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It always feels good to meet your goals — even better to exceed them. Learn how an upgrade to biological nutrient removal (BNR) resulted in enhanced nutrient removal (ENR) performance. By Michele Braas I n recent years, many municipal wastewater treatment plants have needed to update processes and facilities to comply with more stringent environmental regulations related to cleaning up local bays and streams. For the Manheim Area Water & Sewer Authority (MAWSA), formerly known as Manheim Borough Authority, located in Lancaster County, PA, the operators took on the challenge of upgrading to BNR effluent levels. The organization reached Pennsylvania Department of Environmental Protection (PADEP) standards after installing a new facility and processes, and then went on to tweak processes through trial and error, achieving ENR with impressively low effluent levels. The History Nearly 10 years ago, the PADEP met with MAWSA and its wastewater engineer, RETTEW, to review the agency's strategy. The ultimate goal for the PADEP was to improve conditions in the Chesapeake Bay Watershed. The environmental agency set new total nitrogen and total phosphorus effluent limits for wastewater treatment plant (WWTP) discharges in Pennsylvania. MAWSA's WWTP would need to achieve an average of 6.0 mg/L total nitrogen and 0.8 mg/L total phosphorus discharge concentrations, based on the permitted flow for the facility. At that time, MAWSA operated a trickling filter plant, which could not meet the proposed nutrient limits without additional equipment and procedures. After evaluating future needs, MAWSA and RETTEW ana- lyzed alternatives such as sequencing batch reactors and fixed film filters. RETTEW recommended a phased oxidation ditch and integral anoxic tanks for MAWSA's BNR upgrade. The oxidation ditch is a continuous flow activated sludge system, with the main treatment processes isolated in separate oxidation ditches. The conditions of each ditch are altered between aerobic and anoxic conditions, thus achieving the desired treatment level. The rec- ommendation also included an anaerobic selector for biological phosphorus removal. Other proposed upgrades included new return sludge and waste-activated sludge pumps, new variable- speed drives on influent pumps, two new final clarifiers, a supple- mental carbon feed facility, a ferric chloride chemical feed system, and a biosolids storage facility. These changes would not only help MAWSA meet PADEP's goals but also prepare it to meet more rigorous discharge levels in the future if needed. The Upgrades Released for construction bidding in mid-2009, the upgrades were slated for completion in 2011, meeting the PADEP's man- dated timing of April 2012. The engineering design specified all upgrades to be installed on the same property as the existing facility, and treatment operations needed to remain continuous throughout the construction and installation. Undertaken by Wickersham Construction and Engineering, Inc. and Gettle, Inc., the contractors adhered to the schedule, allowing the new commissioning procedures to occur simultaneously with the decommissioning of the existing facilities. Throughout the construction process, some unforeseen chal- lenges surfaced. During excavation, the team discovered the 22 wateronline.com n Water Innovations Nontraditional Nutrient Reduction Techniques Traditionally, wastewater treatment facilities obtain ENR with the addition of filters or chemicals. At MAWSA, however, the facility's staff has been able to reach ENR-level discharges through optimizing its oxidation ditches.