Anaerobic membrane bioreactor cleans effluent

By Ryan C. Christiansen
Web exclusive posted Feb. 17, 2009, at 1:32 p.m. CST

ADI Systems Inc., a Fredericton, New Brunswick-based biological treatment technology provider for industrial wastewater management and renewable energy generation, has announced the successful installation of an anaerobic membrane bioreactor that effectively reduces the biochemical oxygen demand (BOD) for wastewater effluent from an anaerobic digester to nearly zero.

The anaerobic membrane bioreactor has been installed at a plant in Marlborough, Mass., operated by salad dressing and barbecue sauce manufacturer Ken's Foods Inc. The anaerobic digester, coupled with the anaerobic membrane bioreactor, treats wastewater that's high in organic compounds, degradable solids, fat, oil, and grease. ADI Systems said the bioreactor has effectively increased the capacity of the facility's existing anaerobic digester by 60 percent while improving the quality of the effluent produced by the digester so that it can be discharged into the municipal sewer system.

"The BOD going in is about 21,000 milligrams per liter and the BOD leaving the digester is about 15 milligrams per liter. That's pretty incredible for an anaerobic digester," said Graham Brown, president of ADI Systems. He said the anaerobic membrane bioreactor, believed to be the first of its kind in North America, not only improves the cleanliness of the effluent produced by the anaerobic digester, but also increases the efficiency of the digester. Traditionally, anaerobic digesters rely on gravity separation to clean the effluent produced by the digester, but using a membrane means "you've got a very reliable way of keeping the solids in the digester," he said, "because you're not relying on gravity to separate these solids that weigh only just slightly more than water, anyway."

"When digesters have gone bad from time to time in installations, it's often because the solids are not separating properly, and so you're starting to lose your bacterial population," Brown said. "And when you begin to lose your bacterial population, your digester capacity drops and drops and drops because you don't have enough bugs there, basically, to do the job."

According to ADI Systems, it has installed nearly 200 anaerobic and aerobic wastewater treatment systems in 30 countries.