Sewage Pump Design Question

What are the wetted materials?

Check your typing. It appears some info go missed. What percent of vegetable oil?

My first guess is no effect, other than possible oil separation in the wet well. Who will you be pumping this too? Will they accept oil as is, or will they require some type of OWS? What does your pump supplier say?

You don't actually say what percentage of vegetable oil will be pumped. You say less percent but that really doesn't mean a whole lot.

The easiest way to find out is by calling the pump manufacturer/supplier. They will be able to tell you straight up.

Your alternate solution would be to install a oil intercepter mechanism upstream of the wet well to separate the oil before it reaches the pump.

I am sure tho that you can get a pump that is not going to be affected by the oil.

Your specific gravity will be less with X % of oil and power consumption will be less if it is a light non viscous vegetable oil, however, the viscosity of the mix may increase if the oil is very viscous which robs efficiency of any centrifugal pump (power consumption goes up). No change in mechanical seal with low viscosity oil, but if the pumped mix is above 200 cP you will need hard faces to prevent seal face pullouts from the viscous 'glue' during startup pulling out bits of soft seal face.

A well designed sewage pump is indifferent as to the presence of absence of oils in the sewage.

Raw sewage entering the plant passes through grates to remove gross sized items, a comminutor that grinds/cuts any solids into small bits, and then to a separator tank where any oils float to the top to be skimmed off and solids to the bottom to go to the digestor tanks.

If you have to handle a large percentage of oil, then you may need another preliminary means to deal with the oil.

Hard faced mechanical seals wont be affected by vegetable oil unless they include contaminates that could cause gumming of the oils on the seal faces. However if you are pumping effluent with vegetable oil into the municpal sewage system you could end up in big trouble. Authorities require that oils and fats be removed at source as they affect the operation of STPs and are a serious pollutant to the environment. If you can see the oil in the sewage then you shouldnt be discharging it to the sewage system. Seperate it and use it for biodisel or whatever.