On November 19, 2012, the State of Iowa announced the release of the Iowa Nutrient Reduction Strategy for public comment which will end on January 4, 2013. The Iowa Nutrient Reduction Strategy is a science and technology-based approach to assess and reduce nutrients delivered to Iowa waterways and the Gulf of Mexico. The strategy outlines voluntary efforts to reduce nutrients in surface water from both point sources and nonpoint sources.
As its approach to reducing nutrient loading from point source discharges, the Iowa Department of Natural Resources will be working with major facilities throughout the state to reduce nutrient discharges from point sources to Iowa’s waters with a goal of reducing total phosphorus by 16% and total nitrogen by 4 %. Under the draft plan, all major wastewater treatment facilities and minor industrial facilities that already treat process wastewater using biological treatment will be required to evaluate the economic and technical feasibility for installing biological nutrient removal (BNR). It is expected that most major municipal wastewater treatment facilities (>1 MGD AWW Flow) can economically meet technology-based TN limits of 10 mg/L and TP limits of 1 mg/L on an annual average basis with BNR technology. Technology-based nutrient limits for industrial facilities and municipal facilities that have significant industrial loads will be developed on a case-by-case basis due to the differing amounts of nutrients present in these wastewaters. Nutrient reduction will be required for major industries where it is found by IDNR to be feasible, reasonable and cost effective using the procedures specified in 40 CFR Part 125 Subpart A.
Permit limits for TN and TP will be expressed as an annual average. Since biological treatment processes are more efficient at reducing nutrients at higher water temperatures, higher quality wastewater effluent is typically produced in the spring, summer, and fall than in the winter. Thus, while properly designed and operated biological treatment systems may not be capable of meeting TN and TP limits of 10 mg/L and 1 mg/L respectively during winter months, data averaged for the year should yield results at or below these limits.
The basis for implementation of this approach is that the technology-based effluent limits for a pollutant not covered by federal effluent standards may be imposed on a case-by-case basis (IAC 567-62.8(5)). Such limitation must be based on the effect of the pollutant in water and the feasibility and reasonableness of treating such pollutant.
If a permitted discharger installs nutrient reduction processes and technology-based TN and TP limits are included in the NPDES permit, then it is the position of the IDNR that the TN and TP discharge limits will not be made more restrictive for a period of at least 10 years after the completion of the nutrient reduction process construction. Iowa Code section 455B.173(3C) establishes the moratorium on more restrictive limits for municipal dischargers. For non-municipal discharges, this prohibition can be enforced through the permitting process or as a part of the adoption of any future nutrient limitation. An evaluation of the nutrient removal performance and future optimization will be submitted to IDNR once facilities are constructed and have operated for a period of five years.
Technology-based nutrient requirements will be specified in municipal and industrial NPDES permits for major facilities, and minor industrial facilities with existing biological treatment systems, at the next permit renewal. NPDES permits will be amended or reissued to include effluent limits for TN and TP according to the following: 1) BNR already installed; 2) BNR not installed and no capacity increases are planned; 3) BNR not installed and capacity increases are planned:
Category 1) BNR already installed
a) Installed and Operating: If BNR is installed at a given plant and operating, then the NPDES permit will specify technology based limits (no more stringent than 10 mg/I TN; 1 mg/I TP) and will require influent and effluent monitoring for both parameters.
b) Installed and NOT Operating: If BNR is installed at a given plant and NOT operating, then the NPDES permit will require the BNR facilities to be operated. Final limits for TN and TP (no more stringent than 10 mg/I TN; 1 mg/I TP) will be incorporated into the NPDES permit at the end of a one year process optimization and performance evaluation. The NPDES permit will require influent and effluent monitoring for both parameters according to 567 IAC Chapter 63.
Category 2) BNR not installed and no capacity increases are planned
If BNR is not installed and no increases in treatment facility design capacity are planned, then the renewed NPDES permit will include a requirement for the facility to submit a report with the results of a study, within two years of reissuance of the NPDES permit, evaluating the costs and feasibility of installing BNR at a given wastewater treatment facility. The report will also include a proposed schedule for when BNR will be installed at a given wastewater treatment facility. The negotiated schedule will be incorporated into the NPDES permit or administrative consent order. The TN and TP discharge limits will be determined at the end of a one year process optimization and performance evaluation following the BNR process startup. The performance evaluation will include the determination of technologically achievable TN and TP concentrations. The NPDES permit will be amended to include the TN and TP limits as determined from the performance evaluation. The permit limits will be no more stringent than 10 mg/L TN and 1 mg/L TP. The NPDES permit will require influent and effluent monitoring for both parameters according to 567 IAC Chapter 63.
Category 3) BNR not installed and capacity increases are planned
If BNR is not installed and increases in treatment capacity are planned, then the evaluation of installing nutrient removal will be conducted as a part of the construction permitting process through current antidegradation procedures. Nutrient removal will be encouraged at this stage. If nutrient removal is not included with the plant expansion, then the NPDES permit will be written using the procedure in Category 2 above. If nutrient removal is included in the plant expansion, then the NPDES permit will be amended after a one year optimization and performance evaluation following BNR process startup, similar to the Category 2 procedures. The permit limits will be no more stringent than 10 mg/L TN and 1 mg/L TP. The NPDES permit will require influent and effluent monitoring for both parameters according to 567 IAC Chapter 63.
For an industrial wastewater facility with nutrient discharges but no biological treatment, a schedule will be incorporated into the next permit. The schedule will require the industry to assess the feasibility, reasonableness and cost of nutrient reductions. If nutrient reduction is found to be feasible, reasonable, and affordable, the permit will be revised to incorporate technology-based effluent limits based on the assessment.