The following types of membrane filtration are distinguished based on the membrane pore size:
Membranes can be used for a wide range of applications. Thus, different structural configuration can be found in industrial and municipal applications. The following are the main types of membrane configurations available:
Ultrafiltration, commonly used in MBR systems, effectively removes total suspended solids (TSS) and bacteria. Thus, in many cases the effluent from MBR treatment does not require disinfection. Similarly, secondary clarification or sand filtration is not needed in MBR systems to meet regulatory requirements.
The Packaged MBR system is a combination of biological wastewater treatment and high-efficient solids/liquid separation. Mechanically pre-screened wastewater is treated biologically and separated from the activated sludge by ultrafiltration membranes, which act as a physical barrier to suspended solids and bacteria, producing high quality effluent. MBR technology restores wastewater to a hygienic condition fit for use as reuse water, for example, watering the garden or flushing toilets. The advantages of MBR systems are summarized below:
When used an extension of the conventional activated sludge (CAS) process, MBR provides an opportunity to either significantly reduce the overall process footprint or increase the capacity of an existing conventional process plant.
Raw sewage from the equalization tank passes through a safety screen (0.5 – 1.0 mm) before being pumped to the biological treatment unit. The biological treatment unit comprises of anaerobic and aerobic bioreactors. The mixed liquor is pumped then to the phase separation stage done on ultrafiltration membranes. The ultrafiltration membranes are installed in two parallel trains. The liquid not filtered through the membranes overflows the tanks and returns to the beginning of the process in an open channel as recirculation sludge. The process pumps draw the treated water through the membranes and forward it to the discharge point, or for reuse. The membranes are constantly scoured with air that is provided by air scour blowers. Excess sludge is forwarded to a sludge dewatering unit. The membranes are cleaned automatically on a regular basis by specific membrane cleaning chemicals.