Automating Chemical Phosphorus Removal in Real Time

摘要

After receiving a new effluent permit with a 1.0 mg/L total phosphorus average monthly limit,the staff at the Hutchinson, MN wastewater plant concluded the only way to meet this limit wasby using chemicals and precipitating the orthophosphate with their existing treatment system.Due to extreme swings in the influent phosphate concentration causing effluent values higherthan the limit, the staff decided to implement an automatic chemical dosing system to react to theinfluent phosphate swings in real time. Before the real time control system was implemented,staff fed as much chemical as possible in order to meet their effluent target—sometimes as muchas eight times the amount of chemical actually needed. After the system was installed, only theamount of chemical needed to achieve the set point was fed, reducing chemical consumptionapproximately 88%, and large swings in the effluent total phosphorus concentration have beeneliminated.