Ammonium Removal From Saline Wastewater By The Noval Membrane Electrodialysis

High salt-ammonia wastewater has the quality of complex composition,high salinity and poor biodegradability,and the discharge of it could cause tremendous damage on natural environment.In this study,the traditional electrodialysis,Donnan dialysis and concentration electrodialysis were studied in high salt-ammonia nitrogen wastewater treatment.The results showed that traditional electrodialysis could effectively remove salt-ions from high salt-ammonia nitrogen wastewater.The time for treatment could be reduced from 20 hours to 8 hours as the current density increased from 30 mA/cm2 to 90 mA/cm2.The removal efficency of salt cationic was 61.0%,and that of NH4+ and Na+ was 76.2%and 51.2%,repectively,in the conditions that current density was 90 mA/cm2 and the processing time was 8 hours.The seperation efficiency of Donnan dialysis could be effectively improved by optimizing the experimental conditions.The removal efficiency of NH4' was improved from 54.3%to 85.2%as the initial brine concentration reduced from 20%to 5%.When the stirring intensity increased from 200 r/min up to 500 r/min,the seperation efficiency increased from 49.6%to 54.3%,and the processing time was shortted.Moderately increasing the temperature could improve the removal ratio of NH4'The concentrated electrodialysis was used to treat simulation high salt-ammonia nitrogen wastewater.The result showed that the removal ratios of NH4+ and Na+ were 86.9%and 1.3%,respectively,when the current density was 20 mA/cm2 and the processing time was 16 hours.The concentrated electrodialysis could effectively remove NH4+ from wastewater,the removal ratio was 86.9%,while the removal ratio was 55.1%and 80.7%by traditional electrodialysis and Donnan dialysis,respectively,and that of traditional electrodialysis could not achieve the purpose of separating NH4+ and Na+.The concentrated electrodialvsis was used to treat mariculture wastewater with lower current density.The results showed that the concentration of Na+ decreased to 10.98 g/L from 11.31 g/L,when the current density was 3.5 mA/cm2 and the processing time was 7 hours.The removal efficiency of NH4,improved with increasing the concentration of NH4+from 80 mg/L up to 160 mg/L.The removal rate of NH4+was 75.9%,when the current density was 3.5 mA/cm2,the initial concentration of NH4+was 80 mg/L and the processing time was 14 hours.