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1.
Water Res ; 203: 117550, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34418646

RESUMO

One of the main purposes of drinking water treatment is to reduce turbidity originating from clay particles. Relatively little is known about the removal of other types of particles, including conventionally sized powdered activated carbon (PAC) and superfine PAC (SPAC), which are intentionally added during the treatment process; microplastic particles; and viruses. To address this knowledge gap, we conducted a preliminary investigation in full-scale water treatment plants and then studied the removal of these particles during coagulation-flocculation, sedimentation, and rapid sand filtration (CSF) in bench-scale experiments in which these particles were present together. Numbers of all target particles were greatly decreased by coagulation-flocculation and sedimentation (CS). Subsequent rapid sand filtration greatly reduced the concentrations of PAC and SPAC but not the concentrations of viruses, microplastic particles, and clay particles. Overall removal rates by CSF were 4.6 logs for PAC and SPAC, 3.5 logs for viruses, 2.9 logs for microplastics, and 2.8 logs for clay. The differences in removals were not explained by particle sizes or zeta potentials. However, for clays, PAC and SPAC, for which the particle size distributions were wide, smaller particles were less efficiently removed. The ratios of both clay to PAC and clay to SPAC particles increased greatly after rapid sand filtration because removal rates of PAC and SPAC particles were about 2 logs higher than removal rates of clay particles. The trend of greater reduction of PAC concentrations than turbidity was confirmed by measurements made in 14 full-scale water purification plants in which residual concentrations of PAC in treated water were very low, 40-200 particles/mL. Clay particles therefore accounted for most of the turbidity in sand filtrate, even though PAC was employed. The removal rate of microplastic particles was comparable to that of clays. Sufficient turbidity removal would therefore provide comparable removal of microplastics. We investigated the effect of mechanical/photochemical weathering on the removal of microplastics via CSF. Photochemical weathering caused a small increment in the removal rate of microplastics during CS but a small reduction in the removal rate of microplastics during rapid sand filtration; mechanical weathering decreased the removal rate via CS but increased the removal rate via rapid sand filtration. The changes of removal of microplastics might have been caused by changes of their zeta potential.


Assuntos
Vírus , Purificação da Água , Bentonita , Carvão Vegetal , Argila , Filtração , Floculação , Caulim , Microplásticos , Plásticos , Areia
2.
Water Res ; 202: 117467, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34371390

RESUMO

Stabilization of urine with calcium hydroxide prevents enzymatic urea hydrolysis, thus allowing for maximum nitrogen recovery. The process also produces a calcium phosphate bi-product which has value as a fertilizer. However, the treated solution is saturated with calcium that could ultimately result in calcium carbonate scaling of reverse osmosis membranes during urine concentration. This would result in a decrease in maximum water removal and an increase in operational costs. This study therefore investigated if bubbling air and carbon dioxide through stabilized urine could remove calcium ions as calcium carbonate. The process was modelled to better understand the mechanisms controlling the reactions in the process. The model was then used to determine the most cost and time efficient operating conditions. Calcium removal of between 85-98% was achieved at air flow rates of 1.5 to 9 L min-1. Increasing the CO2 concentration from 0.04% (air) to 1% decreased the reaction time from 20.5 h to 2.5 h but the cost of CO2 outweighed the shorter operating time. Air bubbling was the more cost-efficient option. It was estimated that 95% of the calcium could be removed in 7.6 h at an air flow rate of 4 L min-1 L-1 of urine and at a cost of $0.65 m-3. It was also determined that even if the pH decreased to below 11, the urine remained stabilized and no enzymatic urea hydrolysis occurred.


Assuntos
Cálcio , Dióxido de Carbono , Carbonato de Cálcio , Filtração , Humanos , Nitrogênio
3.
Environ Sci Technol ; 55(16): 11348-11359, 2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34342439

RESUMO

Predictive models for micropollutant removal by membrane separation are highly desirable for the design and selection of appropriate membranes. While machine learning (ML) models have been applied for such purposes, their reliability might be compromised by data leakage due to inappropriate data splitting. More importantly, whether ML models can truly understand the mechanisms of membrane separation has not been revealed. In this study, we evaluate the capability of the XGBoost model to predict micropollutant removal efficiencies of reverse osmosis and nanofiltration membranes. Our results demonstrate that data leakage leads to falsely high prediction accuracy. By utilizing a model interpretation method based on the cooperative game theory, we test the knowledge of XGBoost on the mechanisms of membrane separation via quantifying the contributions of input variables to the model predictions. We reveal that XGBoost possesses an adequate understanding of size exclusion, but its knowledge of electrostatic interactions and adsorption is limited. Our findings suggest that future work should focus more on avoiding data leakage and evaluating the mechanistic knowledge of ML models. In addition, high-quality data from more diverse experimental conditions, as well as more informative variables, are needed to improve the accuracy of ML models for predicting membrane performance.


Assuntos
Purificação da Água , Filtração , Aprendizado de Máquina , Membranas Artificiais , Osmose , Reprodutibilidade dos Testes
4.
Artigo em Inglês | MEDLINE | ID: mdl-34360199

RESUMO

The coronavirus disease (COVID-19) pandemic is a global health threat and has posed a challenge for society and social care services as well as healthcare systems. Due to the risks involved in being exposed to the virus, public health actions such as wearing masks and physical distancing are necessary to reduce its spread. However, using non-validated masks is a serious issue as such masks may provide inadequate protection against airborne bioaerosol transmission, resulting in the spread of the virus. Therefore, it is necessary to evaluate the filtering performances of the masks against bioaerosols as well as particulate matter (PM). Here, we evaluated the filtering performances of sixteen different masks (four brands each of woven, antidroplet, KF80, and KF94 masks) commercially available in Korea with high market shares. As a simulation of being exposed to bioaerosols and to the yellow dust commonly found in Korea, the filtration efficiency levels of the masks were tested against airborne bacteria-containing droplets and against fine dusts of different ranges of particle sizes. Their filtration efficiency levels against the droplets showed strong positive correlations, specifically Pearson correlation coefficient r values of 0.917, 0.905, and 0.894, with their efficiency levels against PM1.0, PM2.5, and PM10, respectively. The results of this study should be useful for choosing appropriate masks, including those that meet filtering performance requirements.


Assuntos
COVID-19 , Bactérias , Filtração , Humanos , Tamanho da Partícula , República da Coreia , SARS-CoV-2
5.
Artigo em Inglês | MEDLINE | ID: mdl-34360450

RESUMO

Filtering facepiece respirators (FFR) with anti-odor properties are used to reduce odor nuisance occurring both in everyday life and at workplaces. Unfortunately, there are no standardized methods to measure the efficiency of odor reduction of such personal protective devices. This paper aims to determine whether olfactometric-based methods, commonly used in environmental studies, can be employed for this purpose. The proposed procedure is based on the detection of n-butanol by study participants, and it consists of three subsequent stages: (i) defining the individual levels of odor sensitivity of each study participant; (ii) determining THE odor detection level while using FFRs with varying anti-odor properties; and (iii) completing a questionnaire concerning the subjective perceptions of study participants. As a measure of odor reduction efficiency, a coefficient W, defined as a quotient of the degree of odor reduction by the FFR, and the individual odor sensitivity of the subject, was proposed. The experimental results showed the ability of our measure to differentiate the effectiveness of odor reduction of tested FFRs. This indicates that it can be potentially employed as the assessment tool to confirm the effectiveness of such respiratory protective devices as a control measure mitigating the adverse effects of malodors on workers' health, cognition, and behavior.


Assuntos
Exposição Ocupacional , Dispositivos de Proteção Respiratória , Carvão Vegetal , Filtração , Humanos , Exposição Ocupacional/análise , Odorantes , Olfatometria , Ventiladores Mecânicos
6.
Chemosphere ; 277: 130244, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34384173

RESUMO

The recovery and utilization of organic matter in municipal wastewater are essential for the establishment of a sustainable society, such that these factors have drawn significant recent attention. The up-concentration of organic matter via direct membrane filtration (DMF), followed by anaerobic digestion, is advantageous over the treatment of the entire wastewater by an anaerobic process, such as an anaerobic membrane bioreactor (AnMBR). However, the occurrence of severe membrane fouling in the DMF is a problem. In this study, DMF was carried out at an existing wastewater treatment plant to attempt long-term operation. A combination of vibration of membrane modules, short-term aeration, and chemically enhanced backwash (CEB), with multiple chemicals (i.e., the alternative use of citric acid and NaClO), was found to be effective for the mitigation of membrane fouling in DMF. Furthermore, switching the feed from influents to effluents in the primary sedimentation basin significantly mitigated membrane fouling. In this study, in which microfiltration membrane, with a nominal pore size of 0.1 µm, was used, ∼75% of the organic matter in raw wastewater was recovered, with the volumetric concentration of wastewater by 50- or 150-fold. Organic matter recovered by DMF had significantly higher potentials for biogas production than the excess sludge generated from the same wastewater treatment plant. An analysis of the energy balance (i.e., the energy used for DMF and recovered by DMF) suggests that the proposed DMF can produce a net-positive amount of electricity of ∼0.3 kWh from 1 m3 of raw wastewater with a typical strength (chemical oxygen demand of 500 mg/L).


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Anaerobiose , Reatores Biológicos , Filtração , Membranas Artificiais , Esgotos
7.
Environ Sci Technol ; 55(15): 10714-10723, 2021 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-34269563

RESUMO

Minimum and zero liquid discharge (MLD/ZLD) are emerging brine management strategies that attract heightened attention. Although conventional reverse osmosis (RO) can improve the energy efficiency of MLD/ZLD processes, its application is limited by the maximum hydraulic pressure (ΔPmax) that can be applied in current membrane modules. To overcome such limitation, novel RO-based technologies, including osmotically assisted RO (OARO) and low-salt-rejection RO (LSRRO), have been proposed. Herein, we utilize process modeling to systematically compare the energy consumption of OARO and LSRRO for MLD/ZLD applications. Our modeling results show that the specific energy consumption (SEC) of LSRRO is lower (by up to ∼30%) than that of OARO for concentrating moderately saline feed waters (<∼35,000 mg/L TDS) to meet MLD/ZLD goals, whereas the SEC of OARO is lower (by up to ∼40%) than that of LSSRO for concentrating higher salinity feed waters (>∼70,000 mg/L TDS). However, by implementing more stages and/or an elevated ΔPmax, LSRRO has the potential to outperform OARO energetically for treating high-salinity feed waters. Notably, the SEC of both OARO and LSRRO could be 50% lower than that of mechanical vapor compressor, the commonly used brine concentrator in MLD/ZLD applications. We conclude with a discussion on the practicability of OARO and LSRRO based on membrane module availability and capital cost, suggesting that LSRRO could potentially be more feasible than OARO.


Assuntos
Purificação da Água , Filtração , Membranas Artificiais , Osmose , Sais
8.
J Dairy Sci ; 104(9): 9478-9493, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34218910

RESUMO

Extracellular vesicles (EV) in milk, particularly exosomes, have attracted considerable attention as bioactive food compounds and for their use in drug delivery. The utility of small EV in milk (sMEV) as an animal feed additive and in drug delivery would be enhanced by cost-effective large-scale protocols for the enrichment of sMEV from byproducts in dairy plants. Here, we tested the hypothesis that sMEV may be enriched from byproducts of cheesemaking by tangential flow filtration (EV-FF) and that the sMEV have properties similar to sMEV prepared by ultracentrifugation (sMEV-UC). Three fractions of EV were purified from the whey fraction of cottage cheese making by using EV-FF that passed through a membrane with a 50-kDa cutoff (50 penetrate; 50P), and subfractions of 50P that were retained (100 retentate; 100R) or passed through (100 penetrate; 100P) a membrane with a 100-kDa cutoff; sMEV-UC controls were prepared by serial ultracentrifugation. The abundance of sMEV (<200 nm) was less than 0.3% in EV-FF compared with sMEV-UC (1012/mL of milk). Despite the low EV count, the protein content (mg/mL) of 100R (63 ± 0.02; ± standard deviation) was higher than that of 50P (0.75 ± 0.10), 100P (0.65 ± 0.40), and sMEV-UC (27 ± 0.02). There were 17, 14, 35, and 75 distinct proteins detected by nontargeted mass spectrometry analysis in 50P, 100R, 100P, and sMEV-UC, respectively. Exosome markers CD9, CD63, CD81, HSP-70, PDCD6IP, and TSG101 were detected in control sMEV-UC but not in EV-FF by using targeted mass spectrometry and immunoblot analyses. Negative exosome markers, APOB, ß-integrin, and histone H3 were below the limit of detection in EV-FF and control sMEV-UC analyzed by immunoblotting. The abundance of the major milk fat globule protein butyrophilin showed the following pattern: 100R ≫ 100P = 50P > sMEV-UC. More than 100 mature microRNA were detected in sMEV-UC by using sequencing analysis, compared with 36 to 60 microRNA in EV-FF. Only 100R and sMEV-UC yielded mRNA in quantities and qualities sufficient for sequencing analysis; an average of 276,000 and 838,000 reads were mapped to approximately 14,600 and 18,500 genes in 100R and sMEV-UC, respectively. In principal component analysis, microRNA, mRNA, and protein in EV-FF preparations clustered separately from control sMEV-UC. We conclude that under the conditions used here, flow filtration yields a heterogeneous population of milk EV.


Assuntos
Queijo , Exossomos , Vesículas Extracelulares , Nanopartículas , Animais , Filtração , Ultracentrifugação
9.
Ultrason Sonochem ; 77: 105668, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34298307

RESUMO

To extend the shelf life and retain bioactive proteins in milk, this study utilized microfiltration (MF) combined with ultrasonication to treat skim milk and investigated its efficiency in removing bacteria and retaining bioactive proteins compared with HTST pasteurization and microfiltration alone. Results showed that microfiltration combined with ultrasonication at 1296 J/mL could completely remove the bacteria in skim milk. Ultrasonication further extended the shelf life (4 °C) of microfiltered skim milk, which could reach at least 40 days when MF was combined with ˃1296 J/mL ultrasonication. In addition, ELISA showed that HTST pasteurization significantly decreased the levels of IgG by ~30%, IgA by ~ 50%, IgM by ~60%, and lactoferrin by ~40%, whereas the activity of the enzymes lactoperoxidase and xanthine oxidase were also decreased by ~ 20%. Compared with HTST, MF alone or combined with ultrasonication retained these bioactive proteins to a larger degree. On the other hand, proteomics indicated both damage to casein micelle and fat globule structures in milk when ultrasonication at >1296 J/mL was applied, as shown by increases in caseins and milk fat globular proteins. Simultaneously, this ultrasound intensity also decreased levels of bioactive proteins, such as complement factors. Taken together, this study provided new insights that may help to implement this novel combination of non-thermal technologies for the dairy industry aimed at improving milk quality and functionality.


Assuntos
Filtração , Armazenamento de Alimentos , Leite/química , Proteínas/química , Sonicação , Animais , Temperatura
10.
J Environ Manage ; 297: 113298, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34280854

RESUMO

The discharge of high levels of heavy metals into the environment is of concern due to its toxicity to aquatic life and potential human health impacts. Biofiltration systems have been used in urban environments to address nutrient contamination, but there is also evidence that such systems can be effective in reducing heavy metals concentration in stormwater. However, the accumulation pattern of heavy metals and lifespan of such systems, which are important in engineering design, have not been thoroughly explored. This study investigated the accumulation patterns of lead (Pb), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe), which are common in urban runoff, in non-vegetated filtration columns using three different types of filter media, namely sand (S), and mixtures of sand with fly ash (sand-fly ash mix, SF), and with zeolite (sand-zeolite mix, SZ). The columns were assessed in terms of infiltration rate, the mass of heavy metals accumulation at different depths, and formation of crust layer (schmutzdecke) at the surface. The results show that most of the heavy metals accumulated at the top 5-10 cm of the filter media. However, Zn was found adsorbed to a depth of 15 cm in S and SZ columns, while Mn and Fe were present in column S throughout the entire 30 cm depth of the filter media. The presence especially of Zn, Mn, and Fe in the deeper portions of the filter media before the top 5 cm layer reached its maximum adsorption capacity, hints that transport to the deeper layers is not necessarily dependent on saturation of the upper layers for these heavy metals. SF accumulated heavy metals most at the top 5 cm of the filter media layer, and retained twice the mass of heavy metals in the crust layer, compared to S and SZ columns. SF also yielded the lowest value of infiltration rate of 31 mm/h. Considering both metals accumulation and clogging potential of the filter media, the periodic maintenance of these systems is suggested to be approximately between 1.5 and 3 years.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Zeolitas , Cinza de Carvão , Filtração , Humanos , Poluentes Químicos da Água/análise
11.
J Environ Manage ; 297: 113336, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34325368

RESUMO

PFAs (poly and perfluoroalkyl compounds) are hazardous and bioaccumulative chemicals that do not readily biodegrade or neutralize under normal environmental conditions. They have various industrial, commercial, domestic and defence applications. According to the Organization for Economic Co-operation and Development, there are around 4700 PFAs registered to date. They are present in every stream of life, and they are often emerging and are even difficult to be detected by the standard chemical methods. This review aims to focus on the sources of various PFAs and the toxicities they impose on the environment and especially on humankind. Drinking water, food packaging, industrial areas and commercial household products are the primary PFAs sources. Some of the well-known treatment methods for remediation of PFAs presented in the literature are activated carbon, filtration, reverse osmosis, nano filtration, oxidation processes etc. The crucial stage of handling the PFAs occurs in determining and analysing the type of PFA and its remedy. This paper provides a state-of-the-art review of determination & tools, and techniques for remediation of PFAs in the environment. Improving new treatment methodologies that are economical and sustainable are essential for excluding the PFAs from the environment.


Assuntos
Água Potável , Fluorcarbonetos , Poluentes Químicos da Água , Carvão Vegetal , Água Potável/análise , Filtração , Fluorcarbonetos/análise , Poluentes Químicos da Água/análise
12.
J Environ Manage ; 297: 113375, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34325375

RESUMO

This study evaluates the operational status of twenty-six biofilter facilities across nine cities in Sweden, with respect to their functional design criteria, engineered design features (filter media composition, hydraulic conductivity, and drawdown time), and includes a visual inspection of the biofilter components (pre-treatment, in/outlet structures, filter media, and vegetation). These indicators were used to examine the performance level of each biofilter in achieving their design objectives set by the operators. Furthermore, it was investigated whether the biofilter facilities had been properly maintained to meet the objectives. Results indicate that the soil media used was consistent with respect to percentage sand, fines, and organic matter and comparable to design recommendations used by municipalities in other countries. The field-tested hydraulic conductivity for the biofilters ranged from 30 to 962 mm/h. This range of values, along with noticeable sediment accumulation within the biofilter indicate that not all the sites were operating optimally. Pre-treatment stages in poor condition with high volumes of sediment and litter accumulation were the primary causes for, and indicators of, low hydraulic conductivity rates. The ponding volume calculations revealed that at least 40 % of facilities did not have enough capacity to retain every-day and/or design rainfall due to design and/or construction flaws. These analyses raise concerns that, for a considerable number of the biofilters surveyed, water retention and flood protection identified by operators as prioritised objectives are not being met. This raises significant concerns about the functionality of biofilter in practice. Finally, some suggestions are given for tackling the design and maintenance problems discovered.


Assuntos
Filtração , Purificação da Água , Cidades , Chuva , Solo , Suécia
13.
Artigo em Inglês | MEDLINE | ID: mdl-34281105

RESUMO

To cope with the shortage of filtering facepiece respirators (FFRs) caused by the coronavirus disease (COVID-19), healthcare institutions have been forced to reuse FFRs using different decontamination methods, including vapor hydrogen peroxide (VHP). However, most healthcare institutions still struggle with evaluating the effect of VHP on filtration efficiency (FE) of the decontaminated FFRs. We developed a low-cost in-house FE assessment using a novel 3D-printed air duct. Furthermore, we assessed the FE of seven types of FFRs. Following 10 VHP cycles, we evaluated the FE of KN95 and 3M-N95 masks. The 3M-N95 and Benehal-N95 masks showed significant lower FE (80.4-91.8%) at fine particle sizes (0.3-1 µm) compared to other FFRs (FE ≥ 98.1%, p < 0.05). Following 10 VHP cycles, the FE of KN95 masks was almost stable (FE stability > 99.1%) for all particle sizes, while 3M-N95 masks were stable only at 2 and 5 µm (FE stability > 98.0%). Statistically, FE stability of 3M-N95 masks at 0.3, 0.5, and 0.7 µm was significantly lower (p ≤ 0.006) than 2 and 5 µm. The in-house FE assessment may be used as an emergency procedure to validate the decontaminated FFRs, as well as a screening option for production control of FFRs. Following VHP cycles, both masks showed high stability at 5 µm, the size of the most suspected droplets implicated in COVID-19 transmission.


Assuntos
COVID-19 , Dispositivos de Proteção Respiratória , Descontaminação , Reutilização de Equipamento , Filtração , Humanos , Peróxido de Hidrogênio , SARS-CoV-2 , Ventiladores Mecânicos
14.
PLoS One ; 16(7): e0254540, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34260643

RESUMO

Coronaviruses (CoVs) are a family of viruses that are best known as the causative agents of human diseases like the common cold, Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS) and COVID-19. CoVs spread by human-to-human transmission via droplets or direct contact. There is, however, concern about potential waterborne transmission of SARS-CoV-2, the virus responsible for COVID-19, as it has been found in wastewater facilities and rivers. To date, little is known about the stability of SARS-CoV-2 or any other free coronavirus in aquatic environments. The inactivation of terrestrial CoVs in seawater is rarely studied. Here, we use a porcine respiratory coronavirus (PRCV) that is commonly found in animal husbandry as a surrogate to study the stability of CoVs in natural water. A series of experiments were conducted in which PRCV (strain 91V44) was added to filtered and unfiltered fresh- and saltwater taken from the river Scheldt and the North Sea. Virus titres were then measured by TCID50-assays using swine testicle cell cultures after various incubation times. The results show that viral inactivation of PRCV in filtered seawater can be rapid, with an observed 99% decline in the viral load after just two days, which may depend on temperature and the total suspended matter concentration. PRCV degraded much slower in filtered water from the river Scheldt, taking over 15 days to decline by 99%, which was somewhat faster than the PBS control treatment (T99 = 19.2 days). Overall, the results suggest that terrestrial CoVs are not likely to accumulate in marine environments. Studies into potential interactions with exudates (proteases, nucleases) from the microbial food web are, however, recommended.


Assuntos
Infecções por Coronavirus/transmissão , Coronavirus Respiratório Porcino/isolamento & purificação , Testículo/citologia , Águas Residuárias/virologia , Animais , Células Cultivadas , Filtração , Masculino , Projetos Piloto , Coronavirus Respiratório Porcino/patogenicidade , Rios/virologia , Suínos , Testículo/virologia , Fatores de Tempo , Carga Viral , Microbiologia da Água
15.
Huan Jing Ke Xue ; 42(7): 3348-3357, 2021 Jul 08.
Artigo em Chinês | MEDLINE | ID: mdl-34212660

RESUMO

Protein-like dissolved organic matter (pDOM), which is ubiquitous in natural waters, is a critical precursor of nitrogenous disinfection byproducts. Recently, the control and elimination of pDOM have been a growing concern during drinking water treatment processes. In this study, a high-performance size exclusion chromatography system coupled with photo-diode array, fluorescence detector, and online organic carbon detector (HPSEC-PDA/FLD/OCD) was used to determine the removal behaviors of different-sized pDOM from two full-scale drinking water treatment plants (DWTPs). Coagulation and activated carbon adsorption were selected for bench-scale experiments to further assess the removal behavior of pDOM during conventional water treatment processes. The results showed that different-sized pDOM fractions exhibited different removal characteristics. Pre-oxidation can effectively remove some tyrosine-like and tryptophan-like components with high MW, and as the oxidization effect was enhanced, more high MW fractions decomposed into low MW ones. Conversely, some aliphatic pDOM fractions in high MW (e.g., aliphatic proteins) were not subject to pre-oxidation removal. The coagulation-sedimentation unit was efficient in removing high MW fractions, specifically tryptophan-like fractions. Additionally, some pDOM components may be released during coagulation. pDOM with low MW and high hydrophobicity were easily removed during activated carbon filtration. However, long-term operation of the activated carbon filter may breed microorganisms, resulting in the partial release of pDOM fractions. Moreover, UV disinfection processes promoted the degradation of low MW pDOM components. Due to the complex water quality and uncontrollable microbial activities, the aforementioned water treatment units did not exhibit a synergistic effect on pDOM removal. In comparison with humic-like substances, pDOM was susceptible to water quality changes, and its removal was limited in the surveyed DWTPs. Therefore, DWTPs must strengthen pDOM monitoring in influent and effluent and adjust the operating parameters of different treatment units in a timely manner. Moreover, the combination of advanced water treatment processes, such as ozone-biological activated carbon process and nanofiltration, should also be considered to strictly control pDOM component removal.


Assuntos
Água Potável , Poluentes Químicos da Água , Purificação da Água , Carvão Vegetal , Filtração , Compostos Orgânicos/análise , Poluentes Químicos da Água/análise
16.
J Environ Manage ; 296: 113204, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34243089

RESUMO

Fe2+-activated persulfate process has been introduced into sludge conditioning currently, however the key sludge properties characteristics are worthwhile comprehensively considering for the engineering implementation and management. The results indicated that both the optimal dosages of persulfate and Fe2+ were 0.6 mmol/gTS for sludge dewaterability amelioration, and the reduction efficiencies of capillary suction time (CST), specific resistance of filtration (SRF), and water content (Wc) of dewatered sludge cake reached to 90.5%, 97.2%, and 22.4%, respectively. Significantly, the persulfate and Fe2+ exerted distinctive roles in the conditioning process. The increased persulfate could promote the oxidatively disintegrated effect on sludge flocs, rendering the decrease of particle size. With the oxidative decomposition of the negatively charged biopolymers, sludge zeta potential rose gradually. However, Fe2+ contributed to more persulfate activation to generate free radicals, and the produced Fe3+ could further electrically neutralize the broken sludge fragments. The core mechanism of Fe2+-activated persulfate conditioning is "destroying and re-building" of sludge flocs. Noteworthily, EPS protein was oxidatively degraded more preferentially than EPS polysaccharide, and the decrease of the α-helix content of EPS protein was conducive to the enhancement of sludge dewaterability. Furthermore, the hydrophilic functional groups reduced clearly and element chemical states on sludge flocs altered pronouncedly, also the destroyed structure and microchannel facilitated the flowability of water. These findings provide theoretical and technical support for the practical engineering implementation of the Fe2+-activated persulfate conditioning process.


Assuntos
Filtração , Esgotos , Biopolímeros , Oxirredução , Água
17.
J Environ Manage ; 296: 113218, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34246906

RESUMO

Coagulation/flocculation is an extensive and effective pretreatment technology for improving the sludge dewaterability. A series of hydrophobically associated cationic starch-based flocculants (CS-DMRs) with different degrees of hydrophobicity but similar charge densities were designed and synthesized. The CS-DMRs exhibited excellent sludge dewatering performance. The dewaterability of sludge increased with the hydrophobicity of the CS-DMRs, and the filter cake moisture content (FCMC) and specific resistance to filtration (SRF) could be reduced from 95.47% and 7.09 × 1012 m/kg to 79.26% and 2.258 × 1012 m/kg, respectively, at a constant pressure of 0.05 MPa after conditioned by the starch-based flocculant with the highest hydrophobicity at its optimal dose. Moreover, due to their amphiphilic structures, CS-DMRs could closely interact with the negatively charged extracellular polymeric substances (EPS), efficiently compress the protein and polysaccharide in EPS, and release the bound water. A second-order polynomial model was proposed according to the phenomenological theory to quantitatively analyze the effect of hydrophobicity in these starch-based flocculants on the sludge dewaterability. The structure-activity relationship was built, and the optimal dose and corresponding FCMC could be theoretically estimated accordingly. The results were in good agreement with the experimental results. The dewatering mechanisms were also discussed in detail on the basis of the changes in the FCMC, SRF, capillary suction time, properties of sludge flocs, compression coefficient, microstructures of sludge cakes, EPS fractions and components, and spatial distributions of the proteins and polysaccharides. In addition to charge neutralization, the hydrophobic association effects of CS-DMRs played an important role in the formation of drainage channels and net-like porous structures in the sludge cake to improve its permeability and filterability. This study thus provided a good understanding of the structural effects of the starch-based flocculants on the sludge dewaterability. The results are greatly beneficial to the fabrication and utilization of environment-friendly and high-performance natural polymeric conditioners for sludge treatment.


Assuntos
Esgotos , Eliminação de Resíduos Líquidos , Filtração , Floculação , Interações Hidrofóbicas e Hidrofílicas , Amido , Água
18.
J Environ Manage ; 296: 113196, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34252848

RESUMO

Considering the reduction and resource utilization of landfill sludge (LS) and fresh sludge (FS), Fe2+ activated Na2S2O8 is proposed. The effects of the molar ratio of Fe2+/S2O82- and the addition of Na2S2O8 on the dewatering performance of sludge were studied by vacuum filtration experiments. Consolidation tests were conducted on the sludge with different Na2S2O8 dosage, and the compression, consolidation, and permeability characteristics of the sludge were researched. Besides, via particle size distribution (PSD) and scanning electron microscope (SEM) test, the variation of particle size of sludge was studied from the microscopic perspective. The results are as follows: the specific resistance of filtration (SRF) of LS and FS decreases by 99.3%, 95.2% at an optimal dosage (the molar ratio of (Fe2+/S2O82-) = 1, 30% Na2S2O8); the particle size of LS and FS is significantly smaller; the consolidation and permeability coefficients are increased by 1-2 orders of magnitude compared with non-conditioned sludge; the water content of LS and FS drops from 86.5% to 58.4%, 82.4%-59.7%. The research results have certain guiding significance for the in-situ treatment of sludge deep dewatering.


Assuntos
Esgotos , Sulfatos , Filtração , Compostos de Sódio , Instalações de Eliminação de Resíduos , Eliminação de Resíduos Líquidos , Água
19.
Bioresour Technol ; 339: 125583, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34303103

RESUMO

Chemically enhanced primary treatment (CEPT) is an emerging sewage treatment strategy due to its high efficiency and small land requirement. CEPT sludge can be easily dewatered and used for energy recovery through incineration. However, with large amount of reusable nutrients (40% organic carbon, 23% lipids, and 17% protein), the value of CEPT sludge may have been underestimated. In this study, the biorefinery potential of CEPT sludge has been proven via production of 28.9 g/L ethanol or 50.3 g/L lactic acid (LA) or 1.43 filter paper unit (FPU)/mL cellulase from 10 g of CEPT sludge experiment. Inhibition on cell growth and potential inhibitors from plasticizers, pharmaceuticals, and surfactants were determined. Nevertheless, production titer was not affected or performed even better than the non-inhibitors controls. CEPT sludge showed significant potential in biochemical conversion, and the related products may offer an opportunity to support wastewater treatment toward sustainability and carbon neutrality.


Assuntos
Celulase , Purificação da Água , Carbono , Filtração , Esgotos
20.
ACS Appl Mater Interfaces ; 13(27): 32205-32216, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34225456

RESUMO

Biofouling remains as a persistent problem impeding the applications of membranes for water and wastewater treatment. Green anti-biofouling of membranes made of natural and environmentally friendly materials and methods is a promising strategy to tackle this problem. Herein, we have developed a functionalized PVDF membrane with stimuli-responsive lysozyme nanocapsules (NCP). These nanocapsules can responsively release lysozyme according to environmental stimuli (pH and redox) induced by bacteria. Results showed that (i) the surface of the functionalized membrane with NCP had enhanced hydrophilicity, reduced roughness, and negative charge, (ii) a remarkable reduction of adsorption of proteins, polysaccharides, and bacteria was achieved by the functionalized membrane, and (iii) the colony forming unit (CFU) of bacteria on a membrane surface was reduced more than 80% within 24 h of contact. In addition, the NCP membrane showed excellent anti-biofouling activity regarding the bacterial viability being 12.5 and 8.3% on the membrane after filtration with 108 CFU mL-1 Escherichia coli and Staphylococcus aureus solution as feed, respectively. The coating layer and assembled nanocapsules endowed the membrane with improved lysozyme stability, anti-adhesion performance, and antibacterial activity. Stimuli-responsive lysozyme nanocapsule engineered microfiltration membranes show great potential for anti-biofouling in future practical application.


Assuntos
Incrustação Biológica/prevenção & controle , Engenharia , Filtração , Membranas Artificiais , Microtecnologia/métodos , Muramidase/química , Muramidase/farmacologia , Antibacterianos/química , Antibacterianos/farmacologia , Aderência Bacteriana/efeitos dos fármacos , Cápsulas , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Viabilidade Microbiana/efeitos dos fármacos , Nanoestruturas/química , Oxirredução , Propriedades de Superfície
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