Approaches for Quantifying the Attenuation of Wastewater-Derived Contaminants in the Aquatic Environment

The effluent from municipal wastewater treatment plants contains trace concentrations of a variety of organic compounds. To assess the removal of these compounds in full-scale treatment systems and effluent-receiving waters, approaches are needed for quantifying removal rates and mechanisms. For processes that result in near complete removal of wastewater-derived contaminants, it is reasonable to measure concentrations entering and leaving the treatment system. However, for those compounds that are not completely removed, alternative methods are needed. This paper describes several examples of approaches that combine laboratory and field studies to assess the attenuation of wastewater-derived contaminants

The power of one reinforcer.

Animal trainers use shaping to teach many behaviors. However, during shaping, the organism may engage in behaviors other than the target behavior or approximations to the target behavior. If the animal is engaged in other behaviors, the rate of reinforcement may decrease and the trainer may resort to what is sometimes referred to as a "desperation click." That is, the trainer delivers one reinforcer for a behavior that is not a successive approximation to the target response. Anecdotal reports from trainers suggest that sometimes the animal continues to repeat this other behavior that received only one reinforcer, even in the absence of further reinforcement for that behavior. This study compared whether, during a one minute extinction period, participants spent more time engaged in a behavior that had been reinforced only once after a brief period of no reinforcement or in a behavior that had been reinforced multiple times. Participants, who were university students, played a tabletop game that involved touching and manipulating small objects. Five conditions were repeated twice for each participant: reinforcement for interacting with a training object alone, reinforcement for interacting with a training object with other objects present, reinforcement for interacting with a target object, one reinforcer for interacting with a third object immediately following a brief period of no reinforcement, and reinforcement for interacting with any object. Results from this study show that a desperation click situation can be reliably produced in a controlled setting. When participants received one reinforcer for interacting with a new object following a period of no reinforcement, they interacted with the new object for a longer or equal amount of time as compared to an object that had a history of reinforcement