Investigate turbidity breakthrough on filter 3

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

Simulated workplaceIntermediate missionCAQA ClearFlow Water

What is going on

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.

Tyler Moloney, Water Treatment Plant Operator
Subject: Filter 3 turbidity after backwash

Filter 3 came back from backwash this morning at 0.26 NTU after 20 minutes on filter-to-waste, which is above the alert level, and it took nearly 50 minutes to settle below 0.1. It did the same thing on Tuesday. I have logged it in the incident register and extended filter-to-waste, but Anjali wants a proper investigation before the weekend. Can you take it on? Look at the backwash sequence, the media and the online turbidimeter data, check the Critical Control Points Register for what the limits actually require, and write up what you find with recommendations.

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.

Work through it

You do not need to do it all. Doing a few of these will show you what the work is like. Your ticks and notes stay on this device.

Read the filtration critical control point entry in the Critical Control Points Register and the Drinking Water Quality Risk Management Plan sections on hazards and monitoring, and state the alert level, critical limit and corrective action that applied.
Review the online turbidity data for filter 3 and the other filters for the last seven days and confirm whether any filter-to-waste or filtered water exceeded the critical limit and reached the clear water storage.
Review the backwash sequence for filter 3: air scour and water wash rates and durations, bed expansion and the filter-to-waste duration, and compare with the plant standard.
Review the coagulation data, jar test setpoint, settled water turbidity and the coagulant dose change on Monday, and consider whether upstream conditions explain the ripening time.
Inspect filter 3 during a backwash for media boils, mud balls, uneven expansion and media depth, with Tyler Moloney, and record your observations.
Take a bench turbidity test from the filter 3 outlet during ripening and enter it in the Water Quality Sampling Register with the correct result status.
Update the incident register entry INC-26-119 with your findings, the likely cause and recommended corrective actions with owners and dates.
Write a two-page investigation report for the Water Treatment Manager recommending any change to the backwash program, the filter-to-waste duration or the register limits.

My notes: what did I enjoy, and what surprised me?

What someone in this role would produce

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

Printing this is a record of what you explored. It is not a certificate or a qualification.