Effluent from vehicle and equipment cleaning is known to contain a variety of potential pollutants, the most common being hydrocarbons and suspended solids. Proper treatment and discharge of this effluent is a growing concern as environmental awareness increases. In the United States, discharge of this effluent to municipal sewage treatment systems requires a permit from local authorities, discharge to surface waters requires a federal permit and, in most cases, discharge to the ground is prohibited. Furthermore, discharge to ground and surface waters can cause soil or groundwater contamination resulting in property devaluation, adverse impact on human health, fines from regulatory agencies, expensive cleanup and negative publicity.

Effluent from vehicle washing typically does not meet the minimum pollutant levels allowed by regulatory agencies for discharge to surface waters or sewage treatment plants. Because of the liability associated with discharge to ground and surface waters and the difficulty in meeting municipal sewer discharge permit requirements, closed-loop wastewater treatment is an attractive alternative to discharge. Closed-loop systems, which recycle wash water, eliminate the need for discharge permits and significantly reduce environmental exposure and risk. A Schlumberger field test was conducted to determine feasibility of this concept and to evaluate and compare several closed-loop systems. As part of the field test, 13 closed-loop treatment systems and 2 pretreatment systems were installed in field shops over a 2-year period. The systems are divided into three different treatment categories based on the primary treatment technology employed (mechanical, chemical and biological).

Evaluation and comparison of systems from each category constitute the basis of this paper. Factors involved in selecting a system and available water-treatment technologies are discussed. The conclusion summarizes the results of the system comparison and makes recommendations for selecting and installing closed-loop water treatment systems for vehicle and equipment cleaning.

You can access this article if you purchase or spend a download.