The influence of heavy metals on activated sludge processes: performance, microbial dynamics, and recovery strategies

Abstract

Environmental pollution, primarily water and soil due to heavy metals is extensive and alarming concern due to numerous industrial sources. Heavy metals considerably alter the microbial dynamics and reduce the efficiency of activated sludge process in the wastewater treatment systems. Despite considerable progress in wastewater treatment research, a thorough knowledge of the mechanisms governing microbial interactions, recovery methods, and activated sludge efficiency continues to be insufficient. The present review critically evaluates the current understanding on heavy metal effects on activated sludge processes with an emphasis on process performance, microbial community interactions, and resource recovery from wastewater treatment plants. The effects of metal toxicity and their influence on chemical oxygen demand, nitrification, denitrification, extracellular polymeric substances and effect on microbial diversity and community composition of activated sludge are comprehensively discussed. Furthermore, the review summarizes various recovery and mitigation strategies for heavy metal-stressed activated sludge systems. Developing solid and sustainable wastewater treatment systems that can function under heavy metal stress requires a thorough understanding of these interactions.