Operational solution of low pH
If the influent pH is low (acidic), there is more likely that the
condition will go through the package and show-up in the effluent.
Chemical addition to increase the pH is the immediate solution.
Lime, soda ash, or sodium bicarbonate is normally used for pH
adjustment. However, the ultimate solution is to eliminate the
source of low pH from the system by providing pretreatment requirements.
If the influent pH is in the standard range, then the low
effluent pH is usually caused by nitrification in combination with
low natural alkalinity in the wastewater. If ammonia removal is
required, then nitrification must continue. Use of on/off aeration or
provision for an anoxic zone often returns enough alkalinity to
satisfactorily raise the pH. However, if neither of these is possible,
then pH adjustment may be required. Ammonia-adsorbing zeolites
can be added to the aeration tank to control the discharge of
ammonia while nitrification is reestablished (