Establishment of NH_3-N Prediction Model in Aquaculture Water Based on ELMAN Neural Network

In the present study, ELMAN artificial neural network model was developed to predict the change of NH3-N in aquaculture water. The in- dexes including feed ration, dissolved oxygen in water, water temperature, air temperature, water turbidity, rainfall were recorded and chosen as the input variables, while the NHz-N content in the corresponding pond was chosen as output variable. The above data were collected everyday from June to October in 2014 and were used to develop model in this test, and the data collected in November of 2014 were chosen to evaluate the developed model. The results showed that the changing trend of NH3-N in aquaculture water could be simulated well by the model, the predictive absolute error mean was 0.016 mg/L, and Nash-Sutcliffe efficiency coefficient was 0.74. The prediction model based on ELMAN neural network had a strong ability to describe the nonlinear dynamic changes of NH3-N content in aquaculture water, and it showed the good adaptability and accu- racy in practical application.

Comparison on Purification Effect of Two Macroalgae Species on Prawn Tailwater

[Objectives]This study was conducted to investigate the purification effects of two common large seaweeds on the tail water of prawn farming in greenhouses,and to determine the best culture density of seaweeds.[Methods]Two large seaweed species,Gracilaria lichevoides and Ulva lactuca,were selected to set four culture densities of 0.5,2,4 g/L and a blank control group,respectively.The seaweeds were cultured in 100 L white polyethylene buckets,each of which contained 50 L of tail water from prawn culture.[Results]After 5 d,the nutrient removal rates of the two seaweeds were directly proportional to the density.There was no significant difference in NH_(4)-N removal rate between G.lichevoides and U.lactuca(P>0.05)by two-way analysis of variance,and the NH_(4)-N removal rate of the latter was higher.The removal rates of NO_(3)-N,TN and TP by G.lichevoides were significantly higher than those by U.lactuca(P<0.05).The specific growth rates of seaweeds were negatively correlated with their culture densities.The specific growth rates of G.lichevoides were 5.73%,1.654%and 0.48%,respectively,and those of U.lactuca were 2.01%,1.187%and 0.138%,respectively,when the culture densities were 0.5,2.0 and 4.0 g/L.Two-factor analysis of variance showed that the former was significantly higher than the latter,when the culture density of the two species of seaweeds was 0.5 g/L(P<0.05).The two-way analysis of variance showed that when the culture density of the two kinds of seaweeds was 0.5 g/L,the specific growth rate of G.lichevoides was significantly higher than that of U.lactuca(P<0.05).Based on the above research,the two macroalgae could reduce the nutrients in the wastewater to a large extent,but the culture density determined the scale and economic benefits of seaweed cultivation and further affected the normal growth,metabolism and quality of the seaweeds.[Conclusions]This study provides some theoretical basis for large-scale seaweed farming and biological selection of in-situ ecological restoration of eutrophic seawater.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water:Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics(FQs)in synthetic marine aquaculture water were subject to sodium hypochlorite(NaClO)disinfection scenario to investigate their reaction kinetics and transformation during chlorination.Reactivity of each FQ to NaClO was following the order of ofloxacin(OFL)>enrofloxacin(ENR)>lomefloxacin(LOM)>ciprofloxacin(CIP)?norfloxacin(NOR)>>pipemedic acid(PIP),while flumequine did not exhibit reactivity.The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO,while humic acid was inhibitable to their degradation.The bromide ions promoted degradation of CIP and LOM,but restrained oxidation of OFL and ENR.By analysis of liquid chromatography with tandem mass spectrometry(LC-MS/MS),eight kinds of emerging brominated disinfection byproducts(Br-DBPs)caused by FQ S were primarily identified in the chlorinated synthetic marine culture water.Through density functional theory calculation,the highest-occupied molecular orbital(HOMO)and the lowest-unoccupied molecular orbital(LUMO)characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms.Their formation involved decarboxylation,ring-opening/closure,dealkylation and halogenation.Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position.The piperazine ring containing tertiary amine was comparatively stable,while this moiety with a secondary amine structure would break down during chlorination.Additionally,logK_(ow)and log BAF of transformation products were calculated by EPI-Suite^(TM)to analyze their bioaccumulation.The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.