Design Standards & Guidance

Iowa Wastewater Facilities Design Standards

• Complete Set of Chapters, 12 MG
• Chapter 11: Project Submittals
• Chapter 12: Iowa Standards for Sewer Systems
• Chapter 13: Wastewater Pumping Stations and Force Mains
• Chapter 14: Wastewater Treatment Works
• Chapter 15: Screening and Grit Removal
• Chapter 16: Settling
• Chapter 17: Sludge Handling and Disposal
• Chapter 18a: Fixed Film Media Treatment
• Chapter 18b: Activated Sludge Biological Treatment
• Chapter 18c: Wastewater Treatment Ponds (Lagoons)
• Chapter 19: Supplemental Treatment Processes
• Chapter 20: Disinfection
• Chapter 21: Land Application of Wastewater

Ten States Standards

The "Recommended Standards for Wastewater Facilities" by the Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers, commonly referred to as the Ten States Standards, is referenced in state rules and used by the Iowa DNR to supplement Iowa's Wastewater Facilities Design Standards. Iowa is represented on the Board. The 2014 Edition is available online from the Ten States Standards website. This wastewater facilities design document is an update prepared jointly by a board including ten Midwestern states and the Province of Ontario.

Design Standards Update

The Iowa Wastewater Facilities Design Standards (IWFDS) were adopted in the late 1970's and early 1980's. The Iowa DNR initiated a review of selected Chapters (11, 12, 13, 14, and 18C) in 2018, and revisions were proposed. As part of the required rule review for Executive Order 10 (EO10), all of the chapters in the IWFDS are being reviewed and revised. Copies of the proposed revisions can be downloaded using the links below. See the Water Quality Rulemaking page for more information on EO10 and the proposed rule revisions associated with EO10.

Proposed Changes August 2024

Proposed Changes May 2021

Alternative Wastewater Treatment Design Guidance Manuals

The DNR has developed design guidance manuals for five technologies in an effort to broaden the number of treatment options considered for managing wastewater within Iowa's communities (with populations ranging from 25 to 250) and provide uniform design guidelines for everyone involved to follow.

The five alternative technologies evaluated are: Recirculating Media Filters, Sand Mounds, Drip Dispersal, Constructed Wetlands, and Alternative Collection Systems. Understanding the design guidance is important for consulting engineers and planners involved in the planning, funding, and design, and construction of wastewater treatment improvement projects since they are not addressed in current rules.

The guidance will enable professionals to evaluate these alternatives and work through the state approval process with confidence.

• Recirculating Media Filter Technology Assessment and Design Guidance Manual
• Sand Mound Technology Assessment and Design Guidance Manual
• Drip Dispersal Systems Technology Assessment and Design Guidance Manual
• Constructed Wetlands Technology Assessment and Design Guidance Manual
• Alternative Collection Systems Technology Assessment and Design Guidance Manual
  • Appendix A - Primary Treatment Units, Septic Tanks For Small Community Systems
  • Appendix B - Pressure Distribution Network Design

Alternative Wastewater Treatment Design Guidance Documents - Technology Assessments

Due to revisions to Iowa’s Water Quality Standards, many communities have been faced with more stringent NPDES Permit limits for bacteria and end-of-pipe ammonia limits. Communities may experience significant costs associated with upgrading existing or building new wastewater infrastructure to meet effluent limits. These conditions created a need to broaden the treatment options considered for managing wastewater in Iowa communities.

The DNR has evaluated several new technologies for wastewater treatment as provided in section 14.4.3 “Required Engineering Data for New Process Evaluation” in the  the Iowa Wastewater Facilities Design Standards (IWFDS). These technologies are not addressed by detailed design criteria in the IWFDS. 

After research and data analysis, DNR staff developed technical design guidance for alternative wastewater treatment technologies. These assessments in addition to the applicable IWFDS are intended to provide guidance to designers for project submittals to DNR for review and approval based on current empirical information relative to the capabilities of the process in various applications. These processes were evaluated for technical capability for treating small municipal systems with primarily domestic wastewater only without industrial or significant commercial loads.

These assessments are not design standards, but when used in conjunction with design standards, should serve as expectations of the Department for permit approval. Based on information and experience, additional design standards may be developed in the future.

• Assessment No. 09-01 LemTec Biological Treatment
• Assessment No. 09-02 AdvanTex Treatment
• Assessment No. 11-01 SAGR Treatment (Updated December 2016)
• SAGR Example Calculations

Additional Design Guidance Documents

• Iowa DNR Design Guidance and Criteria for Sequencing Batch Reactors (SBRs)
• Geotechnical Reviews Presentation (presented by Iowa Geological and Water Survey 2/21/12)