How to calculate the amount of citric acid to neutralise the pH within wastewater?
Gotta start with my favorite formula:
$$Q = CV$$

$$C_\textrm{eff}V_\textrm{eff}+C_\textrm{acid}V_\textrm{acid} = C_\textrm{out}V_\textrm{out}$$

$$(10^{-10.5}~\mathrm{mol/L})(10^5~\mathrm{L})+(10^{-2.2}~\mathrm{mol/L})V_\textrm{acid} = (10^{-7}~\mathrm{mol/L})(10^5+V_\textrm{acid})$$

$$V_\textrm{acid} = 1.51~\textrm{L}$$