Implementing hybrid growth processes in membrane bioreactors (MBR) for treatment of chicken manure wastewater

Membrane Bioreactors (MBRs) have been used for the treatment of various wastewaters. In MBR applications fouling phenomena is an inevitable consequence of membrane filtration related to physical, chemical and biological mechanisms. Mixed Liquor Suspended Solids (MLSS) concentration, particle size distribution and Extracellular Polymeric Substances (EPS) are considered significant parameters that directly affect fouling rates. Improving biomass properties is a practical alternative method to minimize membrane fouling and improve process efficiency under different operating conditions. A possible and promising approach to minimize membrane fouling and increase treatment efficiency is the use of Biofilm Membrane BioReactor (BMBR) as an advanced approach. The research work present different designs of MBRs’, airlift MBR and moving-bed BMBR, towards fouling minimization. In this work, airlift MBR and moving-bed BMBR were operated with artificial wastewater made from domestic wastewater and chicken manure using a hollow fiber membrane module of ZW-10 (Zenon Inc, Canada) under ambient arid conditions (Kiryat Sde Boker, Israel). The bioreactors were equipped with a draft tube (diameter of 295 mm) and the moving-bed BMBR was equipped with suspended carriers (AqWise Inc.) occupying around 20% of the reactor volume, serving as the biofilm support. The carriers are made from high-density polyethylene with a specific surface area of 600 m2/m3 and the driving force generated by the airlift enhanced the carriers’ circulation. The systems were operated under a mode of 5 minutes filtration, 15second backwash, 30 days of Sludge Retention Time (SRT), and 3.4 m3/hr of aeration rate. The results showed that the mean removal efficiencies for the main quality parameters in the airlift MBR and moving-bed BMBR were, respectively, 81.3% (from 570 mg/L to 106 mg/L) and 89.1% (from 579 mg/L to 63.3 mg/L) for COD, 96.9% (from 207 mg/L to 6.4mg/L) and 98.6% (from 225 mg/L to 3.1 mg/L) for BOD5, 46.7% (43.1 mg/L to 23 mg/L) and 39.5% (from 28.5 mg/L to 17.2 mg/L) for NH4-N, and 24.6% (12.1 mg/L to 9.1 mg/L) and 14.2% (from 11.8 mg/L to 9.3 mg/L) for PO4-P. The results were obtained for 17 operating days for the airlift MBR and 25 operating days for the moving-bed BMBR. Poor nitrification activity was observed, probably due to inhibition/toxicity induced in the chicken manure or chicken food, or due to high MLSS concentration (from 5,660 up to 10,730 mg/L in the moving-bed BMBR and from 2,700 up to 7,000 mg/L in the airlift MBR) resulting in insufficient dissolved oxygen concentrations (average value of 0.5 mg O2/L in the moving-bed BMBR and 1.32 mg O2/L in the airlift MBR). To check the colloidal characteristics of the mixed liquor, Zeta potential and particle size distribution measurements were conducted. The results from Zeta potential (-20.43 mV) and particle size distribution measurements of the mixed liquor indicate a colloidal system of the mixed liquor with an incipient instability behavior, which has proved highly fouling in MBR systems.