What is the total phosphorus range typically found in wastewater?

• A. 1-5 mg/L
• B. 0.5-2 mg/L
• C. 5-20 mg/L
• D. 10-25 mg/L

Answer: (C)

Total phosphorus in municipal wastewater comes from human waste, detergents, and some food waste, so its concentration in typical untreated wastewater is in the multi-milligram per liter range. The common reference range for total phosphorus in wastewater is about 5 to 20 mg/L, which captures the usual variability across different communities and upstream inputs. After treatment, plants aim to reduce phosphorus to much lower levels (often around 1 mg/L or less) depending on permit requirements and the treatment process used.

That’s why this range fits best: it represents the standard influent concentration seen in many wastewater streams. The other ranges are either generally too low to reflect typical influent or represent effluent values or unusual high-load scenarios rather than the common starting point.