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Open AccessArticle

Evaluating the Applicability of High-Speed Air Flotation Technology for Water Supply: A Case Study in Tianjin Binhai New Area

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Separations 2022, 9(11), 362; https://doi.org/10.3390/separations9110362 - 09 Nov 2022

Cited by 2 | Viewed by 875

Abstract

The development and application of advanced water purification technology is crucial to guarantee a sufficient supply of clean water. However, conventional water purification technology consumes large amounts of coagulants, with the formation of intractable sludge. Herein, the applicability of high-speed air flotation technology [...] Read more.

The development and application of advanced water purification technology is crucial to guarantee a sufficient supply of clean water. However, conventional water purification technology consumes large amounts of coagulants, with the formation of intractable sludge. Herein, the applicability of high-speed air flotation technology for the purification of actual water sources was evaluated in Tianjin Binhai New Area. During a three-year survey, the raw water exhibited periodic pollution characteristics with algae cells as the main removal targets in all seasons. The raw water had both low temperatures and low turbidity in winter, another obstacle for water treatment. Based on the scientific analysis of the water’s quality, the water purification process was comprehensively optimized via regulating the dosage of agents and operating parameters and using high-speed air flotation equipment. The results showed that a dissolved air pressure of 0.40 MPa, reflux ratio of 8%, and SUEZ-1# dissolved air release head combined with pre-chlorination with PACl plus FeCl₃ (PACl/FeCl₃ ratio = 2:1) were suitable for attaining a good purification performance. High turbidity removal rates (80.9–86.2%) and algae cell removal rates (92.5–98.1%) were obtained even in the high algae period of summer and low turbidity period in the winter, proving the superior stability and applicability of the high-speed air flotation system. Full article

(This article belongs to the Special Issue Application of Separation Technology in Soil and Groundwater Remediation)

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Open AccessArticle

Effects of Ecological Restoration on the Distribution of Soil Particles and Organic Carbon in Alpine Regions

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Separations 2022, 9(10), 279; https://doi.org/10.3390/separations9100279 - 01 Oct 2022

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Abstract

This study discusses the impact of two different ecological restoration approaches on the distribution of soil particle size and organic carbon, expecting to provide references for research on the effects of ecological restoration on the soil carbon pool in alpine regions. By replacing [...] Read more.

This study discusses the impact of two different ecological restoration approaches on the distribution of soil particle size and organic carbon, expecting to provide references for research on the effects of ecological restoration on the soil carbon pool in alpine regions. By replacing the method of time sampling with spatial sampling, grasslands enclosed only in the growing season and woodlands enclosed all year round were respectively selected as the research objects. Through centrifugation, the soil samples were classified by grain size into sand (50–2000 μm), silt (2–50 μm), and clay (<2 μm) to analyze the distribution of organic carbon in soil particles of different sizes. The major findings were as follows. First, sand accounted for the largest proportion of all the soil components in the grasslands and woodlands that had been restored for different years, followed by silt and clay. Second, most of the organic carbon in the grasslands and woodlands was from sand and silt. As the restoration years increased, the proportion of organic carbon in clay grew in fluctuation. In short, both ecological restoration approaches have improved the soil structure and raised the content of soil organic carbon (SOC). Specifically, the restoration scheme of the woodlands exerted a more significant influence on the soil components and the distribution of organic carbon than that of the grasslands. Full article

(This article belongs to the Special Issue Application of Separation Technology in Soil and Groundwater Remediation)

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Open AccessArticle

Comparison of Fenton and Ozone Oxidation for Pretreatment of Petrochemical Wastewater: COD Removal and Biodegradability Improvement Mechanism

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Separations 2022, 9(7), 179; https://doi.org/10.3390/separations9070179 - 18 Jul 2022

Cited by 2 | Viewed by 1174

Abstract

Cost-effective pretreatment of highly concentrated and bio-refractory petrochemical wastewater to improve biodegradability is of significant importance, but remains challenging. This study compared the pretreatment of petrochemical wastewater by two commonly used chemical advanced oxidation technologies (Fenton and ozone oxidation), and the mechanisms of [...] Read more.

Cost-effective pretreatment of highly concentrated and bio-refractory petrochemical wastewater to improve biodegradability is of significant importance, but remains challenging. This study compared the pretreatment of petrochemical wastewater by two commonly used chemical advanced oxidation technologies (Fenton and ozone oxidation), and the mechanisms of biodegradability improvement of pretreated wastewater were explored. The obtained results showed that in the Fenton oxidation system, the COD removal of petrochemical wastewater was 89.8%, BOD₅ decreased from 303.66 mg/L to 155.49 mg/L, and BOD₅/COD (B/C) increased from 0.052 to 0.62 after 60 min under the condition of 120 mg/L Fe²⁺ and 500 mg/L H₂O_2, with a treatment cost of about 1.78 $/kg_COD. In the ozone oxidation system, the COD removal of petrochemical wastewater was 59.4%, BOD₅ increased from 127.86 mg/L to 409.28 mg/L, and B/C increased from 0.052 to 0.41 after 60 min at an ozone flow rate of 80 mL/min with a treatment cost of approximately 1.96 $/kg_COD. The petrochemical wastewater treated by both processes meets biodegradable standards. The GC–MS analysis suggested that some refractory pollutants could be effectively removed by ozone oxidation, but these pollutants could be effectively degraded by hydroxyl radicals (^•OH) produced by the Fenton reaction. In summary, compared with ozone oxidation, petrochemical wastewater pretreated with Fenton oxidation had high COD removal efficiency and biodegradability, and the treatment cost of Fenton oxidation was also lower than that of ozone oxidation. Full article

(This article belongs to the Special Issue Application of Separation Technology in Soil and Groundwater Remediation)

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