There are 4 typical alternatives:

1) select a buffer with convenient buffering capacity;

2) employ a commercially available pH controllers, e.g. those use for fermentors.

3) select the right type of ion-exchange membrane that will "drain" the OH- or H+ from the compartment of interest, at a convenient rate.

4) modulate appropriately the applied current. more current will produce more acid or base conditions.

Thank you so much for your information.