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Coagulation and Flocculation in Water and Wastewater Treatment (3rd Edition)
This book provides a comprehensive account of coagulation and flocculation techniques and technologies in a single volume covering theoretical principles to practical applications. Thoroughly revised and updated this new edition has been progressively modified and increased in scope to cater for the requirements of practitioners involved with water and wastewater treatment. New topics in this new edition include: activated sludge bulking and foaming control and enhanced bioflocculation; algae removal and harvesting; dissolved organic nitrogen (DON) removal; inorganics removal; turbidity and its measurement; wastewater treatment by coagulation and chemically enhanced primary treatment (CEPT). The book presents the subject logically and sequentially from theoretical principles to practical applications.
eBook
Wastewater treatment alters microbial colonization of microplastics
Microplastics are ubiquitous contaminants in aquatic habitats globally, and wastewater treatment plants (WWTPs) are point sources of microplastics. Within aquatic habitats microplastics are colonized by microbial biofilms, which can include pathogenic taxa and taxa associated with plastic breakdown. Microplastics enter WWTPs in sewage and exit in sludge or effluent, but the role that WWTPs play in establishing or modifying microplastic bacterial assemblages is unknown. We analyzed microplastics and associated biofilms in raw sewage, effluent water, and sludge from two WWTPs. Both plants retained >99% of influent microplastics in sludge, and sludge microplastics showed higher bacterial species richness and higher abundance of taxa associated with bioflocculation (e.g. Xanthomonas ) than influent microplastics, suggesting that colonization of microplastics within the WWTP may play a role in retention. Microplastics in WWTP effluent included significantly lower abundances of some potentially pathogenic bacterial taxa (e.g. Campylobacteraceae ) compared to influent microplastics; however, other potentially pathogenic taxa (e.g. Acinetobacter ) remained abundant on effluent microplastics, and several taxa linked to plastic breakdown (e.g. Klebsiella , Pseudomonas , and Sphingomonas ) were significantly more abundant on effluent compared to influent microplastics. These results indicate that diverse bacterial assemblages colonize microplastics within sewage and that WWTPs can play a significant role in modifying the microplastic-associated assemblages, which may affect the fate of microplastics within the WWTPs and the environment.
Journal Article
Evaluation of Methods for the Concentration and Extraction of Viruses from Sewage in the Context of Metagenomic Sequencing
Viral sewage metagenomics is a novel field of study used for surveillance, epidemiological studies, and evaluation of waste water treatment efficiency. In raw sewage human waste is mixed with household, industrial and drainage water, and virus particles are, therefore, only found in low concentrations. This necessitates a step of sample concentration to allow for sensitive virus detection. Additionally, viruses harbor a large diversity of both surface and genome structures, which makes universal viral genomic extraction difficult. Current studies have tackled these challenges in many different ways employing a wide range of viral concentration and extraction procedures. However, there is limited knowledge of the efficacy and inherent biases associated with these methods in respect to viral sewage metagenomics, hampering the development of this field. By the use of next generation sequencing this study aimed to evaluate the efficiency of four commonly applied viral concentrations techniques (precipitation with polyethylene glycol, organic flocculation with skim milk, monolithic adsorption filtration and glass wool filtration) and extraction methods (Nucleospin RNA XS, QIAamp Viral RNA Mini Kit, NucliSENS® miniMAG®, or PowerViral® Environmental RNA/DNA Isolation Kit) to determine the viriome in a sewage sample. We found a significant influence of concentration and extraction protocols on the detected viriome. The viral richness was largest in samples extracted with QIAamp Viral RNA Mini Kit or PowerViral® Environmental RNA/DNA Isolation Kit. Highest viral specificity were found in samples concentrated by precipitation with polyethylene glycol or extracted with Nucleospin RNA XS. Detection of viral pathogens depended on the method used. These results contribute to the understanding of method associated biases, within the field of viral sewage metagenomics, making evaluation of the current literature easier and helping with the design of future studies.
Journal Article
Challenges and Opportunities of Biocoagulant/Bioflocculant Application for Drinking Water and Wastewater Treatment and Its Potential for Sludge Recovery
The utilization of metal-based conventional coagulants/flocculants to remove suspended solids from drinking water and wastewater is currently leading to new concerns. Alarming issues related to the prolonged effects on human health and further pollution to aquatic environments from the generated nonbiodegradable sludge are becoming trending topics. The utilization of biocoagulants/bioflocculants does not produce chemical residue in the effluent and creates nonharmful, biodegradable sludge. The conventional coagulation–flocculation processes in drinking water and wastewater treatment, including the health and environmental issues related to the utilization of metal-based coagulants/flocculants during the processes, are discussed in this paper. As a counterpoint, the development of biocoagulants/bioflocculants for drinking water and wastewater treatment is intensively reviewed. The characterization, origin, potential sources, and application of this green technology are critically reviewed. This review paper also provides a thorough discussion on the challenges and opportunities regarding the further utilization and application of biocoagulants/bioflocculants in water and wastewater treatment, including the importance of the selection of raw materials, the simplification of extraction processes, the application to different water and wastewater characteristics, the scaling up of this technology to a real industrial scale, and also the potential for sludge recovery by utilizing biocoagulants/bioflocculants in water/wastewater treatment.
Journal Article
Enhancing the efficiency of coagulation method for sewage treatment by adding sludge
The high performance sedimentation tank (HPST) is an efficient water treatment technology, which accelerates the settling rate of flocculates by adding sludge, so as to increase the water treatment load of coagulation sedimentation tank. Its sewage treatment effect is affected by many factors such as sludge dosage, wastewater pH, flocculant dosage, stirring time, settling time, etc. This paper was to study the optimal conditions of HPST, first, some single-factor tests were conducted to preliminarily explore the optimal range of influencing factors, and then response surface methodology (RSM) tests were performed to accurately determine the optimums of significant factors.The results showed that adding sludge can not improve the water quality of coagulation treatment, but it can significantly accelerate the coagulation settlement process, the sludge dosage, the coagulant dosage and sewage pH all impacted significantly on its coagulation effect, and existed inflection points. A model that could guide HPST was obtained by RSM tests. The model optimization and experimental validation showed that the optimal HPST conditions for treating domestic sewage were as follows: the dosage of polyaluminum chloride (PAC) was 1.70 g/L, cationic polyacrylamide (CPAM) dosage was 2.35 mg/L, sewage pH was maintained at 8.0, sludge dosage was 10 mL/L, stirring time lasted for 5 minutes, and settling time lasted for 30 minutes. As a result of these optimized conditions, the turbidity of treated sewage decreased to 1.19 NTU.
Journal Article
Characterisation, Flocculation Efficiencies and Mechanisms of Bioflocculants Derived from Klebsiella pneumoniae and Meyerozyma guilliermondii
Evaluation of characteristics and flocculation mechanisms of microbial flocculants facilitates the identification of potential applications and informs the fine-tuning of operational conditions for maximum activity. Therefore, this study aimed to characterise and optimise the operational conditions of bioflocculants produced from Klebsiella pneumoniae and Meyerozyma guilliermondii for potent wastewater treatment. Scanning electron microscopy, X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to assess the surface morphology, crystalline structure, thermal stability, and functional group composition of the bioflocculants. Their cytotoxicity was assessed using the tetrazolium bromide-based assay against human colorectal adenocarcinoma (CaCO-2) cell lines. Flocculation efficiencies and mechanisms were determined using Jar and zeta potential assays, respectively. The bioflocculant from K. pneumoniae (Kp1) revealed a fibrous morphology, whereas that from M. guilliermondii (Mg1) displayed a granular structure. FTIR spectra revealed hydroxyl, amine, and alkene groups as key functional groups, while TGA analysis indicated that Kp1 was thermally unstable, contrary to Mg1, which exhibited good thermal stability. Bioflocculants Kp1 and Mg1 exhibited COD removal of 90.86% and 93.12% and turbidity reductions of 92.65% and 92.74%, respectively. Zeta potential analysis revealed that bioflocculant Kp1 primarily flocculated through charge neutralisation, while Mg1 employed a bridging mechanism. These bioflocculants illustrated strong potential to treat wastewater. However, the observed cytotoxic effect at increased concentrations warrants cautious handling and application in lower doses.
Journal Article
A novel Pseudomonas sp. strain with high flocculation efficiency for aquaculture wastewater treatment
A bacterium showing excellent flocculation performance was isolated from sludge. Through 16S rDNA sequencing, morphological observation, and enzyme characterization, the strain was found to represent a novel bacterium of the
Pseudomonas
sp., termed
Pseudomonas
sp. GXUN74702.
Pseudomonas
sp. GXUN74702 was isolated from the sludge of Siyuan Lake in Guangxi Minzu University. Research showed that strain GXUN74702 had good flocculation performance. After the strain was cultured in fermentation medium (pH 7.0) containing glucose as carbon and urea as nitrogen, shaking at 30 °C 180 rpm for 36 h, the flocculation rate reached 92.5% when treating kaolin suspension with 2 mL of the fermentation broth. The microbial flocculants (MBF) GXUN74702 contained 78.90% total sugars and 6.78% protein. Ion chromatography detection showed that the monosaccharide constituents of MBF-GXUN74702 were most mannose (10.55 µg/mg), glucose (5.34 µg/mg), and glucosamine hydrochloride (1.48 µg/mg). The use of MBF-GXUN74702 for treating aquaculture wastewater was then explored, demonstrating chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal rates of 52% and 20%, respectively. In summary,
Pseudomonas
sp. GXUN74702 is a newly identified
Pseudomonas
sp. strain that shows highly efficient flocculation performance in treating aquaculture wastewater, suggesting its potential value in wastewater treatment applications. The fermentation medium components of
Pseudomonas
sp. GXUN74702 identified in this study are simple and easy to obtain, and the fermentation conditions of the strain are mild and not harsh, so a large number of fermentation liquid with high flocculation performance can be obtained in a short time. The main component of MBF-GXUN74702 has been proved to be polysaccharides that are superior to inorganic and synthetic organic flocculants owing to their non-toxicity, biodegradability, high efficiency, free secondary pollution, and wide adaption to pH variation. At present, the team has obtained the flocculants powder of the strain under laboratory conditions. The production process of this powder is simple, the yield and flocculation rate are high, and the property is stable and easy to preserve.
Journal Article
Optimization of Coagulation-Flocculation Process in Efficient Arsenic Removal from Highly Contaminated Groundwater by Response Surface Methodology
Elevated arsenic (As) contamination in water, especially groundwater, has been recognized as a major problem of catastrophic proportions. This work explores As(V) removal via the coagulation-flocculation process by use of ferric chloride coagulant and polyacrylamide k16 co-coagulant as a first time. The effects of major operating variables such as coagulant dosing (50, 125 and 200 mg/L), co-coagulant dosing (5, 12.5 and 20 mg/L), pH (6, 7and 8), fast mixing time (1, 2 and 3 min), and fast mixing speed (110, 200 and 300 rpm) on As(V) removal efficiency were investigated by a Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM). According to factors F values, coagulant dosing, rapid mixing speed, pH, and co-coagulant dosing showed the most effect on As(V) removal efficiency, and the rapid mixing time factor indicated the slightest effect. The proposed quadratic model was significant with a p value < 0.0001 and has satisfactorily described the experimental data with R2 and adjusted R2 values of 0.9855 and 0.9738, respectively. Predicted model optimal conditions with target of complete As(V) removal were coagulant dosing = 197.63 ppm, co-coagulant dosing = 19.55 ppm, pH = 7.37, fast mixing time = 1.43 min and fast mixing speed = 286.77 rpm. The treatment of Nazarabad well water sample with an initial As(V) concentration of 5 mg/L under the optimal conditions removed 100% As(V) with the volume of produced sludge of 10.7 mL/200 mL. Increasing coagulant dosing, co-coagulant dosing, fast mixing time and fast mixing speed operation parameters from low-level to high-level values indicated 78%, 20%, 10.52% and 9.47% increases in volume of the produced sludge, respectively. However, a reduction of 13.63% in volume of the produced sludge resulted via pH increases.
Journal Article
Production of Cationic Starch-Based Flocculants and Their Application in Thickening and Dewatering of the Municipal Sewage Sludge
Polymer flocculants are used to promote solid–liquid separation processes in wastewater treatment technologies, and bio-based flocculants possess many advantages over conventional synthetic polymers. Potato starch microgranules were chemically modified and mechanically sheared to produce modified starch flocculants. The effectiveness of produced cationic starch (CS) and cross-linked cationic starch (CCS) flocculants in the thickening and dewatering of surplus activated sewage sludge was evaluated and compared with that of synthetic cationic flocculants (SCFs) The flocculation efficiency of SCF, CS, and CCS in sludge thickening was determined by measuring the filtration rate of treated surplus activated sludge. Comparing the optimal dose of SCFs and CCS flocculants needed for thickening, the CCS dose was more than 10 times higher, but a wide flocculation window was determined. The impact of used flocculants on the dewatering performance of surplus activated sludge at optimal dose conditions was investigated by measuring capillary suction time. The filtration efficiencies (dewaterability) of surplus activated sludge using SCF, CS, and CCS were 69, 67, and 72%, respectively. The study results imply that mechanically processed cross-linked cationic starch has a great potential to be used as an alternative green flocculant in surplus activated sludge thickening and dewatering operations in municipal sewage sludge treatment processes.
Journal Article