Membrane bioreactor technology

Improves treatment of high-organic-content water

A next-generation, carbon-enhanced membrane-bioreactor (MBR) system improves treatment of industrial wastewater with high organic content and containing compounds that resist microbial breakdown. The system allows economic reuse of wastewater or discharge to meet stringent environmental standards. The new MBR, dubbed EcoRight, will be commercially available in early 2011. First envisioned by Saudi Aramco (Dhahran, Saudi Arabia; www.saudiaramco.com), the technology was developed jointly with Siemens Water Technologies Corp. (Warrendale, Pa.; www.siemens.com/water).

EcoRight’s key technological innovation involves the use of granular activated carbon (GAC), rather than powdered activated carbon (PAC), to adsorb organic contaminants in the wastewater. In PAC-containing MBR systems, PAC can cause varying degrees of abrasion on microfiltration membranes, explains Siemens sales and marketing director Tom Schultz. “That can result in higher operating costs due to shorter membrane life.” EcoRight technology isolates the GAC from the membranes, almost entirely eliminating abrasion associated with using PAC. EcoRight developers have invented a proprietary technique for keeping the GAC in suspension inside the MBR without using energy beyond that required for conventional aeration, Schultz says, which had been a major technological barrier to using GAC in the past.

An additional advantage of the technology is its considerably reduced carbon consumption compared to other PAC-based MBR systems or those using GAC polishing columns, because the granules are retained in the system longer. Longer retention allows a higher degree of biological regeneration of the GAC to occur, as microbes break down organics adsorbed inside the GAC pore structure. EcoRight allows effluent to be fed directly into reverse osmosis equipment for reuse as boiler feed, irrigation, utility or cooling water, the companies say.

Laboratory work on the technology has been completed, and testing has begun on a recently assembled, field demonstration unit built in Saudi Arabia by Saudi Aramco and Siemens.