004 - Centrate tank mixing and pumping modifications

SCOPE of WORK: We currently do not have any mixing capabilties in our centrate tanks.  These tanks are a retro fit from their original design.  We have the capability of using 1-3 tanks that feed into a pumping channel.  We are looking for adequate mixing that will keep solids in suspension as the tanks fill up and pump down.  We will consider different options, do not want vertical shaft mixers that would require building a bridge over the tanks or floating mixers.  Liquid level in the tanks vary from 11 ft to 2 ft., rising and falling as we run centrifuges.
We also want to imporve our centrate pumping and control capabilities.  We currently pump with 2 submersible sump pumps feeding into an 8 inch line with no flow meter and no VFD's.  We would like to have pumps with variable flow rates and a flow meter installed.  Flow rate capability should be 20-80 gallons per minute.  Typical pH range in this tank is 2-4 and aluminum sulfate is added to the tank.  Equipment should be able to withstand these conditions.