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.
Features - Pre-treatment and post-treatment
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.
Municipal wastewater usually contains between 4 and 12 mg/L total phosphorus (TP) concentrations in the range 4−12 mg/L. A conventional activated sludge process (CAS) can take this down to 2−4 mg/L, or 0.5−1 mg/L if an enhanced biological phosphorus removal (BPR) process is used. To achieve the levels required to suppress eutrophication, however, demands P levels of 0.01−0.3 mg/L
In Japan, there are over 3,000 MBRs which have been in operation since the 1980s for small-scale on-site industrial/household wastewater treatment. However, municipal wastewater applications began only in the mid 00’s, leading to 19 operational full-scale plants by April 2013.
Aquaculture is the fastest growing agriculture worldwide, supplying a substantial amount of seafood consumed today. The ‘recirculating aquaculture system’ (RAS) is an upcoming production system in intensive fish production, where over 90% of the water is recycled for production of live feed, larvae and fry and on-growing fish.
The Arenales del Sol WWTP in Spain combines biological treatment with nutrient removal with a submerged MBR system fitted with flat sheet (FS) ultrafiltration membranes, with an average treatment capacity of 10,000 m3/d (10 MLD). The plant provides high quality treatment to highly variable seasonal sewage inflow due to the nature of this popular coastal region.