Impact of Boron Discharge Standard at Automotive Engine Plant

DaimlerChrysler's engine manufacturing plant in Trenton, Michigan was faced with regulation of boron in its wastewater effluent as a result of a boron limit in the local sewer authority's new NPDES permit. After determining that the major source of boron in the engine manufacturing wastewater was from machining coolants, DaimlerChrylser embarked on an evaluation to determine the best method to control boron concentrations in its wastewater effluent. DaimlerChrysler evaluated product substitution as well as enhanced wastewater treatment for boron removal. Based on successful trials using nonboron containing coolants, and expected high costs associated with removal of boron from the wastewater effluent, DaimlerChrysler eliminated its use of coolants containing boron, and wastewater effluent boron concentrations were significantly reduced as a result. However, the new coolants had higher concentrations of oxygen-demanding compounds and nitrogen, which over-taxed DaimlerChrysler's on-site wastewater pretreatment plant. Capital upgrades and modified operating procedures were required to provide necessary treatment capacity and reliable performance. This paper describes the impacts of production changes on wastewater characteristics, details of the capital upgrades and modified operating procedures, and overall project delivery process. Operating data are presented to illustrate the benefits of the capital upgrades and operating procedures on overall wastewater pretreatment plant performance.