ประสิทธิภาพของแบคทีเรียบาซิลลัสทนเค็มสำหรับบำบัดอนินทรีย์ไนโตรเจนในน้ำเลี้ยงกุ้งทะเล

Abstract

Effluent water from shrimp aquaculture usually contains high organic matters and inorganic nitrogen, especially ammonia-nitrogen which is highly toxic to shrimp. Removal of ammonia is therefore important for improving water quality in shrimp culture. Bacilli are group of bacteria that could remove ammonia in nitrification and aerobic denitrification process. The objectives of this study aimed to isolate and identify halo-tolerant Bacillus and to determine the efficiency of improvement inorganic nitrogen in marine shrimp cultured water. Bacillus strains TS23, TW24, TW31, TW34, BR001, and BR002 were isolated from sediment and water samples. They have the characteristic of heterotrophic nitrifying-aerobic denitrifying bacteria. All strains showed high ammonium oxidizing removal more than 90% and showed the capability of nitrite- oxidizing and nitrate-reducing from 25 to 50%. Based on 16S rDNA gene sequencing data and phylogenetic analysis, 6 strains were identified as Bacillus pumilus (TS23), B. cereus (TS31), B. subtilis (TW24 and TW34) and B. tequilensis (BR001 and BR002). The optimal salinity and pH for growth of isolated Bacillus were in the range of 0.5-3% NaCl and 7-7.5, respectively. Applied density of 1% cell suspension of TW24, TW31, TW34, BR001, and BR002 has presented maximal removal of inorganic nitrogen in synthetic wastewater at 7 days. These 5 strains have the capability to remove ammonia, nitrite, and nitrate in the range of 84.7-86.5%, 78.8-83.1% and 66.2-73.3%, respectively. Strains TS23, BR001 and BR002 provided high removal inorganic nitrogen in sterile and non-sterile shrimp cultured water during day 4 to day 7. Ammonium removal ability of TS23, BR001 and BR002 were 63.5, 64.1, and 63.4% respectively; nitrite removal were 66.0%, 71.8% and 63.4%, respectively and nitrate removal were 69.1%, 62.5% and 45.6%, respectively. The proficiency of 3 isolates has decreased the amount of orthophosphate in the range of 45.5-69.1% as well as 46.1-52.9% of total suspended solids.