Oxidation Of Ammonia In Fish Ponds To Nitrates Using Free and Immobilized Nitrifying Bacteria

In fish farming, ammonia stands out as a particularly detrimental toxicant, with the potential to significantly impede growth and even lead to fish mortality. The adverse effects of ammonia exposure in aquatic environments primarily stem from elevated concentrations of unionized ammonium (NH3), which can readily permeate gill membranes. This study aimed to mitigate ammonia levels in fish ponds by employing both free and immobilized nitrifying bacteria to convert ammonia to nitrates. Nitrifying bacteria were isolated from water samples, resulting in the identification of two Pseudomonas species and two Bacillus species. Bacillus spp., designated as B4, exhibited the ability to convert ammonia to both nitrite and nitrate while demonstrating resilience to high ammonia concentrations. When Pseudomonas spp. (C4) and Bacillus spp. (B4) were utilized, the total ammonia concentration was reduced from 2 mg/L to 1.4 mg/L and 1.3 mg/L, respectively. Moreover, the immobilized forms of C4 and B4 achieved a more substantial reduction, lowering the total ammonia concentration from 2 mg/L to 0.5 mg/L within a 5-day period. Both nitrifying bacteria not only exhibited ammonia removal capabilities but also demonstrated their proficiency in transforming ammonia into nitrite. Immobilization proved effective in enhancing microbial tolerance to high ammonia concentrations, ultimately leading to improved water quality and the preservation of aquatic animal health.