Newport’s wastewater treatment plant safely cleaned more than 3.4 billion gallons of water in 2024 — meeting all state and federal permit limits. On average, the plant removed about nine out of every ten parts of pollution, keeping the water we return to the bay clean and healthy.
What We Measure
Overall Rating on How We Performed
| Category | Performance | Comment |
|---|---|---|
| Organic pollution removal | Excellent 90%+ = healthy operation | 91.5% |
| Solids removal | Excellent | 90.4% |
| pH | Very Good | 6.9 – 7.1 (SU) |
| Fecal coliform | Excellent | < 25 MPN/100 mL (12 mo compliant)** |
| Flow treated | Excellent | ≈ 3.4 billion gallons |
| Effluent Quality | Excellent | Consistent low BOD/TSS effluent < 20 mg/L for 10 months |
| Flow Management | Strong | Handled > 15 MGD peak flows without permit exceedance |
| Disinfection | Excellent | All bacteria metrics < permit limits |
| Process Stability | Very Good | Only three isolated exceedance days (rapid response) |
| CSO Operations | Compliant | All events disinfected and reported timely |
Performance: Excellent 90%+ = healthy operation
Comment: 91.5%
Performance: Excellent
Comment: 90.4%
Performance: Very Good
Comment: 6.9 – 7.1 (SU)
Performance: Excellent
Comment: < 25 MPN/100 mL (12 mo compliant)**
Performance: Excellent
Comment: ≈ 3.4 billion gallons
Performance: Excellent
Comment: Consistent low BOD/TSS effluent < 20 mg/L for 10 months
Performance: Strong
Comment: Handled > 15 MGD peak flows without permit exceedance
Performance: Excellent
Comment: All bacteria metrics < permit limits
Performance: Very Good
Comment: Only three isolated exceedance days (rapid response)
Performance: Compliant
Comment: All events disinfected and reported timely
Storm Impacts and Maintenance
Heavy spring rains diluted incoming wastewater but did not cause any permit violations.
Combined Sewer Overflows (CSOs)
Most storms were fully contained. Only Washington Street had brief overflows during four major rain events (January, March, April, and December). Wellington Avenue had none all year.
| Month | Washington St. (MG) | Wellington Ave. (MG) | Notes |
|---|---|---|---|
| Jan 10 | 3.82 | 0 | Heavy rain (2.2″) – within permit |
| Mar 10 & 29 | 9.16 | 0 | Two storms; all limits met |
| Apr 4 | 4.36 | 0 | Met limits; slightly lower solids removal |
| Dec 12 | 1.04 | 0 | 15.4 MGD peak; no violations |
Washington St. (MG): 3.82
Wellington Ave. (MG): 0
Notes: Heavy rain (2.2″) – within permit
Washington St. (MG): 9.16
Wellington Ave. (MG): 0
Notes: Two storms; all limits met
Washington St. (MG): 4.36
Wellington Ave. (MG): 0
Notes: Met limits; slightly lower solids removal
Washington St. (MG): 1.04
Wellington Ave. (MG): 0
Notes: 15.4 MGD peak; no violations
Monthly CSO Events Summary
| Month | Washington St. CSO (MG) | Wellington Ave. CSO (MG) | Remarks |
|---|---|---|---|
| Jan 10 | 3.82 | 0 | 2.22″ rain; exceeded 1-yr/6-hr storm depth (permit exempt) |
| Feb | 0 | 0 | No activation |
| Mar 10 & 29 | 9.16 | 0 | Two events (1.08″ & 1.75″ rain); met limits |
| Apr | 4.36 | 0 | Met bacteria and BOD limits; TSS 46.7% vs 50% min |
| May – Nov | 0 | 0 | No discharge |
| Dec 12 | 1.04 | 0 | Peak 15.38 MGD; TRC < 0.1 mg/L; within limits |
Washington St. CSO: 3.82 MG
Wellington Ave. CSO: 0 MG
Remarks: 2.22″ rain; exceeded 1-yr/6-hr storm depth (permit exempt)
Washington St. CSO: 0 MG
Wellington Ave. CSO: 0 MG
Remarks: No activation
Washington St. CSO: 9.16 MG
Wellington Ave. CSO: 0 MG
Remarks: Two events (1.08″ & 1.75″ rain); met limits
Washington St. CSO: 4.36 MG
Wellington Ave. CSO: 0 MG
Remarks: Met bacteria and BOD limits; TSS 46.7% vs 50% min
Washington St. CSO: 0 MG
Wellington Ave. CSO: 0 MG
Remarks: No discharge
Washington St. CSO: 1.04 MG
Wellington Ave. CSO: 0 MG
Remarks: Peak 15.38 MGD; TRC < 0.1 mg/L; within limits
Biosolids & Energy Performance
Water Quality Performance
Performance Data
- BOD₅ (mg/L): Stands for Five-day Biochemical Oxygen Demand. It measures the amount of dissolved oxygen consumed by microorganisms in a water sample over a period of five days at 20°C to break down organic matter. It is an indicator of the amount of biodegradable organic pollution in the water.
- TSS (mg/L): Stands for Total Suspended Solids. It measures the dry-weight of solid particles (e.g., silt, clay, organic matter, algae) that are suspended in water and can be removed by a filter. High TSS can make water appear cloudy and harm aquatic life.
- < 75% – Underperforming or process issue, 80–85% – Minimum acceptable for compliance, 85–95% – Typical healthy plant performance, > 95% – Very efficient treatment / tertiary polishing
- BOD/TSS Removal Efficiency (%): A measure of how effectively a wastewater treatment process or plant removes BOD or TSS pollutants. It is calculated using the formula: ((Influent Concentration – Effluent Concentration) / Influent Concentration) * 100.
- pH Scale (0–14), 7 = Neutral, Below 7 = Acidic, Above 7 = Basic/Alkaline
- pH (SU): A measure of how acidic or basic (alkaline) water is, reported in Standard Units (SU). The scale ranges from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, and values above 7 indicate basicness.
Microbial Indicators
- Fecal Coliform & Enterococci (Geometric Mean #/100 mL): These are types of bacteria that indicate the potential presence of fecal contamination from humans or animals. They are used as indicators of pathogens and public health risks. The concentration is typically expressed as a geometric mean (a specific type of average used for microbiological data) of the number of colonies per 100 milliliters of water sample.
Environmental Factors
- Average Monthly Flow (MGD): The average volume of water, typically wastewater, that flows through a system or treatment plant over a calendar month. It is measured in Million Gallons per Day. This parameter is crucial for managing system capacity and compliance with discharge limits.
Yearly Performance Highlights
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Observed Trends & Corrective Actions
| Category | Details |
|---|---|
| Winter–Spring (High Flows) | March and April rain events (> 7 inches each month) caused dilute influent and temporary TSS/BOD under-removals but no effluent limit exceedances. |
| Summer Events | July clarifier seal failure and August sample contamination issues led to isolated daily exceedances only; equipment and protocol repairs completed within two weeks. |
| Fall–Winter Recovery | September through December show consistently high removals, low solids, and excellent disinfection efficiency across all indicators. |
| Biosolids Management | Synagro removed ≈ 6,900 wet tons total; average cake solids ≈ 22 % (TKN ~25 mg/L, NH₃-N ~20 mg/L). |
| Energy & Flow Resilience | December’s 15.38 MGD peak handled without permit violations—confirming adequate hydraulic capacity under storm conditions. |
Details: March and April rain events (> 7 inches each month) caused dilute influent and temporary TSS/BOD under-removals but no effluent limit exceedances.
Details: July clarifier seal failure and August sample contamination issues led to isolated daily exceedances only; equipment and protocol repairs completed within two weeks.
Details: September through December show consistently high removals, low solids, and excellent disinfection efficiency across all indicators.
Details: Synagro removed ≈ 6,900 wet tons total; average cake solids ≈ 22 % (TKN ~25 mg/L, NH₃-N ~20 mg/L).
Details: December’s 15.38 MGD peak handled without permit violations—confirming adequate hydraulic capacity under storm conditions.
Compliance Notes
| Month 2024 | Notables / Compliance |
|---|---|
| Jan | Washington CSO 3.82 MG (1-day, met permit) |
| Feb | All within limits; no CSO discharge |
| Mar | Heavy rain; Washington CSO discharged 9.2 MG total (Mar 10 & 29); temporary BOD/TSS dilution |
| Apr | Washington CSO 4.36 MG (4 Apr); TSS removal 46.7% vs 50% limit |
| May | All parameters in compliance; no CSO events |
| Jun | No CSO discharge (June report confirmed) |
| Jul | Daily BOD/TSS exceedances (clarifier seal failure + 2.21″ storm); repairs made |
| Aug | BOD daily exceedances (Aug 5 & 11, stalked ciliates in samples); resolved |
| Sep | Stable operation; no CSO activity |
| Oct | Excellent performance; no exceedances |
| Nov | Compliant operation; steady solids profile |
| Dec | Storm (Dec 12, 2.98″) → peak 15.38 MGD; Washington CSO 1.04 MG; all limits met |
Notables: Washington CSO 3.82 MG (1-day, met permit)
Notables: All within limits; no CSO discharge
Notables: Heavy rain; Washington CSO discharged 9.2 MG total (Mar 10 & 29); temporary BOD/TSS dilution
Notables: Washington CSO 4.36 MG (4 Apr); TSS removal 46.7% vs 50% limit
Notables: All parameters in compliance; no CSO events
Notables: No CSO discharge (June report confirmed)
Notables: Daily BOD/TSS exceedances (clarifier seal failure + 2.21″ storm); repairs made
Notables: BOD daily exceedances (Aug 5 & 11, stalked ciliates in samples); resolved
Notables: Stable operation; no CSO activity
Notables: Excellent performance; no exceedances
Notables: Compliant operation; steady solids profile
Notables: Storm (Dec 12, 2.98″) → peak 15.38 MGD; Washington CSO 1.04 MG; all limits met