Wastewater / effluent
Wehrle was contacted in 2005 to make improvements to an existing wastewater treatment plant at Bertschi’s road tanker washing facility at Birrfelden in Switzerland.
The facilities typically generate 30–100m3 wastewater from rinsing over 50 tankers daily. The tankers are used to transport over 6000 types of resins, polymers and other chemicals, resulting in wastewater that is both high in COD and variable (20,000–50,000mg/l).
Treated wastewater is discharged to sewer under typical license conditions that include effluent volume and final quality charging conditions.
The existing treatment technology at the site consisted of flocculation/precipitation with conventional activated sludge (CAS), which was not capable of reliably treating the wastewater. Biomass was periodically carried through with the final effluent under high-load conditions preventing release of treated effluent to sewer, and incurring additional effluent storage and disposal costs.
Upgrading of the wastewater treatment system was achieved utilising Wehrle’s extensive experience. The key treatment requirements were to consistently produce up to 100m3 final effluent with COD<1000mg/l.
This was to be achieved whilst meeting a lower specific energy consumption at a specific sludge production of 0.12kg activated sludge per kg COD.
Wehrle’s design solution incorporated an MBR to replace the existing CAS system using tubular cross-flow UF membranes. Extensive on-site testing was conducted prior to the design of the full scale system using a fully automated pilot scale Wehrle MBR system.
The MBR system has proved to be effective at consistently reducing solids and COD to the required levels. Life-time cost estimates have also proved to be favourable when compared to the alternatives, and specific energy consumption objectives were also readily met.
Bertschi contracted Wehrle to install the full-scale MBR technology in December 2005 and the re-designed, upgraded plant was commissioned in September 2006 by Wehrle engineers who optimised the new system and attained client acceptance by February 2007.