Glossary of Compressed Air Terms :: Z :: Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ZDDP an antiwear additive found in many types of hydraulic and lubricating fluids. Zinc dialkyldithiophosphate. Zero The temperature of pure melting ice under standard atmospheric pressure on the Centigrage and Réaumur scales. Zero discharge water A discharge limit applied to manufacturing and commercial establishments in which only normal human sanitary wastewaters may be discharged to the municipal sewerage system. All other types of wastewater, such as that water used in manufacturing processes, are not included in zero discharge water; these wastewaters must be recycled, and the resulting waste products must be taken to an alternate and approved disposal facility.