Wastewater

Engineering

Sewage treatment

Biofilm

Ecology

Bacteria

Biology

Halotolerance

Denitrification

Activated sludge

Salinity

Nitrogen

Food science

Nitrification

Genetics

Environmental engineering

Organic chemistry

Extracellular polymeric substance

Environmental chemistry

Environmental science

Nitrite

Denitrifying bacteria

Chemistry

Pulp and paper industry

Aerobic denitrification

Nitrate

Bioresource Technology

Saline wastewater poses a threat to biological nitrogen removal. This study investigated whether and how static magnetic field (SMF) can improve the salt-tolerance of aerobic granular sludge (AGS) in two simultaneous partial nitrification and denitrification (SPND) reactors. Results confirmed that the SMF improved the mean size and settleability of granules, stimulated secretion of extracellular polymeric substances with high protein content, in turn enhancing the aerobic granulation. Although high salt stress inhibited functional microorganisms, the SMF maintained better SPND performance with average COD removal, TN removal and nitrite accumulation ratio finally recovering to 100%, 72.9% and 91.1% respectively. High throughput sequencing revealed that functional bacteria evolved from Paracoccus to halotolerant genera Xanthomarina, Thauera, Pseudofulvimonas and Azoarcus with stepwise increasing salinity. The enhanced salt-tolerance may be because the SMF promoted the activity of these halotolerant bacteria. Therefore, this study proposes an economic, effective and environmental biotechnology for saline wastewater treatment.

Enhanced aerobic granular sludge by static magnetic field to treat saline wastewater via simultaneous partial nitrification and denitrification (SPND) process