NITRIFICATION RATE OF SEAWATER SUBMERGED BIOFILTER AT THREE DIFFERENT OPERATING TEMPERATURES (15ºC, 25ºC DAN 35º CC)

• Main Author: Lestari Taufan, Winda
• Format: Theses
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/57868
• Institution: Institut Teknologi Bandung

Biofilter is one of the important components in Recirculating Aquaculture System (RAS) which functions to accelerate the decomposition rate of ammonia and nitrite in water. Submerged Biofilter is the commonly used type of biofilter. This biofilter has filter media for the immobilization of nitrifying bacteria during biofilm formation. In this filter media, the decomposition process of ammonia and nitrite is carried out by nitrifying bacteria, including Ammonium Oxidizing Bacteria (AOB) and Nitrite Oxidizing Bacteria (NOB) in biofilm form. Nitrification rate is highly influenced by nitrifying bacteria activities and environment factors, such as biofilter water temperature. This study aims to find out the nitrification rate and to analyse the microbial diversity at three different operating temperatures: 15ºC, 25ºC, and 35º C. The steps conducted in this research include: (1) Nitrifying bacteria cultivation and activity, (2) Biofilter installation, (3) Experiment setting, (4) Nitrification rate calculation (5) Alkalinity analysis, (6) Microbial enumeration using Total Plate Count (TPC) method, (7) Scanning Electron Microscopy (SEM) analysis, (8) Research analysis using Kruskal Wallis test in R method. The research was conducted for 15 days. According to the analysis using Kruskall Wallis test in R method, it is shown that the decomposition rate of the three treatments has no significant difference (p – value = 0.774). However, the highest presentation of ammonia decomposition rate is at 33,40% with total of decomposed ammonia of 6,8 ppm/day at 25ºC. Meanwhile, the decomposition rate at 15ºC reached 29,02% with total of 6,6 ppm/day, and 27,07% with total of 6,3 ppm/day at 35ºC. The result of microbial community analysis showed that the highest abundance of nitrifying bacteria isolates was found at 25ºC. Scanning Electron Microscopy (SEM) analysis also showed an aggregation from bacterial flocculation which indicated the formation of biofilm from the nitrifying bacteria activities. Moreover, alkalinity test was conducted to figure out the picture of alkaline capacity in biofilter tank. Alkalinity test using titration method with Alkalinity Test Kit Merck showed results that the highest value is 132?0.29 and occurred at temperature of 15?C, which indicated that the pH in this biofilter tank was more stable than the other two temperature treatments. The second highest alkalinity value is 113?0.19 at 35?C, and the lowest one is 107?0.29 at 25?C. Alkalinity level provides Bicarbonate Ion (HCO3), which are utilized by nitrifying bacteria in biomass formation, hence the higher the activity of nitrifying bacteria, the lower the alkalinity value. The alkalinity value proved that the highest activity of nitrifying bacteria occurred at the temperature of 25?C. This test is also supported by the result of dominance index test which was higher at 25?C and showed a lower diversity and stability index value. Referring to the research results, the dominant bacteria at 25?C is assumed to be nitrifying bacteria group. Therefore, it can be concluded that temperature setting at 25?C in biofilter tank is the convenient setting for the growth of nitrifying bacteria and to accelerate nitrification rate of seawater submerged biofilter.