How can I have an effluent ph 3 in an extended aeration package plant?
If the nitrogen to organic ratio is high and there is no denitrification step, you can land up with a very low pH. At some of the treatment plants that we have built for roadside effluent treatment we have observed extremely low pH readings. In some instances we treat effluent that has ammonia concentrations of more than 150 mg/l. If there is enough aeration, the ammonia levels come right down. The process gets out of balance though when there is not enough organic material to denitrify the nitrates to nitrogen gas. Denitrification raises the pH. In many sewage treatment plants, the nitrification/denitrification unit processes maintain a constant and fairly neutral pH. We have sometimes measured pH values of less the 3.0 in the treated effluent. (http://hwt.co.za/sewage-treatment/gallery/hwt-bioreactor-snapshots/)