Skaneateles WWTP: Performance Testing Confirms Design Compliance Under Variable Seasonal Loading
The Skaneateles Wastewater Treatment Plant, serving the Village of Skaneateles, New York, began operation of its Entex Submerged Fixed-Film (SFF) hybrid system in October 2024. The installation combines Webitat and WavTex media in a configuration sized to meet strict seasonal ammonia-nitrogen limits. Two independent third-party performance tests, conducted in May and July 2025, provide operating data against which to evaluate the system’s performance relative to its original design basis.
Design Basis
| Parameter | Influent | Effluent |
| ADF, MGD | 0.59 | 0.59 |
| BOD, mg/L | 23.37 | 25 |
| BOD, lb/day | 115 | 123.02 |
| NH3-N, mg/L (Jun–Oct max) | 11.79 | 2.0 |
| NH3-N, lb/day (Jun–Oct) | 58 | 9.84 |
| NH3-N, mg/L (Nov–May max) | 11.79 | 9.0 |
| NH3-N, lb/day (Nov–May) | 58 | 44.29 |
Effluent limits are seasonally tiered, with the ammonia limit tightening from 9.0 mg/L to 2.0 mg/L during the summer season.
May 2025 Performance Test
Conducted over ten days between May 6 and May 17, 2025, this test coincided with a significant rainfall event on the first sampling date. That day produced anomalous influent and effluent readings inconsistent with the remaining nine days of testing and was excluded from the averages below as a weather-driven outlier rather than a representative operating condition.
| Metric | Average (9 days) | Design |
|---|---|---|
| Average flow, MGD | 1.22 | 0.59 |
| Influent BOD load, lb/day | 298.3 | 115 |
| Effluent BOD concentration, mg/L | 3.69 | 25 |
| BOD % removal | 98.8% | 78.3% |
| Influent NH3-N load, lb/day | 50.9 | 58 |
| Effluent NH3-N concentration, mg/L | 1.43 | 9.0 |
| NH3-N % removal | 97.2% | 84.5% |
Hydraulic flow during this test averaged roughly double the design basis, pushing influent BOD loading to approximately 2.6 times design. Despite this elevated loading, effluent concentrations for both BOD and ammonia remained well within the shoulder-season limits.
July 2025 Performance Test
Conducted over ten days between July 7 and July 22, 2025, this test evaluated the system under the more stringent summer ammonia limit.
|
Metric |
Average |
Design |
|---|---|---|
| Influent BOD load, lb/day | 79 | 115 |
| Effluent BOD concentration, mg/L | 1.82 | 25 |
| BOD % removal | 97.7% | 78.3% |
| Influent NH3-N load, lb/day | 31.91 | 58 |
| Effluent NH3-N concentration, mg/L | 0.630 | 2.0 |
| NH3-N % removal | 98.0% | 96.6% |
Influent loading during this test ran below design, with both BOD and ammonia loads coming in under their design values. Even so, effluent quality cleared the summer ammonia limit with substantial margin, averaging less than one-third of the 2.0 mg/L cap.
Discussion
Taken together, the two test periods demonstrate performance across materially different operating conditions. The July test confirmed compliance under the plant’s most restrictive discharge requirement, with loading at or below design. The May test showed that even under substantially elevated hydraulic and organic loading, likely reflecting spring infiltration and inflow, the Entex fixed-film process maintained effluent quality well inside applicable limits. The combined results point to an operating margin beyond the original design basis, particularly for BOD removal capacity under high hydraulic loading.