The implementation of data reconciliation for evaluating a full-scale petrochemical wastewater treatment plant.

Abstract

Data reconciliation and mass balance analysis were conducted for the first time to improve the data obtained from a petrochemical wastewater treatment plant (WWTP), and the results were applied to evaluate the performance of the plant. Daily average values for 209آ days from the inlet and outlet of the plant obtained from WWTP documentation center along with the results of four sampling runs in this work were used for data reconciliation and performance evaluation of the plant. Results showed that standard deviation and relative errors in the balanced data of each measurement decreased, especially for the process wastewater from 24.5 to 8.6آ % for flow and 24.5 to 1.5آ % for chemical oxygen demand (COD). The errors of measured data were -137آ m3/day (-4.41آ %) and 281آ kg/day (7.92آ %) for flow and COD, respectively. According to the balanced data, the removal rates of COD and 5-day biological oxygen demand (BOD5) through the aeration unit were equal to 37 and 46آ %, respectively. In addition, the COD and BOD5 concentrations were reduced by about 61.9آ % (2137آ kg/day) and 78.1آ % (1976آ kg/day), respectively, prior to the biological process. At the same time, the removal rates of benzene, toluene, and styrene were 56, 38, and 69آ %, respectively. The results revealed that about 40آ % of influent benzene (75.5آ kg/day) is emitted to the ambient air at the overhead of the equalization basin. It can be concluded that the volatilization of organic compounds is the basic mechanism for the removal of volatile organic compounds (VOCs) and it corresponds to the main part of total COD removal from the WWTP.