High Phosphorus in Wastewater

[Chris73]

Hi Eng's,

how can an unusual high P level in a treatment plant influent cause harm to the plant's operation? Can high P upset the plant? Which levels are critical for extended aeration plants with no advanced treatment? What's the solution? Pricipitation prior in the equalization tank? Thanks!

 

[bimr]

A phosphorus concentration of 15 mg/l is considered to be a strong concentration in municipal wastewater and would have no effect on an extended aeration plant.

My conjecture is that phosphorus concentrations 2 to 3 times higher would also have no effect.

The common approach to phosphorus removal is to precipitate the phosphorus with alum after biological treatment.

 

[Chris73]

Hi bimr,

I haven't seen the official results yet but the lab said that P would be in the 60 - 70 mg/l. That's a lot but could it cause the following problem: the plant does not build up any biomass - virtually clear of solids although reseeded a few times. pH and DO are ok and the plant used to perform well before a restaurant was hooked up. So I took a sample from the restaurant flow and it shows the unusual high P level (probably dishwasher?). But could that do it? I have some more test coming: TKN etc. I post the results once they are in. Thought that somebody may have come across a similar thing before.

 

[bimr]

I don't think the phosphorus is a likely cause of failure to build biomass.

You are probably going to end up spending a lot of money on lab work for little benefit. You already know that the restaurant is a problem, what is the additional lab work going to get you?

You should just be proactive and talk to the restaurant and have them move to a low phosphate detergent, install a fat trap (grease trap) if they don't have one already, and maybe ask the restaurant to try to prevent heavy solids such as carrots from going down the drain. You can tell the restaurant owner that if they don't cooperate, they will end up spending lots of money to put in their own wastewater treatment system.

It is much cheaper to not put the phosphate into the water than to try and precipitate the phosphorus out at the end of the plant.

If the wastewater treatment plant capacity is adequate for the restaurant's organic loading, that is all you have to worry about.