ระบบบำบัดไนเตรทเพื่อการเพาะเลี้ยงสัตว์น้ำด้วยระบบหมุนเวียนน้ำแบบปิดขนาดเล็ก / อำไพเทพิน สิงหะพันธุ = Nitrate treatment system for small scale closed recirculating aquaculture system / Ampaitepin Singhabhandhu
The denitrification system consisted of a long tube with packing material was designed and tested in this study. The system operated by a combination of bacteria activities in fore part of the tube that consumed oxygen and bacteria in the rear part of the tube that provided denitrification. This could eliminate the use of nitrogen gas for purging dissolved oxygen in the previous design. In this study, the original design of the long tube system using oyster shell as packing material was not success because irregular shape of the cracked shell clotted the system after only 2 week operation. Therefore plastic balls named "Super Bioball" were then use instead of oyster shell. A new long tube system was built using PVC tube (1" diameter and 50 meter length) packing with 2,870 bioball. A sampling valve was attached to every 10 meter of the long tube and methanol (carbon source) was feed into the tube at 4.5 ml/hr by peristaltic pump. The experiment were performed with artificial wastewater with 100 ppm nitrate and high nitrate concentration seawater from shrimp pond. The results show that the long tube denitrification system could reduce nitrate in an artificial wastewater from 145.4 mg-NO3- -N/L to 2.9 mg-NO3- -N/L in 8 days. The system also performed well with high nitrate seawater but only when methanol were added as a sole carbon source. The nitrate treatment efficiency rose from 2.96% without methanol addition to 31.08% when adding methanol at 4.5 ml/hr and decrease to 6.61% when stop methanol feeding. However, it was found that incomplete denitrification indicated by slightly increase of nitrite and ammonia in the system was found during operation.
