Summary of Design Guidance for Wastewater Treatment Facilities - PUB2417

This document provides engineering consultants a comprehensive guide of the Missouri Department of Natural Resources’ recommendations and requirements for a summary of design for wastewater treatment facilities. A summary of design shall accompany the plans and specifications when applying for a construction permit per 10 CSR 20-8.110(8) and 10 CSR 20-6.010(5)(G)5.

The following is a sample format for the required summary of design content:

Hydraulic and Organic Loadings

• Design average flow – The average of the daily volumes to be received for a continuous 12-month period expressed as a volume per unit time. However, the design average flow for facilities having critical seasonal high hydraulic loading periods (e.g., recreational areas, campuses and industrial facilities) shall be based on the daily average flow during the seasonal period.
• Design peak hourly flow – The largest volume of flow to be received during a one-hour period expressed as a volume per unit of time.
• Design maximum daily flow – The largest volume of flow to be received during a continuous 24-hour period expressed as a volume per unit of time
• Five-day Design average (BOD₅) – Generally, the average of the organic load received for a continuous 12-month period for the design year expressed as weight per day. However, the design average BOD₅ for facilities having critical seasonal high loading periods (e.g., recreational areas, campuses and industrial facilities) shall be based on the daily average BOD₅ during the seasonal period.
• Projected suspended solids
• Impact from industrial sources (documented or assumed)
• Verification that downstream components (sewers, pumping stations and wastewater treatment facility units) have adequate capacity

Individual Process Units

Include the following information on all new or modified treatment components or components that are being utilized in a different manner; for example, a lagoon cell designed as discharging will now be utilized as a component in the no-discharge system.

• Unit type
• Unit dimensions
• Unit total volumes and useable volumes
• Unit flow rates
• Unit velocities
• Unit detention times at design average flow and at peak hourly flow
• Concentrations
• Recycle rates
• Chemical additive control
• Physical control
• Unit flexibility
• Flow metering
• Performance assumptions
• Pump and system curves

Anticipated Removal Rates and Effluent Quality

• Provide the expected removal rates and effluent concentrations of all permit parameters from the Missouri State Operating Permit or Water Quality Antidegradation Review. Include separate tabulations for hydraulic, organic and biosolids calculations for each process unit as well as the wastewater treatment facility as a whole.

Process Diagrams

• Flow diagrams with hydraulic capacity and organic load

Design Calculations

• Present any pertinent design calculations, tabulations, removal efficiency assumptions and design assumptions used to design the project.  
• Identify published technical design guides and references utilized. 10 CSR 20-8 Minimum Design Standards must be followed but does not provide all the information needed for a properly designed wastewater treatment facility or collection system.

Additional Information

• Design information related to architectural, structural and mechanical components of a system do not need to be included. The department does not review architectural or structural designs. Sketches may be desirable to aid in the presentation of the project. Most criteria related to mechanical designs do not need to be presented unless addressed in 10 CSR 20-8.120 through 10 CSR 20-8.210.
• Include any unusual specifications, construction materials and construction methods with explanations of their use in the project. Also include any maps, photographs and any other supporting data needed to describe the project in its entirety.