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Arcata Marsh Current Performance
From Appropedia
Contents |
[edit] Current Performance
The Arcata Wastewater Treatment Plant has been designed in such a way that it uses natural and passive processes to treat its wastewater. Its ecological Dependant treatment style makes it so that the treatment's effectiveness is Dependant on that of the surrounding environment, similar to that of most natural systems. Although under seemingly normal conditions the treatment is under permit regulations, during the wetter seasons the infiltration levels can increase level of inflow up to five times that of the normal flow.
[edit] Arcata Wastewater Treatment Plant Process
The diagram to the right illustrates how wastewater enters the plant and is then discharged to the enhancement wetlands and then to the bay. As wastewater is processed through the plant; it is discharge to the wetlands multiple times. It's important to note this as it is a key factor to the effectiveness level. The wastewater will be filtered through the enhancement wetlands at least once as when the wastewater makes its way to the chlorination tank part of it is put back into the wetlands for further filtration. This allows for the most efficient removal of wastewater.
[edit] Mass Balance of the Plant
Mass Balance is essential in understanding how the plant is effected by annual precipitation and other possible variables that might effect the water and wastewater levels. Essentially it's a scientific approach to understand how much water is going in versus how much is going out of the plant.
- Dry Season Average: 2.3 MG/day
- Wet Season Average: 5.9 MG/day
[edit] Design Specifications
This is old data (1993) from EPA.
| Design Specification | |
|---|---|
| Capacity | |
| Design Population | 19,056 |
| Design Annual Flow | 2.3 MGD |
| Maximum Monthly Flow | 5.9 MGD |
| Peak Flow | 16.5 MGD |
| BOD Load | 41,000 lbs/day |
| TSS Load | 34,000 lbs/day |
| Headworks | |
| Mechanically Cleaned Bar Screens | 2 @ 5 MGD each |
| Gravity Grit Removal Tank | 144 ft2 |
| Primary Treatment | |
| 2 Primary Clarifiers | 26 ft diameter/ 60 ft diameter |
| Retention Time at Design Flow | 3.8 hours |
| Retention Time at Maximum Monthly Flow | 1.4 hours |
| Oxidation Ponds | |
| Total Area | 50 acres |
| Average Depth | 5 ft |
| Total Retention Time at Design Flow | 1.9 days |
| Treatment Wetlands | |
| Total Area | 7.5 acres in parallel |
| Average Depth | 2 ft |
| Total Retention Time at Design Flow | 1.9 days |
| Chlorination/ Dechlorination | |
| Volume | 185,400 gallons |
| Retention Time at Design Flow | |
| Retention Time at Maximum Monthly Flow | 30 minutes |
| Enhancement Marshes | |
| Total Area | 31 acres in series |
| Average Depth | 1.5 ft |
| Retention Time at Average Flow | 9 days |
[edit] Regulations
The Arcata Wastewater Treatment Plant is regulated by the State of California North Coast Water Quality Control Board. The Water Board administrates the National Pollutant Discharge Elimination System (NPEDS) discharge permit in California under the Environmental Protection Agency (EPA). Such permits include the Federal Clean Water Act, and the State of California Porter-Cologne Act.
Treated effluent is discharged into Humboldt Bay at Outfall 001 (Figure 4). The outfall is located on an enclosed bay and because of which is subject to heavier water quality regulations.
[edit] Permits
The Arcata Wastewater Treatment Plant operates under two NPDES discharge permits. One permit regulates Outfall 001, where the treated water is discharged into Humboldt Bay. The other permit regulates Outfall 002, where the effluent is discharged from the Arcata Wastewater Treatment Plant into the Arcata Marsh and Wildlife Sanctuary. The tables below summarize the current effluent limits for Outfall 001 and Outfall 002 (Kulhman, 2007).
 Effluent Table Concerning Outfall 001 |
 Effluent Table Concerning Outfall 002 |
[edit] Violations
According to the EPA, the Arcata Wastewater Treatment Plant had been found to be in violation of the discharge permit limits 9 out of the 12 past quarterly reports (Jan 2005-Dec 2007) (EPA, "Facility Report.", 2008). NPDES found violations in TSS levels, as displayed in the table below. The treatment plant's violations are primarily BOD, TSS, and the 85% removal efficiency criteria (Kulhman, 2007).
[edit] Intakes & Filters
[edit] Photos
 Group of Intakes |
 Intake |
 Filtration Pool |
[edit] References
http://www.humboldt.edu/~ere_dept/
[edit] Introduction
Some introduction text and background can go here.
