Which issue is least likely to arise from wastewater flows from commercial laundries and paper manufacturers?

The choice of trace metals as the issue least likely to arise from wastewater flows from commercial laundries and paper manufacturers is based on the typical characteristics of the effluents produced by these industries.

Commercial laundries primarily deal with water, detergents, and organic matter such as dirt and fabric fibers during washing processes. The predominant concern in their wastewater is usually the biological oxygen demand (BOD), which reflects the amount of organic material that needs to be broken down. Similarly, paper manufacturing involves the use of large amounts of water and can introduce fats, oils, and grease due to the processes of processing wood and pulp. These characteristics make BOD and fats, oils, and grease more significant concerns in the context of wastewater from these industries.

While pH can certainly be an issue due to the cleaning agents and processes being employed, trace metals are not a common challenge in these specific wastewater streams. These metals are more often associated with industries such as metal plating or mining, where the processes inherently involve the use or release of such metals into wastewater. Therefore, considering the nature of commercial laundries and paper manufacturing, trace metals are least likely to be a concern compared to the other issues listed.