Transcriptome analysis of tea (Camellia sinensis) leaves in response to ammonium starvation and recovery.

The tea plant is a kind of ammonium-preferring crop, but the mechanism whereby ammonium (NH4 +) regulate its growth is not well understood. The current study focused on the effects of NH4 + on tea plants. Transcriptomic analysis was performed to investigate the early- and late-stage NH4 + deprivation and resupply in tea plants shoots. Through short- and long-term NH4 + deficiency, the dynamic response to NH4 + stress was investigated. The most significant effects of NH4 + deficiency were found to be on photosynthesis and gene ontology (GO) enrichment varied with the length of NH4 + deprivation. Enriched KEGG pathways were also different when NH4 + was resupplied at different concentrations which may indicate reasons for tolerance of high NH4 + concentration. Using weighted gene co-expression network analysis (WGCNA), modules related to significant tea components, tea polyphenols and free amino acids, were identified. Hence, NH4 + could be regarded as a signaling molecule with the response of catechins shown to be higher than that of amino acids. The current work represents a comprehensive transcriptomic analysis of plant responses to NH4 + and reveals many potential genes regulated by NH4 + in tea plants. Such findings may lead to improvements in nitrogen efficiency of tea plants.

Genome-wide identification, characterization, and expression analysis of the ammonium transporter gene family in tea plants (Camellia sinensis L.).

As a preferred nitrogen form, ammonium (NH4 + ) transport via specific transporters is particularly important for the growth and development of tea plants (Camellia sinensis L.). However, our understanding of the functions of the AMT family in tea plants is limited. We identified and named 16 putative AMT genes according to phylogenetic analysis. All CsAMT genes were divided into three groups, distributed on 12 chromosomes with only one segmental duplication repetition. The CsAMT genes showed different expression levels in different organs, and most of them were expressed mainly in the apical buds and roots. Complementation analysis of yeast mutants showed that CsAMTs restored the uptake of NH4 + . This study provides insights into the genome-wide distribution and spatial expression of AMT genes in tea plants.

Influence of different nitrogen sources on carbon and nitrogen metabolism and gene expression in tea plants (Camellia sinensis L.).

Nitrogen plays an important role in plant growth and development, with different nitrogen forms also having an impact on carbon/nitrogen metabolism. Unlike most plants, tea plants prefer ammonium over nitrate. In this paper, we focused on how different nitrogen sources regulate the carbon/nitrogen metabolism in tea plants. Tea seedlings of 'Longjing 43' were cultivated hydroponically in four different solutions (zero-nitrogen, only NH4+, only NO3- and mixed nitrogen (NH4+: NO3- = 1:1). We analyzed characteristic components of tea plants and related genes in carbon and nitrogen metabolism. Tea polyphenols and catechins representing carbon pool, increased when NO3- was supplied as the nitrogen source, and similar findings were recorded in the zero-nitrogen treatment. The expression of most catechins biosynthesis-related genes was up regulated under NO3- and zero-N treatment, that was associated with tea polyphenols and catechins changes. Compared with NO3- as the nitrogen source, NH4+ and mixed nitrogen treatments had a positive effect on the accumulation of amino acids, especially theanine, glutamate and arginine, and these components contribute to the freshness flavor of tea. The expression of ammonium-assimilation genes was also up-regulated with NH4+ supply. Under mixed nitrogen treatment, the ratio of total polyphenols to free amino acids (PP/AA) was between sole NH4+ and NO3- supply. Therefore, compared with single nitrogen source, carbon and nitrogen metabolism of tea plant was more balanced under mixed nitrogen treatment. The results suggested that NO3- as the nitrogen source promoted the biosynthesis of catechins enriching the carbon pool, whereas NH4+ supply was more conducive to nitrogen metabolism, indicating that different nitrogen sources could affect the carbon and nitrogen balance.

[Effects of Dissolved Oxygen on Nutrient Removal Performance and Microbial Community in Low Carbon/Nitrogen Municipal Wastewater Treatment Process].

To explore the effects of dissolved oxygen (DO) on the treatment of low carbon/nitrogen municipal wastewater, this study examined the characteristics of the microbial community in a low carbon source environment. The treatment process was conducted with the aeration area having DO concentrations of 2-3, 1-2, and lower than 1 mg·L-1. The results demonstrated that reduced DO concentration in the aeration area increased the efficiency of the nitrogen removal process by 20.23% and 80.54%, for external and internal carbon sources, respectively. Similarly, the efficiency of internal carbon source utilization in the phosphorus removal process increased by 13.89%, thus enhancing the nutrient removal efficiency of the low carbon/nitrogen wastewater treatment system. High-throughput sequencing and RDA analysis showed that reduced oxygen concentration motivated an adjustment in microbial community structure, causing functional microorganisms (i.e., Dechloromonas) to become dominant. In addition, the upregulation of genes associated with energy production and conversion, signal transduction, substrate transport, and metabolism provided favourable nutritional conditions for the proliferation of functional microorganisms in low carbon source conditions. This study provides a theoretical basis for improving the growth of microorganisms involved in the nutrient removal process when treating low carbon/nitrogen municipal wastewater.

[Strengthening Effect of Different Cattail Pretreatment Methods on the Denitrification of Horizontal Subsurface Flow in a Constructed Wetland].

Nitrogen removal in constructed wetlands (CWs) is highly affected by the supply of organic carbon. Thus, to enhance nitrogen removal in the horizontal subsurface flow of CWs, plant carbon sources were added during the downstream portion of the wetland. Moreover, the characteristics of static release and the denitrification potential of Typha were evaluated using three different pretreatment methods (i.e., minced, acid-heated, and alkali-heated). The average concentrations of COD released and the nitrate removal rate with the alkali-heated, acid-heated, and minced Typha were 89.57 mg·L-1 and 75.2%, 67.27 mg·L-1 and 67.2%, and 54.45 mg·L-1 and 23.5%, respectively. The results showed that different pretreatment methods resulted in the release of different amounts of acetic acid, and the alkali-heated Typha performed much better than the other pretreatments. Therefore, the alkali-heated Typha was selected and added to the middle of the horizontal subsurface flow CW, which improved the nitrogen-removal rate significantly; the average removal rate of TN and TP was higher than that of a control CW by 30.3% and 33.9%, respectively. However, the COD concentration of the CW with the alkali-heated Typha was not significantly increased.

[Influence of Sludge Retention Time on the Performance and Stability of Mesophilic Anaerobic Co-digestion of Food Waste with Waste Activated Sludge].

Two parallel digestion systems of food waste (FW) and waste-activated sludge (WAS) were successfully initiated using a continuous stirred-tank reactor (CSTR), and the effect of different reduction extents of sludge retention time (SRT) on the co-digestion of FW and WAS was investigated. SRT Reduction extents longer than 8.3 d were not conducive to the stable operation of the co-digestion system when the organic load rate (OLR) was increased. The reduction extent of SRT should be reduced gradually from 5 d to 0.9 d to achieve high load and stable operation of the co-digestion of FW and WAS. After a long-term operation (approximately 282 d), the co-digestion reached stable operation at SRT of 9.1 d and OLR (calculated by COD) of (12.9±1.5) g·(L·d)-1. The corresponding methane production, methane yield (calculated by COD), pH, and volatile fatty acid (VFA, calculated by COD) were 3.94-4.25 L·(L·d)-1, 288-302 mL·g-1, 7.80-7.83, and 0.32-0.39 g·L-1, respectively. Additionly, the sludge characteristics of the co-digestion of FW and WAS under a high loading rate were also investigated. The results showed that the primary pathway of methane conversion was through acetic acid during the co-digestion of FW and WAS. Meanwhile, higher methanogenic activity of acetic acid, propionic acid, butyric acid, valeric acid, and coenzyme F420 concentration were also measured.

[Substrate Flow by Different Biochemical Activities in the Urban Sewage Network].

In order to investigate the consumption mechanism of organic contaminants in different biological metabolism pathways within an urban sewage network, a pilot-scale system using two kinds of sediments (urban sewage sediment and artificial sediment) was constructed. The pilot system was operated to study the migration and transformation characteristics of COD, methane, nitrate, and sulfate between sediment and sewage. Results showed that the variation of COD in sewage was 170.58 mg·L-1, with change of COD by deposition and bioreaction of 101.53 mg·L-1 and 69.05 mg·L-1, respectively. Due to biological metabolism, the generation of methane in sewers was of 7.39 mg·L-1; the decrease of nitrate and sulfate in sewage was 0.33 mg·L-1 and 21.35 mg·L-1, respectively. Based on our calculations, the consuming concentration of COD was 32.51 mg·L-1for methane generation, 8.04 mg·L-1 for denitrification, and 6.41 mg·L-1for sulfate degradation by sulfate reducing bacteria. The decrease in COD by deposition was responsible for 65.38% of total variation of COD in sewage. The decrease in COD by bioreaction was responsible for 34.62% of total variation in COD. Meanwhile, total variation values of COD for methane generation, denitrification, and sulfate degradation were responsible for 68.01% of COD variation by bioreaction. Deposition was therefore the main pathway for removal of organic contaminants from the sewer system; biochemical activities of methane generation, denitrification, and sulfate degradation also played important roles.

[Ozonation Characteristics of Low Coagulability Organic Matter from the Secondary Effluent of WWTPs].

The aim of this study was to investigate the effectiveness of ozonation on the removal of organic matter with low coagulability from municipal secondary effluent. The results revealed that the removal efficiency of coagulation generally remained quite low. The residual organic matter belonged to low coagulability organic matter. The presence of the ozone increased the removal efficiency of color and UV254 gradually for low coagulability organic matter, whereas DOC had no noticeable change; the efficiencies were 45%, 34%, and 20%, respectively, at a dosage (denoted as O3/DOC) of 1.5 mg·mg-1. It could be concluded that ozone easily reacted with unsaturated organic matter, and the mineralization of organic matter was less effective. In order to further define the variation in organic matter of the secondary effluent, the differences between the relative molecular weight distribution and fluorescence characteristics of coagulation and ozonation with different zone dosages were monitored in this study. The findings showed that coagulation had little effect on organic content. Nonetheless, ozone might have preferentially reacted with high-molecular-weight substances of organic matter with low coagulability and reduced the fluorescence intensity in the humic-like regions significantly. The shift of fluorescence peak was not changed by ozonation. In addition, via X-ray photoelectron spectroscopy (XPS) analysis, it was identified that coagulation could remove carboxylic organic matter. On the other hand, with the increasing ozone dosage (from 0 to 1.5 mg·mg-1), ozone could preferentially react with low coagulability organic matter with aromatic structure, thus the amount of aliphatics increased gradually.

[Effects of Elevated Tetracycline Concentrations on Aerobic Composting of Human Feces: Composting Behavior and Microbial Community Succession].

In order to investigate the effect of antibiotics on composting behavior, enzymatic activity, and microbial community succession during the aerobic composting of human feces using sawdust as the bulk carrier, tetracycline (TC) was added to the composting system at four different concentrations (0, 100, 250, and 500 mg·kg-1). Microbial community succession was examined by high-throughput 16S rRNA gene sequencing. The results showed that the influence of TC on the physical and chemical properties of compost was related to its concentration. With the increase in TC concentration, the temperature increase during aerobic composting was inhibited, the water-soluble carbon (WSC) residue was increased, the germination index (GI) was decreased, and the dehydrogenase activity (DHA) was also hindered. Parameters, such as temperature, WSC, GI, and DHA, are widely accepted and representative indicators to evaluate compost maturity. Overall, when the concentration of TC was higher than 500 mg·kg-1, the aerobic composting process and the maturity of the final compost were inhibited. Furthermore, elevated TC caused significant changes in microbial community succession and reductions in community diversity and abundance. Therefore, interference in microbial community structures and a hindrance to biological activity are believed to be the main adverse effects of TC on the composting process and maturity of the composting products.

[Removal of Typical Antibiotics During Aerobic Composting of Human Feces].

Aerobic composting experiments were conducted under three different temperatures (55℃, 35℃, and non-temperature-controlled) with human feces and sawdust as the compost material and bulky matrix respectively. Attention was paid to the effects of temperature on the removal of four typical antibiotics (tetracycline, chlortetracycline, sulfadiazine, and ciprofloxacin) during human feces aerobic composting. Furthermore, three specific experiments were conducted to identify the possible antibiotic degradation mechanisms in aqueous solution and during composting with moist sterile sawdust but without feces and composting with feces and moist sterile sawdust. The most effective removal of the four antibiotics was achieved through thermophilic composting (55℃). At 55℃, more than 90% of all the antibiotics were removed. The degradation of tetracycline and chlortetracycline was more temperature-dependent than that of sulfadiazine and ciprofloxacin. Moreover, tetracycline and chlortetracycline removal was primarily through hydrolysis in moist environments. However, sulfadiazine and ciprofloxacin removal was mainly attributed to adsorption by sawdust particles. The contribution of microbial action to antibiotic degradation was insignificant for all the antibiotics except ciprofloxacin. Up to 20% of this antibiotic was degraded by microbial action.

Tea polyphenols dominate the short-term tea (Camellia sinensis) leaf litter decomposition.

Polyphenols are one of the most important secondary metabolites, and affect the decomposition of litter and soil organic matter. This study aims to monitor the mass loss rate of tea leaf litter and nutrient release pattern, and investigate the role of tea polyphenols played in this process. High-performance liquid chromatography (HPLC) and classical litter bag method were used to simulate the decomposition process of tea leaf litter and track the changes occurring in major polyphenols over eight months. The release patterns of nitrogen, potassium, calcium, and magnesium were also determined. The decomposition pattern of tea leaf litter could be described by a two-phase decomposition model, and the polyphenol/N ratio effectively regulated the degradation process. Most of the catechins decreased dramatically within two months; gallic acid (GA), catechin gallate (CG), and gallocatechin (GC) were faintly detected, while others were outside the detection limits by the end of the experiment. These results demonstrated that tea polyphenols transformed quickly and catechins had an effect on the individual conversion rate. The nutrient release pattern was different from other plants which might be due to the existence of tea polyphenols.

[Characteristics and Mechanism of Hybrid Ozonation-Coagulation Process in Wastewater Reclamation].

Because of the limited dissolved organic matter removal efficiency in conventional pre-ozonation-coagulation process, the hybrid ozonation-coagulation (HOC) process was developed for wastewater reclamation in this study. In this process, coagulation and ozonation could synchronize within a single unit. Compared with the pre-ozonation-coagulation process and traditional coagulation process at the same coagulants dosage, the HOC process exhibited higher treatment efficiency, especially better organic matter removal performance at each pH value, which were 37.96% and 39.66%, respectively. In order to obtain the removal mechanism of dissolved organic matters by HOC process,ozone decomposition at two pH values either with or without AlCl3·6H2O was monitored in this study. The results showed that higher pH and the addition of coagulant could accelerate ozone decay. In addition, para-chlorobenzoic acid (p-CBA) was chosen as the hydroxyl radical (·OH) probe compound to indirectly calculate the ·OH exposure. The results revealed that the HOC process was involved in ·OH reaction and coagulant could promote ozone decomposition due to its enhancing effect on ·OH production during the ozonation process. Furthermore, the ozone depletion occurred more quickly at high pH due to its reaction with hydroxide ions (OH-), leading to the formation of ·OH through a series of chain reactions. Moreover, the effects of tert-butanol, a well-known ·OH inhibitor on ozone decay and p-CBA decomposition were also investigated. The results indicated that ozone depletion and p-CBA decomposition were significantly inhibited by tert-butanol, which further proved that ozone was decomposed into ·OH radicals through chain reactions. In the HOC process, Al-based coagulants and hydrolyzed products could act as catalysts to enhance ozone decomposition into ·OH which is a powerful oxidant to improve the organics removal efficiency.

[Disinfection Action of Ultraviolet Radiation and Chlorination on Escherichia coli and Poliovirus].

We chose Escherichia coli (E. coli) and poliovirus as a typical pathogenic bacterium and virus, respectively. The effects of two typical disinfectants (chlorine and ultraviolet) on each of them were investigated based on microbial culture and quantitative PCR methods. The results showed that Poliovirus was appreciably more resistant to chlorine (required disinfection dose for 1-log microbial reduction:10.14 mg·L-1·min for E. coli; 19.2 mg·L-1·min for poliovirus) and ultraviolet (UV) light (required UV dose for 1-log microbial reduction:1.81 mJ·cm-2 for E. coli; 6.37 mJ·cm-2 for poliovirus) than E. coli for the microbial culture. For PCR, this study revealed that 1-log gene reduction required UV doses and ct values of at least one to two orders of magnitude higher than that for the microbial culture. The damage of RNA in Poliovirus was more seriously than that of DNA in E. coli. Single-stranded RNA was more sensitive to UV irradiation than DNA. The result evaluated with the quantitative PCR method showed opposite result to that of the traditional culture method in which the Poliovirus was more tolerant. The required UV doses for 1-log nucleic acid reduction were 135 mJ·cm-2 and 270.3 mJ·cm-2 for E. coli and poliovirus, respectively. Nucleic acid damage required a higher dose of disinfectants than microbial inactivation, which was probably attributed to the phenomenon of viable but non-culturable (VBNC) cells, other molecular targets of inactivation and the persistence of nucleic acid after cell death.

[Removal of Estrogenic Effect by Typical Domestic Wastewater Treatment Processes].

Targeting at the characteristics of low concentration but high risk of endocrine disrupting compounds in the aquatic environment, the current study investigated the distribution of estrogenicity and E2 level using recombinant yeast estrogen screen (YES) and enzyme linked immunosorbent assay (ELSIA) during domestic wastewater treatment processes. The results showed that the levels of estrogenicity and E2 in influents of wastewater treatment plants were 4.35-7.58 ng·L-1 and 36.95-83.43 ng·L-1, respectively. It was found that biological treatment processes played a crucial role in the removal of estrogenicity and E2, such as oxidation ditch, A2/O and A2/O followed by MBR, where the removal of estrogenicity and E2 was 71.10%-75.54% and 75.88%-80.72%, respectively. The activated sludge, with an estrogencity level of 1.84-2.43 ng·g-1 and an E2 level of 8.45-12.84 ng·g-1, had the function of eliminating estrogenic effect to a certain extent by adsorption. The estrogenic activity in the effluent of domestic wastewater was 1.06-2.19 ng·L-1, which will pose potential risk to the aquatic life in the environment. Last but not least, ELISA had a good correlation with YES assay, which provides a new method for rapid screening and assessment of water environmental estrogen.

[Biological Toxicity Evaluation of Domestic Wastewater Based on A2/O Treatment Processes Using a Battery of Bioassays].

In order to accurately evaluate the comprehensive ecotoxicity of domestic wastewater and the toxicity reduction efficiency of different treatment processes, standardized assays focusing on Vibrio fischeri, SOS/umu test and yeast estrogen screen were applied. Simultaneously, male zebrafish was used to address the mode of action of endocrine disrupting effects of wastewater and reclaim water on aquatic life. Results of this study indicated that the influent was severely polluted:highly acute toxicity, genotoxicity and estrogenicity were observed. After the secondary biological treatment, the above toxicities were significantly reduced, making the water quality improved. However, the estrogencity of secondary effluent was detected at 1.89 ng·L-1, which still posed potential risk on the aquatic life in receiving water. In addition, the up-regulation of estrogen receptor (esr 1) and vitellogenin (vtg 1) in the livers of zebrafish was observed after exposure to 2.5 times concentrated wastewaters, which demonstrated that wastewater modulates hormonal activities of aquatic life by disturbing target genes expression. Moreover, the slight down-regulation of esr 1 was observed in the gonads. These observations reflect that the evaluation of biological toxic effect should be analyzed in different tissues or organs, so that more comprehensive information about the adverse effects of wastewaters on aquatic life can be obtained.

Occurrence of tetracycline-resistant fecal coliforms and their resistance genes in an urban river impacted by municipal wastewater treatment plant discharges.

Antibiotic resistance of fecal coliforms in an urban river poses great threats to both human health and the environment. To investigate the occurrence and distribution of antibiotic resistant bacteria in an urban river, water samples were collected from the Chanhe River in Xi'an, China. After membrane filtration of water samples, the tetracycline resistance rate of fecal coliforms and their resistance genes were detected by plating and polymerase chain reaction (PCR), respectively. We found that fecal coliforms were generally resistant to tetracycline and saw average resistance rates of 44.7%. The genes tetA and tetB were widely detected, and their positive rate was 60%-100% and 40%-90%, respectively. We found few strains containing tetC, tetK, tetQ and tetX, and we did not identify any strains containing tetG, tetM or tetO. The prevalence of tetA and tetB over other genes indicated that the main mechanism for resistance to tetracycline is by changes to the efflux pump. Our analysis of the types and proportion of tetracycline resistance genes in the Chanhe River at locations upstream and downstream of the urban center suggests that the increased number of tetracycline-resistant fecal coliforms and spatial variation of tetracycline resistance genes diversity were related to municipal wastewater treatment plant discharge.

[Variation of different carbon sources in the sewage treatment process].

The biodegradability and speciation of organics were studied through long-term analysis of A2/O treatment. The majority of the organic matters were particle organics which accounted for 61% of the total organics. The proportions of rapidly degradable, slowly degradable and refractory organics were 15. 8% , 54. 2% and 30% respectively. Rapidly biodegradable organics were mainly dissolved organics while slowly biodegradable organics were particle organics. The variation of these two kinds of carbon sources was analyzed during the treatment process. It was noted that microbial hydrolysis fermentation took place in the anaerobic and anoxic tanks, which led to the transformation of slowly biodegradable organics and the anaerobic tank had the highest transformation rate. The transformation and utilization of rapidly/slowly biodegradable organics were analyzed through calculation. The results showed that the transformation efficiency of slowly biodegradable organics in the anaerobic and anoxic tanks in two hours was 33% and 20%, respectively. Furthermore, the amount and species of aliphatic acid increased in the anaerobic and anoxic tanks comparing with raw water.

[Heavy metals pollution and analysis of seasonal variation runoff in Xi'an].

In order to explore heavy metals pollution situation,changes in characteristics, the correlation between each heavy mental and pollution source analysis of Xi'an various regions in different season in one year. This study collected several samples of Xi'an rainfall typical urban trunk roads throughout the year in 2013 and used inductively coupled plasma mass spectrometry (ICP-MS) to determine the level of Fe, Mn, Pb, Zn, Al, Cd of the samples, then, analyzed the seasonal change of heavy mental. Studies have shown that: the heavy metal of Xi'an road runoff pollutes seriously, the concentration of Fe over three times of the national standard and maintain the higher levels throughout the year, meanwhile the concentration with the intensity of human activities increases. The concentration of Mn and Zn in one year show a trends: winter > autumn > summer> spring. Pb concentration increases with the increase in traffic volume, while showing: winter > spring > summer > autumn. Factor analysis shows: Fe and Al was affected by the same sources-natural sources; Zn, Cd affected by anthropogenic sources of large; Mn, Pb affected by the larger traffic sources.

[Preliminary study on characteristics of volumetric oxygen transfer coefficient in granular sludge systems].

The volumetric oxygen transfer coefficient (k(L)a) was tested with mature aerobic granules in the same aeration measurement device and under the same aeration conditions. The k(L)a (min(-1)) was 0.586 1 +/- 0.009 5, 0.586 1 +/- 0.0272, 0.555 6 +/- 0.016 8, 0.5338 +/- 0.0268 for floc sludge, and 0.645 5 +/- 0.027 6, 0.632 0 +/- 0.0755, 0.618 5 +/- 0.062 5, 0.640 6 +/- 0.055 5 for aerobic granules, when the sludge concentration MLSS (mg x L(-1)) was controlled at 2 000, 4 000, 6 000, 8 000, respectively. This indicated that granular sludge exhibited higher k(L)a values than the flocs, and the k(L)a value of floc sludge decreased with the increase of the sludge concentration; however, insignificant decease was found for granular sludge. After screening of granules with different diameter, the k(L)a values of the aerobic granular sludge with different sizes which had the same MLSS, volume, surface area and particle number were compared, and insignificant difference was found, suggesting that the effects of these factors on the k(L)a of granular sludge were negligible. The findings of this work may have significance for the energy-saving operation of wastewater treatment plants.

[Evaluation of floc strength based on morphological analysis and optical online monitoring].

Based on morphological analysis and PDA online monitoring, a method was established for the evaluation of floc strength. In order to calculate the binding force of flocs formed under a given flocculation condition, a jar test was conducted. The morphological characteristics of flocs were studied by image analysis and the particle image velocimetry technology. A shear force was exerted on the flocs by introducing the flocculated suspension through a transparent tube where the velocity gradient value of the flow could be accurately controlled. As the tube was connected with a particle dispersion analyzer (PDA), the condition of floc breakage was monitored online and the critical condition was identified by analyzing the PDA outputs (FI curves). According to the equivalent relationship among shear force, breaking force and binding force under the critical breaking condition, the binding force coefficient k1 could thus be determined, and the binding force B which represented the floc strength was evaluated. The validity of this method was proved by a series of experiments using aluminium sulphate as the coagulant for the flocculation of humic acid.