Use Biofilter to Minimize Nitrogen Waste

The potential of seaweed applications as biofilter in closed\r\naquaculture systems, especially in the recirculation system.

The aquaculture industry has been developing rapidly all\r\nover the world, resulting in the consequences of waste water sources that are\r\ncausing significant impacts on the environment. In\r\nparticular, Nitrogen and phosphorus are the two main waste\r\ncomponents in aquaculture, studies show that only 25-30% of nitrogen, 15-20% of\r\nphosphorus is absorbed and most is excreted. environment (FAO,\r\n1992). Recognizing this urgent problem, many environmental policies in\r\naquaculture have been applied worldwide to treat waste water.

Therefore, reusing water is one of the solutions to protect\r\nthe environment, and besides, farmers can take advantage of waste to create\r\nvalue-added products. By applying the nutrient uptake ability of seaweed\r\nspecies can help solve oxygen problems as well as the accumulation of toxic\r\ncomponents in culture systems (Van Rijn, 1996).

Seaweed Ulva prolifera (OF Muller, 1778) is one of\r\nthe types of seaweed have economic value high, it is reported that Ulva\r\nprolifera source of vitamin abundant and particularly vitamin B12 higher\r\nthan other types of Other seaweeds (Watanabe, 1999). In addition, this\r\nseaweed has the ability to absorb and assimilate nutrients in water strongly\r\n(Cohen Risa, 2006). Therefore, Ulva prolifera is highly\r\nappreciated in exploiting the potential of waste minimization in aquaculture\r\nand especially in closed circulating systems.

In this study, seaweed was used as a biofilter in\r\ncombination with a closed farming system to minimize nitrogen in aquaculture,\r\nthe subject being Japanese orangefish.

To accomplish this goal, two continuous experiments were\r\nperformed.

Experiment 1: Two closed scale farming systems have\r\nbeen designed and installed to evaluate the application effectiveness of\r\nseaweed. Each system includes aquarium (800L), settling tank (900L) and\r\nseaweed culture (200L), the total volume of each system is 1900L.

The fingerlings are naturally sourced, caught and raised\r\ndirectly at Usa Biological Research Institute using synthetic feed. In\r\nthis experiment, each culture tank was stocked at a density of 22con / m3 with\r\nan average weight of 122g / head.

Accordingly, the wastewater from the fish tank is sucked\r\ndirectly from the bottom of the tank and flows through the settling tank to\r\nremove solid waste before being pumped to the seaweed tank with a 22L / min\r\npump. Wastewater from the culture tank through the seaweed tank will be\r\ncirculated back to the aquarium, the cycle is designed about 16 times / day to\r\nensure the amount of waste is removed completely.

The results showed that the addition of seaweed as a\r\nbiofilter in the culture system effectively reduced the amount of ammonia\r\nreleased from the fish. However, the optimal application of seaweed in\r\nclosed farming systems as well as combined economic efficiency has not been studied\r\nspecifically.

In the second experiment, different seaweed densities\r\nwere tested to find the optimal density when applying this seaweed in the\r\nculture system. Thereby, six seaweed densities were tested including 12g /\r\nL, 6g / L, 2g / L, 1g / L, 0.5g / L and the control treatment of 0g /\r\nL. Water samples were taken every 3 hours after the start of the\r\nexperiment.

Results measured nitrite or nitrate levels reached in\r\naquarium shows, nitrite and nitrate are absorbed rapidly after the addition of\r\nseaweed. Absorption efficiency depends on the density of seaweed\r\ncultured. After 6 hours of experiment, more than 80% of nitrite was\r\nabsorbed at seaweed density from 6 g-12 g / L after 3 hours of experiment, much\r\nhigher than the lower densities and controls.

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Preliminary research results show that the ability of Ulva\r\nprolifera to absorb nitrogen emissions such as ammonia, nitrite and\r\nnitrate directly helps ensure safe water quality in closed orange orange\r\nfarming system. copy. In addition, factors such as oxygen and pH content\r\nalso improved steadily. In addition, the research results also show the\r\npotential of seaweed application as a biofilter in closed aquaculture systems,\r\nespecially in the circulatory system.

Source: Tepbac