Organic Pollution Index (OPI)
Uses and Limitation:
OPI is used to evaluate the polluted level of a watershed. It has been applied to several coastal and estuarine waters, for examples, Bohai Bay (Zou et al., 1983), Huanghua Port (Liu, 1993), Dalian Bay (Yang et al., 2001), Yangtze Delta (Quan et al., 2005), and Guangzhou Bay (Peng and Jia, 2007).
Son et al., (2020) used this index for Cau River of Vietnam.
Categorization Table
Based on the previous research done by Quan et al. (2005), the categorization is classified as follows:
Categorization Table
Based on the previous research done by Quan et al. (2005), the categorization is classified as follows:
Standards Required
Any national or international water quality standards could be used in this method.
Variables Selection
OPI is used to evaluate the polluted level of a watershed based on four parameters: COD, DO, concentration of dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphate (DIP).
Calculation of Organic Pollution Index:
The organic pollution index (OPI) is represented in the following equation:
\begin{eqnarray*}
A =\frac{COD}{COD_{s}} +\frac{DIN}{DIN_{s}} + \frac{DIP}{DIP_{s}}-\frac{DO}{DO_{s}}
\end{eqnarray*}
where COD is chemical oxygen demand; DIN is dissolved inorganic nitrogen; DIP is the dissolved inorganic phosphorus; DO is dissolved oxygen; CODS, DINS, DIPS and DOS are the standard concentrations as defined in Sea Water Quality Standard of China, GB 3097-1997 (State Bureau of Environmental Protection, 1998).
Case Studies based on Organic Pollution Index
Sources of pollution discharges and water quality samples at 27 stations in 2006 in the coastal waters of Hebei Province, western Bohai Sea, were analyzed by Liu et al., (2011). Pollutant loads from industrial sewages have shown stronger impact on the water environment than those from the general sewages. Analysis indicated that pollution of COD is mainly resulted from land-based point pollutant sources. For phosphate concentration, non-point source pollution from coastal ocean (fishing and harbor areas) plays an important role. To assess the water quality conditions, Organic Pollution Index and Eutrophication Index have been used to quantify the level of water pollution and eutrophication conditions. Results show that pollution was much heavier in the dry season than flood season in 2006. Based on COD and phosphate concentrations, results show that waters near Shahe River, Douhe River, Yanghe River, and Luanhe River were heavily polluted. Water quality in the Qinhuangdao area was better than those in the Tangshan and Cangzhou areas.
A combined water quality index (WQI) and pollution index (PI) to assess and characterize river water quality of Cau River which is one of the longest rivers in the north of Vietnam. Five different water quality and water pollution indices were used including the Water Quality Index (WQI), Comprehensive Pollution Index (CPI), Organic Pollution Index (OPI), Eutrophication Index (EI), and Trace Metal Pollution Index (TPI). The combined water pollution indices show more serious pollution towards the river downstream. In particular, CPI and OPI reveal a high
References
Liu, S., Lou, S., Kuang, C., Huang, W., Chen, W., Zhang, J. & Zhong, G. 2011. Water quality assessment by pollution index method in the coastal waters of Hebei Province in western Bohai Sea, China. Mar. Pollut. Bull. 62, 2220–2229.
Cao Truong Son, Nguyen Thị Huong Giang, Trieu Phuong Thao, Nguyen Hai Nui, Nguyen Thanh Lam, Vo Huu Cong; Assessment of Cau River water quality assessment using a combination of water quality and pollution indices. Journal of Water Supply: Research and Technology-Aqua 1 March 2020; 69 (2): 160–172. https://doi.org/10.2166/aqua.2020.122