Treatment Effects of A-F/PDM Composite Coagulants to Taihu Lake Prechlorinated Algae-Containing Water in Winter

2012 ◽  
Vol 610-613 ◽  
pp. 1569-1572
Author(s):  
Xiao Lei Zhao ◽  
Yue Jun Zhang ◽  
Xiao Xiao Li ◽  
Cheng Liu
Keyword(s):  
Intrinsic Viscosity ◽  
Ferric Chloride ◽  
Treatment Effect ◽  
Treatment Effects ◽  
Aluminum Sulfate ◽  
Taihu Lake ◽  
Removal Rates ◽  
Turbidity Removal ◽  
Algae Removal ◽  
Removal Efficiencies

The series of stable A-F/PDM composite coagulants prepared by combining polydiallyldimethylammonium chloride (PDM) with the composite (A-F) of aluminum sulfate (AS) and ferric chloride (FeCl3) were used to research the treatment effects to Taihu Lake prechlorinated algae-containing water in winter. The composite coagulants were tested by jar tests for the effects of mass percents (5%~20%) and intrinsic viscosity values (0.55~3.99dL/g) of PDM on algae- and turbidity-removal efficiencies. The results show that when the residual turbidity of supernatant after sedimentation reaches the control standard of 2 NTU, the dosages of A-F and A-F/PDM (0.55/5%~3.99/20%) are 4.52 mg/L and 4.27~2.52 mg/L respectively, and the algae-removal rates are 90.1% and 92.0%~96.3% respectively. When the dosages are 4.52 mg/L, the algae-removal rates are 90.1% and 92.5%~99.0% respectively, and the residual turbidities are 2.00 NTU and 1.76~0.60 NTU respectively. Therefore, using A-F/PDM composite coagulants can enhance evidently the treatment effect of A-F to Taihu Lake prechlorinated algae-containing water in winter.

Algae-Removal Treatment of A-F/PDM Composite Coagulants to Summer Taihu Lake Algae-Rich Water under Prechlorination Process

2012 ◽  
Vol 621 ◽  
pp. 283-286
Author(s):  
Xiao Lei Zhao ◽  
Yue Jun Zhang ◽  
Xiao Xiao Li ◽  
Cheng Liu
Keyword(s):  
Intrinsic Viscosity ◽  
Removal Efficiency ◽  
Ferric Chloride ◽  
Aluminum Sulfate ◽  
Taihu Lake ◽  
Effluent Water ◽  
Removal Rates ◽  
Polydiallyldimethylammonium Chloride ◽  
Algae Removal ◽  
Removal Efficiencies

The series of stable A-F/PDM composite coagulants prepared by combining polydiallyldimethylammonium chloride (PDM) with the composite (A-F) of aluminum sulfate (AS) and ferric chloride (FeCl3) were used to research the algae-removal efficiencies to summer Taihu Lake algae-rich water under prechlorination process. The composite coagulants were tested by jar tests for the effects of mass percents (5%~20%) and intrinsic viscosity values (0.55~3.99 dL/g) of PDM on algae-removal efficiencies. For water with algae content of 6.14×104 cells/mL, the algae-removal rates of 90.9% and 94.0%~ 96.3% could be realized by using A-F and A-F/PDM(0.55/5%~3.99/20%) with dosages of 5.60 mg/L and 4.81~3.01 mg/L, respectively, when 2 NTU residual turbidity of effluent water after sedimentation was required. Therefore, using A-F/PDM composite coagulants could enhance evidently the algae-removal efficiency of A-F to summer Taihu Lake algae-rich water. Compared with using A-F solely, the dosages of A-F in composite coagulants were saved when the residual turbidities were required in same level.

Performance of PAC/PDM composite coagulants for removal of algae from Lake Taihu waters in summer

2010 ◽  
Vol 62 (2) ◽  
pp. 330-339 ◽  
Author(s):  
Y. J. Zhang ◽  
X. L. Zhao ◽  
X. X. Li ◽  
Ch. Liu ◽  
L. L. Zhu
Keyword(s):  
Water Quality ◽  
Intrinsic Viscosity ◽  
Removal Rate ◽  
Lake Taihu ◽  
Raw Water ◽  
Removal Rates ◽  
Polyaluminum Chloride ◽  
Enhanced Coagulation ◽  
Algae Removal ◽  
Better Than

The enhanced coagulation of algae-rich raw water from Lake Taihu in summer was studied by use of composite coagulants. The composite coagulants were composed of polyaluminum chloride (PAC) and polydimethyldiallylammonium chloride (PDM) with various intrinsic viscosity values (0.55–3.99 dL/g) and different mass percentages (5–20%) in the formulation. For raw water with temperature of 28–29°C and algae content of 3.60 × 104–3.70 × 104 cells/ml, the algae-removal rates of 89.0% and 89.3–93.1% could be realized by using PAC and PAC/PDM (0.55/5%–3.99/20%) with dosages of 8.37 mg/L and 5.93–3.58 mg/L, respectively, when 2 NTU residual turbidity of treated water after sedimentation was required. Compared with using PAC only, the removal rate of CODMn using PAC/PDM increased at least 4.4% when the dosage was 8 mg/L, and increased at least 5.0% when the dosage was 10 mg/L. The composite coagulants could still function well when raw water quality deteriorated and algae content reached 8.00 × 104 cells/ml. The enhanced coagulation efficiency of PAC/PDM (0.55/5%) could be better than that of PAC combined with prechlorination process when the same dosages are used.

scholarly journals Comparison of Water Turbidity Removal Efficiencies of Descurainia Sophia Seed Extract and Ferric Chloride

2016 ◽  
Vol 1 (2) ◽  
pp. 118-124 ◽  
Author(s):  
Tooran Yarahmadi ◽  
Mazyar Peyda ◽  
Mehran Mohammadian Fazli ◽  
Rizan Rezaeian ◽  
Negin Soleimani ◽  
...  
Keyword(s):  
Ferric Chloride ◽  
Seed Extract ◽  
Water Turbidity ◽  
Turbidity Removal ◽  
Descurainia Sophia ◽  
Removal Efficiencies

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

1998 ◽  
Vol 38 (7) ◽  
pp. 19-24 ◽  
Author(s):  
C.-J. Lu ◽  
C. M. Lee ◽  
M.-S. Chung
Keyword(s):  
Cell Concentration ◽  
Removal Rate ◽  
Carbon Sources ◽  
Batch Reactors ◽  
Initial Cell Concentration ◽  
Removal Rates ◽  
Initial Cell ◽  
Toluene Concentration ◽  
Cell Source ◽  
Removal Efficiencies

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 μg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95 μg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 μg/L-hr at toluene concentration of 1 mg/L.

Increasing Precision without Altering Treatment Effects: Repeated Measures Designs in Survey Experiments

2021 ◽  
pp. 1-18
Author(s):  
SCOTT CLIFFORD ◽  
GEOFFREY SHEAGLEY ◽  
SPENCER PISTON
Keyword(s):  
Treatment Effect ◽  
Repeated Measures ◽  
Treatment Effects ◽  
Repeated Measurements ◽  
Experimental Designs ◽  
Treatment Effect Size ◽  
Standard Design ◽  
Survey Experiments ◽  
Repeated Measures Designs ◽  
Alternative Designs

The use of survey experiments has surged in political science. The most common design is the between-subjects design in which the outcome is only measured posttreatment. This design relies heavily on recruiting a large number of subjects to precisely estimate treatment effects. Alternative designs that involve repeated measurements of the dependent variable promise greater precision, but they are rarely used out of fears that these designs will yield different results than a standard design (e.g., due to consistency pressures). Across six studies, we assess this conventional wisdom by testing experimental designs against each other. Contrary to common fears, repeated measures designs tend to yield the same results as more common designs while substantially increasing precision. These designs also offer new insights into treatment effect size and heterogeneity. We conclude by encouraging researchers to adopt repeated measures designs and providing guidelines for when and how to use them.

scholarly journals Estimating and reporting treatment effects in clinical trials for weight management: using estimands to interpret effects of intercurrent events and missing data

2021 ◽  
Author(s):  
Sean Wharton ◽  
Arne Astrup ◽  
Lars Endahl ◽  
Michael E. J. Lean ◽  
Altynai Satylganova ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Missing Data ◽  
Weight Management ◽  
Treatment Effect ◽  
Repeated Measures ◽  
Treatment Effects ◽  
Randomized Clinical Trials ◽  
Weight Losses ◽  
The Difference ◽  
Treatment Of Obesity

AbstractIn the approval process for new weight management therapies, regulators typically require estimates of effect size. Usually, as with other drug evaluations, the placebo-adjusted treatment effect (i.e., the difference between weight losses with pharmacotherapy and placebo, when given as an adjunct to lifestyle intervention) is provided from data in randomized clinical trials (RCTs). At first glance, this may seem appropriate and straightforward. However, weight loss is not a simple direct drug effect, but is also mediated by other factors such as changes in diet and physical activity. Interpreting observed differences between treatment arms in weight management RCTs can be challenging; intercurrent events that occur after treatment initiation may affect the interpretation of results at the end of treatment. Utilizing estimands helps to address these uncertainties and improve transparency in clinical trial reporting by better matching the treatment-effect estimates to the scientific and/or clinical questions of interest. Estimands aim to provide an indication of trial outcomes that might be expected in the same patients under different conditions. This article reviews how intercurrent events during weight management trials can influence placebo-adjusted treatment effects, depending on how they are accounted for and how missing data are handled. The most appropriate method for statistical analysis is also discussed, including assessment of the last observation carried forward approach, and more recent methods, such as multiple imputation and mixed models for repeated measures. The use of each of these approaches, and that of estimands, is discussed in the context of the SCALE phase 3a and 3b RCTs evaluating the effect of liraglutide 3.0 mg for the treatment of obesity.

Inference for treatment effect parameters in potentially misspecified high-dimensional models

Biometrika ◽  
2020 ◽  
Author(s):  
Oliver Dukes ◽  
Stijn Vansteelandt
Keyword(s):  
Sample Size ◽  
Confidence Intervals ◽  
Treatment Effect ◽  
Observational Studies ◽  
Treatment Effects ◽  
Treatment Selection ◽  
High Dimensional ◽  
Selection Mechanism ◽  
Dimensional Models ◽  
Effect Parameter

Summary Eliminating the effect of confounding in observational studies typically involves fitting a model for an outcome adjusted for covariates. When, as often, these covariates are high-dimensional, this necessitates the use of sparse estimators, such as the lasso, or other regularization approaches. Naïve use of such estimators yields confidence intervals for the conditional treatment effect parameter that are not uniformly valid. Moreover, as the number of covariates grows with the sample size, correctly specifying a model for the outcome is nontrivial. In this article we deal with both of these concerns simultaneously, obtaining confidence intervals for conditional treatment effects that are uniformly valid, regardless of whether the outcome model is correct. This is done by incorporating an additional model for the treatment selection mechanism. When both models are correctly specified, we can weaken the standard conditions on model sparsity. Our procedure extends to multivariate treatment effect parameters and complex longitudinal settings.

scholarly journals Use of Aloe vera as an Organic Coagulant for Improving Drinking Water Quality

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2024
Author(s):  
Abderrezzaq Benalia ◽  
Kerroum Derbal ◽  
Amel Khalfaoui ◽  
Raouf Bouchareb ◽  
Antonio Panico ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Suspended Solids ◽  
Aluminum Sulfate ◽  
Aloe Vera ◽  
Drinking Water Treatment ◽  
Water Turbidity ◽  
Turbidity Removal ◽  
Maximum Turbidity ◽  
Optimal Ph

The coagulation–flocculation–sedimentation process is widely used for removal of suspended solids and water turbidity reduction. The most common coagulants used to conduct this process are aluminum sulfate and ferric sulfate. In this paper, the use of Aloe vera as a natural-based coagulant for drinking water treatment was tested. The bio-coagulant was used in two different forms: powder as well as liquid; the latter was extracted with distilled water used as a solvent. The obtained results showed that the use of the natural coagulant (Aloe vera) in both powder (AV-Powder) and liquid (AV-H2O) forms reduced the water turbidity at natural pH by 28.23% and 87.84%, respectively. Moreover, it was found that the use of the two previous forms of bio-coagulant for drinking water treatment had no significant influence on the following three parameters: pH, alkalinity, and hardness. The study of the effect of pH on the process performance using Aloe vera as a bio-coagulant demonstrated that the maximum turbidity removal efficiency accounted for 53.53% and 88.23% using AV-Powder and AV-H2O, respectively, at optimal pH 6.

scholarly journals Blinding, sham, and treatment effects in randomized controlled trials for back pain in 2000–2019: A review and meta-analytic approach

2021 ◽  
pp. 174077452098487
Author(s):  
Brian Freed ◽  
Brian Williams ◽  
Xiaolu Situ ◽  
Victoria Landsman ◽  
Jeehyoung Kim ◽  
...  
Keyword(s):  
Back Pain ◽  
Active Treatment ◽  
Treatment Effect ◽  
Effect Size ◽  
Treatment Effects ◽  
Effect Sizes ◽  
Controlled Trials ◽  
Sham Treatment ◽  
Randomized Controlled ◽  
Random Guess

Background: Blinding aims to minimize biases from what participants and investigators know or believe. Randomized controlled trials, despite being the gold standard to evaluate treatment effect, do not generally assess the success of blinding. We investigated the extent of blinding in back pain trials and the associations between participant guesses and treatment effects. Methods: We did a review with PubMed/OvidMedline, 2000–2019. Eligibility criteria were back pain trials with data available on treatment effect and participants’ guess of treatment. For blinding, blinding index was used as chance-corrected measure of excessive correct guess (0 for random guess). For treatment effects, within- or between-arm effect sizes were used. Analyses of investigators’ guess/blinding or by treatment modality were performed exploratorily. Results: Forty trials (3899 participants) were included. Active and sham treatment groups had mean blinding index of 0.26 (95% confidence interval: 0.12, 0.41) and 0.01 (−0.11, 0.14), respectively, meaning 26% of participants in active treatment believed they received active treatment, whereas only 1% in sham believed they received sham treatment, beyond chance, that is, random guess. A greater belief of receiving active treatment was associated with a larger within-arm effect size in both arms, and ideal blinding (namely, “random guess,” and “wishful thinking” that signifies both groups believing they received active treatment) showed smaller effect sizes, with correlation of effect size and summary blinding indexes of 0.35 ( p = 0.028) for between-arm comparison. We observed uniformly large sham treatment effects for all modalities, and larger correlation for investigator’s (un)blinding, 0.53 ( p = 0.046). Conclusion: Participants in active treatments in back pain trials guessed treatment identity more correctly, while those in sham treatments tended to display successful blinding. Excessive correct guesses (that could reflect weaker blinding and/or noticeable effects) by participants and investigators demonstrated larger effect sizes. Blinding and sham treatment effects on back pain need due consideration in individual trials and meta-analyses.

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