Selective adsorption of tetracycline by β-CD-immobilized sodium alginate aerogel coupled with ultrafiltration for reclaimed water

In this work,a novel composite material based on β-cyclodextrin-immobilized sodium alginate aerogel(β-CD/NaAlg) was developed utilizing cross-linker of epichlorohydrin and applied as an adsorbent to remove tetracycline antibiotics from reclaimed wastewater.A series of characterizations were utilized to confirm the successful synthesis of the adsorbent and this β-CD/NaAlg presented a three-dimensional network at the nanoscale or microscale.Under optimal conditions(pH=4,t=8 h,β-CD:NaAlg=9,adsorbent dosage = 1.5 g·L-1),the maximum removal rate of β-CD/NaAlg to tetracycline was 70%.The adsorption behavior of tetracycline on β-CD/NaAlg conformed to the Freundlich isotherm model(R2=0.9977) and the pseudo-second-order kinetic model(R^(2)=0.9993).Moreover,the adsorbent still removed 55.3% of tetracycline after five cycles.Specially,the adsorbent was integrated with ultrafiltration to adsorb tetracycline antibiotics from simulated reclaimed wastewater,and the removal rate of tetracycline reached 78.9% within 2 h.The existence of Cr(Ⅵ) had a negligible impact on tetracycline removal,while the presence of humic acid exhibited a promoting effect.The possible adsorption mechanisms were also elucidated through X-ray photoelectron spectroscopy and density functional theory analysis.In summary,β-CD/NaAlg represents an environmentally friendly,efficient,and sustainable adsorbent for removing tetracycline antibiotics from reclaimed water.

Effects of reclaimed water irrigation and nitrogen fertilization on the chemical properties and microbial community of soil

The ecological effect of reclaimed water irrigation and fertilizer application on the soil environment is receiving more attention.Soil microbial activity and nitrogen（N）levels are important indicators of the effect of reclaimed water irrigation on environment.This study evaluated soil physicochemical properties and microbial community structure in soils irrigated with reclaimed water and receiving varied amounts of N fertilizer.The results indicated that the reclaimed water irrigation increased soil electrical conductivity（EC）and soil water content（SWC）.The N treatment has highly significant effect on the ACE,Chao,Shannon（H）and Coverage indices.Based on a 16S ribosomal RNA（16S rRNA）sequence analysis,the Proteobacteria,Gemmatimonadetes and Bacteroidetes were more abundant in soil irrigated with reclaimed water than in soil irrigated with clean water.Stronger clustering of microbial communities using either clean or reclaimed water for irrigation indicated that the type of irrigation water may have a greater influence on the structure of soil microbial community than N fertilizer treatment.Based on a canonical correspondence analysis（CCA）between the species of soil microbes and the chemical properties of the soil,which indicated that nitrate N（NO3-–-N）and total phosphorus（TP）had significant impact on abundance of Verrucomicrobia and Gemmatimonadetes,meanwhile the p H and organic matter（OM）had impact on abundance of Firmicutes and Actinobacteria significantly.It was beneficial to the improvement of soil bacterial activity and fertility under 120 mg kg^-1 N with reclaimed water irrigation.

Enhanced Nutrient Removal with Upflow Biological Aerated Filter for Reclaimed Water

A two-stage upflow biological aerated filter was designed as an advanced treatment process to optimize the operating parameters and study the correlative factors influencing the efficiency of nitrification, denitrification and phosphorus removal. The experimental results showed that the final effluent of the two-stage upflow biofilter process operated in series could meet the stringent limits of the reclaimed water for the total nitrogen of 2 mg/L, and total phosphorus of 0.3 mg/L. The high treatment efficiency allowed the reactor operating at very high hydraulic loadings and reaching nearly complete nitrification and denitrifieation.

Nitrogen Removal Efficiency of the Reclaimed Water by Land Treatment System

[Objective] The research aimed to study nitrogen removal effect of the land treatment process on reclaimed water. [Method] By using land treatment system, reclaimed water which reached one-level A standard was conducted advanced processing, and nitrogen removal efficiency of the effluent was inspected. [ Result] There was a positive correlation between organic matter content of the soil medium and nitrogen removal effect. With appropriate soil medium, TN and NH3-N could obtain the removal efficiency of more than 90% and 75% respectively, and they could be removed at 30 and 10 cm height of soil medium respectively with land treatment system to treat reclaimed water. [ Conclusion ] The research provid- ed theoretical basis for application of the land treatment system into nitrogen removal of the reclaimed water.

The risk factors and threshold level of subchronic inhalation exposure of reclaimed water

Inhalation of reclaimed water is known to cause lung infammation,and free endotoxins have been shown to be a major risk factor for acute exposure.Subchronic exposure has also been shown to induce infammatory responses with visible tissue damage.However,subchronic risk factors have yet to be identified,and a threshold for the protection of occupational populations during urban reuse is necessary.In this study,potential risk factors in reclaimed water were examined by subchronic exposure with fractionated reclaimed water,and the health risk threshold was tested with a series of diluted reclaimed water.Accordingly,following a 12-week exposure,macromolecules and microorganisms were found to be two major risk factors in reclaimed water that could cause pulmonary infammation,including increased proportion of polymorphonuclear leukocytes in bronchoalveolar fuid,formation of inducible bronchus-associated lymphoid tissue,and elevation of Immunoglobulin A levels.Moreover,infammation persisted after a 4-week recovery period.The calculated threshold of reclaimed water exposure for mice was 31.8 Endotoxin Unit(EU)/(kg·day)under when exposed to 50%additional relative humidity from reclaimed water at 25℃ for 2 hr/day.Meanwhile,the subchronic threshold estimate for humans under the same exposure conditions was found to be 12.2 EU/(kg·day),corresponding to endotoxin levels of 61.7 EU/mL in reclaimed water.The threshold level of endotoxin was lower than that in most non-potable reclaimed water.The findings of this study suggest that occupational exposure of reclaimed water can serve as a potential risk to workers.

Inactivation, reactivation and regrowth of indigenous bacteria in reclaimed water after chlorine disinfection of a municipal wastewater treatment plant

Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/（mg·min） and R 2 of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose （0-22 （mg·min）/L）, and a trailing region with chlorine dose increasing from 22 to 69 （mg·min）/L. Reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 （mg·min）/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 （mg·min）/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse.

A biological safety evaluation on reclaimed water reused as scenic water using a bioassay battery

An assessment method based on three toxicity tests （algae growth inhibition, daphnia immobilization and larval fish toxicity） was used to screen the biological safety of reclaimed water which was reused as sole replenishment for scenic water system in a park （SOF Park） in northern China. A total of 24 water samples were collected from six sites of water system in the SOF Park in four different seasons. The results indicated that： （1） the reclaimed water directly discharged from a reclamation treatment plant near the SOF Park as influent of park had relatively low biological safety （all samples were ranked as C or D）; （2） the biological safety of reclaimed water was improved greatly with the ecological reclamation treatment processes composing of artificial wetland system and followed oxidation pond system; （3） the biological safety of reclaimed water in the main lake of SOF Park kept at a health status during different seasons （all samples were ranked as A）; （4） there was some certain correlation （R2= 0.5737） between the sum of toxicity scores and dissolved organic carbon for the studied water samples. It was concluded that the assessment method was reliable to screen the safety of reclaimed water reused as scenic water, and the reclaimed water with further ecological purification processes such as artificial wetland and oxidation pond system can be safely reused as scenic water in park.

Identification of key factors governing chemistry in groundwater near the water course recharged by reclaimed water at Miyun County, Northern China

Reclaimed water was successfully used to recover the dry Chaobai River in Northern China, but groundwater may be polluted. To ensure groundwater protection, it is therefore critical to identify the governing factors of groundwater chemistry. Samples of reclaimed water, river and groundwater were collected monthly at Chaobai River from January to September in 2010. Fifteen water parameters were analyzed. Two kinds of reclaimed water were different in type （Na-Ca-Mg-Cl-HCO3 or Na-Ca-Cl-HCO3 ） and concentration of nitrogen. The ionic concentration and type in river were similar to reclaimed water. Some shallow wells near the river bed had the same type （Na-Ca-Mg-Cl-HCO3 ） and high concentration as reclaimed water, but others were consistent with the deep wells （Ca-Mg-HCO3 ）. Using cluster analysis, the 9 months were divided into two periods （dry and wet seasons）, and all samples were grouped into several spatial clusters, indicating different controlling mechanisms. Principal component analysis and conventional ionic plots showed that calcium, magnesium and bicarbonate were controlled by water-rock interaction in all deep and some shallow wells. This included the dissolution of calcite and carbonate weathering. Sodium, potassium, chloride and sulfate in river and some shallow wells recharged by river were governed by evaporation crystallization and mixing of reclaimed water. But groundwater chemistry was not controlled by precipitation. During the infiltration of reclaimed water, cation exchange took place between （sodium, potassium） and （calcium, magnesium）. Nitrification and denitrification both happened in most shallow groundwater, but only denitrification in deep groundwater.

Effectiveness of vegetation on phosphorus removal from reclaimed water by a subsurface flow wetland in a coastal area

This work was conducted to evaluate the effectiveness and influence factors of vegetation on phosphorus （P） removal from reclaimed water in constructed wetlands. Comparisons were conducted between one pilot scale subsurface flow wetland （P-SSFW） and two demonstration subsurface flow wetlands, which were series-wound and named as first subsurface flow wetland （F-SSFW）, and second subsurface flow wetland （S-SSFW）, respectively. The three wetlands had the same vegetation and substrate, but different pH values, total dissolved solids （TDS） and P loads. Results showed that the P content in the vegetation shoots of the F-SSFW was 2.16 rag/g, while 2.31 mg/g in the S-SSFW and 2.69 mg/g in the P-SSFW. These differences were likely caused by the higher pH and TDS in the reclaimed water. The P content also differed among the tissues of the plant, which were 5.94-6.44 mg/g, 2.20-2.77 mg/g, 1.31-1.46 mg/g and 1.53-1.88 mg/g in the flowers, leaves, stems, and roots, respectively. The greatest discrepancy was observed in the leaves, indicating that the environment of the wetlands had the greatest influence on the leaves. When the total phosphorus （TP） load was lower, the proportion of P removed by vegetation assimilation was 16.17% in the P-SSFW, 12.90% in the F-SSFW and 13.29% in the S-SSFW. However, the relative removal efficiency by vegetation among the three wetlands did not vary greatly from that observed in other studies. Moreover, the influence of pH, TDS and TP load was not as great as the influence of the vegetation species, type of substrate, influent style or climate.

Improvement of the assimilable organic carbon （AOC） analytical method for reclaimed water

Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P 17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. Z J2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density （104 CFU.mL-1） and higher incubation temperature （25℃） could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.

Formation and control of disinfection byproducts and toxicity during reclaimed water chlorination： A review

Chlorination is essential to the safety of reclaimed water; however, this process leads to concern regarding the formation of disinfection byproducts（DBPs） and toxicity. This study reviewed the formation and control strategies for DBPs and toxicity in reclaimed water during chlorination.Both regulated and emerging DBPs have been frequently detected in reclaimed water during chlorination at a higher level than those in drinking water, indicating they pose a greater risk to humans. Luminescent bacteria and Daphnia magna acute toxicity, anti-estrogenic activity and cytotoxicity generally increased after chlorination because of the formation of DBPs. Genotoxicity by umu-test and estrogenic activity were decreased after chlorination because of destruction of toxic chemicals. During chlorination, water quality significantly impacted changes in toxicity.Ammonium tended to attenuate toxicity changes by reacting with chlorine to form chloramine,while bromide tended to aggravate toxicity changes by forming hypobromous acid. During pretreatment by ozonation and coagulation, disinfection byproduct formation potential（DBPFP）and toxicity formation potential（TFP） occasionally increase, which is accompanied by DOC removal; thus, the decrease of DOC was limited to indicate the decrease of DBPFP and TFP. It is more important to eliminate the key fraction of precursors such as hydrophobic acid and hydrophilic neutrals. During chlorination, toxicities can increase with the increasing chlorine dose and contact time. To control the excessive toxicity formation, a relatively low chlorine dose and short contact time were required. Quenching chlorine residual with reductive reagents also effectively abated the formation of toxic compounds.

Characteristics of change in water quality along reclaimed water intake area of the Chaobai River in Beijing, China

To reveal the basic characteristics and controlling factors of water quality change in the project Wenyu to Chaobai reclaimed water diversion, the water quality in the study area was monitored for one year at seven monitoring sites. Inverse geochemical models of the statistical groups were developed using PHREEQC to elucidate the hydrochemistry characteristics of reclaimed water and the factors. The monitoring results indicated that nitrogen and phosphorus contents were significantly reduced along the river mainly caused by seasonal and location variation. The pH ranged from 7.44 to 9.81. Photosynthesis of algae and denitrification in anaerobic microenvironment ultimately led to a sudden pH increase after the Jian River and the Chaobai River confluence. Mg2＋ and SO^- levels dropped obviously in the summer and increased in winter seasons after intersection. Na＋ and C1- are relatively stable, and marked drop in the concentration only after the two rivers meet. And there is a decrease of Ca2＋ and HCO~ and increase in CO^- during monitoring period. As a whole, the primary ions and nutrient components, including nitrogen and phosphorus, had high levels in winter. Algae＇s photosynthesis and respiration were observed to have an impact on the river water quality; there was precipitation-dissolution of minerals and denitrification from upstream to downstream. Inverse geochemical PHREEQC modeling confirmed that there was precipitation of aragonite or calcite, and gypsum or anhydrite in summer, and dissolution in winter; as well as precipitation of dolomite in winter, and cationic exchange and denitrification along the river.

A synthetical methodology for identifying pr ior ity pollutants in reclaimed water based on meta-analysis

Wastewater reclamation and reuse is an increasing global project,while the reclamation treatment on wastewater does not completely remove all pollutants in water.The residual pollutants in reclaimed water would cause potential risk on human health and ecosystem safety during the long-term use.It is impossible to analyze and control all pollutants one by one in practice,therefore,identification and control of priority pollutants will be efficient strategy to ensure the safe use of reclaimed water.An integrated three-step methodology for identifying priority pollutants in reclaimed water was proposed in this study.First,a comprehensive literature survey on the occurrence of pollutants in reclaimed water was conducted,and a dataset D PR for pollutants occurrence in reclaimed water was established,containing 1,113 pollutants.Second,611 chemicals that had been recommended as hazardous pollutants for various water bodies in previous literatures were summarized,and a dataset D HP for hazardous pollutants in water was obtained.Third,meta-analysis on these two datasets(D PR and D HP)was performed,a new dataset D HPR for hazardous pollutants in reclaimed water was established,including 265 candidates.Finally,59 substances out of dataset D HPR were identified as priority pollutants for reclaimed water based on their recommendation frequency.It is expected that this synthetical methodology will provide powerful support for scientific evaluating and managing water pollution and ensuring safe use of reclaimed water.

A toxicity-based method for evaluating safety of reclaimed water for environmental reuses

A large quantity of toxic chemical pollutants possibly remains in reclaimed water due to the limited removal efficiency in traditional reclamation processes. It is not enough to guarantee the safety of reclaimed water using conventional water quality criteria. An integrated assessment method based on toxicity test is necessary to vividly depict the safety of reclaimed water for reuse. A toxicity test battery consisting of lethality, genotoxicity and endocrine disrupting effect was designed to screen the multiple biological effects of residual toxic chemicals in reclaimed water. The toxicity results of reclaimed water were converted into the equivalent concentrations of the corresponding positive reference substances（EQC）. Simultaneously, the predicted no-effect concentration（PNEC） of each positive reference substance was obtained by analyzing the species sensitivity distribution（SSD） of toxicity data. An index ＂toxicity score＂ was proposed and valued as 1, 2, 3, or 4 depending on the ratio of the corresponding EQC to PNEC. For vividly ranking the safety of reclaimed water, an integrated assessment index ＂toxicity rank＂ was proposed, which was classified into A, B, C, or D rank with A being the safest. The proposed method was proved to be effective in evaluating reclaimed water samples in case studies.

Molecular characterization of effluent organic matter in secondary effluent and reclaimed water:Comparison to natural organic matter in source water

Municipal wastewater reclamation is becoming of increasing importance in the world to solve the problem of water scarcity. A better understanding of the molecular composition of effluent organic matter（Ef OM） in the treated effluents of municipal wastewater treatment plants（WWTPs） is crucial for ensuring the safety of water reuse. In this study, the molecular composition of Ef OM in the secondary effluent of a WWTP in Beijing and the reclaimed water further treated with a coagulation–sedimentation–ozonation process were characterized using a non-target Fourier transform ion cyclotron resonance mass spectrometry（FT-ICR MS） method and compared to that of natural organic matter（NOM） in the local source water from a reservoir. It was found that the molecular composition of Ef OM in the secondary effluent and reclaimed water was dominated by CHOS formulas, while NOM in the source water was dominated by CHO formulas. The CHO formulas of the three samples had similar origins. Anthropogenic surfactants were responsible for the CHOS formulas in Ef OM of the secondary effluent and were not well removed by the coagulation-sedimentation-ozonation treatment process adopted.

Hydroxyl carboxylate based non-phosphorus corrosion inhibition process for reclaimed water pipeline and downstream recirculating cooling water system

A combined process was developed to inhibit the corrosion both in the pipeline of reclaimed water supplies（PRWS） and in downstream recirculating cooling water systems（RCWS）using the reclaimed water as makeup. Hydroxyl carboxylate-based corrosion inhibitors（e.g.,gluconate, citrate, tartrate） and zinc sulfate heptahydrate, which provided Zn^2＋ as a synergistic corrosion inhibition additive, were added prior to the PRWS when the phosphate（which could be utilized as a corrosion inhibitor） content in the reclaimed water was below 1.7 mg/L, and no additional corrosion inhibitors were required for the downstream RCWS.Satisfactory corrosion inhibition was achieved even if the RCWS was operated under the condition of high numbers of concentration cycles. The corrosion inhibition requirement was also met by the appropriate combination of PO4^3- and Zn^2＋ when the phosphate content in the reclaimed water was more than 1.7 mg/L. The process integrated not only water reclamation and reuse, and the operation of a highly concentrated RCWS, but also the comprehensive utilization of phosphate in reclaimed water and the application of non-phosphorus corrosion inhibitors. The proposed process reduced the operating cost of the PRWS and the RCWS, and lowered the environmental hazard caused by the excessive discharge of phosphate. Furthermore, larger amounts of water resources could be conserved as a result.

Aerosol exposure assessment during reclaimed water utilization in China and risk evaluation in case of Legionella

Reclaimed water utilization provides an effective way to alleviate water shortage.However,the residual pathogens in the recycled water like Legionella,could be spread into the air as aerosols through water-to-air transmission process.Inhaling the aerosols by the people nearby increases their susceptibility to diseases.For estimating the health risks associated with the potential exposure of airborne Legionella emitted from the urban use of reclaimed water in China,nationwide questionnaire was designed to investigate the exposure habits of Chinese population in different scenarios.Quantitative microbial risk assessment(QMRA)served as the suitable explanatory tool to estimate the risk.The results indicated that annual infection probability of populations exposed to Legionella for three scenarios,0.0764(95%CI:0.0032−0.6880)for road cleaning,1.0000(95%CI:0.1883−1.0000)for greenfield irrigation,0.9981(95%CI:0.0784−1.0000)for landscape fountain,were markedly higher than the threshold recommended by WHO(10^(−4) per person per year(pppy))according to the concentration distribution of Legionella in the reclaimed water.An age-,educational background-,region-and gender-specific data in annual infection probability also showed different tendencies for some subpopulations.This study provides some detailed information on the health risks from the water reuse in China and will be useful to promote the safe application of reclaimed water in water-deficient areas.

Modelling the thresholds of nitrogen/phosphorus concentration and hydraulic retention time for bloom control in reclaimed water landscape

The risks posed by algal blooms caused by nitrogen and phosphorus in reclaimed water used in urban water landscapes need to be carefully controlled.In this study,the combined effects of the nitrogen and phosphorus concentrations and the light intensity and temperature on the specific growth rates of algae were determined using Monod,Steele,and Arrhenius models,then an integrated algal growth model was developed.The algae biomass,nitrogen concentration,and phosphorus concentration mass balance equations were used to establish a new control model describing the nitrogen and phosphorus concentration and hydraulic retention time thresholds for algal blooms.The model parameters were determined by fitting the models to data acquired experimentally.Finally,the control model and numerical simulations for six typical algae and mixed algae under standard conditions were used to determine nitrogen/phosphorus concentration and hydraulic retention time thresholds for landscape water to which reclaimed water is supplied(i.e.,for a reclaimed water landscape).

Hydraulic model for multi-sources reclaimed water pipe network based on EPANET and its applications in Beijing, China

Water shortage is one of the major water related problems for many cities in the world.The planning for utilization of reclaimed water has been or would be drafted in these cities.For using the reclaimed water soundly,Beijing planned to build a large scale reclaimed water pipe networks with multi-sources.In order to support the plan,the integrated hydraulic model of planning pipe network was developed based on EPANET supported by geographic information system(GIS).The complicated pipe network was divided into four weak conjunction subzones according to the distribution of reclaimed water plants and the elevation.It could provide a better solution for the problem of overhigh pressure in several regions of the network.Through the scenarios analy-sis in different subzones,some of the initial diameter of pipes in the network was adjusted.At last the pipe network planning scheme of reclaimed water was proposed.The proposed planning scheme could reach the balances between reclaimed water requirements and reclaimed water supplies,and provided a scientific basis for the reclaimed water utilization in Beijing.Now the scheme had been adopted by Beijing municipal government.

Factors influencing water quality indices in a typical urban river originated with reclaimed water

The water quality in a typical urban river segment originated with reclaimed water in Beijing was monitored for two years to investigate the evolution of water quality along the rivcr, and statistical analysis was applied to determine factors influencing water quality of such river recharged by reclaimed water. It was found that no significant change in pollutant concentrations （including COD, NH4＋-N, TN and TP） was observed during this time, and their average values were close to those of the original reclaimed water. However, turbidity and algal contents fluctuated temporally in the direction of river flow. Statistical analysis showed that turbidity was strongly positively correlated with algal contents for flow rate 〈 0.1 m.s-1. whereas it was strongly positively correlated with both algalcontents and TOC for flow rate 〉 0. 1m. s-1. It was observed that diatom was the absolute predominant phyla with Melosira as the major species. In terms of algal bloom control, the specific growth rate of algae was strongly correlated to temperature, and was influenced by flow rate as well. Compared with two other rivers originated with reclaimed water and one originated with natural water, the Shannon Wiener index in the objective river was the lowest, with values between 0.7 and 1.6, indicating a high risk for algal bloom. Statistics showed that Shannon Wiener index was strongly negatively correlated to nutrient salts and cations.