Evaluating the Effects of Aged Fe-Enhanced Primary Sedimentation Sludge on Methane Production from Aluminum-Waste Activated Sludge during Anaerobic Digestion

The iron-containing chemically enhanced primary sedimentation (Fe-CEPS) sludge, as an alternative low-cost iron source, can be used to promote methane production of aluminum-waste activated sludge (AI-WAS) during anaerobic digestion ( AD). Generally, the aging time would induce changes in iron species and compounds in the Fe-CEPS sludge and subsequently affect the methane production process. Here, the effects of Fe-CEPS sludge aging on methane production of Al-WAS were investigated. After a 10-day aging treatment, the iron compounds showed a high crystallinity, and the structure of the CEPS sludge became compacted. The aging treatments always increased the methane yield, with the maximum value (143.3 mL/g VS) occurring after 3 days of aging. Following an addition of short-term (0-3 days) aged Fe-CEPS sludge, the physical structure of AI-WAS obviously collapsed during AD. Meanwhile, the surface of the digested sludge became hydrophobic, which benefited the contact between enzymes and sludge flocs, thereby enhancing the biodegradability of the sludge. The results suggest that the addition of short-term aged Fe-CEPS sludge is an effective approach for Al-WAS digestion, which reflects a treat the wastes with wastes concept.

Automated summary

This study found that the addition of chemically enhanced primary sedimentation (Fe-CEPS) sludge as a low-cost iron source could promote methane production from aluminum-waste activated sludge (AI-WAS). The addition of short-term aged Fe-CEPS sludge increased methane yield and improved the biodegradability of the sludge.