OPERATION

Operator skills.

The EPA Membrane Filtration Guidance Manual (2005) estimates that 24-86 hours of operator training is required to learn the following aspects of membrane system operation:

• Computer Skills

• System overview

• Principles of membrane operation

• Control systems including SCADASCADA:
SCADA is an acronym of Supervisory Control and Data Acquistion. The term refers to computer systems including programmable logic controllers (PLCs) used to monitor and control water treatment processes and distribution systems including storing data and displaying the status of systems and historical trends. systems

• PretreatmentPretreatment: 
In membrane treatment systems, pretreatment encompasses all treatment processes prior to the membrane, e.g., strainers, flocculation, and sedimentation. unit operations

• Operation/pumps/instrumentation

• Post-treatmentPost-treatment:
  Post treatment for microfiltration and ultrafiltration water treatment systems is essentially the same as for conventional treatment and typically consists of disinfection, fluoridation, and corrosion control.

• Chemical cleaningClean-in-place (CIP) or in-situ chemical cleaning:
 Clean-in-place is a procedure performed periodically to clean a membrane more thoroughly than backwashing can achieve in order to restore the permeability of the membrane towards baseline levels. The process uses chemicals such as citric acid and chlorine or others to remove accumulated foulants on the membrane.

• Integrity testing/Module isolation and repair

• Monitoring/troubleshooting/data normalization

• Details of control system/remote monitoring

The 2008 report from by the AWWA Subcommittee on Periodical Publications of the Membrane Process (2008) states that an important function of the operator is to track the effectiveness of chemical cleaning, i.e., whether the membrane filters recovered to normal temperature adjusted conditions of initial headloss and rate of headloss increase. The operator must also monitor production efficiency by monitoring filtrateFiltrate:
  Filtrate is the water that has passed through the membrane. production and backwashBackpulse or backwash:
 1) Backwash is a procedure in which periodically the flow direction is reversed through the membrane for a short period of time in order to remove particulates accumulated at the membrane surface. 
2) Backwash also refers to the waste water produced as a result of the backwash procedure. water use plus downtime for other operations such as chemical cleaning and integrity testing. The importance of SCADA systems must be emphasized for monitoring the degradation and the post backwash/cleaning recovery of filter membrane permeability as well as for monitoring overall performance. Considerable record keeping is required such as records of sensor calibrations, membrane and fiber repair, integrity testing, module replacements as well as feed and filtrate pressures, flow rates, turbidityTurbidity:
  Turbidity is a measure of  the cloudiness of a water as well as a gross measure of the amount of suspended solids in a water., temperature, and calculated transmembrane pressure drop and fluxFlux:
  Flux is the flow rate of water applied per unit area of the membrane and has units of volume/unit area/time..