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Use of Clinoptilolite Zeolites for Ammonia-N Transfer and Retention
in Integrated Aquaculture Systems and for Improving Pond Water Quality
Appropriate Technology Research 5 (10ATR5)/Experiment/Thailand
Asian Institute of Technology, Thailand
Michigan State University
Ted R. Batterson
Donald L. Garling
Christopher F. Knud-Hansen
The ultimate goal of this proposed research is to adapt existing technologies using natural clinoptilolite zeolites to provide a more socially acceptable and efficient way to integrate animal manures in pond fertilization, conserve and recycle on-farm resources, and lessen environmental impacts.
Fertilization Efficiency Objectives
2) Determine the rate of release of ammonia from ammonia-enriched clinoptilolite when used as a nitrogen fertilizer for stimulating natural food production in an outdoor aquaculture system.
3) Determine the ability of clinoptilolite to moderate ammonia concentrations in a fertilized outdoor culture system.
Pond Water Discharge Objectives
2) Evaluate the potential utility of nutrients reclaimed by clinoptilolite for recycling in pond fertilization.
Natural zeolites are aluminosilicate minerals found in volcanogenic sedimentary rocks worldwide (Mumpton, 1999). Natural zeolites possess several important properties including adsorption, cation-exchange, dehydration-rehydration, and catalysis. Considerable scientific research in the last few decades has identified broad applications for natural zeolites in construction materials, soil improvements for water and nutrient retention, treatment of water and wastewater for removal of heavy metals and nutrients, dietary supplements for farm-raised animals, health care, and other beneficial uses (Mumpton, 1999).
Clinoptilolite zeolites, (Na3K3)(Al6Si 30O72)24H2O, are one of the 40+ types of naturally existing zeolites. Clinoptilolites possess a cation-exchange capability of about 2.25 meq g-1, and are able to exchange ammonium-N with sodium (Na) and potassium (K) (Mumpton, 1999). One gram of clinoptilolite can take in about 2.2 mg ammonium-N. This cation-exchange capability has been utilized effectively for terrestrial agriculture, where clinoptilolites are first saturated with ammonium-N and then incorporated into crop soils. In this way they act as a slow-release fertilizer, with plants able to extract the sequestered ammonia from the clinoptilolite (Barbarick and Pirela, 1984; Lewis et al., 1984; Dwairi, 1998). Not only does clinoptilolite improve nitrogen fertilization efficiencies, it also reduces nitrate leaching by inhibiting the nitrification of ammonium to nitrate (Perrin et al., 1998). Most of the manure-ammonia sequestered in the zeolite is unavailable to nitrifying bacteria because of the small (4-5 angstrom) pore size of the crystal lattice structure (Mumpton, 1999). Furthermore, clinoptilolites are also used for animal waste management. Clinoptilolites are replacing clays in the cat litter market, and are being used to create an odorless, nitrogen-rich compost from farm livestock manures.
The use of clinoptilolites in aquaculture has focused on ammonia removal for the aquarium industry and freshwater culture systems (Bower and Turner, 1982; Dryden and Weatherley, 1987). The research below, however, proposes an analogous use of clinoptilolite for aquaculture as currently used for terrestrial agriculture and animal waste management: i.e., as a vehicle for ammonia absorption and subsequent fertilization to stimulate algal productivity.
Applying clinoptilolite technologies for livestock-fish integrated systems should improve sustainability by increasing nutrient utilization efficiencies while reducing undesirable farm outputs. Most of the nitrogen entering a farm as animal feeds ends up as ammonia in manure, which is either volatilized creating noxious odors or leached out as nitrate. By capturing this ammonia-N before it gets either volatilized or nitrified, and using that nitrogen to promote algal productivity in ponds, the farmer not only improves the farm environment by reducing noxious odors and nitrate leaching, but recycles an otherwise lost nutrient for increased farm productivity. Incorporating clinoptilolite with fresh animal manures may also improve the social acceptability of integrated aquaculture.
Furthermore, by transferring ammonia from animal manures to clinoptilolite, and then applying the ammonia-enriched clinoptilolite to ponds, the farmer can fertilize ponds with manure-N without adding additional BOD (biochemical oxygen demand). The major environmental risk of adding manure to ponds is the creation of anoxic conditions in the water. Research clearly shows that both algal and fish productivity can be quite high in ponds without the risk of pond water deoxygenation if no additional organic matter is added (Knud-Hansen et al., 1993). Using clinoptilolite to transfer manure ammonia turns animal manure into a source of inorganic nitrogen, and should eliminate associated risks of adding manures to ponds.
Clinoptilolites are also increasingly being used for wastewater treatment (Holman and Hopping, 1980; Ciambelli et al., 1985). For example, 18 municipal wastewater treatment facilities in Brisbane and other cities in Australia use zeolites for ammonia removal and for the flocculation, settling, and removal of phosphates in domestic wastewater (Oláh et al., 1989; Charuckyj, 1997). The research proposed below is a simple application of this existing clinoptilolite technology for cleaning pond water before being discharged into streams and canals. By removing soluble nitrogen and phosphorus before discharge, receiving waters are at less risk of eutrophication. By capturing these nutrients, they can be recycled back into ponds for stimulating algal productivity. Nutrients which would otherwise be lost from the farming system and degrade surrounding environments are instead recycled to increase farm productivity. Furthermore, clinoptilolites are renewable, since regeneration can be simply accomplished through heating or immersion in a salt solution. And since clinoptilolites are natural, inert, do not degrade, and even used in animal feeds (Pond and Yen 1984), they have no associated environmental risks.
Quantified Anticipated Benefits
Anticipated benefits are discussed generally above in the "Significance" section. More specifically, anticipated benefits to the farmer will be:
And to the community:
All research will take place at the Asian Institute of Technology (AIT), Thailand, within their Agriculture, Aquatic Systems and Engineering Program. Mr. Yuan Derun, a doctoral student within the graduate program, will be responsible for conducting the research under the direction of Dr. Knud-Hansen. The clinoptilolite to be used in all studies originates from Potosí, Mexico, and has an exchangeable K:Na ratio of about 8:1. Statistical analyses will include Analysis of Variance (ANOVA) for comparison of treatment means, and correlation and regression analyses for identifying relationships. The economic viabilities of the proposed clinoptilolite technologies for rural farming systems will also be evaluated as part of the overall research analysis.
Standard cost-benefit analysis at the farm level: costs include materials, time, labor, alternative sources of pond nutrients (i.e., fertilizers and manures), etc.; benefits include savings on fertilizer costs by recycling nutrients otherwise lost to the farming system, perhaps increased marketability of fish not raised directly on animal manures, etc. Economic analysis will focus on the potential for zeolite technology as applied for rural integrated farms in Thailand. Exact details will develop as the technology evolves through the proposed research.
1.Relationship between Clinoptilolite and Ammonia-N Absorption from Animal Manures
This relationship will be examined through a bench study. Crushed clinoptilolite (about 1-2 mm diameter grain size) will be contained in plastic mesh bags at approximately 1 kg clinoptilolite per bag, and immersed in buckets containing fresh swine and chicken manure. Water will be added as necessary to make the manure solution more liquid, which will facilitate the cation-exchange process between K and ammonium. The primary variable examined will be the length of time required to saturate the clinoptilolite with ammonium ions. Additional variables will be the effect of agitating the clinoptilolite bags on the speed of ammonia absorption, and calculating weight to weight relationships between the amount of clinoptilolite required versus the quantity and types of manure. Analytical measurements will be total Kjeldahl nitrogen of the manures before and after exposure to clinoptilolite, and ammonia-N retained in the clinoptilolite, which can be extracted through persulfate digestion.
2.Release of Ammonia from Ammonia-Enriched Clinoptilolite in a Fertilized Pond
The release of ammonia from clinoptilolite enriched with manure-ammonia will be examined both in a bench study and in an outdoor tank experiment. The bench study will be a preliminary evaluation of the ability of a mixed algal culture to extract ammonia from ammonia-enriched clinoptilolite, and examine the relationships between per cent ammonia saturation of clinoptilolite and algal biomass/productivity. The mixed algal culture will come from a fertilized pond and placed in 20-L buckets. Triple superphosphate (TSP) will be added to make algal productivity in the cultures N-limited. Clinoptilolite with a full range of percent ammonia saturation will be added to the containers. There will be a total of 10 different saturation levels in triplicate containers, with algae cultured outdoors for one week. Algal biomass will be determined daily from chlorophyll a measurements made with a hand-held fluorometer. Algal productivity will be determined by differences in dissolved oxygen measured by a hand-held dissolved oxygen meter measured at pre-dawn and mid-day. Ammonia-N will be measured in the clinoptilolite before and after the culture period, and in each container daily at mid-day.
Based on the results from the two bench studies described above, an 8-week grow-out experiment will be conducted in 2.5 m x 2.5 m x 1 m outdoor concrete tanks located at AIT. Nile tilapia fingerlings, about 10 g fish-1, will be stocked at 3 fish m-2. There will be a total of 13 treatments, with three replicate tanks (experimental units) per treatment assigned randomly in a completely randomized design. Nine of the treatments will examine the transfer of ammonia-N from zeolite into tank water. There will be three different amounts of clinoptilolite enriched with ammonia from three different sources: swine manure, chicken manure, and concentrated solution of urea. The ammonia-enriched zeolite will be in plastic mesh bags (about 1 kg zeolite/bag), with the three different numbers of bags per treatment. With all of the above nine treatments, bags will be replaced weekly. The actual number and size of bags will be determined based on results from the preliminary bench studies described above.
TSP will be added to all tanks at about 1.0 g TSP-P m-2 wk-1 to provide enough soluble P to prevent P-limitation of algal productivity. The last four treatments will be a dose-response evaluation of clinoptilolite's ability to moderate ammonia concentrations in culture water. One treatment will have no bags of clinoptilolite, while the other three will have increasing numbers of bags. All four treatments will be fertilized with urea at 3.0 g urea-N m-2 wk-1 and 1.0 g TSP-P m-2 wk-1. These fertilization rates correspond to rates established by previous MSU/AIT research found to be very productive without excessive fertilization. The treatment without any bags will serve as the control for the other 12 treatments. Changes in algal biomass will be monitored weekly with a hand-held fluorometer which measures chlorophyll a, net algal productivities will be monitored weekly by diel changes in dissolved oxygen, tilapia growth will be measured at the start and end of the grow-out experiment by length and weight measurements. Mid-afternoon water temperatures, turbidities, and ammonia-N will be monitored weekly in all 39 tanks.
3.Reclamation of Nutrients from Pond Water Discharge
Twenty tanks used in the grow-out experiment will be selected for their wide range of chlorophyll a and ammonia-N concentrations, and drained through clinoptilolite filters. Twenty clinoptilolite flow-through filters will be made from the 20-L buckets used in the bench studies. Assuming that 1 g of clinoptilolite can remove 2 mg of ammonia-N, then a tank with about 1 mg L-1 ammonia-N would require approximately 3 kg clinoptilolite. All 20 filters will contain identical quantities of clinoptilolite, the actual amount to be based on results of the preliminary bench studies and actual ammonia-N concentrations. The two factors will be the addition of clinoptilolite powder (CP, about 0.8 mm) to 10 tanks to flocculate P before going through the filter, and either "slow" or "fast" discharge flow rates. Actual pump rates will be determined on site. Therefore, this will be 2 ¥ 2 factorial designed experiment, with four treatments (i.e., CP-slow, no CP-slow, CP-fast, no CP-fast), with five replicates per treatment. Filter efficiencies will be determined by measurements of total P, soluble P, ammonia-N, nitrate-nitrite-N, and Kjeldahl-N before and after filtration.
AIT also has a well-established Training and Consultancy Unit which gives regional workshops on various aspects of aquaculture production systems. The knowledge generated from the proposed research can be readily incorporated into the appropriate workshop(s). There will also be five regional workshops on using pond dynamics to promote sustainable aquaculture included as a separate activity in this proposal. In addition to AIT, the other workshop locations will be at aquaculture research institutes and stations located at Bangladesh, Cambodia, Laos, and Vietnam where AIT and the PD/A CRSP have established formal relationships. Information generated from the above research will be incorporated into these proposed workshops. Strengthening ties between these countries and AIT and the PD/A CRSP is an important component of the Regional Plan For Southeast Asia.
All proposed research is scheduled to take place between January and May 2002. Knud-Hansen will make two trips to AIT, of approximately three weeks each (excluding periods away from AIT to give workshops). During the first trip the bench studies on ammonia absorption by clinoptilolite and subsequent release into culture water will take place, and the grow-out study initiated. During the second trip the grow-out study will be completed and the nutrient reclamation study on pond water discharge will be conducted. Final report will be submitted no later than 31 July 2002.
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