Improvement Planning: Choosing Additional Cyanotoxin Control Measures For System Improvement

If the outcome of the risk assessment identifies that high-priority risks are not adequately managed, then upgrade of exiting controls and/or additional control measures are needed. These actions are typically documented in an “improvement plan”, which should capture which improvement is needed, who is responsible for doing it, by when should it be done (i.e., reflecting its priority) and how the improvement will be funded.

Measures to control the risk of human exposure to cyanobacterial blooms range from simple physical interventions like vegetation buffer strips around a waterbody, or behavioural ones like banning recreational use of a water- body, to more complex technical interventions like the implementation and use of appropriate drinking-water treatment trains. Examples of additional control measures to consider at the different stages of the water-use system are provided in Chapters 7-10, and for the three scenarios, they are presented in Table 6.7.

Monitoring the Functioning Of Control Measures For Cyanotoxin Management and Developing a Management Plan

Validation determines that a control measure is fundamentally capable of controlling a hazard/hazardous event (see section 6.2.3). However, to determine that the control measure actually does continue to function effectively over time, routine monitoring is required (referred to as “operational monitoring”). This will show whether the control measure is reliably managed/ operated such that it continues to provide effective protection. Ideally, operational monitoring should use quick and simple monitoring parameters (see below) that provide a rapid result so the performance of a control measure can be continuously determined, and if necessary, corrective action can be taken in an efficient and timely manner.

Operational monitoring also requires setting performance criteria for the respective control measure and critical limits which indicate if the measure is working within the established acceptable performance criteria. Furthermore, it is useful to define corrective action(s) to be taken if the monitoring shows that the control measure is no longer working within the critical limits. For example, for filtration to remove cyanobacterial cells in drinking-water treatment, turbidity, measured continuously at the outflow of each individual filter, is a simple operational monitoring parameter that indicates whether filtration is working optimally. Critical turbidity limits can be set, and if they are exceeded, this would indicate that the filtration processes are not operating optimally, triggering, for example, filter backwashing as the corrective action to restore optimal operation of the control measure.

This approach can be similarly applied to control measures in catchment or offtake management; for example, vegetation cover to prevent erosion from catchment areas identified as critical for the nutrient load to the waterbody can be defined as control measure, compliance to which can be monitored either by remote sensing or by periodic site inspection. If such monitoring detects violation, corrective action would be an immediate enforcement of revegetation and compliance to the dedicated land use. Likewise, adjusting the drinking-water offtake depth to avoid cyanobacterial intake can be defined as a control measure with online monitoring of

Table 6.7 Three example settings: additional measures to control cyanotoxin risks and their operational monitoring identified through WSP development

Examples of settings

Additional control measures and their operational monitoring identified for each of the three settings

1: Slow-flowing large river serving as raw water source for a town of 500 000 inhabitants

Implement Alert Levels Framework; install an online fluorescence analyser to indicate when cyanobacterial levels are >1 pg/L at raw water intake to trigger microscopy for cyanobacteria; incident response plans to be developed as part of an emergency response.

Upgrade the drinking-water filtration system in the treatment train (see technical specification for details) to ensure an effective cell removal avoiding rupture and lysis (note: this will also reduce risks of breakthrough of disinfection-resistant pathogens).

For operational monitoring: install online turbidity analyser (with corresponding “auto dial" alarming for operator notification) at the outlet of each filter.

2: Reservoir serving about 7000 people (three villages and a number of farms)

Any investment into treatment targeting cyanotoxin removal may well prove futile; as a first step, gain the necessary data via the university collaboration described in Table 6.1; decide on appropriate control measures only after the data are available.

3: Farm dugout serving as water source for 20-50 people

Plant a vegetation buffer strip of 10 m between the uphill pasture and the dugout (this likely represents a sufficient intervention to reduce loads from erosion; note: this will also intercept particles like pathogens, reducing infection risks).

Encourage farm inhabitants and farm workers to continue to drink bottled water, to ensure children understand this, and to use packaged water for food preparation.

Replace the filtration device in the kitchen by one with a carbon cartridge with regular renewal following the manufacturer’s instructions.

Ensure children understand the need to avoid swallowing water when using the dugout for recreation and to keep out of scum.

Advise to water the vegetable garden via the soil rather than causing direct water contact with produce.

Operational monitoring of the vegetation buffer strip through visual inspection - annually by the public authority responsible for oversight, by the farmer herself at monthly intervals as well as during and after stormwater events to look for traces of erosion and for immediate repair of any damage.

Operational monitoring of behaviour by spontaneous random household surveys of people on the premises during inspections to check their awareness.

a characteristic cyanobacterial pigment, phycocyanin, with a specific fluorescence probe as a means of operational monitoring. Critical fluorescence limits can be set, and if they are exceeded, this would inform managers that they need to take corrective action by switching the offtake to a different depth or site, or temporarily ceasing raw water harvesting.

Operational monitoring aims to ensure that the water-use system is “proactively” managed to avoid human exposure to unsafe water (e.g., containing cyanotoxin concentrations exceeding the guideline values or prevailing national standards). Proactive management can thus be far more effective (and less costly) than reacting to water quality issues after they have arisen. Additionally, operational monitoring is more practical and cost-effective than relying primarily on cyanotoxin monitoring. Evidently, by the time violation of a land-use plan has led to cyanobacterial blooms that show up in cyanotoxin monitoring data, “fixing the problem” has become far more difficult. Similarly, by the time cyanotoxin monitoring data show that the water quality target for finished drinking-water is exceeded, the water has already reached the consumer, whereas routine process monitoring would indicate the development of the problem (e.g., declining filter performance) with time to fix it before it leads to high levels of toxin concentrations. Chapters 7-10 therefore include text and tables suggesting the selected examples of control measures that can be implemented for the respective targets as well as operational monitoring parameters that indicate whether the measure is working as it should.

Beyond their use for day-to-day operation, the data documented from operational monitoring of control measures can be highly valuable for system and risk assessment, as they may also indicate/validate how effectively a control measure is working. Documentation also supports the identification of trends over time and of conditions that may impact the efficacy of control measures (such as patterns of precipitation or drought).

Furthermore, a management plan should be developed which defines how the performance of key control measures is monitored and which corrective action should be taken if monitoring indicates poor performance, or if incidents occur (typically referred to as “operational monitoring plans”, which may be part of standard operating procedures, SOPs). Operational monitoring plans for key control measures are important to ascertain their reliable performance at all times. These specify:

  • Operational monitoring parameters for key control measures. An important criterion for the choice of the monitoring parameter is that it gives a result with sufficient time for taking corrective action before failure leads to cyanobacterial proliferation or cyanotoxin breakthrough and exposure.
  • Documentation of data from operational monitoring: For each operational monitoring parameter, it is important to keep records of the monitoring data collected in order (i) to be able to trace what went wrong and why in cases of incidents or to validate that the system was working well even when excessively challenged, for example, by a bloom, (ii) to allow the recognition of trends in the data which may indicate a decline in the performance of the control measure (e.g., gradual reduction in filter runtimes at a water treatment plant over time may indicate that the filter media needs replacing) and (iii) to demonstrate due diligence in managing the system.
  • • Critical limits for each of the monitoring parameters that show operators when the system is “out of bounds” and corrective action needs to be taken on time.
  • • Corrective action(s) to take immediately in case monitoring shows a process to be outside of the critical limits, that is, performance criteria are not being met, including lines of responsibility and communication.
 
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