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Relation of pre-chlorination contact time and DOC concentration (Left) and UV 254 (Right) before coagulation (at 30 mg L-1 of alum dose). The results are shown with average and standard deviations from triplicate experiments.
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The use of pre-oxidation is known to improve algae removal by coagulation and control the growth of algae. The contact time between oxidants and algae in pre-oxidation stage has been found as important parameter. This study investigated the effect of pre-chlorination contact time on the control and removal of cyanobacteria Microcystis aeruginosa by...
Contexts in source publication
Context 1
... concentration before coagulation of chlorine 3 mg L -1 was higher than those 2 mg L -1 at every contact time (Figure 3). DOC concentration before coagulation of chlorine 3 mg L -1 increased gradually during 5 to 20 minutes of contact time and then largely increased at 30 minutes of contact time. ...
Context 2
... of UV at 254 has been used as organic compounds monitoring parameter, especially aromatic compounds throughout water treatment plants. In this study, UV 254 showed large increase in case of chlorine 3 mg L -1 , particularly at 30 minutes of contact time and then decreased at 60 minutes of contact time (Figure 3). The decrease of UV 254 at 60 minutes might be resulted from the degradation of high MW organics to lower MW organics by chlorine [12,13]. ...
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In recent years, in-situ fluorometers have been extensively deployed to monitor cyanobacteria in near real-time. Acceptable accuracy can be achieved between measured pigments and cyanobacteria biovolume provided the cyanobacteria species are known. However, cellular photosynthetic pigment content and measurement interferences are site and species s...
Citations
... One possible strategy to reduce DBP levels in treated water is for WTP operators to perform the chlorination step after coagulation, sedimentation, and filtration, which significantly reduces THM formation, sometimes by more than 50% (García & Moreno 2009). However, eliminating the pre-chlorination step may not be a viable option, as it has been used for controlling biological growth, taste, and odor during water treatment processes (Lapsongpon et al. 2017). ...
The widespread use of chlorine pre-oxidation in water purification has been limited in several countries owing to the production of carcinogenic byproducts when combined with naturally occurring organic matter. This study investigates the efficient use of potassium permanganate (KMnO4) pretreatment and coagulation enhancement as particle size and molecular weight distribution controlling parameters. KMnO4 pretreatment significantly reduced the apparent molecular weight of humic acid due to KMnO4 reduction and the continuous generation of manganese dioxide (MnO2) formed in situ under neutral and alkaline conditions. The MnO2 formed in situ had adsorption characteristics that enabled it to form large and stable flocs with the hydrolysis products of aluminum sulfate. However, under acidic conditions, KMnO4 pretreatment exhibited strong oxidation characteristics due to Mn(VII) reduction to Mn(II), and the mean particle floc size was the same as without KMnO4 pretreatment. Overall, KMnO4 pretreatment is a useful alternative strategy for traditional pre-oxidation using chlorine and a good coagulant enhancement agent in neutral and basic media.
HIGHLIGHTS
pH is crucial in the KMnO4 pretreatment mechanism.;
Under acidic conditions, KMnO4 pretreatment results in the same mean particle floc size as alum alone.;
The in situ formed MnO2 is incorporated with the alum hydrolysis product, forming larger flocs.;
KMnO4 pretreatment under optimal conditions results in a significant reduction in the molecular weight distribution of humic acid.;
... This factor refers to verifying if the dosage of an oxidizing agent, such as sodium hypochlorite (NaOCl), in the volume of the mixture can reduce the color coming from the organic load of the wastewater. Previous studies have found that pre-chlorination is a reliable strategy for removing organic material, such as algae, followed by a coagulationflocculation process [43,44]. Natural organic matter reacts with chlorine to produce halogenated byproducts in water treatment [45]. ...
Determining the optimal dose of coagulant required to perform flocculation is critical in
most water treatment plants’ planning and operation. This study implemented a 2k–p fractional factorial design of experiments to identify the factors influencing the color decrease of wastewater from a slaughterhouse. The variables assessed were the velocity gradient, residence time, primary coagulant dosage, chlorine dosage, and coagulation adjuvant dosage. The results indicate that the primary coagulant dose and the velocity gradient significantly affect the samples’ color and that the other factors can be run at a low technical-economic level to start up the water treatment plant. The fractional factorial design allowed reducing the number of experimental points without affecting the minimum information required to identify which factors are significant in reducing the color of a wastewater sample.
... For example, Jiang et al. [82] reported 100% M. aeruginosa removal efficiency under an optimal dosage of 2 mg/L magnetic nanoparticles at pH 10. Ma et al. [83] reported a cell removal efficiency of only about 65% with an alum dosage of 4.1 mg/L at an initial M. aeruginosa of 2.2 × 10 6 cells/mL cell density. Lapsongpon et al. [84] demonstrated that 30 mg/L alum is sufficient to achieve 90% M. aeruginosa cell removal efficiency at pH 7.5. Zhang et al. [85] reported 89% M. aeruginosa cell removal efficiency with a PACl dosage of 3 mg/L, which increased to 93.5% upon sonication for 60 s with an initial cell density and pH of 10 6 cells/mL and 7.3-7.9, ...
Cyanobacteria adversely affect drinking water treatment and the quality of the drinking water supply. Microcystis spp. are the most abundant cyanobacteria in many surface water bodies throughout the world. Electrocoagulation–flotation (ECF) treatment has attracted considerable attention as a means of cyanobacteria removal. In this study, ECF treatment was optimized by adjusting the initial pH, electrode distance, stirring speed, and electrical conductivity (k) to maximize Microcystis aeruginosa cell removal efficiency while meeting drinking water quality standards. The treatment was performed for 200 mL M. aeruginosa suspensions (~2 × 10⁶ cells/mL) using an aluminum anode and a graphite cathode at a constant direct current of 100 mA. An initial pH of 6, a stirring speed of 200 rpm, an electrode distance of 1 cm, and k of 500 μS/cm were selected as optimum conditions for the ECF treatment. Under these conditions, M. aeruginosa at a cell density of ~2 × 10⁶ cells/mL was completely removed at a current density of 4.0 mA/cm² with an average energy consumption of 1.20 ± 0.03 Wh/L. The zeta potential varied from −18.49 ± 3 mV to 1.15 ± 0.38 mV, which confirmed the complete removal of cells. Most importantly, the pH, aluminum concentration, and total dissolved solids of the treated water met the drinking water quality standards of the World Health Organization. The optimized ECF treatment was thus shown to be promising for the removal of M. aeruginosa cells.
... The impact of pre-oxidation on downflow processes should also be considered as it may influence the removal of cyanobacteria by coagulation, flocculation, and sedimentation. Previous studies have been reported that pre-oxidation has a positive impact on enhancing cyanobacterial removal through coagulation/flocculation and sedimentation [27,28,31,32,34,90]. Pre-oxidation can cause morphological deformation [82] and changes in the surface charge of the cells, leading to increased cell removal efficiency during coagulation/flocculation [37]. ...
Freshwater bodies and, consequently, drinking water treatment plants (DWTPs) sources are increasingly facing toxic cyanobacterial blooms. Even though conventional treatment processes including coagulation, flocculation, sedimentation, and filtration can control cyanobacteria and cell-bound cyanotoxins, these processes may encounter challenges such as inefficient removal of dissolved metabolites and cyanobacterial cell breakthrough. Furthermore, conventional treatment processes may lead to the accumulation of cyanobacteria cells and cyanotoxins in sludge. Pre-oxidation can enhance coagulation efficiency as it provides the first barrier against cyanobacteria and cyanotoxins and it decreases cell accumulation in DWTP sludge. This critical review aims to: (i) evaluate the state of the science of cyanobacteria and cyanotoxin management throughout DWTPs, as well as their associated sludge, and (ii) develop a decision framework to manage cyanobacteria and cyanotoxins in DWTPs and sludge. The review identified that lab-cultured-based pre-oxidation studies may not represent the real bloom pre-oxidation efficacy. Moreover, the application of a common exposure unit CT (residual concentration × contact time) provides a proper understanding of cyanobacteria pre-oxidation efficiency. Recently, reported challenges on cyanobacterial survival and growth in sludge alongside the cell lysis and cyanotoxin release raised health and technical concerns with regards to sludge storage and sludge supernatant recycling to the head of DWTPs. According to the review, oxidation has not been identified as a feasible option to handle cyanobacterial-laden sludge due to low cell and cyanotoxin removal efficacy. Based on the reviewed literature, a decision framework is proposed to manage cyanobacteria and cyanotoxins and their associated sludge in DWTPs.
... Except at a temperature of 45 o C and the addition of HCl 3%(v/v), there is a maximum decrease in residual chlorine. This is due to the temperature of 45 o C and the addition of HCl 3% (v/v), pH of solution 7 where at pH 7 occurs the reaction equilibrium so that the residual chlorine is at the lowest concentration [13][14][15]. By using high heating, oxidation reaction occurs hypochlorine to chlorine and reserved so that at a temperature of 45 o C is the equilibrium reaction point between hyprochlorine with chlorine. ...
In the seaweed processing industry to obtain quality products that are free of microorganisms, high concentrations of chlorine are used in the cooking process. Thus the wastewater from the cooking process still contains high concentrations of residual chlorine, where the wastewater when disposed of into the aquatic environment can cause pollution and damage of environmental. The aim of the research is the reduction of high concentrations of residual chlorine in seaweed wastewater using a combination process of aeration, heating and addition of Hypochlorous acid (HCl). The experiment was conducted by adding wastewater from the seaweed cooking process with HCl (1; 2; 3; and 4% v/v), aeration flowrate (1; 1.5; 2; and 2.5 Ls/minute) and heating temperature (35; 40; 45; and 50°C). Residual chlorine concentration was measured using the iodometric method. The experimental results showed that the maximum reduction of residual chlorine by 96.3% was obtained by adding HCl by 3%, aeration flowrate of 2.5 L/minute and heating temperature of 45°C.
... Furthermore, at percentage more than 20% these wastes can be a source of low- quality fuel for heating up of an engineering and utility services room. A technique for controlling of the water plant species of Cyanobacteria Microcystis Aeruginosa on water and wastewater treatment facility is presented in [3]. ...
A mathematical model of RF discharge between metal rod and liquid electrodes in argon media at decreasing pressure in range of 10³-10⁵ Pa at a local approach is constructed. Electrons, atomic and dimer ions, excited atoms and dimers of Ar as well as effect of vorticity electromagnetic field and processes on plasma-liquid interphase boundary are considered.
... Plasma technologies have also been found wide application in other areas of environmental protection. For example, in [5] a method is given for controlling algae cyanobacteria Microcystis aeruginosa in treatment plants. In [6], a breakthrough system is developed by assisting the acid hydrolysis with two-step microwave treatment to improve the more efficient saccharification process of starch and fiber from sago pith. ...
Self-consistent mathematical models of a non-equilibrium low-temperature plasma of a radio frequency capacitive discharge in argon in different pressure ranges have been created. These mathematical models allow us to calculate the internal structure and discharge parameters for controlling parameters of the plasma torches at solving the target problems in order to optimize their functioning. The methods for numerical realization of the proposed models are developed. The results of numerical calculations for test problems are analyzed.
Disposal of municipal solid waste is an environmental burden worldwide, and landfilling is still the widely applied solution for the management of discarded solid waste because of its cost-effectiveness and simpler operational mechanism. Due to the complex reactions inside, landfills generate severely polluted wastewater streams recognized as leachate. Leachate is concentrated wastewater with extreme pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), organic refractory compounds, inorganic salts and toxicity. It is a typical dilemma of a landfill system and a potential threat for environmental elements, which must be treated before discharge into water bodies. Because of the variability in waste composition depending on the landfilling practice, local climatic conditions, landfill’s physicochemical conditions, bio geochemistry and landfill age, treatment of leachate becomes more critical than municipal wastewater. Numerous biological, physicochemical treatment methods are being practised worldwide for landfill leachate. This chapter aims to summarize an overview of the different innovative options applied for landfill leachate treatment and the way forward.KeywordsBiological treatmentChemical treatmentMunicipal solid wastePhysical treatmentSemi-aerobic landfillLeachate
Preoxidation–coagulation is adopted by many drinking water treatment plants to enhance the removal of cyanobacteria. However, conventional technologies — such as the combination of prechlorination with Al-salt coagulation — can easily induce secondary pollution caused by cell lysis and yield unsatisfactory performance both in removal of cyanobacterial cells and metabolites and in alleviation of filter unit fouling. To solve these issues, an iron-based coupled process of moderate preoxidation–hybrid coagulation was invented. In this technology Fe(VI) can moderately oxidize algal cells, resulting in the removal of electronegative organics coating the surfaces of the cells without destroying the algae. After preoxidation, in-situ Fe(III) produced from Fe(VI) will form a highly effective hybrid coagulant by adding a low dose of chitosan quaternary ammonium salt. Combining the reduction of electrostatic repulsion between algal cells obtained from K2FeO4 preoxidation with the enhancement of charge neutralization, polymer bridging and adsorption capability obtained from hybrid coagulation, 92.6% of Microcystis aeruginosa cells were removed and the DOC and microcystin concentrations respectively decreased from 23.54 to 7.63 mg/L and from 16.2 to 0.96 mg/L. Meanwhile the membrane fouling was markedly alleviated. Hence this new technology couples moderate preoxidation and hybrid coagulation through the Fe(VI)–Fe(III) pairing, which is safer and more effective and can thus be a better alternative for cyanobacterial removal in drinking water treatment plants.
Excessive proliferation of cyanobacteria blooms resulting in metabolic musty-earthy odor materials such as geosmin (GSM) pose potential risks to aquatic ecosystems and human health. In this paper, a high-yield OH equipment was developed to be installed in drinking water treatment system with a capacity of 12,000 m³/day in the Xiang’an Water Plant, Xiamen, China, and the comparison of OH and NaClO on GSM degradation in the process of algae colonies inactivation were studied. The results showed that with OH inactivation at 1.0 mg/L within 20 s algae colonies were scattered to individual algae that still had intact shape, while with the NaClO inactivation at 2 h algae still mainly existed as colonies form but were deformed and ruptured due to extensive damage of cell membrane. After the coagulation sedimentation with injection of OH at 1.0 mg/L and the sand filtration at 0.5 mg/L, the GSM were both degraded to below 10 ng/L (Chinese standard limit) within only 20 s, while the NaClO degraded GSM slightly until 2 h later. Based on the intermediates analyses with mass spectra database, pathways of GSM degradation by OH or NaClO were obtained. With OH disinfection at 0.5 mg/L, all water quality and disinfection by-product indexes satisfied the limits of Chinese Standards. Therefore, the OH method based on the strong ionization discharge showed great prospect for large-scale industrial application in inactivation of algae colonies meanwhile degradation of odorous material GSM.
