Wastewater Operator Calculator
MCRT, SVI & BOD Calculator
Free · Designed for iPad. Not verified for macOS.
The professional wastewater calculator is built for licensed operators.
16 essential calculations covering Class I through Class IV certification math — from basic Pounds formulas to MCRT, F/M Ratio, and Volatile Solids Reduction. Every result shows the formula and your substituted values so you can verify the math yourself.
CALCULATORS INCLUDED:
Hydraulics & Loading
• Pounds / Mass Loading (lb/day = MGD × mg/L × 8.34)
• Flow Rate Conversions (MGD, GPM, GPD, cfs)
• Detention Time (accepts GPD, MGD, or GPM)
• Percent Removal
• Chemical Dose / Feed Rate (dry and liquid with SG)
• Surface Overflow Rate (SOR)
Solids Control
• Sludge Volume Index (SVI)
• Return Activated Sludge Rate (RAS %)
• MLSS / MLVSS Inventory
• RAS Solids Balance
Process Control
• Sludge Age — Basic (Class I/II)
• MCRT / SRT — Full (Class III/IV, includes effluent SS)
• F/M Ratio
• Solids Loading Rate
• OUR / SOUR
• Volatile Solids Reduction (Van Kleeck)
BUILT FOR THE FIELD:
• Works 100% offline — concrete bunkers, underground pump stations, rural facilities
• Large, readable results designed for gloved hands
• "Show Your Work" expands to show your exact values substituted into the formula
• Copy Result pastes a formatted summary ready for texts or emails to your supervisor
• Formula reference screen with all formulas, variables, and source attribution
• Calculation history saves your last 20 results
• Dark mode support
SHOW YOUR WORK:
Every result displays the formula that produced it. Tap "Show Your Work" to see your actual input values plugged into the equation — the same way you'd show work on a certification exam.
Based on ABC, Sacramento State OIT, and state certification formula sheets.
Ratings & Reviews
- This app has not received enough ratings or reviews to display an overview.
-Updated UI across all screens/calculators
The developer, Mike Watson, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Provider
- Mike Watson
- Size
- 28.7 MB
- Category
- Utilities
- Compatibility
Requires iOS 15.1 or later.
- iPhone
Requires iOS 15.1 or later. - iPad
Requires iPadOS 15.1 or later. - iPod touch
Requires iOS 15.1 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Mike Watson