agitator to support sludge pump

Hi all

we cut granite and have a pit for the waste water(with fine particles of granite slate marble limestone quartz) flowing into a pit 2 x 1.5 x 2.5deep [m]. The pit is flat at the bottom. we have a pump which pumps that waste up into a silo which is then filtered and seperated. 

The pit with slurry/sludge is getting clogged up with it all time so i am looking to do:-

1. agitator which will constantly disturb the particles in the water

2. build bottom with angles on 4 sides so the slurry can be directed into the submersed pump

Could you let me know what agitator i can buy on RS to do such thing?

thanks

martin