New Standard Revision: AWWA B130-2018: Membrane Bioreactor Systems
Water treatment encapsulates a network of ostensibly unnatural processes to fulfill an auspiciously natural need: assuring public health with access to clean, safe water and responsibly managed wastewater. Water treatment features the chemical or physical removal of particulate matter by coagulation, flocculation, sedimentation, and filtration, along with disinfection to inactivate any residual pathogenic microorganisms.
Among the series of processes for treating potable water, filtration retains a place of exalted importance. This process actively helped purify water for some time, but things like granular media filters can cause some problems, as pathogens can still pass through the filters. To limit the hazards that these microorganisms can present to public health, there are common disinfection practices. However, some microbes, like Cryptosporidium, are resistant to these disinfection practices.
An alternative technology known to avoid this string of issues is membrane filtration. This in itself comes in several forms, with reverse osmosis (RO) being used since the ‘60s for desalination—RO is simply the reverse of the natural osmosis process of cells—and nanofiltration, which applies the principles of reverse osmosis to remove dissolved contaminants from water, dates back to the ‘80s for softening.
According to the EPA’s Membrane Filtration Guidance Manual, however, the most profound impact on the use, acceptance, and regulation of membrane processes was felt in the early ‘90s, following the commercialization of backwashable hollow-fiber microfiltration (MF) and ultrafiltration (UF) membrane processes for removing particulate matter like turbidity and microorganisms.
A noteworthy accomplishment resulting from the widespread acceptance of membrane filtration can only be understood while exploring an alternative water treatment narrative that dates back long before the advent of MF and UF. In 1913, the process known as activated sludge (AS) was discovered in the UK. Activated sludge deals with the treatment of sewage and wastewaters, and all AS consist of three primary components.
This includes an aeration tank, acting as a bioreactor, a settling tank, to separate AS solids and treated waste water, and return activated sludge (RAS) equipment to transfer settled AS from the clarifier to the influent of the aeration tank. Ultimately, aerobic microorganisms break down aerated sewage during the activated sludge process.
With MF and UF membranes initially available in the ‘60s, the process of membrane bioreactor (MBR) treatment was first introduced. MBR treatment systems were designed as adaptations of activated sludge treatment systems by replacing the settling tank of the process with a filtration membrane. However, even though this concept was attractive, it was a challenge to justify the then-high costs of UF and MF membranes.
A major breakthrough for MBR treatment came in 1989 with the innovation of submerging membranes in the bioreactor. This updated the design of MBRs, which generally had the separation device external to the reactor. This development, paired with the widespread commercialization of MF an UF membranes just a couple of years later, made MBRs into practical means of water treatment.
This is what AWWA B130-2018 covers—membrane bioreactor systems. The standard provides purchasers with guidance for the purchase and installation of MBR treatment systems. Specifically, it addresses background information, materials, system guidance, data to be provided by the supplier, water flow guidelines, performance criteria, and verification.
AWWA B130-2018 is the second edition of the American National Standard for membrane bioreactor systems, which was published in 2013 to offer guidance for the flourishing technology. Revisions to the second, 2018 edition included changes to the scope and to feedwater quality characterisitics.
AWWA B130-2018: Membrane Bioreactor Systems is available on the ANSI Webstore.