Log Removal Research Articles

Chemically enhanced primary treatment of municipal wastewater with ferrate(VI).

Chemically enhanced primary treatment (CEPT) with ferrate(VI), a multifunctional treatment agent, was investigated for the treatment of municipal wastewater in a laboratory-scale study. The treatment performance was evaluated at different ferrate(VI) doses (0.0-9.0mg/L as Fe) and pH (6.0 and 7.5). The optimal removals of total suspended solids (TSS) (52%), total chemical oxygen demand (COD) (34%), and total phosphorus (47%) were achieved at the highest ferrate(VI) dose (9.0mg/L as Fe) and the weakly alkaline condition (pH 7.5). The pollutant abatements principally ascribed to the formation of large-sized aggregate and ensuing sedimentation fell within the reported ranges of CEPT with traditional coagulants. However, different from conventional CEPT, ferrate(VI) appreciably removed recalcitrant dissolved organic phosphorus (49%) and simultaneously inactivated total coliform (3.30 log removal) and Escherichia coli (3.67 log removal) at 9.0mg/L Fe(VI) and pH 7.5. The CEPT with ferrate(VI) offers an innovative alternative for improving municipal wastewater treatment. PRACTITIONER POINTS: Ferrate(VI) represents a promising agent for chemically enhanced primary treatment (CEPT) of municipal wastewater. CEPT with ferrate(VI) can effectively alleviate TSS, total COD, and total P via the formation of large-sized aggregates and ensuing sedimentation. Ferrate(VI) can substantially remove recalcitrant dissolved organic phosphorus in municipal wastewater. Different from other CEPT coagulants, ferrate(VI) can appreciably inactivate bacterial indicators during CEPT. Higher ferrate(VI) dose and weakly alkaline pH favor the performance of ferrate(VI) CEPT.

Efficient synergistic disinfection by ozone, ultraviolet irradiation and chlorine in secondary effluents

Disinfection of secondary effluents is vital to provide a sustainable aquatic environment, minimize microbial risks and guarantee public and environmental safety. This study investigated the effectiveness of six treatment trains including single and combined disinfection processes (i.e., ozone alone, ultraviolet (UV) irradiation alone, chlorine alone, sequential ozone-UV, sequential ozone-chlorine and sequential ozone-UV-chlorine) on bacterial inactivation, as well as bulk water quality parameters such as color, turbidity, absorbance at 254 nm (UV254), dissolved organic carbon (DOC) and fluorescence based on samples collected from an actual water reclamation plant (WRP). For the single disinfection processes, when the ozone, UV and chlorine doses reached 5 mg/L, 15 mJ/cm2 and 4 mg/L, respectively, the log removal of Escherichia coli (E. coli) reached 5 log. A trailing phenomenon was observed with further increases in the disinfectant dosage. Under the combined treatment scenarios, ozone pretreatment resulted in substantial removal of color, turbidity, UV254, fluorescence excitation-emission matrix (FEEM) and chlorine consuming organics, thus enhancing the efficiency of subsequent UV irradiation or chlorine treatments. In the sequential ozone-UV-chlorine experiments, E. coli inactivation reached 7 log with ozone, UV and available chlorine of 3 mg/L, 5 or 10 mJ/cm2 and 2.5 mg/L, respectively. On the basis of the results from the actual WRP, the estimated operating cost per unit for the disinfection systems is 0.065 CNY/t, which is economical for long-term operation.

Influence of sand depth and pause period on microbial removal in traditional and modified biosand filters

Three different-sized biosand filters (i.e., the center for Affordable Water and Sanitation Technology v10 concrete filter, a 5-gal bucket filter, and a 2-gal bucket filter with fine sand depths of 54, 15, and 10 cm, respectively), configured with and without the addition of iron nails to the diffuser basin, were evaluated for removal of bacteria, protozoa, and viruses over pause periods ranging from 1 to 72 hrs. Biosand filtration proved effective at all pause periods tested, and log10 removal of bacteria and protozoan cysts for all filter sizes and configurations ranged from 3 to 4. The addition of nails resulted in significantly better (p<0.05) bacteria removal for all filter sizes and significantly better (p<0.02) protozoan removal for the bucket-sized filters. Log10 virus removal for all filter types and sizes ranged from <1 to 6. Both the pause period and filter type (size/configuration) influenced virus removal, and the addition of nails to the filter improved virus removal at the shorter pause periods. Scaled-down biosand filters provide a viable household water treatment option for some of the millions of people that still lack access to an improved water source.

Investigation of reduction in risk from antibiotic resistance genes in laboratory wastewater by using O3 , ultrasound, and autoclaving.

Biological laboratory wastewater containing both antibiotic-resistant bacteria (ARB) and antibiotics is a potential source of antibiotic resistance genes (ARGs). Thus, we determined the efficacy of autoclaving, a common disinfection method, in eliminating 5 ARGs (sul1, sul2, tetW, tetM, amp) and the integrase-encoding gene intI1 from laboratory wastewater. Autoclaving (15min, 121°C) inactivated all bacteria including ARB, whereas ARGs persisted in the wastewater with limited reduction even after 60min of treatment. Ozonation (O3 ), ultrasound (US), O3 /US, and autoclaving followed by O3 were investigated for their ability to reduce ARGs in laboratory wastewater. With O3 and O3 /US, the reduction rate ranged from 5.44 to 7.13 log for all ARGs investigated. Wastewater treatment with US alone did not reduce ARGs under the present experimental conditions (150W, 53kHz). Among the four treatments, autoclaving followed by O3 treatment showed the highest reduction rates in the shortest time; however, further optimization and investigation are needed for the advanced treatment of bio-laboratory wastewater. Overall, this study provides novel insights into ARG sources and demonstrates that advanced oxidation methods can be useful to optimize laboratory wastewater treatment for ARG inactivation. PRACTITIONER POINTS: Bio-laboratory wastewater is potential reservoir of ARGs. Conventional autoclaving was not able to reduce ARGs to a low level. Autoclaving-O3 completely eliminate all the bacteria. Autoclaving-O3 reduced ARGs efficiently (6.12-7.86 logs removal in 60min).

Determination of log removal values of bacteria by spiral-wound reverse osmosis modules and a hollow fiber ultrafiltration module using Escherichia coli and indigenous heterotrophic bacteria as indicators.

The use of reverse osmosis (RO) membranes has been expanding not only to medical applications but also to water supply and reclaimed water applications due to its strong ability to remove a wide range of contaminants. Many researchers reported RO performance as a barrier against waterborne viruses; however, there are limited reports on its ability to remove bacteria from water. This investigation evaluated the removal performances of several spiral-wound RO modules and a hollow fiber ultrafiltration (UF) module in two different ways: dosing tests in batch-wise mode operation and in continuous-mode operation. The dosing tests of Escherichia coli using RO modules confirmed that E. coli could leak from the feed-side into the permeate. The log removal values (LRVs) (4.21- to >7.44-log10) by the RO modules from different production lots were found to vary greatly. In continuous-mode operation of the RO module, the LRVs for indigenous heterotrophic bacteria decreased over the operation period. These results clearly illustrate that bacteria, which originate on the feed-side, can leak into the permeate-side and then begin to proliferate in the permeate. On the other hand, using a UF module, E. coli was not detected in the permeate regardless of the operation mode.

A Critical Review on Ultraviolet Disinfection Systems against COVID-19 Outbreak: Applicability, Validation, and Safety Considerations.

The global health-threatening crisis from the COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights the scientific and engineering potentials of applying ultraviolet (UV) disinfection technologies for biocontaminated air and surfaces as the major media for disease transmission. Nowadays, various environmental public settings worldwide, from hospitals and health care facilities to shopping malls and airports, are considering implementation of UV disinfection devices for disinfection of frequently touched surfaces and circulating air streams. Moreover, the general public utilizes UV sterilization devices for various surfaces, from doorknobs and keypads to personal protective equipment, or air purification devices with an integrated UV disinfection technology. However, limited understanding of critical UV disinfection aspects can lead to improper use of this promising technology. In this work, fundamentals of UV disinfection phenomena are addressed; furthermore, the essential parameters and protocols to guarantee the efficacy of the UV sterilization process in a human-safe manner are systematically elaborated. In addition, the latest updates from the open literature on UV dose requirements for incremental log removal of SARS-CoV-2 are reviewed remarking the advancements and existing knowledge gaps. This study, along with the provided illustrations, will play an essential role in the design and fabrication of effective, reliable, and safe UV disinfection systems applicable to preventing viral contagion in the current COVID-19 pandemic, as well as potential future epidemics.

Low voltage iron electrocoagulation as a tertiary treatment of municipal wastewater: removal of enteric pathogen indicators and antibiotic-resistant bacteria

In this paper we analyse the feasibility of low voltage iron electrocoagulation as a means of municipal secondary effluent treatment with a focus on removal of microbial indicators, Antibiotic Resistant Bacteria (ARB) and nutrients. A laboratory scale batch unit equipped with iron electrodes was used on synthetic and real secondary effluent from a municipal wastewater treatment plant. Synthetic secondary effluent was separately assayed with spiked Escherichia coli WR1 and with bacteriophage ΦX174, while real effluent samples were screened before and after treatment for E. coli, Extended Spectrum Betalactamase-producing E. coli, Enterococci, Vancomycin Resistant Enterococci, Clostridium perfringens spores and somatic coliphages. Charge dosage (CD) and charge dosage rate (CDR) were used as the main process control parameters. Experiments with synthetic secondary effluent showed >4log10 and >5log10 removal for phage ΦX174 and for E. coli WR1, respectively. In real effluents, bacterial indicator removal exceeded 3.5log10, ARB were removed below detection limit (≥2.5log10), virus removal reached 2.3log10 and C. perfringens spore removal exceeded 2.5log10. Experiments in both real and synthetic wastewater showed that bacterial removal increased with increasing CD and decreasing CDR. Virus removal increased with increasing CD but was irresponsive to CDR. C. perfringens spore removal increased with increasing CD yet reached a removal plateau, being also irresponsive to CDR. Phosphate removal exceeded 99%, while total nitrogen and chemical oxygen demand removal were below 15% and 58%, respectively. Operational cost estimates were made for power and iron plate consumption, and were found to be in the range of 0.01 to 0.24€/m3 for the different assayed configurations. In conclusion, low voltage Fe-EC is a promising technology for pathogen reduction of secondary municipal effluents, with log10 removals comparable to those achieved by conventional disinfection methods such as chlorination, UV or ozonation.

Enhanced Antibacterial Photocatalytic Activity of Porous Few-Layer C₃N₄.

Nowadays, antibacterial photocatalytic activity of semiconductors has attracted great attention due to its excellent stability, good biocompatibility and no disinfection byproducts. Herein, a porous few-layer C₃N₄ was successfully fabricated via a simple and low-cost bottom-up method. The asprepared porous few-layer C₃N₄ exhibits large specific surface areas, which is about 4.8 times than bulk C₃N₄. Under the light (<430 nm) irradiation, reactive oxygen species (ROS) (singlet oxygen (1O₂), hydroxyl radicals (·OH), and superoxide (O·-₂)) can be generated. The porous few-layer C₃N₄ was used as an antibacterial agent to kill gram-positive bacterium S. Aureus with an anibacterial efficiency up to 99.7%. The log removal rate of the porous few-layer C₃N₄ is more than 50 times than the bulk C₃N₄. The material shows a potential application in water purification and antibacterial photocatalytic therapy.

Biosand Filter as a Point-of-Use Water Treatment Technology: Influence of Turbidity on Microorganism Removal Efficiency

The number of people living without access to clean water can be reduced by the implementation of point-of-use (POU) water treatment. Among POU treatment systems, the domestic biosand filter (BSF) stands out as a viable technology. However, the performance of the BSF varies with the inflow water quality characteristics, especially turbidity. In some locations, people have no choice but to treat raw water that has turbidity above recommended levels for the technology. This study aimed to measure the efficiency with which the BSF removes microorganisms from well water and from fecal-contaminated water with turbidity levels of 3, 25, and 50 NTU. Turbidity was controlled by the addition of kaolin to water. Turbidity removal varied from 88% to 99%. Reductions in total coliform (TC) and Escherichia coli ranged from 0.54–2.01 and 1.2–2.2 log removal values (LRV), respectively. The BSF that received water with a higher level of turbidity showed the greatest reduction in the concentration of microorganisms. Additional testing with water contaminated with four bacterial pure cultures showed reductions between 2.7 and 3.6 LRV. A higher reduction in microorganisms was achieved after 30–35 days in operation. Despite the filter’s high efficiency, the filtrates still had some microorganisms, and a disinfection POU treatment could be added to increase water safety.

Synergistic effect of UV/chlorine in bacterial inactivation, resistance gene removal, and gene conjugative transfer blocking

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) were investigated from effluent of two hospital and two municipal wastewater treatment plants (WWTPs) before and after disinfection. The results of network analysis showed that 8 genera were identified to be the main potential hosts of ARGs, including Mycobacterium, Ferruginibacter, Thermomonas, Morganella, Enterococcus, Bacteroides, Myroides and Romboutsia. The removal of ARGs and their possible bacterialhosts were synchronous and consistent by chlorine or ultraviolet (UV) disinfection in WWTPs. The mechanisms of ARB and ARGs removal, and conjugation transfer of RP4 plasmids by UV, chlorine and synergistic UV/chlorine disinfection was revealed. Compared to UV alone, ARB inactivation was improved 1.4 log and photoreactivation was overcomeeffectively by UV/chlorine combination (8 mJ/cm2, chlorine 2 mg/L). However, ARGs degradation was more difficult than ARB inactivation. Until UV dosage enhanced to 320 mJ/cm2, ARGs achieved 0.58–1.60 log removal. Meanwhile, when 2 mg/L of chlorine was combined with UV combination, ARGs removal enhanced 1–1.5 log. The synergistic effect of adding low-dose chlorine (1–2 mg/L) during UV radiation effectively improved ARB and ARGs removal simultaneously. The same synergistic effect also occurred in the horizontal gene transfer (HGT). Non-lethal dose chlorine (0.5 mg/L) increased the conjugation transfer frequency,which confirmed that the mRNA expression levels of type IV secretion system (T4SS) proteins vir4D, vir5B and vir10B were significantly enhanced. The risk of RP4 plasmid conjugation transfer was significantly reduced with UV/chlorine (UV ≥ 4 mJ/cm2, chlorine ≥ 1 mg/L). These findings may serve as valuable implications for assessing and controlling the risk of ARGs transfer and propagation in the environment.

Removal of Bacillus spores from stainless steel pipes by flow foam: Effect of the foam quality and velocity

Food industry cleaning operations must efficiently mitigate any risk of remaining unwanted contamination without consuming large amounts of water, chemicals and energy. This study's originality was in analysing the capacity of flowing foams to remove Bacillus spores from stainless steel surfaces. A set-up was designed to allow the formation of wet foams to flow under three differing regimes: bubble-size rearrangement was observed at the wall with increased velocity, thus reducing cleaning efficiency. Foam at 50% air/water and low velocities permitted a 2 log removal of B. amyloliquefaciens spores, which is comparable to similar CIP conditions. Removal kinetics were modelled showing potentially very high constant rates at the start of cleaning. Such efficient cleaning was related to the local high wall shear stress fluctuations and to the capillary forces (low velocities, favorable bubble-size repartition and to the hydrophilicity of bacteria spores).

Contribution of biofilm layer to virus removal in gravity-driven membrane systems with passive fouling control

Passive gravity-driven membrane (PGM) filtration is a type of gravity-driven membrane (GDM) filtration operated with passive physical fouling control measures that add limited to no complexity to the system (e.g. permeate flux interruptions, gravity-driven air scouring, system draining), allowing a greater permeate flux to be sustained. A key aspect of PGM/GDM systems is the development of a structurally loose and permeable biofilm layer on the membrane that enables a sustainable flux to be achieved and has also been associated with improved removal of humic acids, polysaccharides, proteins, assimilable organic carbon and microcystins. The present study investigated if the biofilm layer of PGM systems also contributes to virus removal, for both intact and breached PGM systems. Breach sizes considered ranged from 20 to 180 µm. Challenge tests (CTs) identified an increase of 2.0+ in the log removal value (LRV) for viruses in both intact and breached PGM systems when a biofilm layer was present, suggesting that the biofilm layer is capable of bridging the gap over integrity breaches, acting as a secondary barrier to contaminants that would otherwise bypass treatment by flowing through the breach. Pressure decay tests (PDTs), however, did not identify the same increase in LRVs as that of CTs, suggesting that the standard PDT approach cannot consider the contribution of the biofilm layer to the removal of small material such as viruses. An alternative integrity testing protocol for PGM systems was developed using a modified PDT approach that takes into account the additional removal provided by the biofilm layer. This alternative protocol is also simpler and requires less frequent testing, contributing to the simplification of overall operation of PGM systems in small/remote communities and decentralized applications.

Influence of filter media depth and vegetation on Faecal Coliform removal by stormwater biofilters

AbstractBiofilters are promising technologies that widely applied in the treatment of urban stormwater. However, the microbial removal capacity performance depends greatly on the design of biofilters. Hence, this laboratory study attempts to investigate the influence of filter media depths (i.e. 150, 250, 350 and 450 mm) and the variation of native plants, that is, Cow Grass (Axonopus compressus) and Pearl Grass (Axonopus compressus, dwarf) in removing stormwater microorganism particularly Faecal Coliform (FC). Findings showed that a minimum media depth of 300 mm was required to achieve &gt;1 log FC removal. The mean removal of FC at 450 mm depth filter exceeded 2 log for both Cow and Pearl grass biofilter columns. Results showed that there was no statistically significant difference in vegetation type on the performance of FC removal, however, Cow grass biofilter column revealed higher FC mean log removal compared to Pearl grass biofilter column.

Building a robust and scalable lentiviral vector purification platform

Background & Aim Lentiviral vectors (LVV) are common vehicles of genetic delivery for cell and gene therapies. LVV commercial manufacturing is costly and downstream processing (DSP) is a primary driver for the high costs due to challenges in maintaining viral infectivity. Additionally, these processes are not standardized across the industry and have poor process definition, resulting in large batch-to-batch variability, limited robustness, performance, and scalability. In collaboration with CCRM, the GE Fast Trak Centre for Advanced Therapeutic Cell Technologies (CATCT) has developed a DSP platform that can process LVV from multiple upstream systems; suspension and serum-free cultures from both stable producer and transient-transfection modalities. The different characteristics of these systems (transient vs. inducible, cell viability and density at harvest, amount of host cell contaminants, etc.) showcase the compatibility of our process with various upstream sources. Our semi-closed, single-use, single-day, room temperature LVV purification process yields infectious recoveries and contaminant clearances that are on par with current industry standards, while maintaining robustness and scalability. Methods, Results & Conclusion The final full process consists of nucleic acid digestion inside the bioreactor, clarification using filtration, ultrafiltration and diafiltration using tangential flow filtration, chromatography with multi-modal Capto™ Core 700, an optional secondary concentration, and finally 0.2 µm sterile filtration. Overall infectious titre recoveries and final concentrations of 13.7% ± 6.2% and 5.2E7 TU/mL (stable) and 30.8% ± 2.4% and 1.4E8 TU/mL (transient) have been achieved, with a ≥ 2-log removal of host cell protein and DNA in both. Additionally, a 25 L pilot run was completed with similar results, demonstrating the scalability of the process. Supported by continual gains of process knowledge and understanding, we have built a robust, consistent, and scalable LVV purification platform.

Performance Evaluation of Water Filter Made from Oyong (&lt;i&gt;Luffa сylindrica&lt;/i&gt;) Fiber Coated with Silver Nano Particles for Coliform Bacteria Removal in Wastewater

Oyong fiber (OF) is widely available natural fiber, the material characteristics and porosity make it a suitable alternative for filtration media. Accordingly, to investigate the potential use of OF as filter material in the wastewater disinfection process, this study applied different silver nanoparticles coating onto OF and proposed a new filter structure at lower cost. The OF coated AgNPs and OF coated Ag-GO were successfully synthesized following the chemical reduction methods as reported in the literature. SEM image shown that silver nanoparticles were randomly distributed on the surface of OF. Both OF coated AgNPs and Ag-GO exhibited a good disinfection capability for Total Coliform removal from wastewater. The OF coated Ag-GO have better Total Coliform Log Removal Value (LRV) of 3.3 and still maintain stable disinfection ability even at high filtration rate.

Mitigation via physiochemically enhanced primary treatment of antibiotic resistance genes in influent from a municipal wastewater treatment plant

In this study, a combined coagulation-dissolved air flotation (DAF) process was employed as enhanced primary treatment (EPT) to simultaneously reduce eleven ARGs (tetA, tetM, tetQ, tetX, sul1, sul2, qnrD, ermB, blaTEM, aac(6′)-lb-cr, floR), class 1 integrons-integrase gene (intI1) and common pollutants in the influent of a WWTP and then compared to primary sedimentation alone. In the combined coagulation-DAF process, the optimum doses of PACl, FeCl3 and Al2(SO4)3 required to achieve a removal efficiency exceeding 90% of total suspended solids (TSS) were 25 mg/L, 75 mg/L and 100 mg/L, respectively. The log removal of all quantified ARGs treated by the combined coagulation-DAF process with the three coagulants exceeded 0.44-log, a higher removal efficiency of ARGs compared to primary sedimentation alone (0.03-log). Among the three coagulants, FeCl3 showed the highest log reduction for targeted ARGs. In addition, the three coagulants showed similar capabilities to non-selectively and modestly decrease most ARGs. Most ARGs and intl1 demonstrated strongly negative correlations with the removal efficiencies of physicochemical parameters in the treated wastewater, implying that co-removal of colloidal matter, solids, phosphate, ammonium and organic matter played a crucial role in reduction of ARGs during the combined coagulation-DAF process. Particularly, strong correlations were observed between the reduction of total phosphorus (TP) and ARGs, indicating that TP may provide a suitable proxy for reduction of ARGs in this process. Despite handling influent comprised of ARGs and pollutants of high levels and diverse types, the combined coagulation-DAF process led to improved removal of ARGs along with colloidal substances. Thus, the results demonstrate the potential of a combined coagulation-DAF process to reduce ARGs flowing into WWTPs.

Metagenomic insights into virus removal performance of an algal-based wastewater treatment system utilizing Galdieria sulphuraria

An algal wastewater treatment system capable of reducing dissolved organics, nutrients, and pathogenic bacteria to secondary discharge standards in a single step has been reported on previously. The current study evaluates pathogenic virus reduction in this algal wastewater treatment system and compares it with that in conventional wastewater treatment systems using culture- and nucleic acid-based quantitative methods and shotgun metagenomic sequencing technique. Log removal of somatic coliphages (3.13 ± 0.34), F-specific coliphages (1.23 ± 0.34), Enterovirus (1.05 ± 0.32), and Norovirus GI (1.49 ± 0.16) in the algal wastewater treatment system without any chlorination were comparable to those in the conventional wastewater treatment system with chlorination. While the virus community in the chlorinated effluent of the conventional system was diverse with ~250 species, only 14 discrete virus species were found in the unchlorinated effluent of the algal-based system, none of them pathogenic to humans. This study demonstrated the feasibility of the A-WWT system in delivering pathogenically-safe, high-quality effluent for disposal or beneficial reuse with minimal post-disinfectant demand.

Disinfection performance and mechanism of the carbon fiber-based flow-through electrode system (FES) towards Gram-negative and Gram-positive bacteria

The disinfection performance of a carbon fiber-based flow-through electrode system (FES) towards Gram-negative bacteria (Escherichia coli and fecal coliform) and Gram-positive bacteria (Enterococcus faecalis and Bacillus subtilis) in normal saline was systematically investigated over a wide range of applied voltages (1–5 V) and hydraulic retention times (HRTs) (1–10 s). It was revealed that the Gram-negative bacteria were more vulnerable to FES for their thinner cell walls, and over 6.5 log removal (no live bacteria detected) was achieved at the applied voltage of 2 V and HRT of 2 s; while Gram-positive bacteria were inactivated at slightly higher voltages (3 V, 2 s) or longer HRTs (2 V, 5 s). Bacterial inactivation was attributed to the change and rupture of cell membrane mainly by anode direct oxidation without bacterial regrowth/reactivation. In addition, negligible generation of the free chlorine at low voltages (≤2 V) can avoid the formation of potential chlorinated disinfection byproducts (DBPs). Hence, FES can offer a potential alternative to conventional disinfection methods for bacterial inactivation in natural and contaminated water.

Solar Powered Microplasma-Generated Ozone: Assessment of a Novel Point-of-Use Drinking Water Treatment Method.

Ozonation is widely used in high-income countries for water disinfection in centralized treatment facilities. New microplasma technology has reduced the energy requirements for ozone generation dramatically, such that a 15-watt solar panel is sufficient to produce small quantities of ozone. This technology has not been used previously for point-of-use drinking water treatment. We conducted a series of assessments of this technology, both in the laboratory and in homes of residents of a village in western Kenya, to estimate system efficacy and to determine if the solar-powered point-of-use water ozonation system appears safe and acceptable to end-users. In the laboratory, two hours of point-of-use ozonation reduced E. coli in 120 L of wastewater by a mean (standard deviation) of 2.3 (0.84) log-orders of magnitude and F+ coliphage by 1.54 (0.72). Based on laboratory efficacy, 10 families in Western Kenya used the system to treat 20 L of household stored water for two hours on a daily basis for eight weeks. Household stored water E. coli concentrations of >1000 most probable number (MPN)/100 mL were reduced by 1.56 (0.96) log removal value (LRV). No participants experienced symptoms of respiratory or mucous membrane irritation. Focus group research indicated that families who used the system for eight weeks had very favorable perceptions of the system, in part because it allowed them to charge mobile phones. Drinking water ozonation using microplasma technology may be a sustainable point-of-use treatment method, although system optimization and evaluations in other settings would be needed.

Developing a low-pressure and super stable electrochemical tubular reactive filter: Outstanding efficiency for wastewater purification

This research mainly focused on the development of strong oxidizing and ultra-stable flow-through porous anode materials for electrochemical reactive filter technology. In this study, a novel ultrahigh-throughput tubular reactive filter coated with β-PbO2 electrocatalytic layer (β-PbO2-TRF) was developed, which has super stability and reactivity, outperforming currently reported flow-through porous anode materials. The permeation rate of β-PbO2-TRF was achieved at 59.2 m3/(m2·h·bar) and expected service lifetime was as long as 253 years. Safety assessment test results showed no detectable Pb ions in solution was released from the β-PbO2 electrocatalytic layer. For electrochemical reactivity, the kinetic constants of convection-enhanced oxidation for Fe(CN)64– and oxalic acid were observed at 6.5 × 10−4 and 4.2 × 10−4 m/s, respectively, which are among the highest reported in the literature. Additionally, hydroxyl radical (•OH) formed at a rate of 4.72 × 10−9 mol/(cm2·min) upon 0.59 mA/cm2, much higher than that for Ti4O7 materials. For norfloxacin and sulfamethoxazole at trace level concentration in surface water and wastewater final effluent, a log removal only needs 2.0–5.4 s real residence time. The corresponding energy costs were estimated as 0.005–0.024 kWh/m3. This highly scalable β-PbO2-TRF technology presents a new and cost-effective option for one-step deep purification of wastewater effluent.