Evaluation on Biofilter in Recirculating Integrated Multi-Trophic Aquaculture

Integrated multi-trophic aquaculture pays more attention as a bio-integrated food production system that serves as a model of sustainable aquaculture, minimizes waste discharge, increases diversity and yields multiple products. The objectives of this research were to analyze the efficiency of total ammonia nitrogen biofiltration and its effect on carrying capacity of fish rearing units. Pilot-scale bioreactor was designed with eight run-raceways (two meters of each) that assembled in series. Race 1-3 were used to stock silky worm (Tubifex sp) as detrivorous converter, then race 4-8 were used to plant three species of leaf-vegetable as photoautotrophic converters, i.e; spinach (Ipomoea reptana), green mustard (Brassica juncea) and basil (Ocimum basilicum). The three plants were placed in randomized block design based on water flow direction. Mass balance of nutrient analysis, was applied to figure out the efficiency of bio-filtration and its effect on carrying capacity of rearing units. The result of the experiment showed that 86.5 % of total ammonia nitrogen removal was achieved in 32 days of culturing period. This efficiency able to support the carrying capacity of the fish tank up to 25.95 kg/lpm with maximum density was 62.69 kg/m3 of fish biomass productionDoi: http://dx.doi.org/10.12777/ijse.4.2.2013.80-85 [How to cite this article: Sumoharjo, S. and Maidie, A. (2013). Evaluation on Biofilter in Recirculating Integrated Multi-Trophic Aquaculture. International Journal of Science and Engineering, 4(2),80-85. Doi: http://dx.doi.org/10.12777/ijse.4.2.2013.80-85]


I. INTRODUCTION
FAO (2010) claims that aquaculture accounted for 46 percent of total food fish supply, a slightly lower proportion than reported in The State of World Fisheries and Aquaculture 2008. On the other hand, aquaculture is required to grow in response to demand for increased cheaper protein resources. However, in practices, aquaculture faces major problems in feed nutrient retention, where only 25-30% of feed nutrients converted for energy and growth (Avnimelech, 1999;Rakocy, et al., 2006;Losordo, et al,. 2007), the rest is excreted in water column that would otherwise build up to toxic levels and finally decreasing carrying capacity in the ¤sh rearing units. Actually, Fish can be grown at very high density in aerated-mixed ponds. However, with the increased biomass, water quality becomes the limiting factor, due to the accumulation of toxic metabolites, the most notorious of which are ammonia and nitrite (Avnimelech, 2006). It is estimated that 85% of phosphorus, 80-88% of carbon, 52-95 % of nitrogen (Wu, 1995) and 60% of mass feed input in aquaculture will end up as particulate matter, dissolved chemicals, or gases (Masser, et al., 1999). That why in conventional aquaculture often replace 5-10 % of water every day. Moreover, in recent years, environmental regulation and land limitation become the most consideration in aquaculture development.
Integrated multi-trophic aquaculture (IMTA) is a new concept of aquaculture that different to polyculture terminology. With the multi-trophic approach, aquaculture of fed organisms (fin-fish or shrimp) is combined with the culture of organisms that extract either dissolved inorganic nutrients (seaweeds) or particulate organic matter (shellfish) and, hence, the biological and chemical processes at work are balancing each other (Chopin, 2006). This concept seems to become a future of aquaculture systems and operations. FAO (2012) states that one-third of the world's farmed food fish harvested in 2010 was achieved without the use of feed, through the production of bivalves and filter-feeding carps.
IMTA usually operated in open water-based aquaculture, such as mariculture or cages in lakes or reservoirs. While land-based aquaculture, water and land use are rapidly becoming a strong factor driving the adoption of recirculating technologies. A fish farm c full advantage of IMTA once the nutrient discharge fed (fish) component is fully balanced by the harves xtractive components (seaweeds and suspensio deposit-feeders) (Troell et al., 2009). Therefo biological filter components play an important role systems. Its efficiency in removing nutrient was fish tanks is the main goal to design the biofilter sys Because of relatively high cost, built recirc aquaculture systems should be designed such th efficient, cost-effective and simple to operate research was an effort to develop biofiltration subs and to analyze its efficiency in removing nutrien and increasing carrying capacity to a pilot s integrated multi-trophic reciculating aquaculture sy

IMTA System Description
A pilot scale of IMTA was set up for raising two of fish in different trophic level, i.e.; climbing (Anabas testudineus Blk) and nile tilapia (Oreoc niloticus). Fish tank construction made from wood with fiberglass. The biofilter system was placed in with the fish tanks. The biofilter systems consisted run-raceways (2 meters in length and 13 cm in w each) with effective volume was 140 liters. Where; 1= climbing perch's tank as carnivoro nile tilapia's tank as herbivorous; 3. Silky raceways; and 4 = plant's raceways as photoautotr for growing a eus) weighing g tank was being stocked 6,58 kg/m 3 of nile tilapia (Oreochr weighing 29,3±12,46 grams. Floating p 32 % protein were used to feed the fish Fish was weighed at the end of experim The number and weight of fish taken out culture tanks was recorded for calculati parameter. Fish dead during experime with the same size to keep the constant n the tanks. Death time and fish size were re out the survival rate parameter.
Water flow maintained at 5 liter throughout the experiment units includin (effluent) discharged from fish tank to worm (Tubifex sp) that stocked at the b out 3 individual/cm 2 in three raceways While spinach (Ipomoea reptana), green m juncea) and basil (Ocimum ba hydroponically planted 40 plants of each Planting lay out were conducted in comple block design regarding to flow direction technique where the plants floated by poly

Calculations
Calculation steps to determine biofilter Total Ammonia Nitrogen (TAN) produ based on nitrogen mass balances using produced per kg of feed (Timmons, et al., Where: PTAN = total ammonia productio F is feed rate (kg/day); PC is the protein (decimal value). 0,09 constant in amm equations assumes that protein is 16% nitrogen is assimilated by the organism, nitrogen is excreted, and 90% of nitro TAN+10% as urea.
Then, TAN loading rate calculation bas (1977), ammonia accumulation factor (C) recirculation determined by following equ Where: Climit.TAN is allowable ammoni CTAN is single pass ammonia con determined with, CTAN = PTAN (gm/d)/wa (m 3 /hari), and TAN loading rate determin iameter 81 Oreochromis niloticus) loating pellets containing the fish at satiation rate. f experiment (at 32 days) taken out from each of the r calculating fish growth experiment was replaced constant number of fish in ze were recorded to figure t 5 liters per minutes ts including nutrient waste tank to bioreactor. Silky at the bioreactor spread raceways (raceway 1-4). ), green mustard (Brassica basiliucum) were of each at raceway 4-8. in completely randomized direction and used rafting ted by polystyrene sheets.
week at five points based t of bioreactor or the 1 st ia's tank), (2) inlet of y, (3) outlet of bioreactor, udineus) tank, and (5)  Carrying capacity (loading density) and fish density.
According to TAN biofiltration efficiency, hy recirculation rates (R), feeding rates, and tanks The maximum carrying capacity of the fish tanks water exchanges determined by Westers (1997) eq Where LD is fish loading density (kg/lpm), TAN biofiltration efficiency, Vtank is fish tanks (liter), ANO3 is allowable nitrate nitrogen, FR is rate (%/BW/d), PTAN is TAN production (g/d); 4,2 c is come from 1 molecule of TAN generate 4,2 mole NO3; R is recirculation rates (hour) Therefore, maximum fish density can be ex with this equation.

Fish performance and TAN Production
During the 32 days of grow out period, c perch feed consumption is very small compared to which 0,5 kg of feed while tilapia can spend 1.96 feed.
For the total growth during the 32 days of gr period, the average climbing perch and tilapia has the size of 46.0±8,47 gm and 42,4±27,73 gm, respe Based on unpaired t test assuming not the same v the growth of these two species were signi different (P <0.05). According to total feeding ra production rate was 72,5 gm TAN/kg feed. It mea 2,94 % of TAN produced per kg feed, this value w significant different with the standard of the esti TAN production that published by Malone TAN tends to decrease during experimen rising at day-16 while nitrate also in experiment. In 32 days experiment, nitr seemed to follow the first order rea sufficiently low substrate concentration, become linear (Chen et al., 2006). Ho experiment showed that nitrite oxidation appears did not have linear corr accumulation occurred in day-20 and production become slower. The accumu suggested that ammonium and nitrite ox proceed at the same rates in the batch exp et al., 2009).
Oxidation of ammonia is usually the r in the conversion of ammonia to nitrate (C Thus value of ammonia oxidation are th parameters in describing nitrification ( 1994).

A. Effects of Biofiltration efficiency to car
The production capacity of fish that can the IMTA system is analyzed through a com major limiting factors i.e., dissolved ox ammonia nitrogen. Model calculations the controlling factors such as feeding rate o amount of water circulation, and the e biofilters. Based on the concentration of d systems can accommodate a maximum kg/m 3 of climbing perch, while the tilapia supporting up to a maximum density of results of these calculations based on th oxygen fish need oxygen concentration a remaining oxygen is not used for respir fish the greater oxygen needed to supply (Colt, 1991;Wester, 1997).
The difference in capacity between perch) and trophic II (nile tilapia) is stron the IMTA system configuration, in which tilapia are in a position after filtration an tank, it makes the climbing perch get a containing higher oxygen, whereas theirs themselves lower. The types of labyr additional respiratory system) such as cli experiment, nitrite started te also increased during ent, nitrification process order reaction, when at entration, the relationship 2006). However, at the oxidation rate to nitrate ear correlation, nitrite 20 and made nitrate e accumulation of nitrite nitrite oxidations did not batch experiments (Sesuk ally the rate limiting step nitrate (Chen et al., 2006). tion are the rate limiting ification (Wheaton et al., -N, NO3-N and PO4-P to carrying capacity sh that can be produced by gh a combination of two solved oxygen and total lations then consider other ing rate of water flow, the and the efficiency of the ration of dissolved oxygen, aximum density of 25.8 the tilapia is still capable of ensity of 47.7 kg/m 3 . The ed on the value of the ntration available and the for respiration. The more to supply the needs of fish etween trophic I (climbing a) is strongly influenced by , in which the layout like ltration and before tilapia rch get a supply of water eas theirs oxygen demand of labyrinth fish (with uch as climbing perch are not sensitive to the concentration of oxygen in water (Zonnenfeld, 1991).
In IMTA system, water was recirculated continuously, where water with higher oxygen concentration from climbing perch's tank flows into the tilapia's tank thus providing a greater influence on the capacity of tilapia production. However, in the three-week maintenance period, the fish still need oxygen to be supplied from the flow of water out of the tank with flow rates 5 liters /min, but then the concentration of oxygen is already close to zero, and tilapia loss of appetite. To overcome this added bubble jet aeration system, but it also only lasted for two weeks. Thus, changes made to the aeration system keeps the water fountain with a height of 1 meter, the system is able to maintain the DO concentration in the tank of tilapia with an average of 1.3 mg/l.
Modeling fish densities can be done if the oxygen demand is not a problem in the system. Brune, et al. (2003) states that if the concentration of oxygen is sufficient for the needs of the fish and the stripping of CO2 through aeration, the NH3 will be a limiting factor within 24 hours. Therefore, the density of the fish will be strongly influenced by the nitrogen removal efficiency in the system. Based on the average values of temperature and pH, the fraction of unionized ammonia (NH3) is only 1.91% on average in the tank of climbing perch and 1.76% at the tilapia tank. Biofiltration efficiency of TAN was 86.5% overall. Model density of fish made on the basis of the efficiency of biofiltration of ammonia and dissolved oxygen demand estimated of 62.69 kg/m 3 fish biomass. However, the water quality parameters will begin to limit the carrying capacity allowed for waste degradation, accumulation of ammonia, carbon dioxide, and suspended solids (Timmons and Ebeling, 2007).
Carrying capacity calculation procedure was based on the calculations made by Losordo and Hobbs (2007) as shown in the following worksheet.
Flow calculations represent the factor analysis procedure with ammonia production as a limiting factor to the efficiency of biofilters as independent variables (Wheaton, 1977;Wester, 1997;Drenan II, 2006;Ebeling, 2006;Timmons and Ebeling, 2007). Production of ammonia was generated by the calculation of Drenan II (2006) at 3.06 g/day was not much different when using the equation of Ebeling (2006), which was equal to 3.28 g/day.
Through the process of biofiltration with trophic level detrivorous (Tubifex sp) and phototrophic (spinach, mustard greens, and basil) on a scale integrated aquaculture systems multi-trophic pilot was able to absorb the ammonia waste by 86.5% of TAN. This value is higher than ever published by Graber and Junge (2009) that 69 % of nitrogen removal by the overall system could thus be converted into edible fruit in hydroponic system design only. Therefore, based on the calculation of production capacity due to TAN removal efficiency, a culture system like this can result in fish biomass of 62.69 kg/m3. However, according to Timmons and Ebeling (2007) stated that do not get stuck on the calculation of the mathematical models because you can kill fish, so to be safe, it is recommend stocking half of the results of these calculations (only 31.34 kg/m 3 of fish biomass is recommended).

IV. CONCLUSIONS
A pilot-scale of integrated multi-trophic aquaculture production systems set up in this study generally works well for a single production cycle (32 days). Although there is no water exchanges, but the subsystem designed biofilter still able to maintain optimum water conditions for the survival and growth of fish. Maximum production capacity of fish that can be produced from an integrated multiple trophic with a total volume of 2.2 m 3 of water was 25.30 kg of climbing perch and 39.58 kg of tilapia; 772.1 grams of spinach, 333.6 grams of basil, and 217, 6 grams of mustard for 28 days, and 789,533 individual of silky worm (Tubifex sp) for 32 days. and high economic value, as well as a uniform seed size. Although aiming for sustainability of local fish, but given the low growth rate, then the selection of climbing perch (Anabas testudineus) in aquaculture systems may be less favorable. For the types of plants that are used to absorb nitrogen waste, spinach (Ipomoea reptana) and basil are recommended to be used, although the price is relatively low, but the rate of growth (harvest every 14 days) and the high absorption rate of nutrients added value in terms of economic benefits and health.