USS Chemical's Houston plant produces ethylene from an ethane rich refinery gas by steam cracking. Prior to 1979, the plant discharged roughly 300 to 500 gpm of effluent to the Houston Ship Channel. The construction of a maximum recycle sidestream softening system began in 1977 for the treatment of wastewater from the plant. The system is composed of two lime softening units that treat the blowdown from the cooling water system. The softeners remove the calcium, magnesium, silica, and carbonate ions. Softened water is processed through a recarbonator and filter for return to the cooling water system. Carbon dioxide is used to control pH in the cooling water system instead of sulfuric acid. Polymaleic anhydride polymers mechanistically prevented scale formation by fluidizing small crystals rather than inhibiting crystals rather than inhibiting crystal formation