The Cost of Grit Calculator draws on real-world data collected from operating plants to predict the likely savings to treatment plant efficiency that can be gained for any operator installing a high-performance grit removal system, using the guiding principles of Advanced Grit Management™.
The simple-to-use calculator requires input of a small number of values to generate, within minutes, an estimate of the annual and lifecycle savings that could be made by removing more grit at the headworks.
According to Keith Hutchings, Group Product Manager for Hydro International, the company's experience of working with wastewater treatment plants in North America and around the world has shown that operators are settling for very low percentage rates of grit removal efficiency – typically removing only 30-50% of incoming grit.
Hydro's Advanced Grit Management philosophy is based on removing between 85-95% of all grit entering the plant, he explains. Based on this target, the system can predict the estimated improvements to operating efficiency that result from removing much greater volumes of grit before it clogs tanks, basins and channels and abrades downstream process equipment.
Having set the operating plant capacity and the preferred equipment lifetime cost into the system, users can input estimated or known costs of their downstream plant maintenance activities. These include the periodic cleanout of grit basins, aeration basins, or anaerobic digester tanks, for example, as well as replacement and refurbishment costs for equipment such as pumps, centrifuges or membranes.
Where operators are unable to provide values, averages are suggested based on actual costs from operating plants in the USA.
“Every plant is different, so the calculator is no substitute for a detailed site assessment of real-world grit concentration and behavior, and actual sampling of incoming effluent prior to a detailed plant design,” adds Hutchings. “However, our research shows that poor grit removal is a major source of avoidable process inefficiency, operating, maintenance and replacement costs."
Hydro hopes the tool will help designers and operators to simply demonstrate the benefits for improved grit removal and help to justify optimum capital and operating cost decisions. The company says there is no need to continue with cumbersome and costly tank clear-outs or to budget for frequent equipment replacement.
The Advanced Grit Management philosophy is based on using Hydro International’s HeadCell® grit removal system currently being introduced in the UK, having been developed and refined during more than 30 years of operation. The HeadCell can be combined with Hydro’s GritCup® washer and classifier and SpiraSnail® dewatering system to achieve the best possible results.
