The Membrane Bioreactor (mbr) To Deal With High Salt Wastewater

Nowadays,in the bio-treatment process of high salinity wastewater,it is tailed to reach an agreement in organics and ammonia removal with salinity effect.Still the technology like A/O,SBR,conventional activated sludge process and so on are adopted from the home and abroad.So far,membrane bioreactor in high-saline wastewater treatment is not reported.The paper researches the organics and ammonia removal regularity during the high-saline wastewater treatment with MBR.Through test,it is reached a conclusion in organics and ammonia removal regularity(based on different operating conditions such as salinity,organic loading,ammonia loading,pH value and HRT),what's more,tremendous efforts is placed on membrane fouling mechanism research and the measures to relieve it are presented.Many fruits can be concluded from the experimental test.During the treatment process of wastewater containing different content of seawater,the conditions are as below: COD_cr is 800～1000mg/L,NH₃-N is 80～100mg/L,pH is 7.0～8.5,MLSS is 7000mg/L,DO is 2～4mg/L,temperature is 20～25℃.The results show that COD_cr removal percentages are 93%,87%and 75%respectively when the wastewater contains 30%,50%and 70%seawater.NH₃-N removal percentages are 95%,91%and 85% respectively when the wastewater contains 40%,60%and 70%seawater.What's more, SVI is lower and lower with the higher and higher seawater content.MBR process is used to treat wastewater containing 50%seawater with the conditions as below:COD_cr is 300～2600mg/L,NH₃-N is 50～300mg/L,pH is 6.0～9.0,MLSS is 7000mg/L,DO is 2～4mg/L,temperature is 20～25℃.The results show that both COD_cr and NH₃-N removal can reach 90%with the best conditions as below:organic loading and ammonia loading are less than 3.2kgCOD/m³·d and 0.35kg/m³·d respectively,pH is between 7.5 and 8.5,HRT is more than 12h.Membrane fouling is an inevitable problem in membrane separation,and it is the priority to control in MBR technology.Both the membrane module effluent rate and power are affected largely by it also.During the test,membrane fouling can be relieved when PE hollow fiber membrane and intermittent operation are adopted.The extracellular polymeric substances(EPS) which are excreted by microorganism devote to membrane fouling largely in the process.Water flushing and NaClO solution soaking can be effective cleaning method to recover membrane flux,and the trans-membrane pressure falls from 15.7kPa to 3.5kPa after cleaning.