The purpose of this research was to suggest the water quality improvement in streams by evaluating the distribution characteristics of organics and ammonia nitrogen discharged by pollution sources from human living. The public sewage treatment plants'(PSTPs) effluents and the waters from streams in Gyeonggi-do were sampled and analyzed. Nitrogenous oxygen demand (NOD) was measured for the stream waters as well as the PSTPs effluents, and the correlations of NOD and NH3-N, NH3-N and water temperature in the PSTPs effluents were confirmed. In the case of the stream waters, the ratios of NOD to BOD and NH3-N increased in the downstream sites after discharging the PSTPs effluents. As a result of statistical analysis of NH3-N concentrations for the national water quality monitoring streams in Gyeonggi-do, NH3-N showed the non-normal distribution which were biased to the left, but showed the considerable level because of higher coefficient of variation. Therefore, it is required to establish the water quality standard for the NH3-N as a new parameter for judging the quality of the streams. In addition, inducing complete nitrification and introducing a logical standard setting system are needed to improve the water quality of streams by identifying distribution of the nitrogen components from PSTPs effluents.

This study aimed to evaluate the discharge characteristics of nonylphenol (NP) and octylphenol (OP) in the effluent of wastewater treatment facilities in the southern Gyeonggi-do. The detection rates of NP and OP were found to be 39.3% and 43.1%, respectively, with median values ranging from 1 to 3 μg/L across all industries. The industries that showed a detection rate of 50% or more were car wash, chemical experiment, fabric leather, paper wood, and plating facilities, with rates ranging from 50% to 75%, while other industries had detection rates of 21.7% to 36.8%. In terms of facility size, small-size establishments such as Type 4 and Type 5 showed higher detection rates in the "Na" region where somewhat relaxed standards are applied on a regional basis. This is because the proportion of Type 4 and Type 5 industries, including various concentration distributions of chemical experiments, research facilities, car washes, petrochemical, and plating industries, is higher than 77.7% overall and concentrated at a rate of 55.6% or higher in the “Na” region. Furthermore, the correlation coefficient (R) between NP and OP exhibited moderate association with values of 0.45 and 0.60 for car washes and plating industries, respectively. Chemical experiments, paper and wood, electrical and electronic, and medicine and hospital facilities showed strong association with correlation coefficients of 0.83, 0.82, 0.82, and 0.79, respectively. The findings in this study can be expected to serve as fundamental data for NP and OP in the establishment of water quality pollutants designation and discharge standards (draft) currently being pursued.