ABSTRACT
Three parallel bioreactors were operated with different inoculation of activated sludge (R1), intertidal sludge (ItS) (R2), and ItS-added AS (R3), respectively, to explore the effects of ItS bioaugmentation on the formation of salt-tolerant aerobic granular sludge (SAGS) and the enhancement of COD removal performance. The results showed that compared to the control (R1-2), R3 promoted a more rapid development of SAGS with a cultivation time of 25 d. Following 110-day cultivation, R3 exhibited a higher granular diameter of 1.3 mm and a higher hydrophobic aromatic protein content than that in control. Compared to the control, the salt-tolerant performance in R3 was also enhanced with the COD removal efficiency of 96.4% due to the higher sludge specific activity of 14.4 g·gVSS-1·d-1 and the salinity inhibition constant of 49.3 gL-1. Read- and genome-resolved metagenomics together indicated that a higher level of tryptophan/tyrosine synthase gene (trpBD, tyrBC) and enrichment of the key gene hosts Rhodobacteraceae, Marinicella in R3, which was about 5.4-fold and 1.4-fold of that in control, could be the driving factors of rapid development of SAGS. Furthermore, the augmented salt-tolerant potential in R3 could result from that R1 was dominated by Rhodospirillaceae, Bacteroidales, which carried more trehalose synthase gene (otsB, treS), while the dominant members Rhodobacteraceae, Marinicella in R3 were main contributors to the glycine betaine synthase gene (ectC, betB, gbsA). This study could provide deeper insights into the rapid development and improved salt-tolerant potential of SAGS via bioaugmentation of intertidal sludge, which could promote the application of hypersaline wastewater treatment.
Subject(s)
Sewage , Water Purification , Sewage/chemistry , Waste Disposal, Fluid/methods , Bioreactors , Salinity , AerobiosisABSTRACT
Petrochemicals are one of the pillar industries of China. Despite this, the treatment of petrochemical wastewater has long been seen as a massive challenge in the field of water pollution control, hindering the high-quality and sustainable development of the petrochemical industry. The majority of petrochemical enterprises and zones are located near rivers or seas, so their wastewater discharges can easily cause watershed or regional water ecological risks. Specifically, nitrogen pollution in petrochemical wastewater poses a significant threat to water ecological safety and human health. Sludge samples were collected from a petrochemical wastewater A/O nitrogen removal process line in a chemical industry zone in Shanghai. Metagenomic and metatranscriptomic methods were used to analyze the community structure of microorganisms, the functional characteristics of nitrogen removal bacteria, and the key nitrogen metabolism pathways in different sludges during the period when effluent water quality was stable and fluctuating. During the study, it was found that the nitrite and nitrate removal was relatively stable in this process, but ammonia oxidation fluctuated easily. In the study of microbial communities, it was found to be a nitrification-denitrification pathway that primarily removed nitrogen from the A/O process, and no genes related to ANAMMOX were detected. Approximately 90% of the functional genes responsible for removing nitrogen were responsible for denitrification, whereas only 0.17% of them were involved in the conversion of ammonia nitrogen in the nitrification process. Moreover, the abundance of ammonia-oxidizing bacteria in the process was extremely low, and the main genus was Nitrosomonas. It is likely that this is the main cause of fluctuations in ammonia nitrogen concentration in effluent due to water quality shocks in the process line.
