A combined intensive-extensive fishpond system developed for the purification and re-use of intensive fishpond effluent water was studied during a three-year experimental period. The investigated pond system consists of five small-size intensive culture ponds of 1 ha total water surface area with 1.5 m water depth and a 20 ha extensive culture...pond with 1.0 m average water depth. The water was recirculated between the intensive and extensive ponds with around 60 days retention time in the extensive treatment pond.
Carbon, nitrogen and phosphorus budget and water purifying capacity were described and evaluated by means of regular measurements of nutrient concentrations in the water and sediment. During the three-year test period, 81.5% of organic carbon, 54.7% of nitrogen and 72.2% of phosphorus were retained by the system as a percentage of the total input of each nutrient. A significant amount of the total nitrogen input was removed by the harvested fish, which was much higher than in traditional fishponds or intensive fish culture systems. The efficiency of nutrient removal is clearly indicated by the 27.3% nitrogen assimilation.
Only a small percentage of the total nutrient input was discharged into the environment during fish harvest, which was 9.0% for organic carbon, 13.2% for nitrogen and 12.1% for phosphorus. The combination of intensive and extensive fishponds with water recirculation resulted in significant reduction of nutrient discharge into the surrounding aquatic environment, primarily due to the high nutrient processing and retention capacity of the extensive fishpond ecosystem.
The selenium is an essential trace element with antioxidant effect, constituent of many enzymes, natural component of the body of the animals. The addition to the fish feed as micro element supplementation is generally accepted. Numerous animal experiments veryfied, that the antioxidant effect of the nanoselenium is higher than other selenium f...orms. But no much information is available of the usuage at fish.
In the experiment were investigated the effects of the nanoselenium supplementation of a commercial fish feed were investigated to the production parameters and the body tissue composition. The correlation between the accumulated selenium content of the body and the treatment, and the feed conversation was also statistically analyzed beside the production parameters. Furthermore we were curious, if can be toxic the nanoselenium in higher doses.
The experimental stock was placed into 12 plastic tanks (each 70 l water vol.) in a recirculation system for larval rearing. The salinity and the water temperature was constant during the 8 week long experiment. The feeding was ad libitum, 4 times a day. Beside the control five (1, 1.5, 2.5, 5.5, 10.5 mg Se kg-1) duplicated treatment were set.
According to the results, from the production parameters only at the value of FCR and the survival was found significant difference (p<0.05) between the groups. However strong correlation (r=0.752–0.780, p<0.01) was determined between the treatment and the accumulated selenium levels. To analyzed the free fatty acid contentof the fish, we realized, that the selenium uptake significanly enhanced this level at all treatments. The greatest change was found in case of the type n-3 fatty acids.
Established by the results, the higher intake than 0.5 mg Se kg-1 was not changed significantly the production parameters, nevertheless to increase the selenium content of commercial feeds to 1.5 mg Se kg-1 could be rewarding on the rearing of red drum.
The sewage sludge compost is suitable to improve the colloid-poor sandy soils, which are common characteristics of poor water- and nutrientholding capacity. The general characteristics of sandy soils are the light mechanical composition, the low content of humus and mineral colloids, large pore size and a bad aggregate stability. They have a po...or nutrient supply capacity, due to its high porosity the organic matter is degraded very quickly to mineral colloids (Stefanovits et al., 1999).
By the compost application the soil is enriched mineral and organic colloids, thereby improving the soil structure. The effect of addition of compost to soil the water- and nutrient-holding capacity and porosity could be increased and the bulk density could be decreased (Martens and Frankenberger, 1992).
The aim of our experiment is to carry out physical measurements to determine the effects of compost treatment. In this study the results of the first year are presented.
The aim of the research was a development of a featherdegradation technology in industrial circumstances. During the experiments we determined the parameters of the critical environmental and technological limitation factors. Because of the high keratin-content the degradation (and composting) of the feather is difficult. With the developed tec...hnology huge mass of feather can be used fast and easily in biogas production and in the adjustment of the optimal element ratio of biomass. The industrial experiments were implemented in a 6m3 heatable double-walled
tank with stirring-shovels and aeration-system. The degradation process was followed with extinction measurements.
According to the experiments that were done the best results were given at the case which was heat-treated at 70°C, was injected with 1% bacteria concentration, and where 1:3 feather:water ratio was set if we consider the effectiveness of degradation and the hydraulical retention time.