CENT RAS on going operation by farmers

Kg Bukit Keluang, Besut, Terengganu

Kg. Kuala Semerak, Pasir Puteh, Kelantan

Kg. Bukit, Keluang, Besut, Terengganu

Kg. Limau Nipis, Setiu, Terengganu

Kg. Air Tawar, Besut, Terengganu

Kg. Gong Medang, Besut, Terengganu

Kg Bukit Keluang, Besut, Terengganu

Kg. Mangkuk, Setiu, Terengganu

DIY own zeolite filter (Low cost - material PVC)

You can make yours simple zeolite filteration on Cents-Ras. The cost of filter system is less than RM70 per unit. The material that you need is list below ;
1. PVC pipe 2 inch - 100 cm
2. PVC pipe 1 inch - 50 cm
3. Valve 1 inch - 5 unit
4. Tee pvc 3 to 2 inch - 1 unit
5. Tee pvc 2 to 1 inch - 1 unit
6. Elbow 3 inch- 1 unit
7. Cap 2 inch - 1 unit
8. Reducer 3 to 2 inch - 1 unit
9. PVC Pipe 3 inch - 80 cm
10. Pvc pipe 3/4 inch - 100 cm
11. Elbow 3/4 inch - 4 unit

You can fabricate yours Zeolite filter based on picture above

Calculating Ammonia Loading:

The amount of ammonia excreted into a tank depends on a number of variables including the species, sizes, and densities of fish stocked and environmental conditions (temperature, pH). Ammonia loading can be roughly estimated from the biomass (weight) of fish in the tank or it can be based on the weight of feed fed each day. On the average about 25 mg (milligrams) of ammonia per day is produced for every 100 grams of fish in the tank. Therefore, in a tank containing 1,000 seabass fingerlings each weighing 75 g (75,000 g total fish weight), the daily ammonia load produced by all the fish would be 18,750 mg (18.8 g). To remedy excessively high
ammonia levels, add freshwater, eliminate feeding or reduce the density of fish in the tank.

Ammonia loading also can be estimated based on the total amount of feed fed. For manufactured fish feed with standard protein levels of 30 to 40 percent, simply multiply the total weight of the feed (in grams) times 25. For example, if the fingerling seabass are fed 454 grams of pelleted feed per day, the amount of ammonia produced per tank would be about 11,350 mg per day.

Zeolite, ammonia and fish health

Zeolites are an ideal means of managing ammonia levels in the short-term until full filter active is restored or achieved. Even modest levels of ammonia are a threat to fish health. This is particularly a problem in new ponds and aquaria where we have to let ammonia levels rise a little to encourage the establishment of nitrifying bacteria in the filter. Elevated ammonia can occasionally be a problem in established set-ups.

What are zeolites?
These are naturally occurring types of minerals, although because of their usefulness as molecular sieves they can now be artificially produced. In their natural form they are aluminosilicates, which are normal silicate minerals containing aluminium. The structure is such that these minerals can loosely bind positive charged ions, usually sodium.
They act as ion-exchangers and 'swap' their sodium ions, for other positively charged ions, for example calcium or ammonium. So they are often used for water softening to remove hardness-forming calcium ions. Fish keepers can make use of this unusual characteristic and employ them to remove ammonia (or more strictly ammonium - NH4+) from the water.

Using zeolite
The required amount is simply placed in the filter just before the water is returned to the pond or tank. Don't place it before the biological section otherwise there may not be enough ammonia left to encourage the growth of nitrifying bacteria.
Depending on the current ammonia levels, the zeolite is removed when it is 'full' and left overnight to soak in a very strong salt solution, during which the collected ammonium is "swapped" for sodium (you will recall that salt is actually sodium chloride). After a good rinse in clean water it is ready for use again

How much and how often?
For aquaria use, zeolite and other ion-exchanger products usually come in pre-prepared pouches with instructions. For pond use it is best to have at least two 10 kg sacks - one in use, the other being recharged.

Initially it will probably need to be changed daily, until such times that ammonia test kit readings show that levels are stabilising. Once this happens the period between cleans can be extended

To clean it use 2-3 oz salt per gallon of water. The actual amount is not critical as long as it is good and salty. It should only be used to manage an existing problem and not used on a long-term 'just in case' basis. First, if used permanently there is always the risk that it will 'dump' its ammonium collection. Secondly, it also acts as a water-softener and will remove calcium from the water.

Initially, even with zeolite it may still be necessary to do partial water changes to keep ammonia at an acceptable level. Zeolite cannot be used in ponds or aquaria where the water is salted

How Biological Filtration can works????

A biological filter is quite simply the heart of the RAS system. It's purpose is to convert the waste matter produced by the fish from harmful ammonia into less toxic waste. It is less important to remove solids particles from water than it is to process nitrogen, so if there is to be a compromise between mechanical and biological, err on the side of biological.

In other words, it is much better to allow particles below a certain size to escape back into the pond,while converting a great deal of ammonia to nitrate, than it is to catch every little thing down to a micron or less which in the process would slow the water down to the point where the bacteria have a hard time living (because they're not getting enough oxygen).

The bacteria that convert ammonia to nitrate for us are among a class of bacteria that you may have heard of before. They are the so-called, “nitrogen fixing” bacteria. This means that they take nitrogen that is unavailable to plants in its ammoniacal form, and make it available to plants in an oxidized form.

There are 2 types of bacterial species that colonise the biological filter media. Nitrosomonas sp.bacteria which oxidize ammonia to nitrite, and Nitrobacter bacteria convert nitrite to nitrate.

NH3 + CO2 + 1.5 O2 + Nitrosomonas → NO2- + H2O + H+NO2- + CO2 + 0.5 O2 + Nitrobacter → NO3-

The conversion of ammonia to nitrates is performed primarily by bacteria and other nitrifying bacteria. The primary stage of nitrification, the oxidation of ammonia (NH3) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites (NO2-). Other bacterial species, such as the Nitrobacter, are responsible for the oxidation of the nitrites into nitrates (NO3-).It is important for the nitrites to be converted to nitrates because accumulated nitrites are toxic to plant life

Denitrification

Denitrification is the reduction of nitrites back into the largely inert nitrogen gas (N2), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas and Clostridium in anaerobic conditions. They use the nitrate as an electron acceptor in the place of oxygen during respiration. These facultatively anaerobic bacteria can also live in aerobic conditions.

Ammonia

Ammonia (NH3) is produced by fish as part of their normal metabolic function and is excreted from the gills. The amount of ammonia produced is directly related to the amount of food they eat. Approximately 3-4% of normal 30-40% protein level food will be excreted as ammonia, i.e. for every 100grams of food 3-4grams (3000-4000mg) of ammonia is produced. Fish exposed to unacceptable levels of ammonia risk damage to gills, eyes, fins and skin which can result in them being susceptible to secondary bacterial infection. Using standard drop type tests kits any ammonia reading is considered unacceptable and remedial action should be taken.NitriteAmmonia is oxidized by the Nitrosomonas sp. bacteria in the filter to produce nitrite (NO2). Whilst it is not considered as dangerous as ammonia it can still do serious damage to your fish. High levels of nitrite are likely to stress your fish leaving them susceptible to secondary infection. As with ammonia, target levelsshould be that nitrite is undetectable. Before the fish pond filter can efficiently remove ammonia and nitrite from the fish pond water, it must first become fully colonized with nitrifying bacteria. This can take some time and is a process known as fish pond filter "maturation". Each time a fish is put in the fish pond it will add to the total amount of ammonia being produced. The ammonia level in the fish pond will therefore increase slightly. Because there is more ammonia for the bacteria to utilize, they start to multiply until there are enough to use all of theammonia being produced inside the fish pond. The ammonia level in your fish pond will then fall back to zero.NitrateAs the ammonia level falls, the amount of nitrite produced by the bacteria in the fish pond filter will start to increase. Therefore, the level of nitrite in the fish pond will rise. The increasing nitrite level means that the bacteria that break it down can start to multiply in the fish pond filter until, as with the ammonia, there are enough to use up all the nitrite that is being produced. The nitrite level within the fish pond can then fall to zero. As this occurs, the nitrate level increases.

Conversion of nitrite to nitrate (NO3) is the final stage of the nitrification process.

There is debate as to the possible problems that elevated levels of nitrate may cause.Nitrate and it causes no problem at all. High nitrate may also attribute to green water(phytoplankton). The green water problem can get worst when you clean the biofilter and make water change outs, due to the reduction in bacteria.The bacteria also produces a certain phytoplankton-killing enzyme. As algae starts to grow in the biofilter,or on the walls of the pond, the bacteria loves to feed on this algae, and as it does so it releases the enzyme into the water. Green water is a pain for many reasons. Ultra Violet Clarifier lights will kill single cell phytoplankton algaethat cause green water, and when dead they clump together and can be removed by the filter. However there is sometimes a concern expressed that passing water through the UVC also kills beneficial bacteria.

Cost efficient RAS technology for nursery (Article in Aquaculture Asia Pasific Magazine- March/April 2009 Vol. 5 Number 2)

The team led by Ahmad Daud Om at the Marine Fish Production and Research Centre has developed a low cost and easy to manage recirculation aquaculture system suitable for small hatcheries. They have named this CENTS – Cheap Efficient Nursery Tank System. The system is ideal for nursing the highly carnivorous tiger grouper from 2-3cm to 7.5 - 10 cm total length in seawater of 15ppt. There are two partitioned concrete biological filters, two water pumps, one air blower and 20 concrete tanks holding 180 litres of water. Each of these can hold 2,000 2-3 cm juveniles. The investment cost is MYR 20,000. A unique feature is a waste trap which reduces the load on the biological filters. This is merely lifted for cleaning twice a day. Waterin the tanks and biological filters are topped up by 10-15% daily. Fish is graded every two weeks and stocking density is reduced by transferring fish to nursery tanks. In a one month operation, the yield is 14,000 juveniles. Fish are fed to satiation 4-6 times daily. Pre operation procedures include preparation of probiotic bacteria for tanks and biological filters. The benefits of this system include improvement in survival at 80-90% as compared to juveniles reared in open systems such as cages and ponds. The system has been commercialised and it now used by 20 farmers for nursing of various species of marine fish fry.

Zeolite can remove ammonia in RAS

What is magnificient of Zeolites?????

Zeolites are crystalline aluminosilicate minerals that can be found in rock deposits throughout the world. They are formed by a process known as devitrification or crystallization of volcanic ash, a process that takes place over millions of years when lava remains in contact with fresh or salt water. The word 'zeolite' itself is an amalgam of the two Greek words for 'boiling stones' because of the steam that is given off when these rock crystals are heated, due to their high water content. Zeolites have a molecular stacked-cage or honeycomb structure formed of silicon and aluminium oxides, and as a result of the electronic configurations of the aluminium, silicon and oxygen that make up these tiny zeolite cages, each has an overall negative charge which means that they electrostatically attract positively charged ions and other particles, in much the same way that a magnet attracts iron filings.

Molecule structure of zeolite

Oxygen and ammonia are the two most important parameters in aquaculture operations. While oxygen can be easily controlled ammonia on the other hand is much more difficult to mitigate and is highly detrimental to the health of fish. The natural generation of toxic levels of ammonia (NH3) and hydrogen sulphide (H2S) by large densities of fish in aquaculture operations affects fish tissue, growth rates, oxygen utilization, disease resistance and causes mass mortality.

Zeolite is currently used in commercial fish farms to reduce ammonium (NH4) and hydrogen sulphide levels resulting in increased growth rates and population densities. Zeolite is also used during fish transportation allowing the delivery of more fish over a longer period of time.Zeolite has a high selectivity and capacity for ammonium via cation exchange capacity (CEC). Once the ammonium ion is within the zeolite lattice, it is not water-soluble.

When used as an ion-exchange filter medium the zeolite can reduce ammonium content of circulating freshwater from aquaculture systems by as much as 97%. Piper and Smith (1982) suggested that a water recycling system with a zeolite filter system can allow up to a 10 fold increase in fish density. Zeolite also reduces ammonium content in discharge waters in order to meet environmental requirements.Zeolite is 100% natural, durable and can also be simply regenerated using a brine solution (with a rinse) for repeat cycles of this ion exchange filter bed. Zeolite can also be broadcast over the surface of a pond to be effective in reducing ammonium.

The pond-bed sludge can be recovered and used as a nutrient enriched slow release fertilizer.
The required zeolite quantity for your operation depends on water pH, temperature, volume along with fish species and population density. When the optimum quantity of zeolite is used, the ammonium level is reduced at a rate highly dependent upon the rate of water movement. A variety of systems have been designed for reduction of ammonia in fish rearing environments.

Zeolite also provides a substrate for bacterial populations in order to breakdown ammonium to nitrate (NH4 to NO3) and remains effective as a chemical filter capable of modifying fluctuations in the system's ammonium levels. This enhances the biological functions making ammonium available to bacteria at a stable level, thus enabling the bacteria to remain abundant during periods of low ammonium contamination. The bacterial population will therefore survive during dramatic changes in concentration.There are three filtration processes to reduce ammonia in the water:

Mechanical filtration of unused food and fecal material.

Zeolite is much more effective than sand and charcoal filters due to nominal rating of 3 to 5 microns (sand is typically 20 microns) thereby increasing loading while reducing the amount of backwashing. Refer to the ‘Water Filtration’ menu item in the Industrial Section.

Biological.

The tremendous surface area and irregular surface of BRZ Zeolite provides an idea media for aerobic bacteria. The bacteria mineralize the organic nitrogen compounds. The process can be aerobic (nitrification) or anaerobic (denitrification). Nitrification is most common and involves the oxidation of ammonia to nitrite to nitrate by autotrophic bacteria.

Chemical.

Due to its large cation exchange capacity zeolite is an excellent filter of ammonium and certain heavy metals.

How the CENTS-RAS is working???

A system where the water (in fish rearing tank) , instead of being discharged to the outside environment, is reused after undergoing filtration in a settling pond or water treatment process.

Biofiltration.

As we mentioned earlier, the biological filter (biofilter) is the heart of the RAS. As the name implies, it is a living filter composed of a media (corrugated plastic sheets or beads or sand grains) upon which a film of bacteria grows. The bacteria provide the waste treatment by removing pollutants.

The two primary water pollutants that need to be removed are

(1) fish waste (toxic ammonia compounds) excreted into the water and

(2) Uneaten fish feed particles. The biofilter is the site where beneficial bacteria remove (detoxify) fish excretory products, primarily ammonia.Ammonia and Nitrate Toxicity:Ammonia and nitrite are toxic to fish.

Ammonia in water occurs in two forms: ionized ammonium (NH4+) and unionized (free) ammonia (NH3). The latter, NH3, is highly toxic to fish in small concentrations and should be kept at levels below 0.05 mg/l. The total amount of NH3 and NH4 remain in proportion to one another for a given temperature and pH, and a decrease in one form will be compensated by conversion of the other. The amount of unionized ammonia in the water is directly proportional to the temperature and pH. As the temperature of pH increases, the amount of NH3 relative to NH4 also increases.In addition to ammonia, nitrite (NO2) poisoning of fish also is an imminent danger in RAS. Nitrite levels should be kept below 0.5 mg/l. Brown blood disease (methemoglobinemia) occurs in cultured salmon and channel catfish when hemoglobin is oxidized by nitrite to form methemoglobin (a respiratory pigment of the blood that cannot transport oxygen). The disease can occur at nitrite concentrations of 0.5 mg/l or greater. As the name implies, the blood has a characteristic chocolate brown color. Adding salt (NaCl) at a rate of 1 pound per 120 gallons of water (a chloride to nitrite ratio of 16:1) will suppress this disease in soft water; a ratio of 3:1 is effective in hard water.

CENTS IN BRIEF

CENTS Flowthrough (2006)

One set of CENTS-RAS are shown above (2008)

A commercial CENTS-Flowthrough run by famers at
Kg. Kuala Semerak, Kelantan


New Version of CENT RAS- HDPE (2008)

At beginning, CENTS is consist of cement culvert, pumped sea water 24 hours. Than, in 2008 we start to developed RAS concept which is recirculate or to reused back seawater after treat with a special and economic biofilter. So, the CENTS RAS should consist of effective biofilter. The points here is, biofilter is the heart of RAS system. Failed the biofilter system will collaspe all the cultured or nursed fry. At that reasons, we are more focus on how we could developed a economic filteration system.

After some innovation we introduced to the system, we realize that, to made filteration is more effective, all the uneaten feed and feces should descriminate out before water treat in the biological filteration. than we come out with simple device, what we call it, ..... Cents Waste Trap.

Cents Waste Trap

CONCEPT RAS

The aquaculture industry that began developing in the late 1960s has exploded into a major global industry of 60 million tonsa year, with huge annual revenues in excess of US$ 70 billion (FAO,2006). With the current increase in environmental awareness andthe consequent stringency in environmental legislation, a newapproach to dealing with the ecological problems associated withaquaculture has been developed—recirculating aquaculture systems. This approach was originally developed to provide a solutionto the environmental problems generated by the traditional pondand flow-through aquaculture systems, since it enables thetreatment of polluted water within a closed loop, offers improvedcontrol of effluent discharge, and allows complete environmentalcontrol (van Gorder, 1994; Shnel et al., 2002). Moreover, RASconfers ecological and economic advantages in that it facilitates areduction in the amounts of water and energy required andreduces land use. In addition, it provides growers with thegeographical freedom to set up aquaculture systems in ‘‘nontraditional’’farming areas (Shnel et al., 2002); for example, small RAS,such as the one presented in this study, producing lucrativeseafood species might be suitable for small-scale aquaculture forfood production in urban areas (Zohar et al., 2005). Thus, RAS couldcontribute to meeting the demand for protein foods in highlypopulated urban centers.

What is CENTS?

CENTS = Which is mean of Cheap Efisyen Nursery Tank System are initiated by MFPRC (Marine Production and Research Center) in the year 2006. At the beginning CENTS are developed by flowthrough system which is pump with running 24 hr non stop.

This system was introduced for intention to developed more efisyen nursing system than conventional system which is used earthen pond. The prototype CENTS is consists of cement culvert with 0.75 cm diameter and 180 liter volume capacity and pumping sea water. However, after innovative ideas, this systems are change to the RAS system, which is more economic and suitable and practical to operate at many location which is difficult to manage a conventional technique.