Their removal prior to the treatment might be necessary if they are present in
high concentration (>400 mg/L) to prevent the negative effect on
the treatment process. On the other hand, photolysis of nitrate in
the absence of H2O2 would lead to the generation of HO•. However,
when H2O2 is added, nitrate acts as an inner filter and reduces the
process efficiency [33]. This effect will be evident only when the
nitrate is present at high concentration (>10 mg/L).