A Northwest Ohio manufacturing facility utilizes a controlled discharge lagoon system to treat a combination of sanitary and industrial wastewater. Depending on weather conditions and production rates, the lagoon system has been inconsistent at meeting the facility's NPDES Permit oil and grease limit of 10 mg/l.
The industrial portion of the wastewater that is pumped to the lagoon system consists of coolants or drawing fluids containing some amounts of free oils from the production process. The coolants consist of emulsified water-soluble oils used to lubricate the cutting and finishing process of the parts made at this facility. Due to this load of industrial oily wastewater, IFM proposed a dual bioaugmentation program that consistently fed oil and grease degrading bacteria (liquid) along with the supplemental treatment of dry bacteria into the lagoon system.
This combination has proved effective at improving all treatment aspects of the treatment system over the years. However, due to inclement weather and changes in production, oil and grease levels in the final lagoon have risen as high as 32 mg/l. To combat these problems, IFM began to monitor oil and grease levels from the primary and final lagoons monthly as a process control measure. Oil and grease results over the course of the year ranged from non-detectable to 20 mg/l.
IFM concluded that improved mixing and aeration would enhance the bioaugmentation program, leading to consistent NPDES Permit compliance. As an alternative to capital improvements, IFM also suggested that IFM's AOS 2008 (alternate oxygen source) be dosed into the lagoon along with a liquid bacterial culture. Also, to improve aeration, the facility modified the discharge pump to circulate in the final lagoon from the effluent end to the influent end of the lagoon.
This combination has proven effective with oil and grease, often creating non-detectable levels after this dosing and mixing treatment. This has become a standard operating procedure for the maintenance staff of the facility and has eliminated, to date, the necessity for further capital improvements to the lagoon system.