A review of physical relationships between form and function in wastewater biotreatment and a new theory relating activated sludge and biofilm systems behaviour

Abstract

In this review paper, a physical systems analysis based on thermodynamics has been applied to the observed behaviour of activated sludge as a physical system. The origin of the microecology of activated sludge and its relationship to biofilms and the metabolic consequences of the extracellular polysaccharide (EPS) formation are explained for the first time. Feast‐famine conditions are shown to be the leading candidate for the evolution of the ability of biofilm forming bacteria and activated sludge ‘floc‐formers’ to form EPS. The basis for competition for RBCOD between low F:M filamentous heterotrophic bacteria and ‘floc‐forming’ heterotrophic is presented and its relationship to activated sludge bulking described.

The evolution of alkaliphilic biofilm communities in response to extreme alkaline pH values

“…From a wastewater treatment perspective, the switch between a floc and biofilm‐based existence is often associated with external stressors where EPS production plays a key role in this survival (Palmer et al, 2021). The biofilms generated within this study were resilient to their harsh exterior environment due to internal pH modulation linked to EPS production.…”

Toxic Effect of Ammonium Nitrogen on the Nitrification Process and Acclimatisation of Nitrifying Bacteria to High Concentrations of NH4-N in Wastewater

“…Proper operation of mechanical and biological wastewater treatment plants from the chemical industry is a difficult matter, especially in the case of plants that receive different wastewater. In such plants, the amount and composition of wastewater and the concentration of the organic pollutant are constantly fluctuating [51,52]. Meanwhile, the biocenosis of activated sludge is reluctant to acclimate to specific industrial substances [53].…”

Sensitive detection of quorum signaling molecules (N-acyl homoserine lactones) in activated sludge based on surface molecularly imprinted polymers on CQDs@MIL-101

“…The activated sludge process is an aerobic biological treatment method that utilizes suspended microbial flocs to treat organic wastewater, which is one of the most critical biotechnological applications for wastewater treatment. 1 The primary purification function in the activated sludge method involves activated sludge with filamentous bacteria and bacterial micelles as the main structure. 2 However, along with changes in the environmental conditions of the sludge, the filamentous bacteria will over-proliferate, resulting in a loose structure of the activated sludge flocs and slow settling, which leads to sludge bulking.…”