Efficacy Of Spirulina Platensis In Treating Marine Aquaculture Wastewater And Its Continuous Operation Effect In MPBR

With the rapid development of the marine aquaculture industry,the development of coastal areas has been promoted,but the wastewater discharge and wastewater treatment have become an important issue for the ecological development of coastal areas.The discharge of a large amount of farming wastewater will affect the aquaculture water body and the adjacent sea water body or even deep sea water area,resulting in the deterioration of the water environment and the eutrophication of the water body,which will destroy the ecological balance and biodiversity.The large water volume,high salinity,and low carbon-to-nitrogen ratio of marine aquaculture wastewater increase the difficulty of treatment.Spirulina platensis as a facultative heterotrophic microalgae with high economic value,can not only effectively reduce the concentration of nutrients in sewage to obtain higher biomass energy,but also have higher salinity tolerance,and can be suitable for containing Treatment of marine aquaculture wastewater with high salinity.In addition,Spirulina platensis has a certain capacity of algae self-settlement in marine aquaculture wastewater.In this study,Spirulina platensis was used to treat marine aquaculture wastewater.The effects of inoculation concentration,organic carbon concentration,and nitrogen concentration on wastewater treatment efficiency and biomass production were studied through batch experiments,and the algal body self-sedimentation capacity was monitored.On the basis of batch experiments,a membrane photosynthetic bioreactor was constructed to recover algal bodies with high nutritional value while achieving efficient removal of carbon,nitrogen,and phosphorus.This thesis mainly includes the following sections:(1)The effects of inoculation concentration,organic carbon concentration,and nitrogen concentration on wastewater treatment effects were studied through batch experiments.The results show that Spirulina platensis can effectively remove contaminants in marine aquaculture wastewater.The optimal inoculation concentration is 0.12 g/L;the increase of organic carbon concentration is beneficial to the growth of microalgae and the removal of nutrients,and the removal rate of nutrients is increased;the increase of nitrogen concentration will reduce the removal effect of microalgae on nutrients.In addition,the nitrogen assimilation of spirulina in marine aquaculture wastewater is mainly through the GS/GOGAT cycle.Too high ammonia nitrogen concentration will inhibit GS and GOGAT enzyme activities.On the contrary,when the ammonia nitrogen concentration is too high,GDH enzyme activity will increase,which can offset the accumulation of ammonia nitrogen.Reduce the impact of nitrogen stress.(2)The biomass yield and self-sedimentation of algae in Spirulina platensis in marine aquaculture wastewater were studied under different conditions.The results showed that the inoculation concentration had little effect on the biomass production of algae;the increase of organic carbon concentration was conducive to lipid accumulation.Proper increase of nitrogen concentration can increase protein content,which is not conducive to lipid accumulation.When the nitrogen concentration is greater than 50 mg/L,it is not conducive to microalgae growth or biomass accumulation.In the case of changing the inoculation concentration,organic carbon concentration,and nitrogen concentration in marine aquaculture wastewater,the self-sedimentation efficiency of microalgae can reach more than 86.5%,and the highest can reach 98.1%,which can reduce the use of microalgae to treat wastewater to some extent.Recovery costs.For the algae that cannot be fully harvested,it can be used for breeding feed with circulating water.(3)Based on batch experiments,a microalgae membrane photosynthetic bioreactor(MPBR)was constructed to study the continuous long-term operation of Spirulina platensis in marine aquaculture wastewater and microalgal biomass production.The results show that the treatment of marine aquaculture wastewater with Spirulina platensis in MPBR can run stably for a long time,and has obtained relatively ideal biomass.The reactor effluent with non-woven fabric as membrane material is relatively more stable and the effluent quality is better.The average effluent concentrations of TN,TP and COD are 0.57 mg/L,0.07 mg/L and 4.13 mg/L,respectively Nitrate accumulation.Slight membrane fouling was found in the reactor RA.The RB reactor with non-woven fabric as the membrane material had no membrane fouling,the membrane flux was large,it was easy to clean,and the cost was also lower.