Fig. 2a. Pond 41 at fish farm A. (Photo: Morten S. Bruun) Fig. 2b. Raceway at fish farm B. (Photo: Morten S. Bruun) Fate and Discharge of Chemical Additives Investigation of the additives in water and sediment showed that hydrogen peroxide was fast degradable with half-lives of a few hours, whereas formaldehyde and chloramine-T were reduced to a lesser extent. A large part of the copper was retained in the sediment at the concentrations used. The hydraulic model could predict the course of the concentration; the model concentrations were in accordance to measured values with regard to time and magnitude (Figure 3). The modified hydraulic model could describe concentration patterns of the four chemicals to a satisfactory level. The model tends to overestimate the calculated values which indicates that additional elimination processes are not completely described. Inasmuch as the model in general predicts discharge concentrations of chemicals in agreement with measured concentrations, it can be applied to practical and administrative purposes. 600 E 500 i 400 -� 300 g 200 "C C: 8 100 Treatment pond 0 -----.----.----,-----..-�-----,.---,-----, 0 2 4 6 8 1 0 12 14 16 Time (h) Settlement pond 70 1:: v.� I :: 1· • �•••• ••••••••• 8 4 5 i 40 +-- - - - --- - - - - - - - - - � 2 4 6 8 1 0 12 14 16 Time (h) The full line represents the output values from the model (PoolSim) The open symbols represent measured values (conductivity correlates to concentrations of NaCl) Fig. 3. Comparison of predicted NaCl concentrations (Pao/Sim) and measured values at farm A. 12 10 12 10 'a, 6 Fig 4a. Sulfadiazin, Farm A, 1 . day of treatment of five ponds at 8:00 -+-Inlet -Pond -outlet Fig4b. Sulfadiazin, 1 hour after medication of five ponds. 11 /7 is the last day of treatment -+-Inlet -Pond -outlet Fig 4c. Sulfadiazin, Farm A, last day of treatment of five ponds at 8:00 >ir.s a;;o ..900 7 0 0 0 7700 �oo 7iroo 7..9 S'o -+-Inlet -Pond -outlet Fig. 4a,b,c. Concentrations of sulfadiazin in fish farm water during treatment of five ponds. WORLD AQUACULTURE 59
RkJQdWJsaXNoZXIy MjExNDY=