Evaluation of changes in M. aeruginosa growth and microcystin production under phosphorus starvation via transcriptomic surveys.

Phosphorus (P) is an important nutrient for the growth and metabolism of algae. Although P typically limits the growth of algae, little is known regarding the molecular response of Microcystis aeruginosa under P starvation. The transcriptomic and physiological responses of Microcystis aeruginosa to P starvation were investigated in this study. P starvation affected the growth, photosynthesis, and Microcystin (MC) production of Microcystis aeruginosa and triggered cellular P-stress responses for 7 days. In terms of physiology, P starvation inhibited the growth and MC production, while the slight promotion of photosynthesis in Microcystis aeruginosa compared to P-replete. For transcriptome, the down-regulation of genes related to MC production controlled by mcy genes and ribosome metabolism (17 genes encoding ribosomal proteins) was observed while transport genes (sphX and pstSAC) were significantly upregulated. In addition, some other genes are related to photosynthesis and the use of other forms of P displayed increases or decreases in transcripts abundance. These results suggested that the limitation of P had a diverse performance on aspects of growth and metabolism in M. aeruginosa and obviously enhanced the ability to adapt to the P stress environment. They provide a comprehensive understanding of the P physiology of Microcystis aeruginosa and theoretical support for eutrophication.

Application of fluorescence spectra and molecular weight analysis in the identification of algal organic matter-based disinfection by-product precursors.

Algal organic matter (AOM) is considered to be threatening for the consumption of disinfectants and the formation of disinfection by-products (DBPs) during the disinfection process. Incompatible parameters in the conventional pretreatment of algal-laden water will lead to counterproductive results, such as AOM release. Therefore, the generation of AOM and its conversion to DBPs during pretreatment should be observed. The characteristics of DBPs from extracellular organic matter (EOM) and intracellular organic matter (IOM) were epitomized and simulation experiments were conducted in deionized (DI) water and source water under pretreatment conditions. Differences in DBP formation between the different backgrounds during chlorination and powdered activated carbon (PAC) treatment were investigated. Instead of monotonous excitation-emission matrix (EEM) spectra, molecular weight (MW) fractionation was simultaneously applied to elucidate the mechanisms of chlorination and PAC adsorption on AOM-based DBPs. The fluorescence regional integration (FRI) EEM results showed a clear correlation between the fluorescent properties and MW distribution of AOM. A decreasing trend was observed after a rapid increase in fluorescence intensity during the chlorination and PAC treatment of water samples in the simulation experiments in deionized (DI) water and source water. The DBP formation potential (FP) in the source water was consistent with the change in AOM during chlorination and PAC adsorption. In addition, EEM showed decent predictability of AOM-based trihalomethanes (THM) FPs (R2 = 0.77-0.99) invoking a combination with MW fractionation. Macromolecular protein compounds were highly correlated with the formation of dichloroacetonitrile (DCAN) (R2 = 0.89-0.98). These post-mortems results imply that EEM spectra are a useful tool for identifying AOM-based precursors to reveal the accurate environmental fate and risk assessments of AOM.

Transcriptome analysis of changes in M. aeruginosa growth and microcystin production under low concentrations of ethinyl estradiol.

Ethinyl estradiol (EE2) is a synthetic environmental estrogen with considerable estrogenic activity. It has been found to consequently pose a significant threat to the aquatic ecosystem. Harmful algal blooms are a major aquatic ecological issue. However, the relationship between EE2 and cyanobacterial bloom is mainly unknown. In this study, the physiological and molecular responses of Microcystis aeruginosa to EE2 exposure were investigated. A low level of EE2 (0.02 µg/L) significantly enhanced the growth of algal cells (P < 0.05), whereas higher concentrations of EE2 (0.2-200 µg/L) inhibited it. EE2 at doses ranging from 0.02 to 200 µg/L promoted the production of microcystins (MCs), with genes mcyABD playing a key role in the regulation of MC synthesis. The alterations of chlorophyll-a, carotenoid, and phycocyanin contents caused by EE2 showed the same trend as cell growth. At the molecular level, 200 µg/L EE2 significantly down-regulated genes in photosynthetic pigment synthesis, light harvesting, electron transfer, NADPH, and ATP generation. High concentrations of EE2 caused oxidative damage to algal cells on the 4th d. After 12d exposure, although there was no significant change in superoxide dismutase (SOD) content and no damage observed in membrane lipids, genes related to SOD and glutathione were changed. In addition, due to the down-regulation of pckA, PK, gltA, nrtA, pstS, etc., carbon fixation, glycolysis, TCA cycle, nitrogen and phosphorus metabolism were hindered by EE2 (200 µg/L). Gene fabG in fatty acid biosynthesis was significantly up-regulated, promoting energy storage in cells. These findings provide important clues to elucidate the effects and mechanisms of cyanobacterial blooms triggered by EE2 and help to effectively prevent and control cyanobacterial blooms.

Environmental estrogens in surface water and their interaction with microalgae: A review.

Environmental estrogens (EEs) have received extensive attention because they interfere with biological endocrine and reproduction systems by mimicking, antagonizing, or otherwise affecting the actions of endogenous hormones. Additionally, harmful algal blooms have become a global problem in surface water. Microalgae, as an essential primary producer, is especially important for aquatic life and the entire ecosystem. The presence of EEs in surface water may be a potential promoting factor for algal blooms, and microalgae may have effects on the degradation of EEs. This review focuses on the distribution and pollution characteristics of EEs in global surface waters, effects of single and mixed EEs on microalgae regarding growth and toxin production, mechanisms of EEs on microalgae at the cellular and molecular level. The impacts of microalgae on EEs were also discussed. This review provides a risk assessment of EEs and identifies essential clues that will aid in formulating and revising the relevant standards of surface water regarding EEs, which is significant for ecosystems and human health.

Microbial diversity characteristics and the influence of environmental factors in a large drinking-water source.

Although the influence of environmental factors on the microbial community in water sources is crucial, it is seldom evaluated. The seasonal relationship between microbial diversity of bacteria and fungi and environmental factors was investigated in a large drinking-water reservoir using Illumina MiSeq sequencing. Forty-one bacterial phyla and nine fungal phyla were analyzed in the Qingcaosha Reservoir, Shanghai, China. The predominant bacterial phyla were Actinobacteria, Proteobacteria, Bacteroidetes, and Cyanobacteria, with the maximum relative abundance of 46%, 36.6%, 16.1%, and 14.9%, respectively. Actinobacteria were observed to be the predominant bacterial phylum during spring and summer. The maximum relative abundance of unclassified fungi appeared in summer (98.8%), which was higher than that of Ascomycota and Basidiomycota (11.7% and 8.2%, respectively). Principal coordinate analysis (PCoA) results showed that the structural similarity in the bacterial community was greater during summer and winter; however, the fungal community exhibited a greater similarity during spring and summer. 2-Methylisoborneol (2-MIB), an olfactory compound produced by microorganisms, was detected at a concentration of 8.97 ng/L during summer, which was slightly lower than the olfactory threshold (10 ng/L). The positive correlation between Actinobacteria and unclassified fungi and 2-MIB (p < 0.05) confirmed that Actinobacteria and unclassified fungi produced 2-MIB. The chemical oxygen demand (COD) was 1.48-1.94 mg/L, and the maximum concentrations of total nitrogen (TN) and total phosphorus (TP) were 2.1 mg/L and 0.5 mg/L, respectively. Chloroflexi were negatively correlated with COD (p < 0.05) but positively correlated with TP (p < 0.01). Nitrospirae were negatively correlated with COD (p < 0.05), but positively correlated with TN (p < 0.05). Among the classified fungi, Rozellomycota, Basidiomycota (p < 0.05), and Chytridiomycota (p < 0.01) were positively correlated with TP. Therefore, the relative abundance of predominant bacteria was affected by various environmental factors; however, fungi were mainly influenced by TP.

Algae removal performance of UV-radiation-enhanced coagulation for two representative algal species.

Algal blooms severely impact the ecological environment and human health, as well as drinking water supplies and treatment systems. This study investigated UV-radiation-enhanced aluminum (Al)-based coagulation for the removal of two representative algal species (Microcystis aeruginosa and Cyclotella sp.) which are responsible for most fresh water algal bloom in different seasons. The results demonstrated that the UV-Al process can enhance algae removal, and simultaneously control algal organic matter (AOM) release. Comparing with Microcystis aeruginosa, Cyclotella sp. was more sensitive to UV irradiation and its activity was severely inhibited by 240 s of UV irradiation; intracellular reactive oxygen species (ROS) increased sharply then decreased rapidly, and SEM images showed cell walls exhibited substantial compression. UV irradiation decreased the zeta potential, which might have contributed to algae removal. Approximately 93.5% of Microcystis aeruginosa cells and 91.4% of Cyclotella sp. cells were removed after 240 s of UV irradiation with 0.4 mmol/L Al. The MCs concentrations after Al coagulation were low (<100 ng/L). The DOC of Microcystis aeruginosa and Cyclotella sp. was also lower (1.2 and 1.6 mg/L, respectively) than the national standard level after UV-Al process. This study highlights the practical application of UV irradiation for enhancing algae removal and simultaneously controlling AOM release in water treatment plants, which is a simple and promising technology. This result also indicates that the water treatment parameters should be adjusted according to the algae species present in different seasons, especially for diatom which needs low UV irradiation and Al dosage.

Removal of cyanobacteria and control of algal organic matter by simultaneous oxidation and coagulation - comparing the H2O2/Fe(II) and H2O2/Fe(III) processes.

Cyanobacterial blooms in drinking water are worldwide concern. It is known that pre-oxidation enhanced coagulation can be more efficient at removing algae than traditional coagulation. However, its application is hindered by high oxidant/coagulant consumption and the resultant potential health risk, in the form of algal organic matter (AOM) released during oxidation. To remove the cyanobacteria and meanwhile ensure cell integrity, H2O2/Fe(II) and H2O2/Fe(III), which have been widely used to degrade organic pollutants in waters, are proposed in this study. The removal efficiency of Microcystis aeruginosa (M. aeruginosa) under various oxidant/coagulant dosages, AOM release and cell integrity, as well as floc formation and morphology were investigated with these simultaneous oxidation/coagulation processes. The results show that the removal efficiency was higher than 95% with H2O2/Fe(II) and H2O2/Fe(III) under 100 µmol/L H2O2 and Fe. In addition, neither method was found to damage the algal cells in 50-200 µmol/L H2O2 dosing concentrations. It was also found that AOM, including microcystins (MCs), was well controlled owing to the oxidation of H2O2 or hydroxyl radicals, and in-situ Fe(III) settled down the cells in the processes. Compared with H2O2/Fe(II), H2O2/Fe(III) could remove algae efficiently and control AOM release with lower H2O2 (50 µmol/L) and Fe(III) (80 µmol/L) dosages, which suggests that a low chemical consumption is suitable for this simultaneous oxidation/coagulation processes. This is a promising technology for the removal of algae from drinking water in a clean, economical way.

Transcriptomic survey on the microcystins production and growth of Microcystis aeruginosa under nitrogen starvation.

Cyanobacteria are a vital component of freshwater phytoplankton, and many species are recognized for their ability to produce toxins and harmful algal blooms (HABs). Nitrogen is an essential element of all the complex macromolecules in algal cells. However, the underlying molecular mechanism of the changes in transcriptomic patterns and physiological responses in response to N starvation is poorly understood. The transcriptomes were generated via RNA-sequencing (RNA-Seq) technology to study the major metabolic pathway under N starvation. The results shed light on the mechanism of toxin production and physiological adaptations in Microcystis aeruginosa (M. aeruginosa). The cell density gradually increased during the first two days then declined over time and was finally stable at (15.50 ±â€¯0.5) × 105 cell mL-1 after 6 days. The chlorophyll-a content and phycocyanin content of M. aeruginosa increased during the first two days and subsequently decreased markedly over time under N starvation. The variable to maximum chlorophyll fluorescence ratio (Fv/Fm ratio) decreased with time under N starvation. Most photosynthesis genes have similarity decreasing trends with growth physiological changes. The microcystins (MCs) levels generally increased first, reaching a peak value with 1.35 pg cell-1 on the fifth day, and then remained roughly constant. The genes involved in N metabolism-related gene expression were upregulated to maintain normal biological activity, while the genes involved in photosynthesis-related gene expression were downregulated to save energy. All genes encoding algae toxin synthesis were upregulated under N starvation. The observed expression patterns demonstrate that all MCs genes respond similarly to MCs production within the cell. Our results indicate the response mechanism of M. aeruginosa under N starvation and provide a comprehensive understanding of N-controlling cyanobacteria and MCs synthesis.

Highly Sensitive Dissolved Oxygen Sensor with a Sustainable Antifouling, Antiabrasion, and Self-Cleaning Superhydrophobic Surface.

Long-term sensing of dissolved oxygen in aqueous solution always suffers from adherence of algae, barnacles, and clams and formation of biofilms on the sensor surface, which strongly influences the diffusion of oxygen into the sensor film. Metabolism of these adhered species consumes oxygen and causes bias on sensor readout. Therefore, commercial sensors are equipped with mechanical brushes to constantly clean the sensor surface, which significantly complicates the sensor design and causes damage to the sensor surface. In addition, extra energy storage and mechanical structures are required, which make an optical sensor bulky and limit its service life. We have developed a robust and highly sensitive dissolved oxygen sensor with good mechanical stability and self-cleaning capability. The sensor was fabricated by doping oxygen-sensitive probe PtTFPP with superhydrophobic coating. The 3 to 5 nm micro/nanostructures formed from silica sol were solidified with silicone resin, which endowed the sensor film with excellent mechanical stability. The sensor film exhibits antifouling, antiabrasion, and self-cleaning properties. There is no need of mechanical brushes to clean sensor surfaces, which greatly simplifies the sensor design. Owing to the porous structure, the sensor shows high quenchability, with I 0/I 100 of 77. All these features guarantee that the sensor could be used in harsh and dirty conditions for long-term monitoring of dissolved oxygen concentration.

Urea dynamics during Lake Taihu cyanobacterial blooms in China.

Lake Taihu, the third largest freshwater lake in China, suffers from harmful cyanobacteria blooms caused by Microcystis spp., which do not fix nitrogen (N). Reduced N (i.e., NH4+, urea and other labile organic N compounds) is an important factor affecting the growth of Microcystis. As the world use of urea as fertilizer has escalated during the past decades, an understanding of how urea cycling relates to blooms of Microcystis is critical to predicting, controlling and alleviating the problem. In this study, the cycling rates of urea-N in Lake Taihu ranged from non-detectable to 1.37 µmol N L-1 h-1 for regeneration, and from 0.042 µmol N L-1 h-1 to 2.27 µmol N L-1 h-1 for potential urea-N removal. The fate of urea-N differed between light and dark incubations. Increased 15NH4+ accumulated and higher quantities of the removed urea-15N remained in the 15NH4+ form were detected in the dark than in the light. A follow-up incubation experiment with 15N-urea confirmed that Microcystis can grow on urea but its effects on urea dynamics were minor, indicating that Microcystis was not the major factor causing the observed fates of urea under different light conditions in Lake Taihu. Bacterial community composition and predicted functional gene data suggested that heterotrophic bacteria metabolized urea, even though Microcystis spp. was the dominant bloom organism.

Evaluation of changes in Microcystis aeruginosa growth and microcystin production by urea via transcriptomic surveys.

The freshwater cyanobacteria, Microcystis aeruginosa (M. aeruginosa), is well known to produce microcystins (MCs) and induce the formation of harmful algal blooms (HABs) in aquatic environments, but the effects that urea fertilizer has on cyanobacterial growth and toxin production from a molecular biology perspective remain poorly understood. We evaluated changes in the growth and toxicity of M. aeruginosa cultured under different conditions of nitrogen (N) starvation (NN), low nitrogen (LN), and high nitrogen (HN). Cell density and chlorophyll-a concentrations decreased in cyanobacteria exposed to N starvation and increased following the addition of urea, whereas MCs content increased to a peak and then decreased after urea addition. Transcriptomic analysis confirmed that most genes encoding MCs and genes involved in N metabolic pathways were upregulated under N starvation and LN conditions, whereas these genes were downregulated under HN conditions. Our results offer important insights into the exploring N in controlling the formation of HABs and toxin production based on both physiological and molecular response.

Effects of arginine on the growth and microcystin-LR production of Microcystis aeruginosa in culture.

Although toxic cyanobacterial blooms and their toxins threaten drinking water and ecology and are promoted by nutrient loading, the precise nutrient regime that increases cyanobacterial populations and toxin production is poorly understood. Here, the influences of arginine (Arg), as a common amino acid with high nitrogen content, on the growth and microcystins (MCs) production of Microcystis aeruginosa (M. aeruginosa) were investigated by an isotope method (15N). The results showed that the biomass and production of microcystin-LR (MC-LR) increased with an increase in initial Arg concentrations in the range of 0.3-1.4 mmol-N L-1, whereas a higher Arg concentration (3.6 mmol-N L-1) inhibited the growth. MC-LR on different days (days 0, 6, 12, and 18) was detected by liquid chromatography with tandem mass spectrometry (LC-MS/MS) after incubation with 15N-Arg. The MC-LR molecular weight increased from 995 to 1004 with 100% relative abundance with 10 15N atoms bound by the Adda, Arg (4 15N), Glu, Mdha, Ala, Leu, and MeAsp residues on day 18. It seems that there was a sequential order when M. aeruginosa assimilated Arg to synthesize MC-LR. The Arg residue in the molecule of MC-LR was the last one to be labeled by 15N from 15N-arginine. This study not only presents a deeper insight into the biosynthesis of free amino acids that are incorporated into MCs but also reminds us of the potential risk caused by Arg, which should arouse concerns.

Cyanobacterium removal and control of algal organic matter (AOM) release by UV/H2O2 pre-oxidation enhanced Fe(II) coagulation.

Harmful algal blooms in source water are a worldwide issue for drinking water production and safety. UV/H2O2, a pre-oxidation process, was firstly applied to enhance Fe(II) coagulation for the removal of Microcystis aeruginosa [M. aeruginosa, 2.0 (±0.5) × 106 cell/mL] in bench scale. It significantly improved both algae cells removal and algal organic matter (AOM) control, compared with UV irradiation alone (254 nm UVC, 5.4 mJ/cm2). About 94.7% of algae cells were removed after 5 min UV/H2O2 pre-treatment with H2O2 dose 375 µmol/L, FeSO4 coagulation (dose 125 µmol/L). It was also certified that low residue Fe level and AOM control was simultaneously achieved due to low dose of Fe(II) to settle down the cells as well as the AOM. The result of L9(3)4 orthogonal experiment demonstrated that H2O2 and FeSO4 dose was significantly influenced the algae removal. UV/H2O2 induced an increase of intracellular reactive oxidant species (ROS) and a decrease in zeta potential, which might contribute to the algae removal. The total microcystins (MCs) concentration was 1.5 µg/L after UV/H2O2 pre-oxidation, however, it could be removed simultaneously with the algae cells and AOM. This study suggested a novel application of UV/H2O2-Fe(II) process to promote algae removal and simultaneously control AOM release in source waters, which is a green and promising technology without secondary pollution.

A review on factors affecting microcystins production by algae in aquatic environments.

Microcystins, a toxin produced by Microcystis aeruginosa have become a global environmental issue in recent years. As a consequence of eutrophication, microcystins have become widely disseminated in drinking water sources, seriously impairing drinking water quality. This review focuses on the relationship between microcystins synthesis and physical, chemical, and biological environmental factors that are significant in controlling their production. Light intensity and temperature are the more important physical factors, and in many cases, an optimum level for these two factors has been observed. Nitrogen and phosphorus are the key chemical factors causing frequent occurrence of harmful algal blooms and microcystins production. The absorption of nutrients and metabolic activities of algae are affected by different concentrations and forms of nitrogen and phosphorus, leading to variations in microcystins production Metal ions and emerging pollutants are other significant chemical factors, whose comprehensive impact is still being studied. Algae can also interact with biological agents like predators and competitors in aquatic environments, and such interactions are suggested to promote MCs production and release. This review further highlights areas that require further research in order to gain a better understanding of microcystins production. It provides a theoretical basis for the control of microcystins production and releasing into aquatic environments.

Comparative effects of inorganic and organic nitrogen on the growth and microcystin production of Microcystis aeruginosa.

Nitrogen causes the frequent occurrence of harmful algal blooms and possible microcystin production. The effects of ammonia and alanine (Ala) on the growth and microcystin production of Microcystis aeruginosa were investigated using an isotope tracer ((15)N). The results indicated that Ala was directly used by M. aeruginosa and contributed to biomass formation amounting to 2.1 × 10(7) cells mL(-1) on day 48, compared with only 6.2 × 10(6) cells mL(-1) from ammonia alone. Microcystin-LR production with Ala was less than that of ammonia, which peaked at 50.2 fg cell(-1) on day 6. Liquid chromatographic analysis with tandem mass spectrometry of (15)N-microcystin-LR suggested that (15)N from ammonia was probably synthesized into the arginine residue. By contrast, (15)N from Ala was assimilated into the Ala, leucine, the iso-linked (2R,3S)-3-methylaspartic acid, arginine, and certain unusual C20 amino acid residues. The results represent the forward steps in the determination of the nitrogen forms that fuel toxin production and blooms.

Effect of urea on growth and microcystins production of Microcystis aeruginosa.

The effects of urea on the growth and toxin content of Microcystis aeruginosa isolated from Dianchi Lake in China were investigated. Experiments were carried out in lab using (15)N isotopic technique to characterize urea-N biosynthesis to microcystins. High urea concentration (3.6 mmol-N L(-1)) would restrict the growth of M.aeruginosa and the production of microcystin-LR, while low urea concentration (0.4-1.4 mmol-N L(-1)) would promote the growth of M.aeruginosa and the production of microcystin-LR. The (15)N labeling experiment further demonstrated that there existed selectivity when M.aeruginosa assimilated urea to form its structure. The majority of M.aeruginosa assimilated 1 urea molecule at first which was biosynthesized into the Ala or Leu residue. On day 18, The m/z=1004 parent ion assimilated 9 (15)N except that the Mdha residue did not assimilate any urea-(15)N. The results give deeper insight to the biosynthesis of urea into microcystins.

Effects of bromide and iodide ions on the formation of disinfection by-products during ozonation and subsequent chlorination of water containing biological source matters.

This study aims to investigate the influence of the coexistence of halogen ions (bromide/iodide) and biological source matters on the speciation and yield of trihalomethanes (THMs), haloacetic acids (HAAs), and N-nitrosodimethylamine (NDMA) during the ozonation and subsequent chlorination of water. The results show that the concentrations of brominated THMs and iodinated THMs increased with increasing bromide and iodide concentration. These results may be attributed to the higher reactivity of hypobromous acid and hypoiodous acid generated from the ozonation and subsequent chlorination in the presence of bromide or iodide ions. The presence of bromide increased the species of brominated HAAs. There was a shift from chlorinated HAAs to brominated HAAs after increasing the concentration of bromide. The effect of iodide on HAA formation was more complex than bromide. For most samples, the concentration of total HAAs (T-HAAs) increased to the maximum and then decreased with increasing iodide concentration. The components of the organic precursors also significantly influenced the formation of brominated and iodinated disinfection by-products (Br-DBPs and I-DBPs). Humic acids produced more CHBr3 (596.60 µg/L) than other organic materials. Microcystis aeruginosa cells produced the most tribromoacetic acid (TBAA, 84.16 µg/L). Furthermore, the yield of NDMA decreased with increasing bromide concentration, indicating that the formation of NDMA was inhibited by the high concentration of bromide.

The effects of anaerobic fermentation on dehydrated sludge.

Dehydrated sludge with two concentrations of total suspended solids (high: 50 g/L TSS; low: 20 g/L TSS) were studied for 20 d to investigate the effects of anaerobic fermentation on sludge properties. The results showed that the soluble chemical oxygen demand (SCOD) of high-concentration sludge was 16.53 g/L, much higher than that from the low one. The SCOD/total nitrogen ratio of high-concentration sludge varied from 8 to 14.29 g/g, indicating that the sludge could serve as a carbon source for biological denitrification. High-concentration sludge showed a short-chain fatty acid yield of 11.29 g COD/L, much higher than that from low-concentration sludge. The specific resistance of the sludge to filtration (SRF) increased with fermentation time. The quantity of low-speed centrifugation substances (LSCS) was the main factor that influenced the reduction of dehydration. The correlation coefficient between the SRF and protein content in the LSCS layer was significantly positive.

Speciation and formation of iodinated trihalomethane from microbially derived organic matter during the biological treatment of micro-polluted source water.

Water sources are micro-polluted by the increasing range of anthropogenic activities around them. Disinfection byproduct (DBP) precursors in water have gradually expanded from humic acid (HA) and fulvic acid to other important sources of potential organic matter. This study aimed to provide further insights into the effects of microbially derived organic matter as precursors on iodinated trihalomethane (I-THM) speciation and formation during the biological treatment of micro-polluted source water. The occurrence of I-THMs in drinking water treated by biological processes was investigated. The results showed for the first time that CHCl2I and CHBrClI are emerging DBPs in China. Biological pre-treatment and biological activated carbon can increase levels of microbes, which could serve as DBP precursors. Chlorination experiments with bovine serum albumin (BSA), starch, HA, deoxyribonucleic acid (DNA), and fish oil, confirmed the close correlation between the I-THM species identified during the treatment processes and those predicted from the model compounds. The effects of iodide and bromide on the I-THM speciation and formation were related to the biochemical composition of microbially derived organic precursors. Lipids produced up to 16.98µgL(-1) of CHCl2I at an initial iodide concentration of 2mgL(-1). HA and starch produced less CHCl2I at 3.88 and 3.54µgL(-1), respectively, followed by BSA (1.50µgL(-1)) and DNA (1.35µgL(-1)). Only fish oil produced I-THMs when iodide and bromide were both present in solution; the four other model compounds formed brominated species.

The effect of continuous Zn (II) exposure on the organic degradation capability and soluble microbial products (SMP) of activated sludge.

This study describes the change of organic degradation capability and soluble microbial products (SMP) generated in activated sludge under continuous exposure to Zn (II) in a sequencing batch reactor (SBR). In 338 days of operation, the added Zn (II) concentrations were gradually increased from 50 to 100, 200, 400 to 600 and 800 mg/L. Results showed that after adaptation, the activated sludge could endure 400mg/L Zn (II) without showing evident reduction in organic degradation ability (92±1% of chemical oxygen demand (COD) removal in stable state). However, when 600 and 800 mg/L Zn (II) were applied, the effluent water quality significantly deteriorated. Meanwhile, under increasing Zn (II) concentrations, the SMP content in the activated sludge, together with its main biochemical constituents, first increased slightly below 400mg/L of Zn (II), then rose sharply under 600 and 800 mg/L Zn (II). Furthermore, a close correlation was found between SMP content and effluent soluble COD in both the Experimental Reactor and Control Reactor. In addition, the Zn (II) concentrations in the effluent and SMP extraction liquid were further analyzed and discussed to reveal the role that SMP constituents played in defense and resistance to the toxicity of Zn (II).