Effects of sludge particles on performance of enhanced backwash for fouling reduction in anaerobic membrane bioreactors

Abstract

The objectives of this research are to investigate effects of sludge properties in terms of particle size composition on performance of physical and chemical cleaning and to understand fouling mechanisms of the specific feed solutions. The sludge was centrifuged at three rotational speeds to differentiate particle size distributions, and the supernatant and residual flocs were used for microfiltration and cleaning processes. The filtration flux with the flocs was greater than those of the three supernatants, which indicates that fouling was greater with supernatants. Taking into account that the solid concentrations of the raw sludge and the residual flocs were 10 times greater than those of the supernatants, the reduction in flux for the supernatants is significant. The flux was recovered to 64% of the clean water flux at the maximum efficiency by two cleaning of membrane fouled with supernatant treated at 1,000 rpm. In addition, increasing removal of coarse particles by applying higher centrifugal speed (i.e. 1,000 and 1,500 rpm) yielded greater recovery performance by chemical cleaning. Particle composition such as the fine particle concentration played a significant role in fouling and the enhanced backwash cleaning efficiency.

Keywords:

• Anaerobic MBR
• Membrane fouling
• Sludge particles
• Chemical cleaning
• Physical cleaning
• NaOCl

Acknowledgment

This work is financially supported by Korea Ministry of Environment (MOE) as “Waste-to-energy recycling human resource development Project (YL-WE-12-001)”.

Notes

Presented at the 13th International Conference on Environmental Science and Technology (CEST 2013), 5–7 September 2013, Athens, Greece