Ammonia Remover
Preventing crucial parameter to become number 1 problem in intensive culture. Used in fish transportation
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The dominant forms of nitrogen in wetlands that are of importance to wastewater treatment include organic nitrogen, ammonia, ammonium, nitrate, nitrite, and nitrogen gases. Inorganic forms are essential to plant growth in aquatic systems but if scarce can limit or control plant productivity.The nitrogen entering wetland systems can be measured as organic nitrogen, ammonia, nitrate and nitrite. Total Nitrogen refers to all nitrogen species. The removal of nitrogen from wastewater is important because of ammonia’s toxicity to fish if discharged into water courses. Excessive levels of nitrates in drinking water is thought to cause methemoglobinemia in infants, which decreases the oxygen transport ability of the blood.
Read more...Trickling filters have been used to filter water for various end uses for almost two centuries. Biological treatment has been used in Europe to filter surface water for drinking purposes since the early 1900s and is now receiving more interest worldwide. Biological treatment methods are also common in wastewater treatment, aquaculture and greywater recycling as a way to minimize water replacement while increasing water quality.
For drinking water, biological water treatment involves the use of naturally occurring micro-organisms in the surface water to improve water quality. Under optimum conditions, including relatively low turbidity and high oxygen content, the organisms break down material in the water and thus improve water quality. Slow sand filters or carbon filters are used to provide a place on which these micro-organisms grow. These biological treatment systems effectively reduce water-borne diseases, dissolved organic carbon, turbidity and colour in surface water, improving overall water quality.
The use of biofilters are commonly used on closed aquaculture systems, such as recirculating aquaculture systems (RAS). Many designs are used, with different benefits and drawbacks, however the function is the same -- reducing water exchanges by converting ammonia to nitrate. Ammonia (NH4+ and NH3) originates from the brachial excretion from the gills of aquatic animals and from the decomposition of organic matter. As ammonia-N is highly toxic, this is converted to a less toxic form of nitrite (by Nitrosomonas sp.) and then to an even less toxic form of nitrate (by Nitrobacter sp.). This "nitrification" process requires oxygen (aerobic conditions), without which the biofilter can crash. Furthermore, as this nitrification cycle produces H+, the pH can decrease which necessitates the use of buffers such as lime.
Source :
http://en.wikipedia.org/wiki/Biofilter
Species of the freshwater prawn genus Macrobrachium are distributed throughout the tropical and subtropical zones of the world. Holthuis (1980) provides useful information on the distribution, local names, habitats and maximum sizes of commercial (fished and farmed) species of Macrobrachium. They are found in most inland freshwater areas including lakes, rivers, swamps, irrigation ditches, canals and ponds, as well as in estuarine areas. Most species require brackishwater in the initial stages of their life cycle (and therefore they are found in water that is directly or indirectly connected with the sea) although some complete their cycle in inland saline and freshwater lakes. Some species prefer rivers containing clear water, while others are found in extremely turbid conditions. M. rosenbergii is an example of the latter. There is a wide interspecific variation in maximum size and growth rate, M. rosenbergii, M. americanum, M. carcinus, M. malcolmsonii, M. choprai, M. vollenhovenii and M. lar being the largest species known. M. americanum (Cauque river prawn) is found naturally in western watersheds of the Americas while M. carcinus (painted river prawn) is found in those connected with the Atlantic. M. choprai (Ganges river prawn) is found in the Ganges and Brahmaputra river systems. M. lar (Monkey river prawn) is native from East Africa to the Marquesas Islands of the Pacific (and was introduced into Hawaii). M. malcolmsonii (monsoon river prawn) is found in the waters of Bangladesh, India and Pakistan. M. rosenbergii (giant river prawn) is indigenous in the whole of the South and Southeast Asian area as well as in northern Oceania and in the western Pacific islands. M. vollenhovenii (African river prawn) is naturally distributed in West Africa, from Senegal to Angola. Many Macrobrachium species have been transferred from their natural location to other parts of the world, initially for research purposes. M. rosenbergii remains the species most used for commercial farming and consequently is the one which has been introduced to more countries. Following its import into Hawaii from Malaysia in 1965, where the pioneer work of Ling (1969) was translated into a method for the mass production of postlarvae (PL) by Fujimura and Okamoto (1972), it has been introduced into almost every continent for farming purposes. M. rosenbergii is now farmed in many countries; the major producers (>200 mt) are Bangladesh, Brazil, China, Ecuador, India, Malaysia, Taiwan Province of China, and Thailand (FAO 2002). More than thirty other countries reported production of this species in the year 2000. Viet Nam is also a major producer, according to New (2000b). In addition, there are also valuable capture fisheries for M. rosenbergii, for example in Bangladesh, India, and several countries in Southeast Asia.
by
Michael B. New
Marlow, United Kingdom
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 2002
Farming freshwater prawns
A manual for the culture of the giant riverprawn (Macrobrachium rosenbergii)
A freshwater prawn farm is an aquaculture business designed to raise and produce freshwater prawn or shrimp1 for human consumption. Freshwater prawn farming shares many characteristics with, and many of the same problems as, marine shrimp farming. Unique problems are introduced by the developmental life cycle of the main species (the giant river prawn, Macrobrachium rosenbergii) The global annual production of freshwater prawns (excluding crayfish and crabs) in 2003 was about 280,000 tons, of which China produced some 180,000 tons, followed by India and Thailand with some 35,000 tons each. Additionally, China produced about 370,000 tons of Chinese river crab.
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