Potable water reuse was the central theme during this conference, recognizing the existing ‘de facto’ reuse of wastewater discharged on rivers and lakes, and intentional indirect and direct water reuse schemes.
The microbial view on water
Eleven years after my first WQTC, the American water industry seems to have made major steps forward in water safety and sustainability. Potable water reuse was the central theme during this conference, recognizing the existing ‘de facto’ reuse of wastewater discharged on rivers and lakes, and intentional indirect and direct water reuse schemes. New approaches and technologies are applied to achieve this, addressing water quality monitoring, treatment and the effect of processes in the distribution systems. Automated microbial analyzers provide a virtually real-time view of the level of contamination in the source water and even treated water and is used for both research and operation. Quantitative microbial risk assessment (QMRA) forms the basis to design the required treatment from the largest communal facilities down to local decentralized remote water reuse. This solves both the issued of water shortages and wastewater disposal. Especially in reuse attention is paid to preventing microbial growth in the distribution system to avoid risks from opportunistic pathogens such as legionella.
From sterile to living water
Although chlorination is still the principal approach to keeping drinking water safe, the water in the distribution system is now increasingly recognized as a living microbial environment. This community is constantly evolving and adapting to local conditions. Genomics are shedding new light on these bugs, and putting chemical stress on them may lead to selection of more resistant types, creating bigger problems for water safety. Many discussions were held over this survival of the fittest, including the adaptation of us as humans to these new stresses. It seems we are moving into a new era where we (again) work with nature rather than against it to achieve safe water. Nature was abundant at the excursion in the Bull Run watershed. Natural processes and protection are the key to achieve safe, wholesome drinking water for Portland from this unfiltered water supply. Although filtration will be implemented to deal with the current concern around protozoa in the water source, the impact of treatment can be kept minimal as the starting point is actually drinking water.
I wonder if in another ten years this concept of protection and natural processes will extend to abandoning chlorine in the distribution system. I got many questions about the Dutch Secret of chlorine-free distribution, so who knows?