Commercial pond fish culture using waste water

Waste water from some National Electric Power Authority (NEPA) housing units in Nigeria was fed to a 0.4 ha pond which was stocked with 2,200 Sarotherodon galilaeus fingerlings with a mean weight of about 36.0gm and 1000 Cyprinus carpio fingerlings with a mean weight of 10gm. This yielded after 10 months, over 2300 kg of harvestable fish plus over 20,000 Sarotherodon galilaeus fingerlings. The growth rate of C. carpio was not very encouraging possibly because of the type of plankton that colonised the pond. The S. galilaeus became stunted because of overpopulation as there were no carnivores to control their excessive breeding. The physico-chemical parameters were favourable for the growth of fish food organisms

Feeding and waste management strategies in the culture of Clarias gariepinus

Nutrient digestibility and amino acid availability were assessed in sharp-toothed catfish, Clarias gariepinus, fingerlings fed diets containing soyabean flour (SF) - Poultry meat meal (PMM) blends (25:75. 50:50, and 75:25) and 0.5 of 1.0%, Cr sub(2)0 sub(3). There was agreement between the pattern of overall protein digestibility and average amino acid availability despite the variability in individual amino acid availability the best dry matter, lipid and protein digestibility coefficients, and amino acid availability values were obtained with diets containing 0.5% Cr sub(2)0 sub(3). Chromic Oxide inclusion level appeared to affect nutrient availability. Increased marker level resulted into decreased nutrient digestibility coefficients. Similarly, these diets generated lower fecal crude protein than those with 1.0% Cr sub(2)0 sub(3). However, the latter group recorded higher protein retention efficiency. Dry mailer and lipid of diets containing more soyabean flour seemed to be more digestible than those of poultry meat meal. Similar trend was observed for the apparent availability of the amino acids. This investigation has indicated that low level of marker was better in digestibility study. Utilization of more SF than PMM in the diets of this catfish was more beneficial and should be encouraged in the feed industries producing catfish diets towards a better feed and waste management strategies in this aquaculture operation

THE FORMATION MECHANISM OF THE VITRIFIED SLAG IN A PLASMA ARC REACTOR FOR HAZARDOUS WASTE TREATMENT

Various hazardous wastes with additives have been vitrified to investigate the formation mechanism of the glassy slag by a 30 kW DC plasma-arc reactor developed by the Institute of Mechanics, Chinese Academy of Sciences. The average temperature in the reaction area is controlled at 1500°C. The chemical compositions of three sorts of fly ashes are analyzed by XRF (X-Ray Fluorescence). Fly ashes with vitrifying additives can be vitrified to form glassy slag, which show that the ratio of the whole oxygen ions to the whole network former ions in glass (R) is appropriate in the range of 2~3 to form durable vitrified slag. In this experiment, the arc power is controlled below 5 kW to inhibit waste evaporation. To enhance the effects of heat transfer to wastes, ferrous powder has been added into the graphite crucible, which aggregates as ingot below the molten silicate after vitrification. The slag fails to form glass if the quenching rate is less than 1 K/min. Therefore, the slag will break into small chips due to the sharp quenching rate, which is more than 100 K/sec.

Application of algal bioassays in the determination of eutrophic power of waste water (”Conclusions” only) [Translation from: 1g.Sanita pubbl. 31 257-267, 1975]

The best evidence for establishing the level of eutrophy of a water-body is its algal production which makes it possible to identify the type and the intensity of the eutrophication according to the kind and number of algal species present: when the number of algae exceeds half a million per litre then one speaks o an ”algal bloom”. The scope of the present research aims to verify if the alga Selenastrum capricornutum can be used as a test alga under our culture conditions and to determine the eutrophic level of the secondary effluent of a modern plant for the treatment of domestic discharge and to investigate the eventual ”limiting factors”. Finally this paper aims to study the effect on the secondary effluent of tertiary treatment carried out artificially in the laboratory.

Aquaculture of a high-value freshwater fish in [Malaysia] : the marble or sand goby (Oxyeleotris marmoratus, Bleeker)

The article highlights the aquaculture of marble or sand goby (Oxyeleotris marmoratus) in Malaysia. Topics discussed are: breeding, hatchery and nursery techiques, nutrition, growout techniques, and diseases.