BALANCING TREATMENT PROCESS REQUIREMENTS AND ENERGY MANAGEMENT

In October 2007, the Water Environment Federation (WET, 2007) reported that the “…60,000 water and 15,000 wastewater systems in the United States account for as much as 35% of municipal energy usage and 3% of the nations electric load”. In addition to the energy loads at these facilities, permit requirements have lead to utilities investigating treatment process requirements to maximize the facilities capacities, while minimizing operation and maintenance (O&M) costs. Aeration required for treatment, in-plant and effluent pumping and solids processing account from most of the energy used in a wastewater treatment facility (WWTF).Today, utilities large and small are under intense pressure to provide better service, accommodate growth with fewer staff, and meet more stringent regulations, while minimizing the financial impact on their rate payers and providing greater accountability on all fronts. Complicating the matter, these facilities must be able to treat flows for nearly all conditions, integrating new processes and technologies. Like many utilities in the state of Florida, addressing these issues through process control, energy management, and reclaimed water reuse are priority issues to meet the demands of today's utility environment. A number of utilities in Florida have integrated process control management and technology into their designs to not only meet their permit conditions, but also minimize the energy requirements at their facilities.Many facilities can operate their facilities at higher capacities than originally thought, or be retrofitted with newer technology cost effectively. Optimization of wastewater treatment processes requires not only a science based assessment of the wastewater flows and process performances, but also operations trust in “big picture” thinking and engineering skills. Additionally, many utilities have implemented controls to manage aeration for process control and pumping requirements associated with process and energy management.This paper discusses the work at a number of utilities in Florida that are continually evaluating technological solutions that improve the environmental performance of its processes. In addition, it discusses the importance of process modeling as a means to optimize the wastewater treatment process. These utilities have done a significant amount of research and to optimize their wastewater treatment processes, and as such, they have implemented process controls to mange and optimize the energy used in the wastewater treatment process, biosolids management and reclaimed water reuse. The process controls include such control mechanisms as continuous monitoring of dissolved oxygen (DO) and more complex parameters (e.g., nutrients, ORP, etc.) for aeration control to optimize the biological nutrient removal processes.The work that these utilities have done, does not stop at the treatment process, they have instituted programs to reuse a significant amount of the wastewater effluent for public access reclaimed water uses, whether it is used within a residential development, on a golf course, or used to irrigate agricultural fields or farms. Additionally, these utilities have developed programs to beneficially reuse the biosolids generated as a result of the treatment process, whether it is the methane generated from the treatment process to supplement energy requirements or the production of a product that is used as a fertilizer.