Novel Biofilm-MBR Concept with Zero Energy Consumption for Air Scouring and Permeate Production

Novel biofilm-MBR concept with zero energy consumption for air scouring and permeate production

Igor Ivanovic^a and TorOve Leiknes^a

^a NTNU - Norwegian University of Science and Technology, Trondheim, Norway

igor.ivanovic@ntnu.no and torove.leiknes@ntnu.no

A novel biofilm MBR (BF-MBR) concept coupling a moving media biofilm reactor with a membrane filtration unit in a vertical arrangement is being investigated (Figure 1). The membrane filtration unit consists of polymeric flat sheet membranes positioned above the biofilm reactor. The design enables exhaust air from the aerobic biological treatment in the biofilm reactor to be used for air scouring of the membranes, thereby reducing energy required for air scouring to zero. The reactor design further enables increasing the water level sufficiently above the membrane to enable operation by gravity, eliminating energy required for permeate extraction by suction pumps. A cyclic mode of operation of the membrane filtration unit is applied; however, the influent wastewater is treated in a continuous mode.

Figure 1. Illustration of novel biofilm MBR concept and pilot plant investigated in this study

Figure 2 illustrates two operational cycles. The water level in the reactor is increased until a hydrostatic pressure of 4500 Pa (measured from the bottom of the membrane module). At this point (A in Figure 2), the permeate valve is opened and a volume of permeate is extracted (red line, B in Figure 2). Consequently the water level in the reactor drops, reducing the hydrostatic pressure to the level of 3500 Pa (B in Figure 2). Permeate level (red line) rise until amount of 7000 mL (point B) and after that the permeate valve is closed resulting in relaxation of the membranes. The water level again increasing until a hydrostatic pressure of 4500 Pa (C in Figure 2). In parallel, during this sequence (B-C), a purge valve connected to the permeate tank is opened to drain the permeate tank. A new cycle is then started as illustrated by points C-D-E in Figure 2.

The operating mode described above enables the membrane to be operated without a suction pump and in a filtration - relaxation cycle while continuously being exposed to air scouring with exhaust air from the bioreactor below membrane arrangement.

The paper will present results from long term operation and overall system performance of the proposed novel BF-MBR concept with zero energy consumption for operation the membrane component applied for treatment of municipal wastewater.

Figure 2. Operational cycles of novel BF-MBR