale recirculating aquaculture system

Recirculating aquaculture systems (RAS) are essential for the reduction in fresh water usage as well as the discharge of nutrients along with aquaculture effluents. A RAS consisting of an anoxic reactor, a membrane bioreactor (MBR) and a UV-disinfection unit was used to process 10,000 L/d of aquaculture effluent providing high-quality treated water for recirculation to a Barramundi fish culture. The system maintained low levels of nitrate (<20 mg/L), nitrite (<3 mg/L) and ammonia (<0.6 mg/L) in the fish tank. Permeate from the membrane that was recirculated to the fish tank contained <21 mg/L of nitrate, <2 mg/L of nitrite and 0 mg/L of ammonia. However, the rate of fouling of the membrane in the MBR was around 1.47 kPa/d, and the membrane in the MBR required cleaning due to fouling after 16 days. Cleaning of the membrane was initiated when the TMP reached around 25 to 30 kPa. In order to reduce the rate of fouling, 500 mg of powdered activated carbon (PAC) per litre of MBR volume was introduced, which decreased the rate of fouling to 0.90 kPa/d. Cleaning of membrane was needed only after 31 days of operation while maintaining the treated effluent quality. Thus the frequency of cleaning could be halved due to the introduction of PAC into the MBR.

The growth of disk abalone, Haliotis discus hannai at different culture densities in a pilot-scale recirculating aquaculture system with a baffled culture tank

The growth rate of disk abalone, Haliotis discus hannai, energy consumption and changes in water quality were monitored in a pilot-scale recirculating aquaculture system (RAS) for 155 days. Baffles were installed in the RAS culture tanks to enlarge the attachment area and clean out solid waste materials automatically by hydraulic force only. The experimental disk abalones, of shell length 24.5 ± 0.5 mm, were cultured at three stocking densities, 700, 1300 and 1910 individuals/m 2 bottom area, in triplicate. The abalones were fed with sea mustard, Undaria pinnatifida, once a week. The abalone feed conversion rates and daily growth rates ranged from 24.5 to 25.9 and 0.32 to 0.36%, respectively. Their daily shell increments and survival rates ranged from 67.7 to 78.6 μm/day and 87.6–92.2%, respectively. The growth in weight tended to decrease at a culture density of 1300 individuals/m 2 bottom area, while shell increments and survival rates were acceptable at this density. The total power consumption for heating was 1185.4 kW, comprising 30.2% of the total power consumption, while the average water exchange rate was only 2.9% per day. The total ammonia nitrogen stabilized below 0.07 mg/L, after conditioning of the biofilter. The NO 2 −–N, NO 3 −–N and total suspended solid concentrations were also maintained within acceptable ranges for the normal growth of disk abalone. The use of the RAS with these newly designed culture tanks for disk abalone culture produced 1300 individuals/m 2 bottom area with a water exchange rate of only 2.9% per day and used about one-tenth of the heat energy of a conventional flow-through system.

Temperature-dependent and surface specific formaldehyde degradation in submerged biofilters

This study investigated formaldehyde removal in submerged fixed media biofilters in commercial and pilot scale recirculation aquaculture systems. Steady removal of formaldehyde (F) was observed immediately after simulated therapeutic treatment in closed systems and complete removal occurred within 1–4 days depending on water temperature. Formaldehyde removal was dependent on available biofilter surface area, and comparable rates of surface specific removal (SSR) were observed in two different systems. SSR was positively correlated to temperature (Q10=3.4) with estimates of 2.1mg F/(m2h) at 5.7°C to 6.5±0.2mg F/(m2h) at 14.5°C. The estimates for SSR of formaldehyde can be used to predict actual treatment and effluent concentration with more accuracy. Furthermore, the results allow calculation on biofilter removal capacity of formaldehyde, applicable for developing biofilters ensuring sufficient formaldehyde removal in effluent water.

고정화 미생물을 이용한 공기 부상식 생물반응기에 의한 순환 여과식 양어장의 순환수 처리

Performance of an airlift bioreactor (ABR) containing the immobilized microorganisms was evaluated in an integrated pilot scale recirculating aquaculture system stocked with Nile tilapia (Oreochromis niloticus) at an initial rearing density of <TEX>$5\%$</TEX> and compared to a rotating biological contactor (RBC) for 40 days. The TAN concentration of rearing tank for ABR and RBC were maintained at <TEX>$0.4\;g/m^3$</TEX> and <TEX>$0.5\;g/m^3,$</TEX> respectively, The nitrite nitrogen was completely removed by the ABR. The ABR's aeration was more stable than the RBC's. On the whole, the feasibility of ABR as an aquacultural water treatment unit was recognized.

Floating Bead Filter에 의한 순환여과식 양식장의 부유고형물 제거와 질산화

The floating bead filter was tested for treatment of aquacultural water in a pilot-scale recirculating aquaculture system. Performance of floating bead filter on the removal of total suspended solids (TSS) and the treatment of nitrogen sourer such as total ammonia nitrogen (TAN), nitrite nitrogen and nitrate nitrogen were evaluated. The system was stocked with Nile tilapia at an initial rearing densities of <TEX>$5\%\;and\;7\%$</TEX> over 30 days. The average TSS removal rates were <TEX>$43.0\;g/m^2{\cdot}day\;and\;39.5\;g/m^2{\cdot}day$</TEX> for rearing density of <TEX>$5\%\;and\;7\%$</TEX>, respectively. As rearing density increased from <TEX>$5\%\;to\;7\%$</TEX>. the TAN removal efficiency decreased from <TEX>$22.0\%\;to\;17.7\%$</TEX>. At the rearing densities of <TEX>$5\%\;and\;7\%$</TEX>, the average TAN removal rates and removal efficiencies were <TEX>$38.8\;g/m^2{\cdot}day,\;15.6\%\;and\;37.8\;g/m^2{\cdot}day.\;17.7\%,$</TEX> respectively. The average TAN removal rate was <TEX>$37.8-38.8\;g/m^3{\cdot}day.$</TEX> The oxygen consumption by floating bead filter was higher than theoretical oxygen consumption rate by nitrification.

Pilot-scale 순환여과식 양식장에서 회전원판 반응기의 순환수 처리 및 산소전달

The rotating biological contactor (RBC) was tested for treatment of aquacultural water in a pilot-scale recirculating aquaculture system. Performance of RBC on the treatment of nitrogen source such as total ammonia nitrogen (TAN), nitrite nitrogen and nitrate nitrogen and chemical oxygen demand (CODcr.) was evaluated. A system was stocked with nile tilapia at an initial rearing densities of and over 30 days. As increasing rearing density from to , the TAN removal rates was increased from to . But TAN removal efficiency was decreased from to . The removal rate of was higher than TAN. The RBC as an aerator was also evaluated for increasing dissolved oxygen concentration. For and of rearing density, the average aeration rate were and , respectively.

Pilot-scale 순환여과식 양식장에서 병류 공기구동식 포말분리장치의 성능

본 연구는 사육조 용적 2.5<TEX>$m^3$</TEX> 규모의 pilot-scale 순환석과식 양어장에 나일 틸라피아를 2, 5, <TEX>$7\%$</TEX>의 밀도로 사육하면서 사육조내의 수질과 포말분리기에 의해 배출된 포말농축액의 수질을 분석하여 병류 공기구동식 포말분리기의 실제 어류를 사육하는 양어장에서 나타내는 효율을 측정하고자 하였다 사육밀도가 증가함에 따라 단백질, 총 부유 고형물, 화학적 산소요구량 등 각 수질 인자의 농도가 증가하였으며 포말 농축액의 유출량도 증가하였다. 사육조의 단백질 농도는 사육밀도가 <TEX>$5\%$</TEX>에서 <TEX>$7\%$</TEX>로 높아짐에 따라 16.6 g/<TEX>$m^3$</TEX>에서 21.9 g/<TEX>$m^3$</TEX>으로 증가하였으며 일간 제거량은 0.99 g/day에서 2.5 g/day로 증가하였으나 포말의 단백질 농도는 50.6 g/<TEX>$m^3$</TEX>에서 36.6 g/<TEX>$m^3$</TEX>으로 감소하여 농축비는 3.2에서 1.9로 감소하였다. 사육밀도의 변화에 따른 총 부유 고형물과 화학적 산소 요구량의 일간 제거량, 농축비와 포말 농축액의 농도의 변화는 단백질 제거특성과 그 형태가 유사하였다 총 부유 고형물의 일간 제거량은 사육밀도 <TEX>$2\%$</TEX>일 경우 0.2g/d, <TEX>$5\%$</TEX>에서는 0.8 g/d 7%에서는 1.5 g/d로 사육밀도와 비례하여 증가하였으며 화학적 산소요구량의 일간 제거량은 사육밀도 <TEX>$2\%$</TEX>일 경우 1.6 g/d, <TEX>$5\%$</TEX>에서는 4.2 g/d, <TEX>$7\%$</TEX>에서는 7 g/d로 나타났다. 총 부유 고형물과 화학적 산소 요구량의 농축비와 제거량은 단배질과 비슷한 경향을 보였으며 총 부유 고형물과 화학적 산소 요구량의 농축비의 경우 <TEX>$2\%$</TEX>의 사육 밀도에서 각각 10.2, 8.4의 가장 높은 값을 나타내어 포말분리기가 양어장 순환수 처리에 효율적임을 알 수 있었다. The performances of a parallel current air driven type foam separator were evaluated in the pilot-scale recirculating aquaculture system. The system was stocked with Nile tilapia (Oreochromis niloticus) at an initial rearing densities of <TEX>$2\%$</TEX>, <TEX>$5\%$</TEX> and <TEX>$7\%$</TEX> of water volume of rearing tank and reared for 15, 30, 35 days, respectively. The condensated volume of effluent foam was increasing with increased rearing density. As increasing rearing density from <TEX>$2\%$</TEX> to <TEX>$7\%$</TEX>, the protein concentration in rearing tank was increased from 16.6 g/<TEX>$m^3$</TEX> to 21,9 g/<TEX>$m^3$</TEX> and the removal amount of protein through foam separator as increased from 0.99 g/day to 2.5 g/day. But protein concentration ratio in the foam was decreased from 3.2 to 1.9. Changes of the removal amount and the concentration ratios of total suspended solid (TSS) and chemical oxygen demand (COD_cr.) were similar to proteins. The highest concentration ratios of TSS and COD_cr. were 10.2 and 8.4 at 2<TEX>$2\%$</TEX> of rearing density.

Growth and Production Characteristics of Palmetto Bass (Morone saxatilis female x Morone chrysops male) Reared at Three Densities in a Pilot-scale Recirculating Aquaculture System

Production characteristics of palmetto bass (Morone saxatilis female x Morone chrysops male) reared at three stocking densities (36 fish/m3, 72 fish/m3, and 144 fish/m3) in a pilot-scale RAS were evaluated. A final mean ±SE fish weight of 412.1 ± 7.8 g at the high density was significantly lower than that of fish at the medium density weighing 542.1 ± 11 .8 g (P