Problem: The pH in the final effluent of the activated sludge plant is below permit values. The facility uses gas chlorine as its disinfectant and does not de-chlorinate. The chlorine dose and residual are normal and the effluent is clear. What is causing the low effluent pH? • Low alkalinity due to excess DO in the effluent • Low alkalinity due to nitrification in aeration basins • Denitrification increased the alkalinity too much • Denitrification reduced the alkalinity too much