MBR membrane costs drop while other costs rise

Costs associated with the membrane system component of membrane bioreactor (MBR) wastewater treatment and reuse systems decreased between 2000 and 2006 by approximately 33%, according to a report published by the US Bureau of Reclamation in February 2009.

Report 147 Evaluation of newly developed membrane bioreactor systems for water reclamation says that non-membrane MBR process component costs (headworks, process basins, blower/pump building, chlorine dosing system and effluent storage) increased by approximately 24% over the same time period.

The study behind the report looked at four systems that were, in 2005, newly developed. The specific systems tested and participating MBR suppliers included Puron™ MBR from Koch Membrane Systems (KMS), Huber® MBR from Huber Technology, Kruger Neosep™ MBR from I Kruger Inc and DynaLift™ MBR from Parkson Corporation.

The evaluation, carried out by consultant MWH, looked at four MBR pilot systems operated for a target period of about 3,500 hours on raw wastewater from Point Loma wastewater treatment plant in San Diego, California. In addition, a reverse osmosis desalination membrane provided by KMS was also evaluated while operating on MBR effluent.

A significant difference was observed in the operating flux of the submerged MBR systems and external MBR system. The median net flux for submerged MBR systems was measured between 13-16 gallons per square foot per day (gfd) whereas that for an external MBR system was measured at 27 gfd. The high-flux operation of the external MBR system may be attributed to better turbulence available within the external membrane module, says the report, due to a relatively higher recirculation flow requirement compared with submerged MBR systems.

Another finding was that the Kruger Neosep system required fewest maintenance cleans during the same operational period, while both the Puron and DynaLift systems had the lowest scouring air requirement at 0.019 scfm/ft².

The full report can be downloaded from the Reclamation website.