Executive Summary 2007
Inventor Prof.. Jaap van Rijn, The Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem.
Fish perform all their bodily functions in water.Because fish are totally dependent upon water to breathe,feed and grow, excrete wastes, maintain a salt balance, and
reproduce,understanding and controlling the quality of water is critical to successful aquaculture. To a great extent, water determines the success or failure of an aquaculture operation.
In recent years,aquaculture (cultivation of fish or other aquatic organisms) is characterized by the tendency towards growing more fish per area unit.
As opposed to conventional fishponds, water quality deterioration proceeds rapidly in these intensive fishponds and without man-made interference, fish mortality would be imminent.
Theoretically, two options exist as to maintaining an adequate water quality in these intensive fish culture ponds:
1. The ponds are continuously flushed with clean (unpolluted) water.
2. The pond water is continuously treated in order to reduce the level of pollutants.
Unlimited amounts of clean water to flush the ponds is a luxury which is restricted to few geographical areas only, and cause considerable environmental pollution.
Therefore, treatment of the pond water is the option of choice.
BGT (Bio Group Technologies Ltd) is the company for development, production and commercialization of a fully closed system for intensive fish culture.
This technology, developed by Prof. van Rijn, comprises indoor fish culture tanks operated in a fully recycling mode. This recycling is achieved by the combined use of two kinds of biofilters.
Based on studies on four pilot plants:
zero-discharge system pilot plant for freshwater fish at Ginosar Experimental Station, Israel;
A marine zero-discharge re-circulating system pilot plant at the Faculty of Agriculture of the Hebrew University, Rehovot, Israel,
A marine zero-dischargere-circulating pilot plant at the National Center for Mariculture, Eilat, Israel) was shown that fish could be grown at high densities in a
completely closed environment without discharge of water and of organic waste products to the environment; and without accumulation of toxic intermediates in the
fish ponds. Results of these studies were published in various scientific journals over the years.
A Commercial Plant-Zero-Discharge Closed-System for growing ornamental fish, Herev Leet, Israel.
The system will allow the fish farmers to enjoy the following benefits:
-Fish densities of up to 70kg/m3
-More than 95% water saving as compared to conventional, extensive systems
-All-year-round fish culture
-Inland marine fish intensive culture
-Grown sea fish closer to their markets
II. The Technology
The accumulation of inorganic nitrogen in intensively cultured fishponds is one of the major limiting factors preventing further intensification.
Inorganic nitrogen (especially ammonia and nitrite) is toxic to fish, and it accumulates in the pond water through excretion of ammonia by the fish and by breakdown of organic solids.
Most of the treatment systems used in aquaculture facilities today are designed to facilitate the growth of nitrifying bacteria which convert ammonia to nitrate.
A drawback of the ammonia removal by means of nitrification, is the subsequent increase in nitrate in the culture system.
High nitrate concentrations ought to be prevented for several reasons:
-Nitrate at high concentrations has a toxic effect on fish.
-The discharge of nitrate-rich effluent water is prohibited in many countries due to environmental and public health considerations.
-Nitrate in a fish culture system is converted to nitrite, a compound extremely toxic to fish
II-2. Description of the Technology
The system developed by Prof. van Rijn reduces inorganic nitrogen from pond water by means of the induction of two microbial processes:
-Nitrification: Conversion of ammonia to nitrate.
-Denitrification: Conversion of nitrate to gas.
The system consists of an aerobic stage (trickling filter) and an anaerobic stage (sedimentation/digestion basin and fluidized bed reactor).
-Aerobic stage: The ammonia is converted by means of a nitrifying bacteria to
nitrate.Nitrification is induced in a trickling filter.
These filters are currently used for ammonia removal in water treatment plants (including fish culture systems).
-Anaerobic stage: In this stage, several biological processes take place.:
-Nitrate is reduced to N2 gas by means of denitrifying bacteria which obtain their reducing equivalents from compound released in a sedimentation/digestion tank
included in the system.
-By bacterial breakdown in the sedimentation/digestion basin and the fluidized bed reactor, organic matter is converted to CO2.
-Soluble phosphorus is immobilized into denitrifying biomass in the sedimentatio/digestion basin and in the fluidized bed reactor.
-Sulfide, formed under anaerobic conditions in the sedimentation/digestion basin, is reoxidized by autotrophic denitrifiers in the fluidized bed reactor.
Fluidized bed technology has been used to a limited extent (mainly at an experimental level) for removal of nitrate in wastewater.
Most of the fluidized bed reactors are operated with the addition of an external carbon source to drive denitrification.
The innovative aspect of the fluidized bed reactor developed by Dr. van Rijn is that organic matter accumulated in the fishpond is used as a carbon source after proper
digestionin the sedimentation/digestion tank.In addition, conditions are created in which denitrifiers store phosphorus as polyphosphate and oxidize sulfide to harmless
III. Advantages over existing technologies.
Current Re-circulating Systems
-Discharge of sludge and water rich in nutrients to the environment.
-Cannot be used for mariculture unless.
-situated in the vicinity of the sea and connected with it.
-High expenses in water and energy.
Van Rijn’s Fully Re-circulating System
-No nitrate accumulation.
-No phosphate accumulation.
-Zero-discharge to the environment nutrients to the environment.
-Can be used for mariculture far away from the sea.
-No environmental pollution
->99% saving in water expenses,Low energy expenses
IV. Current Status of the Technology
IV-1. Patent: US Patent granted 5,660,140
IV-2. The freshwater zero-discharge system at the Ginosar Experimental Station , Israel has been in operation for the last ten years. During the last eight years of operation, the unit has consistently produced annual tilapia yields of more than 100 kg of fish per 1 m3 of water volume. Average water usage (water added to compensate for evoporation losses alone) for production of 1 kg of fish were lower than 200 l.
IV-3. The experimental marine zero-discharge recirculating system in Rehovot has been operated for the last seven years. The system was primarily operated with the aim of fine-tuning the various biological treatment units. Over this period, water quality parameters were maintained at acceptable levels despite the high fish stocking densities of the seabream (Sparus aurata) and the complete closed mode of operation. Water usage was the same as in the freshwater zero discharge system.
IV-4. The experimental marine zero discharge recirculating system at the National Center for Mariculture in Eilat is in its fifth year of operation. This system, larger than the system in Rehovot, was constructed with the aim of determining the growth performance of the seabream at commercial stocking densities. Results pointed to performance parameters similar to those obtained in commercial, open culture systems.
IV-5. The commercial ornamental fish freshwater zero-discharge recirculating system ,Herev Laeet ,Israel has been in operation for the last five months and the results are as expected.
V. Commercial potential of the technology
Evaluation of the commercial potential of the technology involves the examination of the marketplace in which it will function. We can define this market as the “market
of fully re-circulating aquaculture systems”, which is an emerging market.
V-1. Current Status of Fully Re-circulating Aquaculture Systems
The main factors to take into account are:
-Most existing re-circulating systems are in the basic research stage.
-Aquaculture is facing big regulatory barriers. There are no fish culture systems in the market which can operate according to these new regulations. Commercial fully
re-circulating systems have in fact a low degree of re- circulation and a relatively high degree of water is discharged to the environment.
-Commercial re-circulating systems use water purification technologies which were developed for other purposes and have not been appropriately adapted for aquaculture.
-There are no commercial fish culture systems for mariculture on the market.
V-2. Market overall trends.
Many market trends will impact in the commercialization of the technology. Among these are the following:
- Increased Fish Demand: The demand for fish will continue to grow significantly,due to increased demand of protein with low cholesterol and the natural growth of the
The FAO estimated (2000) the value of fish traded internationally to be $51 billion/year.Over 36 million people are employed directly through fishing and aquaculture.
Consumption of food fish is increasing, having risen from 40 million tons in 1970 to 86 million tons in 1998, and is expected to reach 110 million tons by 2010.
- Capture Fisheries:They have reached their maximum production levels, so that the increase in fish demand will have to be supplied through aquaculture.
-Trends in Food Production: Countries with high populations will need to increase the protein-per-acre of food raised to feed the population.
Aquaculture in general, and fully re-circulating aquaculture systems in particular, will offer an excellent alternative in raising high-protein food in a limited area.
Fish is man’s most important single source of protein, providing approximately 16% of the animal protein consumed by the world’s population today.
- Water and Land Available: The large amounts of land and water used by current aquaculture methods will be increasingly unavailable and increasingly expensive.
It is generally accepted that a minimum rate of 49.2 liters per minute is required for each surface acre of ponds. Thus a 100-acre fish farm will need a minimum of 4,920 liters per minute of water.
Even water re-circulating systems used today require large quantities of water. If a 378,000 liter capacity re-circulating systems exchanges 10% of the water daily, it
will require 37,800 liters of water per day.
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