By control of such floway operating conditions as water flow rate, light level, intensity and wavelength, water surge rate, recirculation rate, and nutrient concentrations, the pH of the water adjacent the algal cell wall is caused to increase to {TAIL ~ a level} at which {HEAD ~ the desired pollutants} precipitate 
at precipitate
By control of such floway operating conditions as water flow rate , light level , intensity and wavelength , water surge rate , recirculation rate , and nutrient concentrations , the pH of the water adjacent the algal cell wall is caused to increase to { TAIL ~ a level } at which { HEAD ~ the desired pollutants } precipitate
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