Mathematical model and experimental validation for the prediction of dissolved oxygen saturation in aquaculture ponds

Fluid mechanics is one of the oldest areas of physics with the greatest number of applications in everyday life. This area became more versatile when mass and energy transport equations were incorporated. Together, these equations allow describing a wide variety of case studies with great precision. Among cases available in the open literature, aquaculture is one of the most important due to the growing need for food sources for human consumption, the nutritional value of many fish varieties, the low cost of the maintenance of fish farms. Dissolved oxygen is one of the most relevant parameters ensuring water quality in fish farming. Many fish farms use permanent artificial aeration systems for maintaining the oxygen level within the recommended range used, causing an increasing energy consumption. Therefore, this work proposes an equation and validation, based on equations hydraulics and transport phenomenon, capable of determining the maximum concentration of dissolved oxygen in the body from the operating parameters of the tilapia rearing pond.

Application of Aeration Injection to Increase Dissolved Oxygen of Surface Water in The Floating Net Cage

Cirata Reservoir is a place for fish cultivators who mostly cultivate tilapia using floating net cages. However, water quality conditions, especially dissolved oxygen levels, which play an important role in tilapia culture in floating net cages are always uncertain and affect the growth of tilapia. Therefore, artificial aeration is needed that is able to increase dissolved oxygen levels so that it is suitable for tilapia culture by using Aearator Dua Lapis (ADL) engine. This study aims to inject dissolved oxygen into the surface layer of the reservoir by applying the ADL engine with gasoline. ADL operated at 1800, 4500, and 5500 rpm with a torque of 3.5 N/m2 and the DO value is recorded every 10 minutes up to 1440 minutes, the results of DO value were recorded and analyzed by using descriptive statistic and statistically using ANOVA with a single factor showed that the rotation has a very significant effect on the resulting DO value (p<0.01). For ADL operation in floating net cages, 4500 rpm rotation was used at certain depth (0.4 m; 1 m; 1.5 m) and the DO value measured at 4.00 am to 2.00 am (22 hours) in aerated floating net cages and without aerated floating net cages.Aerated floating net cages have a higher DO value, especially at a depth of 0.4 m. ADL as an aerator in floating net cages has a very significant effect (p<0.01) in increasing the DO value in floating net cages at a depth of 40 cm to 1.5 m. This proved that the use of ADL is able to increase the DO value in floating net cages in the first layer with a depth of up to 4 m and ADL also can be used as emergency aeration or supplemental aeration for tilapia culture.

The impact of aeration on ecological state of lake Telbyn in Kyiv

Lake Telbyn is considered to be one of the largest lakes located in the eastern part of Kyiv. The artificial aeration of this lake was started at the end of 2016 by using of 8 aerators, which has been continuing so far. The main perpose of this measure is improving the ecological state of the lake mostly for recreational use. There were carried out a field study of the lake and the analysis of remote sensing data. Physical and chemical characteristics of water, phytoplankton biomass, chlo- rophyll a concentration and some other parameters at the different depths were studied. It was found out that artificial aeration has a positive effect on the ecological state of the lake. The water aeration causes the blur of thermocline whereas the impact on its depth is not essential. Under impact of aeration the concentration of dissolved oxygen become larger, mostly in the bottom layer. The highest concentration of ammonium nitrogen in a warm period is observed in the bottom layer of the lake. The deep location of aerators causes the increasing of concentration in bottom layer. At the same time there is not visible impact on concentration near the surface. The similar result was obtained for the concentration of inorganic phosphorus. The impact of aeration on algal bloom is not such essential as on hydrochemical characteristics. The artificial aeration causes negative impact on the phytoplankton abundance and less effect on their biomass. It means the larger effect on the algae with small cells. In other words the aeration has larger impact on green algae than on blue-green ones. The use of remote sensing data showed that ecological state of Lake Telbyn during the aeration period improved comparably with other lakes of Kyiv. As a result of aeration, the view of water surface of the lake became more similar to water surface of the Dnipro River, which flows through the city.

EFEITO DA TAXA DE AERAÇÃO NO DESEMPENHO DE ALAGADOS CONSTRUÍDOS AERADOS INTERMITENTEMENTE

EFEITO DA TAXA DE AERAÇÃO NO DESEMPENHO DE ALAGADOS CONSTRUÍDOS AERADOS INTERMITENTEMENTE JOÃO GABRIEL THOMAZ QUELUZ; LAUREN NOZOMI MARQUES YABUKI E MARCELO LOUREIRO GARCIA Instituto de Geociências e Ciências Extas, Universidade Estadual Paulista, Avenida 24 A,1515, CEP: 13506-900, Rio Claro, SP, Brasil. [email protected]; [email protected]; [email protected] 1 RESUMO O presente trabalho foi conduzido com o objetivo de avaliar o efeito de diferentes taxas de aeração na remoção de nitrogênio total (NT) e demanda química de oxigênio (DQO) em alagados construídos de fluxo subsuperficial horizontal (ACFH) aerados intermitentemente. Para isso, foram avaliados quatro ACFH em escala piloto utilizando diferentes taxas de aeração (0; 2; 5 e 10 L min-1) com intervalo de aeração intermitente fixo de 3 h d-1 (1h com aeração/7 horas sem aeração). Os sistemas receberam 8,6 L d-1 de efluente sintético, resultando em tempo de detenção hidráulica de 3 dias. Os resultados mostram que os ACFH aerados intermitentemente apresentaram elevada eficiência na remoção de DQO (>97%), NT (>80%) e NH4+ (>97%), enquanto o ACFH sem aeração apresentou menor eficiência na remoção de DQO (93,9%), NT (48,8%) e NH4+ (57,7%). Adicionalmente, os resultados também mostram que os três ACFH aerados intermitentemente obtiveram desempenho similar na remoção de DQO, NT e NH4+. Finalmente, os resultados permitem concluir que a aeração intermitente permite a ocorrência simultânea da nitrificação e da desnitrificação, aprimorando, assim, o desempenho dos ACFH na remoção de NT. Entretanto, o uso de diferentes taxas de aeração não altera a eficiência de remoção de NT e DQO. Palavras-chave: aeração artificial, remoção de DQO, remoção de nitrogênio. QUELUZ, J. G. T.; YABUKI, L. N. M.; GARCIA, M. L. EFFECT OF AERATION RATE ON THE PERFORMANCE OF INTERMITTENTLY AERATED CONSTRUCTED WETLAND 2 ABSTRACT The aim of the present work was to evaluate the effect of different aeration rates on the removal of total nitrogen (TN) and chemical oxygen demand (COD) in intermittently aerated horizontal subsurface flow constructed wetlands (HFCW). Four pilot-scale HFCWs were evaluated using different aeration rates (0, 2, 5, and 10 L min-1) with a fixed intermittent aeration interval of 3 h d-1 (1 h with aeration / 7 h without aeration). The HFCWs received 8.6 L d-1 of synthetic effluent, resulting in a hydraulic retention time of 3 days. The results show that intermittently aerated HFCWs were highly efficient in removing COD (>97%), TN (>80%) and NH4+ (>97%), while the HFCW without aeration showed lower efficiencies in the removal of COD (93.9%), TN (48.8%), and NH4+ (57.7%). In addition, the results also show that the three intermittently aerated HFCW achieved similar performance in the removal of COD, TN, and NH4+. Finally, the results indicate that intermittent aeration allows the simultaneous occurrence of nitrification and denitrification, thus improving the performance of HFCW in removing TN. However, the use of different aeration rates does not alter COD and TN removal efficiencies. Keywords: artificial aeration, COD removal, the nitrogen removal.

Artificial aeration promotes better zootechnical performance and physiological balance of tambaqui (Colossoma macropomum) cultivated in a system without continuous water flow (Amazon: Brazil)

The aimed of the study was to evaluate the effect of continuous artificial aeration on zootechnical performance, hematological characteristics and glucose concentration of tambaqui (Colossoma macropomum) cultivated in a system without water flow. The study was conducted with two treatments, with aeration and without artificial aeration. Were 600 tambaqui juveniles with an average initial weight of 15 ± 0.15g were distributed in two excavated tanks. Thirty fish were captured per cultivation unit to perform monthly biometric measurements and were subjected to blood collection to determine hematological parameters. There was no difference between hematological variables (p<0.05). However, the continuous use of artificial aeration provided fish with more comfortable conditions, resulting in greater performance (p<0.05) in up to 90 days of cultivation, with an average daily weight gain of 4.82 g compared to 4.49g to the system without artificial aeration. It can be inferred that fish grown in a system without artificial aeration presented, when compared to those raised in a system with continuous artificial aeration, smaller values (p<0.05) of growth, both in weight and in length, consequently the continuous use of the aerator provided favorable conditions for the fish, resulting in average daily weight gain and total biomass gain.

Shrimp farming with pen enclosures in south Brazil.

Native shrimp farming has been considered as an important alternative source of income for artisanal fishers and farmers in the Patos Lagoon estuary, southern Brazil. Considering the potential of estuarine areas for shrimp farming, the application of a low-cost structure to culture shrimp such as a pen is being proposed to complement capture fisheries and agriculture. From an economic standpoint, the use of pens has several advantages over a traditional pond-based culture system as land, water pumping and artificial aeration devices are not required. Relatively inexpensive materials may be employed for pen construction and running costs are minimized by the use of by-products from capture fishing to feed shrimps. These factors represent important points in lowering costs, which may turn small-scale shrimp farming into an economically feasible activity. Although this activity is in its initial stages of development, there is a strong tendency for the spread of this practice in coastal lagoons and estuaries in southern Brazil.

Combining artificial aeration and biological zeolite mulch for nitrogen removal from eutrophic water bodies

Endogenous nitrogen pollution can be a major cause of eutrophication. Nitrogen species release from sediments can be reduced by biologically-enforced zeolite mulch or water column aeration. This study was about their combined effects. Water and surface sediment samples from the Yangzhou ancient canal were aerated and biozeolite mulching was applied separately and in combination for 81 days, while the nitrogen species removal rate was recorded. The combination of aeration and biozeolite mulching removed &gt;95% of the ammoniacal-nitrogen in 15 days. This was better than either the blank control or biozeolite mulch without aeration. The ammoniacal-nitrogen concentration was lowered faster by combined treatment than by aeration alone. Nitrate nitrogen was only detected during aeration between days 10 and18, and reached lower concentration in the presence of biozeolite. Nitrate was formed during aeration but its concentrations were higher and more variable in the absence of biozeolite; that is, mulching stabilized nitrate formation. The total nitrogen concentration reached its lowest levels after 81 days with biozeolite treatment alone, with 78% total nitrogen removal, whereas combined aeration with biozeolite achieved 41%. This shows that biozeolite mulching can remove nitrogen in eutrophic waters, even without aeration.