Preliminary Study of Hospital Wastewater Treatment with a Submerged Membrane Bioreactor (SMBR): Case Study of Songklanagarind Hospital – Thailand

Abstract

The objective of this research was to study hospital wastewater treatment using a submerged membrane bioreactor (SMBR). The lab scale unit of SMBR with a working volume of 20 liters was operated at a hydraulic retention time of 0.416 day and 0.208 day at F/M ratio of 0.18 day^–1 and 0.29 day^–1. The operating conditions were set up to provide good biological treatment without sludge extraction, and two different permeate flux values were studied. The performance of membrane was studied by monitoring the variation of transmenbrane pressure (TMP) during filtration runs. The efficiency of MBR was investigated according to the daily measurements of pH, dissolved oxygen and temperature. The COD, BOD₅, NH₄⁺–N, TKN, color, turbidity, SS and Escherichia coli (E.coli) in influent and effluent were analyzed. Membrane fouling intensity occurred slowly when the system operated with flux at 10 L/h/m²Â and 20 L/h/m², which induced high TMP at the initial period of filtration. The fouling rate was at about 0.3022 mbar/day for the permeation of flux at 10 L /h/m². The fouling rate still remained at 0.2774 mbar/day for 20 L/h/m². The results showed the great effect of membrane use for total biomass retention and the removal rate of COD, BOD₅ and E.coli were over 90%. The characteristics of sludge in SMBR showed healthy floc formations with good settling. Although the ratio of MLVSS/MLSS was lower than the normal range (about 0.2), it was found that the average values of COD and NH₄⁺–N in permeate were lower than 2–80 mg/L and 0.05–6.755 mg/L while the value of turbidity was also less than 3 NTU.