3.2.2 SSP2 STEP Tank
This section details the Septic Treatment and Effluent Pumping (STEP) tank serving Bungalows 1–16, designated as SPS2 (replacing the former SSP2 distribution box and lift well).
- Location: Opposite side of the causeway from SSP1, eastern end of Bungalow 16
Layout Diagram
Legacy System Decommissioned
The old SPS2 infrastructure — concrete distribution box, dual lift pumps, and 50 mm discharge pipe to SSP1 — has been decommissioned and replaced by this STEP tank.
Role in Collection Network
SPS2 serves Zone 2 of the collection network. Gravity sewer from Bungalows 1–16 discharges into this tank, which provides primary treatment and pumps primary clarified effluent to the WWTP.
Tank Specifications
| Item | Detail |
|---|---|
| Type | 22,000 L concrete tank with internal epoxy coating (H₂S attack prevention) |
| Manufacturer | Taylex Tanks (installed by Fastcall Plumbing NT) |
| Anti-flotation | Concrete ring-beam poured around base to prevent movement from seasonal groundwater |
| Lids | 2 × fibreglass lids with extended risers (Orenco) |
| Venting | Venting lid with activated carbon odour suppression kit |
| Access | Tank shield anti-access grate |
Pump System
| Item | Detail |
|---|---|
| Pump Package | Orenco Biovault Pump Package (PVU72-2425-L) with Effluent Filter |
| Discharge Pumps | 2 × Orenco PF(50Hz)500712 — 3/4 hp, 50 gpm, 380–415 V, 50 Hz, 1-phase |
| Effluent Filter | Biotube 24" cartridge — prevents pump clogging from rags, wipes, and debris |
| Controller | Orenco MVP Duplex Panel, 230 V (MVP-DAX2DM AU/NZ Style) |
Only primary clarified effluent is discharged from this tank. Solids remain in the underground tank for passive anaerobic treatment. Desludging is required approximately every 6–8 years.
Flow System
- Inflow: Gravity sewer from Bungalows 1–16 (DN150 common main via access chambers)
- Discharge: Primary clarified effluent pumped to WWTP Primary Tank 1 (PT-1)
Maintenance
SPS2-Specific Tasks (from O&M Manual Table 1)
| Task | Action | Frequency | Responsible |
|---|---|---|---|
| Check Biotube® Effluent Filters; clean as required | Inspect and clean 24" cartridge filter | Quarterly | ENVR |
| Check Biotube® Pump Vault Filters; clean as required | Inspect Biovault filter assembly | Quarterly | ENVR |
| Sludge accumulation assessment | Measure sludge and scum levels; organise de-sludge pump-out if required | Quarterly | ENVR |
See 3.2.15 O&M and Contingency for the full maintenance program.
Version Control
| Version | Date | Description |
|---|---|---|
| 1.0 | 2025-10-06 | Initial Release (legacy distribution box and lift well) |
| 2.0 | 2026-06-22 | Rewritten for STEP tank replacement per O&M Manual V1.1 |
| 2.0.1 | 2026-06-22 | Added STEP tank layout diagram |
Next Review Date: 2026-12-22