Domestic wastes, ranging from sewage and sludge to municipal solid waste, are usually treated in bioprocessing systems. These systems are regarded as main conduits for the elevated levels of antibiotic resistance genes (ARGs) observed in the environment. This paper mainly reviews recent studies on the occurrence and dynamics of ARGs in wastewater bio-treatment systems and discusses the ins and outs of ARG dissemination from the perspective of the microbial community. Our analysis shows that concentration of antibiotics through adsorption to microbial aggregates triggers the bacteria to acquire ARGs, which can be facilitated by the presence of mobile genetic elements. Notably, the acquisition and flow of ARGs during the rapid dissemination process is directed towards and for the best interests of the microbial community as a whole, and is influenced by surrounding nutrient levels, toxicant types, and sensitivities of the species in the prevailing antibiotic-stressed conditions. Furthermore, our review argues that predation of ARG-carrying bacteria by bacteriophages does periodically enhance the accessibility of ARGs to bacteria, which indirectly facilitates the recruitment of ARGs into environmental microbial communities.