1. Background
Appledore Island, ME: Aerial View

2. Wastewater flow Generated by toilets, showers and sinks
Varies daily and seasonally
Regimented daily schedule
Seasonal operation of the island
Average flow is 2000 gallons per day (range 1150 – 3450 gals/day)

3. SML Wastewater Flow Characteristics
SML Wastewater Flow vs. Time (days)

4. Process Flow
Primary Settling
Chlorination
Dechlorination

5. Primary Settling Three 1,000 gallon fiberglass tanks in series
Total Suspended Solids (TSS) removed by settling
Second tank has filter
Retains additional solids
Retention time hours
Caused by flow variation
Solids accumulate in tank bottom
Removed at end of season by vacuum pump

6. WWTF Schematic
1000 Gallon Settling Tanks

10. Chlorination Two 500 gallon batch disinfection tanks
Operated in parallel
12.5% sodium hypochlorite (NaOCl) used as disinfectant
Dosed at 20mg/L
Added to wastewater prior to entering batch tanks
Design contact time = 30 min
Time wastewater in batch tanks
Reduced contact time during daily peak flows

11. WWTF Schematic
1000 Gallon Settling Tanks

12. Dechlorination Sodium metabisulfite (Na2S2O5)
Added immediately upon exiting the disinfection batch tanks
Effluent pumped to outfall pipe

13. WWTF Schematic
1000 Gallon Settling Tanks