Pengolahan Limbah Cair Laboratorium Bekas Pengujian Kebutuhan Oksigen Kimiawi (KOK) dengan Metode Presipitasi

Abstract

Determination of chemical oxygen demand (COD) parameter in water samples produce laboratory waste which are still harmful to be dumped to the environment. It is because COD testing still use several reagents containing heavy metals such as Ag, Cr, and Hg. This research was focused on Hg removal, because of its higher toxicity compared with the two others. The initial COD waste contained 5241.4 mg/L of Hg, whereas the quality standard of Hg according to PP No. 82/2001 is 0.002 mg/L. Precipitation method was studied in this research to treat this COD waste, especially to reduce the Hg content. The precipitation was carried out with hydroxide and carbonate. From several methods tested, 5 of which decreased significant amount of Hg, which were hydroxide precipitation with acid addition (HA), multilevel hydroxide precipitation (HB), carbonate precipitation with addition of hydroxide and acid (KHA), multilevel hydroxide precipitation with acid addition (HBA), and multilevel hydroxide precipitation with addition of salt and acid (HBGA). Those five methods could decrease the Hg content up to 99.96%, into 2.1939, 2.7513, 2.0185, 2.5858, and 2.1683 mg/L, respectively. However these results had not yet fulfilled the quality standard