Objective: to protect public health by supplying safe, quality drinking water to our customers
Risk: the effect of uncertainty on objectives. (ISO 31000:2018)
The Australian Drinking Water Guidelines note that assessment of the drinking water supply system, including understanding its characteristics, sources of hazard and risks, is an essential prerequisite for subsequent steps in which effective strategies for prevention and control of hazards are planned and implemented. A water supply system can be defined as anything from source to endpoint – the components of this system depend on the type of water product or service being delivered, the specific processes involved, the interested parties in the supply chain and the required regulatory and formal requirements.
So, what is the best way to understand the risk for our objectives, how do we understand water supply system context for the risk assessment?
What does the Framework say?
Element 2 of the Framework for Management of Drinking Water Quality calls for development of a flow diagram to be constructed from catchment to consumer:
“Effective system management requires, first and foremost, an understanding of the water supply system from catchment to consumer.”
In my auditing experience, the implementation of this area of the Framework (along with articulation of critical control points), is often the one which requires most improvement.
I’ve already got P&IDs – that’s enough isn’t it?
Piping and instrumentation diagrams (P&IDs) are often provided to the auditor as a means of meeting Element 2 of the Framework. These diagrams are usually developed for the planning and construction phase of a facility and in our experience, may not been reviewed since commissioning. We’ve all seen the facility that has had upgrades or other modifications, which haven’t been adjusted on the P&ID or the facility which supposedly had been checked and signed off by the engineer but in the audit walk through, differing connections, plumbing idiocy to meet quantity rather than quality outcomes, lack of reservoir integrity, or process bypasses, are uncovered. All of these items have a huge potential to create uncertainty on your objectives as a utility – without the discipline of verifying the flow diagram, they are not uncovered in a timely manner, and leave you exposed. So, no, P&IDs are not usually a good way of meeting the Framework, and nor, more importantly, of protecting your customers.
Why do I need to include things that aren’t my responsibility?
For this question, I always go back to Element 1 of the Framework and ISO 31000. Both state the importance of understanding the interested parties as a potential source of risk. Parties may introduce risk, you might introduce risk to those parties, or parties may perceive that you are passing on a risk to them. Additionally, Element 2 of the Framework calls for you to identify all steps and processes in your diagram, regardless of whether they are under your control. In other words, you need to understand the governance of your water supply system.
My checklist
So what makes a good flow diagram – one that will not only satisfy the requirements of Framework compliance, but actually deliver you tangible risk understanding and management benefits? My checklist and outcomes for a good flow diagram would look something like those in Table 1 and Figure 1.
Table 1. My checklist and tips for a good flow diagram.
| Check point | Tips |
| Is the diagram generalized? | Ideally the flow diagram will have been prepared for the purposes of the risk assessment and include simple and logical flows. Process flow symbols used in HACCP are helpful but not essential. It’s more important to get the process right. |
| Does the diagram describe the system from catchment to customer? | You must include where you are getting your water from and make clear where the water is going to – the source to endpoint information. |
| Does your diagram include all steps and processes, whether or not they are under your control? | Make clear on your diagram what the handover points are. Ideally, where you have formal agreements, detail these at the relevant part e.g. a water extraction licence or an environmental protection licence or a water supply agreement with a downstream user or upstream provider. We’ve seen examples where water can be supplied in a bi-directional manner between two suppliers – these arrangements need to be shown on the diagram. |
| Have you adequately characterized the basic components of your system? | You should have the basic process components adequately described in your flow diagram. If there are areas of your flow diagram that are starting to get too complicated, it’s perfectly OK to develop a supporting flow diagram for that component, and identify where it fits on the overarching flow diagram. A good example of this is to have an overarching source to endpoint flow diagram with a single process step for treatment – and then expand treatment in a separate flow diagram. |
| Have you made the specific characteristics of your system explicit? | What I would expect to see, as well as the basic process components, would be things that help to clarify risk such as non-potable systems (many areas have raw water reticulation systems which, if cross-connected, could cause public health risk), chemical inputs (e.g. hypochlorite or soda ash), supernatant returns, sources of water for backwash and chemical dilutions, bi-directional flows (intra- and inter-utility), bypasses and CCPs. |
| Have you verified the flow diagram? | The flow diagram should be checked and signed off by those with appropriate knowledge of the system. Someone should be formally assigned an authority for sign off on the accuracy of the flow diagram. A record (on the diagram or somewhere in the document history) should be kept of the ‘when’ and ‘who’ changes and the flow diagram should have sound version control. I often see flow diagrams actually in the drinking water management plan document. This practice is not so onerous for smaller systems, however, to be more nimble (and stop your plan from becoming a monster!), it may prove easier to have an overarching system flow diagram in your plan and then just reference the individual, supporting flow diagrams. This way, you don’t have to keep going back to the regulator with a change to the DWQMP, every time the diagram is changed. The auditor will be able to check the diagrams referenced in the DWQMP. |
| When did you last review the flow diagram? | Ideally you will have a trigger for review of the flow diagram such as cyclical review, on system change, before proposing system changes, after audit findings and/or at each risk review. For each review, it should be undertaken by those with the appropriate system knowledge to undertake the review, sign off the changes and maintain a record of the changes as an audit trail. |
So, the next time you think your auditor is being pedantic on the flow diagram, it’s not just your compliance, their diligence is helping you deliver on your objective: to protect public health by supplying safe, quality drinking water to your customers.
Need help? Risk Edge and D2K Information profoundly know water. We can assist you with system assessment, water quality monitoring technology and information, tailored for your context. Our aim is to provide well-designed and executed water quality monitoring, information and system optimisation solutions. Learn more here.
BIO:
Annette Davison, Director and Principal, Risk Edge Pty Ltd; Director and Chief Risk and Product Officer, D2K Information Pty Ltd