Fate of cyanide and related compounds in aerobic microbial systems-I. Chemical reaction with substrate and physical removal

Abstract

The chemical reaction of cyanide with substrate was investigated in sealed glass ampoules using glucose as substrate and inorganic buffers. The reaction was found to be pseudo-first order and pH dependent, with an optimum pH near 11.0. The cyanide-glucose reaction products were found to be biodegradable by both acclimated and unacclimated heterogeneous cultures in shake flask and BOD bottle systems.Adsorption onto microbial solids was investigated using sealed, stirred glass reactors containing bacteria and potassium cyanide in water buffered at pH 7.0 with inorganic buffers. Very little adsorption occurred on a starved non-flocculating pure culture of Bacillus meqaterium, although up to 15% adsorption occurred in systems containing a stirred flocculent heterogeneous culture.Stripping was investigated from a starved heterogeneous culture in an aerated microfermenter at neutral pH. Hydrogen cyanide and carbon dioxide in the off-gas were trapped in sodium hydroxide solution, separated and analyzed. Stripping removed up to 80% of original cyanide, and tests using K14CN revealed that a small amount of cyanide had been metabolized.