The objective of the present study is to develop an eco-friendly aquatic feed to reduce phosphorus (P) loading, in large rainbow trout. Gain in fish mass, nutrient digestibility, non-fecal P excretion, P retention and loading were compared among triplicate groups of fish reared with a P-sufficient (commercial feed), a previously-developed P-deficient (Aquaculture Collaborative Research and Development Program, ACRDP diet) and an experimental diet formulated with low level of domestic fish meal (herring meal, 150g/kg diet) and low-P ingredients: Hamlet soy concentrate (110g/kg diet), corn gluten meal (250g/kg diet), feather meal (120g/kg diet), blood meal (100g/kg diet) and whey powder (50g/kg diet). The total P content was 10.7g/kg, 3.7g/kg and 4.7g/kg, for the P-sufficient, P-deficient and experimental diet, respectively. Fish (initial average mass 314.7±5.9g) were fed in triplicate tanks per diet for 60days. At the end of the trial, gain in fish mass and thermal growth coefficient (TGC) were comparable among fish from different treatments. With the exception of the P-deficient diet (higher FCR), feed conversion ratio (FCR) was not (P>0.05) influenced by diets. Coefficient of total tract apparent digestibility (CTTAD) of P and P retention were higher (P<0.05) in fish fed the experimental diet than commercial feed. The maximum non-fecal soluble P accumulation curve and concentration were different (P<0.05) and mainly affected by dietary P. The fecal P content was found to be lower (P<0.05) in rainbow trout fed the experimental diet (10.6mg/g dry fecal matter) than commercial feed (24.3mg/g dry fecal matter). Non-fecal P excretion was higher (P<0.05) in fish fed commercial feed (6.22g soluble P/kg dry diet) than experimental diet (2.20g soluble P/kg dry diet). Moreover, estimated P loading was lower (P<0.05) for the experimental diet than the commercial feed (3.98kg/ton of fish produced versus 11.07kg/ton, respectively). The present study demonstrates that for large rainbow trout, low P loading diet can be formulated through an adequate and optimal combination of diverse and practical low-P protein ingredients.

Le RAQ regroupe des chercheurs québécois et leur équipe respective (étudiants et personnel) provenant de huit institutions universitaires (Université du Québec à Rimouski / Institution hôte, Université Laval, Université de Montréal, Université de Sherbrooke, Institut national de la recherche scientifique Institut Armand Frappier, École polytechnique de Montréal, École de technologie supérieure, Université McGill) et d’une institution d’enseignement collégial (Cégep de la Gaspésie et des Îles). Travaillant de concert avec ses principaux partenaires, la Société de développement de l’industrie maricole du Québec (SODIM), la Société de recherche et de développement en aquaculture continentale (SORDAC), le Ministère de l’Agriculture, des Pêcheries et de l’Alimentation (MAPAQ) et Pêches et Océans Canada (MPO), le RAQ a comme principaux objectifs de stimuler la recherche au Québec dans le secteur aquacole et de favoriser la collaboration entre chercheurs de disciplines diverses.

Forty-nine strains of filamentous, mat-forming cyanobacteria isolated from the Arctic, subarctic and Antarctic environments were screened for their potential use in outdoor waste-water treatment systems designed for cold north-temperate climates. The most promising isolate (strain E18, Phormidium sp. from a high Arctic lake) grew well at low temperatures and formed aggregates (flocs) that could be readily harvested by sedimentation. We evaluated the growth and nutrient uptake abilities of E18 relative to a community of green algae (a Chlorococcalean assemblage, denoted Vc) sampled from a tertiary treatment system in Valcartier, Canada. E18 had superior growth rates below 15°C Canada. (µ = 0.20 d- 1 at 10°C under continuous irradiance of 225 µmol photon m- 2 s- 1 ) and higher phosphate uptake rates below 10°C (k = 0.050 d- 1 at 5°C) relative to Vc (µ=0.087 d- 1 at 10°C and k = 0.020 d- 1 at 5°C, respectively). The green algal assemblage generally performed better than E18 at high temperatures (at 25°C, µ = 0.39 d- 1 and k = 0.34 d- 1 for Vc; µ = 0.28 d- 1 and k = 0.33 d- 1 for E18). However, E18 removed nitrate more efficiently than Vc at most temperatures including 25°C. Polar cyanobacteria such as strain E18 are appropriate species for waste-water treatment in cold climates during spring and autumn. Under warmer summer conditions, fast-growing green algae such as the Vc assemblage are likely to colonize and dominate, but warm-water Phormidium isolates could be used at that time.

The effect of the dietary incorporation of cassava leaves (Manihot esculenta Cranfcz) and peanut vines (Arachys kypogaea L.) on biomass production, final weight, mortality and feed conversion ratio of Clarias gariepinus (Burchell) was studied in a 10-week experiment. Two groups of diets were used: one group used cassava chips as the main energetic ingredient and cassava leaves (CL) as the crop residue, the other used corn as the energetic ingredient and peanut vines (PV) as the crop residue. Each group had diets with 0% (control). 10% or 20% crop residue incorporation. Comparison of the two controls (cassava or corn-based) showed that the cassava-based diet resulted in a significantly lower biomass and final weight (P < 0.01) and higher Teed conversion ratio. FCR (P < 0.05). There was no significant difference of biomass yield and final weight for the fish fed diets with 0%, 10%. and 20% CL diets. Fish fed 20% CL appeared to be more sensitive to diseases. Their mortality and FCR were significantly higher (P < 0.01) than those of the control. Incorporation of 10% or 20% PV did not affect any parameter when compared with the control. The results obtained in this experiment show that, for Clarias gariepinus under these conditions, a maximum of 10% cassava leaves can be incorporated in a cassava-chip diet. For a corn-based diet, incorporation of 20% peanut vines is possible.

Immobilization appears to be one of the best techniques to separate physically micro-algal cells from their culture medium for the purpose of algal tertiary wastewater treatment. High operation costs and other drawbacks of large-scale physico-chemical methods of harvest led to a comparative study of biotreatment systems. Before treatment began, Scenedesmus bicellularis cells were conditioned (starved) under four different sets of conditions: 1) non-immobilized cells with air bubbling (NCA); 2) cells immobilized in alginate beads (CBW) and 3) cells immobilized on alginate screens (CSW), all conditioned in synthetic culture medium depleted in N and P; 4) cells immobilized on alginate screens but conditioned in air at 100% relative humidity (CSA). Starvation was started under a light:dark photoperiod of 16:8 h. Starved cells were then used to treat wastewater for a 2-h period. The performance of each system was evaluated by determination of residual NH4-N and phosphate ions and by growth (dry weight, total chlorophyll, cell count, protein content). We then tested the capacity of microalgae immobilized on screens to eliminate N and P from a secondary municipal wastewater effluent and examined the influence of temperature and starvation. The quality of treated effluents was improved considerably with the system using CSA or CSW model. For CSA model, the protein content was 22.4 pg cell-1 compared to 12.9, 9.5, 9.1 pg cell-1 for NCA, CBW and CSW models, respectively. The CBW and CSW models were efficient for chlorophyll synthesis. The residual ammonium content in natural wastewater after 2 h of treatment with CSA model was 39% at 6±2 °C and reached 100% removal at 18±2 °C. With the first 2 h, the removal of orthophosphate was inferior (53%) at 6±2 °C, but 88 to 100% at 18±2 °C depending on starvation times. Long starvation times (72 or 96 h) caused damage to cells and uptake of nutrients was lower than with 54 h starvation. This work demonstrates that by using immobilization on screens, removal of nutrients from wastewater was higher than with conventional biological tertiary wastewater treatments (free cells or bead-shaped alginate particles).

When a reuse water system operates at high fish loadings and recirculation levels, a readily perofrming biofilter is of utmost importance. The present work aims at reducing the colonization time of nitrifying bacteria with the intention of creating a fully operational trickling biofilter upon the introduction of a substantial fish load into the system. A technique is developed by which the future fish biomass is simulated continuous injection of ammonium salts (25.5 ± 2.6 g H-NH4 +/m3 of iofilter media (432 to 1411 ky fish/liter per minute of makeup water) with a sustaining water quality. With a pH mainained between 9.0 and 8.5, a hydraulic loading rate of 130 m3/m2/d. inorganic nutrients and an inoculum of active nitrifiers, fully reliable biofilters were obtained within 9 days. The role of alkalinity, inoculum, and mineral nutrients is also discussed.

Microalgal cultures offer an interesting alternative for waste water treatment (urban, industrial or agricultural effluents) because they provide a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for several purposes. We review the main abiotic, biotic and operative factors playing a role in the cultivation of microalgae. Various types of bioreactors are scrutinized keeping in view that the main limitation upon the type of usable bioreactors is the enormous volume of water to be treated. The choice of suitable microalgae and cyanobacteria is examined in terms of productivity and easiness of harvesting. The possible alternatives to harvesting are also reviewed with an emphasis on immobilized systems. Finally, the need for more research and development is discussed.

Rainbow trout were fed two experimental diets differed in lipid content by replacement of crude starch (lipid-poor diet : 4.2% lipid or lipid or lipid-rich diet :14.8% lipid) supplemented or not with antibiotics (a combination Flumequine + Gentamycin, 1:4). The apparent digestibility of dry matter, crude protein, lipid, carbohydrate and total energy were measured. Addition of lipid by replacement of crude starch in the fish diet in the absence of antibiotics enhanced significantly (p<0.01) the apparent digestibility of dry matter, crude protein, carbohydrate and total energy, but did not influence those of lipid. Antibiotics supplementation of the lipid-poor diet (consequently with a high level of carbohydrate) enhanced significantly (p<0.01) the apparent digestibility of dry matter, crude protein, lipid, and total energy, but not those of carbohydrate. On the other hand the antibiotics-treated lipid-rich diet (consequently with a low level of carbohydrate) showed a higher (p<0.01) digestibility for dry matter, lipid, carbohydrate and total energy, but not for crude protein. The stimulatory effect of antibiotics on nutrient digestibility is discussed.

Under both laboratory-controlled and outdoor conditions, mass culture ofPhormidium bohneri has shown low growth rates and filament aggregate or floc instability. In order to test for a possible carbonaceous supply limitation, a mass transfer characterization study of the reactor used was conducted. To examine different conditions of aeration, the overall volumetric mass transfer coefficient, KLa(C02), and the energy and physical transfer efficiency for CO2 were determined for three air-flow rates and three types of diffuser. For the different aeration conditions studied, the reactor showed adequate mixing properties with respect to CO2. However, under low air-flow rate conditions, even with the most efficient diffuser, the CO2 transfer capacity appeared limiting. On the other hand, at high air-flow rates, floc breakage as a result of shear stress appeared to limit bioreactor efficiency.

Chitosan:Phormidium aggregates (chitosan: algae=1:2, dry weight basis) were used as a biological tertiary treatment to remove the nitrogen (NH 4 + , NO 2 - , NO 3 - ) and phosphorus (PO 4 3- ) from a secondary effluent. In a batch system, 71 and 92% of P−PO 4 3- were removed after 6 and 24 h, respectively. The orthophosphate removal rate was identical for all three concentrations of algae-chitosan tested (3.3, 4.6, 5.9 g d. wt.·l-1), and was 90 μg±2 μg P−PO 4 3- ·l-1·h-1, for a 90% removal. Under control conditions (chitosan flakes only added to the effluent) 73 and 78% of PO 4 3- were removed after 6 and 24 h respectively. A 95% removal of inorganic nitrogen (NH 4 + , NO 2 - , NO 3 - ) was attained after 4–6 h withPhormidium immobilized on chitosan flakes, as compared to 30% with chitosan flakes alone (5 g d. wt.·l-1). The system gave a similar performance when operated semi-continuously over 5 days at a daily retention time of 1.0. In the presence of chitosan-immobilized algae, medium P−PO 4 3- levels were reduced by 87.3%±6.4% after 24 h (61.1 μg±7.0 μg P·l-1·h-1). The reduction of inorganic nitrogen in the medium was 98% after 24 h (370 μg±50 μg N·l-1·h-1). In the presence of chitosan alone, some 60% orthophosphate removal was recorded, whereas no reduction of nitrogen was observed. Disappearance of orthophosphate was attributed to its co-precipitation with calcium released from the chitosan by abrasion. The presence of the algae protected the chitosan from abrasion andPhormidium directly assimilated the orthophosphate and inorganic nitrogen, thus reducing their levels in the effluent.

Bacillus subtilis, immobilized in carrageenan, was used to synthesize alpha-amylase in two media. In complete medium with organic nitrogen growth was more rapid during the first hours than in minimal medium without organic nitrogen, but the maximum bacterial density was the same for both media. The alpha-amylase activity was always higher in the complete medium and the difference was 25% at the end of the fermentation. To overcome oxygen diffusion problems, bacteria were co-immobilized with the microalga Scenedesmus obliquus. This resulted in an increase of enzyme activity by 20% in the complete medium and 26% in the minimal one. Increasing the algal/bacterial ratio invariably led to a higher final bacterial density, but high algal concentrations were associated with repression of alpha-amylase activity. Axenic immobilized microalgae grew slowly, but when co-immobilized with bacteria, the generation time was significantly reduced.

Les biomasses de microalgues, par leur haute teneur en protéines, vitamines et minéraux, recèle un intérêt indéniable pour les fins de l'alimentation, animale tout spécialement. Une installation-pilote de traitement tertiaire des eaux usées domestiques par culture de microalgues a été érigée à 80 km au nord de la ville de Québec (Canada). La productivité s'échelonne selon les saisons de 1,1 à 12,0 g d'algues (poids sec)/m2. d. Le coefficient de conversion de l'énergie solaire atteint 2,2%. Afin de résoudre les différentes contraintes d'ordre technique et économique en climat tempéré-froid, un concept technologique de bassins sous serre est proposé.

This study was aimed at examining the possibility of using Daphnia magna to recover the phytoplankton produced in high concentration during the biological treatment of wastewaters. Ingestion rate, assimilation rate and assimilation efficiency were measured for Daphnia grown under controlled experimental conditions in secondarily treated wastewaters. The rate of ingestion was higher at 15°C than at 20°C and depended on the high concentrations of algae (Oocystis sp.) used: 10 and 50 mg C litre−1. The rate of assimilation was constant at about 1·8 μg C per Daphnia per hour. It is proposed that the incipient limiting level of ingestion corresponds to the concentration where the assimilation rate is maximum. At food concentrations higher than this level of ingestion, Daphnia control mechanisms normally maintain a constant ingestion rate and prevent superfluous feeding. Our results revealed the inefficiency of these mechanisms at high food concentrations, leading Daphnia to superfluous feeding. Nevertheless, Daphnia reveals itself as a good candidate for the filtration of Oocystis produced in wastewaters.