OPTIMIZING THICKENING AND DEWATERING THROUGH AUTOMATION WERF

Automation in the wastewater treatment industry is advancing rapidly. Industries and agencies are complying with stricter regulations and performing more tasks with less staff. Automation provides an opportunity to overcome the regulation and staffing hurdles. The automation trend is just reaching the thickening and dewatering processes that are employed at practically every wastewater treatment facility. These processes have routinely been operated with “semiautomatic” controls because of the inherent variations of the feed and the lack of reliable instrumentation. This research on automated thickening and dewatering involved performing long-term operational tests on automation packages and instruments to determine the potential for fully automated operation. This research has been funded by the Water Environment Research Foundation with funding from the U.S. Environmental Protection Agency.The four agencies where this research was completed each had very difficult sludge to dewater or thicken. Even with this, the instruments and control systems showed the operators optimum operational parameters that resulted in some improvement, i.e., reduced polymer dosage, improved capture, and/or more consistent cake and centrate/filtrate. The instrumentation also allowed the discovery of many problems with the existing systems of which the plant staff was not aware.The required cleaning of the probes, unclogging of sample lines, plus the required operator attention to the systems made the control systems more of a problem for the operators of these systems then the value they perceived from them. As a result the research team had to continually push to get the systems put back in automatic. Consequently, although installed at little or no cost to the agencies, all of them chose not to purchase the equipment and make these permanent installations.Results from the research lead to recommendations for new thickening and dewatering systems. These include: applicability of solids concentration instruments, instrumentation installation recommendations, and control system applicability. Further research of new systems and a system being developed in the Netherlands is recommended.