DENITRIFICATION FILTERS: A COMPARISON OF MANUFACTURERS AND REVIEW OF PERFORMANCE, PATENT AND BIDDING ISSUES

With the development of total maximum daily loads for nutrient discharges to address water quality concerns, many wastewater treatment plants are facing stringent nutrient limits. Deepbed denitrification filters are a well-proven technology for meeting low total nitrogen limits. Concurrent denitrification and solids removal in a deep-bed filter was first patented in 1973, and then followed by a series of patents for other components including the use of backwash water to release nitrogen gas. Dravo Corporation, and later Tetra Process Technologies/Severn Trent Services, pioneered the development of denitrification filter technology and continues to make advances. With the expiration of the original process patents, several other filter manufacturers are developing a denitrification option for their equipment. While Tetra's denitrification experience is unparalleled, there are times when an alternate must be considered, such as under strict competitive bidding laws or upgrading existing filters for denitrification. This paper will provide a literature review documenting technology development and process performance; review the current manufacturers, patented features and their relevance; and examine how bidding requirements have been met in several states.