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Možnosti zachycení a recyklace živin při vypouštění rybníků
DOFEK, Jan
This diploma thesis tries to verify the possibilities of effective retention of sediments and nutrients from the run-off water during harvesting of ponds. Retention was tested using a system of two barriers made of organic material looking to temporarily count down water in the drains and extend the water residence time to sediment the particles. Monitoring of water quality was demonstrated on eight ponds in the South Bohemian Region, which manages fisheries company the Blatenská ryba, s.r.o. The following parameters were monitored: Undissolved substances 105; 550, total and dissolved phosphorus, total nitrogen, total carbon, total organic carbon, BOD5, CODCr, calcium, magnesium, potassium, large iron and dissolved. Water samles were processed in the laboratories of the state enterprise Povodí Vltavy in České Budějovice. Evaluation of results based on the evaluation of nutrient content in water and sediment samples on the profile under the dam (profile A) and under the other barrier (profile B). The flow of water over two hundred barriers increased the water quality. There was a statistical decrease earlier in all monitored parameters. The difference between the values of the values on profile A under the pond and under the other barrier (profile B) was not confirmed only in Fedissolve and at Pdissolve., at any time to increase their concentration. During the discharge of water from the pond and during the actual fishing of water to increase all monitored parameters. The highest values of concentrations were found at the end of BOD5, US105, US550, Fe and Fedissolve. The highest values during fishing are caused by the active movement of fish, people in catch basin.and with the crawling of fish, the pulling of the net, the lifting of the roofs of the net and the core. By flowing through the barriers, the concentration in the effluent water was reduced by up to 50%. Retention of up to 90% was possible for individual parameters (TP). According to these experiences, the efforts of operators should be to capture nutrients, especially from the start of fishing to the start of discharge and stopping the outflow of water, when it is possible to significantly eliminate their leakage into the basin. On average, 9,834 kg.ha-1 of sediment (in the raw state) was published. In this amount of sediment, 1015.89 kg of total nitrogen (22.3 kg.ha-1), 206.04 kg of total phosphorus (4.47 kg.ha-1), 294.11 kg of potassium (6.56 kg.ha-1), 1,097.92 kg calcium (23.58 kg.ha-1) and 10,108.63 kg received (220.69 kg.ha-1). The perceived sediment contained an average of 4.47 kg.ha-1 phosphorus. Dissolved phosphorus is a key parameter in the problem of eutrophication. The results of the water do not show that the catch of the pond is not such a serious problem in terms of dissolved phosphorus. During catches, the bound form of phosphorus predominated, with a share of 99%. The results, according to the objectives, can be used to capture the technology of sedimentation and nutrients in the run-off water when fishing ponds. Barriers made of organic material are able to retain and sediment nutrients from running water from ponds. This makes it possible to improve the quality of water discharge when fishing for ponds.
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Jak se mění kvalita vody na odtoku z rybníků při jejich výlovu
VÁGNER, Martin
The goal of this diploma thesis was to characterise the change of pond effluent quality during fish harvesting period. The change of water quality variables were measured and the pond draining stage at which fish harvesting activities affect most the quality of pond effluent was identified. Results and observations should help with the development of technology for retaining the sediment and nutrients discharged from ponds during fish harvest. The monitoring of pond effluent quality was carried out in twelve ponds managed by Krajské školní hospodářství České Budějovice in South Bohemian region. At different fish harvest phases, water temperature, concentration of dissolved oxygen, conductivity, turbidity and pH were measured in situ with a multiparametric probe YSI EXO 2. At the same time, water samples were also taken to quantify the concentration of suspended solids (SS), total phosphorus (TP), particulate and dissolved phosphorus (PP, DP) and total nitrogen (TN). Water samples were processed in the laboratories of the state enterprise Povodí Vltavy in České Budějovice. Our results confirmed that draining and fish harvest have significant influence on the quality of both the pond effluents and probably on the water bodies located downstream of the ponds. The largest changes of monitored parameters were caused by the time of active movement of fish and people in fish harvesting area. The active movements include setting the tanks for fish sorting, fish scaring, and seining. The highest concentrations of suspended solids, total phosphorus and total nitrogen were detected at the stage of catching fish with hand nets and surface outflow after the end of fish harvest. The changes of values during the fish harvest were considerable (% higher than pond water) and was fast. Therefore, best management practices aiming at reducing the concentration of SS, TP and TN may be implemented starting from the stage of fish netting until the closure of the pond outlet. Dissolved phosphorus has been identified as the key parameter causing eutrophication. The results of our study revealed that fish harvest is not so important problem from this point of view. During fish harvests obviously dominated particulated phosphorus which part was in average more than 99 %. The quality of effluent discharged during fish harvest was mainly influenced by the biomass and type of fish. Weather, water level regulation and type of outlet device influenced the effluent quality as well but at a lesser extent.
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Environmental conditions during the carp pond harvesting
PAVLÍČEK, Michal
Pond harvesting is an integral part of fish farming procedures in pond culture and overall fish production. This study was aimed at the evaluation of environmental conditions during pond harvesting, based on the comparison of values monitored in the trawl-net with fish located in a harvesting pit and outside it. The monitored parametres comprised the oxygen content and saturation, temperature, pH, conductivity and turbidity. The monitoring was performed on three autumn harvests (Potěšil, Rod, Jaroslavický dolní) and two spring harvests (Vrbenský přední and Vrbenský nový), always during the fish removal from the net (seine). The monitored determinants were recorded in 30-min intervals inside the net with fish and outside it in 15m distance. During the statistical comparision of the oxygen content and saturation in the net and outside it with the count on fish biomass was statistically signifiant differences in the four of twelve raids evaluated, which means keeping fishes in the net during the yielding was adequately treated by installation of fresh water jet.When the fresh water jet had been stopped worsen of the conditions in the fish net and even in the harvesting pit appeared.
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