Sequencing batch reactor biofilm system for treatment of milk industry wastewater

A sequencing batch reactor biofilm (MSBR) system was modified from the conventional sequencing batch reactor (SBR) system by installing 2.7 m2 surface area of plastic media on the bottom of the reactor to increase the system efficiency and bio-sludge quality by increasing the bio-sludge in the system. The COD, BOD5, total kjeldahl nitrogen (TKN) and oil & grease removal efficiencies of the MSBR system, under a high organic loading of 1340 g BOD5/m3 d, were 89.3±0.1, 83.0±0.2, 59.4±0.8, and 82.4±0.4%, respectively, while they were only 87.0±0.2, 79.9±0.3, 48.7±1.7 and 79.3±10%, respectively, in the conventional SBR system. The amount of excess bio-sludge in the MSBR system was about 3 times lower than that in the conventional SBR system. The sludge volume index (SVI) of the MSBR system was lower than 100 ml/g under an organic loading of up to 1340 g BOD5/m3 d. However, the MSBR under an organic loading of 680 g BOD5/m3 d gave the highest COD, BOD5, TKN and oil & grease removal efficiencies of 97.9±0.0, 97.9±0.1, 79.3±1.0 and 94.8±0.5%, respectively, without any excess bio-sludge waste. The SVI of suspended bio-sludge in the MSBR system was only 44±3.4 ml/g under an organic loading of 680 g BOD5/m3 d.