Statistical analysis technique was applied to operating parameters and removal efficiency data sets obtained from advanced wastewater treatment plant during 1 year. Through factor analysis three factors derived varimax rotation were selected each plant. Three components explained 96%, 87% of the total variance of the process, respectively. The components on A2O plant were identified in the following order：1) Shortening the SRT during high-flow period, 2) Keeping biomass high on winter 3) factor was related to DO. On DNR plant, we defined them as follows: factor 1, Prolonged the SRT during high-flow period; factor 2 was related to sludge return; factor 3, Influent BOD during low-DO period. This technique was believed to assist operators in identifying priorities to improve operation efficiency.

We investigated and analysed the actual conditions and characteristics of railroad noise levels for 17 sites in the vicinity of the Seoul-Pusan Line. The results are summarized. as follows : 1) Railroad noise level ranged to 64∼74 L_eq dB(A) at day time and ranged to 60∼72 L_eq dB(A) at night time. 2) Increased night noise level depend on the increase of trains passing at night time. 3) The major factor of increased noise level in the vicinity of stations are using loudspeakers and stream whistle on trains. 4) Decreased effect of noise according to distance is able to be described quantitatively using regression equations of multiplicative model. L_eq=78.59 X^-0.056 n=25, r=-0.994, s.e.=1.007 P_av =105.68X^-0073, n =25, r =-0.997, s.e. = 1.007 Also increased and decreased effect of noise according to floor in apartment is able to be described quantitatively using regression equations of multiplicative model. L_eq = 64.238 X^0.0567, n = 39, r = 0.787, s. e. = 1.004 P_av. = 79.963 X^0.0254 n = 39, r = 0.689, s. e. = 1.056 5) Average noise level in high floor is over 70L_eq dB(A) at day and night time, so more detailed soundproofing countermeasured in high floors apartment is required.