Intensified efforts to curb transmission of the Severe Acute Respiratory Syndrome Coronavirus-2 might lead to an elevated concentration of disinfectants in domestic wastewater and drinking water in China, possibly resulting in the generation of numerous toxic disinfection byproducts (DBPs). In this study, the occurrence and distribution of five categories of DBPs, including six trihalomethanes (THMs), nine haloacetic acids (HAAs), two haloketones, nine nitrosamines, and nine aromatic halogenated DBPs, in domestic wastewater effluent, tap water, and surface water were investigated. The results showed that the total concentration level of measured DBPs in wastewater effluents (78.3 μg/L) was higher than that in tap water (56.0 μg/L, p = 0.05), followed by surface water (8.0 μg/L, p < 0.01). Moreover, HAAs and THMs were the two most dominant categories of DBPs in wastewater effluents, tap water, and surface water, accounting for >90%, respectively. Out of the regulated DBPs, none of the wastewater effluents and tap water samples exceeded the corresponding maximum guideline values of chloroform (300 μg/L), THM4 (80 μg/L), NDMA (100 ng/L), and only 2 of 35 tap water samples (67.6 and 63.3 μg/L) exceeded the HAA5 (60 μg/L) safe limit. HAAs in wastewater effluents showed higher values of risk quotient for green algae. This study illustrates that the elevated use of disinfectants within the guidance ranges during water disinfection did not result in a significant increase in the concentration of DBPs.

Lake Erhai is the second largest lake of Southwest China and an important drinking water source. The lake is currently defined as the preliminary stage of eutrophic states, but facing a serious threat with transfer into intensive eutrophication. The present study examined the dynamics of Microcystis blooms and toxic Microcystis in Lake Erhai during 2010, based on quantitative real-time PCR method using 16S rRNA gene specific for Microcystis and microcystin systhesis gene (mcy), and chemical analysis on microcystin (MC) concentrations. Total Microcystis cell abundance at 16 sampling sites were shown as an average of 1.7×10 7 cells l −1 (1.3×10 2 -3.8×10 9 cells l −1 ). Microcystin LR (MC-LR) and microcystin RR (MC-RR) were the main variants. The strong southwesterly winds, anticlockwise circular flows and geographical characteristics of lake and phytoplankton community succession impacted the distribution patterns of Chl a and MC in the lake. The concentration of Chl a and MC and abundances of total Microsytis and MC-producing Microsystis (MCM) were shown to be positively correlated with pH, DO and TP, negatively correlated with SD, NO 3 -N, TN/Chl a and TN/TP, and not correlated with NH 4 -N, TN, dissolved total nitrogen (DTN) and water temperatures. When TN/TP decrease, Microcystis tended to dominate and MC concentrations tended to increase, suggesting that the "TN/TP rule" can be partially applied to explain the correlation between the cyanobacterial blooms and nutrients N and P only within a certain nutrient level. It is speculated that N and P nutrients and the associated genes (e.g., mcy) may jointly drive MC concentration and toxigenicity of Microcystis in Lake Erhai.

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2-Methylisoborneol (MIB), along with geosmin, has been frequently associated with taste and odor (T&O) events in waters, and cyanobacterial species were considered the main producers in freshwater ecosystems. The detection and quantification of genes responsible for the synthesis of these odors on-site could be valuable for the prediction and treatment of T&O. In this study, SYBR Green and TaqMan real-time quantitative polymerase chain reaction (qPCR) assays were established on the basis of conserved regions in cyanobacterial MIB cyclase gene (mic) and applied to the quantification of potential MIB-producing cyanobacteria in waters. These two qPCR assays showed the prescribed values of amplification efficiency (0.976 and 1.023, respectively) with linearity (R 2 >0.99) in the range of 10 1 to 10 7 mic copies. Examination on environmental samples and cyanobacterial cultures indicated that qPCRs were rarely inhibited by background biomass, and the limit of quantification was at the level of 10 3 mic copies L −1 in natural waters. The seasonal variations of mic abundances in Lushui Reservoir, Donghu Lake, and Qinghai Lake of China were successfully quantified using the two qPCR protocols and indicated the applicability of these assays in field monitoring. Regression analysis revealed the positive correlation between mic abundance and MIB concentration, but no significant linear correlation was found between MIB-producing cyanobacteria and total cyanobacteria in investigated waters. The qPCR assays developed in this study could rapidly and reliably detect and quantify the abundance of potential cyanobacterial MIB producers, thereby providing a valuable tool for the prediction and early detection of T&O events.

A novel genus within Leptolyngbyaceae related to Leptolyngbya morphotypes, Scytolyngbya, gen. nov., is described based on a polyphasic approach in the present study. From a freshwater sample with filaments of oscillatorean cyanobacteria from a well in Hubei Province, China, Scytolyngbya (type species: Scytolyngbya timoleontis, sp. nov.) was found to possess richly and repeatedly false branches and thick sheaths, which distinguishs this genus from Leptolyngbya sensu stricto. Phylogenetic analysis based on 16S rRNA sequences showed that this species was clustered into the Leptolyngbyaceae and separated from the type species Leptolyngbya boryana. The secondary structures of 16S-23S rRNA intergenic spacer of Scytolyngbya timoleontis did not correspond to any previously described species in cyanobacteria.

The earthy-musty compounds geosmin and 2-methylisoborneol (MIB) produced by cyanobacteria are considered as the main biological causes of off-flavor events, especially in aquatic ecosystems. More than 50 filamentous cyanobacteria species have been documented as geosmin or MIB producers; however, little is known about the species coproducing these two metabolites. In this study, an epiphytic sample was collected from a river in Hubei, China. Three isolated strains (A2, B2, and B4) producing earthy odors were successfully isolated and identified as the cyanobacterium Leptolyngbya bijugata Anagnostidis et Komárek 1988 based on morphology and 16S rDNA sequences. Gas chromatography analysis confirmed that the isolated L. bijugata strains were geosmin and MIB coproducers, with accumulation ranging from 13.6 to 22.4 and 12.3 to 57.5 μg L −1 , respectively. The partial fragments of geosmin and MIB synthesis genes in the L. bijugata strains were cloned and sequenced. Further sequences and phylogenetic analysis indicated the high conservation and a common origin of these genes in cyanobacteria. This study is the first to report and characterize the coproduction of geosmin and MIB by L. bijugata, representing a new source for potential risk of off-flavor events.

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