In membrane separation systems, it is probably shear which is the most significant parameter for driving the membrane process. Pressure is obviously important for forcing the water through the membrane but shear is arguably the property of the system which largely determines the rate of membrane fouling and so, ultimately, the flux.
In 2012, the Arla milk powder factory in Sweden planned to expand operations. The increased production process generated larger wastewater volumes which the receiving municipal treatment plant was unable to process. Therefore, the dairy decided to build their own treatment plant on site, which needed to be installed within a short period of time and meet strict discharge requirements.
In autumn 2015, after two years of research and development, Pentair brought to market its new ‘Helix’ product. An enhancement to X-Flow tubular membrane technology, Helix features a helically-winding ridge on the inside of the membrane which is designed to tackle cake build-up and enhance flux. The technology has so far been tested on both industrial effluents and municipal wastewater.
Foaming of conventional activated sludge (CAS) is very common. It may happen during start-up due to the presence of surfactants, with insufficient biomass to degrade them during the early stages. However, this is normally a short-term issue. These foams (from surfactant foaming) are mostly white and can be countered with anti-foamants until there are sufficient biomass developed to degrade them.
Key facets to take into account when selecting a screen for your MBR design include the screenings capture ratio, screen apertures, screening flow velocity, ancillary processes and coarse suspended solids, and screen maintenance. The screenings capture ratio (SCR) represents the amount of solids removed by the screen as a proportion of the total coarse solids load, and as such is analogous to membrane rejection.
The importance of screening upstream of a membrane bioreactor remains a key concern for MBR practitioners. Screening protects the membrane from mechanical damage from sharp or abrasive particles and from clogging from hair and matted cotton fibre. While any screen is better than no screen at all, it is critically important to have a properly designed and sized screening system.