WEF Discussion Forums
Operation and Maintenance
chemical phosphorus removal using alum
i am looking for some basics on beginning phosphorus removal using alum.
i am working with a small state park facility that gets loaded heavy on weekends - especially from RV dump station wastewater.
chemical addition point is in mixing zone of final clarifier
i think i need basic help on determining the starting point for chemical
addition. using alum is the beginning dosage for an influent of ~ 8 mg/l P in the raw. chemical feed pumps are oversized and the alum has been diluted in order to maiintain prime on the pumps.
the effluent limit is 1.0 mg/l
while i could simply give it more alum i would like to understand the chemistry of where to start and how to calculate the proper dose and feed rate.
appreciate any guidance and direction
A good starting point would be to run a series of jar-tests on your mixed liquor to determine the optimum dose of chemical. If you don't have experience running jar-tests and/or the jar-test equipment is not available, you have a couple of options. 1) Contact another wastewater treatment plant or water treatment plant in your area to see if they can bring their jar test equipment (if they have it) to your location and conduct a few tests. Note: Would advise against taking samples to their location as physical properties of the sample could change during transport. 2) Contact a chemical supplier and ask them to come to your location w/ their jar tester. Most will do this at no charge. Also, while they are there, you should have them evaluate (in addition to the Aluminum Sulfate) alternative chemicals including Aluminum Chloride, Ferric Chloride, Magnesium Chloride, and Polyaluminum Chloride. One may work better than the other at an overall lower cost, particularly if you currently have to feed a chemical to raise ph/alkalinity. If you run into dead-end on both of these options, respond back and I can walk you through conducting a simple version of a jar-test that will help get you to where you want to be. I've been through this many times as part of plant start-up's and troubleshooting.