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Plant Statistics:
| Area served: |
Beechville-Lakeside-Timberlea |
| Constructed: |
1984 |
| Engineering Firm: |
CBCL |
| Process: |
Enhanced secondary |
| Present Capacity: |
1.5 million imperial gallons per day (mgpd) |
| Ultimate Capacity: |
3.0 million imperial gallons per day (mgpd) |
| Receiving water: |
Nine Mile River |
Plant process:
 This facility was the first large scale rotating biological contactor (RBC) process constructed in Nova Scotia. Due to the sensitivity of the Nine Mile River ecosystem, a high quality effluent with phosphorous removal and nitrification (summer) was required in order to conform with Federal and Provincial regulatory approval guidelines. The Lakeside/Timberlea facility routinely produces an effluent quality of less than 10 mg/L BOD, 10 mg/L suspended solids, 1.5 mg/L P, 3.0 mg/L ammonia.
- Preliminary treatment consists of automatic bar screening and inorganic solids removal by means of an aerated grit chamber which also serves to oxygenate the raw influent wastewater. Primary clarifiers retain the wastewater flow for a period of 3-4 hours in order to allow heavier organic solids to settle by gravity. Scraper mechanisms remove surface floatables and grease which are transferred along with settled sludges, to the anaerobic digester operation. Primary effluent is directed to (2) trains of (4) RBC units in parallel. These contactors have a rotating ‘shaft' surrounded by plastic disks call ‘media' to which a biological growth attaches. The total media surface area is 1,000,000 sq.ft. As the RBC rotates in the wastewater, the fixed bacteria metabolize (feed upon) carbonaceous organic compounds which are converted to new bacterial growth, carbon dioxide and water. Nitrification, or the conversion of ammonia to nitrates, is performed by nitrifying bacteria which are established on the fourth stage RBC shafts. Secondary clarifiers collect spent RBC biomass and any remaining suspended solids. Alum is added at this stage in order to precipitate soluble phosphorus. Settled solids are pumped to the anaerobic digester. Disinfection: Chlorine is added to the secondary effluent prior to entering the chlorine contact tanks. Sufficient detention time (1 hour) allows the destruction of any remaining pathogenic bacteria. Post aeration tanks: Diffused air is applied in order to oxygenate the final effluent to a level of at least 5 mg/L dissolved oxygen.
- Biosolids (sludge) treatment and stabilization is performed by the anaerobic digestion process producing methane gas as a by-product. At present, methane provides 40% of boiler requirements for the facility buildings and digester heating.
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