Utilization of kolong for aquaculture: use of compost to minimize concentration of lead (Pb) in fish culture media

Abstract

Kolong (lakes formed of ex-tin mining) has good potency to use for aquaculture activity but so many kolong in Bangka Belitung archipelago weren’t used for this purpose because of its low pH, and high heavy metal level, especially lead (Pb). Fish culture in lead containing- water is very risk. Accumulation of lead in the body of fish above safe level of consumption is one of the problems in the field that need to be solved. Compost could be able to minimize lead in aqueous media and increase the pH of water. The purpose of this research was to determine the best material of compost and its level to minimize lead in fish culture media. Minimization of lead metal by compost occurs through cation exchange, electrostatic binding, complex binding and chelating. The treatment with compost of gamal leaf, avicennia leaf, and banana stem with the level of each composts were 5 gr/l, 9 gr/l, and 13 gr/l by aeration for 24 hours. The measurement of lead metal level reduction in the water were repeated in every 1st, 8th, 16th and 24th hour. The treated water (after 24th hour treatment) then been used to culture 14 days aged-seed of catfish for 30 days. The results showed that the compost was able to minimize lead in the media more than 80% with gamal leaf at 9 gr/l and banana stem at 9 gr/l as the best material and level of compost in the media. The compost increasing the pH of media so that the survival rate and the growth rate of the fish were increased.

Danau bekas galian timah atau kolong yang berusia muda banyak terdapat di Kepulauan Bangka Belitung. Kolong-kolong ini memiliki potensi untuk dimanfaatkan bagi kegiatan akuakultur. Namun permasalahan utama yang dihadapi yaitu pH air yang rendah dan tingginya kandungan logam berat di air. Timah hitam (Pb) merupakan salahsatu logam berat berbahaya yang terdapat di air kolong. Logam ini merupakan mineral non esensial yang sama sekali tidak dibutuhkan oleh tubuh. Air yang mengandung logam berat Pb tentunya tidak layak digunakan untuk budidaya ikan. Oleh karena itu perlu dilakukan treatment terhadap air agar air layak digunakan untuk budidaya ikan. Kompos merupakan salahsatu bahan yang dapat digunakan untuk meminimalisasi logam berat Pb di air. Kandungan substansi humus, seperti : asam humat, asam fulvat dan humin yang jumlahnya dominan merupakan substansi yang berperan dalam proses minimalisasi. Selain itu kandungan mineral yang terdapat pada kompos walaupun jumlahnya tidak dominan dapat mengalami pertukaran dengan ion Pb. Proses minimalisasi logam Pb di air terjadi melalui pertukaran kation, ikatan elektrostatik, pementukan senyawa kompleks dan chelate.