A method of HCN removal from syngas including treating a hot syngas stream for conversion to chemical products by removing various components from the hot syngas stream by: passing the hot syngas stream to a scrubber; adding aldehyde to a circulating scrubber water; capturing ammonia and HCN in the circulating scrubber water and condensing water from the hot syngas stream into the circulating scrubber water; withdrawing a scrubber waste water effluent from the scrubber comprising absorbed ammonia, ammonium, and absorbed HCN, and glycol nitriles, formed from the reaction of the aldehydes with HCN, from the scrubber; withdrawing a treated syngas stream effluent from the scrubber having a reduced concentration of ammonia and HCN; and, passing at least a portion of the scrubber waste water effluent stream to a biological treatment zone for the removal of ammonia, absorbed HCN, and glycol nitriles.