Study On Nitrogen Removal Effect Of Dynamic Membrane Bioreactor For Mariculture Wastewater Treatment

In recent years, along with the rapid development of Chinese marine aquacultureindustry, the problem of mariculture wastewater treatment is increasingly outstanding.There are rare special technologies of method for mariculture wastewatertreatment.Based on the above problem, dynamic membrane bioreactors were used totreat mariculture wastewater in this paper. The effects of salinity and hydraulicresidence time on CODMnand nitrogen removals were studied. Morever, the kineticanalysis was performed for the organic matter degradation and denitrification processof the system. Also the microbial community structure of bioreactor was investigated.When salinity was0³000mg·L^-1, the removal rates of CODMnand NH4+-N in thecontinuous aeration DMBR kept stable. But when salinity is1000mg·L^-1, the removalrate of NO3--N improved from73%to97%. Under the experimental condition ofsalinity0³5g·L^-1, with the increment of salt concentration, the general trend ofremoval efficiencies of continuous aeration DMBR and intermittent aeration DMBRreduced. The removal rates of CODMnreduced by18.90%and14.51%, respectively.The removal rates of TN reduced by24.36%and13.41%, respectively.With the prolonging the time of HRT, the removal rates of organic compounds andTN in intermittent aeration DMBR and continuous aeration DMBR for mariculturewastewater treatment raised. The removal rates of CODMnimproved by16.53%and10.22%, respectively. The removal rates of TN improved by11.91%and10.54%,respectively. But in freshwater, the optimal HRT for continuous aeration DMBR was6h. When continuous aeration DMBR was in the ptimal HRT, the effluentconcentrations of CODMnand TN of continuous aeration DMBR were0.72mg·L^-1and1.18mg·L^-1, respectively.The paper gave kinetic analysis on organic matter degradation and denitrificationprocess. And the kinetic equations for the reactions were abtained, repetitively. TheCODMnremoval rate and NH4+-N removal rate by continuous aeration DMBR fortreating aquaculture wastewater followed the Monod equation. And their kinetic equations can be expressed as:d_Sc/dt=0.25C/147.73+C and dSN/dt=0.096N/3.58+N。Under highconten of salt, CODMnand NH4+-N degradation rates were inhibted by salt. And theinhibition equation of salinilty were written as:r_N=14.91N/4.22+N·349.47/349.47+Y andr_c=38.23C/1.37+C·165.67c/165.67+Y。For the intermittent aeration DMBR, the the effects of thesalinity on CODMndegradation and denitrification rate constants were mainlydiscussed. The results show that the CODMndegradation and and denitrification rateconstants droped linearly with the salinity increasing. And the linear equations wereyC=-0.0057XC+0.5562，yN=-0.0143XN+4.9884, respectively.In order to research environmental microbial community diversity in DMBRs,PCR-DGGE technique was used in this paper. DGGE electrophoresis patterns of fouractivated sludge samples showed the microbial diversity. In general, the microbialcommunity of continuous aeration DMBR for treating mariculture wastewater wasmore abundant than other bioreactors. By comparing similarity of differentbioreactors, found that the highest similarity was between intermittent aerationDMBR and continuous aeration DMBR for mariculture wastewater treatment.According to DGGE map, selected the bands with stronger signals for gel extractionand sequenced. The majority of clone sequences belonged to α-Proteobacteria,β-Proteobacteria, γ-Proteobacteria, δ-Proteobacteria, Sphingobacteriia, Clostridia andActinobacteridae. Then established the phylogenetic tree of selected bacteria from thebioreactors, and analyzed the similarity between bacteria.