Effect of temperature on submerged membrane activated sludge reactor

Abstract

This study investigates the performance of Submerged Membrane Activated Sludge Reactor on treating synthetic wastewater and also the effects of varying temperature of a laboratory scale Submerged Membrane Activated Sludge reactor. Laboratory bench-scale continuous reactors, fed with synthetic wastewater were used. The operational volume of the reactor was 20 litres and included a membrane. The membrane was made from a polymer material (HDPE) with a thickness of 3.5 mm. The membrane, whose pore size ranged between 0.1 – 1mm, played the role of a secondary clarifier. Effects of temperatures of 27, 32, 37, 42, and 47°C were studied. Studies on the effects of temperatures were carried out as the pH was maintained in the range of 6.5 to 8.00 by adjustment of the feed pH with NaOH. Nutrients levels were maintained in the ratio of COD: N: P at 100:5:1. The biomass was considered to be acclimatized when MLSS concentration maintained constant levels (3000 ± 2000 mg/L). The reactor was aerated continuously with an aquarium air stone with compressed air supplied at approximately 3 L/min to maintain dissolved oxygen (DO) concentration of 1.5 to 3.0 mg/L. Results indicated that as the operating temperatures of the reactors were increased, the percent removal of the soluble chemical oxygen demand (COD) also increased. The highest percent removal of soluble COD was obtained at 47 ºC (90.45%) while the lowest percent removal of soluble COD was obtained at 32 ºC (24.27%). The higher concentration of MLSS was obtained at 42 ºC (80 mg/L) while the lowest concentration was obtained at 10 mg/L at the same temperature (42 ºC). The patterns of the MLSS concentration for the temperature of 27 ºC, 32 ºC, 37 ºC, 42 ºC, and 47 ºC was increased and decreased gradually. The greatest concentration of MLVSS was achieved at 47 ºC and 32 ºC (80 mg/L) while the lowest was attain at 42 ºC which is 10 mg/L. On the other hand, increases the temperature affected the DO concentrations. The highest and lowest DO concentration was obtained at 27 ºC which is 5.1 mg/L and 1.7 mg/L.