Wastewater

In 2019, the City of East Peoria, IL, began a comprehensive modernization of its wastewater infrastructure, including a $68 million upgrade covering two operating facilities, Wastewater Treatment Plant No. 1 and Wastewater Treatment Plant No. 3. The project addressed aging equipment, regulatory pressure and the need for improved process control.

The ideal blower control matches the blower airflow to the process demand. The process demand, in turn, must be established by the aeration control system. This control strategy has become standard practice in most treatment facilities because of its proven effectiveness in reducing energy consumption and improving process stability.

The wastewater treatment plant for the City of Lafayette, Colorado, is a Class B biosolids facility. It meets grid regulations for volatiles reduction with at least a 38% reduction, and has a solids retention time (SRT) of at least 15 days at 95°F (35°C). Class B biosolids can be used as fertilizer for livestock feed and other applications that don’t directly lead to food for human consumption. 

Many designers and operators believe that multistage centrifugal blowers are not suitable for variable speed control. They also feel that multistage centrifugal blowers are an inefficient option for wastewater aeration. Implementing VFD control of their aeration blowers allowed the plant to improve energy efficiency. The reduction in energy expense paid for the system upgrade in less than two years.

Derby Sewage Treatment Works handles wastewater for a population of 440,000, processing an average of 1’000 liters and a maximum 2,300 liters of effluent every second. After water has passed the inlet and mechanical screens, it gravitates into the primary settlement tanks, where solids settle as sludge at the bottom. The sludge is drawn off and anaerobically digested to produce renewable fuel, but liquid flows onto the activated sludge plant.

High levels of reliability can be achieved in two ways. First, by design – employing quality materials, proven components, and simplified mechanisms. Second, by incorporating advanced monitoring techniques that identify abnormal operating conditions, provide notification to operators, and initiate equipment shutdown before catastrophic failure occurs. Modern positive displacement (PD) blower packages use both techniques to improve system reliability.

When a facility plans for a wastewater treatment plants, they typically design based on population and industry growth twenty to thirty years into the future. Regulatory requirements often dictate designing the activated sludge process equipment based on future-state influent flow and loading conditions, resulting in decades of constrained, inefficient, and suboptimal operation. 

The objective of this article is to look at typical industrial wastewater agitation processes and share various energy saving compressed air/blower projects that have worked well over the years. These basic fundamentals are a good starting point to begin the evaluation of a project idea. There are three primary uses of compressed air in all wastewater treatment applications. This article will focus on agitation and movement of materials.

Supplying air to process equipment necessitates a system approach. Selecting the blowers is a critical design step, but far from the final one. The layout of the blower room and ancillary equipment is just as critical to project success as the blowers themselves.

Single-stage centrifugal blowers are a proven technology that have been around for many years and will probably be here for many years to come. A well maintained machine can last for decades and will likely outlast its original control system. Even if the control system is still in good working order the components might already be end of life and hard to replace if any of them fail. If you are thinking about modernizing the hardware (PLC / HMI / Instruments) this is also a great opportunity to make the system a little smarter and user friendly.