NOVELTY - Method (I) of treating hot syngas stream (11) comprises: passing hot syngas stream to scrubber (14); adding acidic solution comprising purge water (13) to circulate scrubber water; capturing ammonia, carbonyl sulfide and particulates in circulating scrubber water and condensing water; withdrawing scrubber waste water effluent from scrubber comprising absorbed carbonyl sulfide, ammonia and particulates; withdrawing treated syngas stream effluent from scrubber having reduced concentration of carbonyl sulfide, ammonia and particulates; and converting treated syngas stream to chemical products.    USE - The methods are useful for treating hot syngas stream for conversion to chemical products by removing particulates, ammonia and carbonyl sulfide from the hot syngas stream (claimed), which is useful in production of biofuels used as liquid motor fuels or for blending with conventional gasoline or diesel motor fuels.    ADVANTAGE - The methods: remove ammonia, carbonyl sulfide, hydrogen cyanide and some polishing of particulates from syngas in a cost effective and environmentally benign and sustainable fashion, with the need for little to no chemical addition; and prevent the build up of secondary metabolites and dissolved solids.    DETAILED DESCRIPTION - Method (I) of treating a hot syngas stream (11) for conversion to chemical products by removing particulates, ammonia and carbonyl sulfide from the hot syngas stream comprises: (a) passing the hot syngas stream to a scrubber (14); adding an acidic solution comprising a purge water (13) to a circulating scrubber water; (b) capturing ammonia, carbonyl sulfide and particulates in the circulating scrubber water and condensing water from the hot syngas stream into the circulating scrubber water; (c) withdrawing a scrubber waste water effluent from the scrubber comprising absorbed carbonyl sulfide, ammonia and particulates; (d) withdrawing a treated syngas stream effluent from the scrubber having a reduced concentration of carbonyl sulfide, ammonia and particulates; and (e) converting the treated syngas stream to chemical products in a process that produces at least a portion of the purge water. INDEPENDENT CLAIMS are also included for:    (1) method (II) of treating hot syngas stream for conversion to chemical products by removing particulates, ammonia and carbonyl sulfide from the hot syngas stream comprising: steps (a)-(d); and (f) passing at least a portion of the scrubber waste water effluent stream to a biological treatment zone for the removal of ammonia and absorbed carbonyl sulfide to produce a biologically treated waste water effluent; and    (2) method (III) of treating hot syngas stream for conversion to chemical products by removing particulates, ammonia, carbonyl sulfide and hydrogen cyanide from the hot syngas stream comprising: steps (a)-(b); step (c), where the scrubber comprises absorbed carbonyl sulfide, ammonia, ammonium and particulates from the scrubber; step (d), where the scrubber comprises hydrogen cyanide and a reduced concentration of carbonyl sulfide, ammonia and particulates; (g) passing the treated syngas stream effluent to a hydrogen cyanide scrubber and contacting it with a hydrogen cyanide scrubbing water stream to capture the hydrogen cyanide and to produce a hydrogen cyanide scrubbing water effluent and a hydrogen cyanide scrubber syngas stream; (h) passing at least a portion of the scrubber waste water effluent and the hydrogen cyanide scrubbing water stream to an anoxic biological treatment step for the partial conversion of nitrate formed from ammonia, and ammonium into nitrogen gas and for the at least partial conversion of carbonyl sulfide to primarily carbon dioxide and hydrogen sulfide, and hydrogen cyanide into carbon dioxide and ammonia to produce an anoxic effluent stream; (i) passing at least a portion of the anoxic effluent stream to an aerobic biological treatment step for the nitrification of ammonium to nitrates; (j) recovering a biologically treated waste water stream from the aerobic biological treatment step; (k) passing a portion of the biologically treated waste water stream to the anoxic biological treatment step; and (l) passing a portion of the biologically treated waste water stream to the hydrogen cyanide scrubber as at least part of the hydrogen cyanide scrubbing water stream.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram showing the steps of the method of treating hot syngas stream for conversion to chemical products by removing particulates, as carried out by a syngas conversion system run.    Stream of hot syngas (11)    Cyclone separator (12)    Purge water (13)    Venturi type scrubber (14)    Separator (16)