การพัฒนาหน่วยแยกตะกอนและผลของตะกอนต่อคุณภาพน้ำในระบบเลี้ยงสัตว์น้ำแบบปิด / ศิวฤกษ์ หนูฤทธิ์ = Development of solid separating unit and the effect of solid to water quality in closed aquaculture system / Siwaruek Nurit
This research aims to develop the solid separating system for closed-water aquaculture and assess the system performance with aims to improve the efficiency of nitrifying and denitrifying biofilters in treatment inorganic nitrogen compounds. The research also investigates the possibility of utilizing the separated solid as microbial seeding in biofloc aquaculture system.The experiment result is divided in 4 parts. The first experiment studied the effect of solid on water quality. The result indicated that high concentration of suspended solids led to accumulation of ammonia and nitrite at dangerous levels for extended period, thereby confirming the need of solid separating system. The second experiment developed the solid separating system and conducted testing of the proposed designs. Evaluation of the proposed systems showed that the separating unit containing 8-storey circular PVC sheet was the most effective at 71.3±2.4% removal efficiency at the flow rate of 180 L/hr. The initial testing of this particular unit with the closed-water tilapia cultivation (without biofilters) demonstrated that the presence of solid separating system could lower the concentration of ammonia, nitrite, nitrate and suspended solids in comparison with the cultivation without the solid removal. In the third experiment, the solid separating unit was used with aquaculture (i.e., tilapia) system integrating nitrifying and denitrifying biofilters. Increasing ammonia, nitrite and nitrate concentrations as well as increasing suspended solids were observed when the solid separating system was not in use. In contrast, simultaneous operation of the solid separating system along with optimal supply of methanol to denitrifying biofilter could maintain acceptable ammonia, nitrite and nitrate concentrations below 0.4, 0.6 and 15.9 mg N/L and suspended solid concentration less than 35 mg SS/L. For the last experiment, separated solids were used as microbial seeding for biofloc system. The result indicated the suspended solids in water in the range from 300 to 500 mg SS/L could keep ammonia and nitrite concentrations in acceptable range. Moreover, the presence of biofilters and solid removal system was crucial in maintaining acceptable inorganic nitrogen and suspended solid concentrations.