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Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China

1
Environmental standards Institution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
2
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 2019, 11(12), 2475; https://doi.org/10.3390/w11122475
Received: 8 September 2019 / Revised: 19 November 2019 / Accepted: 21 November 2019 / Published: 24 November 2019
(This article belongs to the Section Water and Wastewater Treatment)
Most guidelines for urban wastewater treatment plants (WWTPs) are established on a time basis determination to determine performance and compliance with discharge standards and limits (i.e., maximum daily-average). Nevertheless, there is a lack of a systematic analysis of the relationship between instant sampling and daily average discharge concentration values. The present study used the chemical oxygen demand (COD) automated monitoring data that were collected from 1738 WWTPs in China to discuss the relationship between instant sampling and daily average values. A ratio model (K value) was developed to study the relationship between the reliability of the instant sampling value and the daily average limit for the COD measurements. The K value revealed that the ratio of COD instant and daily average measured concentrations for WWTPs in China collectively ranged from 1.00 to 1.45. The results of this study suggest setting the K value of COD to 1.3 for WWTPs in China to estimate the corresponding instant sampling limit of COD, as well as for most WWTPs in China, in order to ensure the stability of compliance to the daily average limits. The instant sampling value of COD in 24 h should be controlled no more than five times out of the instant sampling limit, which is 1.3 times of the daily average limit.
Keywords: discharge standards; limits; instant sampling; daily average; COD; urban wastewater treatment plants; compliance; monitoring discharge standards; limits; instant sampling; daily average; COD; urban wastewater treatment plants; compliance; monitoring
MDPI and ACS Style

Zhou, Y.; Lei, J.; Zhang, Y.; Zhu, J.; Wu, Y.; Fang, H. Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China. Water 2019, 11, 2475.

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