PENGENDALIAN LIMBAH AMONIA BUDIDAYA IKAN LELE DENGAN SISTEM HETEROTROFIK MENUJU SISTEM AKUAKULTUR NIR-LIMBAH
Abstract
Limbah amonia dari budidaya ikan yang dibuang langsung ke perairan sekitarnya merupakan sumber pencemaran yang perlu mendapat perhatian. Potensi pasokan amonia ke dalam air budidaya ikan adalah sebesar 75% dari kadar nitrogen dalam pakan. Pengubahan nitrogen dalam sistem akuakultur yang berperan dalam pengurangan kandungan amonia terdiri atas tiga proses yakni proses fotoautotrofik oleh alga, proses bakterial autotrofik yang mengubah amonia menjadi nitrat, dan proses bakterial heterotrofik yang mengubah amonia langsung menjadi biomassa mikroba. Proses mikrobial seperti tersebut dapat dimanfaatkan untuk meningkatkan kualitas air dan mengurangi beban cemaran limbah budidaya ikan ke perairan sekitarnya. Pada prinsipnya kandungan amonia di dalam air kolam dirangsang untuk berubah menjadi alga atau bakteri. Penelitian penerapan sistem heterotrofik untuk mengurangi beban limbah budidaya ikan lele (Clarias gariepinus) telah dilaksanakan di Loka Riset Pemuliaan dan Teknologi Budidaya Perikanan Air Tawar, Sukamandi. Air pemeliharaan ikan lele dialirkan ke ruang pemeliharaan ikan nila. Pemberian pakan hanya diberikan kepada ikan lele. Kandungan amonia yang ada dipacu untuk diubah menjadi biomassa bakteri dengan memberikan pasokan karbon berupa molases yang merupakan hasil samping pabrik gula. Hasil yang diperoleh setelah pengamatan selama 7 minggu menunjukkan bahwa kadar amonia dapat dipertahankan di bawah 0,1 mg/L NH3/L, produksi biomassa bakteri dalam bentuk padatan volatil total (total volatile solids, TVS) mencapai 85,5 mg/L dan pertumbuhan ikan nila mencapai 30,53%. Sistem heterotrofik mempunyai peluang untuk diterapkan dalam pemanfaatan limbah amonia pada pemeliharaan ikan lele. Namun demikian, masih diperlukan kajian lebih lanjut dalam rangka optimalisasi keragaan sistem heterotrofik dalam mendukung sistem akuakultur nir-limbah (zero-waste aquaculture).
Waste from fish farm which is directly discharged to the sorounding water is a potential source of pollution. Theoritically, about 75% of nitrogen in feed will be released as fish waste. Conversion of nitrogenous compound in aquaculture system, which plays a key role in ammonium reduction, consisted of three processes, i.e. phototoautotrophic algal, autotrophic bacterial conversion of ammonium to nitrate, and heterotrophic bacterial conversion of ammonium to microbe biomass. This bacterial process can be exploited to improve water quality in fish pond and simultanously decrease impact of fish culture waste. Principally, ammonium compound in water is directly converted to bacterial biomass. An experiment applying heterotrophic system in catfish (Clarias gariepinus) culture had been conducted at the Research Institute for Freshwater Fish Breeding and Aquaculture, Sukamandi. Water from catfish pond was flown to the tilapia pond. Feed was given only to catfish. Supplemented molasses as carbon sources was spread onto tilapia pond to enhance ammonium conversion to bacterial biomass. The results showed that during 7 weeks of observation, ammonium level in tilapia pond could be controlled below 0.1 mg NH3/L, production of bacterial biomass reached up to 85,5 mg/L in term of total volatile solids (TVS), whereas tilapia grew 30,53% from their initial weight. Heterotrophic system has a highly potential application in utilization of ammonium waste of catfish culture. However, it is still required advance studies to optimize this systems performance in relation to zero-waste aquaculture development.
Waste from fish farm which is directly discharged to the sorounding water is a potential source of pollution. Theoritically, about 75% of nitrogen in feed will be released as fish waste. Conversion of nitrogenous compound in aquaculture system, which plays a key role in ammonium reduction, consisted of three processes, i.e. phototoautotrophic algal, autotrophic bacterial conversion of ammonium to nitrate, and heterotrophic bacterial conversion of ammonium to microbe biomass. This bacterial process can be exploited to improve water quality in fish pond and simultanously decrease impact of fish culture waste. Principally, ammonium compound in water is directly converted to bacterial biomass. An experiment applying heterotrophic system in catfish (Clarias gariepinus) culture had been conducted at the Research Institute for Freshwater Fish Breeding and Aquaculture, Sukamandi. Water from catfish pond was flown to the tilapia pond. Feed was given only to catfish. Supplemented molasses as carbon sources was spread onto tilapia pond to enhance ammonium conversion to bacterial biomass. The results showed that during 7 weeks of observation, ammonium level in tilapia pond could be controlled below 0.1 mg NH3/L, production of bacterial biomass reached up to 85,5 mg/L in term of total volatile solids (TVS), whereas tilapia grew 30,53% from their initial weight. Heterotrophic system has a highly potential application in utilization of ammonium waste of catfish culture. However, it is still required advance studies to optimize this systems performance in relation to zero-waste aquaculture development.
Keywords
intensive aquaculture; zero-waste aquaculture; heterotrophic system; ammonium
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PDFDOI: http://dx.doi.org/10.15578/jra.3.3.2008.437-448
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