Abstract: In, for example, a gas-liquid, liquid/liquid exchange column, perforated tray assemblies are provided comprising a plurality of adjacent tray sections with slots adjacent rounded leading edges of the sections, and catches extending along trailing edges which interlock in the slots of an adjacent section. This interlocking avoids the use of bolted joints which cause stagnant areas where sediment accumulation occurs, resulting in reduced gas-liquid and liquid/liquid contact, and the need for the tray sections to be frequently cleaned. Perforated domes may be provided on perforations to reduce stagnant areas.