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Open AccessArticle

COD Discharge Limits for Urban Wastewater Treatment Plants in China Based on Statistical Methods

by Yuhua Zhou 1,2,*, Ning Duan 1,2, Xuefang Wu 2 and Hao Fang 3
1
College of Water Sciences, Beijing Normal University, Beijing 100875, China
2
Environmental Standards Institution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
3
Beijing Municipal Research Institute of Environmental Protection, State Environmental Protection and Industrial Wastewater Pollution Control Engineering and Technology (Beijing) Center, Beijing 100037, China
*
Author to whom correspondence should be addressed.
Water 2018, 10(6), 777; https://doi.org/10.3390/w10060777
Received: 18 May 2018 / Revised: 5 June 2018 / Accepted: 11 June 2018 / Published: 13 June 2018
(This article belongs to the Section Water and Wastewater Treatment)
Discharge standards are among the most important regulations to control pollutants discharged from industries and domestic uses. China has made great efforts to build up its discharge standard system and develop methods to derive limits. However, there is still a lack of systematic analysis of measured data and derivation of discharge limits based on statistical methods. The present study, taking chemical oxygen demand (COD) discharge limits of urban wastewater treatment plants (WWTPs) as an example, reviews the history of discharge standards of WWTPs in China and analyzes the statistical distributions of COD concentrations from 1753 WWTPs. Based on the lognormal distribution, three factors—geographic location, treatment process, and ratio of treated wastewater from industries—were found to be significantly correlated with logarithmic COD concentrations via a regression model and long-term averages of WWTPs were derived. Daily maximum variability factors for WWTPs based on the 99th percentile of the distribution of daily measurements and the discharge limits for WWTPs were also derived by multiplying long-term averages by variability factors. This study develops, for the first time in China, discharge limits based on statistical methods. The results may inform special discharge limit settings for different types of WWTPs. View Full-Text
Keywords: COD; discharge standards; limits; statistical methods; urban wastewater treatment plants COD; discharge standards; limits; statistical methods; urban wastewater treatment plants
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Zhou, Y.; Duan, N.; Wu, X.; Fang, H. COD Discharge Limits for Urban Wastewater Treatment Plants in China Based on Statistical Methods. Water 2018, 10, 777.

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