9.4.5 Operational monitoring frequency

Operational characteristics throughout the system should be monitored often enough to reveal any failures and trigger a response within a timeframe that is appropriate to how critical the monitored activity or process is. This applies to both measurements and observational monitoring. Online and continuous monitoring should be used wherever possible, particularly at critical control points. For operational characteristics that are deemed less critical or are more stable, grab samples or regular inspections may be sufficient.

Frequency of observations may be increased at times of increased risk; for example, inspections of reservoirs for algal blooms may be more frequent during summer, or floc blanket observations during the coagulation process may be increased when there are higher flow rates through the treatment plant.

Operational monitoring requirements and frequency of monitoring will vary for each water supply, depending on the key characteristics identified through analysis of the water supply system and risk assessment. Table 9.2 provides an example of how selected operational characteristics can be used within a catchment-to-consumer operational monitoring program.

Table 9.2 Example of an operational monitoring program (characteristics and frequencies)

Location	Characteristic	Monitoring frequency	Rationale
Catchment
General catchment	Rainfall	Daily	Understand impact of rainfall on water quality – to help predict challenge under range of rainfall intensity.
	Inspection	Monthly -> Daily Frequency depends on level of access and use permitted in catchment.	Detect human and animal activities that could cause contamination; confirm that fences and signs are effective.
Feeder streams in catchment	Turbidity Colour E. coli	Monthly plus events	Early warning of changes to raw water quality to allow timely changes to treatment processes. Detect local contamination and disturbances.
	Cryptosporidium	Risk-based	Assess if treatment barriers are needed to effectively remove or inactivate Cryptosporidium.
Source Water
Storage dam or raw water reservoir	Temperature Profile Dissolved oxygen profile	Monthly -> Weekly	Information for management of water quality in storage with existing or new management systems.
	General water quality profile	Weekly -> Event based	Allow best quality water to be selected for supply.
	Inspection	Weekly	Detect human and animal activities that could cause contamination.
	Algal cell counts	Monthly -> Daily Risk-based	Early warning to activate management actions to prevent algal blooms in storage and forewarning of need for additional monitoring, observational surveillance. Information for changes to water treatment processes in order to maintain effective removal of algae and algal metabolites.
	Cryptosporidium	Risk-based	Information for changes to water treatment processes in order to maintain optimal Cryptosporidium removal.
	Turbidity Colour	Continuous Weekly -> Event based	Information for changes to water treatment processes in order to maintain optimal turbidity and colour removal.
River intake	Rainfall	Daily	Understand impact of rainfall on water quality to help predict challenge under range of rainfall intensity.
	Inspection	Weekly -> Daily	Detect sources of contamination and activities that could cause contamination.
	Turbidity Colour	Continuous Weekly -> Event based	Inform changes to water treatment processes in order to maintain optimal turbidity and colour removal.
	Iron Manganese	Weekly (risk-based)	Inform changes to water treatment processes in order to maintain optimal iron and manganese removal; forewarn of water quality that may cause customer complaints.
	Algal cell counts	Monthly -> Weekly (risk-based)	Forewarn of possible algal risk and need for additional monitoring, observational surveillance.
	Cryptosporidium	Risk-based	Inform changes to water treatment processes in order to maintain optimal Cryptosporidium removal.
	Turbidity, E. coli Enterococci Cryptosporidium Pesticides Colour	(Rainfall-related monitoring) Risk-based	Understand rainfall effects. Identify high challenge periods and forewarn downstream processes; identify local point source of contamination. Intervene in catchment before reservoir affected. Feedback to industry and source of contamination.
Treatment Processes
Coagulation (inlet to flocculation tank)	pH	Daily -> Continuous	Optimise pH for effective coagulation of selected coagulants when raw water quality changes. Provide alarm if pH is outside set limits.
Flocculation (last compartment)	Floc characteristics	Daily -> Event based	Optimise floc characteristics for effective clarification or filtration when changes occur to raw water quality or operating conditions.
Clarifier (clarified water outlet)	Turbidity Colour	Daily -> Continuous Daily -> Event based	Confirm coagulant dose, pH correction, flocculation and clarifier operations are optimised when changes occur to raw water quality or operating conditions. Provide alarm if turbidity is above set limit.
	Visual observation of floc or floc blankets	Daily -> Event based	Assess if adjustment needed to process to improve stability of clarification process.
Filtration (Individual or combined filtered water)	Turbidity	Continuous	Provide alarm if filtrate turbidity is above set maximum. Trigger for initiating filter cleaning.
	Filter Headloss	Continuous	Trigger for initiating filter cleaning to avoid turbidity breakthrough.
Filtration (Combined filtered water post pH correction)	pH	Continuous	Confirm target pH range is maintained. Provide alarm if pH is outside target limits for effective disinfection and corrosion control.
	Aluminium (If aluminium-based coagulant used)	Weekly	Assess inadvertent carry-over of aluminium from sub-optimal flocculation pH.
Chlorine Disinfection (Chlorine >30 minutes after chlorine injection)	Free chlorine residual	Continuous	Provide alarm if chlorine residual is outside set limits for maintaining integrity of water quality during reticulation and for reticulation hygiene.
UV Disinfection	UV dose rate	Continuous	Confirm UV system is operating satisfactorily. Provide alarm if below minimum set dose.
Fluoridation (Downstream of fluoride dosing)	Fluoride	Daily Continuous (if provided)	Confirm target dose is maintained. Provide alarm if fluoride is outside set limits.
Distribution System
Disinfection (At various locations in the reticulation system selected by careful monitoring design)	Chlorine residual	Continuous -> Daily	Confirm total chlorine target or free chlorine residual target range are achieved.
Service Reservoirs and tank	Integrity from contamination	1 to 5 yearly	Confirm roof/hatches are effective against ingress of contaminants.
Consumers	Customer complaints	Ongoing	Clusters of complaints of turbidity, objectionable taste and odour, illness allow investigation to identify cause(s) of water quality problems.