Drinking Water Purification Research Articles

Safe purification of rural drinking water by biological aerated filter coupled with ultrafiltration

Water resources of many rural areas are usually lakes or reservoirs, which can be easily affected by run-off, non-point source pollution and are often of poorer quality compared with urban water sources. Drinking water supply in remote rural areas usually suffers from various challenges, such as the high cost of construction and maintenance of centralized drinking water treatment plants and pipe networks, due to the dispersed nature of villages, which are often located in varied and complex topographies. In this study, a combined process comprising biological aerated filter (BAF) combined with ultrafiltration was developed to treat polluted reservoir water. Organic matter indexes, turbidity, and chroma were used as indicators for the evaluation of the system performance. In a long-term experiment lasting 260 days, the combined process was tested under different values of critical operational parameters, including filler types and empty bed contact time (EBCT). Furthermore, the microbial communities in different BAF reactors were carefully evaluated at different times, finding that microorganisms with specific functions were enriched in the various BAF reactors. The combined process reached 85.5 % removal rate of DOC with an EBCT of 45 min and using granule active carbon (GAC) as filler. Most of the effluents of BAF reactors met the requirements for drinking water in China. The combined system showed practical potential for polluted water treatment in some rural areas.

A novel post coordination modulation method to synthesize N/S functionalized ZIF-8 for removal of trace heavy metals from drinking water

The functionalization of metal–organic frameworks (MOFs) has been considered an effective strategy for promoting heavy metals removal from water. Therefore, a novel post coordination modulation method was systematically studied to synthesize ZIF-8 functionalized by 2,5-Dimercapto-1,3,4-thiadiazole (Post-ZIF-8-DMTD) for trace heavy metals removal from drinking water. The effects of addition time and addition amount of DMTD on the structure and adsorption performance of Post-ZIF-8-DMTD were investigated. It was found that addition time of DMTD had minor impact, while addition amount of DMTD had great impact, appropriate DMTD addition amount (375 mg) could not only provide sufficient active sites but also avoid self-polymerization of DMTD. Post-ZIF-8-DMTD exhibited a more regular structure than Before-ZIF-8-DMTD synthesized by direct coordination of mim and DMTD with Zn2+, and had faster adsorption rate and deeper purification capability for trace Pb(II). Post-ZIF-8-DMTD also exhibited good stability, wide suitable pH range, high maximum adsorption capacity (4.34 mg/g) that met WHO effluent Pb(II) concentration standard and excellent capture capacity for many trace heavy metals in tap water, and could be regenerated effectively with thiourea solution. The post coordination modulation method provides a novel and efficient strategy for the functionalization of MOFs, and Post-ZIF-8-DMTD has excellent application prospects in drinking water purification.

Methodology for calculating the design parameters of thin-layer modules during reconstruction and use in existing structures

This article presents a method for using thin-layer sedimentation tanks in horizontal sedimentation tanks in the process of drinking water purification. The basic requirements and methods for using thin-layer sedimentation tanks are presented. The role of thin-layer sedimentation tanks in accelerating the process of softening drinking water is great. When making recommendations, conclusions are drawn based on the results obtained on a laboratory instrument. The recommendations can be used both for existing settling tanks and for newly developed settling tanks.

Phosphate functionalized activated carbon sachet filters for drinking water purification

This study reports the synthesis and characterization of a phosphate functionalized porous activated carbon filter material suitable for sachet filters to remove fluoride, hardness and bacterial pathogens in drinking water.

Проектное обучение и кейс-технологии: подготовка специалиста-агроинженера на курсе химии

The requirements for the level of theoretical and practical knowledge and skills of agricultural specialists are increasing every year. Chemical subjects form the basis of natural science education of future agricultural specialists. To improve the effectiveness of the educational process, the practice of teaching introduces many different teaching methods. The authors analyzed didactic opportunities of project-based learning and case technology n the context of methodological psychological and pedagogical concepts, in particular, the structure of activity and the logic of personality development. It is established that these methods used in the teaching of chemistry activate all the components of the structure of learning activity: cognitive, value-oriented, communicative, transformative, physical, and aesthetic. The article outlines the ways of using project-based learning and case technologies in the study of chemical subjects by agricultural engineering students. Given as an example is a case study on determining the quality of drinking water by titrimetric and potentiometric analysis methods and selection of a household filter for drinking water purification. The authors dwell on the methodology of performing tasks and define the criteria for evaluating the learning outcomes. Project-based learning and case technologies should meet a number of requirements, have a system of evaluation criteria, certain goals and practice-oriented task, which will enable and motivate students to solve practical problems in their future professional activities.

A cross-reactive plasmonic sensing array for drinking water assessment

The continuous monitoring of remote drinking water purification systems is a global challenge with direct consequences for human and environmental health. Nanoplasmonic sensors can monitor treatment systems and warn of failures.

Development of lignocellulosic biomass derived Cu and Zn doped highly porous activated carbon and its utilization in the anti-microbial treatment

A detailed study has been carried out to develop a process which can yield highly porous activated carbons from lignocellulosic biomasses and check the antimicrobial properties by doping with metals such as Cu and Zn. According to the availability of the waste biomasses in the Indian subcontinent especially in the North-Eastern region which is considered a biomass hotpot, activated carbon samples were prepared using rubber wood sawdust, ramie fibre and areca husk as they are available in plenty. The activated carbons were prepared using a modified thermo-chemical treatment at different temperatures and activation time to increase the surface area of the activated carbon samples which was found to be in the range of 346–1998 m2/g. The activated carbon samples were found to have thereby exhibited good antimicrobial activity against E.coli on the incorporation of suitable metals such as Cu and Zn into the highly porous carbon matrix. The activated carbon samples which were prepared at 700 °C using rubber wood sawdust and areca fibres reported a better bactericidal effect ranging between 75 and 93.5% against the carbon dosages ranging between 10 and 20 g/L of water samples containing E. coli. The antimicrobial killings were confirmed through the minimum inhibitory concentration (MIC) process by using UV Visible Spectroscopy. Various analytical methods such as DSC, FTIR, BET and FESEM-EDX etc. were applied to describe the properties of the samples. This study will give more information about the utilization of activated carbons for drinking water purification purposes.

Synthesis and structural characterization of copper nanoparticles doped activated carbon derived from coconut coir for drinking water purification

Modifying and functionalizing activated carbon using metal nanoparticles have received great scientific attention in recent decades as a method to improve its inherent properties. The synergistic effects between the dopant and the activated carbon could lead to advanced properties in the hybrid material compared to individual counterparts. In this study, copper-doped activated carbon from coconut coir (Cu-ACC) is synthesized by an in-situ reduction method. The successful doping of zerovalent copper nanoparticles (Cu np) into the activated carbon matrix was confirmed using several characterization techniques. Peaks related to zerovalent Cu np in the X-ray diffractogram confirmed the successful formation of zerovalent Cu np. The dopant-matrix interactions were confirmed through peak shifts in the Fourier Transform Infrared Spectroscopy and D and G band changes in the Raman spectrum of Cu-ACC. The Cu 2p band in XPS of the Cu-ACC showed a sharp doublet at 932.7 eV, confirming the presence of metallic Cu. As indicated in the TEM/SEM images, Cu np demonstrated a spherical morphology with an average diameter of 5 nm. It was further observed that the Cu-ACC nanohybrid material could remove fluoride (63%) and hardness (69%) in synthetic water. Cu-ACC further demonstrates an enhanced antimicrobial activity against three commonly found water pathogens; E. coli, S. typhi, and S. flexneri. The material is expected to be used in next-generation domestic water filters formulated as single-use sachet bags.

Removal Performances of Turbidity, Organics, and NH4+-N in a Modified Settling Tank with Rotating Biological Discs Used for Enhancing Drinking Water Purification

In this study, a modified horizontal settling tank with rotating biological discs was developed to treat slightly polluted surface water, and its performance on the simultaneous removal of turbidity, organics, and NH4+-N was investigated on a lab scale. Results show that the effluent quality of the modified settling tank is stable in more than two months of continuous operation. At a hydraulic retention time (HRT) of 2.0 h, 73.65 ± 5.15% turbidity, 53.98 ± 5.17% TOC, and 77.01 ± 10.02%, NH4+-N could be removed by the modified settling tank with an average of 1.96 NTU turbidity, 1.98 mg/L TOC, and 0.46 mg/L NH4+-N residue in the effluent. Due to the improvement in DO supply, higher removal efficiencies of both organics and NH4+-N were achieved with increased disc rotating speed (r < 4 r/min). Further study showed that the genus Hyphomicrobium dominant on the posterior discs and the genus Nitrospira dominant on the anterior discs mainly contributed to the enhanced bio-oxidation of organics and NH4+-N, respectively.

Impact of UV-C Irradiation on Bacterial Disinfection in a Drinking Water Purification System.

The supply of microbiological risk-free water is essential to keep food safety and public hygiene. And removal, inactivation, and destruction of microorganisms in drinking water are key for ensuring safety in the food industry. Ultraviolet-C (UV-C) irradiation is an attractive method for efficient disinfection of water without generating toxicity and adversely affecting human health. In this study, the disinfection efficiencies of UV-C irradiation on Shigella flexneri (Gram negative) and Listeria monocytogenes (Gram positive) at various concentrations in drinking water were evaluated using a water purifier. Their morphological and physiological characteristics after UV-C irradiation were observed using fluorescence microscopy and flow cytometry combined with live/dead staining. UV-C irradiation (254 nm wavelength, irradiation dose: 40 mJ/cm2) at a water flow velocity of 3.4 L/min showed disinfection ability on both bacteria up to 108 CFU/4 L. And flow cytometric analysis showed different physiological shift between S. flexneri and L. monocytogenes after UV-C irradiation, but no significant shift of morphology in both bacteria. In addition, each bacterium revealed different characteristics with time-course observation after UV-C irradiation: L. monocytogenes dramatically changed its physiological feature and seemed to reach maximum damage at 4 h and then recovered, whereas S. flexneri seemed to gradually die over time. This study revealed that UV-C irradiation of water purifiers is effective in disinfecting microbial contaminants in drinking water and provides basic information on bacterial features/responses after UV-C irradiation.

Current Challenges for Biological Treatment of Pharmaceutical-Based Contaminants with Oxidoreductase Enzymes: Immobilization Processes, Real Aqueous Matrices and Hybrid Techniques.

The worldwide access to pharmaceuticals and their continuous release into the environment have raised a serious global concern. Pharmaceuticals remain active even at low concentrations, therefore their occurrence in waterbodies may lead to successive deterioration of water quality with adverse impacts on the ecosystem and human health. To address this challenge, there is currently an evolving trend toward the search for effective methods to ensure efficient purification of both drinking water and wastewater. Biocatalytic transformation of pharmaceuticals using oxidoreductase enzymes, such as peroxidase and laccase, is a promising environmentally friendly solution for water treatment, where fungal species have been used as preferred producers due to their ligninolytic enzymatic systems. Enzyme-catalyzed degradation can transform micropollutants into more bioavailable or even innocuous products. Enzyme immobilization on a carrier generally increases its stability and catalytic performance, allowing its reuse, being a promising approach to ensure applicability to an industrial scale process. Moreover, coupling biocatalytic processes to other treatment technologies have been revealed to be an effective approach to achieve the complete removal of pharmaceuticals. This review updates the state-of-the-art of the application of oxidoreductases enzymes, namely laccase, to degrade pharmaceuticals from spiked water and real wastewater. Moreover, the advances concerning the techniques used for enzyme immobilization, the operation in bioreactors, the use of redox mediators, the application of hybrid techniques, as well as the discussion of transformation mechanisms and ending toxicity, are addressed.

Self-Powered Water Disinfection System Acheving a Novel Oxidation-Assisted Electroporation Mechansim with Rotational Triboelectric Nanogenerator

In world, one of three people lack reliable access to clean water and water-borne diseases resulting from pathogenic microbescontaminated water remain a great threat to public health. Disinfection is an effective drinking water purification method; however, the most commonly used water disinfection method, chlorination, is limited by carcinogenic disinfection byproducts formation. Alternative methods such as ultraviolet (UV) radiation and membrane filtration suffer from drawbacks such as pathogen regrowth, low throughput, and intensive energy/chemical consumption. In addition, the methods have a limited disinfecting capacity and may be inadequate during a crisis like in cases of a severe epidemic outbreak, such as coronavirus disease 2019. Here, we report a rapid, self-powered water disinfection system for both bacterial and viral inactivation based on a novel oxidation-assisted electroporation mechanism powered by a supercoiling-mediated rotational TENG (S-TENG) that converts the periodic hand stretching/releasing into high-speed rotation. Owing to a rational design of the S-TENG that yields an ultrafast rotation (≈7500 rpm), we successfully overcame the insufficient output limitations of TENG caused by the low-frequency stimuli ambient energy harvesting. The S-TENG with sufficient voltage and current output can generate an NW-enhanced localized electric field and oxidative species simultaneously, and therefore achieving high disinfection efficiency. More than 99.9999% of bacteria and viruses were inactivated at a high flux of 15 m3 h–1 m–2. Our work presented an efficient enlarged demonstrator wherein 1 L of natural water can flow through the whole system within 1 min solely driven by gravity, and achieve complete disinfection, confirming the feasibility of this method for water disinfection in areas with an inadequate power supply. Figure 1

Chemical Analysis of Drink Water Samples for some Water Purification and Treatment Stations in El-Beida City - Libya and Compared with Residential and Mineral Water

This study was conducted in the city of El-Beida-Libya on different samples from 11 drinking water purification and treatment stations, compared with the source water (residential water) and some of the most popular mineral water samples in the Libyan local markets. During this work, a number of chemical properties of the studied samples were examined, such as pH, Electric Conductivity (EC) (µS/cm),Total Dissolved Solids (TDS) (mg/l), Alkalinity (as HCO3-) (mg/l), Total Hardness (TH) (mg/l), Ca++(mg/l), Mg++ (mg/l), Na+(mg/l), K+ (mg/l), Cl- (mg/l) and NO3- (mg/l). The results obtained in the current study indicate that there are variation among stations. Whereas the pH values were ranged between (5.99 - 7.48), EC values were ranged (10.03 – 590 µS/cm), TDS values were ranged (5 - 283.33), Alkalinity (as HCO3-) values were ranged (44.73- 390.40 mg/l), Total hardness values were ranged (8.01-248.20 mg/l), Ca++ values were ranged (3.2-99.42 mg/l), Mg++ (1.92-59.52 mg/l), Na+ (1.92-23.24 mg/l), K+ (0.03-1.95 mg/l), Cl- (9.46-56.74 mg/l) and NO3- (6.33-12.17 mg/l). Most of the parameters analyzed in this study were within the guidelines given by the World Health Organization (WHO) and the Libyan National Centre for Standardization and Metrology ( LNCSM) for drinking water while few others were not. Overall, the water from all the locations was found to be safe as drinking water except for the sample number S8 (Al Nabaa for drinking water purification and treatment), which is considered poor quality in terms of chemical properties specifications.

POROSITY, PERMEABILITY AND TORTUOSITY RELATIONSHIP IN BINARY SPHERICAL PARTICALS

The complexity of processes in industry, which involved the formation of granular beds, has limited information about permeability (k), which is directly related with packing porosity ε and tortuosity T. For an understanding of the relationship between k, ε and T in mixed beds of particles that are different in size, simplified porous media model of binary mixture of spheres have been. A continuous function relating the porosity of a mixture (ε) with the volume fraction (xD) of binary mixture has been established. The incorporation of the proposed porosity model into the conventional Kozeny-Carmen equation gives a good agreement between the measured and predicted permeability vs.xD. Based on this relation and on the dependence of ε vs.xD, a model predicted tortuosity and permeability was obtained, having demonstrated that the tortuosity may significantly alter the permeability of a mixed bed. This search is useful for transport phenomena analysis in granular beds as well as in engineering applications, such as deep bed filtration used for drinking water purification.

Research on Autopsy Results of over 10 Year Old Low Pressure Hollow Fiber Membrane from Domestic Water Treatment Plant

Objectives : In this study, membrane autopsy was performed for a parallel arrayed low-pressure membrane (microfiltration) filtration process that is actually applied to water treatment, to check out whether there are differences in the degree of membrane fouling due to the uneven flow rate into each module. Also, membrane foulants were evaluated quantitatively.Methods : In this study, autopsy was performed for over 10 year old membranes used for drinking water purification. In this way, the outer casings of membrane modules at different positions were disassembled and visually observed. In addition, In addition, the size of the pores and the porosity were investigated by taking a SEM (Scanning Electron Microscope) photograph for the new and the used membrane module fiber samples in different positions from the header pipe. The used membrane foulants were classified into organic and inorganic matters and quantitatively analyzed.Results and Discussion : As a result of visually observing inside the membrane module that has produced drinking water for over 10 years, the inside of the No. 1 membrane module close to the inlet was contaminated with black foulants. On the other hand, in the case of No. 10 membrane module located farthest from the header pipe inlet, no foulants were observed with the naked eye. Also, it was observed from SEM photograph results that there were large differences in the surfaces among No. 1, 4, 6, 8 and 10 MF module fibers.Conclusion : Even after periodic physical and chemical cleaning, it was concluded that the fouling levels were different each other in the parallel arrayed low-pressure membrane modules. In addition, the pore size distribution and porosities of the membrane modules may vary depending on the position.

DNA Barcoding of Chironomid Larvae (Diptera: Chironomidae) from Large Rivers in South Korea to Facilitate Freshwater Biomonitoring and Public Health Surveillance.

Chironomid larvae are among the dominant benthic macroinvertebrates in all types of water systems in South Korea. They may pass through pipes in rivers (raw water) and occur in drinking water, thus creating public health issues. However, little is known about the larval stages of chironomids in large South Korean rivers. Therefore, we examined larval–adult associations in chironomids inhabiting major rivers used as water sources. The larvae were collected in 2015 and 2016 from nine locations along the four largest rivers in South Korea using a Ponar grab. Cytochrome oxidase subunit I (COI) sequences were generated from the larval specimens, and the species were identified by comparing these sequences to those in a newly constructed DNA barcode library of Chironomidae in South Korea. The samples from the four rivers yielded 61 mitochondrial COI sequences belonging to 18 species, including Hydrobaenus kondoi Saether, 1989, which was reported for the first time in the Korean Peninsula. Further, morphological identification of the larvae was conducted, and a pictorial taxonomic key to Chironomidae species in large rivers in South Korea was developed to facilitate freshwater biomonitoring research. Finally, an action flow chart was created for the rapid identification of chironomid larvae in infested drinking water or water purification facilities.

Characterizing Groundwater Turbidity Reduction by Using a Magnetic Biocarbon Adsorbent Composite (MBAC): Process Optimization

The usage of groundwater as drinking water source in many parts of Kelantan encourages the research and development of various cost-effective alternative adsorbent material for turbidity reduction and drinking water purification. The preparation, characterization, and use of a magnetic biocarbon adsorbent composite (MBAC) is introduced in this study as an option to treat turbid groundwater. In contrast to commercial activated carbon (CAC), peak shifts and peaks denoting Fe-O bending were observed in the FTIR spectrum of MBAC. The adsorption process for turbidity reduction by MBAC and CAC was investigated. A factorial design matrix consisting of four parameters were tabulated, namely, adsorbent dosage (0.02, 0.04, and 0.06 g), agitation time (15, 30, and 60 min), agitation rate (150, 200, and 250 rpm), and two adsorbent particle size ranges (M: 300 < x ≤ 500, and Q: ≤ 45 μm). The predictive model was validated with 0.04 g MBAC of ≤ 45 μm in particle size, agitated at 150 rpm, for 48 min, that attained 98.46% turbidity removal efficiency with a final NTU reading of 0.40. Conversely, CAC removed 88.19% for a final NTU reading of 3.07. Overall, the iron oxide impregnated biocarbon composite showed better turbidity reduction capability compared to CAC. The findings of this work support the potential application of MBAC as an alternative adsorbent for the treatment of groundwater sourced drinking water.

Mechanical performance and phase analysis of an eco-friendly alkali-activated binder made with sludge waste and blast-furnace slag

A new eco-friendly alkali-activated material (AAM) using two waste materials, including drinking water treatment sludge (DWTS) and ground granulated blast furnace slag (GGBFS), was developed in this study. DWTS is a by-product generated from drinking water purification processes. Using DWTS and GGBFS to manufacture alkali-activated binder to replace cement provides an economical engineering solution for these industrial wastes and alleviates adverse environmental effects of cement production. In this study, the workability, mechanical performance, durability, and microstructure properties of AAM-derived mortar were evaluated with different DWTS/GGBFS proportions and sodium silicate (SS) to sodium hydroxide (SH) ratios. Moreover, this study investigated the formation of hybrid tobermorite-like C-(A)-S-H and zeolite-like N-A-S-H phases on different mixtures. The results showed that mortar samples made with AAM containing the DWTS/GGBFS ratio of 40/60 and SS/SH ratio of 1.5 had the highest compressive strength (67 MPa). The porosity results analysed using mercury intrusion porosimetry showed that 40% DWTS contents could refine pore structure and promote geopolymerisation. The x-ray diffraction pattern and Fourier-transform infrared spectroscopy identified the hybrid C-(A)-S-H and N-A-S-H phases. The element analysis on the AAM matrix using the energy-dispersive x-ray spectroscopy technique demonstrated that the co-existence of these two phases could improve the mechanical performance and microstructure. In addition, the results obtained from backscattered electron images showed that excessive alumina in the samples with more than 60% DWTS might lead to an incomplete reaction and a porous gel structure.

Preparation of activated carbon fibers rich in S/N/O adsorption sites for selective and efficient trace Pb(II) removal from drinking water

Selective and efficient removal of trace heavy metals from drinking water has been a challenging problem. Herein, we report novel activated carbon fibers rich in S/N/O multiple active sites (ACF-S/N/O) obtained by hydrogen peroxide pretreatment and 2,5-dimercapto-1,3,4-thiadiazole (DMTD) post-functionalization. The coexistence of -SH, =N-, -NH-, -NH2, -COOH and -OH functional groups in ACF-S/N/O greatly increased adsorption performance and selectivity for trace lead. The adsorbent prepared at optimum nominal mass ratio (9:11) of ACFs pretreated by hydrogen peroxide (ACF-O) to DMTD represented excellent and selective adsorption behavior for trace lead, and maximum adsorption capacity which effluent concentration met World Health Organization (WHO) standard attained 29.05 mg g−1, which was far above those of previously reported materials. Moreover, the adsorbent also exhibited rapid adsorption dynamics, superior selectivity for trace lead, and excellent adsorption performance under broad pH and concentration range, as well as in tap water. The adsorption data were well fitted to Freundlich and D-R isotherm models and pseudo-second-order kinetic model, respectively, suggesting chemical adsorption mechanism. The abundant S/N/O active sites greatly overcame mass transfer resistance of trace lead and promoted the chelation between the adsorption site and trace lead, making adsorbent exhibit excellent application prospects for drinking water purification.

Reclaimable MoS2 Sponge Absorbent for Drinking Water Purification Driven by Solar Energy.

With the fast development of modern industries, scarcity of freshwater resources caused by heavy metal pollution (i.e., Hg2+) has become a severe issue for human beings. Herein, a 3D-MoS2 sponge as an excellent absorbent is fabricated for mercury removal due to its multidimensional adsorption pathways, which decreases the biomagnification effect of methylmercury in water bodies. Furthermore, a secondary water purification strategy is employed to harvest drinkable water with the exhausted adsorbents, thus alleviating the crisis of drinking water shortage. Compared to the conventional landfill treatment, the exhausted MoS2 sponge absorbents are further functionalized with a poly(ethylene glycol) (PEG) layer to prevent the heavy metals from leaking and enhance the hydrophilicity for photothermal conversion. The fabricated evaporator displays excellent evaporation rates of ∼1.45 kg m-2 h-1 under sunlight irradiation and produces freshwater with Hg2+ under the WHO drinking water standard at 0.001 mg L-1. These results not only assist in avoiding the biodeposition effect of mercury in water but also provide an environment-friendly strategy to recycle hazardous adsorbents for water purification.