# Sustainable Technologies for Achieving Very Low **Nitrogen and Phosphorus Effluent Levels** 

# I n 2001 the U.S. Environmental Protection Agency published new criteria for nutrients in receiving waters, driving wastewater treatment plants (WWTPs) to significantly lower total nitrogen (TN) and total phosphorus (TP) in treated effluents. Although existing technology produces effluents containing either low TN and TP levels (5 mg/L and 0.5 mg/L, respectively) or very low TN and TP levels (3 mg/L and 0.1 mg/L, respectively), there has not been a comprehensive assessment of efficiency and long-term sustainability of the technologies. This WERF project fills the gap with a cost-benefit analysis of the various nutrient removal technologies. WWTPs can use this information to compare capital and operating costs of nutrient removal schemes, and regulatory agencies can use it to better assess the technology constraints and economics of nutrient removal. 

### Current Technologies Have Limitations The team surveyed WWTPs and conducted an extensive literature search. They also summarized case studies on design, operating and performance data, and regulatory compliance with low TN and/or TP effluent requirements. The researchers found several state-of-the-art technologies currently in vogue to achieve low TN and TP. They also found, however, that most nutrient removal plants can remove either TP or TN to very low levels, but not both. The various modes for N and P removal include tertiary treatment systems such as chemical precipitation and effluent filtration for P reduction, and denitrification filters and/or methanol addition in secondary or tertiary systems to enhance N removal. The study also noted that upgrading the treatment plants to achieve very low N and P levels would add significant costs. Factors driving the cost increases include the use of chemicals, effluent filtration, increased energy needs, provisions for redundancy and reliability, and increased sludge processing. The study underscored several other challenges to achieving very low TN and TP levels. One problem is the lack of organic carbon (or another electron donor) for biological nutrient removal (BNR). Others include the presence (in the influent) of hard-to-remove or recalcitrant forms of dissolved organic nitrogen (DON), and the presence of byproducts of the BNR process. 

### Project Team Evaluated Nutrient Removal Alternatives The project team developed a technology threshold matrix (for plant capacity up to 100 MGD) that would guide selection of treatment alternatives. 

### B **ene f**  **its**

n Evaluates technologies to achieve low levels of total nitrogen (TN) and total phos

phorus (TP) in wastewater effluent.

n Identifies key challenges and knowledge gaps in achieving very low TN and TP levels.

n Discusses potential constraints in achieving very low TN and TP levels attributable to the speciation of TN and TP – in influent and efflu

ent and in the BNR process – that are not efficiently removed in current processes.

n Informs regulators of the feasibility and cost benefits of nutrient reduction to very low effluent levels of reactive and non-reac

tive nutrients. 

### R **elate d P**  **r odu**  **cts** Technology Assessments: Nitrogen Removal Using Oxidation Ditches (96CTS1) Characterizing Mechanisms of Simultaneous Biological Nutrient Removal During Wastewater Treatment (00CTS17UR) Factors Influencing the Reliability of Enhanced Biological Phosphorus Removal (01CTS3) Dissolved Organic Nitrogen Characterization and Bioavailability in Wastewater Effluents (02CTS1a) On-Line Nitrogen Monitoring and Control Strategies (03CTS8) WERF Workshop on Nutrient Removal: How Low Can We Go? (05CTS1W) 

### R **elate d**  **On go**  **in g R**  **esearch** Nutrient Challenge Program (NUT1R06) 

### A

**vailable F**  **o r**  **m at** 

Online PDF. 

# Wat e r E n v i r o n m e n t R e s e a r c h F o u n d at i o n w a s t e w at e r t r e at m e n t a n d r e u s e 

# E X ECUTIVE SUMMAR Y

**T O**  **O R**  **D ER** 
Contact WERF at 703-684-2470 or visit www.werf.org and click on Search Research Publications & Tools. WERF Subscribers: Download unlimited free PDFs at www.werf.org. Non-Subscribers: Charges apply to some products. Visit www.werf.org for more information. Refer to: 

### S **t o**  **c k No. 02CTS1** 

For more information, log on to www.werf.org

. 

### As effluent limits become more stringent, **better characterization of influent wastewater and source tracking of pollutants into the**  **collection system is needed.**One of the main criteria in comparing the various N and P removal technologies is achieving effluent quality on a sustainable basis. The technology assessment entailed a two-tier system for nutrient removal: Tier I effluents (TN and TP levels of less than 5.0 mg/L and 0.5 mg/L, respectively) and Tier II effluents (TN and TP levels of less than 3.0 mg/L and 0.1 mg/L, respectively). Economic criteria included the cost of implementing the technologies. The team learned that emerging technologies – such as sidestream N removal by SHARON/Anammox (anaerobic ammonium oxidation), and implementation of membrane bioreactor systems – can achieve lower nutrient levels. The following processes consistently received high scores in the evaluation process. Bardenpho process employs a series of aerobic and anoxic tanks; Johannesburg process is a modification of the Bardenpho process.


### Bardenpho + chem-P + sand filtration Modified Bardenpho + chem-P + sand filtration Modified Bardenpho with fermenter + sand filtration Johannesburg high IR + chem-P + sand filtration

The team evaluated selected technologies at lab-scale, pilot-scale, and full-scale. Labscale MBR studies included: 1) treatment of highly concentrated ammonium rich centrate wastewater (sidestreams in WWTPs) to obtain low TN values in the effluent; and 2) investigation of simultaneous nitrification and denitrification of dilute wastewater without compromising the COD removal under low DO conditions. They also used a pilot-scale MBR system to achieve simultaneous low TN and TP in the wastewater effluent on a sustainable basis at the Flagg Creek WWTP (Hinsdale, IL). In a demonstration study, the team investigated chemically enhanced P removal in the anaerobic zone of the EBPR process and chemical usage minimization. The research also describes the full-scale technology demonstration at John Egan Wastewater Reclamation Plant at the Metropolitan Water Reclamation District of Greater Chicago, using step-feed BNR and chemical P removal to achieve low TN and TP levels, respectively. The report discusses N and P speciation projects at participating WWTPs, including selected Illinois plants, and the District of Columbia Water and Sewer Authority Blue Plains advanced treatment plant.



### F **uture Research Needs** Additional research efforts are warranted in several related areas: 1) identification of alternative carbon sources for N and P removal; 2) source control of N and P to minimize their loads on the treatment plants; 3) ways to deal with the composition and calcitrant constituents of DON in influent wastewater; 4) impact of BNR processes in the generation of DON products; and 5) integrated strategies to balance point and non-point source control of N and P in a watershed approach. 

### Related Research WERF project, Dissolved Organic Nitrogen Characterization and Bioavailability in Wastewater Effluents (02CTS1a), investigated the speciation of the TN in the treated effluent and suggested that the dissolved organic nitrogen (DON) formed a major part of the total nitrogen in the effluent that was derived from incoming wastewater sources and from the biological treatment processes (products of cell metabolism and lysis) employed to reduce nitrogen levels. DON’s bioavailability for bacteria and algae growth – triggering eutrophication in the receiving waters – has sparked considerable interest among researchers seeking a rational regulatory approach to setting nitrogen levels in the discharge permits, particularly in regard to DON. WERF is actively pursuing this effort. WERF research is also assessing the limits of technology (LOT) of the biological processes and inherent constraints to removal of total nitrogen to very low levels (less than 3 mg/L). 

### Sustainable Technologies for Achieving Very Low Nitrogen and Phosphorus Effluent Levels



### Co **ntract o**  **rs** Krishna R. Pagilla, Ph.D., P.E. Illinois Institute of Technology Meltem Urgun-Demirtas, Ph.D. Illinois Institute of Technology



### P **r oj**  **ect Su**  **bc omm**  **ittee** James L. Barnard, Ph.D., P. Eng. Black and Veatch Rajendra P. Bhattarai, P.E. City of Austin John T. Novak, Ph.D., P.E. Virginia Tech Andrea C. Rex, Ph.D. Massachusetts Water Resources Authority Rao Y. Surampalli, Ph.D., P.E. U.S. Environmental Protection Agency Kenneth N. Wood, P.E. DuPont

Water Environment Research Foundation n 635 Slaters Lane, Suite 300 Alexandria n VA 22314-1177 

# E X ECUTIVE SUMMAR Y

The research on which this report is based was funded in part by the U.S. Environmental Protection Agency (U.S. EPA) through Cooperative Agreement No. CR-83155901 with the Water Environment Research Foundation (WERF). Unless an U.S. EPA logo appears on the cover, this report is a publica

tion of WERF, not U.S. EPA. Funds awarded under the agreement cited above were not used for editorial services, reproduction, printing, or distribution. 6/09