Pristine water source with seasonal quality fluctuations. Plan to upgrade capacity and researching all possibilities to include additional Microfloc package units and/or reverting to conventional plant set-up. Wondering if traditional flocculation/ sedimentation has limitations with low (<2.0 ntu) turbidity and low alkalinity (<12ppm). Microfloc units are working well 95% of time, but have limitations on the upper end of the turbidity (~50 to 100 ntu) we get due to seasonal rains / storms. Currently using Alum for coag, but open to others if switching to conventional plant.
Do you have filtration after the sedimentation step?
If that is the case you can bypass the flocculation and sedimentation units when times of very low turbidity and go directly to the sand filter units.
in theory, you can treat low turbidity and low alkalinity water with flocculation and sedimentation treatment, but you would have to increase the Alum dose a lot and add Soda Ash to have a good level of alkalinity. And the end you would get maybe 1 NTU. In those cases when you have turbidity lower than 10 NTU you can go to a San Filter and run to 8 hours without the need of backwashing.