Reconsideration of anaerobic fermentation from excess sludge at pH 10.0 as an eco-friendly process

Volatile fatty acids' (VFA) production from excess sludges during the initial stage (133 h) in the fermentation processes and the disposal risk of sludge were investigated under the real time controlled condition of pH at 5.5 and 10.0. The results showed that the total VFA production at pH 10.0 was markedly higher than that at pH 5.5. Anaerobic fermentation at pH 10.0 was the first be shown having marked reduction effect on total bromate in excess sludge when compared with pH 5.5. Meanwhile, at pH 5.5, sludge dewaterability deteriorated slightly with the fermentation time, whereas at pH 10.0 it deteriorated greatly with the fermentation time. Moreover, the mechanism of VFA improvement was also explored. It was suggested that anaerobic fermentation process at pH 10.0 should be reconsidered to be applied as an eco-friendly material recycling process, based on its sludge dewaterability and total bromate.