3.2.13 Disinfection and Final Polishing
This section details the microfiltration, UV disinfection, and chlorine dosing systems that polish treated effluent to Class A recycled water standards. Based on the LBC OWMS O&M Manual V1.1.
Distinct from Bore Chlorine System
This chlorine dosing system is part of the WWTP and is separate from the 3.1.3 Bore Chlorine Dosing System used for potable water treatment.
Treatment Sequence
Treated effluent from the discharge tank passes through the control room in this order:
- Microfiltration — polishes remaining suspended solids
- UV disinfection — primary disinfection
- Chlorine dosing — secondary disinfection
- Distribution — to RWS tanks or LAA irrigation areas
Microfiltration
| Item | Detail |
|---|---|
| Housing | Harmsco HUR 90 HP (Orenco) |
| Filters | HC/90-5 cartridge filters (Orenco) |
| Purpose | Achieve TSS target of <10 mg/L; ensure lowest turbidity for optimum UV disinfection |
| Position | Upstream of UV disinfection system |
Maintenance
| Task | Frequency | Responsible |
|---|---|---|
| Remove and clean filter cartridge | Quarterly | ENVR |
UV Disinfection
| Item | Detail |
|---|---|
| Model | Sanitron S5000C (Orenco) |
| Quantity | 2 units |
| Power | 220 V 1Ø, 0.64 A each |
| Control | Independent enable/disable points on T-COM panel |
| Fault behaviour | UV fault does not disable any pump |
Maintenance
| Task | Frequency | Responsible |
|---|---|---|
| Clean UV glass sleeves via internal wiper mechanism | Quarterly | ENVR |
| Replace UV lamps | Annually | ENVR |
Chlorine Dosing
| Item | Detail |
|---|---|
| System | Grundfos Dosing Station DDA 7.5-16 AR (1 L02 P1 02) |
| Supplier | Thinkwater NT |
| Location | Climate-controlled control room (20 ft container) |
Chlorine dosing provides secondary disinfection after UV treatment. Ample chlorine supply must always be available on site.
Chlorine Storage Safety
Chemical Storage
Chlorine and all chemicals must be stored in appropriately bunded and signed areas with relevant safety information and MSDS sheets readily available.
See 3.2.15 Safety Guidelines for full PPE and hazard requirements.
Class A Discharge Targets
| Parameter | Target |
|---|---|
| E. coli | ≤ 10 CFU/100 mL (max) |
| BOD | ≤ 30 mg/L (max) |
| TSS | ≤ 20 mg/L (max) |
| TN | ≤ 60 mg/L (avg) |
| TP | ≤ 20 mg/L (avg) |
| pH | 6–9 |
Contingency — Declining Disinfection Performance
E. coli Failure
| Control |
|---|
| Ensure ample chlorine supply on site |
| Confirm chlorine doser operation |
| Maintain chlorine dosing per manufacturer requirements |
| Confirm UV disinfection system operation |
| Clean UV glass sleeves using manual wiper |
| Replace UV bulbs annually |
TSS Failure
| Control |
|---|
| Clean out microfiltration cartridge |
| Ensure AdvanTex ventilation assembly operational |
| Review and adjust recirculation ratios |
| Ensure primary tank effluent filters in place and functional |
| Manage sludge/scum in septic tanks to prevent carryover |
See 3.2.15 Contingency Plans for full declining water quality response procedures.
Control Room
The microfiltration unit, UV system, chlorine dosing, flow meter, and T-COM control panel are installed inside a secure, climate-controlled 20 ft shipping container (repurposed MAC Water Treatment Plant container, fitted out by SCF Containers Berrimah).
The control room includes:
- Potable water supply with backflow prevention
- Sample collection tap
- Security cameras
- Work bench
Version Control
| Version | Date | Description |
|---|---|---|
| 2.0 | 2026-06-22 | Initial Release per O&M Manual V1.1 |
Next Review Date: 2026-12-22