Performance Evaluation and Microbial Shift of Sequencing Batch Biofilm Reactor Treating Synthetic Mariculture Wastewater Under Different Dissolved Oxygen at Aerobic Phase

The impact of dissolved oxygen(DO)at aerobic phase on the nitrogen removal,extracellular polymeric substances(EPS),microbial activity and microbial community of sequencing batch biofilm reactor(SBBR)have been evaluated in treating mariculture wastewater.The oxygen uptake rate and nitrification rate declined with DO concentration from 3–4 to 1–1.5mgL^(-1),whereas the denitrification rate had an increment.The activities of nitrifying enzymes reduced with the decrease of DO concentration at aerobic phase,but those of denitrifying enzymes illustrated opposite results.The nitrification and denitrification rates displayed the similar variation tendency with the relevant enzymatic activities as DO concentration decreased.The protein(PN)and polysaccharide(PS)content in EPS decreased as DO concentration declined,whereas the PN/PS ratio increased.The microbial community showed obvious difference as DO concentration decreased from 3–4 to 1–1.5mgL^(-1).The microbial co-occurrence,keystone taxa and sig-nificant difference illustrated some variations at different DO concentrations.

Enhancement of Penaeus vannamei shrimp growth using nanobubble in indoor raceway pond

The effects of nanobubble on the growth environment,such as dissolved oxygen(DO)and total virus-bacteria,and growth performance,such as growth,feed conversion ratio(FCR),survival rate(SR),total harvest,and productivity,were investigated in Penaeus vannamei shrimp ponds.The present study was carried out in 50 m2 indoor raceway ponds for 81 days with stocking density being set to 680 shrimp m3 in two types of treatment:nanobubble and diffuser aerator.A paddlewheel was used to distribute the oxygen saturation levels throughout the ponds.The presence of nanoparticles was detected using a dynamic light scattering method and was reported to be 82.38 nm in size and26 mV for zeta potential value.DO was significantly higher under nanobubble treatment.Total virus-bacteria and FCR decreased,whereas SR,growth(weight and length),total harvest,and productivity increased with increasing DO.The SR was reported to reach 95%.The average weight and length of P.vannamei were 15.1±1.8 g and 13.1±1.1 cm,respectively.The total harvest and productivity have doubled to 436 kg and 8.7 kg/m3.The results revealed that nanobubble has managed to maintain DO at the optimal range and affected the shrimp growth significantly(P<0.05).