3.3.3. pH and ORP

Figure 4 shows the changes of oxidation-reduction potential (ORP) and water pH in the microcosm during the operation. The data of changes of electrical conductivity (EC), pH, dissolved oxygen (DO), and oxidation-reduction potential (ORP) are also shown in Tables S1–S4. Higher pH values and lower ORP in columns capped with materials were attained as compared to the one without caps. However, the differences tended to be slight during the later stage.

**Figure 4.** The changes of oxidation-reduction potential (ORP) and water pH values in microcosm during the operation.
