Influent raw water

The effluent water from the hardness removal reactor is basic and tends to deposit scales in distribution pipes. For this reason, this water should be stabilized. Stabilization is normally done using carbon dioxide, a process called recarbonation. Stabilization using carbon dioxide affects the concentration of the bicarbonate ion in the treated water. The concentrations of the SO4, Cl and NO3 ions are not affected, however, because they do not react with carbon dioxide. Their concentrations remain the same as when they were in the influent to the treatment plant. The original cation Na from the influent raw water is also not affected for the same reason that it does not react with carbon dioxide. Na is, however, introduced with the soda ash. 

Typical Influent Raw Water Characteristics and Capacities of Seven Filtration Technologies for Water Treatment... 

These results have important implications for process control of solids/liquid separation processes. Because many suspensions in natural waters have particle size distributions with p > 3 (see Table II), presently available particle counters will not detect particulates that dominate the surface area concentration. Light-scattering devices may be needed to monitor the influent raw water supplies. However, if p values are less than 3 in effluent streams from solids/liquid separation processes, particle counters could be used for process monitoring and ultimately, process control. 

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