Fluoride removal by a continuous flow electrocoagulation reactor

Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. Electrocoagulation (EC) is an electrochemical technique, in which a variety of unwanted dissolved particles and suspended matter can be effectively removed from an aqueous solution by electrolysis. Continuous flow experiments with monopolar aluminium electrodes for fluoride removal were undertaken to investigate the effects of the different parameters such as: current density (12.5-50A/m(2)), flow rate (150-400 mL/min), initial pH (4-8), and initial fluoride concentration (5-25mg/L). The highest treatment efficiency was obtained for the largest current and the removal efficiency was found to be dependent on the current density, the flow rate and the initial fluoride concentration when the final pH ranged between 6 and 8. The composition of the sludge produced was analysed using the X-ray diffraction (XRD) spectrum. The strong presence of the aluminium hydroxide [Al(OH)(3)] in the above pH range, which maximizes the formation of aluminium fluoride hydroxide complex [Al(n)F(m)(OH)(3n-m)], is the main reason for defluoridation by electrocoagulation. The results obtained showed that the continuous flow electrocoagulation technology is an effective process for defluoridation of potable water supplies and could also be utilized for the defluoridation of industrial wastewater.     

Positive environmental effects of the coronavirus 2020 episode: a review

Environment, Development and Sustainability - The outbreak of COVID-19 has made a global catastrophic situation that caused 1,039,406 deaths out of 35,347,404 infections, and it will also cause...     

Review of pollutants removed by electrocoagulation and electrocoagulation/flotation processes

The word “electrocoagulation” (EC) will be sometimes used with “electroflotation” (EF) and can be considered as the electrocoagulation/flotation (ECF) process. Through the process of electrolysis, coagulating agents such as metal hydroxides are produced. When aluminium electrodes are used, the aluminium dissolves at the anode and hydrogen gas is released at the cathode. The coagulating agent combines with the pollutants to form large size flocs. As the bubbles rise to the top of the tank they adhere to particles suspended in the water and float them to the surface. In fact, a conceptual framework of the overall ECF process is linked to coagulant generation, pollutant aggregation, and pollutant removal by flotation and settling when it has been applied efficiently to various water and wastewater treatment processes. This review paper considers a significant number of common applications of EC and ECF processes which have been published in journal and conference papers.     

A critical review of state-of-the-art electrocoagulation technique applied to COD-rich industrial wastewaters

Environmental Science and Pollution Research - Electrocoagulation (EC) is one of the emerging technologies in groundwater and wastewater treatment as it combines the benefits of coagulation,...     

Biosensors for pathogen surveillance

Biologists, chemists, and physicists are collaborating to develop highly sensitive and specific biosensors for pathogen detection in the food, healthcare, and environmental sectors. Those novel biosensors allow quick detection and are thus expected to solve the issues of the emergence of highly virulent or antibiotic-resistant pathogens. This article reviews different types of biosensors used for pathogen detection, classified based on the type of transducer used. Optical biosensors integrate labeled means, e.g., fluorophores, quantum dots, and carbon dots to overcome photobleaching. Surface plasmon resonance is also used for enhanced sensitivity. Mechanical biosensors with piezoelectric crystals and cantilevers are adapted for the detection of food pathogens without sample preparation or labels. Conventional methods using electrodes for the measurement of electrochemical changes with differential pulse voltammetry or impedance spectroscopy are fast and highly sensitive. Immunosensors are developed for pathogen detection at trace levels using sample enrichment, signal amplification, and new visual detection techniques.     

我国环境监测体制改革探讨

本文分析了目前我国环境监测工作中普遍存在的体制不顺、职责不明、行政干预、重复监测、资源浪费、信息混乱等问题,提出监测机构垂直管理,调整监测职能,打破条块分割,整合社会监测资源,引入第三方检测的具体构想。     

Occurrence of pesticides and polychlorinated biphenyls in water of the Nile river at the estuaries of Rosetta and Damiatta branches,north of delta,Egypt

Abstract

A study was conducted from summer 1995 to summer 1997 to assess the seasonal occurrence of pesticide residues and other organic contaminants, polychlorinated biphenyls (PCBs), in water at the estuaries of Rosetta and Damiatta branches of the Nile river. The results indicated that organochlorine compounds (OCs) including HCB, lindane, p,p‘‐DDE, p,p‘DDD, p,p‘‐DDT, aroclor 1254 and aroclor 1260 were present in all the water samples at concentration levels ranging between 0.195–0.240, 0.286–0.352, 0.035–0.067, 0.019–0.033, 0.024–0.031, 0.390–0.70 and 0.166–0.330 μg/l, respectively. The levels of these compounds were higher in water of Damiatta branch than those found in water of Rosetta branch. Aldrin, dieldrin and endrin were not detected in all water samples. Only 4 compounds from 36 organophosphorus insecticides, fungicides and s‐triazine herbicides tested were detected in water samples collected during summer and autumn seasons from Rosetta branch. The concentration levels of these detected compounds, dimethoate, malathion, captan, and ametryne, ranged from 0.011 to 0.340 μg/l, respectively. Similar compounds during the same seasons as found in water of Rosetta branch were also detected in water of Damiatta branch except ametryne. The levels of the detected compounds (dimethoate, malathion and captan) ranged between 0.030 and 0.330 μg/l. The levels of detected organophosphorus insecticides, fungicides and s‐triazine herbicides were in the order: dimethoate > malathion > captan > ametryne.     

Analysis of cost–benefit in life-cycle of plastic solid waste: combining waste flow analysis and life cycle cost as a decision support tool to the selection of optimum scenario

Millions of tons of plastic are consumed annually in the world due to its significant characteristics such as durability, flexibility, and low weight. High consumption has made plastic one of the most important municipal solid waste compounds, the quantity of which has increased in recent decades. Plastic solid wastes are known as a threat to the environment, and its efficient management in various aspects such as cost–benefit requires decision-making tools. This study was assessing the cost–benefit of plastic solid waste management by development of an economic model, and definition of different scenarios to change plastic solid waste management status. The results showed that 8971 tons of plastic solid waste were generated annually in the studied city. The plastic solid wastes were finally transferred to either recycling or landfilling site through 5 identified routes. 83 percent of the total recycled plastic solid waste was due to post-separation routes, and only 7.7 percent of the total plastic solid waste was recycled from the source separation route. The economic comparison of scenarios showed that with the aggregation of post-separation routes, the net revenue of plastic solid waste management increases by 334,000 euro per year while increasing the public participation and the ratio of source separation route raises net revenue by 875,000 euro per year, which was the best economic condition among the scenarios. Using life cycle cost method and it’s respected developed economic model truly satisfied the conditions of both, the current plastic solid waste management and the alternative scenarios, and hence can be adopted as a tool for decision-making.

     

Household waste behaviours among a community sample in Iran: An application of the theory of planned behaviour

Understanding the factors influencing recycling behaviour can lead to better and more effective recycling programs in a community. The goal of this study was to examine factors associated with household waste behaviours in the context of the theory of planned behaviour (TPB) among a community sample of Iranians that included data collection at time 1 and at follow-up one year later at time 2. Study participants were sampled from households under the coverage of eight urban health centers in the city of Qazvin. Of 2000 invited households, 1782 agreed to participate in the study. A self-reported questionnaire was used for assessing socio-demographic factors and the TPB constructs (i.e. attitude, subjective norms, perceived behavioural control, and intention). Furthermore, questions regarding moral obligation, self-identity, action planning, and past recycling behaviour were asked, creating an extended TPB. At time 2, participants were asked to complete a follow-up questionnaire on self-reported recycling behaviours. All TPB constructs had positive and significant correlations with each other. Recycling behaviour at time 1 (past behaviour) significantly related to household waste behaviour at time 2. The extended TPB explained 47% of the variance in household waste behaviour at time 2. Attitude, perceived behavioural control, intention, moral obligation, self-identity, action planning, and past recycling behaviour were significant predictors of household waste behaviour at time 2 in all models. The fact that the expanded TPB constructs significantly predicted household waste behaviours holds great promise for developing effective public campaigns and behaviour-changing interventions in a region where overall rates of household waste reduction behaviours are low. Our results indicate that educational materials which target moral obligation and action planning may be particularly effective.