The wastewater and drinking water worlds: two continents drifting towards each other

Since I entered the 'water sector' 10 years ago, I have been fascinated about the comparison between the 'drinking water world' and the 'wastewater world'. To me they seem like two continents: isolated enough to create an own culture and language, yet close enough for potential exchange. Throughout the years, I have been calling them the 'DOC' and the 'COD' worlds. Also some other worlds exist (please don't be offended by the size!),with potable water reuse in the middle. Some sub-cultures such as 'ground water treatment' and 'surface water treatment' or 'industrial' and 'municipal' wastewater treatment exist.

Different cultures

I would compare the languages with American and Brittish English: they can perfectly talk but some words differ. It was around 2012 when I discovered that some drinking water engineers had not heard about COD, while some wastewater engineers did not know what DOC was. I have a feeling that this has changed. Here's a small table with some (not all!) important drivers for cultural differences:

I do not know too many people that are fluent in both languages. Maybe you are?

The scheme below is from my PhD in 2012 (you can download it here if you're interested). It clearly visualises the connection between the continents. In 2011 for the first time I heard about the 'unplanned' or 'de facto' reuse. It made me realise that water reuse is not new at all, just looking at the effluent fraction in some of the rivers (very nice examples are the connection between Dallas and Houston, or the Netherlands being downstream of the river Meuse). I have always seen this as a big elephant in rooms where direct potable reuse is being discussed.

Fascinating is the difference in use of process models

Process modelling for treatment train design and process optimisation is culturally embedded in the wastewater sector, while it is not in the drinking water field. I guess this is driven by the dynamic character of both flow rates and loads in wastewater, while in drinking water only the loads may vary (while treating surface water). I have seen efforts in dynamic drinking water modelling, but the joint focus of the efforts and scale of their usage cannot be compared to those in the wastewater field. But I have identified three trends that might lead to more dynamic modelling efforts in the drinking water field:

1. DW treatment plants are more and more preparing for changing inlet quality (eg driven by climate change) and lower quality water sources are being used (for example: changing and increasing natural organic matter content)
2. The micropollutant concern, whereby the 'load' of them is highly dynamic. This only became visible around 15y ago
3. Direct and indirect potable reuse is growing rapidly, whereby WWTP effluent dynamics become of direct relevance (and this trend directly relates to 1) and 2),with in many cases the river being the connecting pipe)

Besides that: both are facing the same 'digital challenge'. Many people are equally confused by the speed of it, and ask themselves how it can help their utility. This gives a huge opportunity to collaborate more.

Every threat to the status quo is an opportunity in disguise, Jay Samit

Figure: a recent visit to a DW and WWTP on the same day

So what about the future?

I expect that both fields will come closer and closer, because it simply makes sense. Only a minority of the utilities treat both DW and WW, and I know quite some of these where inside this utility also both continents exist. The important trends discussed above cannot be stopped. Further, it would be very effecient if they could share their worries and experiences regarding the current digital revolution. Many of those questions are exactly the same.

Author: Dr. Wim Audenaert, CEO AM-TEAM