3. Results and discussion
3.1. Chemical precipitation of brining wastewater
Given that the brining wastewater inherently contained
lots of soluble magnesium, chemical precipitation
to induce the precipitation of magnesium hydroxide was
attempted by raising the pH of the wastewater through
the addition of sodium hydroxide. It was known that the
precipitation of magnesium hydroxide during limesoftening
processes was effective for the removal of
viruses [4], color [5], organic matters [6,7], and so on.
The optimal dosage of sodium hydroxide was established
by the jar-test experiment. Taking into account
the characteristics of the food product, the application
of polymeric or inorganic coagulants was discounted.
The results of the jar-test experiment are summarized
in Fig. 3. Removal of TOC, SS, turbidity and the amount
of sediment volume increased as the NaOH doseincreased. But the recovery of soluble magnesium,
which was known to be a critical component in the delicate
taste of Kimchi and thus desired to get back as much
as possible, did not change vary much. The optimal dosage
of NaOH was estimated to be about 14 ml of 2 M
NaOH per liter of the brining wastewater, although it
was quite difficult to determine the precise optimal dosage