Effects of temperature and pH on residual aluminum in alkaline-treated waters

The effects of temperature and pH on aluminum concentrations in alkaline‐treated waters were examined using laboratory and field data. Residual aluminum concentrations were measured in the effluent from the Van de Water treatment plant, Tonawanda, N.Y., over a one‐year period. Also, data from seven other treatment plants in the United States and Canada were compiled and analyzed. Raw water pH for the plants ranged from 6.7 to 8.4. Results showed that key factors influencing residual aluminum concentrations for the conventional treatment plants were pH and temperature. Trends in dissolved aluminum with temperature measured at the Van de Water plant were described reasonably well based on theoretical inorganic aluminum speciation with fitted values of pKs0=32.3 (infinite dilution) and ΔH0=15.9kJ/mole for Al(OH)3(s). Similar results were observed for three other conventional water treatment plants. Operationally, the effects of pH and temperature on residual aluminum can be described conveniently by pOH, whi...