Effect of Natural Colloid on Ammonia Nitrogen Transport in Water-bearing Media

Effects of natural colloids on transport of ammonia nitrogen were studied in sand packed laboratory columns under five different concentrations of colloid.Solutions of deionized water(DI),70,160,265 and 630mg/L were used in saturated columns.Results showed that breakthrough curves of ammonia nitrogen presented as three stages including not-yet-breakthrough,breakthrough in process and complete breakthrough.The pore volumes of three stages were different under various colloid concentration conditions.When colloid concentrations were 70mg/L and 160mg/L,the presence of colloids facilitated the transport of ammonia nitrogen through sand columns,which the pore volumes of ammonia nitrogen complete breakthrough were obtained smaller than in the absence of colloids,while colloid concentration at 265mg/L and 630mg/L were opposite,which showed that there was a critical colloid concentration between 160mg/L and 265mg/L,with colloid facilitating ammonia nitrogen migration when its concentration up to the critical concentration and retarding when beyond the critical concentration.