Locomotive Engine Rebuild Wastewater Proves No Match for Ultrafiltration

Wastewater generated from a locomotive engine remanufacturing facility is currently pretreated and discharged to the municipal sewer system. Process wastewater generated at the facility contains high concentrations of oils and soluble metals. The sewer authority advised the railroad company that stringent metals limits may soon be enforced as a result of modifications to the authority’s NPDES discharge permit. In anticipation of the new limits, the company embarked on a program to improve their wastewater pretreatment system, including evaluation of alternate treatment technologies such as ultrafiltration.A three-month pilot study was conducted at the facility to evaluate the performance and long-term operating considerations for two wastewater streams: effluent from an existing oil/water separator, and clarifier effluent after chemical emulsion-breaking and gravity separation. The pilot trials demonstrated that ultrafiltration technology provides superior effluent quality compared to the facility’s existing pretreatment system, with complete removal of suspended solids, emulsified oil and grease, and precipitated metals. High concentrations of emulsified oil and grease and metals in the facility’s oil/water separator effluent were readily removed by the ultrafiltration test unit. This paper presents the pilot study experimental design and performance data, including design considerations for the full-scale ultrafiltration system.