Guest Column | December 1, 2014

Math Solutions: Load Calculations

Wastewater Dan Theobald

By Daniel Theobald, "Wastewater Dan"


Water Online’s “Math Solutions,” presented by wastewater consultant and trainer Dan Theobald (“Wastewater Dan”), instructs operators on load calculations.

Whether for certification exams or on-the-job activities, the ability to perform load calculations is a valuable skill for treatment plant operators, facility designers, regulators, and educators alike.

Some common calculations for hydraulic loads and concentration/organic loads (biochemical oxygen demand) are shared below.

Calculate Hydraulic Load

Calculate weir loading rate in GPD:

Calculate weir loading rate in GPD/ft.:

Calculate weir loading rate in GPD/1,000 ft.:

Calculate Concentration/Organic Load

Calculate organic load in pounds of BOD per day (lbs/BOD/day):

Calculate organic load in lbs/BOD/day per 1,000 sq. ft.:

Complete playlist of Wastewater Dan’s Math Solutions

This is the Load Calculations presentation in my series of “Math Solutions.” If you have specific wastewater math queries, please submit a question.

About Dan Theobald:

Known in the industry as “Wastewater Dan,” Daniel L. Theobald, proprietor of Environmental Services (, is a professional wastewater and safety consultant/trainer. He has more than 24 years of hands-on industry experience operating many variants of wastewater treatment processing units and is eager to share with others his knowledge about water conservation.

Theobald serves as an active consultant for industries looking to achieve and maintain improved wastewater treatment at reduced cost. He is a Lifetime Member of the Who’s Who Registry of Professionals and holds numerous certifications from wastewater management regulatory boards and professional organizations. Theobald contributed one chapter to the Water Environment Federation’s ( Manual of Practice # 37 (MOP-37), a technical manual resource guide for biological nutrient removal, published in 2013.

Image credit: "Roue à palettes pour chenal algal," Sustainable sanitation © 2005, used under an Attribution-ShareAlike 2.0 Generic license: