Witton ETP

The contract for the fast-track turnkey, design, supply and construction of an industrial effluent treatment plant (ETP) with a value of ?1.5million, was awarded to Naston as Principal Contractor by Titanium manufacturer Timet UK Limited of Birmingham in August 1997.

An existing ETP, treating effluent from the Timet site at Witton, was scheduled for closure at the end of 1997 and it was vital that the new plant was ready to receive effluent by this time. The target date was achieved with no loss of production, even with an increase in manufacturing output from the plant of over 35%.

The new ETP was designed with a minimum footprint, has a capacity to treat up to 100 m?/h of process effluent and provides a final effluent that meets stringent consent limits. The plant has semi-automatic operation with telemetry, off-site monitoring and repeat alarms.

Effluent Treatment Process
Effluent from the manufacture of Titanium is produced in four separate areas and contains a variety of acids, oils and sediments. The treatment process involves the following stages.

- Two pump stations with pipelines.
- Balancing of separate inputs and flow peaks in a concrete balancing tank.
- Coarse pH control of main acidic effluents with interception tank for bulk acid discharges.
- Steady flow input from progressive cavity pumps.
- Lime, Ferric Sulphate and Polyelectrolyte addition for pH control, flocculation and coagulation.
- Continuous separation of flocculants and filtration of effluent.
- Sludge consolidation, pressing and dewatering.
- Final effluent control and monitoring.

Mixing, Flocculation and Filtration
Hydrated lime slurry for pH control, Ferric Sulphate for flocculation and Polyelectrolyte for coagulation are injected and mixed at high and low speeds in respective tanks. The resulting floc is separated in the twin lamella separators and the effluent is filtered through twin automatic sand filters arranged for continuous washing.

Sludge Press and Lime Dosing Plant
Concentrated sludge is pumped by air driven diaphragm pumps into a hydraulically operated recessed plate filter press where it is filtered and dewatered to produce a 30% cake, discharging into a skip. From a 30 Tonne hydrated lime silo, twin screw conveyors feed automatic duty/duty slurry mixing tanks. The fine and coarse dosing system uses diaphragm pumps to provide fully automatic pH control.

Final Effluent Discharge and Storage
Final effluent which meets all consent levels is discharged to the public sewer via an ultrasonic flow measurement chamber with automatic pH measurement and control of divert valve. Any "out of limits" effluent is automatically diverted to an 850 cubic metre concrete holding tank before recycling for re-treatment.

Oil Emulsion Treatment Plant
30 m?/day of 2000 ppm oil emulsion passes into the buffer storage tank. Free oil is removed in a Coalescer and an Ultra Filtration Unit removes the remaining emulsified oil, allowing discharge of effluent direct to the public sewer.