Dissolved organic nitrogen (DON) is currently considered to be one of the most important issues in drinking water field due to its formation of nitrogenous disinfection byproducts.This paper deals with DON concentrations in typical processes of a water treatment plant.The results show that very little DON is removed by these processes.Furthermore,biological activity in some processes can even increase DON concentration and decrease the ratio of dissolved organic carbon/DON,which may pose a risk to drinking water safety.
The biologic activated carbon(BAC)process is widely used in drinking water treatments.A comprehensive molecular analysis of the microbial community structure provides very helpful data to improve the reactor performance.However,the bottleneck of deoxyribonucleic acid(DNA)extraction from BAC attached biofilm has to be solved since the conventional procedure was unsuccessful due to firm biomass attachment and adsorption capacity of the BAC granules.In this study,five pretreatments were compared,and adding skim milk followed by ultrasonic vibration was proven to be the optimal choice.This protocol was further tested using the vertical BAC samples from the full-scale biofilter of Pinghu Water Plant.The results showed the DNAyielded a range of 40μg·g^(-1) BAC(dry weight)to over 100μg·g^(-1) BAC(dry weight),which were consistent with the biomass distribution.All results suggested that the final protocol could produce qualified genomic DNA as a template from the BAC filter for downstream molecular biology researches.
