For many industries throughout the United States, the contamination of wastewater by the infiltration of oil and grease is a problem that must be dealt with before state and federal regulatory compliance can be achieved. Untreated oil and grease in wastewater discharges can result in potential safety hazards, as well as damage to downstream wastewater treatment equipment. Varying strategies can be employed to prevent these problems. These schemes may include biological additives, chemical additives (such as surfactants or solvents) and mechanical skimmers. However, a proven method commonly used in the presence of oils and suspended solids, is a device known as an API oil-water separator, which has been used since the early 1930’s.

Oil-water separators are devices that separate oils and grease (and suspended solids) from a variety of wastewater discharges. Many separators are designed according to standards published by the American Petroleum Institute, even though some of these same principals can be used when designing separators for the food processing industry. In their most basic form, oil-water separators are rectangular tanks with lengthy retention times, and designed based on the specific gravity difference between the oils and the wastewater. Once separation has occurred, the top oil-layer is skimmed off, the bottom solids-layer is removed by a chain and flight scraper (or can be removed when the system is drained for maintenance) and the middle water-layer is removed and further treated. When available space is a concern, a parallel plate separator can significantly reduce the required area needed by the conventional API separator. This design uses parallel plates tilted at approximately 45 degrees, allowing smaller oil droplets to combine and rise more quickly, enhancing separation efficiency.

August Mack Environmental has managed the installation of oil-water separation systems for clients within a variety of industries. Most recently, a facility in Greensburg, Indiana solicited August Mack’s services to determine what method of oil-water separation would best meet their needs. Consultation with the client revealed that under previous facility ownership, oily sludge contamination had resulted in the facility’s sub-structure. Analysis of the site conditions indicated that wastewater discharges from several basement sump units contained levels of oil that were unacceptable for discharge to a Publicly Owned Treatment Works (POTW).

The challenge facing August Mack personnel was to design a system of oil-water separation that would effectively address the contamination, while also proving cost effective for the client. Several factors were considered during the design process. The factors contemplated included the extent of the oil contamination, the dispersion of the oil in the water, the estimated system retention time, and the cost of the system. Although the level of oil contamination was significant enough to warrant a separation system, the extent of the oil contamination was not severe. Nevertheless, the degraded and dispersed condition of the oil presented a separation challenge. The use of coalescing media (a suitable surface for oil droplets to meet and grow into larger droplets, thus increasing droplet buoyancy) would be necessary to prevent highly dispersed oil from passing through the system. Taking these conditions into account, August Mack successfully designed and installed a separation system utilizing a chamber for removal of solids and a second chamber in which a coalescing media would increase the system’s separation efficiency. Expertise, commitment to quality, and recognition of the client’s specific needs allowed August Mack to provide a cost-effective and thorough solution.

For facilities where oil is present in wastewater discharges, oil-water separators have proven to be cost effective solutions. Identifying the appropriate technologies for site-specific conditions, however, can pose a challenge. Overcoming that challenge is as simple as seeking an ally with the proper expertise and commitment to quality. August Mack is a valuable resource that can provide customized solutions to the challenges of industrial oil-water separation.