November 7, 2002

Disclaimer

The Pennsylvania Department of Environmental Protection does not endorse or recommend any of the technologies described herein. The technical articles are provided for informational purposes only. Persons seeking additional information about the described technologies should contact the parties listed in the article.

The SHARON® process (Single reactor system for High activity Ammonium Removal Over Nitrite) is a new treatment technology offered by M2T Technologies, Inc. This high-rate nitrification/denitrification process is used for the removal of nitrogen components from wastewater flow streams containing high concentrations of nitrogen. Because it operates with minimal sludge retention time, a substantially smaller reactor volume is needed than is currently required for conventional nitrification and denitrification. In addition, the process allows for both a savings of twenty five percent (25%) in oxygen transfer energy and forty percent (40%) in carbon feed for denitrifying bacterial growth compared to conventional processes.

The two core concepts on which the process is based is that (a) at temperatures above 15° C, in particular between 30-40° C, the growth rate of the nitrifying bacteria is greater than the nitrafying bacteria and (b) denitrifying bacteria are capable of anoxic conversions of nitrite to nitrogen gas. Due to differences in growth rates of the bacterial species at the process design temperature (30-40 °C), a selection can be made in which the nitrite oxidizing bacteria can be washed out of the system while ammonia oxidizing bacteria are retained along with denitrifying bacteria. Using this metabolic mode of operation allows for the 25% reduction in aeration energy required for nitrification and the 40% reduction in the amount of BOD addition needed for denitrification. In addition, since the process is accomplished in a side stream, there are savings in mainstream reactor costs.

The process is used in the treatment of municipal wastewater side streams from both dewatered digested primary sludge and waste activated biosolids to achieve high total overall nitrogen removal. It is also used for the treatment of concentrate from sludge and biosolids drying facilities, of high strength landfill leachate, and of manure treatment wastewaters.

The SHARON® reactor has been implemented on full-scale basis and has demonstrated an unutilized metabolic pathway for total nitrogen removal. The reactor converts ammonia mainly to nitrite by oxidation at a minimal sludge retention time and at temperatures between 30-40°C. In this mode of operation, the reactor selects Nitrosomonas over Nitrobactor by washout of Nitrobactor. The nitrite is then anoxically converted to nitrogen gas. The reactor pH is controlled by the production of alkalinity from the denitrification process. Ammonia removal efficiencies of greater than 90% have resulted. (This is 90% reduction in the recycle flow where the influent flow contains 600-1000 mg/L ammonia. The effluent can be controlled to between 85-95% ammonia removal through adjustments to the solids retention time (SRT), pH, and dissolved oxygen (DO).)

PROCESS SCHEMATIC

The growth rates of nitrifying bacteria (Nitrosomonas) are significantly different from nitrafying bacteria (Nitrobactor). At low temperatures up to 12°C, the growth rate of Nitrobactor is higher than that of Nitrosomonas. Above 12°C, Nitrosomonas growth rate is higher than that of Nitrobactor and becomes significantly higher above 25°C. On a conceptual basis, a reactor can be designed based on these principles to provide total nitrogen removal from wastewater. The biochemistry results in significant reductions in the required oxygen to be transferred for oxidation and also in the amount of carbon addition required for bacterial growth in denitrification. Since the oxidation of ammonia is taken only to nitrite, and nitrite is reduced

SHARON ® REACTOR SCHEMATIC

instead of being taken to nitrate and having the nitrate reduced, there is a 25 % reduction in the oxygen requirements and a 40 % reduction in the carbon requirements. The SHARON ® reactor accomplishes this at a minimal sludge retention time and at an elevated temperature in order to select the Nitrosomas over the Nitrobactor. The process is run first in an oxic mode and then in an anoxic mode to accomplish both oxidation and reduction resulting in nitrification and denitrification, without nitrafication. The reactor can be run as an intermittent aerated reactor or a continuous-flow staged reactor. By using intermittent aeration, both nitrification and denitrification can be accomplished in a single reactor.

A characteristic feature of the reactor is that the biochemistry takes place without sludge retention. That is, the sludge retention time is equal to the liquid's hydraulic detention time. This is to allow selection of the Nitrosomas bacteria. There is no need to develop large clusters of microbial floc since the reactor is run with free cell mass or small clusters of bacteria.

• Minimal site excavation needed for implementation

• Amenability of construction sequencing to current plant operations

• Operational simplicity

• Washout protection for nitrifiers

• None known as of the present.

The Rotterdam, Dorkhaven, Netherlands, Wastewater Treatment Plant needed to provide treatment to comply with the new stringent total nitrogen removal requirements. However, there was little area available for constructing treatment facilities. Many processes were investigated. An analysis of several different technologies for N-removal showed that the new SHARON® process was the most cost effective of all the processes. (A comparison of technologies for side-stream treatment is provided in Exhibit A at the end of this report. The Delft University of Technology synthesized the SHARON® concept and tested it on the laboratory scale. A scale-up mathematical model was developed to design the full-scale facility. Grontmij Water and Wastewater Management in cooperation with the Water Authority ZHEW did the detailed design of the SHARON ® reactor and ancillaries. The design parameters are listed in Exhibit B.) To accommodate the SHARON system in light of the site restrictions, a post thickener was taken out of operation and converted to a SHARON® reactor. The 1800 m3 (0.476 MG) reactor was designed for treatment of the side-stream of recycled wastewaters from biosolids treatment and processing. The recycle stream ranges from 3-4% of the main stream.

The reactor was initially filled with river water and heated to 30°C. It was then seeded with waste activated sludge. The flow was gradually increased in stepwise increments until it reached full flow and load. The average nitrogen load in the recycle stream was 520 kg N/ day (1,146 lbs/day). The feed to the reactor depended upon the amount of the plant's processed biosolids. The flow variation was between 0 and 980 m3/day (0.259 MGD). The recycle stream's average ammonia concentration was 1230 mg N/l with a maximum of 1530 mg N/l - higher than the design value of 1000 mg N/l. Both the reactor's hydraulic and oxic detention times were gradually decreased until the concentrations reached design.

Ammonia was initially converted to both nitrate and nitrite. (This was attributed to the long oxic retention time and bacteria present in the seed.) Both nitrate and nitrite were then partially reduced until the process stabilized. The process proved to be stable and insensitive to variations of the load or other disturbances such as high influent SS concentrations.

Results of the testing found that denitrification via the nitrite metabolic pathway occurred. Also, the effect of the SHARON® reactor's operation on the overall plant effluent was positive resulting in the total nitrogen removal of above 90% and ammonia removal of 60%. (The plant had the capability of providing two-stage nitrification on their main stream. With both main stream and recycle stream ammonia removal, the facility was able to attain a total nitrogen removal of above 90%.) A graph showing the effluent results for the Dokhaven plant is provided in Exhibit C.

In general, the pertinent principles of both nitrification/denitrification and the SHARON® process design parameters are developed. Three full-scale SHARON® systems have been constructed at wastewater treatment plants in The Netherlands while a fourth is under design. Operating plants include: the Rotterdam (Dorkhaven) Wastewater Treatment Plant (1999) and the Utrecht Wastewater Plant (1997). The Zwolle Treatment Plant is under construction (2003) and a fourth plant – the Beverwijk Treatment Plant – is being designed with construction completion scheduled for 2003.

There are no full-scale SHARON® installations in the U.S. However, there is a pilot plant at the 93rd Ave WWTP in Phoenix, Arizona and one at the Contra Costa Sewer District, California. Currently, the City of New York is negotiating with Grontmij for a facility to be installed at their Wards Island facility. Also, the County Sanitation Districts of Los Angeles County (CSDLAC) is developing a proposal to WERF to demonstrate SHARON® at their Valencia, CA facility.

Capital and O&M costs for the system vary by the type and size of facility. For site-specific unit design and costs, it is recommended to contact the manufacturer directly.

Sources of Additional Information about the SHARON® system can be obtained from Mr. Alphonse Warakomski, M2T2 Lotepro Environmental Systems and Technology, 8833 North Congress Avenue, Suite 818, Kansas City, MO 64153, (816) 854-1969, by e-mail at awarakomski@m2ttech.com or awarakomski@loteproesg.com or from m²t Technologies, Inc. Suite 423, 8 John Walsh Boulevard, Peekskill, NY 10566, by e-mail at Kimm@m2ttech.com, or by web site at www.m2ttech.com.

ACKNOWLEDGEMENTS

Information for this Technology Review was obtained from publications and/or work by:

R. van Kempen (Grontmij Water and Waste Management, De Bilt The Netherlands)
J. W. Mulder (Water Authority Hollandse Eilanden and Waarden, Dordrecht, The Netherlands)
J.J. Heijnen, C. Hellinga, and M. C. M. van Loosdrecht (Department of Biochemical Engineering, Delft University of Technology, Delft, The Netherlands), and
Alphonse Warakomski (M2T2 Lotepro Environmental Systems and Technology)

EXHIBIT A
COMPARISON OF TECHNOLOGY FOR SIDE STREAM TREATMENT PLANT

EXHIBIT B
DESIGN PARAMETERS ROTTERDAM, DOKHAVEN PLANT, THE NETHERLANDS

EXHIBIT C ROTTERDAM DOKHAVEN PLANT EFFLUENT RESULTS

This report has been prepared and submitted by Renee Bartholomew, PA Department of Environmental Protection, Bureau of Water Supply and Wastewater Management, Division of Municipal Financial Assistance, Innovative Technology Section, at (717) 787-3481 or e-mail at rebartholo@state.pa.us.