3.2.8 Effluent Disposal
This section details the Land Application Areas (LAA) for disposal of Class A recycled water via subsurface dripline irrigation, based on the LBC OWMS O&M Manual V1.1.
Legacy System Decommissioned
The previous Land Application Area — concrete distribution box feeding four plastic tunnel trenches (~140 m total) — has been decommissioned and replaced by the subsurface dripline irrigation system described below.
System Overview
Treated effluent from the WWTP is reused as a watering resource and irrigated via subsurface driplines installed across two designated irrigation areas. Distribution valves ensure even distribution of recycled effluent throughout the soil profile, eliminating the risk of over-saturation and runoff.
Manual isolation and automatic solenoids for the absorption areas are on the control-room distribution manifold. On Irrigation Area 2 (hill), each of the four sub-beds is also switched by a local solenoid with a Hunter NODE-BT (Node One) controller — see Sub-Beds and Hunter NODE Controllers.
| Parameter | Value |
|---|---|
| Technology | Netafim Bioline 17 pressure-compensating dripline (Thinkwater NT) |
| Pipework colour | Lilac (permanently coloured, per recycled water standards) |
| Design total area | 9,425 m² (plan cover sheet) |
| Operational area | 7,620 m² (see breakdown below) |
| Design Loading Rate | 3 mm/day DLR = 22,860 L/day allowable discharge |
| Daily max discharge (programmed) | 28,600 L (user-adjustable default in discharge tank logic) |
Dripline to Manifold Connection
Lilac dripline takeoffs leave the white PVC (or poly) manifold through a rubber grommet seal. A takeoff connector is pushed through the grommet into the manifold; the lilac dripper line is clamped onto the takeoff.
| Item | Detail |
|---|---|
| Grommet | Tavlit G16 — black rubber top-hat grommet for a 16 mm takeoff |
| Takeoff | 16 mm barb / start connector pushed through the grommet into the manifold |
| Clamp | Stainless ear / crimp clamp (Oetiker-style) pinched onto the dripline over the takeoff — not a worm-drive hose clamp |
| Dripline | Lilac Netafim Bioline (pressure-compensating recycled-water dripline) — estate LAA laterals |
Where to Buy (Darwin)
Primary supplier: Think Water Darwin — 7 Patsalou Road, Coolalinga NT 0839 · (08) 7980 8000 · salesdarwin@thinkwater.com.au · Contact. Authorised Netafim dealer; ask counter staff for these parts (order-in if not on the shelf).
| Part | What to ask for | Notes / reference |
|---|---|---|
| Grommet | Tavlit G16 rubber grommet (16 mm) | Reference listing elsewhere in Think Water network: Tavlit grommet take-off 16 mm OD — stock DFTGS16 |
| Takeoff connector | 16 mm barb takeoff / PVC start connector to suit G16 grommet | Must match the grommet; do not mix brands unless the supplier confirms fit |
| Crimp / ear clamp | Stainless single-ear (Oetiker-style) clamp for 16 mm dripline OD; crimped with pincer pliers | Ask Think Water Darwin for COBRA / ear clamps to suit 16 mm dripline. Reference: COBRA clamp 16.5–18.0 mm (16 OD drip) — stock GCC16-8 |
| Dripline | Lilac Netafim Bioline (or equivalent Netafim lilac recycled-water PC dripline) | Think Water Darwin — Netafim; match existing LAA spacing / L/h when replacing |
Match the set
Order grommet + takeoff as a matched 16 mm set. Drill hole size depends on manifold material (PVC vs PE) — follow the fitting maker’s sheet. Use lilac dripline only for recycled water.
Irrigation Areas
Irrigation Area 1
| Item | Detail |
|---|---|
| Total Area | 1,386 m² |
| Configuration | One field (Bed A), manually divisible into two nearly equal sections via red taps in the lilac valve box; blue tap serves front garden / forest irrigation |
| Drawings | Thinkwater AREA #01 (LAA A); as-constructed Sheet 3 of 5 |
| Site Location | Larger field north-east of Area 2, nearer Chinner Road, immediately downslope of the WWTP |
| Potable Makeup | Purple in-ground valve box beside the control room — see 3.2.13 Potable Water Valve Boxes |
Lilac Valve Box (Bed A)
Rectangular lilac in-ground irrigation box at Bed A / LAA A. Contains three ball valves:
| Tap | Colour | Isolates |
|---|---|---|
| 1 | Red | One half of Bed A (bed is split into two nearly equal sections) |
| 2 | Red | The other half of Bed A |
| 3 | Blue | Irrigation to the front garden / forest area of the property |
Bed A Isolation
Close either red tap to shut off roughly half of Bed A. The blue tap is separate — it isolates the front garden / forest irrigation, not a Bed A half.
Flow Direction on AREA #01 Design
On the Thinkwater layout, effluent enters from the southern edge (valves and pump) and distributes upslope through the dripline grid.
Construction of LAA A (2025)
Absorption Bed A was built in late October 2025. Construction photos are on a separate page so this operations page stays readable:
- 3.2.8.1 LAA A Construction 2025 — dripline layout, header, geotextile / grading
- 3.2.10.1 WWTP Construction 2025 — plant and RWS from the same programme
Irrigation Area 2 (Absorption Bed 2 / LAA B)
| Item | Detail |
|---|---|
| Total Area | 6,234 m² |
| Configuration | Four sub-beds on the hill, numbered 1–4 from top to bottom; each bed has its own solenoid |
| Controllers | One Hunter NODE-BT (Node One / 1-station) per sub-bed — battery Bluetooth controller on the solenoid, in a lilac valve box |
| Drawings | Thinkwater AREA #02 (LAA B); as-constructed Sheet 5 of 5 |
| Site Location | Four terraced beds on the hill south of the WWTP |
Sub-Beds and Hunter NODE Controllers
| Sub-bed | Position on hill | Control |
|---|---|---|
| 1 | Top (highest terrace) | Solenoid + Hunter NODE-BT (1-station / Node One) |
| 2 | Second from top | Solenoid + Hunter NODE-BT (1-station / Node One) |
| 3 | Third from top | Solenoid + Hunter NODE-BT (1-station / Node One) |
| 4 | Bottom (lowest terrace) | Solenoid + Hunter NODE-BT (1-station / Node One) |
| Controller | Detail |
|---|---|
| Make / model | Hunter NODE-BT (Bluetooth battery-operated; 1-station with DC-latching solenoid — NODE-BT-100 / Node One class) |
| Power | Battery (typically one or two 9 V alkaline); optional solar kit available from Hunter |
| Programming | Hunter NODE-BT smartphone app (Bluetooth, about 50 ft / 15 m line-of-sight) |
| Enclosure | Lilac recycled-water valve box at each sub-bed |
| Manual | Hunter NODE-BT product page |
Hunter App Names
Controllers are named in the Hunter app as A2-Bn = Absorption Area 2, sub-bed n:
| App name | Sub-bed |
|---|---|
| A2-B1 | 1 (top) |
| A2-B2 | 2 |
| A2-B3 | 3 |
| A2-B4 | 4 (bottom) |
Irrigation Schedule (Paired Beds)
Beds run in two pairs so only half the hill irrigates at once:
| Pair | Controllers | Schedule |
|---|---|---|
| Beds 3 and 4 | A2-B3 + A2-B4 | Same program — turn on together (times below; as in screenshot) |
| Beds 1 and 2 | A2-B1 + A2-B2 | Same as each other; alternating hours — opposite / offset by 2 hours from beds 3 and 4 |
Beds 3 and 4 — program 2/4 Hours (as recorded 2026-10-29 on A2-B4):
| Setting | Value |
|---|---|
| Water days | Every day |
| Start times (6 of 8) | 02:00, 06:00, 10:00, 14:00, 18:00, 22:00 |
| Station 1 run time | 2 h 5 min per start |
| Daily total (this program) | 12 h 30 min |
| Seasonal adjustment | 100% |
| Rain / soil sensors | Disabled |
Beds 1 and 2 — same run time and every-day pattern, but start times offset by 2 hours (alternating with beds 3 and 4), e.g. 00:00, 04:00, 08:00, 12:00, 16:00, 20:00.
On-Site Bed Numbering
On the hill, sub-beds are 1 (top) through 4 (bottom). The Thinkwater AREA #02 drawing may label Bed/Block 01–04 differently on plan (e.g. right-to-left); use the top-to-bottom numbering and Hunter names A2-B1…B4 when working on site.
Combined Total
7,620 m² operational irrigation area.
Area Discrepancy
The design cover sheet references 9,425 m² as the total permitted disposal area. The operational breakdown (1,386 + 6,234 m²) sums to 7,620 m². The design total includes the full permitted disposal area allocation.
Signage and Identification
Lilac recycled-water warning signs must be displayed wherever recycled water is used for irrigation — including the absorption beds (LAA A and LAA B) and any other irrigated areas (for example garden beds served by recycled water).
Wording on the estate signs:
RECYCLED WATER USED FOR IRRIGATION
DO NOT DRINK
(with the standard “no drinking” symbol)
| Item | Detail |
|---|---|
| Colour | Lilac / magenta (matches recycled-water identification) |
| Required at | All recycled-water irrigation areas — absorption beds and other zones |
| Spares | Stored in the WWTP control room |
All pipelines and fittings associated with the irrigation zones are distinctly and permanently coloured lilac.
Environmental Benefits
Subsurface dripline irrigation:
- Evenly distributes water throughout the soil profile, eliminating over-saturation and runoff
- Maximises evapotranspiration from vegetation planted within the garden beds
- Makes beneficial residual nutrients available to plant root-mass within the rhizosphere
- Prevents runoff and potential contamination of adjacent aquatic habitats (Lake Bennett)
Maintenance
Routine Tasks
| Task | Detail |
|---|---|
| Mowing/slashing | Periodic, as required |
| Weed control | Keep all irrigation areas clear of weeds — careful application of wick-type herbicides or mechanical means |
| Ponding checks | Check for pooling or ponding caused by possible dripline or pipework breakages; repair as necessary |
| Soil health | Twice-yearly checks of soil pH and conductivity |
| Low-occupancy watering | Deploy potable water irrigation during periods of low occupancy and/or when turf shows signs of heat stress or water deficiency — Absorption Area 1 via the purple valve box beside the control room |
Performance Indicators
- Turf is healthy and actively growing
- All irrigation areas display even coverage of turf with no lines or die-off
- Weeds are not present
- Irrigation areas are mowed and tidy
Maintenance Program (Table 1)
| Item | Task | Action | Frequency | Responsible |
|---|---|---|---|---|
| 3 | Mowing and groundskeeping | Irrigation areas | Weekly (or as required) | Site Caretaker |
| 8 | Turf health assessment | Check for pests, diseases, and growth inhibitors | Quarterly | ENVR |
| 20 | Leak and pooling inspection | Inspect all irrigation areas; repair as necessary | Quarterly | ENVR |
See 3.2.15 O&M and Contingency for the full maintenance program.
Wet Weather and Storage
When irrigation is not possible due to prolonged wet weather, treated effluent is diverted to the 3.2.14 Recycled Water Storage. If storage reaches capacity, engage McMinns Pumping Systems (0408 895 171) for licensed pump-out.
Version Control
| Version | Date | Description |
|---|---|---|
| 1.0 | 2025-10-06 | Initial Release (legacy trench LAA) |
| 2.0 | 2026-06-22 | Rewritten for subsurface dripline irrigation per O&M Manual V1.1 |
| 2.0.1 | 2026-06-22 | Added LAA Area A and B design and layout diagrams |
| 2.0.2 | 2026-06-22 | Corrected area presentation order and layout/design sequence |
| 2.0.3 | 2026-06-22 | Corrected irrigation area sizes, configurations, and site locations |
| 2.1 | 2026-08-30 | Linked control-room manifold for LAA isolation and solenoids |
| 2.2 | 2026-08-30 | Photo of Absorption Area A |
| 2.3 | 2026-08-30 | Photo of Absorption Area B |
| 2.4 | 2026-08-30 | Linked purple potable-water valve box for Absorption Area 1 |
| 2.5 | 2026-10-20 | Updated site photo of Absorption Area B (LAA B) |
| 2.6 | 2026-10-21 | Added Show on Map locate buttons |
| 2.7 | 2026-10-27 | Current site photo of Absorption Area A (LAA A / Bed A) |
| 2.8 | 2026-10-27 | Bed A lilac valve box — two red section taps, blue front-garden/forest tap |
| 2.9 | 2026-10-27 | Lilac recycled-water sign photo; spares in WWTP control room |
| 2.10 | 2026-10-30 | LAA B sub-beds 1–4 top-to-bottom; Hunter NODE-BT (Node One) per solenoid |
| 2.11 | 2026-10-30 | Hunter app names A2-B1…B4; beds 3+4 shown schedule, 1+2 alternating |
| 2.12 | 2026-10-30 | Hidden search aliases (LAA / absorption beds / NODE) |
| 2.13 | 2026-10-30 | Dripline–manifold takeoff; Tavlit G16 grommet photos |
| 2.14 | 2026-10-30 | AU purchase links — Tavlit G16 / 16 mm takeoff (Think Water, Perth Irrigation) |
| 2.15 | 2026-10-30 | Darwin-focused supply list: grommet, takeoff, clamp, Netafim Bioline dripline |
| 2.16 | 2026-10-30 | Clamp corrected to crimped ear / COBRA type (not worm-drive) |
| 2.17 | 2026-10-30 | LAA A construction gallery (Oct 2025 dripline / geotextile) |
| 2.18 | 2026-10-30 | Construction photos moved to 3.2.8.1 |
Next Review Date: 2027-04-30