. 2021 Nov 26;18(23):12481. doi: 10.3390/ijerph182312481

Table 1.

Calculation equations of discharge coefficient method.

Pollution Sources	Formula	Symbols and Units	Remarks
Rural living sources	$G_{p} = 365 \times N S_{p} \times 10^{- 10}$	Where G_p represents some kind of pollution emission (10,000 tons/year); N represents Number of permanent residents (one person); S_p represents discharge coefficient of pollutants (g/day·person)	The pollution loads of COD, TN, TP, and N-NH4⁺ are calculated by the same formula.
Agricultural source	$P = \sum (A_{N} F_{N} + A_{P} F_{P}) / 10^{4}$	Where P represents a load of a certain pollutant (10,000 tons/year); A_N, A_P represents the amount of Nitrogen and Phosphorus fertilizer applied in farmland (Tons/Year); F_N, F_P represents loss Coefficient of Nitrogen and Phosphate Fertilizer (%)
Livestock and poultry breeding source	$M = \sum C_{i} P_{i} \times 365 / 10^{7}$	Where M represents the discharge of certain pollutants (10,000 tons/year); C_i represents the total number of animals of type i (one head); P_i represents type i animal emission factor (kg/head (only)····day)
Aquaculture source	$M_{N} = (C \times N_{f} - N_{b}) \times 10^{3}$ $M_{P} = (C \times P_{f} - P_{b}) \times 10^{3}$	MN, MP Represents nitrogen load and phosphorus load (kg/ton) respectively; C is the bait coefficient; N_f, P_f represents the percentage of nitrogen and phosphorus in the bait respectively; N_b, P_b represents the content percentage of nitrogen and phosphorus in cultured fishery products respectively	Applicable to the calculation of TN and TP pollution load