Maintaining Favourable Fermentation Conditions in Sargassum Liquid Fertilizer Production using Siphon in A Two-Containers System Resulting in Acceptable Levels of Heavy Metals

A U-shapedsiphon was used to connect two 600 mL disposed of mineral water-plastic bottles called container A and B. Container A served as a decomposer drum for mixingSargassum porridge, EM4 (effective microorganisms 4), organic nutrients, and water to allow an anaerobic fermentation to occur within 25 days.B was an aeration drum containing an acceptable volume of freshwater. Between these two containers, the siphon was set to bridge the air between containers above the suspension. There were 14 different configurations including a siphon with three different diameters (0.5, 1, 1.5 cm), four different lengths (16, 18, 20, 22 cm), and three different connections (connected to aeration drum, opened to air, closed). The last two configurations did not need the siphon. During the fermentation process, gas and heat were perceptibly released inone way-flowing from A to B and creating bubblesin Bleading to a maintained condition of the fermentation. As the one of main challenging aspects in the production of sargassum liquid fertilizer (SFL) is the considerable number of heavy metals, therefore, we measured some transition metals levels extracted in the filtrate post-25 days to estimate the safety level of the product compared to those mentioned in the Regulation of the Indonesian Ministry of Agriculture (Permentan70/SR/140/10/2011). All data excluding sample S4 were below the limit, except Cd level, whereby two configurations gave the least values of potentially toxic elements, which might be linked to the role of the siphon in giving a favourable condition for preventing the release of the heavy metals trapped in the cell walls.