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Limited information is currently available on the assembly processes (deterministic vs. stochastic) shaping the compositions of key microbial communities in activated sludge (AS). The relative importance of deterministic and stochastic processes for key bacterial and archaeal assemblages (i.e., core-satellite and habitat generalist-specialist) in AS from 13 wastewater treatment plants in China was investigated using 16S rDNA amplicon sequencing. The results obtained indicated 1,388 and 369 core operational taxonomic units (OTUs), 1,038 and 1,683 satellite OTUs, 255 and 48 habitat generalist OTUs, and 192 and 111 habitat specialist OTUs for Bacteria and Archaea, respectively. The proportions of shared OTUs between core and habitat specialist communities were similar to or higher than those between core and habitat generalist communities, suggesting a stronger inter-linkage between the former two groups. Deterministic processes, indicated by abundance-based β-null models, were responsible for shaping core communities, in which NH 4 -N, OrgC/OrgN, Cr, and Ni were the main controlling factors. In contrast, satellite communities were predominantly influenced by stochastic processes. Moreover, we found that deterministic and stochastic processes were mainly responsible for shaping the assembly of habitat specialists and generalists, respectively. However, the influence of deterministic factors on habitat specialists remains unclear. The present study provides novel insights into the assembly mechanisms of AS microbial communities.

Limited information about the sludge quality is a major constraint for its usage and proper disposal. This study investigated the occurrence of 49 elements in sludge from 11 wastewater treatment plants (WWTPs) in Chongqing and Xiamen cities of China. The concentration of 46-detected elements ranged from 16.2 μg kg -1 (Pt) to 55.0 g kg -1 (Al) on dry solid basis in the sludge. The enrichment factor of most of the elements was > 1.5, indicating their possible anthropogenic origin. The precious metals had considerably higher enrichment factor ranging from 56.3 to 200,000. Principal component analysis clustered the samples from Chongqing and Xiamen separately to suggest strong spatial variations. Contamination factor, pollution loading index, and integrated pollution degree were calculated to evaluate the elemental pollution risk. The pollution loading index indicated unpolluted to highly polluted levels of the elements in the sludge. In addition, results from the ecotoxicological risk index showed an individual low to very high ecotoxicological risk posed by eight metal(loid)s (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in the WWTPs.

The occurrence and fate of pharmaceuticals and personal care products (PPCPs) was investigated in seven wastewater treatment plants (WWTPs) in Xiamen City, China. Special emphasis was placed on their co-occurrence and the mass balances of both dissolved and adsorbed PPCPs in influent, effluent, and sludge samples. Results showed that PPCPs were widely detected and their co-occurrence was observed both in the wastewater and sludge that can be attributed to either their similar usage or similar physicochemical properties. These results further emphasize that some specific PPCPs have the potential as indicators or surrogate compounds to reduce the number of targeted PPCPs. The occurrence and distribution of PPCPs also showed strong spatial variations, as the PPCP mass loads per inhabitant were positively correlated with the urbanization levels. Both the removal efficiencies of dissolved PPCPs from the aqueous phase and mass loss proportion of the total PPCPs were evaluated and compared. Overall, a measured total amount of 8500 g PPCPs entered the seven WWTPs daily via influent with 6640 g in the dissolved form, while 3450 g left the WWTPs. The large mass loads of antibiotics in the sludge and effluents indicated their potential adverse effects to the receiving environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)