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Scenario · Water Treatment

Investigate turbidity breakthrough on filter 3

You are a water treatment operator assigned to investigate a filtration critical control point excursion.

Intermediate3 to 5 hours8 tasks
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The situation

What has happened

Filter 3 at the Kialla plant has twice this week returned from backwash at 0.26 NTU after 20 minutes on filter-to-waste, above the alert level of 0.2 NTU, and has taken almost 50 minutes to ripen below 0.1 NTU. The other five filters ripen within 15 minutes. Raw water turbidity has risen after rain and the coagulant dose was increased on Monday. Filter 3 had its media topped up in July. The event is logged in the incident register at Under investigation and the Water Treatment Manager wants an investigation report with recommendations before the weekend, and confirmation that no water above the critical limit reached the clear water storage.

Your brief. Investigate the repeated turbidity breakthrough on filter 3 using the online data, backwash records, coagulation data and a physical inspection, confirm whether the critical limit was breached, identify the likely cause and recommend corrective actions and any changes to the register or procedure.
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Tasks

Deliverables

  • Data review showing filter performance against the critical control point limits
  • Backwash and coagulation review notes
  • Filter inspection record and bench test entry
  • Updated incident register entry
  • Investigation report with recommendations

Documents to use

Systems to use

Water Quality Sampling Register

Records operational and verification samples, laboratory results and the result status for drinking water, recycled water, effluent and raw water.

WHS and Environmental Incident Register

Records injuries, near misses, hazards, chemical releases, sewage spills, water quality incidents and vehicle events with investigation and actions.

Network Work Orders

Tracks every reactive and planned job on the water and sewer networks, plants, storages and channels from dispatch to completion.

For trainers and assessors

Units of competency

Current on training.gov.au for the National Water Training Package as at 10 September 2026.

NWPTRT019Operate and control granular media filters
NWPTRT009Operate and control coagulation and flocculation processes
NWPNET030Identify and respond to water quality problems
NWPTRT059Assess and improve granular media filters
NWPGEN029Contribute to continuous improvement of quality systems

Qualifications

NWP30222Certificate III in Water Industry Operations
NWP40120Certificate IV in Water Industry Operations
Assessor notes

What to look for

Evidence guide

Look for the student separating the alert level from the critical limit and stating clearly whether treated water above the limit reached storage. The investigation must use the data, the backwash records and a physical inspection rather than a single explanation. Recommendations must be specific, for example a changed filter-to-waste duration or a media inspection, and the incident register entry must be updated to match the report.

The student's evidence summary lists every record they created or changed in the systems named above, their notes and the tasks they ticked. Verify it against the deliverables and your own assessment tool.