Selecting water treatment approaches is a complex undertaking and can be quite confusing if it’s not something you’re familiar with. Sometimes, an analogy can be helpful to briefly explain complex concepts, so in this session, we are using the process of choosing and cooking potato dishes as an analogy to choosing and implementing water treatment technologies.  That’s right… for today’s topic, we are setting goals and defining questions for water treatment, all using potatoes as an analogy.

Start by Defining Success – what are you ‘ordering’?

We are frequently asked if a specific element or constituent can be treated with semi-passive treatment. Conceptually, the answer is often yes, but in reality, treatability depends on the site-specific chemistry, goals, and context. So, let’s start the potato analogy. You go to a chef and ask if they can cook you a potato. They say, of course they can, and they bring you mashed potatoes, but you wanted french fries. Would you be happy to pay for your order of ‘potato’? Would you consider this a ‘good chef’ even if it was the best mashed potatoes ever, but you didn’t want mashed potatoes? It’s hard to say for sure. But what’s clear is that without asking questions up front to defining a successful outcome (i.e., the potato form you want is french fries), you and the chef will have varying opinions on their degree of success in ‘cooking a potato’. In a similar way, semi-passive treatment can be effective for many constituents, but without a clear definition of success there is no way to be certain if it has been achieved. Many semi-passive systems have been said to have “failed” but largely due to not having clearly defined goals and objectives.

Set the Context – know your ‘ingredients’

Once goals are defined, the overall context of the situation is important. For example, french fries and potato pancakes require a different set of ingredients. The approach to cooking is also different. You cannot make french fries if all you have is a pot of boiling water. Knowing the goals and the context dictate the feasibility of water treatment systems. For example, copper can be treated in many ways. It can be treated as a sulphide, hydroxide, or carbonate mineral, be co-precipitated with iron, or removed by sorption. Just as your ingredients available influence what types of potato dish you can make, the context of the water chemistry and site-specific aspects will influence the types of treatment that are possible. This includes factors such as availability of land and other resources, planned end uses of the water, timelines to implementation, climate, and project lifecycle phase.

Experts are Experts, whether chefs or water treatment

Now, to take it one step further, if you talk to a really good chef, they know that the type of potatoes are an important factor in what you cook with them. For example, russet potatoes are better baked than as hash browns, and Yukon gold potatoes are a bit of an all-purpose potato, but some people might say they are better fried than mashed (HUGE disclaimer here… we aren’t chefs… this could be totally wrong, so please don’t follow this potato advice!). Knowing the specific varieties is important. Likewise, in water treatment knowing the form (speciation) of the chemicals present is important. For example, selenium can exist several different forms and all will require different treatment approaches to appropriately target the particular form. Typically, selenate removal requires a reductive process, selenite can be treated through reductive processes or through sorption to iron, while selenocyanate requires oxidation to selenate and/or selenite before follow-up treatment.

Putting it into practice

By asking questions to clearly defining goals up front, complexities of water treatment can become simplified. Much in the same way as a cookbook can help a novice to create delicious potato dishes without personally needing to know the complexities of each type, tools such as decision matrices help provide transparency to choices. Of course, there is a difference between following a recipe in a cookbook to make mashed potatoes for supper, and eating a meal prepared by a chef that contains potatoes. Your goals will help determine which is right for your situation at the moment. 

If you are interested in learning more about water treatment options and decision matrices, you can check out our mScout water treatment selection tool (and more info about it here). Bon appétit! (are you hungry for french fries yet?)